Erosion by an Alpine glacier.

PubMed

Herman, Frédéric; Beyssac, Olivier; Brughelli, Mattia; Lane, Stuart N; Leprince, Sébastien; Adatte, Thierry; Lin, Jiao Y Y; Avouac, Jean-Philippe; Cox, Simon C

2015-10-09

Assessing the impact of glaciation on Earth's surface requires understanding glacial erosion processes. Developing erosion theories is challenging because of the complex nature of the erosion processes and the difficulty of examining the ice/bedrock interface of contemporary glaciers. We demonstrate that the glacial erosion rate is proportional to the ice-sliding velocity squared, by quantifying spatial variations in ice-sliding velocity and the erosion rate of a fast-flowing Alpine glacier. The nonlinear behavior implies a high erosion sensitivity to small variations in topographic slope and precipitation. A nonlinear rate law suggests that abrasion may dominate over other erosion processes in fast-flowing glaciers. It may also explain the wide range of observed glacial erosion rates and, in part, the impact of glaciation on mountainous landscapes during the past few million years. Copyright © 2015, American Association for the Advancement of Science.

Sediment detachment and transport processes associated with internal erosion of soil pipes: Often overlooked processes of gully erosion

USDA-ARS?s Scientific Manuscript database

Subsurface flow can be an important process in gully erosion through its impact on decreasing soil cohesion and erosion resistance as soil water content or pressure increases and more directly by the effects of seepage forces on particle detachment and piping. The development of perched water tables...

Numerical study of impact erosion of multiple solid particle

NASA Astrophysics Data System (ADS)

Zheng, Chao; Liu, Yonghong; Chen, Cheng; Qin, Jie; Ji, Renjie; Cai, Baoping

2017-11-01

Material erosion caused by continuous particle impingement during hydraulic fracturing results in significant economic loss and increased production risks. The erosion process is complex and has not been clearly explained through physical experiments. To address this problem, a multiple particle model in a 3D configuration was proposed to investigate the dynamic erosion process. This approach can significantly reduce experiment costs. The numerical model considered material damping and elastic-plastic material behavior of target material. The effects of impact parameters on erosion characteristics, such as plastic deformation, contact time, and energy loss rate, were investigated. Based on comprehensive studies, the dynamic erosion mechanism and geometry evolution of eroded crater was obtained. These findings can provide a detailed erosion process of target material and insights into the material erosion caused by multiple particle impingement.

Electromagnetic valve for controlling the flow of molten, magnetic material

DOEpatents

Richter, T.

1998-06-16

An electromagnetic valve for controlling the flow of molten, magnetic material is provided, which comprises an induction coil for generating a magnetic field in response to an applied alternating electrical current, a housing, and a refractory composite nozzle. The nozzle is comprised of an inner sleeve composed of an erosion resistant refractory material (e.g., a zirconia ceramic) through which molten, magnetic metal flows, a refractory outer shell, and an intermediate compressible refractory material, e.g., unset, high alumina, thermosetting mortar. The compressible refractory material is sandwiched between the inner sleeve and outer shell, and absorbs differential expansion stresses that develop within the nozzle due to extreme thermal gradients. The sandwiched layer of compressible refractory material prevents destructive cracks from developing in the refractory outer shell. 5 figs.

Electromagnetic valve for controlling the flow of molten, magnetic material

DOEpatents

Richter, Tomas

1998-01-01

An electromagnetic valve for controlling the flow of molten, magnetic material is provided, which comprises an induction coil for generating a magnetic field in response to an applied alternating electrical current, a housing, and a refractory composite nozzle. The nozzle is comprised of an inner sleeve composed of an erosion resistant refractory material (e.g., a zirconia ceramic) through which molten, magnetic metal flows, a refractory outer shell, and an intermediate compressible refractory material, e.g., unset, high alumina, thermosetting mortar. The compressible refractory material is sandwiched between the inner sleeve and outer shell, and absorbs differential expansion stresses that develop within the nozzle due to extreme thermal gradients. The sandwiched layer of compressible refractory material prevents destructive cracks from developing in the refractory outer shell.

[Sediment-yielding process and its mechanisms of slope erosion in wind-water erosion crisscross region of Loess Plateau, Northwest China].

PubMed

Tuo, Deng-Feng; Xu, Ming-Xiang; Zheng, Shi-Qing; Li, Qiang

2012-12-01

Due to the coupling effects of wind and water erosions in the wind-water erosion crisscross region of Loess Plateau, the slope erosion in the region was quite serious, and the erosion process was quite complicated. By using wind tunnel combined with simulated rainfall, this paper studied the sediment-yielding process and its mechanisms of slope erosion under the effects of wind-water alternate erosion, and quantitatively analyzed the efffects of wind erosion on water erosion and the relationships between wind and water erosions. There was an obvious positive interaction between wind and water erosions. Wind erosion promoted the development of microtopography, and altered the quantitative relationship between the sediment-yielding under water erosion and the variation of rainfall intensity. At the rainfall intensity of 60 and 80 mm x h(-1), the sediment-yielding without wind erosion decreased with the duration of rainfall and tended to be stable, but the sediment-yielding with wind erosion decreased to a certain valley value first, and then showed an increasing trend. At the rainfall intensity of 60, 80, and 100 mm x h(-1), the sediment-yielding with the wind erosion at speeds of 11 and 14 m x s(-1) increased by 7.3%-27.9% and 23.2%-39.0%, respectively, as compared with the sediment-yielding without wind erosion. At the rainfall intensity of 120 and 150 mm x h(-1) and in the rainfall duration of 15 minutes, the sediment-yielding with and without wind erosion presented a decreasing trend, but, with the increase of rainfall duration, the sediment-yielding with wind erosion showed a trend of decreasing first and increasing then, as compared with the sediment-yielding without wind erosion. The mechanisms of wind-water alternate erosion were complicated, reflecting in the mutual relation and mutual promotion of wind erosion and water erosion in the aspects of temporal-spatial distribution, energy supply, and action mode of erosion forces.

Identification and characterization of natural pipe systems in forested tropical soils

NASA Astrophysics Data System (ADS)

Bovi, Renata Cristina; Moreira, Cesar Augusto; Stucchi Boschi, Raquel; Cooper, Miguel

2017-04-01

Erosive processes on soil surface have been well studied and comprehended by several researchers, however little is known about subsurface erosive processes (piping). Piping is a type of subsurface erosion caused by water flowing in the subsurface and is still considered one of the most difficult erosive processes to be studied. Several processes have been considered as resposible for subsurface erosion and their interaction is complex and difficult to be studied separately. Surface investigations on their own may underestimate the erosion processes, due to the possible occurrence of subsurface processes that are not yet exposed on the surface. The network of subsurface processes should also be understood to better control erosion. Conservation practices that focus on water runoff control may be inefficient if the subsurface flow is not considered. In this study, we aimed to identify and characterize subsurface cavities in the field, as well as understand the network of these cavities, by using geophysical methods (electrical tomography). The study area is situated at the Experimental Station of Tupi, state of São Paulo, Brazil. The soil of the area was classified as Hapludults. The area presents several erosive features, ranging from laminar to permanent gullies and subsurface erosions. The geophysical equipment used was the Terrameter LS resistivity meter, manufactured by ABEM Instruments. The method of electrical tomography was efficient to detect collapsed and non-collapsed pipes. The results presented valuable information to detect areas of risk.

Evaluating the effectiveness of agricultural mulches for reducing post-wildfire wind erosion

USDA-ARS?s Scientific Manuscript database

Post-wildfire soil erosion can be caused by water or aeolian processes yet most erosion research has focused on predominantly water-driven erosion. This study investigates the effectiveness of three agricultural mulches, with and without a tackifier, on aeolian sediment transport processes. A wind t...

Interrill soil erosion processes on steep slopes

USDA-ARS?s Scientific Manuscript database

To date interrill erosion processes and regimes are not fully understood. The objectives are to 1) identify the erosion regimes and limiting processes between detachment and transport on steep slopes, 2) characterize the interactive effects between rainfall intensity and flow depth on sediment trans...

How does slope form affect erosion in CATFLOW-SED?

NASA Astrophysics Data System (ADS)

Gabelmann, Petra; Wienhöfer, Jan; Zehe, Erwin

2016-04-01

Erosion is a severe environmental problem in agro-ecosystems with highly erodible loess soils. It is controlled by various factors, e.g. rainfall intensity, initial wetness conditions, soil type, land use and tillage practice. Furthermore slope form and gradient have been shown to influence erosion amounts to a large extent. Within the last fifty years, various erosion models have been developed to describe the erosion process, estimate erosion amounts and identify erosion-prone areas. These models differ in terms of complexity, the processes which are considered, and the data required for model calibration and they can be categorised into empirical or statistical, conceptual, and physically-based models. CATFLOW-SED is a process-based hydrology and erosion model that can operate on catchment and hillslope scales. Soil water dynamics are described by the Richards equation including effective approaches for preferential flow. Evapotranspiration is simulated using an approach based on the Penman-Monteith equation. The model simulates overland flow using the diffusion wave equation. Soil detachment is related to the attacking forces of rainfall and overland flow, and the erosion resistance of soil. Sediment transport capacity and sediment deposition are related to overland flow velocity using the equation of Engelund and Hansen and the sinking velocity of grain sizes respectively. We performed a study to analyse the erosion process on different virtual hillslopes, with varying slope gradient and slope form, using the CATFLOW-SED model. We explored the role of landform on erosion and sedimentation, particularly we look for forms that either maximise or minimise erosion. Results indicate the importance to performing the process implementation within physically meaningful limits and choose appropriate model parameters respectively.

Physical erosion modelling of complex morphodynamics in the upper Val d'Orcia: a combination of EROSION 3D, UAV, SFM and CANUPO

NASA Astrophysics Data System (ADS)

Buchholz, Arno; Kaiser, Andreas; Neugirg, Fabian; Schindewolf, Marcus; Schmidt, Jürgen

2017-04-01

Throughout the Mediterranean Basin soil erosion is both a widely spread and a landscape shaping process. In order to increase the understanding of morphodynamics inside large Italian badland areas, so called Calanchi, the process based erosion model EROSION 3D was parameterized by artificial rainfall simulations, soil sampling and an UAV based high resolution digital elevation model. Vegetation structures were removed with the CANUPO-classifier in CloudCompare. The rainfall experiments proved to be a convenient but costly tool for deriving the model input parameters. While building up the model, different composition of the inhomogeneous soil surface was considered. A diverse behavior against erosion by water was observed. The results showed that the deposition surfaces of rotational or translational slides, besides calanco depth contour, tend to degrade. Although these deposits present a comparatively low bulk density, they reduce the infiltration due to soil surface clogging and cause less erosion resistances. The differential consideration of erosion sub-processes turns out as particularly challenging. The simulation of a reference year showed an annual soil export from the catchment of 43 t/ha, which corresponds to an average surface lowering of 3 mm. Sheet erosion represents an amount of about 5% of the total erosion of badlands. Furthermore, infiltration depth, amount of runoff, sediment concentration, and grain size composition of the deposits were calculated. This study makes a contribution to the understanding of denudation processes in Calanchi badlands. The presented process-based modeling of badlands is contributing a new aspect to erosion research.

Gaining insights into interrill soil erosion processes using rare earth element tracers

USDA-ARS?s Scientific Manuscript database

Increasing interest in developing process-based erosion models requires better understanding of the relationships among soil detachment, transportation, and deposition. The objectives are to 1) identify the limiting process between soil detachment and sediment transport for interrill erosion, 2) und...

Can DEM time series produced by UAV be used to quantify diffuse erosion in an agricultural watershed?

NASA Astrophysics Data System (ADS)

Pineux, N.; Lisein, J.; Swerts, G.; Bielders, C. L.; Lejeune, P.; Colinet, G.; Degré, A.

2017-03-01

Erosion and deposition modelling should rely on field data. Currently these data are seldom available at large spatial scales and/or at high spatial resolution. In addition, conventional erosion monitoring approaches are labour intensive and costly. This calls for the development of new approaches for field erosion data acquisition. As a result of rapid technological developments and low cost, unmanned aerial vehicles (UAV) have recently become an attractive means of generating high resolution digital elevation models (DEMs). The use of UAV to observe and quantify gully erosion is now widely established. However, in some agro-pedological contexts, soil erosion results from multiple processes, including sheet and rill erosion, tillage erosion and erosion due to harvest of root crops. These diffuse erosion processes often represent a particular challenge because of the limited elevation changes they induce. In this study, we propose to assess the reliability and development perspectives of UAV to locate and quantify erosion and deposition in a context of an agricultural watershed with silt loam soils and a smooth relief. Erosion and deposition rates derived from high resolution DEM time series are compared to field measurements. The UAV technique demonstrates a high level of flexibility and can be used, for instance, after a major erosive event. It delivers a very high resolution DEM (pixel size: 6 cm) which allows us to compute high resolution runoff pathways. This could enable us to precisely locate runoff management practices such as fascines. Furthermore, the DEMs can be used diachronically to extract elevation differences before and after a strongly erosive rainfall and be validated by field measurements. While the analysis for this study was carried out over 2 years, we observed a tendency along the slope from erosion to deposition. Erosion and deposition patterns detected at the watershed scale are also promising. Nevertheless, further development in the processing workflow of UAV data is required in order to make this technique accurate and robust enough for detecting sediment movements in an agricultural watershed affected by diffuse erosion. This area of investigation holds much potential as the images processing is relatively new and expanding.

Issues of upscaling in space and time with soil erosion models

NASA Astrophysics Data System (ADS)

Brazier, R. E.; Parsons, A. J.; Wainwright, J.; Hutton, C.

2009-04-01

Soil erosion - the entrainment, transport and deposition of soil particles - is an important phenomenon to understand; the quantity of soil loss determines the long term on-site sustainability of agricultural production (Pimental et al., 1995), and has potentially important off-site impacts on water quality (Bilotta and Brazier, 2008). The fundamental mechanisms of the soil erosion process have been studied at the laboratory scale, plot scale (Wainwright et al., 2000), the small catchment scale (refs here) and river basin scale through sediment yield and budgeting work. Subsequently, soil erosion models have developed alongside and directly from this empirical work, from data-based models such as the USLE (Wischmeier and Smith, 1978), to ‘physics or process-based' models such as EUROSEM (Morgan et al., 1998) and WEPP (Nearing et al., 1989). Model development has helped to structure our understanding of the fundamental factors that control soil erosion process at the plot and field scale. Despite these advances, however, our understanding of and ability to predict erosion and sediment yield at the same plot, field and also larger catchment scales remains poor. Sediment yield has been shown to both increase and decrease as a function of drainage area (de Vente et al., 2006); the lack of a simple relationship demonstrates complex and scale-dependant process domination throughout a catchment, and emphasises our uncertainty and poor conceptual basis for predicting plot to catchment scale erosion rates and sediment yields (Parsons et al., 2006b). Therefore, this paper presents a review of the problems associated with modelling soil erosion across spatial and temporal scales and suggests some potential solutions to address these problems. The transport-distance approach to scaling erosion rates (Wainwright, et al., 2008) is assessed and discussed in light of alternative techniques to predict erosion across spatial and temporal scales. References Bilotta, G.S. and Brazier, R.E., 2008. Understanding the influence of suspended solids on water quality and aquatic biota. Water Research, 42(12): 2849-2861. de Vente, J., Poesen, J., Bazzoffi, P., Van Ropaey, A.V. and Verstraeten, G., 2006. Predicting catchment sediment yield in Mediterranean environments: the importance of sediment sources and connectivity in Italian drainage basins. Earth Surface Processes And Landforms, 31: 1017-1034. Morgan, R.P.C. et al., 1998. The European soil erosion model (EUROSEM): a dynamic approach for predicting sediment transport from fields to small catchments. Earth Surface Processes And Landforms, 23: 527-544. Nearing, M. A., G. R. Foster, L. J. Lane, and S. C. Finkner. 1989. A process-based soil erosion model for USDA Water Erosion Prediction Project technology. Trans. ASAE 32(5): 1587-1593. Parsons, A.J., Brazier, R.E., Wainwright, J. and Powell, D.M., 2006a. Scale relationships in hillslope runoff and erosion. Earth Surface Processes and Landforms, 31(11): 1384-1393. Parsons, A.J., Wainwright, J., Brazier, R.E. and Powell, D.M., 2006b. Is sediment delivery a fallacy? Earth Surface Processes and Landforms, 31(10): 1325-1328. Pimental, D. et al., 1995. Environmental and economic costs of soil erosion and conservation benefits. Science, 267:1117-1122. Wainwright, J., Parsons, A.J. and Abrahams, A.D., 2000. Plot-scale studies of vegetation, overland flow and erosion interactions: case studies from Arizona and New Mexico. Hydrological Processes, 14(16-17): 2921-2943. Wischmeier, W.H. and Smith, D.D., 1978. Predicting rainfall erosion losses - a guide for conservation planning., 537.

Research of wind erosion intensity in the region of Subotica-Horgos sands

Treesearch

Velizar Velasevic; Ljubomir Letic

1991-01-01

Wind is an important erosional process in the areas of steppe-savanna climate in Europe as typified by the Bojvodina plain in Yugoslavia. Cultivated and forested plots on the Subotica-Horgos Sands were used to study aeolian erosion processes. Wind erosion on the cultivated plot was 3-29 times greater than that occurring on a plot planted to forest trees. That erosion...

Evaluating a process-based model for use in streambank stabilization and stream restoration: insights on the bank stability and toe erosion model (BSTEM)

USDA-ARS?s Scientific Manuscript database

Streambank retreat is a complex cyclical process involving subaerial processes, fluvial erosion, seepage erosion, and geotechnical failures and is driven by several soil properties that themselves are temporally and spatially variable. Therefore, it can be extremely challenging to predict and model ...

Process-oriented modelling to identify main drivers of erosion-induced carbon fluxes

NASA Astrophysics Data System (ADS)

Wilken, Florian; Sommer, Michael; Van Oost, Kristof; Bens, Oliver; Fiener, Peter

2017-05-01

Coupled modelling of soil erosion, carbon redistribution, and turnover has received great attention over the last decades due to large uncertainties regarding erosion-induced carbon fluxes. For a process-oriented representation of event dynamics, coupled soil-carbon erosion models have been developed. However, there are currently few models that represent tillage erosion, preferential water erosion, and transport of different carbon fractions (e.g. mineral bound carbon, carbon encapsulated by soil aggregates). We couple a process-oriented multi-class sediment transport model with a carbon turnover model (MCST-C) to identify relevant redistribution processes for carbon dynamics. The model is applied for two arable catchments (3.7 and 7.8 ha) located in the Tertiary Hills about 40 km north of Munich, Germany. Our findings indicate the following: (i) redistribution by tillage has a large effect on erosion-induced vertical carbon fluxes and has a large carbon sequestration potential; (ii) water erosion has a minor effect on vertical fluxes, but episodic soil organic carbon (SOC) delivery controls the long-term erosion-induced carbon balance; (iii) delivered sediments are highly enriched in SOC compared to the parent soil, and sediment delivery is driven by event size and catchment connectivity; and (iv) soil aggregation enhances SOC deposition due to the transformation of highly mobile carbon-rich fine primary particles into rather immobile soil aggregates.

Mapping soil erosion risk in Serra de Grândola (Portugal)

NASA Astrophysics Data System (ADS)

Neto Paixão, H. M.; Granja Martins, F. M.; Zavala, L. M.; Jordán, A.; Bellinfante, N.

2012-04-01

Geomorphological processes can pose environmental risks to people and economical activities. Information and a better knowledge of the genesis of these processes is important for environmental planning, since it allows to model, quantify and classify risks, what can mitigate the threats. The objective of this research is to assess the soil erosion risk in Serra de Grândola, which is a north-south oriented mountain ridge with an altitude of 383 m, located in southwest of Alentejo (southern Portugal). The study area is 675 km2, including the councils of Grândola, Santiago do Cacém and Sines. The process for mapping of erosive status was based on the guidelines for measuring and mapping the processes of erosion of coastal areas of the Mediterranean proposed by PAP/RAC (1997), developed and later modified by other authors in different areas. This method is based on the application of a geographic information system that integrates different types of spatial information inserted into a digital terrain model and in their derivative models. Erosive status are classified using information from soil erodibility, slope, land use and vegetation cover. The rainfall erosivity map was obtained using the modified Fournier index, calculated from the mean monthly rainfall, as recorded in 30 meteorological stations with influence in the study area. Finally, the soil erosion risk map was designed by ovelaying the erosive status map and the rainfall erosivity map.

Wind erosion processes and control

USDA-ARS?s Scientific Manuscript database

Wind erosion continues to threaten the sustainability of our nations' soil, air, and water resources. To effectively apply conservation systems to prevent wind driven soil loss, an understanding of the fundamental processes of wind erosion is necessary so that land managers can better recognize the ...

Evaluation of soil erosion risk using Analytic Network Process and GIS: a case study from Spanish mountain olive plantations.

PubMed

Nekhay, Olexandr; Arriaza, Manuel; Boerboom, Luc

2009-07-01

The study presents an approach that combined objective information such as sampling or experimental data with subjective information such as expert opinions. This combined approach was based on the Analytic Network Process method. It was applied to evaluate soil erosion risk and overcomes one of the drawbacks of USLE/RUSLE soil erosion models, namely that they do not consider interactions among soil erosion factors. Another advantage of this method is that it can be used if there are insufficient experimental data. The lack of experimental data can be compensated for through the use of expert evaluations. As an example of the proposed approach, the risk of soil erosion was evaluated in olive groves in Southern Spain, showing the potential of the ANP method for modelling a complex physical process like soil erosion.

Soil erodibility for water erosion: A perspective and Chinese experiences

NASA Astrophysics Data System (ADS)

Wang, Bin; Zheng, Fenli; Römkens, Mathias J. M.; Darboux, Frédéric

2013-04-01

Knowledge of soil erodibility is an essential requirement for erosion prediction, conservation planning, and the assessment of sediment related environmental effects of watershed agricultural practices. This paper reviews the status of soil erodibility evaluations and determinations based on 80 years of upland area erosion research mainly in China and the USA. The review synthesizes the general research progress made by discussing the basic concepts of erodibility and its evaluation, determination, and prediction as well as knowledge of its spatio-temporal variations. The authors found that soil erodibility is often inappropriately or inaccurately applied in describing soil loss caused by different soil erosion component processes and mechanisms. Soil erodibility indicators were related to intrinsic soil properties and exogenic erosional forces, measurements, and calculations. The present review describes major needs including: (1) improved definition of erodibility, (2) modified erodibility determinations in erosion models, especially for specific geographical locations and in the context of different erosion sub-processes, (3) advanced methodologies for quantifying erodibilities of different soil erosion sub-processes, and (4) a better understanding of the mechanism that causes temporal variations in soil erodibility. The review also provides a more rational basis for future research on soil erodibility and supports predictive modeling of soil erosion processes and the development of improved conservation practices.

Parameterization of erodibility in the Rangeland Hydrology and Erosion Model

USDA-ARS?s Scientific Manuscript database

The magnitude of erosion from a hillslope is governed by the availability of sediment and connectivity of runoff and erosion processes. For undisturbed rangelands, sediment is primarily detached and transported by rainsplash and sheetflow (splash-sheet) processes in isolated bare batches, but sedime...

A simple enrichment correction factor for improving erosion estimation by rare earth oxide tracers

USDA-ARS?s Scientific Manuscript database

Spatially distributed soil erosion data are needed to better understanding soil erosion processes and validating distributed erosion models. Rare earth element (REE) oxides were used to generate spatial erosion data. However, a general concern on the accuracy of the technique arose due to selective ...

Annotated bibliography on soil erosion and erosion control in subarctic and high-latitude regions of North America.

Treesearch

C.W. Slaughter; J.W. Aldrich

1989-01-01

This annotated bibliography emphasizes the physical processes of upland soil erosion, prediction of soil erosion and sediment yield, and erosion control. The bibliography is divided into two sections: (1) references specific to Alaska, the Arctic and subarctic, and similar high-latitude settings; and (2) references relevant to understanding erosion, sediment production...

Dynamic Modelling of Erosion and Deposition Processes in Debris Flows With Application to Real Debris Flow Events in Switzerland

NASA Astrophysics Data System (ADS)

Deubelbeiss, Y.; McArdell, B. W.; Graf, C.

2011-12-01

The dynamics of a debris flow can be significantly influenced by erosion and deposition processes during an event because volume changes have a strong influence on flow properties such as flow velocity, flow heights and runout distances. It is therefore worth exploring how to include these processes in numerical models, which are used for hazard assessment and mitigation measure planning. However, it is still under debate, what mechanism drives the erosion of material at the base of a debris flow. There are different processes attributed to erosion: it has been proposed that erosion correlates with the stresses due to granular interactions at the front, which in turn strongly depend on particle size or it may be related to basal shear forces. Because it is expected that larger flow heights result in larger stresses one can additionally hypothesize that there is a correlation between erosion rate and flow height. To test different erosion laws in a numerical model and its influence on the flow behavior we implement different relationships and compare simulation results with field data. Herefore, we use the numerical model, RAMMS (Christen et al., 2010), employing the Voellmy-fluid friction law. While it has already been shown that a correlation of erosion with velocity does not lead to a satisfying result (too high entrainment in the tail) a correlation with flow height combined with velocity (momentum) has been successfully applied to ice-avalanches. Currently, we are testing the momentum-driven and for comparison we reconsider the simple velocity-driven erosion rate. However, these laws do not consider processes on a smaller scale such as particle fluctuations resulting in energy production, which might play an important role. Therefore, we additionally consider an erosion model that has potential to draw new insights on the erosion process in debris flows. The model is based on an extended Voellmy model, which additionally employs an equation, which is a measure of the random kinetic energy (RKE, equivalent to granular temperature) produced by the random movement of particles in a debris flow (Buser and Bartelt, 2009). Advantageous is that friction is dependent on the production of RKE and is decreasing with decreasing RKE. The amount of energy produced in the system, might therefore be a useful indicator for the erosion rate. While the erosion model using the Voellmy approach might be successfully applicable to cases where erosion and bulking are the main processes, such as in Illgraben (CH), it might be less straight forward in mountain torrents where we additionally observe a lot of deposition along the flow path such as in Dorfbach (CH). The extended Voellmy model is indirectly accounting for this process as friction is a function of RKE, which allows material to deposit earlier. At both locations we have debris flow observation stations including innovative new measurement techniques indication parameters such as flow velocity, height and volumes at specific locations (Illgraben, Dorfbach) as well as erosion rate measurements (Illgraben). These highly valuable data allow us good model calibration as well as verification of the newly implemented erosion models.

Geomorphic considerations for erosion prediction

USGS Publications Warehouse

Osterkamp, W.R.; Toy, T.J.

1997-01-01

Current soil-erosion prediction technology addresses processes of rainsplash, overland-flow sediment transport, and rill erosion in small watersheds. The effects of factors determining sediment yield from larger-scale drainage basins, in which sediment movement is controlled by the combined small-scale processes and a complex set of channel and other basin-scale sediment-delivery processes, such as soil creep, bioturbation, and accelerated erosion due to denudation of vegetation, have been poorly evaluated. General suggestions are provided for the development of erosion-prediction technology at the geomorphic or drainage-basin scale based on the separation of sediment-yield data for channel and geomorphic processes from those of field-scale soil loss. An emerging technology must consider: (1) the effects on sediment yield of climate, geology and soils, topography, biotic interactions with other soil processes, and land-use practices; (2) all processes of sediment delivery to a channel system; and (3) the general tendency in most drainage basins for progressively greater sediment storage in the downstream direction.

Advances in modeling soil erosion after disturbance on rangelands

USDA-ARS?s Scientific Manuscript database

Research has been undertaken to develop process based models that predict soil erosion rate after disturbance on rangelands. In these models soil detachment is predicted as a combination of multiple erosion processes, rain splash and thin sheet flow (splash and sheet) detachment and concentrated flo...

Effects of soil surface roughness on interrill erosion processes and sediment particle size distribution

USDA-ARS?s Scientific Manuscript database

Soil surface roughness significantly impacts runoff and erosion under rainfall. Few previous studies on runoff generation focused on the effects of soil surface roughness on the sediment particle size distribution (PSD), which greatly affects interrill erosion and sedimentation processes. To address...

Experimental rill erosion research vs. model concepts - quantification of the hydraulic and erosional efficiency of rills

NASA Astrophysics Data System (ADS)

Wirtz, Stefan

2014-05-01

In soil erosion research, rills are believed to be one of the most efficient forms. They act as preferential flow paths for overland flow and hence become the most efficient sediment sources in a catchment. However their fraction of the overall detachment in a certain area compared to other soil erosion processes is contentious. The requirement for handling this subject is the standardization of the used measurement methods for rill erosion quantification. Only by using a standardized method, the results of different studies become comparable and can be synthesized to one overall statement. In rill erosion research, such a standardized field method was missing until now. Hence, the first aim of this study is to present an experimental setup that enables us to obtain comparable data about process dynamics in eroding rills under standardized conditions in the field. Using this rill experiment, the runoff efficiency of rills (second aim) and the fraction of rill erosion on total soil loss (third aim) in a catchment are quantified. The erosion rate [g m-2] in the rills is between twenty- and sixty-times higher compared to the interrill areas, the specific discharge [L s-1 m-2] in the rills is about 2000 times higher. The identification and quantification of different rill erosion processes are the fourth aim within this project. Gravitative processes like side wall failure, headcut- and knickpoint retreat provide up to 94 % of the detached sediment quantity. In soil erosion models, only the incision into the rill's bottom is considered, hence the modelled results are unsatisfactorily. Due to the low quality of soil erosion model results, the fifth aim of the study is to review two physical basic assumptions using the rill experiments. Contrasting with the model assumptions, there is no clear linear correlation between any hydraulic parameter and the detachment rate and the transport rate is capable of exceeding the transport capacity. In conclusion, the results clearly show the need of experimental field data obtained under conditions as close as possible to reality. This is the only way to improve the fundamental knowledge about the function and the impact of the different processes in rill erosion. A better understanding of the process combinations is a fundamental request for developing a really functioning soil erosion model. In such a model, spatial and temporal variability as well as the combination of different sub-processes must be considered. Regarding the experimental results of this study, the simulation of natural processes using simple, static mathematical equations seems not to be possible.

Lava channel formation during the 2001 eruption on Mount Etna: evidence for mechanical erosion.

PubMed

Ferlito, Carmelo; Siewert, Jens

2006-01-20

We report the direct observation of a peculiar lava channel that was formed near the base of a parasitic cone during the 2001 eruption on Mount Etna. Erosive processes by flowing lava are commonly attributed to thermal erosion. However, field evidence strongly suggests that models of thermal erosion cannot explain the formation of this channel. Here, we put forward the idea that the essential erosion mechanism was abrasive wear. By applying a simple model from tribology we demonstrate that the available data agree favorably with our hypothesis. Consequently, we propose that erosional processes resembling the wear phenomena in glacial erosion are possible in a volcanic environment.

Control and monitoring method and system for electromagnetic forming process

DOEpatents

Kunerth, Dennis C.; Lassahn, Gordon D.

1990-01-01

A process, system, and improvement for a process for electromagnetic forming of a workpiece in which characteristics of the workpiece such as its geometry, electrical conductivity, quality, and magnetic permeability can be determined by monitoring the current and voltage in the workcoil. In an electromagnet forming process in which a power supply provides current to a workcoil and the electromagnetic field produced by the workcoil acts to form the workpiece, the dynamic interaction of the electromagnetic fields produced by the workcoil with the geometry, electrical conductivity, and magnetic permeability of the workpiece, provides information pertinent to the physical condition of the workpiece that is available for determination of quality and process control. This information can be obtained by deriving in real time the first several time derivatives of the current and voltage in the workcoil. In addition, the process can be extended by injecting test signals into the workcoil during the electromagnetic forming and monitoring the response to the test signals in the workcoil.

Effects of Laser Shock Processing on Morphologies and Mechanical Properties of ANSI 304 Stainless Steel Weldments Subjected to Cavitation Erosion

PubMed Central

Zhang, Lei; Lu, Jin-Zhong; Zhang, Yong-Kang; Ma, Hai-Le; Luo, Kai-Yu; Dai, Feng-Ze

2017-01-01

Effects of laser shock processing (LSP) on the cavitation erosion resistance of laser weldments were investigated by optical microscope (OM), scanning electron microscope (SEM) observations, roughness tester, micro hardness tester, and X-ray diffraction (XRD) technology. The morphological microstructures were characterized. Cumulative mass loss, incubation period, erosion rate, and damaged surface areas were monitored during cavitation erosion. Surface roughness, micro-hardness, and residual stress were measured in different zones. Results showed that LSP could improve the damage of morphological microstructures and mechanical properties after cavitation erosion. The compressive residual stresses were generated during the process of LSP, which was an effective guarantee for the improvement of the above mentioned properties. PMID:28772652

Elevated Temperature Solid Particle Erosion Performance of Plasma-Sprayed Co-based Composite Coatings with Additions of Al2O3 and CeO2

NASA Astrophysics Data System (ADS)

Nithin, H. S.; Desai, Vijay; Ramesh, M. R.

2017-11-01

In this paper, investigation into solid particle erosion behavior of atmospheric plasma-sprayed composite coating of CoCrAlY reinforced with Al2O3 and CeO2 oxides on Superni 76 at elevated temperature of 600 °C is presented. Alumina particles are used as erodent at two impact angles of 30° and 90°. The microstructure, porosity, hardness, toughness and adhesion properties of the as-sprayed coatings are studied. The effects of temperature and phase transformation in the coatings during erosion process are analyzed using XRD and EDS techniques. Optical profilometer is used for accurate elucidation of erosion volume loss. CoCrAlY/CeO2 coating showed better erosion resistance with a volume loss of about 50% of what was observed in case of CoCrAlY/Al2O3/YSZ coating. Lower erosion loss is observed at 90° as compared to 30° impact angle. The erosion mechanism evaluated using SEM micrograph revealed that the coatings experienced ductile fracture exhibiting severe deformation with unusual oxide cracks. Reinforced metal oxides provide shielding effect for erodent impact, enabling better erosion resistance. The oxidation of the coating due to high-temperature exposure reforms erosion process into oxidation-modified erosion process.

Disc valve for sampling erosive process streams

DOEpatents

Mrochek, J.E.; Dinsmore, S.R.; Chandler, E.W.

1984-08-16

This is a patent for a disc-type, four-port sampling valve for service with erosive high temperature process streams. Inserts and liners of ..cap alpha..-silicon carbide respectively, in the faceplates and in the sampling cavities, limit erosion while providing lubricity for a smooth and precise operation. 1 fig.

Experimental investigation into the initiation and intensity of erosion in granular flows and its effect on flow dynamics with applications to pyroclastic density currents

NASA Astrophysics Data System (ADS)

Pollock, N. M.; Brand, B. D.; Roche, O.

2017-12-01

The macroscopic processes that control the behavior of pyroclastic density currents (PDCs) include the transportation and deposition of flow particles, entrainment of air, and interaction with topography. However, recent field studies demonstrate that substrate erosion by PDCs is also pervasive. Furthermore, analogue experiments suggest that erosion can increase flow runout distance up to 50%. We present the results from a series of analogue flume experiments on both non-fluidized and initially gas fluidized (i.e. high pore fluid pressure) granular flows. The experiments are designed to explore the controls on erosion initiation and intensity, and how erosion affects flow dynamics. A range of initial conditions allow us to explore how the angle of the bed (0°-20°) and diameter of substrate particles (40 to 700 μm) affect the onset of erosion. The experiments also explore how erosion, once initiated, affects the behavior of the flow in terms of velocity and runout distance. We observe that fluidized flows have increased runout distances of 50-300% relative to non-fluidized flows with the same initial conditions. Fluidized flows that travel over substrates composed of 40 μm particles consistently experience the largest increase in runout distance relative to non-fluidized flows, while flows over substrates of 80 μm particles experience the lowest increase. Erosion occurs for all experimental configurations in both non-fluidized and fluidized flows; however, the intensity of erosion varies widely, from small, millimeter-scale erosional features to decimeter sized wave-like features. Fluidized flows consistently show more intense erosion than non-fluidized flows, suggesting that the fluid-like behavior of these flows allows for efficient mixing between flow and substrate particles. These experiments demonstrate that erosion is a pervasive process for fluidized granular flows and that intense erosion is associated with increased flow runout distances. These results improve our understanding of the role of fluidization in erosion processes, what controls when PDCs become erosional, and how that erosion can alter flow behavior. To accurately model and predict hazards associated with PDCs, we must better understand erosional processes as they relate to these dangerous volcanic phenomena.

Erosion performance studies on sansevieria cylindrica reinforced vinylester composite

NASA Astrophysics Data System (ADS)

Johnson, R. Deepak Joel; Arumugaprabu, V.; Uthayakumar, M.; Vigneshwaran, S.; Manikandan, V.; Bennet, C.

2018-03-01

The intent of the research is to study the erosion behaviour of NaOH treated and untreated sansevieria cylindrica reinforced vinyl ester composites (SCVEC). The SCVEC was fabricated by varying fiber length as 30 mm and 40 mm and the fiber concentration as 30 wt%, 40 wt% and 50 wt% respectively for both NaOH treated and untreated sansevieria cylindrica fibres. The fabricated SCVEC was subjected to erosion studies using abrasive air jet erosion test rig. Full factorial design of experiment for conducting the erosion studies was made using Taguchi technique. The erosion test process variables like impingement angle 30°, 60° and 90°, impact velocity 28, 41 and 72 m s‑1, erodent feed rate or discharge 2.5, 3.3 and 4 g min‑1 and exposure time 5, 10 and 15 min were used to study the erosion rate of the SCVEC specimen. From the Taguchi analysis the optimized erosion process parameter and fabrication process parameters were found to be as fiber length 30 mm, NaOH treated fiber, fiber content 40 wt.%, impingement angle 90°, impact velocity 41 m s‑1, erodent discharge 4 g min‑1 and exposure time 15 min. Further, the erosion mechanism on the surface of the eroded SCVEC specimen was studied using Scanning electron microscope (SEM).

Ultrasonic cavitation erosion-corrosion behavior of friction stir processed stainless steel.

PubMed

Selvam, Karthikeyan; Mandal, Priya; Grewal, Harpreet Singh; Arora, Harpreet Singh

2018-06-01

Cavitation erosion remains the primary cause of material degradation in fluid machinery components operating at high speed. Micro-jets/shock waves caused by implosion of bubbles on material surface results in significant material loss and premature failure of the components. The presence of corrosive medium further exuberates this effect, causing rapid degradation. Here, we demonstrate a novel pathway to control cavitation erosion-corrosion by tailoring the surface properties using submerged friction stir processing (FSP), a severe plastic deformation process. FSP parameters were varied over wide range of strain-rates to generate tailored microstructures. High strain-rate processing resulted in nearly single phase fine grained structure while low strain-rate processing resulted in phase transformation in addition to grain refinement. As-received and processed samples were subjected to ultrasonic cavitation in distilled water as well as in corrosive environment of 3.5% NaCl solution. Individual roles of cavitation erosion, corrosion and their synergistic effects were analyzed. Depending on the microstructure, processed samples showed nearly 4-6 times higher cavitation erosion resistance compared to as-received alloy. Superior cavitation erosion-corrosion resistance of processed samples was attributed to surface strengthening, higher strain-hardening ability and quick passivation kinetics. The results of current study could be potentially transformative in designing robust materials for hydro-dynamic applications. Copyright © 2018 Elsevier B.V. All rights reserved.

Skylab

NASA Image and Video Library

1970-01-01

This 1970 photograph shows Skylab's Microwave Radiometer/Scatterometer and Altimeter, one of the major components for an Earth Resources Experiment Package (EREP). It was designed to study varying ocean surface, soil erosion, sea and lake ice, snow cover, seasonal vegetational changes, flooding, rainfall and soil types. The overall purpose of the EREP was to test the use of sensors that operated in the visible, infrared, and microwave portions of the electromagnetic spectrum to monitor and study Earth resources. The Marshall Space Flight Center had program management responsibility for the development of Skylab hardware and experiments.

The similarity of river evolution at the initial stage of channel erosion

NASA Astrophysics Data System (ADS)

Lin, Jiun-Chuan

2014-05-01

The study deals with a comparison study of two types of rocks at the initial stage of channel erosion in Taiwan. It is interesting that channel erosion at different types of rocks shows some similarity. There are two types of rocks: sandstone at Ta-an River, central Taiwan where river channel erosion from the nick point because of earthquake uplifting and mud rock at Tainan, southern Taiwan where rill erosion on a flat surface after artificial engineering. These two situations are both at the beginning stage of channel erosion, there are some similar landform appeared on channels. However the rate of erosion and magnitude of erosion are different. According to the using of photogrammetry method to reconstruct archive imageries and field surveying by total station and 3D scanner at different stages. The incision rate is high both at the Ta-an River and the bank erosion and it is even more obvious at mud rock area because of erodibility of mud rock. The results show that bank erosion and incision both are obvious processes. Bank erosion made channel into meander. The bank erosion cause slope in a asymmetric channel profile. The incision process will start at the site where land is relatively uplifted. This paper demonstrates such similarity and landform characters.

Electromagnetic Spectrum Test and Evaluation Process

DTIC Science & Technology

2010-01-01

HERO , hazards of electromagnetic radiation to ordnance ; HERP, hazards of electromagnetic radiation to personnel; HERF, hazards of electromagnetic ... electromagnetic pulse (EMP); electronic protection; electrostatic dis- charge (ESD); hazards of electromagnetic radi- ation to personnel (HERP), ordnance ...including ordnance containing electrically initiated devices, to be mutually compatible in their intended

Terrace effects on soil erosion processes in a watershed of the loess plateau

USDA-ARS?s Scientific Manuscript database

Terraces in crop fields are one of the most important soil and water conservation measures that affect runoff and erosion processes in a watershed. In this paper, terrace effects on soil erosion and sediment transport in the upstream and middle sections of the Weihe River basin in the Loess Plateau ...

Watershed rehabilitation: a process view

Treesearch

Robert R. Ziemer

1981-01-01

Abstract - The most effective control of erosion, in both physical and economic terms, is through prevention because once natural erosion is accelerated, corrective action is not only expensive but seldom entirely successful. To control erosion it is important to understand the forces that cause material to move or resist movement. Once the forces and processes of...

"Keynote address, Theme 4, Management of steepland erosion: an overview"

Treesearch

Robert R. Ziemer

1981-01-01

Abstract - Steepland erosion is a composite of surface, channel, and mass erosion. The relative importance of each process is determined by an interaction between climate, soil, geology, topography, and vegetation. A change in any of these components can increase or decrease the rate of erosion. The key to successful management of erosion is the ability to 1)...

Wind erosion of soils burned by wildfire

Treesearch

N. S. Wagenbrenner; M. J. Germino; B. K. Lamb; R. B. Foltz; P. R. Robichaud

2011-01-01

Wind erosion and aeolian transport processes are largely unstudied in the post-wildfire environment, but recent studies have shown that wind erosion can play a major role in burned landscapes. A wind erosion monitoring system was installed immediately following a wildfire in southeastern Idaho, USA to measure wind erosion from the burned area (Figure 1). This paper...

Modeling the Contribution of Ephemeral Gully Erosion Under Different Soil Management in An Olive Orchard Microcatchment Using AnnAGNPS Model

EPA Science Inventory

In Spain, few studies have been carried out to explore the erosion caused by processes other than interrill and rill erosion, such as gully and ephemeral gully erosion, especially because most of the available studies have evaluated the erosion at plot scale. A study about the en...

The similarity of river evolution at the initial stage of channel erosion

NASA Astrophysics Data System (ADS)

Lin, J.

2011-12-01

The similarity of river evolution at the initial stage of channel erosion Jiun-Chuan Lin Department of Geography, National Taiwan University Abstract The study deals with a comparison study of two types of rocks at the initial stage of channel erosion in Taiwan. It is interesting that channel erosion at different types of rocks shows some similarity. There are two types of rocks: sandstone at Ta-an River, central Taiwan where river channel erosion from the nick point because of earthquake uplifting and mud rock at Tainan, southern Taiwan where rill erosion on a flat surface after artificial engineering. These two situations are both at the beginning stage of channel erosion, there are some similar landform appeared on channels. However the rate of erosion and magnitude of erosion are different. According to the using of photogrammetry method to reconstruct archive imageries and field surveying by total station and 3D scanner at different stages. The incision rate is high both at the Ta-an River and the bank erosion and it is even more obvious at mud rock area because of erodibility of mud rock. The results show that bank erosion and incision both are obvious processes. Bank erosion made channel into meander. The bank erosion cause slope in a asymmetric channel profile. The incision process will start at the site where land is relatively uplifted. This paper demonstrates such similarity and landform characters.

Computational analysis of Pelton bucket tip erosion using digital image processing

NASA Astrophysics Data System (ADS)

Shrestha, Bim Prasad; Gautam, Bijaya; Bajracharya, Tri Ratna

2008-03-01

Erosion of hydro turbine components through sand laden river is one of the biggest problems in Himalayas. Even with sediment trapping systems, complete removal of fine sediment from water is impossible and uneconomical; hence most of the turbine components in Himalayan Rivers are exposed to sand laden water and subject to erode. Pelton bucket which are being wildly used in different hydropower generation plant undergoes erosion on the continuous presence of sand particles in water. The subsequent erosion causes increase in splitter thickness, which is supposed to be theoretically zero. This increase in splitter thickness gives rise to back hitting of water followed by decrease in turbine efficiency. This paper describes the process of measurement of sharp edges like bucket tip using digital image processing. Image of each bucket is captured and allowed to run for 72 hours; sand concentration in water hitting the bucket is closely controlled and monitored. Later, the image of the test bucket is taken in the same condition. The process is repeated for 10 times. In this paper digital image processing which encompasses processes that performs image enhancement in both spatial and frequency domain. In addition, the processes that extract attributes from images, up to and including the measurement of splitter's tip. Processing of image has been done in MATLAB 6.5 platform. The result shows that quantitative measurement of edge erosion of sharp edges could accurately be detected and the erosion profile could be generated using image processing technique.

Anthropogenic control on geomorphic process rates: can we slow down the erosion rates? (Geomorphology Outstanding Young Scientist Award & Penck Lecture)

NASA Astrophysics Data System (ADS)

Vanacker, V.

2012-04-01

The surface of the Earth is changing rapidly, largely in response to anthropogenic perturbation. Direct anthropogenic disturbance of natural environments may be much larger in many places than the (projected) indirect effects of climate change. There is now large evidence that humans have significantly altered geomorphic process rates, mainly through changes in vegetation composition, density and cover. While much attention has been given to the impact of vegetation degradation on geomorphic process rates, I suggest that the pathway of restoration is equally important to investigate. First, vegetation recovery after crop abandonment has a rapid and drastic impact on geomorphic process rates. Our data from degraded catchments in the tropical Andes show that erosion rates can be reduced by up to 100 times when increasing the protective vegetation cover. During vegetation restoration, the combined effects of the reduction in surface runoff, sediment production and hydrological connectivity are stronger than the individual effects together. Therefore, changes in erosion and sedimentation during restoration are not simply the reverse of those observed during degradation. Second, anthropogenic perturbation causes a profound but often temporary change in geomorphic process rates. Reconstruction of soil erosion rates in Spain shows us that modern erosion rates in well-vegetated areas are similar to long-term rates, despite evidence of strong pulses in historical erosion rates after vegetation clearance and agriculture. The soil vegetation system might be resilient to short pulses of accelerated erosion (and deposition), as there might exist a dynamic coupling between soil erosion and production also in degraded environments.

Relationships between slope erosion processes and aggregate stability of Ultisols from subtropical China during rainstorms

NASA Astrophysics Data System (ADS)

Liu, Gang; Xiao, Hai; Liu, Puling

2017-04-01

Soil aggregates, being a key soil structural unit, influence several soil physical properties such as water infiltration, runoff and erosion. The relationship between soil aggregate stability and interrill and rill erodibility is unclear but critical to process-based erosion prediction models. One obvious reason is that it is hard to distinguish between interrill and rill-eroded sediment during the erosion process. This study was designed to partition interrill and rill erosion rates and relates them to the aggregate stability of Ultisols in subtropical China. Six kinds of rare earth element (REE) were applied as tracers mixed with two cultivated soils derived from the Quaternary red clay soil and the shale soil at six slope positions. Soil aggregate stability was determined by the Le Bissonnais (LB)-method. Simulated rainfall with three intensities (60, 90 and 120 mm/h) were applied to a soil plot (2.25 m long, 0.5 m wide, 0.2 m deep) at three slope gradients (10°, 20° and 30°) with duration of 30 min after runoff initiation. The results indicated that interrill and rill erosion increased with increasing rainfall intensity and slope gradient for both types of soil. Rill and interrill erosion rates of the shale soil were much higher than those of the Quaternary red clay soil. Rill erosion contribution enhanced with increasing rainfall intensity and slope gradient for both soils. Percentage of the downslope area erosion to total erosion was the largest, followed by the mid-slope area and then upslope area. Equations using an aggregate stability index As to replace the erodibility factor of interrill and rill erosion in the Water Erosion Prediction Project (WEPP) model were constructed after analyzing the relationships between estimated and measured rill and interrill erosion data. It was shown that these equations based on the stability index, As, have the potential to improve methods for assessing interrill and rill erosion erodibility synchronously for the subtropical Ultisols by using REE tracing method.

Comparison of single thickness and double thickness processed pericardium patch graft in glaucoma drainage device surgery: a single surgeon comparison of outcome.

PubMed

Lankaranian, Dara; Reis, Ricardo; Henderer, Jeffrey D; Choe, Sung; Moster, Marlene R

2008-01-01

To compare the incidence of conjuctival erosions with single thickness versus double thickness allograft processed pericardium used in mitomycin-C (MMC) augmented glaucoma drainage device (GDD) sugery. In a retrospective comparative case series, medical records of 84 consecutive glaucoma patients who underwent GDD surgery between July 1996 to December 2004 were reviewed. All surgeries were done by one glaucoma surgeon (M.R.M.). MMC was adminstered in all cases over the plate area and either single thickness processed pericardium patch graft (STPP) or double thickness processed pericardium patch graft (DTPP) was used to cover the external silicone tube of the glaucoma device at the limbus. The principal outcome measure was the incidence of conjunctival erosions associated with GDD surgery. Eighty-four patients (90 eyes) who met the eligibility criteria were enrolled in the study. Thirty-one consecutive eyes received a STPP, and 59 consecutive eyes received a DTPP. Five eyes (16.0%) in the STPP group developed conjunctival erosion. None of the eyes in DTPP group developed conjunctival erosion. The Mann-Whitney U test difference in the rate of conjunctival erosion was statistically significant between 2 groups (P=0.002). For the STPP group, the average time to conjunctival erosion was 9 months (range, 4 to 14 mo). All erosions were surgically corrected using DTPP and followed up for a mean of 8.6 months after repair with no additional conjunctival erosions. DTPP placed over the silicone tube significantly reduced the incidence of conjunctival erosion after MMC augmented GDD surgery.

Understanding soil erosion impacts in temperate agroecosystems: bridging the gap between geomorphology and soil ecology using nematodes as a model organism

NASA Astrophysics Data System (ADS)

Baxter, C.; Rowan, J. S.; McKenzie, B. M.; Neilson, R.

2013-11-01

Soil is a key asset of natural capital, providing a myriad of goods and ecosystem services that sustain life through regulating, supporting and provisioning roles, delivered by chemical, physical and biological processes. One of the greatest threats to soil is accelerated erosion, which raises a natural process to unsustainable levels, and has downstream consequences (e.g.~economic, environmental and social). Global intensification of agroecosystems is a recognised major cause of soil erosion which, in light of predicted population growth and increased demand for food security, will continue or increase. Transport and redistribution of biota by soil erosion has hitherto been ignored and thus is poorly understood. With the move to sustainable intensification this is a key knowledge gap that needs to be addressed. Here we highlight the erosion-energy and effective-erosion-depth continuum in soils, differentiating between different forms of soil erosion, and argue that nematodes are an appropriate model taxa to investigate impacts of erosion on soil biota across scales. We review the different known mechanisms of soil erosion that impact on soil biota in general, and nematodes in particular, and highlight the few detailed studies, primarily from tropical regions, that have considered soil biota. Based on the limited literature and using nematodes as a model organism we outline future research priorities to initially address the important interrelationships between soil erosion processes and soil biota.

Quantifying Electromagnetic Wave Propagation Environment Using Measurements From A Small Buoy

DTIC Science & Technology

2017-06-01

ELECTROMAGNETIC WAVE PROPAGATION ENVIRONMENT USING MEASUREMENTS FROM A SMALL BUOY by Andrew E. Sweeney June 2017 Thesis Advisor: Qing Wang...TYPE AND DATES COVERED Master’s thesis 4. TITLE AND SUBTITLE QUANTIFYING ELECTROMAGNETIC WAVE PROPAGATION ENVIRONMENT USING MEASUREMENTS FROM A...the Coupled Air Sea Processes and Electromagnetic (EM) ducting Research (CASPER), to understand air-sea interaction processes and their representation

SSEM: A model for simulating runoff and erosion of saline-sodic soil slopes under coastal reclamation

NASA Astrophysics Data System (ADS)

Liu, Dongdong; She, Dongli

2018-06-01

Current physically based erosion models do not carefully consider the dynamic variations of soil properties during rainfall and are unable to simulate saline-sodic soil slope erosion processes. The aim of this work was to build upon a complete model framework, SSEM, to simulate runoff and erosion processes for saline-sodic soils by coupling dynamic saturated hydraulic conductivity Ks and soil erodibility Kτ. Sixty rainfall simulation rainfall experiments (2 soil textures × 5 sodicity levels × 2 slope gradients × 3 duplicates) provided data for model calibration and validation. SSEM worked very well for simulating the runoff and erosion processes of saline-sodic silty clay. The runoff and erosion processes of saline-sodic silt loam were more complex than those of non-saline soils or soils with higher clay contents; thus, SSEM did not perform very well for some validation events. We further examined the model performances of four concepts: Dynamic Ks and Kτ (Case 1, SSEM), Dynamic Ks and Constant Kτ (Case 2), Constant Ks and Dynamic Kτ (Case 3) and Constant Ks and Constant Kτ (Case 4). The results demonstrated that the model, which considers dynamic variations in soil saturated hydraulic conductivity and soil erodibility, can provide more reasonable runoff and erosion prediction results for saline-sodic soils.

Cropping system effects on wind erosion potential

USDA-ARS?s Scientific Manuscript database

Wind erosion of soil is a destructive process impacting crop productivity and human health and safety. The mechanics of wind erosion and soil properties that influence erosion are well understood. Less well-studied are the effects that cropping intensity has upon those soil properties. We collected ...

Time scale bias in erosion rates of glaciated landscapes

PubMed Central

Ganti, Vamsi; von Hagke, Christoph; Scherler, Dirk; Lamb, Michael P.; Fischer, Woodward W.; Avouac, Jean-Philippe

2016-01-01

Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time. PMID:27713925

Time scale bias in erosion rates of glaciated landscapes.

PubMed

Ganti, Vamsi; von Hagke, Christoph; Scherler, Dirk; Lamb, Michael P; Fischer, Woodward W; Avouac, Jean-Philippe

2016-10-01

Deciphering erosion rates over geologic time is fundamental for understanding the interplay between climate, tectonic, and erosional processes. Existing techniques integrate erosion over different time scales, and direct comparison of such rates is routinely done in earth science. On the basis of a global compilation, we show that erosion rate estimates in glaciated landscapes may be affected by a systematic averaging bias that produces higher estimated erosion rates toward the present, which do not reflect straightforward changes in erosion rates through time. This trend can result from a heavy-tailed distribution of erosional hiatuses (that is, time periods where no or relatively slow erosion occurs). We argue that such a distribution can result from the intermittency of erosional processes in glaciated landscapes that are tightly coupled to climate variability from decadal to millennial time scales. In contrast, we find no evidence for a time scale bias in spatially averaged erosion rates of landscapes dominated by river incision. We discuss the implications of our findings in the context of the proposed coupling between climate and tectonics, and interpreting erosion rate estimates with different averaging time scales through geologic time.

Cavitation erosion - scale effect and model investigations

NASA Astrophysics Data System (ADS)

Geiger, F.; Rutschmann, P.

2015-12-01

The experimental works presented in here contribute to the clarification of erosive effects of hydrodynamic cavitation. Comprehensive cavitation erosion test series were conducted for transient cloud cavitation in the shear layer of prismatic bodies. The erosion pattern and erosion rates were determined with a mineral based volume loss technique and with a metal based pit count system competitively. The results clarified the underlying scale effects and revealed a strong non-linear material dependency, which indicated significantly different damage processes for both material types. Furthermore, the size and dynamics of the cavitation clouds have been assessed by optical detection. The fluctuations of the cloud sizes showed a maximum value for those cavitation numbers related to maximum erosive aggressiveness. The finding suggests the suitability of a model approach which relates the erosion process to cavitation cloud dynamics. An enhanced experimental setup is projected to further clarify these issues.

Mechanics of aeolian processes: Soil erosion and dust production

NASA Technical Reports Server (NTRS)

Mehrabadi, M. M.

1989-01-01

Aeolian (wind) processes occur as a result of atmosphere/land-surface system interactions. A thorough understanding of these processes and their physical/mechanical characterization on a global scale is essential to monitoring global change and, hence, is imperative to the fundamental goal of the Earth observing system (Eos) program. Soil erosion and dust production by wind are of consequence mainly in arid and semi arid regions which cover 36 percent of the Earth's land surface. Some recent models of dust production due to wind erosion of agricultural soils and the mechanics of wind erosion in deserts are reviewed and the difficulties of modeling the aeolian transport are discussed.

Geospatial application of the Water Erosion Prediction Project (WEPP) Model

Treesearch

D. C. Flanagan; J. R. Frankenberger; T. A. Cochrane; C. S. Renschler; W. J. Elliot

2011-01-01

The Water Erosion Prediction Project (WEPP) model is a process-based technology for prediction of soil erosion by water at hillslope profile, field, and small watershed scales. In particular, WEPP utilizes observed or generated daily climate inputs to drive the surface hydrology processes (infiltration, runoff, ET) component, which subsequently impacts the rest of the...

Rainfall and sheet power equation for interrill erosion on steep hillslope

USDA-ARS?s Scientific Manuscript database

Splash and sheet erosion processes dominate on most undisturbed hillslopes of rangeland. Interrill soil erosion should consider the influence of both raindrop and sheet flow to work of soil particles detached by raindrop impact and transported by rainfall-disturbed sheet flow. Interrill erosion equa...

Soil water erosion processes in mountain forest catchment - analysis by using terrestrial laser scanning

NASA Astrophysics Data System (ADS)

Dąbek, Paweł; Żmuda, Romuald; Szczepański, Jakub; Ćmielewski, Bartłomiej; Patrzałek, Ciechosław

2013-04-01

The paper presents the results of the analysis of the water erosion processes of soil occurring in forestry mountain catchment area in the region of West Sudetes Mountain in Poland. The research was carried out within the experimental area of skid trails (operational trails), which were used to the end of 2010 in obtaining wood and its mechanical transport to the place of storage. As a consequence of forestry works that were carried out it was changing the natural structure of ground and its surface on the wooded slopes, which, combined with the favorable hydro-meteorological conditions contributed to the intensification of the water erosion processes of soil on surface of trails. For the implementation of the research project of the analysis of water erosion processes in the forestry catchment area innovative was used terrestrial laser scanning. Using terrestrial laser scanning has enabled the analysis of the dynamics of erosion processes both in time, as well as in spatial and quantitative terms. Scanning was performed at a resolution of 4 mm, resulting in 62 500 points per 1 square meter. After filtering the data were interpolated to other resolution of 1 cm, which can identify even the smallest linear and surface effects of erosion. While installed on the experimental area, along the skid trails, anti-erosion barriers in order to reduce transport eroded material and allow its accumulation. Allowed to precisely determine the location of areas of accumulation, the rate and amount of accumulated material. The result of the analyses that was carried out is identification areas of denudation of the eroded material, and also determine the intensity of the erosion processes and their quantitative analysis. The long-term researches on hydrological conditions and forest complexes functioning show that forest effectively stores water, limits linear and surface flow and delays water outflow from a catchment. Carried out a research project using the terrestrial laser scanning shows that anthropogenic activities in the form of forest management and their effects in the form of dense network of forest roads and skid trails and obtaining wood diminish correct functioning of a forest or even increase the phenomenon of erosion. Submit the results of the analysis consider the problem of dynamics and intensity of erosion processes in mountain areas, and show the effectiveness of the methodology of research.

75 FR 75961 - Notice of Implementation of the Wind Erosion Prediction System for Soil Erodibility System...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-07

... Wind Erosion Prediction System for Soil Erodibility System Calculations for the Natural Resources... Erosion Prediction System (WEPS) for soil erodibility system calculations scheduled for implementation for... computer model is a process-based, daily time-step computer model that predicts soil erosion via simulation...

Soil erosion in humid regions: a review

Treesearch

Daniel J. Holz; Karl W.J. Williard; Pamela J. Edwards; Jon E. Schoonover

2015-01-01

Soil erosion has significant implications for land productivity and surface water quality, as sediment is the leading water pollutant worldwide. Here, erosion processes are defined. The dominant factors influencing soil erosion in humid areas are reviewed, with an emphasis on the roles of precipitation, soil moisture, soil porosity, slope steepness and length,...

Ecological site-based assessments of wind and water erosion: informing accelerated soil erosion management in rangelands

USGS Publications Warehouse

Webb, Nicholas P.; Herrick, Jeffrey E.; Duniway, Michael C.

2014-01-01

Accelerated soil erosion occurs when anthropogenic processes modify soil, vegetation or climatic conditions causing erosion rates at a location to exceed their natural variability. Identifying where and when accelerated erosion occurs is a critical first step toward its effective management. Here we explore how erosion assessments structured in the context of ecological sites (a land classification based on soils, landscape setting and ecological potential) and their vegetation states (plant assemblages that may change due to management) can inform systems for reducing accelerated soil erosion in rangelands. We evaluated aeolian horizontal sediment flux and fluvial sediment erosion rates for five ecological sites in southern New Mexico, USA, using monitoring data and rangeland-specific wind and water erosion models. Across the ecological sites, plots in shrub-encroached and shrub-dominated vegetation states were consistently susceptible to aeolian sediment flux and fluvial sediment erosion. Both processes were found to be highly variable for grassland and grass-succulent states across the ecological sites at the plot scale (0.25 Ha). We identify vegetation thresholds that define cover levels below which rapid (exponential) increases in aeolian sediment flux and fluvial sediment erosion occur across the ecological sites and vegetation states. Aeolian sediment flux and fluvial erosion in the study area can be effectively controlled when bare ground cover is 100 cm in length is less than ~35%. Land use and management activities that alter cover levels such that they cross thresholds, and/or drive vegetation state changes, may increase the susceptibility of areas to erosion. Land use impacts that are constrained within the range of natural variability should not result in accelerated soil erosion. Evaluating land condition against the erosion thresholds identified here will enable identification of areas susceptible to accelerated soil erosion and the development of practical management solutions.

A field method for soil erosion measurements in agricultural and natural lands

Treesearch

Y.P. Hsieh; K.T. Grant; G.C. Bugna

2009-01-01

Soil erosion is one of the most important watershed processes in nature, yet quantifying it under field conditions remains a challenge. The lack of soil erosion field data is a major factor hindering our ability to predict soil erosion in a watershed. We present here the development of a simple and sensitive field method that quantifies soil erosion and the resulting...

Electromagnetic Torque in Tokamaks with Toroidal Asymmetries

DOE Office of Scientific and Technical Information (OSTI.GOV)

Logan, Nikolas Christopher

2015-01-01

Lithium and boron coatings are applied to the walls of many tokamaks to enhance performance and protect the underlying substrates. Li and B-coated high-Z substrates are planned for use in NSTX-U and are a candidate plasma-facing component (PFC) for DEMO. However, previous measurements of Li evaporation and thermal sputtering on low-flux devices indicate that the Li temperature permitted on such devices may be unacceptably low. Thus it is crucial to characterize gross and net Li erosion rates under high-flux plasma bombardment. Additionally, no quantitative measurements have been performed of the erosion rate of a boron-coated PFC during plasma bombardment. Amore » realistic model for the compositional evolution of a Li layer under D bombardment was developed that incorporates adsorption, implantation, and diffusion. A model was developed for temperature-dependent mixed-material Li-D erosion that includes evaporation, physical sputtering, chemical sputtering, preferential sputtering, and thermal sputtering. The re-deposition fraction of a Li coating intersecting a linear plasma column was predicted using atomic physics information and by solving the Li continuity equation. These models were tested in the Magnum-PSI linear plasma device at ion fluxes of 10^23-10^24 m^-2 s^-1 and Li surface temperatures less than 800 degrees C. Li erosion was measured during bombardment with a neon plasma that will not chemically react with Li and the results agreed well with the erosion model. Next the ratio of the total D fluence to the areal density of the Li coating was varied to quantify differences in Li erosion under D plasma bombardment as a function of the D concentration. The ratio of D/Li atoms was calculated using the results of MD simulations and good agreement is observed between measurements and the predictions of the mixed-material erosion model. Li coatings are observed to disappear from graphite much faster than from TZM Mo, indicating that fast Li diffusion into the bulk graphite substrate occurred, as predicted. Li re-deposition fractions very close to unity are observed in Magnum-PSI, as predicted by modeling. Finally, predictions of Li coating lifetimes in the NSTX-U divertor are calculated. The gross erosion rate of boron coatings was also measured for the first time in a high-flux plasma device.« less

Critical role of wind-wave induced erosion on the morphodynamic evolution of shallow tidal basins

NASA Astrophysics Data System (ADS)

D'Alpaos, Andrea; Carniello, Luca; Rinaldo, Andrea

2014-05-01

Wind-wave induced erosion processes are among the chief processes which govern the morphodynamic evolution of shallow tidal basins, both in the vertical and in the horizontal plane. Wind-wave induced bottom shear stresses can promote the disruption of the polymeric microphytobenthic biofilm and lead to the erosion of tidal-flat surfaces and to the increase in suspended sediment concentration which affects the stability of intertidal ecosystems. Moreover, the impact of wind-waves on salt-marsh margins can lead to the lateral erosion of marsh boundaries thus promoting the disappearance of salt-marsh ecosystems. Towards the goal of developing a synthetic theoretical framework to represent wind wave-induced resuspension events and account for their erosional effects on the long-term biomorphodynamic evolution of tidal systems, we have employed a complete, coupled finite element model accounting for the role of wind waves and tidal currents on the hydrodynamic circulation in shallow basins. Our analyses of the characteristics of combined current and wave-induced exceedances in bottom shear stress over a given threshold for erosion, suggest that wind wave-induced resuspension events can be modeled as a marked Poisson process. The interarrival time of wave-induced erosion events is, in fact, an exponentially distributed random variable, as well as the duration and intensity of overthreshold events. Moreover, the analysis of wind-wave induced resuspension events for different historical configurations of the Venice Lagoon from the 19th to the 21st century, shows that the interarrival times of erosion events have dramatically decreased through the last two centuries, whereas the intensities of erosion events have experienced a surprisingly high increase. This allows us to characterize the threatening erosion and degradation processes that the Venice Lagoon has been experiencing since the beginning of the last century.

Metal droplet erosion and shielding plasma layer under plasma flows typical of transient processes in tokamaks

DOE Office of Scientific and Technical Information (OSTI.GOV)

Martynenko, Yu. V., E-mail: Martynenko-YV@nrcki.ru

It is shown that the shielding plasma layer and metal droplet erosion in tokamaks are closely interrelated, because shielding plasma forms from the evaporated metal droplets, while droplet erosion is caused by the shielding plasma flow over the melted metal surface. Analysis of experimental data and theoretical models of these processes is presented.

Geomorphic processes active in the Southwestern Louisiana Canal, Lafourche Parish, Louisiana

NASA Technical Reports Server (NTRS)

Doiron, L. N.; Whitehurst, C. A.

1974-01-01

The geomorphological changes causing the destruction of the banks of the Southwestern Louisiana Canal are studied by means of field work, laboratory analyses, and infrared color imagery interpretation. Turbulence and flow patterns are mapped, and related to erosion and sediment deposition processes. The accelerated erosion rate of the last decade is discussed, with two causative factors cited: (1) development of faster boats, increasing bank and bottom erosion, and (2) a subsequently larger tidal influx, with greater erosive ability. The physical properties of the canal bank materials are also analyzed. It is concluded that channel erosion progressively increases, with no indications of stabilization, until they merge with other waterways and become indistinguishable from natural water bodies.

A letter of intent for an experiment to study strong electromagnetic fields at RHIC via multiple electromagnetic processes

NASA Technical Reports Server (NTRS)

Fatyga, M.; Norbury, John W.

1992-01-01

An experimental program at the Relativistic Heavy Ion Collider (RHIC) which is designed to study nonperturbative aspects of electrodynamics is outlined. Additional possibilities for new studies of electrodynamics via multiple electromagnetic processes are also described.

A new experimental material for modeling relief dynamics and interactions between tectonics and surface processes

NASA Astrophysics Data System (ADS)

Graveleau, F.; Hurtrez, J.-E.; Dominguez, S.; Malavieille, J.

2011-12-01

We developed a new granular material (MatIV) to study experimentally landscape evolution in active mountain belt piedmonts. Its composition and related physical properties have been determined using empirical criteria derived from the scaling of deformation, erosion-transport and sedimentation natural processes. MatIV is a water-saturated composite material made up with 4 granular components (silica powder, glass microbeads, plastic powder and graphite) whose physical, mechanical and erosion-related properties were measured with different laboratory tests. Mechanical measurements were made on a modified Hubbert-type direct shear apparatus. Erosion-related properties were determined using an experimental set-up that allows quantifying the erosion/sedimentation budget from tilted relaxation topographies. For MatIV, we also investigated the evolution of mean erosion rates and stream power erosion law exponents in 1D as a function of slope. Our results indicate that MatIV satisfies most of the defined criteria. It deforms brittlely according to the linear Mohr-Coulomb failure criterion and localizes deformation along discrete faults. Its erosion pattern is characterized by realistic hillslope and channelized processes (slope diffusion, mass wasting, channel incision). During transport, eroded particles are sorted depending on their density and shape, which results in stratified alluvial deposits displaying lateral facies variations. To evaluate the degree of similitude between model and nature, we used a new experimental device that combines accretionary wedge deformation mechanisms and surface runoff erosion processes. Results indicate that MatIV succeeded in producing detailed morphological and sedimentological features (drainage basin, channel network, terrace, syntectonic alluvial fan). Geometric, kinematic and dynamic similarity criteria have been investigated to compare precisely model to nature. Although scaling is incomplete, it yields particularly informative orders of magnitude. With all these characteristics, MatIV appears as a very promising material to investigate experimentally a wide range of scientific questions dealing with relief dynamics and interactions between tectonics, erosion and sedimentation processes.

Linking Soil Moisture Variation and Abundance of Plants to Geomorphic Processes: A Generalized Model for Erosion-Uplifting Landscapes

NASA Astrophysics Data System (ADS)

Ding, Junyan; Johnson, Edward A.; Martin, Yvonne E.

2018-03-01

The diffusive and advective erosion-created landscapes have similar structure (hillslopes and channels) across different scales regardless of variations in drivers and controls. The relative magnitude of diffusive erosion to advective erosion (D/K ratio) in a landscape development model controls hillslope length, shape, and drainage density, which regulate soil moisture variation, one of the critical resources of plants, through the contributing area (A) and local slope (S) represented by a topographic index (TI). Here we explore the theoretical relation between geomorphic processes, TI, and the abundance and distribution of plants. We derived an analytical model that expresses the TI with D, K, and A. This gives us the relation between soil moisture variation and geomorphic processes. Plant tolerance curves are used to link plant performance to soil moisture. Using the hypothetical tolerance curves of three plants, we show that the abundance and distribution of xeric, mesic, and hydric plants on the landscape are regulated by the D/K ratio. Where diffusive erosion is the major erosion process (large D/K ratio), mesic plants have higher abundance relative to xeric and hydric plants and the landscape has longer and convex-upward hillslope and low channel density. Increasing the dominance of advective erosion increases relative abundance of xeric and hydric plants dominance, and the landscape has short and concave hillslope and high channel density.

Effects of low-scale landscape structures on aeolian transport processes on arable land

NASA Astrophysics Data System (ADS)

Siegmund, Nicole; Funk, Roger; Koszinsky, Sylvia; Buschiazzo, Daniel Eduardo; Sommer, Michael

2018-06-01

The landscape of the semiarid Pampa in central Argentina is characterized by late Pleistocene aeolian deposits, covering large plains with sporadic dune structures. Since the current land use changed from extensive livestock production within the Caldenal forest ecosystem to arable land, the wind erosion risk increased distinctly. We measured wind erosion and deposition patterns at the plot scale and investigated the spatial variability of the erosion processes. The wind-induced mass-transport was measured with 18 Modified Wilson and Cooke samplers (MWAC), installed on a 1.44 ha large field in a 20 × 40 m grid. Physical and chemical soil properties from the upper soil as well as a digital elevation model were recorded in a 20 × 20 m grid. In a 5-month measuring campaign data from seven storms with three different wind directions was obtained. Results show very heterogeneous patterns of erosion and deposition for each storm and indicate favoured erosion on windward and deposits on leeward terrain positions. Furthermore, a multiple regression model was build, explaining up to 70% of the spatial variance of erosion by just using four predictors: topsoil thickness, relative elevation, soil organic carbon content and slope direction. Our findings suggest a structure-process-structure complex where the landscape structure determines the effects of recent wind erosion processes which again slowly influence the structure, leading to a gradual increase of soil heterogeneity.

15 CFR 923.25 - Shoreline erosion/mitigation planning.

Code of Federal Regulations, 2010 CFR

2010-01-01

... purpose in developing this planning process is to give special attention to erosion issues. This special management attention may be achieved by designating erosion areas as areas of particular concern pursuant to...

Forces acting on particles in a Pelton bucket and similarity considerations for erosion

NASA Astrophysics Data System (ADS)

Rai, A. K.; Kumar, A.; Staubli, T.

2016-11-01

High sediment transport rates cause severe erosion issues in hydropower plants leading to interruptions in power generation, decrease in efficiency and shutdown for repair and maintenance. For Pelton turbines operating at high head, the issue of erosion is severe, especially in components like buckets, nozzle rings and needles. Goal of the study is to develop erosion focussed guidelines for both designing as well as operating hydropower plants with Pelton runners. In this study, the flow of sediment inside a Pelton bucket with respect to forces acting on solid particles is analysed with an analytical approach by considering different dynamic forces originating from the rotation of the turbine, the curvature of the buckets, and the Coriolis effect. Further, the path of sediment particles and its effect on erosion phenomena are analysed based on the process of separation of different sized sediment particles from streamlines. The data relating to head, power, discharge, number of jet and efficiency of 250 hydropower plants installed all over the world were analysed in this study to find the major factors related to erosion in Pelton turbine bucket. From analysis of different force ratios, it is found that an increase of D/B, i.e. the ratio of pitch circle diameter and bucket width, and/or decrease of specific speed (nq) enhances erosion. As the erosion process depends significantly on nondimensional parameters D/B and nq, these are considered as similarity measures for scaling of the erosion process in the Pelton buckets of various sizes.

Rainfall simulations as a tool for quantification of soil erosion processes caused by the trampling of sheep and goats in semi-arid and arid landscapes

NASA Astrophysics Data System (ADS)

Ruthenberg, Jonas; Tumbrink, Jonas; Wilms, Tobias; Peter, Klaus Daniel; Wirtz, Stefan; Ries, Johannes B.

2015-04-01

As there is a massive increase of livestock husbandry in semi-arid and arid landscapes, the investigation of trampling-induced soil erosion has become indispensable for a better understanding of erosive processes such as loosening and translocation of sediment, as well as the genesis of rill erosion and gully systems. Our work will support other studies focusing on desertification and land-use changes in the investigated landscapes. Up to this date, research on livestock-induced soil erosion, even in relation to other erosion processes such as aeolian and fluvial/pluvial sediment translocation, is very scarcely found in literature. The presented study on trampling-induced soil erosion by sheep and goats in arid and semi-arid landscapes aims to create a general understanding, an estimation and quantification of the influencing factors of these erosive processes. Within this study, we present the first results of several field rainfall experiments on rock fragment translocation as well as loosening and transportation of coarse and fine sediment depending on the motion sequence and the individual weight, size, and hoof beat of the animals. Furthermore, we conducted additional experiments to investigate the trampling-induced erosion processes for various other sediments, especially those in the range of clay, silt, and sand. To do so, we used a specially designed test plot, equipped with sediment traps on each side. For a clear and reliable analysis of the measured parameters, univariate as well as multivariate statistical methods have been used. For all field methods, we developed relevant statements concerning flock size. The rock fragment translocation experiments done so fare have shown that a flock of 45 sheep or goats moved 87 % of 320 spread out rock fragments with a mean translocation distance of 0.123 m when trampling across a test plot of 3.2 m^2. Besides that we found out that the soil surface was worked up in a way that the loosened fine sediment proved to be easily detachable by secondary erosive processes such as rainfall. The conducted rainfall simulations confirmed this assumption. They have shown that sediment yields were significantly higher on trail areas than on intershrub or shrub areas. The preliminary work done up until now suggests that the grazing and trampling of sheep and goats can be regarded as an important factor for soil degradation in semi-arid and arid landscapes. However, the understanding of the erosive processes in detail remains to be defined, i.e. the exact movement of the sheep and goats, the energy they can impart with their hooves, and how that energy affects different sediments or surfaces they tread upon, as well as the general quantification of trampling-induced erosion rates and transport processes of clastic sediments.

An holistic approach to beach erosion vulnerability assessment.

PubMed

Alexandrakis, George; Poulos, Serafim Ε

2014-08-15

Erosion is a major threat for coasts worldwide, beaches in particular, which constitute one of the most valuable coastal landforms. Vulnerability assessments related to beach erosion may contribute to planning measures to counteract erosion by identifying, quantifying and ranking vulnerability. Herein, we present a new index, the Beach Vulnerability Index (BVI), which combines simplicity in calculations, easily obtainable data and low processing capacity. This approach provides results not only for different beaches, but also for different sectors of the same beach and enables the identification of the relative significance of the processes involved. It functions through the numerical approximation of indicators that correspond to the mechanisms related to the processes that control beach evolution, such as sediment availability, wave climate, beach morhodynamics and sea level change. The BVI is also intended to be used as a managerial tool for beach sustainability, including resilience to climate change impact on beach erosion.

The interactions between attrition, abrasion and erosion in tooth wear.

PubMed

Shellis, R Peter; Addy, Martin

2014-01-01

Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear through tooth-tooth contact) and erosion (dissolution of hard tissue by acidic substances). A further process (abfraction) might potentiate wear by abrasion and/or erosion. Knowledge of these tooth wear processes and their interactions is reviewed. Both clinical and experimental observations show that individual wear mechanisms rarely act alone but interact with each other. The most important interaction is the potentiation of abrasion by erosive damage to the dental hard tissues. This interaction seems to be the major factor in occlusal and cervical wear. The available evidence is insufficient to establish whether abfraction is an important contributor to tooth wear in vivo. Saliva can modulate erosive/abrasive tooth wear, especially through formation of pellicle, but cannot prevent it. © 2014 S. Karger AG, Basel.

Dynamics of Soil Organic Carbon and Microbial Biomass Carbon in Relation to Water Erosion and Tillage Erosion

PubMed Central

Xiaojun, Nie; Jianhui, Zhang; Zhengan, Su

2013-01-01

Dynamics of soil organic carbon (SOC) are associated with soil erosion, yet there is a shortage of research concerning the relationship between soil erosion, SOC, and especially microbial biomass carbon (MBC). In this paper, we selected two typical slope landscapes including gentle and steep slopes from the Sichuan Basin, China, and used the 137Cs technique to determine the effects of water erosion and tillage erosion on the dynamics of SOC and MBC. Soil samples for the determination of 137Cs, SOC, MBC and soil particle-size fractions were collected on two types of contrasting hillslopes. 137Cs data revealed that soil loss occurred at upper slope positions of the two landscapes and soil accumulation at the lower slope positions. Soil erosion rates as well as distribution patterns of the <0.002-mm clay shows that water erosion is the major process of soil redistribution in the gentle slope landscape, while tillage erosion acts as the dominant process of soil redistribution in the steep slope landscape. In gentle slope landscapes, both SOC and MBC contents increased downslope and these distribution patterns were closely linked to soil redistribution rates. In steep slope landscapes, only SOC contents increased downslope, dependent on soil redistribution. It is noticeable that MBC/SOC ratios were significantly lower in gentle slope landscapes than in steep slope landscapes, implying that water erosion has a negative effect on the microbial biomass compared with tillage erosion. It is suggested that MBC dynamics are closely associated with soil redistribution by water erosion but independent of that by tillage erosion, while SOC dynamics are influenced by soil redistribution by both water erosion and tillage erosion. PMID:23717530

Characteristics of pulsed runoff-erosion events under typical rainstorms in a small watershed on the Loess Plateau of China.

PubMed

Wu, Lei; Jiang, Jun; Li, Gou-Xia; Ma, Xiao-Yi

2018-02-27

The pulsed events of rainstorm erosion on the Loess Plateau are well-known, but little information is available concerning the characteristics of superficial soil erosion processes caused by heavy rainstorms at the watershed scale. This study statistically evaluated characteristics of pulsed runoff-erosion events based on 17 observed rainstorms from 1997-2010 in a small loess watershed on the Loess Plateau of China. Results show that: 1) Rainfall is the fundamental driving force of soil erosion on hillslopes, but the correlations of rainfall-runoff and rainfall-sediment in different rainstorms are often scattered due to infiltration-excess runoff and soil conservation measures. 2) Relationships between runoff and sediment for each rainstorm event can be regressed by linear, power, logarithmic and exponential functions. Cluster Analysis is helpful in classifying runoff-erosion events and formulating soil conservation strategies for rainstorm erosion. 3) Response characteristics of sediment yield are different in different levels of pulsed runoff-erosion events. Affected by rainfall intensity and duration, large changes may occur in the interactions between flow and sediment for different flood events. Results provide new insights into runoff-erosion processes and will assist soil conservation planning in the loess hilly region.

AERO: A Decision Support Tool for Wind Erosion Assessment in Rangelands and Croplands

NASA Astrophysics Data System (ADS)

Galloza, M.; Webb, N.; Herrick, J.

2015-12-01

Wind erosion is a key driver of global land degradation, with on- and off-site impacts on agricultural production, air quality, ecosystem services and climate. Measuring rates of wind erosion and dust emission across land use and land cover types is important for quantifying the impacts and identifying and testing practical management options. This process can be assisted by the application of predictive models, which can be a powerful tool for land management agencies. The Aeolian EROsion (AERO) model, a wind erosion and dust emission model interface provides access by non-expert land managers to a sophisticated wind erosion decision-support tool. AERO incorporates land surface processes and sediment transport equations from existing wind erosion models and was designed for application with available national long-term monitoring datasets (e.g. USDI BLM Assessment, Inventory and Monitoring, USDA NRCS Natural Resources Inventory) and monitoring protocols. Ongoing AERO model calibration and validation are supported by geographically diverse data on wind erosion rates and land surface conditions collected by the new National Wind Erosion Research Network. Here we present the new AERO interface, describe parameterization of the underpinning wind erosion model, and provide a summary of the model applications across agricultural lands and rangelands in the United States.

Internal erosion during soil pipe flow: Role in gully erosion and hillslope instability

USDA-ARS?s Scientific Manuscript database

Many field observations have lead to speculation on the role of piping in embankment failures, landslides, and gully erosion. However, there has not been a consensus on the subsurface flow and erosion processes involved and inconsistent use of terms have exasperated the problem. One such piping proc...

The limits on the usefulness of erosion hazard ratings

Treesearch

R. M. Rice; P. D. Gradek

1984-01-01

Although erosion-hazard ratings are often used to guide forest practices, those used in California from 1974 to 1982 have been inadequate for estimating erosion potential. To improve the erosion-hazard rating procedure, separate estimating equations were used for different situations. The ratings were partitioned according to yarding method, erosional process, and...

Performance of the SWEEP model affected by estimates of threshold friction velocity

USDA-ARS?s Scientific Manuscript database

The Wind Erosion Prediction System (WEPS) is a process-based model and needs to be verified under a broad range of climatic, soil, and management conditions. Occasional failure of the WEPS erosion submodel (Single-event Wind Erosion Evaluation Program or SWEEP) to simulate erosion in the Columbia Pl...

Disc valve for sampling erosive process streams

DOEpatents

Mrochek, J.E.; Dinsmore, S.R.; Chandler, E.W.

1986-01-07

A four-port disc valve is described for sampling erosive, high temperature process streams. A rotatable disc defining opposed first and second sampling cavities rotates between fired faceplates defining flow passageways positioned to be alternatively in axial alignment with the first and second cavities. Silicon carbide inserts and liners composed of [alpha] silicon carbide are provided in the faceplates and in the sampling cavities to limit erosion while providing lubricity for a smooth and precise operation when used under harsh process conditions. 1 fig.

Design and testing of a coil-unit barrel for helical coil electromagnetic launcher

NASA Astrophysics Data System (ADS)

Yang, Dong; Liu, Zhenxiang; Shu, Ting; Yang, Lijia; Ouyang, Jianming

2018-01-01

A coil-unit barrel for a helical coil electromagnetic launcher is described. It provides better features of high structural strength and flexible adjustability. It is convenient to replace the damaged coil units and easy to adjust the number of turns in the stator coils due to the modular design. In our experiments, the highest velocity measured for a 4.5-kg projectile is 47.3 m/s and the mechanical reinforcement of the launcher could bear 35 kA peak current. The relationship between the energy conversion efficiency and the inductance gradient of the launcher is also studied. In the region of low inductance gradient, the efficiency is positively correlated with the inductance gradient. However, in the region of high inductance gradient, the inter-turn arc erosion becomes a major problem of limiting the efficiency and velocity of the launcher. This modular barrel allows further studies in the inter-turn arc and the variable inductance gradient helical coil launcher.

Design and testing of a coil-unit barrel for helical coil electromagnetic launcher.

PubMed

Yang, Dong; Liu, Zhenxiang; Shu, Ting; Yang, Lijia; Ouyang, Jianming

2018-01-01

A coil-unit barrel for a helical coil electromagnetic launcher is described. It provides better features of high structural strength and flexible adjustability. It is convenient to replace the damaged coil units and easy to adjust the number of turns in the stator coils due to the modular design. In our experiments, the highest velocity measured for a 4.5-kg projectile is 47.3 m/s and the mechanical reinforcement of the launcher could bear 35 kA peak current. The relationship between the energy conversion efficiency and the inductance gradient of the launcher is also studied. In the region of low inductance gradient, the efficiency is positively correlated with the inductance gradient. However, in the region of high inductance gradient, the inter-turn arc erosion becomes a major problem of limiting the efficiency and velocity of the launcher. This modular barrel allows further studies in the inter-turn arc and the variable inductance gradient helical coil launcher.

Soil erosion and the global carbon budget.

PubMed

Lal, R

2003-07-01

Soil erosion is the most widespread form of soil degradation. Land area globally affected by erosion is 1094 million ha (Mha) by water erosion, of which 751 Mha is severely affected, and 549 Mha by wind erosion, of which 296 Mha is severely affected. Whereas the effects of erosion on productivity and non-point source pollution are widely recognized, those on the C dynamics and attendant emission of greenhouse gases (GHGs) are not. Despite its global significance, erosion-induced carbon (C) emission into the atmosphere remains misunderstood and an unquantified component of the global carbon budget. Soil erosion is a four-stage process involving detachment, breakdown, transport/redistribution and deposition of sediments. The soil organic carbon (SOC) pool is influenced during all four stages. Being a selective process, erosion preferentially removes the light organic fraction of a low density of <1.8 Mg/m(3). A combination of mineralization and C export by erosion causes a severe depletion of the SOC pool on eroded compared with uneroded or slightly eroded soils. In addition, the SOC redistributed over the landscape or deposited in depressional sites may be prone to mineralization because of breakdown of aggregates leading to exposure of hitherto encapsulated C to microbial processes among other reasons. Depending on the delivery ratio or the fraction of the sediment delivered to the river system, gross erosion by water may be 75 billion Mg, of which 15-20 billion Mg are transported by the rivers into the aquatic ecosystems and eventually into the ocean. The amount of total C displaced by erosion on the earth, assuming a delivery ratio of 10% and SOC content of 2-3%, may be 4.0-6.0 Pg/year. With 20% emission due to mineralization of the displaced C, erosion-induced emission may be 0.8-1.2 Pg C/year on the earth. Thus, soil erosion has a strong impact on the global C cycle and this component must be considered while assessing the global C budget. Adoption of conservation-effective measures may reduce the risks of C emission and sequester C in soil and biota.

Application of geoelectric and electromagnetic methods for the detection of failing zones and brine rising zones in the vicinity of a potential CO2-storage site

NASA Astrophysics Data System (ADS)

Herd, Rainer; Krause, Yvonne; Schafrik, Wlad

2013-04-01

Within the framework of the project "brine - CO2 storage in eastern Brandenburg" geophysical investigations are conducted by the German Research Center for Geoscience (GFZ), Potsdam and the Brandenburg University of Technology (BTU), Cottbus on different scales in order to investigate underground situations and evaluate methods suitable for a salinization early warning system. The research of BTU is focused on the distribution of underground structures up to a maximum depth of 200m. Of prevalent interest are the detection capabilities for near surface failing zones which might serve as favored pathways for brine migration and the status-quo of the freshwater-saltwater boundary. Geophysical investigations with the frequency domain electromagnetic (FDEM) and direct current (DC) geoelectric methods are qualified for the identification and monitoring of brine displacement as the measuring parameter is the resistivity/conductivity of the subsurface. In eastern Brandenburg the Oligocene Rupelian clay represents the barrier horizon separating the freshwater and saline aquifers. Due to postglacial processes this layer is locally reduced or totally eroded and might enhance upward brine migration during pressure increase. The areas of investigation were selected by known high fluid conductivity values (hydro chemical indication) and the potential presence of quaternary erosion channels in the Rupelian clay (geological indication). The geophysical results yield a vertical and horizontal resistivity/conductivity distribution. The interpretation is done by lithology profiles of nearby boreholes and correlation with fluid conductivities in groundwater wells. The results of FDEM and DC on coincident profiles are generally in accordance and show that both methods are suitable with DC geoelectrics supplementing a higher resolution close to the surface (max. 80m depth) and the electromagnetics adding coarser/less detailed conductivity information of the deeper underground (down to 200m depth).

Urine metabolic profiling for the pathogenesis research of erosive oral lichen planus.

PubMed

Li, Xu-Zhao; Yang, Xu-Yan; Wang, Yu; Zhang, Shuai-Nan; Zou, Wei; Wang, Yan; Li, Xiao-Nan; Wang, Ling-Shu; Zhang, Zhi-Gang; Xie, Liang-Zhen

2017-01-01

Oral lichen planus (OLP) is a relatively common chronic immune-pathological and inflammatory disease and potentially oral precancerous lesion. Erosive OLP patients show the higher rate of malignant transformation than patients with non-erosive OLP. Identifying the potential biomarkers related to erosive OLP may help to understand the pathogenesis of the diseases. Metabolic profiles were compared in control and patient subjects with erosive OLP by using ultra-performance liquid chromatography-quadrupole time-of-flight-mass spectrometry (UPLC-QTOF-MS) coupled with pattern recognition methods An integrative analysis was used to identify the perturbed metabolic pathways and pathological processes that may be associated with the disease. In total, 12 modulated metabolites were identified and considered as the potential biomarkers of erosive OLP. Multiple metabolic pathways and pathological processes were involved in erosive OLP. The dysregulations of these metabolites could be used to explain the pathogenesis of the disease, which could also be the potential therapeutic targets for the disease. Copyright © 2016 Elsevier Ltd. All rights reserved.

Soil erosion - a local and national problem

Treesearch

C.G. Bates; O.R. Zeasman

1930-01-01

The erosion of soils through the action of rain water and that from melting snow is almost universal in its occurrence. The gradual erosion and levelling of any country is inevitable, being a process which has gone on as long as there has been free water on the face of the earth. Nevertheless, this process is an extremely slow one where the landscape is naturally well...

An integrated assessment of soil erosion dynamics with special emphasis on gully erosion: Case studies from South Africa and Iran

NASA Astrophysics Data System (ADS)

Maerker, Michael; Sommer, Christian; Zakerinejad, Reza; Cama, Elena

2017-04-01

Soil erosion by water is a significant problem in arid and semi arid areas of large parts of Iran. Water erosion is one of the most effective phenomena that leads to decreasing soil productivity and pollution of water resources. Especially in semiarid areas like in the Mazayjan watershed in the Southwestern Fars province as well as in the Mkomazi catchment in Kwa Zulu Natal, South Africa, gully erosion contributes to the sediment dynamics in a significant way. Consequently, the intention of this research is to identify the different types of soil erosion processes acting in the area with a stochastic approach and to assess the process dynamics in an integrative way. Therefore, we applied GIS, and satellite image analysis techniques to derive input information for the numeric models. For sheet and rill erosion the Unit Stream Power-based Erosion Deposition Model (USPED) was utilized. The spatial distribution of gully erosion was assessed using a statistical approach which used three variables (stream power index, slope, and flow accumulation) to predict the spatial distribution of gullies in the study area. The eroded gully volumes were estimated for a multiple years period by fieldwork and Google Earth high resolution images as well as with structure for motion algorithm. Finally, the gully retreat rates were integrated into the USPED model. The results show that the integration of the SPI approach to quantify gully erosion with the USPED model is a suitable method to qualitatively and quantitatively assess water erosion processes in data scarce areas. The application of GIS and stochastic model approaches to spatialize the USPED model input yield valuable results for the prediction of soil erosion in the test areas. The results of this research help to develop an appropriate management of soil and water resources in the study areas.

An Improved Experimental Method for Simulating Erosion Processes by Concentrated Channel Flow

PubMed Central

Chen, Xiao-Yan; Zhao, Yu; Mo, Bin; Mi, Hong-Xing

2014-01-01

Rill erosion is an important process that occurs on hill slopes, including sloped farmland. Laboratory simulations have been vital to understanding rill erosion. Previous experiments obtained sediment yields using rills of various lengths to get the sedimentation process, which disrupted the continuity of the rill erosion process and was time-consuming. In this study, an improved experimental method was used to measure the rill erosion processes by concentrated channel flow. By using this method, a laboratory platform, 12 m long and 3 m wide, was used to construct rills of 0.1 m wide and 12 m long for experiments under five slope gradients (5, 10, 15, 20, and 25 degrees) and three flow rates (2, 4, and 8 L min−1). Sediment laden water was simultaneously sampled along the rill at locations 0.5 m, 1 m, 2 m, 3 m, 4 m, 5 m, 6 m, 7 m, 8 m, 10 m, and 12 m from the water inlet to determine the sediment concentration distribution. The rill erosion process measured by the method used in this study and that by previous experimental methods are approximately the same. The experimental data indicated that sediment concentrations increase with slope gradient and flow rate, which highlights the hydraulic impact on rill erosion. Sediment concentration increased rapidly at the initial section of the rill, and the rate of increase in sediment concentration reduced with the rill length. Overall, both experimental methods are feasible and applicable. However, the method proposed in this study is more efficient and easier to operate. This improved method will be useful in related research. PMID:24949621

[Sediment transport characteristics at different erosion stages for non-hardened roads of the Shenfu Coalfield, west China].

PubMed

Guo, Ming-ming; Wang, Wen-long; Li, Jian-ming; Huang, Peng-fei; Zhu, Bao-cai; Wang, Zhen; Luo, Ting

2015-02-01

Non-hardened roads formed in the production of the Shenfu Coalfield have a unique condition of underlying surface. The road surface is composed of a regolith layer with a certain thickness resulted from long-term rolling and thus, is characterized by weakened anti-scourabilty and anti-erodibility. In contrast, soil layer below the regolith has a higher bulk density and anti-erodibility. The processes of soil erosion on the non-hardened roads exhibit some differences under rainfall condition. The process of sediment transport and the relationship between sediment transport rate and erosion factors at different erosion stages were studied on non-hardened roads with slope degrees ranging from 3° to 12° (3°, 6°, 9°, 12°) by a field experiment under artificial rainfall. Results showed that the first peak of sediment transport on the regolith surface was observed at the sheet erosion stage. Sheet erosion occurred only at 3° slope degree, with an average variation coefficient of 0.07 for sediment transport rate. Rills in every testing began to develop at slope degrees of 6° to 12° about 15 min after runoff initiation. At the sheet erosion stage, the process of sediment transport fluctuated considerably at rainfall intensities of > 1.5 mm · min(-1), but the differences in its variation were little at the three slope degrees, with average variation coefficients of 0.20, 0.19 and 0.16, respectively. Rainfall intensity had a more significant impact on sediment transport rate than slope degree. The process of sediment transport at the rill erosion stage fluctuated, but the fluctuation was obviously smaller than that at the sheet erosion stage, with average variation coefficients of 0.05, 0.09 and 0.10 at the three slope degrees. Many wide and shallow rills evolved at the rill erosion stage. The sediment transport rate could be well predicted by a power function of rainfall intensity and slope degree at the sheet and rill erosion stages. The stable sediment transport rate for all the tests was linearly related to runoff rate and sediment concentration.

Assessment of soil erosion and deposition rates in a Moroccan agricultural field using fallout 137Cs and 210Pbex.

PubMed

Benmansour, M; Mabit, L; Nouira, A; Moussadek, R; Bouksirate, H; Duchemin, M; Benkdad, A

2013-01-01

In Morocco land degradation - mainly caused by soil erosion - is one of the most serious agroenvironmental threats encountered. However, only limited data are available on the actual magnitude of soil erosion. The study site investigated was an agricultural field located in Marchouch (6°42' W, 33° 47' N) at 68 km south east from Rabat. This work demonstrates the potential of the combined use of (137)Cs, (210)Pb(ex) as radioisotopic soil tracers to estimate mid and long term erosion and deposition rates under Mediterranean agricultural areas. The net soil erosion rates obtained were comparable, 14.3 t ha(-1) yr(-1) and 12.1 ha(-1) yr(-1) for (137)Cs and (210)Pb(ex) respectively, resulting in a similar sediment delivery ratio of about 92%. Soil redistribution patterns of the study field were established using a simple spatialisation approach. The resulting maps generated by the use of both radionuclides were similar, indicating that the soil erosion processes has not changed significantly over the last 100 years. Over the previous 10 year period, the additional results provided by the test of the prediction model RUSLE 2 provided results of the same order of magnitude. Based on the (137)Cs dataset established, the contribution of the tillage erosion impact has been evaluated with the Mass Balance Model 3 and compared to the result obtained with the Mass Balance Model 2. The findings highlighted that water erosion is the leading process in this Moroccan cultivated field, tillage erosion under the experimental condition being the main translocation process within the site without a significant and major impact on the net erosion. Copyright © 2012 Elsevier Ltd. All rights reserved.

Understanding soil erosion impacts in temperate agroecosystems: bridging the gap between geomorphology and soil ecology

NASA Astrophysics Data System (ADS)

Baxter, C.; Rowan, J. S.; McKenzie, B. M.; Neilson, R.

2013-04-01

Soil is a key asset of natural capital, providing a myriad of goods and ecosystem services that sustain life through regulating, supporting and provisioning roles, delivered by chemical, physical and biological processes. One of the greatest threats to soil is accelerated erosion, which raises a natural process to unsustainable levels, and has downstream consequences (e.g. economic, environmental and social). Global intensification of agroecosystems is a major cause of soil erosion which, in light of predicted population growth and increased demand for food security, will continue or increase. Elevated erosion and transport is common in agroecosystems and presents a multi-disciplinary problem with direct physical impacts (e.g. soil loss), other less tangible impacts (e.g. loss of ecosystem productivity), and indirect downstream effects that necessitate an integrated approach to effectively address the problem. Climate is also likely to increase susceptibility of soil to erosion. Beyond physical response, the consequences of erosion on soil biota have hitherto been ignored, yet biota play a fundamental role in ecosystem service provision. To our knowledge few studies have addressed the gap between erosion and consequent impacts on soil biota. Transport and redistribution of soil biota by erosion is poorly understood, as is the concomitant impact on biodiversity and ability of soil to deliver the necessary range of ecosystem services to maintain function. To investigate impacts of erosion on soil biota a two-fold research approach is suggested. Physical processes involved in redistribution should be characterised and rates of transport and redistribution quantified. Similarly, cumulative and long-term impacts of biota erosion should be considered. Understanding these fundamental aspects will provide a basis upon which mitigation strategies can be considered.

A field experiment on the controls of sediment transport on bedrock erosion

NASA Astrophysics Data System (ADS)

Beer, A. R.; Turowski, J. M.; Fritschi, B.; Rieke-Zapp, D.; Campana, L.; Lavé, J.

2012-12-01

The earth`s surface is naturally shaped by interactions of physical and chemical processes. In mountainous regions with steep topography river incision fundamentally controls the geomorphic evolution of the whole landscape. There, erosion of exposed bedrock sections by fluvial sediment transport is an important mechanism forming mountain river channels. The links between bedload transport and bedrock erosion has been firmly established using laboratory experiments. However, there are only few field datasets linking discharge, sediment transport, impact energy and erosion that can be used for process understanding and model evaluation. To fill this gap, a new measuring setup has been commissioned to raise an appropriate simultaneous dataset of hydraulics, sediment transport and bedrock erosion at high temporal and spatial resolution. Two natural stone slabs were installed flush with the streambed of the Erlenbach, a gauged stream in the Swiss Pre-Alps. They are mounted upon force sensors recording vertical pressure und downstream shear caused by passing sediment particles. The sediment transport rates can be assessed using geophone plates and an automated moving basket system taking short-term sediment samples. These devices are located directly downstream of the stone slabs. Bedrock erosion rates are measured continuously with erosion sensors at sub-millimeter accuracy at three points on each slab. In addition, the whole slab topography is surveyed with photogrammetry and a structured-light 3D scanner after individual flood events. Since the installation in 2011, slab bedrock erosion has been observed during several transport events. We discuss the relation between hydraulics, bedload transport, resulting pressure forces on the stone slabs and erosion rates. The aim of the study is the derivation of an empirical process law for fluvial bedrock erosion driven by moving sediment particles.

Plasma x-ray radiation source.

PubMed

Popkov, N F; Kargin, V I; Ryaslov, E A; Pikar', A S

1995-01-01

This paper gives the results of studies on a plasma x-ray source, which enables one to obtain a 2.5-krad radiation dose per pulse over an area of 100 cm2 in the quantum energy range from 20 to 500 keV. Pulse duration is 100 ns. Spectral radiation distributions from a diode under various operation conditions of a plasma are obtained. A Marx generator served as an initial energy source of 120 kJ with a discharge time of T/4 = 10-6 s. A short electromagnetic pulse (10-7 s) was shaped using plasma erosion opening switches.

Bragg scattering of electromagnetic waves by microwave-produced plasma layers

NASA Technical Reports Server (NTRS)

Kuo, S. P.; Zhang, Y. S.

1990-01-01

A set of parallel plasma layers is generated by two intersecting microwave pulses in a chamber containing dry air at a pressure comparable to the upper atmosphere. The dependencies of breakdown conditions on the pressure and pulse length are examined. The results are shown to be consistent with the appearance of tail erosion of the microwave pulse caused by air breakdown. A Bragg scattering experiment, using the plasma layers as a Bragg reflector, is then performed. Both time domain and frequency domain measurements of wave scattering are conducted. The experimental results are found to agree very well with the theory.

Rail accelerator research at Lewis Research Center

NASA Technical Reports Server (NTRS)

Kerslake, W. R.; Cybyk, B. Z.

1982-01-01

A rail accelerator was chosen for study as an electromagnetic space propulsion device because of its simplicity and existing technology base. The results of a mission feasibility study using a large rail accelerator for direct launch of ton-size payloads from the Earth's surface to space, and the results of initial tests with a small, laboratory rail accelerator are presented. The laboratory rail accelerator has a bore of 3 by 3 mm and has accelerated 60 mg projectiles to velocities of 300 to 1000 m/s. Rail materials of Cu, W, and Mo were tested for efficiency and erosion rate.

Development of an inexpensive optical method for studies of dental erosion process in vitro

NASA Astrophysics Data System (ADS)

Nasution, A. M. T.; Noerjanto, B.; Triwanto, L.

2008-09-01

Teeth have important roles in digestion of food, supporting the facial-structure, as well as in articulation of speech. Abnormality in teeth structure can be initiated by an erosion process due to diet or beverages consumption that lead to destruction which affect their functionality. Research to study the erosion processes that lead to teeth's abnormality is important in order to be used as a care and prevention purpose. Accurate measurement methods would be necessary as a research tool, in order to be capable for quantifying dental destruction's degree. In this work an inexpensive optical method as tool to study dental erosion process is developed. It is based on extraction the parameters from the 3D dental visual information. The 3D visual image is obtained from reconstruction of multiple lateral projection of 2D images that captured from many angles. Using a simple motor stepper and a pocket digital camera, sequence of multi-projection 2D images of premolar tooth is obtained. This images are then reconstructed to produce a 3D image, which is useful for quantifying related dental erosion parameters. The quantification process is obtained from the shrinkage of dental volume as well as surface properties due to erosion process. Results of quantification is correlated to the ones of dissolved calcium atom which released from the tooth using atomic absorption spectrometry. This proposed method would be useful as visualization tool in many engineering, dentistry, and medical research. It would be useful also for the educational purposes.

Fire effects on rangeland hydrology and erosion in a steep sagebrush-dominated landscape

Treesearch

Frederick B. Pierson; Peter R. Robichaud; Corey A. Moffet; Kenneth E. Spaeth; Stuart P. Hardegree; Patrick E. Clark; C. Jason Williams

2008-01-01

Post-fire runoff and erosion from wildlands has been well researched, but few studies have researched the degree of control exerted by fire on rangeland hydrology and erosion processes. Furthermore, the spatial continuity and temporal persistence of wildfire impacts on rangeland hydrology and erosion are not well understood. Small-plot rainfall and concentrated flow...

Comparison of WEPP and APEX runoff and erosion prediction at field scale in Goodwater Creek Experimental Watershed

USDA-ARS?s Scientific Manuscript database

The Water Erosion Prediction Project (WEPP) and the Agricultural Policy/Environmental eXtender (APEX) are process-based models that can predict spatial and temporal distributions of erosion for hillslopes and watersheds. This study applies the WEPP model to predict runoff and erosion for a 35-ha fie...

Implementation of channel-routing routines in the Water Erosion Prediction Project (WEPP) model

Treesearch

Li Wang; Joan Q. Wu; William J. Elliott; Shuhui Dun; Sergey Lapin; Fritz R. Fiedler; Dennis C. Flanagan

2010-01-01

The Water Erosion Prediction Project (WEPP) model is a process-based, continuous-simulation, watershed hydrology and erosion model. It is an important tool for water erosion simulation owing to its unique functionality in representing diverse landuse and management conditions. Its applicability is limited to relatively small watersheds since its current version does...

Modeling erosion on steep sagebrush rangeland before and after prescribed fire

Treesearch

Corey A. Moffet; Frederick B. Pierson; Kenneth E. Spaeth

2007-01-01

Fire in sagebrush rangelands significantly alters canopy cover, ground cover, and soil properties that influence runoff and erosion processes. Runoff is generated more quickly and a larger volume of runoff is produced following prescribed fire. The result is increased risk of severe erosion and downstream flooding. The Water Erosion Prediction Project (WEPP), developed...

Microhardness evaluation of silorane and methacrylate composites submitted to erosion and abrasion processes

PubMed Central

Gazola, Eloá Aguiar; Rego, Marcos Augusto; Brandt, William Cunha; D’Arce, Maria Beatriz Freitas; Liporoni, Priscila Christiane Suzy

2015-01-01

Abstract Objective: The aim of this study was to evaluate the Knoop hardness number (KHN) of methacrylate (MC) and silorane (SC) composites after being submitted to erosion and abrasion processes. Material and methods: Forty samples were made with each composite: MC and SC. The samples were divided into eight groups (n = 10) according to the type of composite (G1–G4, MC; G5–G8, SC) and the beverages involved in the erosion process (G1 and G5 – Control (C), without erosion, with abrasion; G2 and G6 – Orange Juice (OJ), abrasion; G3 and G7 – Smirnoff Ice® (SI), abrasion; G4 and G8 – Gatorade® (GA), abrasion). The KHN test was performed 24 h after the last cycle of erosion/abrasion. Results: The MC groups showed smaller KHN values for the SI group (p < 0.05) when compared to the Control and OJ groups; however, for the SC groups, no differences were found (p > 0.05). Conclusion: Methacrylate composite when submitted to acidic beverages erosive challenge combined with abrasive process might alter its surface microhardness. However, the beverages used in the present study were not able to interfere in silorane composite surface microhardness. PMID:28642903

Multi-agent gully processes: Evidence from the Monaro Volcanic Province, Australia and in Terra Cimmeria, Mars

NASA Astrophysics Data System (ADS)

Hobbs, S. W.; Paull, D. J.; Clarke, J. D. A.; Roach, Ian C.

2016-03-01

Comparison of the similarities and differences between terrestrial and Martian hillside gullies promotes understanding of how surface processes operate on both planets. Here we tested the viability of subsurface flow of water as a process affecting gully evolution. We compared gullies within the Monaro Volcanic Province near Cooma, New South Wales, Australia, to gullies possessing strong structural control near Gasa Crater, Terra Cimmeria, Mars. Although cursory examination of the Monaro gullies initially suggested strong evidence for aquifer erosion, detailed field surveys showed the evidence to be ambiguous. Instead a complex regime of erosion dependent on multiple conditions and processes such as local geology, surface runoff, dry mass wasting, and animal activity emerged. We found the morphology of gullies near Gasa Crater to be consistent with erosion caused by liquid water, while also being heavily influenced by the local environment, including slope and geology. Additionally, erosion at the Martian site was not consistent with evidence of subsequent, smaller scale erosion and channel modification by dry mass wasting. Local conditions thus play an important role in gully evolution, further highlighting that processes forming Martian gullies may be more diverse than initially thought.

The Role of Vegetation Cover in Interactions between Climate and Erosion

NASA Astrophysics Data System (ADS)

Schildgen, T. F.; Torres-Acosta, V.; Düsing, W.; Garcin, Y.; Strecker, M. R.

2016-12-01

Interactions between tectonics, climate and erosion during mountain building are often considered to include a positive feedback between precipitation and erosion, with the onset of orographic rainfall inducing greater erosion, which in turn may drive faster deformation. Here, we consider two different case studies that explore specifically the relationship between climate and erosion. Within the Kenya Rift of East Africa, spatial variations in 10Be derived erosion rates show no clear dependency on yearly precipitation. Instead, we find that the data fall into two categories. In areas that are sparsely vegetated, erosion rates increase rapidly with slope, whereas in areas that are densely vegetated, erosion rates increase slowly with slope. These data imply that vegetation cover plays a major role in stabilizing hillslopes. From these results, we hypothesize that in a sparsely vegetated region, the onset of greater precipitation will lead to faster erosion, but only until vegetation becomes denser, after which erosion rates will strongly decrease. Initial results from an ongoing study that reconstruct paleo-erosion rates from a sedimentary archive support this hypothesis. Hence, we infer that in this region, vegetation cover acts as a negative feedback in the interactions between climate and erosion. Compared to East Africa, we find a very different relationship between climate and 10Be derived erosion rates in the Toro intermontane basin in NW Argentina. There, the fastest erosion rates occur in the wettest areas with dense vegetation cover, implying a positive feedback between increased precipitation and erosion rates. Also, paleo-erosion rates from the nearby Humahuaca Basin derived from fluvial terraces point to faster erosion during wetter periods in the past. In this region, the stabilizing effects of vegetation cover may be muted. Ultimately, whether increased precipitation leads to faster or slower erosion could hinge on the dominant erosion processes. Along the steep slopes of NW Argentina, landslides are the dominant process, and appear to be minimally affected by vegetation cover. In contrast, the more gentle hillslopes in East Africa appear to be stabilized by a dense vegetation cover.

Relativistically strong electromagnetic radiation in a plasma

DOE Office of Scientific and Technical Information (OSTI.GOV)

Bulanov, S. V., E-mail: svbulanov@gmail.com, E-mail: bulanov.sergei@jaea.go.jp; Esirkepov, T. Zh.; Kando, M.

Physical processes in a plasma under the action of relativistically strong electromagnetic waves generated by high-power lasers have been briefly reviewed. These processes are of interest in view of the development of new methods for acceleration of charged particles, creation of sources of bright hard electromagnetic radiation, and investigation of macroscopic quantum-electrodynamical processes. Attention is focused on nonlinear waves in a laser plasma for the creation of compact electron accelerators. The acceleration of plasma bunches by the radiation pressure of light is the most efficient regime of ion acceleration. Coherent hard electromagnetic radiation in the relativistic plasma is generated inmore » the form of higher harmonics and/or electromagnetic pulses, which are compressed and intensified after reflection from relativistic mirrors created by nonlinear waves. In the limit of extremely strong electromagnetic waves, radiation friction, which accompanies the conversion of radiation from the optical range to the gamma range, fundamentally changes the behavior of the plasma. This process is accompanied by the production of electron–positron pairs, which is described within quantum electrodynamics theory.« less

Apparatus and method for enhanced chemical processing in high pressure and atmospheric plasmas produced by high frequency electromagnetic waves

DOEpatents

Efthimion, Philip C.; Helfritch, Dennis J.

1989-11-28

An apparatus and method for creating high temperature plasmas for enhanced chemical processing of gaseous fluids, toxic chemicals, and the like, at a wide range of pressures, especially at atmospheric and high pressures includes an electro-magnetic resonator cavity, preferably a reentrant cavity, and a wave guiding structure which connects an electro-magnetic source to the cavity. The cavity includes an intake port and an exhaust port, each having apertures in the conductive walls of the cavity sufficient for the intake of the gaseous fluids and for the discharge of the processed gaseous fluids. The apertures are sufficiently small to prevent the leakage of the electro-magnetic radiation from the cavity. Gaseous fluid flowing from the direction of the electro-magnetic source through the guiding wave structure and into the cavity acts on the plasma to push it away from the guiding wave structure and the electro-magnetic source. The gaseous fluid flow confines the high temperature plasma inside the cavity and allows complete chemical processing of the gaseous fluids at a wide range of pressures.

Thermal erosion of a permafrost coastline: Improving process-based models using time-lapse photography

USGS Publications Warehouse

Wobus, C.; Anderson, R.; Overeem, I.; Matell, N.; Clow, G.; Urban, F.

2011-01-01

Coastal erosion rates locally exceeding 30 m y-1 have been documented along Alaska's Beaufort Sea coastline, and a number of studies suggest that these erosion rates have accelerated as a result of climate change. However, a lack of direct observational evidence has limited our progress in quantifying the specific processes that connect climate change to coastal erosion rates in the Arctic. In particular, while longer ice-free periods are likely to lead to both warmer surface waters and longer fetch, the relative roles of thermal and mechanical (wave) erosion in driving coastal retreat have not been comprehensively quantified. We focus on a permafrost coastline in the northern National Petroleum Reserve-Alaska (NPR-A), where coastal erosion rates have averaged 10-15 m y-1 over two years of direct monitoring. We take advantage of these extraordinary rates of coastal erosion to observe and quantify coastal erosion directly via time-lapse photography in combination with meteorological observations. Our observations indicate that the erosion of these bluffs is largely thermally driven, but that surface winds play a crucial role in exposing the frozen bluffs to the radiatively warmed seawater that drives melting of interstitial ice. To first order, erosion in this setting can be modeled using formulations developed to describe iceberg deterioration in the open ocean. These simple models provide a conceptual framework for evaluating how climate-induced changes in thermal and wave energy might influence future erosion rates in this setting.

Modeling soil erosion processes on a hillslope with dendritic rill network

NASA Astrophysics Data System (ADS)

Chen, L.; Wu, S.

2017-12-01

The effect of planform of dendritic rill network on hillslope rainfall-runoff and soil erosion processes was usually neglected in previous studies, which, however, could dramatically alter the mechanisms of the hydrologic and geomorphic processes. In the present study, the interrill areas were treated as two-dimensional (2D), while the complicated rill network was represented by a piecewise one-dimensional (1D) rill retaining the characteristic of rill network (the rill density and average rill deflection angle). Based on a 2D diffusive wave overland flow model, and the WEPP erosion theory, the 1D and 2D coupling model was developed to simulate the hillslope runoff and soil erosion on both the interrill areas and the representative rill. The rill number and rill inclination angle were introduced in the model to reflect the actual rill density, rill length, rill slope gradient, and confluence processes from the interrill areas to the rill. The excess rainfall and sediment load coming into the representative rill were not only from the two lateral interrill areas but also from the upstream interrill areas. The model was successfully tested against experimental data obtained from a hillslope with complicated rill network. Comparison of the results obtained from the present model with WEPP indicates that WEPP calculated the hillslope runoff yield accurately but overestimated the amount of rill erosion. Moreover, the effects of rill deflection angle and rill number distribution on both interrill and rill erosions were examined and found neglecting the planar characteristic of rill network has a considerable impact on soil erosion prediction. It is expected that the model can extend the scope of WEPP application and predict more accurately the runoff and erosion yield on a hillslope with complicated rill network.

Qualitative comparison of soil erosion, runoff and infiltration coefficients using small portable rainfall simulators in Germany, Spain and France

NASA Astrophysics Data System (ADS)

Rodrigo Comino, Jesús; Iserloh, Thomas; Morvan, Xavier; Malam Issa, Oumarou; Naisse, Christophe; Keesstra, Saskia; Cerdà, Artemi; Prosdocimi, Massimo; Arnáez, José; Lasanta, Teodoro; Concepción Ramos, María; José Marqués, María; Ruiz Colmenero, Marta; Bienes, Ramón; Damián Ruiz Sinoga, José; Seeger, Manuel; Ries, Johannes B.

2016-04-01

Small portable rainfall simulators are considered as a useful tool to analyze soil erosion processes in cultivated lands. European research groups of Spain (Valencia, Málaga, Lleida, Madrid and La Rioja), France (Reims) or Germany (Trier) have used different rainfall simulators (varying in drop size distribution and fall velocities, kinetic energy, plot forms and sizes, and field of application)to study soil loss, surface flow, runoff and infiltration coefficients in different experimental plots (Valencia, Montes de Málaga, Penedès, Campo Real and La Rioja in Spain, Champagne in France and Mosel-Ruwer valley in Germany). The measurements and experiments developed by these research teams give an overview of the variety in the methodologies with rainfall simulations in studying the problem of soil erosion and describing the erosion features in different climatic environments, management practices and soil types. The aim of this study is: i) to investigate where, how and why researchers from different wine-growing regions applied rainfall simulations with successful results as a tool to measure soil erosion processes; ii) to make a qualitative comparison about the general soil erosion processes in European terroirs; iii) to demonstrate the importance of the development a standard method for soil erosion processes in vineyards, using rainfall simulators; iv) and to analyze the key factors that should be taken into account to carry out rainfall simulations. The rainfall simulations in all cases allowed knowing the infiltration capacity and the susceptibility of the soil to be detached and to generate sediment loads to runoff. Despite using small plots, the experiments were useful to analyze the influence of soil cover to reduce soil erosion and to make comparison between different locations or the influence of different soil characteristics.

Manufacturing of hybrid aluminum copper joints by electromagnetic pulse welding - Identification of quantitative process windows

NASA Astrophysics Data System (ADS)

Psyk, Verena; Scheffler, Christian; Linnemann, Maik; Landgrebe, Dirk

2017-10-01

Compared to conventional joining techniques, electromagnetic pulse welding offers important advantages especially when it comes to dissimilar material connections as e.g. copper aluminum welds. However, due to missing guidelines and tools for process design, the process has not been widely implemented in industrial production, yet. In order to contribute to overcoming this obstacle, a combined numerical and experimental process analysis for electromagnetic pulse welding of Cu-DHP and EN AW-1050 was carried out and the results were consolidated in a quantitative collision parameter based process window.

[Assessment of the impacts of soil erosion on water environment based on the integration of soil erosion process and landscape pattern].

PubMed

Liu, Yu; Wu, Bing-Fang; Zeng, Yuan; Zhang, Lei

2013-09-01

The integration of the effects of landscape pattern to the assessment of the impacts of soil erosion on eco-environmental is of practical significance in methodological prospect, being able to provide an approach for identifying water body's sediment source area, assessing the potential risks of sediment export of on-site soil erosion to the target water body, and evaluating the capacity of regional landscape pattern in preventing soil loss. In this paper, the RUSLE model was applied to simulate the on-site soil erosion rate. With the consideration of the soil retention potential of vegetation cover and topography, a quantitative assessment was conducted on the impacts of soil erosion in the water source region of the middle route for South-to-North Water Transfer Project on rivers and reservoirs by delineating landscape pattern at point (or cell) scale and sub-watershed level. At point (or grid cell) scale, the index of soil erosion impact intensity (I) was developed as an indicator of the potential risk of sediment export to the water bodies. At sub-watershed level, the landscape leakiness index (LI) was employed to indicate the sediment retention capacity of a given landscape pattern. The results revealed that integrating the information of landscape pattern and the indices of soil erosion process could spatially effectively reflect the impact intensity of in situ soil erosion on water bodies. The LI was significantly exponentially correlated to the mean sediment retention capacity of landscape and the mean vegetation coverage of watershed, and the sediment yield at sub-watershed scale was significantly correlated to the LI in an exponential regression. It could be concluded that the approach of delineating landscape pattern based on soil erosion process and the integration of the information of landscape pattern with its soil retention potential could provide a new approach for the risk evaluation of soil erosion.

Interaction between attrition,abrasion and erosion in tooth wear.

PubMed

Addy, M; Shellis, R P

2006-01-01

Tooth wear is the result of three processes: abrasion (wear produced by interaction between teeth and other materials), attrition (wear through tooth-tooth contact) and erosion (dissolution of hard tissue by acidic substances). A further process (abfraction) might potentiate wear by abrasion and/or erosion. Both clinical and experimental observations show that individual wear mechanisms rarely act alone but interact with each other. The most important interaction is the potentiation of abrasion by erosive damage to the dental hard tissues. This interaction seems to be the major factor in occlusal and cervical wear. The available evidence seems insufficient to establish whether abfraction is an important contributor to tooth wear in vivo. Saliva can modulate erosive/abrasive tooth wear through formation of pellicle and by remineralisation but cannot prevent it.

A review of concentrated flow erosion processes on rangelands: fundamental understanding and knowledge gaps

USDA-ARS?s Scientific Manuscript database

Concentrated flow erosion processes are distinguished from splash and sheetflow processes in their enhanced ability to mobilize and transport large amounts of soil, water and dissolved elements. On rangelands, soil, nutrients and water are scarce and only narrow margins of resource losses are tolera...

Process-Based Modeling of Upland Erosion and Salt Load in the Upper Colorado River Basin

USDA-ARS?s Scientific Manuscript database

Hillslope runoff and soil erosion processes are indicators of sustainability in rangeland ecosystem due to their control on resource mobility. Hillslope processes are dominant contributors to sediment delivery on semi-arid rangeland watersheds. The influence of vegetation on hillslope runoff and sed...

Methods for monitoring the effects of grazing management on bank erosion and channel morphology, Fever River, Pioneer Farm, Wisconsin, 2004

USGS Publications Warehouse

Peppler, Marie C.; Fitzpatrick, Faith A.

2005-01-01

Bank erosion is a natural process that occurs in meandering streams (Leopold and others, 1964); however, in the Midwestern United States, historical and present agricultural activities in uplands, riparian areas, and channels have increased erosion (Waters, 1995; Lyons and others, 2000; Simon and Rinaldi, 2000; and Knox, 2001). Reducing streambank erosion is important because sediment carried by streams has adverse environmental effects; for example, sediment carried by streams is a major source of phosphorus (Waters, 1995). Continuous cattle grazing in riparian areas may increase local erosion processes in a meandering stream by removal or trampling of bank vegetation, which in turn affects channel morphology, water chemistry, and fish and aquatic-insect habitat (Kauffman and Krueger, 1984; Fitch and Adams, 1998). However, studies of livestock exclusion from riparian corridors have shown mixed results in reducing bank erosion (Trimble, 1994; Sarr, 2002). Some studies have shown reduced bank erosion after row-cropped or continuously grazed riparian areas are converted to managed grazing (see inset box) (Lyons and others, 2000; Sovell and others, 2000; and Zaimes and others, 2004).

Universal approach to analysis of cavitation and liquid-impingement erosion data

NASA Technical Reports Server (NTRS)

Rao, P. V.; Young, S. G.

1982-01-01

Cavitation erosion experimental data was analyzed by using normalization and curve-fitting techniques. Data were taken from experiments on several materials tested in both a rotating disk device and a magnetostriction apparatus. Cumulative average volume loss rate and time data were normalized relative to the peak erosion rate and the time to peak erosion rate, respectively. From this process a universal approach was derived that can include data on specific materials from different test devices for liquid impingement and cavitation erosion studies.

What Should a Restored River Look Like? (Invited)

NASA Astrophysics Data System (ADS)

Florsheim, J. L.; Chin, A.

2010-12-01

Removal of infrastructure such as dams, levees, and erosion control structures is a promising approach toward restoring river system connectivity, processes, and ecology. Significant management challenges exist, however, related to removal of such structures that have already transformed riparian processes or societal perceptions. Here, we consider the effects of bank erosion infrastructure versus the benefits of allowing channel banks to erode in order to address the question: what should a restored river look like? The extent of channel bank infrastructure globally is unknown; nevertheless, it dominates rivers in most urban areas and is growing in rural areas as small projects merge and creeks and rivers are progressively channelized. Bank erosion control structures are usually installed to limit land loss and to reduce associated hazards. Structures are sometimes themselves considered restoration under the assumption that sediment erosion is bad for ecosystems. Geomorphic and ecological effects of bank erosion control structures are well understood, however, and include loss of sediment sources, bank substrate, dynamic geomorphic processes, and riparian habitat. Thus, a rationale for allowing eroding banks in restored rivers is as follows: 1) bank erosion processes are a component of system-scale channel adjustment needed to accommodate variable hydrology and sediment loads and to promote long-term stability; 2) bank erosion is a source of coarse and fine sediment to channels needed to maintain downstream bed elevations and topographic heterogeneity; and 3) bank erosion is a component of river migration, a process that promotes riparian vegetation succession and provides large woody material and morphologic diversity required to sustain habitat and riparian biodiversity. When structures that were originally intended to control or manage dynamic natural processes such as flooding and erosion are removed, not surprisingly, a return to dynamic processes may cause economic and cultural impacts to a public that that has often encroached on land too close to the riparian zone to accommodate the magnitude of these processes. Thus, to accomplish river system restoration in rural areas, science is needed to inform policy-makers and managers about the multidimensional physical extent of the riparian zone required for restoration of bio-hydro-geomorphic processes that promote functioning ecology. In urban areas, river system restoration requires a long-term dedication to education, fund raising for land acquisition, infrastructure removal, as well as planning, new riparian policy, governance, and management that takes into account the value and dynamic nature of river processes. So, what should a restored river look like? The banks of the restored river might be thought of as an aquatic-terrestrial ecotone that is longitudinally, laterally, and vertically connected to adjacent ecosystems. This ecotone includes a non-stationary mosaic of bare ground, irregular topography, live vegetation of diverse ages, sizes, and type, dead woody material, and diverse fauna.

Electromagnetic Radiation Disturbed the Photosynthesis of Microcystis aeruginosa at the Proteomics Level.

PubMed

Tang, Chao; Yang, Chuanjun; Yu, Hui; Tian, Shen; Huang, Xiaomei; Wang, Weiyi; Cai, Peng

2018-01-11

Photosynthesis of Microcystis aeruginosa under Electromagnetic Radiation (1.8 GHz, 40 V/m) was studied by using the proteomics. A total of 30 differentially expressed proteins, including 15 up-regulated and 15 down-regulated proteins, were obtained in this study. The differentially expressed proteins were significantly enriched in the photosynthesis pathway, in which the protein expression levels of photosystems II cytochrome b559 α subunit, cytochrome C550, PsbY, and F-type ATP synthase (a, b) decreased. Our results indicated that electromagnetic radiation altered the photosynthesis-related protein expression levels, and aimed at the function of photosynthetic pigments, photosystems II potential activity, photosynthetic electron transport process, and photosynthetic phosphorylation process of M. aeruginosa. Based on the above evidence, that photoreaction system may be deduced as a target of electromagnetic radiation on the photosynthesis in cyanobacteria; the photoreaction system of cyanobacteria is a hypothetical "shared target effector" that responds to light and electromagnetic radiation; moreover, electromagnetic radiation does not act on the functional proteins themselves but their expression processes.

Conversion of electromagnetic energy in Z-pinch process of single planar wire arrays at 1.5 MA

DOE Office of Scientific and Technical Information (OSTI.GOV)

Liangping, Wang; Mo, Li; Juanjuan, Han

The electromagnetic energy conversion in the Z-pinch process of single planar wire arrays was studied on Qiangguang generator (1.5 MA, 100 ns). Electrical diagnostics were established to monitor the voltage of the cathode-anode gap and the load current for calculating the electromagnetic energy. Lumped-element circuit model of wire arrays was employed to analyze the electromagnetic energy conversion. Inductance as well as resistance of a wire array during the Z-pinch process was also investigated. Experimental data indicate that the electromagnetic energy is mainly converted to magnetic energy and kinetic energy and ohmic heating energy can be neglected before the final stagnation. Themore » kinetic energy can be responsible for the x-ray radiation before the peak power. After the stagnation, the electromagnetic energy coupled by the load continues increasing and the resistance of the load achieves its maximum of 0.6–1.0 Ω in about 10–20 ns.« less

Experimental and numerical studies on laser-based powder deposition of slurry erosion resistant materials

NASA Astrophysics Data System (ADS)

Balu, Prabu

Slurry erosion (the removal of material caused by the randomly moving high velocity liquid-solid particle mixture) is a serious issue in crude oil drilling, mining, turbines, rocket nozzles, pumps, and boiler tubes that causes excessive downtime and high operating costs as a result of premature part failure. The goal of this research is to enhance the service life of high-value components subjected to slurry erosion by utilizing the concept of functionally graded metal-ceramic composite material (FGMCCM) in which the favorable properties of metal (toughness, ductility, etc.) and ceramic (hardness) are tailored smoothly to improve erosion resistance. Among the potential manufacturing processes, such as the laser-based powder deposition (LBPD), the plasma transferred arc (PTA), and the thermal spray the LBPD process offers good composition and microstructure control with a high deposition rate in producing the FGMCCM. This research focuses on the development of nickel-tungsten carbide (Ni-WC) based FGMCCM using the LBPD process for applications the above mentioned. The LBPD of Ni-WC involves the introduction of Ni and WC powder particle by an inert gas into the laser-formed molten pool at the substrate via nozzles. The LBPD of Ni-WC includes complex multi-physical interactions between the laser beam, Ni-WC powder, substrate, and carrier and shielding gases that are governed by a number of process variables such as laser power, scanning speed, and powder flow rate. In order to develop the best Ni-WC based slurry erosion resistant material using the LBPD process, the following challenges associated with the fabrication and the performance evaluation need to be addressed: 1) flow behavior of the Ni-WC powder and its interaction with the laser, 2) the effect of the process variables, the material compositions, and the thermo-physical properties on thermal cycles, temperature gradient, cooling rate, and residual stress formation within the material and the subsequent cracking issue, and 3) the effect of composition and composition gradient of Ni and WC on the slurry erosion resistance over a wide range of erosion conditions. This thesis presents a set of numerical and experimental methods in order to address the challenges mentioned above. A three-dimensional (3-D) computational fluid dynamics (CFD) based powder flow model and three vision based techniques were developed in order to visualize the process of feeding the Ni-WC powder in the LBPD process. The results provide the guidelines for efficiently feeding the Ni-WC composite powder into the laser-formed molten pool. The finite element (FE) based experimentally verified 3-D thermal and thermo-mechanical models are developed in order to understand the thermal and stress evolutions in Ni-WC composite material during the LBPD process. The models address the effect of the process variables, preheating temperature, and different mass fractions of WC in Ni on thermal cycles and stress distributions within the deposited material. The slurry erosion behavior of the single and multilayered deposits of Ni-WC composite material produced by the LBPD process is investigated using an accelerated slurry erosion testing machine and a 3-D FE dynamic model. The verified model is used to identify the appropriate composition and composition gradient of Ni-WC composite material required to achieve erosion resistance over a wide range of erosion conditions.

Scales and erosion

USDA-ARS?s Scientific Manuscript database

There is a need to develop scale explicit understanding of erosion to overcome existing conceptual and methodological flaws in our modelling methods currently applied to understand the process of erosion, transport and deposition at the catchment scale. These models need to be based on a sound under...

Quantifying and modeling soil erosion and sediment export from construction sites in southern California

NASA Astrophysics Data System (ADS)

Wernet, A. K.; Beighley, R. E.

2006-12-01

Soil erosion is a power process that continuously alters the Earth's landscape. Human activities, such as construction and agricultural practices, and natural events, such as forest fires and landslides, disturb the landscape and intensify erosion processes leading to sudden increases in runoff sediment concentrations and degraded stream water quality. Understanding soil erosion and sediment transport processes is of great importance to researchers and practicing engineers, who routinely use models to predict soil erosion and sediment movement for varied land use and climate change scenarios. However, existing erosion models are limited in their applicability to constructions sites which have highly variable soil conditions (density, moisture, surface roughness, and best management practices) that change often in both space and time. The goal of this research is to improve the understanding, predictive capabilities and integration of treatment methodologies for controlling soil erosion and sediment export from construction sites. This research combines modeling with field monitoring and laboratory experiments to quantify: (a) spatial and temporal distribution of soil conditions on construction sites, (b) soil erosion due to event rainfall, and (c) potential offsite discharge of sediment with and without treatment practices. Field sites in southern California were selected to monitor the effects of common construction activities (ex., cut/fill, grading, foundations, roads) on soil conditions and sediment discharge. Laboratory experiments were performed in the Soil Erosion Research Laboratory (SERL), part of the Civil and Environmental Engineering department at San Diego State University, to quantify the impact of individual factors leading to sediment export. SERL experiments utilize a 3-m by 10-m tilting soil bed with soil depths up to 1 m, slopes ranging from 0 to 50 percent, and rainfall rates up to 150 mm/hr (6 in/hr). Preliminary modeling, field and laboratory results are presented.

Probabilistic soil erosion modeling using the Erosion Risk Management Tool (ERMIT) after wildfires

Treesearch

P. R. Robichaud; W. J. Elliot; J. W. Wagenbrenner

2011-01-01

The decision of whether or not to apply post-fire hillslope erosion mitigation treatments, and if so, where these treatments are most needed, is a multi-step process. Land managers must assess the risk of damaging runoff and sediment delivery events occurring on the unrecovered burned hillslope. We developed the Erosion Risk Management Tool (ERMiT) to address this need...

Water erosion susceptibility mapping by applying Stochastic Gradient Treeboost to the Imera Meridionale River Basin (Sicily, Italy)

NASA Astrophysics Data System (ADS)

Angileri, Silvia Eleonora; Conoscenti, Christian; Hochschild, Volker; Märker, Michael; Rotigliano, Edoardo; Agnesi, Valerio

2016-06-01

Soil erosion by water constitutes a serious problem affecting various countries. In the last few years, a number of studies have adopted statistical approaches for erosion susceptibility zonation. In this study, the Stochastic Gradient Treeboost (SGT) was tested as a multivariate statistical tool for exploring, analyzing and predicting the spatial occurrence of rill-interrill erosion and gully erosion. This technique implements the stochastic gradient boosting algorithm with a tree-based method. The study area is a 9.5 km2 river catchment located in central-northern Sicily (Italy), where water erosion processes are prevalent, and affect the agricultural productivity of local communities. In order to model soil erosion by water, the spatial distribution of landforms due to rill-interrill and gully erosion was mapped and 12 environmental variables were selected as predictors. Four calibration and four validation subsets were obtained by randomly extracting sets of negative cases, both for rill-interrill erosion and gully erosion models. The results of validation, based on receiving operating characteristic (ROC) curves, showed excellent to outstanding accuracies of the models, and thus a high prediction skill. Moreover, SGT allowed us to explore the relationships between erosion landforms and predictors. A different suite of predictor variables was found to be important for the two models. Elevation, aspect, landform classification and land-use are the main controlling factors for rill-interrill erosion, whilst the stream power index, plan curvature and the topographic wetness index were the most important independent variables for gullies. Finally, an ROC plot analysis made it possible to define a threshold value to classify cells according to the presence/absence of the two erosion processes. Hence, by heuristically combining the resulting rill-interrill erosion and gully erosion susceptibility maps, an integrated water erosion susceptibility map was created. The adopted method offers the advantages of an objective and repeatable procedure, whose result is useful for local administrators to identify the areas that are most susceptible to water erosion and best allocate resources for soil conservation strategies.

Effects of Bedrock Landsliding on Cosmogenically Determined Erosion Rates

NASA Technical Reports Server (NTRS)

Niemi, Nathan; Oskin, Mike; Burbank, Douglas; Heimsath, Arjun

2005-01-01

The successful quantification of long-term erosion rates underpins our understanding of landscape. formation, the topographic evolution of mountain ranges, and the mass balance within active orogens. The measurement of in situ-produced cosmogenic radionuclides (CRNs) in fluvial and alluvial sediments is perhaps the method with the greatest ability to provide such long-term erosion rates. In active orogens, however, deep-seated bedrock landsliding is an important erosional process, the effect of which on CRN-derived erosion rates is largely unquantified. We present a numerical simulation of cosmogenic nuclide production and distribution in landslide-dominated catchments to address the effect of bedrock landsliding on cosmogenic erosion rates in actively eroding landscapes. Results of the simulation indicate that the temporal stability of erosion rates determined from CRN concentrations in sediment decreases with increased ratios of landsliding to sediment detachment rates within a given catchment area, and that larger catchment areas must be sampled with increased frequency of landsliding in order to accurately evaluate long-term erosion rates. In addition, results of this simulation suggest that sediment sampling for CRNs is the appropriate method for determining long-term erosion rates in regions dominated by mass-wasting processes, while bedrock surface sampling for CRNs is generally an ineffective means of determining long-term erosion rates. Response times of CRN concentrations to changes in erosion rate indicate that climatically driven cycles of erosion may be detected relatively quickly after such changes occur, but that complete equilibration of CRN concentrations to new erosional conditions may take tens of thousands of years. Simulation results of CRN erosion rates are compared with a new, rich dataset of CRN concentrations from the Nepalese Himalaya, supporting conclusions drawn from the simulation.

Challenges in soil erosion research and prediction model development

USDA-ARS?s Scientific Manuscript database

Quantification of soil erosion has been traditionally considered as a surface hydrologic process with equations for soil detachment and sediment transport derived from the mechanics and hydraulics of the rainfall and surface flow. Under the current erosion modeling framework, the soil has a constant...

A fluidized bed technique for estimating soil critical shear stress

USDA-ARS?s Scientific Manuscript database

Soil erosion models, depending on how they are formulated, always have erodibilitiy parameters in the erosion equations. For a process-based model like the Water Erosion Prediction Project (WEPP) model, the erodibility parameters include rill and interrill erodibility and critical shear stress. Thes...

Reduction in soil aggregate size distribution due to wind erosion

NASA Astrophysics Data System (ADS)

Swet, Nitzan; Katra, Itzhak

2017-04-01

Soil erosion process by wind causes emission of fine soil particles, and thus alters the topsoil's properties, fertility, and erodibility. Topsoil resistance to erosion depends on its physicochemical properties, especially on the soil aggregation. Although the key role of aggregates in soil erodibility, quantitative information on the relations between soil aggregate size distribution (ASD) and erosion is still lucking. This study focuses on ASD analyses before and after soil erosion by wind. Wind tunnel experiments and soil analyses were conducted on semiarid loess topsoils with different initial conditions of aggregation. The results show that in all initial soil conditions saltation of sand particles caused the breakdown of macro-aggregates > 500 µm, resulting in increase of micro-aggregates (63-250 µm). The micro-aggregate production increases with the wind shear velocity (up to 0.61 m s-1) for soils with available macro-aggregates. The findings highlight dynamics in soil aggregation in response to erosion process, and therefore the significance of ASD in quantifying soil degradation and soil loss potential.

Impact of rainfall pattern on interrill erosion process

USDA-ARS?s Scientific Manuscript database

The impact of rainfall pattern on the interrill erosion process is not fully understood despite its importance. Systematic rainfall simulation experiments involving different rain intensities, stages, intensity sequences, and surface cover conditions were conducted to investigate the impacts of rain...

Effectiveness assessment of soil conservation measures in reducing soil erosion in Baiquan County of Northeastern China by using (137)Cs techniques.

PubMed

Zhang, Qing-Wen; Li, Yong

2014-05-01

Accelerated soil erosion is considered as a major land degradation process resulting in increased sediment production and sediment-associated nutrient inputs to the rivers. Over the last decade, several soil conservation programs for erosion control have been conducted throughout Northeastern China. Reliable information on soil erosion rates is an essential prerequisite to assess the effectiveness of soil conservation measures. A study was carried out in Baiquan County of Northeastern China to assess the effectiveness of soil conservation measures in reducing soil erosion using the (137)Cs tracer technique and related techniques. This study reports the use of (137)Cs measurements to quantify medium-term soil erosion rates in traditional slope farmland, contour cropping farmland and terrace farmland in the Dingjiagou catchment and the Xingsheng catchment of Baiquan County. The (137)Cs reference inventory of 2532 ± 670 Bq m(-2) was determined. Based on the principle of the (137)Cs tracer technique, soil erosion rates were estimated. The results showed that severe erosion on traditional slope farmland is the dominant soil erosion process in the area. The terrace measure reduced soil erosion rates by 16% for the entire slope. Typical net soil erosion rates are estimated to be 28.97 Mg per hectare per year for traditional slope farmland and 25.04 Mg per hectare per year for terrace farmland in the Dingjiagou catchment. In contrast to traditional slope farmland with a soil erosion rate of 34.65 Mg per hectare per year, contour cultivation reduced the soil erosion rate by 53% resulting in a soil erosion rate of 22.58 Mg per hectare per year in the Xingsheng catchment. These results indicated that soil losses can be controlled by changing tillage practices from the traditional slope farmland cultivation to the terrace or contour cultivation.

Design, construction, test and field support of a containerless payload package for rocket flight. [electromagnetic heating and confinement

NASA Technical Reports Server (NTRS)

1977-01-01

The performance of a device for electromagnetically heating and positioning containerless melts during space processing was evaluated during a 360 second 0-g suborbital sounding rocket flight. Components of the electromagnetic containerless processing package (ECPP), its operation, and interface with the rocket are described along with flight and qualification tests results.

Spectrum Management and Electromagnetic Environmental Effects (E3) Business Process

DTIC Science & Technology

2010-05-06

HAZARDS OF ELECTROMAGNETIC RADIATION TO ORDNANCE ( HERO ) SURVEY. XM11: IS THERE A CURRENT ELECTROMAGNETIC INTERFERENCE (EMI) SITE SURVEY. SM & EMI Navy...PERSONNEL (HERP) / FUEL (HERF) SURVEY. XM10: IS THERE A CURRENT HAZARDS OF ELECTROMAGNETIC RADIATION TO ORDNANCE ( HERO ) SURVEY. XM11...OF ALL KNOWN ELECTROMAGNETIC INTERFERENCE (EMI) FIXES INSTALLED ONE YEAR AFTER SURVEY COMPLETION. M05: OF ALL RADIATION HAZARDS

Changes in micro-relief during different water erosive stages of purple soil under simulated rainfall.

PubMed

Luo, Jian; Zheng, Zicheng; Li, Tingxuan; He, Shuqin

2018-02-22

This study investigated the variation characteristics of micro-topography during successive erosive stages of water erosion: splash erosion (SpE), sheet erosion (ShE), and rill erosion (RE). Micro-topography was quantified using surface elevation change, soil roughness (SR) and multifractal model. Results showed that the area of soil surface elevation decay increased gradually with the development of water erosion. With rainfall, the combined effects of the detachment by raindrop impact and the transport of runoff decreased SR, whereas rill erosion contributed to increase SR. With the increase in slope gradient, soil erosion area gradually decreased at the splash erosion stage. By contrast, soil erosion area initially decreased and then increased at the sheet and rill erosion stages. The width of the D q spectra (ΔD) values increased at the splash erosion stage and then decreased at the sheet and rill erosion stages on the 10° slope, opposite to that on the 15° slope. The ΔD values decreased with the evolution of water erosive stages on the 20° slope. The slope had an enhancing effect on the evolution of water erosion. In this study, we clarified the essence of micro-topography and laid a theoretical foundation for further understanding diverse hydrological processes.

Interrill Erodibility of P and C on conventially and organically farmed Devon soils

NASA Astrophysics Data System (ADS)

Kuhn, N. J.

2012-04-01

Soil erosion can have significant off-site effects on water quality and thus human and habitat health. Apart from sedimentation, the transfer of nutrients, both dissolved and particulate, is a major concern. The particulate transfer of nutrients from agricultural land can occur either by rill or interrill erosion. Rill erosion is non-selective and affects only a limited extent of agricultural land. Interrill processes such as crusting, splash and raindrop-impacted wash, on the other hand, act on all cropland and affect the quality of the water from all areas generating runoff. A significant amount of phosphorus (P) is contained in the surface soil layer transformed by interrill processes annually. In the EU, the P content of a crusted (2 mm) surface layer corresponds to 4 to 40 kg ha-1 of P on arable land (1.094 mil km2). Therefore, the role of interrill processes and erosion for regional nutrient cycling requires close attention. Interrill erosion is a complex phenomenon, involving the detachment, transport and deposition of soil particles by raindrop impacted flow. Resistance to interrill erosion varies between soils depending on their physical, chemical and mineralogical properties. In addition, significant changes in soil resistance to interrill erosion occur during storms as a result of changes in surface roughness, cohesion and particle size. As a consequence, erosion on interrill areas is selective, moving the most easily detached small and/or light soil particles which are often enriched in clay, P and organic C. Commonly, the risk of erosion associated with organically farmed soils is lower than those farmed in a conventional way. This is attributed to greater aggregate stability and thus greater infiltration and lower erodibility. Erosion of nutrients on organically farmed soils is therefore considered to be reduced by the same order of magnitude than the amount of eroded soil compared to conventionally farmed soils. However, the selective nature of interrill erosion potentially counteracts this effect by the preferential removal of fine particles enriched in nutrients and soil organic matter. In this study, an experiment comparing the erodibility of P and C on organically and conventially farmed soils from Devon is presented. The results show a disproportional increase of P in sediment from the organically farmed soil, reducing the perceived benefit of organic farming on nutrient erosion by 80%. The pronounced P enrichment in the organically farmed soil is attributed to the higher concentrations of C and P as well as lower densities of the small particle fraction. The results, while very preliminary, indicate that the impact of soil management on off-site effects of erosion such as water quality can only be fully assessed when we understand the relevant erosion processes. They also indicate that some less than expected positive effects of changing soil management to improve water quality might be caused by the preferential erosion of P-bearing soil particles.

Multi-scale wind erosion monitoring and assessment for US rangelands

USDA-ARS?s Scientific Manuscript database

Wind erosion is a major resource concern for rangeland managers. Although wind erosion is a naturally occurring process in many drylands, land use activities, and land management in particular, can accelerate wind-driven soil loss – impacting ecosystem dynamics and agricultural production, air quali...

Disaggregating soil erosion processes within an evolving experimental landscape

USDA-ARS?s Scientific Manuscript database

Soil-mantled landscapes subjected to rainfall, runoff events, and downstream base level adjustments will erode and evolve in time and space. Yet the precise mechanisms for soil erosion also will vary, and such variations may not be adequately captured by soil erosion prediction technology. This st...

Fundamental Understanding of Propellant/Nozzle Interaction for Rocket Nozzle Erosion Minimization Under Very High Pressure Conditions

DTIC Science & Technology

2005-08-31

conditions; with X-ray radiography for erosion rate measurements. A vortex combustor was also designed to simulate propellant product species and to...DATES COVERED Interim Progress Report, August 1, 2004 to July 31, 2005 4. TITLE AND SUBTITLE Fundamental Understanding of Propellant /Nozzle...nozzle erosion by solid- propellant combustion products. Several processes can affect the nozzle erosion rate at high pressure and temperature

Spatial bedrock erosion distribution in a natural gorge

NASA Astrophysics Data System (ADS)

Beer, A. R.; Turowski, J. M.; Kirchner, J. W.

2015-12-01

Quantitative analysis of morphological evolution both in terrestrial and planetary landscapes is of increasing interest in the geosciences. In mountainous regions, bedrock channel formation as a consequence of the interaction of uplift and erosion processes is fundamental for the entire surface evolution. Hence, the accurate description of bedrock channel development is important for landscape modelling. To verify existing concepts developed in the lab and to analyse how in situ channel erosion rates depend on the interrelations of discharge, sediment transport and topography, there is a need of highly resolved topographic field data. We analyse bedrock erosion over two years in a bedrock gorge downstream of the Gorner glacier above the town of Zermatt, Switzerland. At the study site, the Gornera stream cuts through a roche moutonnée in serpentine rock of 25m length, 5m width and 8m depth. We surveyed bedrock erosion rates using repeat terrestrial laser scanning (TLS) with an average point spacing of 5mm. Bedrock erosion rates in direction of the individual surface normals were studied directly on the scanned point clouds applying the M3C2 algorithm (Lague et al., 2013, ISPRS). The surveyed erosion patterns were compared to a simple stream erosivity visualisation obtained from painted bedrock sections at the study location. Spatially distributed erosion rates on bedrock surfaces based on millions of scan points allow deduction of millimeter-scale mean annual values of lateral erosion, incision and downstream erosion on protruding streambed surfaces. The erosion rate on a specific surface point is shown to depend on the position of this surface point in the channel's cross section, its height above the streambed and its spatial orientation to the streamflow. Abrasion by impacting bedload was likely the spatially dominant erosion process, as confirmed by the observed patterns along the painted bedrock sections. However, a single plucking event accounted for the half of the total eroded material. Our results demonstrate the practicability of TLS for highly resolved spatio-temporal erosion monitoring in the field and quantitatively confirm concepts of spatially varying erosion rates based current thinking. Furthermore, we introduce an easy-to-apply method for qualitative spatial erosion detection by paint.

Is research on soil erosion hazard and mitigation in the Global South still needed? (Alexander von Humbold Medal Lecture)

NASA Astrophysics Data System (ADS)

Poesen, Jean

2016-04-01

Soil erosion represents a geomorphological and geological hazard that may cause environmental damage (land degradation), property damage, loss of livelihoods and services as well as social and economic disruption. Erosion not only lowers the quality of our soils on site, resulting in a drastic reduction of their ecosystem functions that play a vital role in daily life, but causes also significant sediment-related problems off site. To curb soil erosion problems, a range of soil conservation techniques and strategies have been designed and are being applied. Worldwide, ca. 62 000 research papers on soil erosion and 116 000 on soil conservation have been published (Web of Science, Dec. 2015). The number of such papers dealing with the Global South represents less than 20 % of all papers, despite the fact that many regions in this part of the world face significant soil erosion problems, aggravated by a rapidly growing population and major environmental changes. Given the large number of research papers on this topic, one might therefore conclude that we now know almost everything about the various soil erosion processes and rates, their factors and consequences as well as their control so that little new knowledge can still be added to the vast amount of available information. We refute this conclusion by pointing to some major research gaps that still need to be addressed if we want to use our soils in a more sustainable way. More specifically the following topics need more research attention: 1) improved understanding of both natural and anthropogenic soil erosion processes and their interactions, 2) scaling up soil erosion processes and rates in space and time, and 3) innovative techniques and strategies to prevent or reduce erosion rates. This will be illustrated with case studies from the Global South. If future research focuses on these research gaps, we will 1) better understand processes and their interactions operating at a range of spatial and temporal scales, their rates as well as their on-site and off-site impacts, which is crucial for better targeting erosion control measures and which is academically spoken rewarding, and 2) we will also be in a better position to select the most appropriate and effective soil erosion control techniques and strategies which are badly needed for a sustainable use of our soils in the Anthropocene and for the improvement of environmental conditions worldwide.

Electromagnetic disturbance of electric drive system signal is extracted based on PLS

NASA Astrophysics Data System (ADS)

Wang, Yun; Wang, Chuanqi; Yang, Weidong; Zhang, Xu; Jiang, Li; Hou, Shuai; Chen, Xichen

2018-05-01

At present ISO11452 and GB/T33014 specified by electromagnetic immunity are narrowband electromagnetic radiation, but our exposure to electromagnetic radiation at ordinary times is not only a narrowband electromagnetic radiation, and some broadband electromagnetic radiation, and even some of the more complex electromagnetic environment. In terms of Electric vehicles, electric drive system is a kind of complex electromagnetic disturbance source, is not only a narrow-band signal, there are a lot of broadband signal, this paper puts forward PLS data processing method is adopted to analyze the electric drive system of electromagnetic disturbance, this kind of method to extract the data can be provide reliable data support for future standards.

Trends of the gully erosion development in the territory of the Republic of Tatarstan

NASA Astrophysics Data System (ADS)

Medvedeva, R. A.

2018-01-01

Gully erosion is one of the most active geomorphic processes and one of the major cause of land degradation worldwide. The aim of the study was identifying the dynamics of gully erosion development in the Republic of Tatarstan. The interpretation of satellite images were used for evaluation of the modern dynamics of gullies. Two key indicators of gully erosion (length density and gully head density) were determined. Maps of modern gully erosion for a part of the Republic of Tatarstan were constructed.

The role of lava erosion in the formation of lunar rilles and Martian channels

USGS Publications Warehouse

Carr, M.H.

1974-01-01

Lava tubes and channels develop around active sources of low viscosity lava. The channels normally form without erosion; however, sustained flow can result in the incision of a lava channel and simulation of fluvial erosion features. Lava erosion by means of thermal incision was modelled by computer, erosion rates calculated, and these compared with rates observed terrestrially. Lunar sinuous rilles are examined in light of the proposed lava erosion. The mechanism explains many features of lunar rilles that were heretofore puzzling and implies erosion rates comparable to terrestrial rates. Many Mars channels also appear to form by the action of lava; however, the larger, more spectacular Mars channels do not appear to have been formed by the same process. ?? 1974.

Modeling erosion and sedimentation coupled with hydrological and overland flow processes at the watershed scale

NASA Astrophysics Data System (ADS)

Kim, Jongho; Ivanov, Valeriy Y.; Katopodes, Nikolaos D.

2013-09-01

A novel two-dimensional, physically based model of soil erosion and sediment transport coupled to models of hydrological and overland flow processes has been developed. The Hairsine-Rose formulation of erosion and deposition processes is used to account for size-selective sediment transport and differentiate bed material into original and deposited soil layers. The formulation is integrated within the framework of the hydrologic and hydrodynamic model tRIBS-OFM, Triangulated irregular network-based, Real-time Integrated Basin Simulator-Overland Flow Model. The integrated model explicitly couples the hydrodynamic formulation with the advection-dominated transport equations for sediment of multiple particle sizes. To solve the system of equations including both the Saint-Venant and the Hairsine-Rose equations, the finite volume method is employed based on Roe's approximate Riemann solver on an unstructured grid. The formulation yields space-time dynamics of flow, erosion, and sediment transport at fine scale. The integrated model has been successfully verified with analytical solutions and empirical data for two benchmark cases. Sensitivity tests to grid resolution and the number of used particle sizes have been carried out. The model has been validated at the catchment scale for the Lucky Hills watershed located in southeastern Arizona, USA, using 10 events for which catchment-scale streamflow and sediment yield data were available. Since the model is based on physical laws and explicitly uses multiple types of watershed information, satisfactory results were obtained. The spatial output has been analyzed and the driving role of topography in erosion processes has been discussed. It is expected that the integrated formulation of the model has the promise to reduce uncertainties associated with typical parameterizations of flow and erosion processes. A potential for more credible modeling of earth-surface processes is thus anticipated.

Metamorphic records for subduction erosion and subsequent underplating processes revealed by garnet-staurolite-muscovite schists in central Qiangtang, Tibet

NASA Astrophysics Data System (ADS)

Zhang, Xiu-Zheng; Dong, Yong-Sheng; Wang, Qiang; Dan, Wei; Zhang, Chunfu; Xu, Wang; Huang, Ming-Liang

2017-01-01

Subduction erosion is confirmed as a crucial geodynamic process of crustal recycling based on geological, geochemical, and geophysical observations at modern convergent plate margins. So far, not a single metamorphic record has been used for constraining a general tectonic evolution for subduction erosion. Here we first revealed metamorphic records for a subduction erosion process based on our study of the Late Paleozoic garnet-staurolite-muscovite schists in the central Qiangtang block, Tibet. Provenance analyses suggest that the protoliths of garnet-staurolite-muscovite schists have the Northern Qiangtang-affinity and were deposited in an active continental margin setting. Mineral inclusion data show that the early metamorphic stage (M1) recorded blueschist facies pressure-temperature (P-T) conditions of 0.8-1.1 GPa and 402-441°C, indicating that a part of the material from the overriding plate had been abraded into the subduction channel and undergone high-pressure/low-temperature metamorphism. The peak metamorphic stage (M2) recorded amphibolite facies P-T conditions of 0.3-0.5 GPa and 470-520°C. The 40Ar/39Ar cooling ages (263-259 Ma) yielded from muscovite suggest the amphibolite facies metamorphism (>263 Ma) occurred at oceanic subduction stage. The distinctly staged metamorphism defines a clockwise and warming decompression P-T-t path which reveals an underplating process following the early subduction erosion. During the tectonic process, the eroded low-density material escaped from the cold subduction channel and rise upward into the warm middle-lower crust of the upper plate, undergoing amphibolite facies metamorphism. Our new results revealed a complete evolutional process from the early subduction erosion to the subsequent underplating during the northward subduction of the Paleo-Tethys Ocean.

Estimation of erosion-accumulative processes at the Inia River's mouth near high-rise construction zones.

NASA Astrophysics Data System (ADS)

Sineeva, Natalya

2018-03-01

Our study relevance is due to the increasing man-made impact on water bodies and associated land resources within the urban areas, as a consequence, by a change in the morphology and dynamics of Rivers' canals. This leads to the need to predict the development of erosion-accumulation processes, especially within the built-up urban areas. Purpose of the study is to develop programs on the assessment of erosion-accumulation processes at a water body, a mouth area of the Inia River, in the of perspective high-rise construction zone of a residential microdistrict, the place, where floodplain-channel complex is intensively expected to develop. Results of the study: Within the velocities of the water flow comparing, full-scale measured conditions, and calculated from the model, a slight discrepancy was recorded. This allows us to say that the numerical model reliably describes the physical processes developing in the River. The carried out calculations to assess the direction and intensity of the channel re-formations, made us possible to conclude, there was an insignificant predominance of erosion processes over the accumulative ones on the undeveloped part of the Inia River (the processes activity is noticeable only in certain areas (by the coasts and the island)). Importance of the study: The study on the erosion-accumulation processes evaluation can be used in design decisions for the future high-rise construction of this territory, which will increase their economic efficiency.

Modeling streamflow in a snow-dominated forest watershed using the Water Erosion Prediction Project (WEPP) model

USDA-ARS?s Scientific Manuscript database

The Water Erosion Prediction Project (WEPP) model was originally developed for hillslope and small watershed applications. The model simulates complex interactive processes influencing erosion, such as surface runoff, soil-water changes, vegetation growth and senescence, and snow accumulation and me...

The Rangeland Hydrology and Erosion Model: A dynamic approach for predicting soil loss on rangelands

USDA-ARS?s Scientific Manuscript database

In this study we present the improved Rangeland Hydrology and Erosion Model (RHEM V2.3), a process-based erosion prediction tool specific for rangeland application. The article provides the mathematical formulation of the model and parameter estimation equations. Model performance is assessed agains...

Gully head retreat in the sub-humid Ethiopian Highlands: The Ene-Chilala catchment

USDA-ARS?s Scientific Manuscript database

In the northern highlands of Ethiopia, gully erosion is severe. Despite many efforts to implement gully prevention measures, controlling gully erosion remains a challenge. The objective is to better understand the regional gully erosion processes and to prevent gully head retreat. The study was cond...

Evaluation of Interrill Erosion Under Wind-Driven Rain Events in Northern Burkina Faso

USDA-ARS?s Scientific Manuscript database

Wind changes the velocity, frequency and angle of raindrop impact and hence affects rain splash detachment rates. Many soil erosion models underpredict interrill erosion because the contribution of the wind to raindrop detachment and wind-driven transport processes are not taken into account. In thi...

Model development and applications at the USDA-ARS National Soil Erosion Research Laboratory

USDA-ARS?s Scientific Manuscript database

The United States Department of Agriculture (USDA) has a long history of development of soil erosion prediction technology, initially with empirical equations like the Universal Soil Loss Equation (USLE), and more recently with process-based models such as the Water Erosion Prediction Project (WEPP)...

Demonstration of the Water Erosion Prediction Project (WEPP) internet interface and services

USDA-ARS?s Scientific Manuscript database

The Water Erosion Prediction Project (WEPP) model is a process-based FORTRAN computer simulation program for prediction of runoff and soil erosion by water at hillslope profile, field, and small watershed scales. To effectively run the WEPP model and interpret results additional software has been de...

Internal Erosion During Soil PipeFlow: State of Science for Experimental and Numerical Analysis

EPA Science Inventory

Many field observations have led to speculation on the role of piping in embankment failures, landslides, and gully erosion. However, there has not been a consensus on the subsurface flow and erosion processes involved, and inconsistent use of terms have exacerbated the problem. ...

Assessment of environmental effects on Space Station Freedom Electrical Power System

NASA Technical Reports Server (NTRS)

Lu, Cheng-Yi; Nahra, Henry K.

1991-01-01

Analyses of EPS (electrical power system) interactions with the LEO (low earth orbit) environment are described. The results of these analyses will support EPS design so as to be compatible with the natural and induced environments and to meet power, lifetime, and performance requirements. The environmental impacts to the Space Station Freedom EPS include aerodynamic drag, atomic oxygen erosion, ultraviolet degradation, VXB effect, ionizing radiation dose and single event effects, electromagnetic interference, electrostatic discharge, plasma interactions (ion sputtering, arcing, and leakage current), meteoroid and orbital debris threats, thermal cycling effects, induced current and voltage potential differences in the SSF due to induced electric field, and contamination degradation.

Integrated process-based hydrologic and ephemeral gully modeling for better assessment of soil erosion in small watersheds

NASA Astrophysics Data System (ADS)

Sheshukov, A. Y.; Karimov, V. R.

2017-12-01

Excessive soil erosion in agriculturally dominated watersheds causes degradation of arable land and affects agricultural productivity. Structural and soil-quality best management practices can be beneficial in reducing sheet and rill erosion, however, larger rills, ephemeral gullies, and concentrated flow channels still remain to be significant sources of sediment. A better understanding of channelized soil erosion, underlying physical processes, and ways to mitigate the problem is needed to develop innovative approaches for evaluation of soil losses from various sediment sources. The goal of this study was to develop a novel integrated process-based catchment-scale model for sheet, rill, and ephemeral gully erosion and assess soil erosion mitigation practices. Geospatially, a catchment was divided into ephemeral channels and contributing hillslopes. Surface runoff hydrograph and sheet-rill erosion rates from contributing hillslopes were calculated based on the Water Erosion Prediction Project (WEPP) model. For ephemeral channels, a dynamic ephemeral gully erosion model was developed. Each channel was divided into segments, and channel flow was routed according to the kinematic wave equation. Reshaping of the channel profile in each segment (sediment deposition, soil detachment) was simulated at each time-step according to acting shear stress distribution along the channel boundary and excess shear stress equation. The approach assumed physically-consistent channel shape reconfiguration representing channel walls failure and deposition in the bottom of the channel. Soil erodibility and critical shear stress parameters were dynamically adjusted due to seepage/drainage forces based on computed infiltration gradients. The model was validated on the data obtained from the field study by Karimov et al. (2014) yielding agreement with NSE coefficient of 0.72. The developed model allowed to compute ephemeral gully erosion while accounting for antecedent soil moisture conditions. Results showed significant differences in performance of management practices for initially dry and wet soils. Application of no-till and conversion to grassland significantly reduced the erosion rates compared to conventional tillage for small runoff events, while the efficiency was reduced for large events.

Infiltration and soil erosion modelling on Lausatian post mine sites

NASA Astrophysics Data System (ADS)

Kunth, Franziska; Schmidt, Jürgen

2013-04-01

Land management of reclaimed lignite mine sites requires long-term and safe structuring of recultivation areas. Erosion by water leads to explicit soil losses, especially on heavily endangered water repellent and non-vegetated soil surfaces. Beyond that, weathering of pyrite-containing lignite burden dumps causes sulfuric acid-formation, and hence the acidification of groundwater, seepage water and surface waters. Pyrite containing sediment is detached by precipitation and transported into worked-out open cuts by draining runoff. In addition to ground water influence, erosion processes are therefore involved in acidification of surface waters. A model-based approach for the conservation of man-made slopes of post mining sites is the objective of this ongoing study. The study shall be completed by modeling of the effectiveness of different mine site recultivation scenarios. Erosion risks on man-made slopes in recultivation areas should be determined by applying the physical, raster- and event based computer model EROSION 2D/3D (Schmidt, 1991, 1992; v. Werner, 1995). The widely used erosion model is able to predict runoff as well as detachment, transport and deposition of sediments. Lignite burden dumps contain hydrophobic substances that cover soil particles. Consequently, these soils show strong water repellency, which influences the processes of infiltration and soil erosion on non-vegetated, coal containing dump soils. The influence of water repellency had to be implemented into EROSION 2D/3D. Required input data for soil erosion modelling (e.g. physical soil parameters, infiltration rates, calibration factors, etc.) were gained by soil sampling and rainfall experiments on non-vegetated as well as recultivated reclaimed mine sites in the Lusatia lignite mining region (southeast of Berlin, Germany). The measured infiltration rates on the non-vegetated water repellent sites were extremely low. Therefore, a newly developed water repellency-factor was applied to depict infiltration and erosion processes on water repellent dump soils. For infiltration modelling with EROSION 2D calibration factors (e.g. water repellency factor, skin-factor, etc.) were determined in different steps by calibrating computer modelled infiltration, respectively volume rate of flow to the measured data.

Efficacy of bedrock erosion by subglacial water flow

NASA Astrophysics Data System (ADS)

Beaud, F.; Flowers, G. E.; Venditti, J. G.

2015-09-01

Bedrock erosion by sediment-bearing subglacial water remains little-studied, however the process is thought to contribute to bedrock erosion rates in glaciated landscapes and is implicated in the excavation of tunnel valleys and the incision of inner gorges. We adapt physics-based models of fluvial abrasion to the subglacial environment, assembling the first model designed to quantify bedrock erosion caused by transient subglacial water flow. The subglacial drainage model consists of a one-dimensional network of cavities dynamically coupled to one or several Röthlisberger channels (R-channels). The bedrock erosion model is based on the tools and cover effect, whereby particles entrained by the flow impact exposed bedrock. We explore the dependency of glacial meltwater erosion on the structure and magnitude of water input to the system, the ice geometry and the sediment supply. We find that erosion is not a function of water discharge alone, but also depends on channel size, water pressure and on sediment supply, as in fluvial systems. Modelled glacial meltwater erosion rates are one to two orders of magnitude lower than the expected rates of total glacial erosion required to produce the sediment supply rates we impose, suggesting that glacial meltwater erosion is negligible at the basin scale. Nevertheless, due to the extreme localization of glacial meltwater erosion (at the base of R-channels), this process can carve bedrock (Nye) channels. In fact, our simulations suggest that the incision of bedrock channels several centimetres deep and a few meters wide can occur in a single year. Modelled incision rates indicate that subglacial water flow can gradually carve a tunnel valley and enhance the relief or even initiate the carving of an inner gorge.

Can we manipulate root system architecture to control soil erosion?

NASA Astrophysics Data System (ADS)

Ola, A.; Dodd, I. C.; Quinton, J. N.

2015-03-01

Soil erosion is a major threat to soil functioning. The use of vegetation to control erosion has long been a topic for research. Much of this research has focused on the above ground properties of plants, demonstrating the important role that canopy structure and cover plays in the reduction of water erosion processes. Less attention has been paid to plant roots. Plant roots are a crucial yet under-researched factor for reducing water erosion through their ability to alter soil properties, such as aggregate stability, hydraulic function and shear strength. However, there have been few attempts to manipulate plant root system properties to reduce soil erosion. Therefore, this review aims to explore the effects that plant roots have on soil erosion and hydrological processes, and how plant root architecture might be manipulated to enhance its erosion control properties. We clearly demonstrate the importance of root system architecture for the control of soil erosion. We also demonstrate that some plant species respond to nutrient enriched patches by increasing lateral root proliferation. The soil response to root proliferation will depend upon its location: at the soil surface dense mats of roots may block soil pores thereby limiting infiltration, enhancing runoff and thus erosion; whereas at depth local increases in shear strength may reinforce soils against structural failure at the shear plane. Additionally, in nutrient deprived regions, root hair development may be stimulated and larger amounts of root exudates released, thereby improving aggregate stability and decreasing erodibility. Utilising nutrient placement at depth may represent a potentially new, easily implemented, management strategy on nutrient poor agricultural land or constructed slopes to control erosion, and further research in this area is needed.

Gully development processes in the Ethiopian Highlands

USDA-ARS?s Scientific Manuscript database

Gully erosion is an important soil degradation process in a range of environments, causing considerable soil losses and producing large volumes of sediment. In Ethiopia, gully erosion is a major problem expanding at alarming rate and devastating cultivated and grazing lands. The objective of the stu...

How surface mounds and depressions change during rainfall events

USDA-ARS?s Scientific Manuscript database

The soil roughness, or microrelief, controls processes occurring on the surface. Although there are numerous studies on how soil roughness affects soil erosion processes, little are focused on quantifying different roughness functions on surface hydrology and erosion, i.e., water diverging and soil...

The search for a topographic signature of life.

PubMed

Dietrich, William E; Perron, J Taylor

2006-01-26

Landscapes are shaped by the uplift, deformation and breakdown of bedrock and the erosion, transport and deposition of sediment. Life is important in all of these processes. Over short timescales, the impact of life is quite apparent: rock weathering, soil formation and erosion, slope stability and river dynamics are directly influenced by biotic processes that mediate chemical reactions, dilate soil, disrupt the ground surface and add strength with a weave of roots. Over geologic time, biotic effects are less obvious but equally important: biota affect climate, and climatic conditions dictate the mechanisms and rates of erosion that control topographic evolution. Apart from the obvious influence of humans, does the resulting landscape bear an unmistakable stamp of life? The influence of life on topography is a topic that has remained largely unexplored. Erosion laws that explicitly include biotic effects are needed to explore how intrinsically small-scale biotic processes can influence the form of entire landscapes, and to determine whether these processes create a distinctive topography.

Empirical relations for cavitation and liquid impingement erosion processes

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1984-01-01

A unified power-law relationship between average erosion rate and cumulative erosion is presented. Extensive data analyses from venturi, magnetostriction (stationary and oscillating specimens), liquid drop, and jet impact devices appear to conform to this relation. A normalization technique using cavitation and liquid impingement erosion data is also presented to facilitate prediction. Attempts are made to understand the relationship between the coefficients in the power-law relationships and the material properties.

Monitoring and assessment of soil erosion at micro-scale and macro-scale in forests affected by fire damage in northern Iran.

PubMed

Akbarzadeh, Ali; Ghorbani-Dashtaki, Shoja; Naderi-Khorasgani, Mehdi; Kerry, Ruth; Taghizadeh-Mehrjardi, Ruhollah

2016-12-01

Understanding the occurrence of erosion processes at large scales is very difficult without studying them at small scales. In this study, soil erosion parameters were investigated at micro-scale and macro-scale in forests in northern Iran. Surface erosion and some vegetation attributes were measured at the watershed scale in 30 parcels of land which were separated into 15 fire-affected (burned) forests and 15 original (unburned) forests adjacent to the burned sites. The soil erodibility factor and splash erosion were also determined at the micro-plot scale within each burned and unburned site. Furthermore, soil sampling and infiltration studies were carried out at 80 other sites, as well as the 30 burned and unburned sites, (a total of 110 points) to create a map of the soil erodibility factor at the regional scale. Maps of topography, rainfall, and cover-management were also determined for the study area. The maps of erosion risk and erosion risk potential were finally prepared for the study area using the Revised Universal Soil Loss Equation (RUSLE) procedure. Results indicated that destruction of the protective cover of forested areas by fire had significant effects on splash erosion and the soil erodibility factor at the micro-plot scale and also on surface erosion, erosion risk, and erosion risk potential at the watershed scale. Moreover, the results showed that correlation coefficients between different variables at the micro-plot and watershed scales were positive and significant. Finally, assessment and monitoring of the erosion maps at the regional scale showed that the central and western parts of the study area were more susceptible to erosion compared with the western regions due to more intense crop-management, greater soil erodibility, and more rainfall. The relationships between erosion parameters and the most important vegetation attributes were also used to provide models with equations that were specific to the study region. The results of this paper can be useful for better understanding erosion processes at the micro-scale and macro-scale in any region having similar vegetation attributes to the forests of northern Iran.

The role of vegetation on gully erosion stabilization at a severely degraded landscape: A case study from Calhoun Experimental Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Bastola, S.; Dialynas, Y. G.; Bras, R. L.; Noto, L. V.; Istanbulluoglu, E.

2018-05-01

Gully erosion was evidence of land degradation in the southern Piedmont, site of the Calhoun Critical Zone Observatory (CCZO), during the cotton farming era. Understanding of the underlying gully erosion processes is essential to develop gully erosion models that could be useful in assessing the effectiveness of remedial and soil erosion control measures such as gully backfilling, revegetation, and terracing. Development and validation of process-based gully erosion models is difficult because observations of the formation and progression of gullies are limited. In this study, analytic formulations of the two dominant gullying processes, namely, plunge pool erosion and slab failure, are utilized to simulate the gullying processes in the 4-km2 Holcombe's Branch watershed. In order to calibrate parameters of the gully erosion model, gully features (e.g., depth and area) extracted from a high-resolution LiDAR map are used. After the calibration, the gully model is able to delineate the spatial extent of gullies whose statistics are in close agreement with the gullies extracted from the LiDAR DEM. Several simulations with the calibrated model are explored to evaluate the effectiveness of various gully remedial measures, such as backfilling and revegetation. The results show that in the short-term, the reshaping of the topographical surface by backfilling and compacting gullies is effective in slowing down the growth of gullies (e.g., backfilling decreased the spatial extent of gullies by 21-46% and decreased the average depth of gullies by up to 9%). Revegetation, however, is a more effective approach to stabilizing gullies that would otherwise expand if no gully remedial measures are implemented. Analyses of our simulations show that the gully stabilization effect of revegetation varies over a wide range, i.e., leading to 23-69% reduction of the spatial extent of gullies and up to 45% reduction in the depth of gullies, depending on the selection of plant species and management practices.

Relations between rainfall–runoff-induced erosion and aeolian deposition at archaeological sites in a semi-arid dam-controlled river corridor

USGS Publications Warehouse

Collins, Brian D.; Bedford, David; Corbett, Skye C.; Fairley, Helen C.; Cronkite-Ratcliff, Collin

2016-01-01

Process dynamics in fluvial-based dryland environments are highly complex with fluvial, aeolian, and alluvial processes all contributing to landscape change. When anthropogenic activities such as dam-building affect fluvial processes, the complexity in local response can be further increased by flood- and sediment-limiting flows. Understanding these complexities is key to predicting landscape behavior in drylands and has important scientific and management implications, including for studies related to paleoclimatology, landscape ecology evolution, and archaeological site context and preservation. Here we use multi-temporal LiDAR surveys, local weather data, and geomorphological observations to identify trends in site change throughout the 446-km-long semi-arid Colorado River corridor in Grand Canyon, Arizona, USA, where archaeological site degradation related to the effects of upstream dam operation is a concern. Using several site case studies, we show the range of landscape responses that might be expected from concomitant occurrence of dam-controlled fluvial sand bar deposition, aeolian sand transport, and rainfall-induced erosion. Empirical rainfall-erosion threshold analyses coupled with a numerical rainfall–runoff–soil erosion model indicate that infiltration-excess overland flow and gullying govern large-scale (centimeter- to decimeter-scale) landscape changes, but that aeolian deposition can in some cases mitigate gully erosion. Whereas threshold analyses identify the normalized rainfall intensity (defined as the ratio of rainfall intensity to hydraulic conductivity) as the primary factor governing hydrologic-driven erosion, assessment of false positives and false negatives in the dataset highlight topographic slope as the next most important parameter governing site response. Analysis of 4+ years of high resolution (four-minute) weather data and 75+ years of low resolution (daily) climate records indicates that dryland erosion is dependent on short-term, storm-driven rainfall intensity rather than cumulative rainfall, and that erosion can occur outside of wet seasons and even wet years. These results can apply to other similar semi-arid landscapes where process complexity may not be fully understood.

Can we manipulate root system architecture to control soil erosion?

NASA Astrophysics Data System (ADS)

Ola, A.; Dodd, I. C.; Quinton, J. N.

2015-09-01

Soil erosion is a major threat to soil functioning. The use of vegetation to control erosion has long been a topic for research. Much of this research has focused on the above-ground properties of plants, demonstrating the important role that canopy structure and cover plays in the reduction of water erosion processes. Less attention has been paid to plant roots. Plant roots are a crucial yet under-researched factor for reducing water erosion through their ability to alter soil properties, such as aggregate stability, hydraulic function and shear strength. However, there have been few attempts to specifically manipulate plant root system properties to reduce soil erosion. Therefore, this review aims to explore the effects that plant roots have on soil erosion and hydrological processes, and how plant root architecture might be manipulated to enhance its erosion control properties. We demonstrate the importance of root system architecture for the control of soil erosion. We also show that some plant species respond to nutrient-enriched patches by increasing lateral root proliferation. The erosional response to root proliferation will depend upon its location: at the soil surface dense mats of roots may reduce soil erodibility but block soil pores thereby limiting infiltration, enhancing runoff. Additionally, in nutrient-deprived regions, root hair development may be stimulated and larger amounts of root exudates released, thereby improving aggregate stability and decreasing erodibility. Utilizing nutrient placement at specific depths may represent a potentially new, easily implemented, management strategy on nutrient-poor agricultural land or constructed slopes to control erosion, and further research in this area is needed.

Sediment dynamics in an overland flow-prone forest catchment

NASA Astrophysics Data System (ADS)

Zimmermann, Alexander; Elsenbeer, Helmut

2010-05-01

Vegetation controls erosion in many respects, and it is assumed that forest cover is an effective control. Currently, most literature on erosion processes in forest ecosystems support this impression and estimates of sediment export from forested catchments serve as benchmarks to evaluate erosion processes under different land uses. Where soil properties favor near-surface flow paths, however, vegetation may not mitigate surface erosion. In the forested portion of the Panama Canal watershed overland flow is widespread and occurs frequently, and indications of active sediment transport are hard to overlook. In this area we selected a 9.7 ha catchment for a high-resolution study of suspended sediment dynamics. We equipped five nested catchments to elucidate sources, drivers, magnitude and timing of suspended sediment export by continuous monitoring of overland flow and stream flow and by simultaneous, event-based sediment sampling. The support program included monitoring throughfall, splash erosion, overland-flow connectivity and a survey of infiltrability, permeability, and aggregate stability. This dataset allowed a comprehensive view on erosion processes. We found that overland flow controls the suspended-sediment dynamics in channels. Particularly, rainfalls of high intensity at the end of the rainy season have a superior impact on the overall sediment export. During these events, overland flow occurs catchment-wide up to the divide and so does erosion. With our contribution we seek to provide evidence that forest cover and large sediment yields are no contradiction in terms even in the absence of mass movements.

Erosion processes by water in agricultural landscapes: a low-cost methodology for post-event analyses

NASA Astrophysics Data System (ADS)

Prosdocimi, Massimo; Calligaro, Simone; Sofia, Giulia; Tarolli, Paolo

2015-04-01

Throughout the world, agricultural landscapes assume a great importance, especially for supplying food and a livelihood. Among the land degradation phenomena, erosion processes caused by water are those that may most affect the benefits provided by agricultural lands and endanger people who work and live there. In particular, erosion processes that affect the banks of agricultural channels may cause the bank failure and represent, in this way, a severe threat to floodplain inhabitants and agricultural crops. Similarly, rills and gullies are critical soil erosion processes as well, because they bear upon the productivity of a farm and represent a cost that growers have to deal with. To estimate quantitatively soil losses due to bank erosion and rills processes, area based measurements of surface changes are necessary but, sometimes, they may be difficult to realize. In fact, surface changes due to short-term events have to be represented with fine resolution and their monitoring may entail too much money and time. The main objective of this work is to show the effectiveness of a user-friendly and low-cost technique that may even rely on smart-phones, for the post-event analyses of i) bank erosion affecting agricultural channels, and ii) rill processes occurring on an agricultural plot. Two case studies were selected and located in the Veneto floodplain (northeast Italy) and Marche countryside (central Italy), respectively. The work is based on high-resolution topographic data obtained by the emerging, low-cost photogrammetric method named Structure-from-Motion (SfM). Extensive photosets of the case studies were obtained using both standalone reflex digital cameras and smart-phone built-in cameras. Digital Terrain Models (DTMs) derived from SfM revealed to be effective to estimate quantitatively erosion volumes and, in the case of the bank eroded, deposited materials as well. SfM applied to pictures taken by smartphones is useful for the analysis of the topography and Earth surface processes at very low-cost. This methodology should be of great help for farmers and/or technician who work at Land Reclamation Consortia or at Civil Protection for taking suitable post-event field surveys in support to flood risk and soil management.

Reemission spectra and inelastic processes at interaction of attosecond and shorter duration electromagnetic pulses with atoms

NASA Astrophysics Data System (ADS)

Makarov, D. N.; Matveev, V. I.

2017-01-01

Inelastic processes and the reemission of attosecond and shorter electromagnetic pulses by atoms have been considered within the analytical solution of the Schrödinger equation in the sudden perturbation approximation. A method of calculations with the exact inclusion of spatial inhomogeneity of the field of an ultrashort pulse and the momenta of photons in the reemission processes has been developed. The probabilities of inelastic processes and spectra of reemission of ultrashort electromagnetic pulses by one- and many-electron atoms have been calculated. The results have been presented in the form of analytical formulas.

On electromagnetic forming processes in finitely strained solids: Theory and examples

NASA Astrophysics Data System (ADS)

Thomas, J. D.; Triantafyllidis, N.

2009-08-01

The process of electromagnetic forming (EMF) is a high velocity manufacturing technique that uses electromagnetic (Lorentz) body forces to shape sheet metal parts. EMF holds several advantages over conventional forming techniques: speed, repeatability, one-sided tooling, and most importantly considerable ductility increase in several metals. Current modeling techniques for EMF processes are not based on coupled variational principles to simultaneously account for electromagnetic and mechanical effects. Typically, separate solutions to the electromagnetic (Maxwell) and motion (Newton) equations are combined in staggered or lock-step methods, sequentially solving the mechanical and electromagnetic problems. The present work addresses these issues by introducing a fully coupled Lagrangian (reference configuration) least-action variational principle, involving magnetic flux and electric potentials and the displacement field as independent variables. The corresponding Euler-Lagrange equations are Maxwell's and Newton's equations in the reference configuration, which are shown to coincide with their current configuration counterparts obtained independently by a direct approach. The general theory is subsequently simplified for EMF processes by considering the eddy current approximation. Next, an application is presented for axisymmetric EMF problems. It is shown that the proposed variational principle forms the basis of a variational integration numerical scheme that provides an efficient staggered solution algorithm. As an illustration a number of such processes are simulated, inspired by recent experiments of freely expanding uncoated and polyurea-coated aluminum tubes.

Constructing a sequence of palaeoDEMs to obtain erosion rates in a drainage basin.N

NASA Astrophysics Data System (ADS)

Castelltort, F. Xavier; Carles Balasch, J.; Cirés, Jordi; Colombo, Ferran

2017-04-01

DEMs made in a present-day drainage basin, considering it as a geomorphic unit, represent the end result of a landscape evolution. This process has had to follow a model of erosion. Trying to establish a conceptual erosion model in landscape evolution represents the first difficulty in constructing a sequence of palaeoDEMs. But if one is able to do it, the result will be easier and believable. The next step to do is to make a catalogue of base level types present in the drainage basin. The list has to include elements with determinate position and elevation (x, y, z) from the centre of the basin until hillslopes. A list of base level types may contain fluvial terrace remnants, erosive surfaces, palaeosols, alluvial covers of glacis, alluvial fans, rockfalls, landslides and scree zones. It is very important to know the spatial and temporal relations between the elements of the list, even if they are disconnected by erosion processes. Relative chronologies have to be set for all elements of the catalogue, and as far as possible absolute chronologies. To do it,it is essential to have established first the spatial relations between them, including those elements that are gone. Moreover, it is also essential to have adapted all the elements to the conceptual erosion model proposed. In this step, it has to be kept in mind that erosion rates can be very different in determinate areas within the same geomorphic unit. Erosion processes are focused in specific zones while other areas are maintained in stability. A good technique to construct a palaeoDEM is to start making, by hand, a map of contour lines. At this point, it is valuable to use the elements' catalogue. The use of those elements belonging to the same palaeosurface will result in a map. Several maps can be obtained from a catalogue. Contour maps can be gridded into a 3D surface by means of a specific application and a set of surfaces will be obtained. Algebraic operations can be done with palaeoDEMs obtaining positive or negative volumes corresponding to processes of erosion or aggradation. A case study of the application of palaeoDEMs is presented in the process of homoclinal shifting that is the origin of the strike valley of La Plana de Vic in the NE of Iberian Peninsula.

Mapping Subsea Permafrost Using Suface-Towed Electromagnetic Methods Near Prudhoe Bay, AK

NASA Astrophysics Data System (ADS)

Sherman, D.; Constable, S.

2017-12-01

We have developed a surface-towed electric dipole-dipole system capable of operating in shallow water and deployable from small boats. Our system uses electromagnetic energy from a modulated manmade source to interrogate the underlying resistivity structure of the seafloor. We used this system in the summers of 2014 and 2015 to map subsea ice-bonded permafrost on the Beaufort Shelf along 200 km of coastline, from Tigvariak Island to Harrison Bay. Permafrost is resistive and was found to be anisotropic, likely due to interbedded layers of frozen and unfrozen sediment. Maps of depth to permafrost and its thickness were produced and results compared to borehole logs in the area. We observed elevated resistivity values offshore the Sagavanirktok River outflow, supporting the idea that fresh groundwater flow has a preserving effect on submerged permafrost. This system provides a cost effective method that could be used to further quantify permafrost extent, provide a baseline for measurements of future degradation, answer questions about the relationship between coastal erosion rates and offshore permafrost, and provide observational constraints on pore water salinity to aid in permafrost modeling studies.

Bedrock river erosion measurements and modelling along a river of the Frontal Himalaya

NASA Astrophysics Data System (ADS)

Lave, Jerome; Dubille, Matthieu

2017-04-01

River incision is a key process in mountains denudation and therefore in landscape evolution models. Despite its importance, most incision models for mountain rivers rely on simplified, or quite empirical relations, and generally only consider annual average values for water discharge and sediment flux. In contrast, very few studies consider mechanistic models at the timescale of a flood, and try to bridge the gap between experimental or theoretical approaches and long term river incision studies. In this contribution, we present observations made during 7 monsoon seasons on fluvial bedrock erosion along the Bakeya river across the Frontal Himalaya in Central Nepal. Along its lower gorge, this river incises alternation of indurated sandstone and less resistant claystone, at Holocene rates larger than 10mm/yr. More importantly, its upper drainage mostly drains through non-cohesive conglomerate which allows, in this specific setting, estimating the bedload characteristics and instantaneous fluxes, i.e. a pre-requisite to test mechanistic models of fluvial erosion. During the study period, we monitored and documented the channel bank erosion in order to understand the amplitude of the erosion processes, their occurrence in relation with hydrology, in order to test time-integrated models of erosion. Besides hydrologic monitoring, erosion measurements were threefold: (1) at the scale of the whole monsoon, plucking and block removal by repeated photo surveys of a 400m long channel reach, (2) detailed microtopographic surveys of channel bedrock elevation along a few sandstone bars to document their abrasion, (3) real time measurement of fluvial bedrock wear to document erosion timing using a new erosion sensor. Results indicate that: 1. Erosion is highly dependent on rock resistance, but on average block detachment and removal is a more efficient process than bedrock attrition, and operates at a rate that permit channel banks downcutting to keep pace with Holocene uplift rate. 2. Both block detachment and attrition processes clearly increase with fluvial shear stress, but non-linearly, in particular through the existence of a minimum threshold. As a result of which bank erosion occur during only a few hours per year during short and very high flood events, which questions the use of average discharge (or drainage area) in many bedrock erosion models. We then propose a semi-physical model of sandstone bars abrasion based on discharge history (HEC-RAS modelling), Rouse suspension model, and experimental measurements on dependency of abrasion rate vs impacting particle size. This model predicts well the timing and the amplitude of both real-time and monsoon average abrasion along the surveyed sandstone bars. This first validation of a model for bank erosion opens large perspective for future work on channel bottom incision modelling using physical models of erosion and their time- and gravel-size-integration, with the objective to introduce more physical rules in landscape evolution models.

Experimental Investigation of Rainfall Impact on Overland Flow Driven Erosion Processes and Flow Hydrodynamics on a Steep Hillslope

NASA Astrophysics Data System (ADS)

Tian, P.; Xu, X.; Pan, C.; Hsu, K. L.; Yang, T.

2016-12-01

Few attempts have been made to investigate the quantitative effects of rainfall on overland flow driven erosion processes and flow hydrodynamics on steep hillslopes under field conditions. Field experiments were performed in flows for six inflow rates (q: 6-36 Lmin-1m-1) with and without rainfall (60 mm h-1) on a steep slope (26°) to investigate: (1) the quantitative effects of rainfall on runoff and sediment yield processes, and flow hydrodynamics; (2) the effect of interaction between rainfall and overland flow on soil loss. Results showed that the rainfall increased runoff coefficients and the fluctuation of temporal variations in runoff. The rainfall significantly increased soil loss (10.6-68.0%), but this increment declined as q increased. When the interrill erosion dominated (q=6 Lmin-1m-1), the increment in the rill erosion was 1.5 times that in the interrill erosion, and the effect of the interaction on soil loss was negative. When the rill erosion dominated (q=6-36 Lmin-1m-1), the increment in the interrill erosion was 1.7-8.8 times that in the rill erosion, and the effect of the interaction on soil loss became positive. The rainfall was conducive to the development of rills especially for low inflow rates. The rainfall always decreased interrill flow velocity, decreased rill flow velocity (q=6-24 Lmin-1m-1), and enhanced the spatial uniformity of the velocity distribution. Under rainfall disturbance, flow depth, Reynolds number (Re) and resistance were increased but Froude number was reduced, and lower Re was needed to transform a laminar flow to turbulent flow. The rainfall significantly increased flow shear stress (τ) and stream power (φ), with the most sensitive parameters to sediment yield being τ (R2=0.994) and φ (R2=0.993), respectively, for non-rainfall and rainfall conditions. Compared to non-rainfall conditions, there was a reduction in the critical hydrodynamic parameters of mean flow velocity, τ, and φ by the rainfall. These findings provide a better understanding on the influence mechanism of rainfall impact on hillslope erosion processes.

Misrepresentation of hydro-erosional processes in rainfall simulations using disturbed soil samples

NASA Astrophysics Data System (ADS)

Thomaz, Edivaldo L.; Pereira, Adalberto A.

2017-06-01

Interrill erosion is a primary soil erosion process which consists of soil detachment by raindrop impact and particle transport by shallow flow. Interill erosion affects other soil erosion sub-processes, e.g., water infiltration, sealing, crusting, and rill initiation. Interrill erosion has been widely studied in laboratories, and the use of a sieved soil, i.e., disturbed soil, has become a standard method in laboratory experiments. The aims of our study are to evaluate the hydro-erosional response of undisturbed and disturbed soils in a laboratory experiment, and to quantify the extent to which hydraulic variables change during a rainstorm. We used a splash pan of 0.3 m width, 0.45 m length, and 0.1 m depth. A rainfall simulation of 58 mm h- 1 lasting for 30 min was conducted on seven replicates of undisturbed and disturbed soils. During the experiment, several hydro-physical parameters were measured, including splashed sediment, mean particle size, runoff, water infiltration, and soil moisture. We conclude that use of disturbed soil samples results in overestimation of interrill processes. Of the nine assessed parameters, four displayed greater responses in the undisturbed soil: infiltration, topsoil shear strength, mean particle size of eroded particles, and soil moisture. In the disturbed soil, five assessed parameters displayed greater responses: wash sediment, final runoff coefficient, runoff, splash, and sediment yield. Therefore, contextual soil properties are most suitable for understanding soil erosion, as well as for defining soil erodibility.

The erosion of the beaches on the coast of Alicante: Study of the mechanisms of weathering by accelerated laboratory tests.

PubMed

López, I; López, M; Aragonés, L; García-Barba, J; López, M P; Sánchez, I

2016-10-01

One of the main problems that coasts around the world present, is the regression and erosion of beaches. However, the factors involved in these processes are unclear. In this study, the influence of sediment erosion on beach regression has been analysed. In order to do that, a three-step investigation has been carried out. Firstly, coastline variations of four Spanish beaches have been analysed. Secondly, a study on sediment position along the beach profile has been developed. Finally, the process that beach sediments undergo along the surf zone when they are hit by the incident waves has been simulated by an accelerated particle weathering test. Samples of sand and shells were subjected to this accelerated particle weathering test. Results were supplemented with those from carbonate content test, XRD, SEM and granulometric analysis. Results shows a cross-shore classification of sediments along the beach profile in which finer particles move beyond offshore limit. Besides, it was observed that sediment erosion process is divided into three sages: i) particles wear due to crashes ii) dissolution of the carbonate fraction, and iii) breakage and separation of mineral and carbonate parts of particles. All these processes lead to a reduction of particle size. The mechanism responsible of beach erosion would consist of multiples and continuous particle location exchanges along the beach profile as a consequence of grain-size decrease due to erosion. Copyright © 2016 Elsevier B.V. All rights reserved.

Erosion and Sediment Transport Modelling in Shallow Waters: A Review on Approaches, Models and Applications.

PubMed

Hajigholizadeh, Mohammad; Melesse, Assefa M; Fuentes, Hector R

2018-03-14

The erosion and sediment transport processes in shallow waters, which are discussed in this paper, begin when water droplets hit the soil surface. The transport mechanism caused by the consequent rainfall-runoff process determines the amount of generated sediment that can be transferred downslope. Many significant studies and models are performed to investigate these processes, which differ in terms of their effecting factors, approaches, inputs and outputs, model structure and the manner that these processes represent. This paper attempts to review the related literature concerning sediment transport modelling in shallow waters. A classification based on the representational processes of the soil erosion and sediment transport models (empirical, conceptual, physical and hybrid) is adopted, and the commonly-used models and their characteristics are listed. This review is expected to be of interest to researchers and soil and water conservation managers who are working on erosion and sediment transport phenomena in shallow waters. The paper format should be helpful for practitioners to identify and generally characterize the types of available models, their strengths and their basic scope of applicability.

Erosion and Sediment Transport Modelling in Shallow Waters: A Review on Approaches, Models and Applications

PubMed Central

Fuentes, Hector R.

2018-01-01

The erosion and sediment transport processes in shallow waters, which are discussed in this paper, begin when water droplets hit the soil surface. The transport mechanism caused by the consequent rainfall-runoff process determines the amount of generated sediment that can be transferred downslope. Many significant studies and models are performed to investigate these processes, which differ in terms of their effecting factors, approaches, inputs and outputs, model structure and the manner that these processes represent. This paper attempts to review the related literature concerning sediment transport modelling in shallow waters. A classification based on the representational processes of the soil erosion and sediment transport models (empirical, conceptual, physical and hybrid) is adopted, and the commonly-used models and their characteristics are listed. This review is expected to be of interest to researchers and soil and water conservation managers who are working on erosion and sediment transport phenomena in shallow waters. The paper format should be helpful for practitioners to identify and generally characterize the types of available models, their strengths and their basic scope of applicability. PMID:29538335

Advances in the continuous monitoring of erosion and deposition dynamics: Developments and applications of the new PEEP-3T system

NASA Astrophysics Data System (ADS)

Lawler, D. M.

2008-01-01

In most episodic erosion and deposition systems, knowledge of the timing of geomorphological change, in relation to fluctuations in the driving forces, is crucial to strong erosion process inference, and model building, validation and development. A challenge for geomorphology, however, is that few studies have focused on geomorphological event structure (timing, magnitude, frequency and duration of individual erosion and deposition events), in relation to applied stresses, because of the absence of key monitoring methodologies. This paper therefore (a) presents full details of a new erosion and deposition measurement system — PEEP-3T — developed from the Photo-Electronic Erosion Pin sensor in five key areas, including the addition of nocturnal monitoring through the integration of the Thermal Consonance Timing (TCT) concept, to produce a continuous sensing system; (b) presents novel high-resolution datasets from the redesigned PEEP-3T system for river bank system of the Rivers Nidd and Wharfe, northern England, UK; and (c) comments on their potential for wider application throughout geomorphology to address these key measurement challenges. Relative to manual methods of erosion and deposition quantification, continuous PEEP-3T methodologies increase the temporal resolution of erosion/deposition event detection by more than three orders of magnitude (better than 1-second resolution if required), and this facility can significantly enhance process inference. Results show that river banks are highly dynamic thermally and respond quickly to radiation inputs. Data on bank retreat timing, fixed with PEEP-3T TCT evidence, confirmed that they were significantly delayed up to 55 h after flood peaks. One event occurred 13 h after emergence from the flow. This suggests that mass failure processes rather than fluid entrainment dominated the system. It is also shown how, by integrating turbidity instrumentation with TCT ideas, linkages between sediment supply and sediment flux can be forged at event timescales, and a lack of sediment exhaustion was evident here. Five challenges for wider geomorphological process investigation are discussed. This event-based dynamics approach, based on continuous monitoring methodologies, appears to have considerable wider potential for stronger process inference and model testing and validation in many areas of geomorphology.

Mechanical erosion of xenoliths by magmatic shear flow

NASA Astrophysics Data System (ADS)

Del Gaudio, Piero; Ventura, Guido

2008-05-01

We focus on the role of mechanical erosion by magmatic shear flow in the formation of xenoliths occurring in lava flows. The process is analyzed by combining the physics of fragmentation and erosion to the concept of rock mass. The conditions for the country rock fragmentation are analyzed as a function of the magma viscosity, strain rate and tensile strength of the rock mass. In reservoirs, mechanical processes play a subordinate role and thermal erosion processes prevail. In conduits, intermediate and silicic magmas may erode and, eventually, fragment good to poor quality country rock masses. Basalts may erode poor quality country rocks. A crystal-rich magma has more chance to break up the conduit walls with respect to a vesiculated melt. The variety of xenoliths of a lava reflects a set of wall-rocks with similar mechanical properties and may not mirror the stratigraphy of the substratum of a volcanic area.

Advancements in Hydrology and Erosion Process Understanding and Post-Fire Hydrologic and Erosion Model Development for Semi-Arid Landscapes

NASA Astrophysics Data System (ADS)

Williams, C. Jason; Pierson, Frederick B.; Al-Hamdan, Osama Z.; Robichaud, Peter R.; Nearing, Mark A.; Hernandez, Mariano; Weltz, Mark A.; Spaeth, Kenneth E.; Goodrich, David C.

2017-04-01

Fire activity continues to increase in semi-arid regions around the globe. Private and governmental land management entities are challenged with predicting and mitigating post-fire hydrologic and erosion responses on these landscapes. For more than a decade, a team of scientists with the US Department of Agriculture has collaborated on extensive post-fire hydrologic field research and the application of field research to development of post-fire hydrology and erosion predictive technologies. Experiments funded through this research investigated the impacts of fire on vegetation and soils and the effects of these fire-induced changes on infiltration, runoff generation, erodibility, and soil erosion processes. The distribution of study sites spans diverse topography across grassland, shrubland, and woodland landscapes throughout the western United States. Knowledge gleaned from the extensive field experiments was applied to develop and enhance physically-based models for hillslope- to watershed-scale runoff and erosion prediction. Our field research and subsequent data syntheses have identified key knowledge gaps and challenges regarding post-fire hydrology and erosion modeling. Our presentation details some consistent trends across a diverse domain and varying landscape conditions based on our extensive field campaigns. We demonstrate how field data have advanced our understanding of post-fire hydrology and erosion for semi-arid landscapes and highlight remaining key knowledge gaps. Lastly, we briefly show how our well-replicated experimental methodologies have contributed to advancements in hydrologic and erosion model development for the post-fire environment.

Soil erosion under multiple time-varying rainfall events

NASA Astrophysics Data System (ADS)

Heng, B. C. Peter; Barry, D. Andrew; Jomaa, Seifeddine; Sander, Graham C.

2010-05-01

Soil erosion is a function of many factors and process interactions. An erosion event produces changes in surface soil properties such as texture and hydraulic conductivity. These changes in turn alter the erosion response to subsequent events. Laboratory-scale soil erosion studies have typically focused on single independent rainfall events with constant rainfall intensities. This study investigates the effect of multiple time-varying rainfall events on soil erosion using the EPFL erosion flume. The rainfall simulator comprises ten Veejet nozzles mounted on oscillating bars 3 m above a 6 m × 2 m flume. Spray from the nozzles is applied onto the soil surface in sweeps; rainfall intensity is thus controlled by varying the sweeping frequency. Freshly-prepared soil with a uniform slope was subjected to five rainfall events at daily intervals. In each 3-h event, rainfall intensity was ramped up linearly to a maximum of 60 mm/h and then stepped down to zero. Runoff samples were collected and analysed for particle size distribution (PSD) as well as total sediment concentration. We investigate whether there is a hysteretic relationship between sediment concentration and discharge within each event and how this relationship changes from event to event. Trends in the PSD of the eroded sediment are discussed and correlated with changes in sediment concentration. Close-up imagery of the soil surface following each event highlight changes in surface soil structure with time. This study enhances our understanding of erosion processes in the field, with corresponding implications for soil erosion modelling.

Effect of current ripple on cathode erosion in 30 kWe class arcjets

NASA Technical Reports Server (NTRS)

Harris, William J.; O'Hair, Edgar A.; Hatfield, Lynn L.; Kristiansen, M.; Grimes, Montgomery D.

1991-01-01

An investigation was conducted to study the effect of current ripple on cathode erosion in 30 kWe class arcjets to determine the change in the cathode erosion rate for high (11 percent) and low (4 percent) current ripple. The measurements were conducted using a copper-tungsten cathode material to accelerate the cathode erosion process. It is shown that the high ripple erosion rate was initially higher than the low ripple erosion rate, but decreased asymptotically with time to a level less than half that of the low ripple value. Results suggest that high ripple extends the cathode lifetime for long duration operation, and improves arc stability by increasing the cathode attachment area.

Predicting plot soil loss by empirical and process-oriented approaches: A review

USDA-ARS?s Scientific Manuscript database

Soil erosion directly affects the quality of the soil, its agricultural productivity and its biological diversity. Many mathematical models have been developed to estimate plot soil erosion at different temporal scales. At present, empirical soil loss equations and process-oriented models are consid...

Structural and functional connectivity as a driver of hillslope erosion following disturbance

USDA-ARS?s Scientific Manuscript database

Hydrologic response to rainfall input on fragmented or burnt hillslopes is strongly influenced by the ensuing connectivity of runoff and erosion processes. Yet, cross-scale process connectivity is seldom evaluated in field studies due scale limitations in experimental design. This study quantified...

10 CFR Appendix H to Part 110 - Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export...

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 2 2010-01-01 2010-01-01 false Illustrative List of Electromagnetic Enrichment Plant... Appendix H to Part 110—Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export Licensing Authority Note—In the electromagnetic process, uranium metal ions produced by...

10 CFR Appendix H to Part 110 - Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export...

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 2 2013-01-01 2013-01-01 false Illustrative List of Electromagnetic Enrichment Plant... Appendix H to Part 110—Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export Licensing Authority Note—In the electromagnetic process, uranium metal ions produced by...

10 CFR Appendix H to Part 110 - Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export...

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 2 2011-01-01 2011-01-01 false Illustrative List of Electromagnetic Enrichment Plant... Appendix H to Part 110—Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export Licensing Authority Note—In the electromagnetic process, uranium metal ions produced by...

10 CFR Appendix H to Part 110 - Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export...

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 2 2012-01-01 2012-01-01 false Illustrative List of Electromagnetic Enrichment Plant... Appendix H to Part 110—Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export Licensing Authority Note—In the electromagnetic process, uranium metal ions produced by...

10 CFR Appendix H to Part 110 - Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export...

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 2 2014-01-01 2014-01-01 false Illustrative List of Electromagnetic Enrichment Plant... Appendix H to Part 110—Illustrative List of Electromagnetic Enrichment Plant Equipment and Components Under NRC Export Licensing Authority Note: In the electromagnetic process, uranium metal ions produced by...

A new perspective on soil erosion: exploring a thermodynamic approach in a small area of the River Inn catchment

NASA Astrophysics Data System (ADS)

Reid, Lucas; Scherer, Ulrike; Zehe, Erwin

2016-04-01

Soil erosion modeling has always struggled with compensating for the difference in time and spatial scale between model, data and the actual processes involved. This is especially the case with non-event based long-term models based on the Universal Soil Loss Equation (USLE), yet USLE based soil erosion models are among the most common and widely used for they have rather low data requirements and can be applied to large areas. But the majority of mass from soil erosion is eroded within short periods of times during heavy rain events, often within minutes or hours. Advancements of the USLE (eg. the Modified Universal Soil Loss Equation, MUSLE) allow for a daily time step, but still apply the same empirical methods derived from the USLE. And to improve the actual quantification of sediment input into rivers soil erosion models are often combined with a Sediment Delivery Ratio (SDR) to get results within the range of measurements. This is still a viable approach for many applications, yet it leaves much to be desired in terms of understanding and reproducing the processes behind soil erosion and sediment input into rivers. That's why, instead of refining and retuning the existing methods, we explore a more comprehensive, physically consistent description on soil erosion. The idea is to describe soil erosion as a dissipative process (Kleidon et al., 2013) and test it in a small sub-basin of the River Inn catchment area in the pre-Alpine foothills. We then compare the results to sediment load measurements from the sub-basin and discuss the advantages and issues with the application of such an approach.

Post-wildfire landscape change and erosional processes from repeat terrestrial lidar in a steep headwater catchment, Chiricahua Mountains, Arizona, USA

NASA Astrophysics Data System (ADS)

DeLong, Stephen B.; Youberg, Ann M.; DeLong, Whitney M.; Murphy, Brendan P.

2018-01-01

Flooding and erosion after wildfires present increasing hazard as climate warms, semi-arid lands become drier, population increases, and the urban interface encroaches farther into wildlands. We quantify post-wildfire erosion in a steep, initially unchannelized, 7.5 ha headwater catchment following the 2011 Horseshoe 2 Fire in the Chiricahua Mountains of southeastern Arizona. Using time-lapse cameras, rain gauges, and repeat surveys by terrestrial laser scanner, we quantify the response of a burned landscape to subsequent precipitation events. Repeat surveys provide detailed pre-and post-rainfall measurements of landscape form associated with a range of weather events. The first post-fire precipitation led to sediment delivery equivalent to 0.017 m of erosion from hillslopes and 0.12 m of erosion from colluvial hollows. Volumetrically, 69% of sediment yield was generated from hillslope erosion and 31% was generated from gully channel establishment in colluvial hollows. Processes on hillslopes included erosion by extensive shallow overland flow, formation of rills and gullies, and generation of sediment-laden flows and possibly debris flows. Subsequent smaller rain events caused ongoing hillslope erosion and local deposition and erosion in gullies. Winter freeze-thaw led to soil expansion, likely related to frost-heaving, causing a net centimeter-scale elevation increase across soil-mantled slopes. By characterizing landscape form, the properties of near-surface materials, and measuring both precipitation and landscape change, we can improve our empirical understanding of landscape response to environmental forcing. This detailed approach to studying landscape response to wildfires may be useful in the improvement of predictive models of flood, debris flow and sedimentation hazards used in post-wildfire response assessments and land management, and may help improve process-based models of landscape evolution.

Manufacturing issues which affect coating erosion performance in wind turbine blades

NASA Astrophysics Data System (ADS)

Cortés, E.; Sánchez, F.; Domenech, L.; Olivares, A.; Young, T. M.; O'Carroll, A.; Chinesta, F.

2017-10-01

Erosion damage, caused by repeated rain droplet impact on the leading edges of wind turbine blades, is a major cause for cost concern. Resin Infusion (RI) is used in wind energy blades where low weight and high mechanical performance materials are demanded. The surface coating plays a crucial role in the manufacturing and performance response. The Leading Edge coating is usually moulded, painted or sprayed onto the blade surface so adequate adhesion in the layers' characterization through the thickness is required for mechanical performance and durability reasons. In the current work, an investigation has been directed into the resulting rain erosion durability of the coating was undertaken through a combination of mass loss testing measurements with manufacturing processing parameter variations. The adhesion and erosion is affected by the shock wave caused by the collapsing water droplet on impact. The stress waves are transmitted to the substrate, so microestructural discontinuities in coating layers and interfaces play a key role on its degradation. Standard industrial systems are based on a multilayer system, with a high number of interfaces that tend to accelerate erosion by delamination. Analytical and numerical models are commonly used to relate lifetime prediction and to identify suitable coating and composite substrate combinations and their potential stress reduction on the interface. In this research, the input parameters for the appropriate definition of the Cohesive Zone Modelling (CZM) of the coating-substrate interface are outlined by means of Pull off testing and Peeling testing results. It allowed one to optimize manufacturing and coating process for blades into a knowledge-based guidance for leading edge coating material development. It was achieved by investigating the erosion degradation process using both numerical and laboratory techniques (Pull off, Peeling and Rain Erosion Testing in a whirling arm rain erosion test facility).

Post-wildfire landscape change and erosional processes from repeat terrestrial lidar in a steep headwater catchment, Chiricahua Mountains, Arizona, USA

USGS Publications Warehouse

DeLong, Stephen B.; Youberg, Ann M.; DeLong, Whitney M.; Murphy, Brendan P.

2018-01-01

Flooding and erosion after wildfires present increasing hazard as climate warms, semi-arid lands become drier, population increases, and the urban interface encroaches farther into wildlands. We quantify post-wildfire erosion in a steep, initially unchannelized, 7.5 ha headwater catchment following the 2011 Horseshoe 2 Fire in the Chiricahua Mountains of southeastern Arizona. Using time-lapse cameras, rain gauges, and repeat surveys by terrestrial laser scanner, we quantify the response of a burned landscape to subsequent precipitation events. Repeat surveys provide detailed pre-and post-rainfall measurements of landscape form associated with a range of weather events. The first post-fire precipitation led to sediment delivery equivalent to 0.017 m of erosion from hillslopes and 0.12 m of erosion from colluvial hollows. Volumetrically, 69% of sediment yield was generated from hillslope erosion and 31% was generated from gully channel establishment in colluvial hollows. Processes on hillslopes included erosion by extensive shallow overland flow, formation of rills and gullies, and generation of sediment-laden flows and possibly debris flows. Subsequent smaller rain events caused ongoing hillslope erosion and local deposition and erosion in gullies. Winter freeze-thaw led to soil expansion, likely related to frost-heaving, causing a net centimeter-scale elevation increase across soil-mantled slopes. By characterizing landscape form, the properties of near-surface materials, and measuring both precipitation and landscape change, we can improve our empirical understanding of landscape response to environmental forcing. This detailed approach to studying landscape response to wildfires may be useful in the improvement of predictive models of flood, debris flow and sedimentation hazards used in post-wildfire response assessments and land management, and may help improve process-based models of landscape evolution.

To accrete or not accrete, that is the question

USGS Publications Warehouse

von Huene, Roland E.

1986-01-01

Along modern convergent margins tectonic processes span a spectrum from accretion to erosion. The process of accretion is generally recognized because it leaves a geologic record, whereas the process of erosion is generally hypothetical because it produces a geologic hiatus. Major conditions that determine the dominance of accretion or erosion at modern convergent margins are: 1) rate and direction of plate convergence, 2) sediment supply and type in the trench, and 3) topography of the subducting ocean floor. Most change in structure has been ascribed to plate motion, but both erosion and accretion are observed along the same convergence margin. Thus sediment supply and topography are probably of equivalent importance to plate motion because both erosion and accretion are observed under constant conditions of plate convergence. The dominance of accretion or erosion at a margin varies with the thickness of trench sediment. In a sediment flooded trench, the proportions of subducted and accreted sediment are commonly established by the position of a decollement along a weak horizon in the sediment section. Thus, the vertical variation of sediment strength and the distribution of horizontal stress are important factors. Once deformation begins, the original sediment strength is decreased by sediment remolding and where sediment thickens rapidly, increases in pore fluid pressure can be pronounced. In sediment-starved trenches, where the relief of the subducting ocean floor is not smoothed over, the front of the margin must respond to the topography subducted as well as that accreted. The hypothesized erosion by the drag of positive features against the underside of the upper plate (a high stress environment) may alternate with erosion due to the collapse of a margin front into voids such as graben (a low stress environment). ?? 1986 Ferdinand Enke Verlag Stuttgart.

Effects of low-intensity ultrahigh frequency electromagnetic radiation on inflammatory processes.

PubMed

Lushnikov, K V; Shumilina, Yu V; Yakushina, V S; Gapeev, A B; Sadovnikov, V B; Chemeris, N K

2004-04-01

Low-intensity ultrahigh frequency electromagnetic radiation (42 GHz, 100 microW/cm(2)) reduces the severity of inflammation and inhibits production of active oxygen forms by inflammatory exudate neutrophils only in mice with inflammatory process. These data suggest that some therapeutic effects of electromagnetic radiation can be explained by its antiinflammatory effect which is realized via modulation of functional activity of neutrophils in the focus of inflammation.

Numerical simulation of electromagnetic surface treatment

NASA Astrophysics Data System (ADS)

Sonde, Emmanuel; Chaise, Thibaut; Nelias, Daniel; Robin, Vincent

2018-01-01

Surface treatment methods, such as shot peening or laser shock peening, are generally used to introduce superficial compressive residual stresses in mechanical parts. These processes are carried out during the manufacturing steps or for the purpose of repairing. The compressive residual stresses prevent the initiation and growth of cracks and thus improve the fatigue life of mechanical components. Electromagnetic pulse peening (EMP) is an innovative process that could be used to introduce compressive residual stresses in conductive materials. It acts by generating a high transient electromagnetic field near the working surface. In this paper, the EMP process is presented and a sequentially coupled electromagnetic and mechanical model is developed for its simulation. This 2D axisymmetric model is set up with the commercial finite element software SYSWELD. After description and validation, the numerical model is used to simulate a case of introducing residual stresses of compression in a nickel-based alloy 690 thick sample, by the means of electromagnetic pulses. The results are presented in terms of effective plastic strain and residual mean stress. The influence of the process parameters, such as current intensity and frequency, on the results is analyzed. Finally, the predictability of the process is shown by several correlation studies.

Modeling the reduction in soil loss due to soil armouring caused by rainfall erosion

USDA-ARS?s Scientific Manuscript database

Surface soil properties can change as a result of soil disturbances, erosion, or deposition. One process that can significantly change surface soil properties is soil armouring, which is the selective removal of finer particles by rill or interrill erosion, leaving an armoured layer of coarser parti...

RVR Meander – Migration of meandering rivers in homogeneous and heterogeneous floodplains using physically-based bank erosion

USDA-ARS?s Scientific Manuscript database

The RVR Meander platform for computing long-term meandering-channel migration is presented, together with a method for planform migration based on the modeling of the streambank erosion processes of hydraulic erosion and mass failure. An application to a real-world river, with assumption of homogene...

Erosion processes and prediction in NW U.S. forests

Treesearch

W. J. Elliot; P. R. Robichaud; R. B. Foltz

2011-01-01

The greatest amounts of forest erosion usually follow infrequent wildfires. Sediment from these fires is gradually routed through the stream system. The forest road network is usually the second greatest source of sediment, generating sediment annually. Erosion rates associated with timber harvest, biomass removal, and prescribed fire are generally minimal with current...

Internal erosion during soil pipeflow: state of science for experimental and numerical analysis

USDA-ARS?s Scientific Manuscript database

Many field observations have lead to speculation on the role of piping in embankment failures, landslides, and gully erosion. However, there has not been a consensus on the subsurface flow and erosion processes involved and inconsistent use of terms have exasperated the problem. One such piping proc...

Erosion, sedimentation, and cumulative effects in the Northern Rocky Mountains

Treesearch

Walter F. Megahan; John G. King

2004-01-01

Erosion and sedimentation are natural geomorphic processes characterized by large temporal and spatial variability. Recent radionuclide studies suggest that rare episodic events, such as large wildfires, produce massive sediment yields over time scales of thousands of years, thereby causing long-term average sediment production to exceed present-day average erosion...

Rio Grande Lidar Bank Erosion Monitoring: Preliminary 2007-2008 Results and Survey Design Considerations

DTIC Science & Technology

2010-09-01

was reexposed by erosion following the initial event (Figure 9). Erosion of the fan toe in the vicinity of the downstream array is primarily...Digitally Capture the Topography of Sand Dunes in High Spatial Resolution. Earth Surface Processes and Landforms 29:391-398. Queensland, G. 2008

Erosion of soil organic carbon: implications for carbon sequestration

USGS Publications Warehouse

Van Oost, Kristof; Van Hemelryck, Hendrik; Harden, Jennifer W.; McPherson, B.J.; Sundquist, E.T.

2009-01-01

Agricultural activities have substantially increased rates of soil erosion and deposition, and these processes have a significant impact on carbon (C) mineralization and burial. Here, we present a synthesis of erosion effects on carbon dynamics and discuss the implications of soil erosion for carbon sequestration strategies. We demonstrate that for a range of data-based parameters from the literature, soil erosion results in increased C storage onto land, an effect that is heterogeneous on the landscape and is variable on various timescales. We argue that the magnitude of the erosion term and soil carbon residence time, both strongly influenced by soil management, largely control the strength of the erosion-induced sink. In order to evaluate fully the effects of soil management strategies that promote carbon sequestration, a full carbon account must be made that considers the impact of erosion-enhanced disequilibrium between carbon inputs and decomposition, including effects on net primary productivity and decomposition rates.

Performance Evaluation and Modeling of Erosion Resistant Turbine Engine Thermal Barrier Coatings

NASA Technical Reports Server (NTRS)

Miller, Robert A.; Zhu, Dongming; Kuczmarski, Maria

2008-01-01

The erosion resistant turbine thermal barrier coating system is critical to the rotorcraft engine performance and durability. The objective of this work was to determine erosion resistance of advanced thermal barrier coating systems under simulated engine erosion and thermal gradient environments, thus validating a new thermal barrier coating turbine blade technology for future rotorcraft applications. A high velocity burner rig based erosion test approach was established and a new series of rare earth oxide- and TiO2/Ta2O5- alloyed, ZrO2-based low conductivity thermal barrier coatings were designed and processed. The low conductivity thermal barrier coating systems demonstrated significant improvements in the erosion resistance. A comprehensive model based on accumulated strain damage low cycle fatigue is formulated for blade erosion life prediction. The work is currently aiming at the simulated engine erosion testing of advanced thermal barrier coated turbine blades to establish and validate the coating life prediction models.

A review of physically based models for soil erosion by water

NASA Astrophysics Data System (ADS)

Le, Minh-Hoang; Cerdan, Olivier; Sochala, Pierre; Cheviron, Bruno; Brivois, Olivier; Cordier, Stéphane

2010-05-01

Physically-based models rely on fundamental physical equations describing stream flow and sediment and associated nutrient generation in a catchment. This paper reviews several existing erosion and sediment transport approaches. The process of erosion include soil detachment, transport and deposition, we present various forms of equations and empirical formulas used when modelling and quantifying each of these processes. In particular, we detail models describing rainfall and infiltration effects and the system of equations to describe the overland flow and the evolution of the topography. We also present the formulas for the flow transport capacity and the erodibility functions. Finally, we present some recent numerical schemes to approach the shallow water equations and it's coupling with infiltration and erosion source terms.

Cross-section, velocity, and bedload data at two erosion sites on the Tanana River near Fairbanks, Alaska, 1979

USGS Publications Warehouse

Burrows, Robert L.

1980-01-01

In an effort to relate river processes to vertical and lateral erosion at two sites on the Tanana River in the vicinity of Fairbanks, Alaska, measurements of depth, velocity, and bedload-transport rates were made at several sections at each site. To facilitate comparison of the river processes and ongoing erosion, compilation and graphic presentation of the velocity distributions and bedload-transport rates are presented in conjunction with cross-section configuration immediately adjacent to the area of erosion. Dry sieve analyses of the bedload samples give particle-size distribution. Approximately 85 to 95% of the material in transport at both sites was in the sand range (>0.062 millimeter <2.0 millimeter). (USGS)

Surface Roughness Investigation of Ultrafine-Grained Aluminum Alloy Subjected to High-Speed Erosion

NASA Astrophysics Data System (ADS)

Kazarinov, N. A.; Evstifeev, A. D.; Petrov, Y. V.; Atroshenko, S. A.; Lashkov, V. A.; Valiev, R. Z.; Bondarenko, A. S.

2016-09-01

This study is the first attempt to investigate the influence of severe plastic deformation (SPD) treatment on material surface behavior under intensive erosive conditions. Samples of aluminum alloy 1235 (99.3 Al) before and after high-pressure torsion (HPT) were subjected to intensive erosion by corundum particles accelerated via air flow in a small-scale wind tunnel. Velocity of particles varied from 40 to 200 m/s, while particle average diameter was around 100 μm. Surface roughness measurements provided possibility to compare surface properties of both materials after erosion tests. Moreover, SPD processing appeared to increase noticeably the threshold velocity of the surface damaging process. Additionally, structural analysis of the fracture surfaces of the tested samples was carried out.

Runoff as a factor in USLE/RUSLE technology

NASA Astrophysics Data System (ADS)

Kinnell, Peter

2014-05-01

Modelling erosion for prediction purposes started with the development of the Universal Soil Loss Equation the focus of which was the prediction of long term (~20) average annul soil loss from field sized areas. That purpose has been maintained in the subsequent revision RUSLE, the most widely used erosion prediction model in the world. The lack of ability to predict short term soil loss saw the development of so-called process based models like WEPP and EUROSEM which focussed on predicting event erosion but failed to improve the prediction of long term erosion where the RUSLE worked well. One of the features of erosion recognised in the so-called process based modes is the fact that runoff is a primary factor in rainfall erosion and some modifications of USLE/RUSLE model have been proposed have included runoff as in independent factor in determining event erosivity. However, these models have ignored fundamental mathematical rules. The USLE-M which replaces the EI30 index by the product of the runoff ratio and EI30 was developed from the concept that soil loss is the product of runoff and sediment concentration and operates in a way that obeys the mathematical rules upon which the USLE/RUSLE model was based. In accounts for event soil loss better that the EI30 index where runoff values are known or predicted adequately. RUSLE2 now includes a capacity to model runoff driven erosion.

Modeling and analysis of Soil Erosion processes by the River Basins model: The Case Study of the Krivacki Potok Watershed, Montenegro

NASA Astrophysics Data System (ADS)

Vujacic, Dusko; Barovic, Goran; Mijanovic, Dragica; Spalevic, Velibor; Curovic, Milic; Tanaskovic, Vjekoslav; Djurovic, Nevenka

2016-04-01

The objective of this research was to study soil erosion processes in one of Northern Montenegrin watersheds, the Krivacki Potok Watershed of the Polimlje River Basin, using modeling techniques: the River Basins computer-graphic model, based on the analytical Erosion Potential Method (EPM) of Gavrilovic for calculation of runoff and soil loss. Our findings indicate a low potential of soil erosion risk, with 554 m³ yr-1 of annual sediment yield; an area-specific sediment yield of 180 m³km-2 yr-1. The calculation outcomes were validated for the entire 57 River Basins of Polimlje, through measurements of lake sediment deposition at the Potpec hydropower plant dam. According to our analysis, the Krivacki Potok drainage basin is with the relatively low sediment discharge; according to the erosion type, it is mixed erosion. The value of the Z coefficient was calculated on 0.297, what indicates that the river basin belongs to 4th destruction category (of five). The calculated peak discharge from the river basin was 73 m3s-1 for the incidence of 100 years and there is a possibility for large flood waves to appear in the studied river basin. Using the adequate computer-graphic and analytical modeling tools, we improved the knowledge on the soil erosion processes of the river basins of this part of Montenegro. The computer-graphic River Basins model of Spalevic, which is based on the EPM analytical method of Gavrilovic, is highly recommended for soil erosion modelling in other river basins of the Southeastern Europe. This is because of its reliable detection and appropriate classification of the areas affected by the soil loss caused by soil erosion, at the same time taking into consideration interactions between the various environmental elements such as Physical-Geographical Features, Climate, Geological, Pedological characteristics, including the analysis of Land Use, all calculated at the catchment scale.

Utilising Structure-From-Motion Approaches to Develop a Spatial Understanding of Soil Erosion Processes, in an Experimental Setting.

NASA Astrophysics Data System (ADS)

Benaud, P.; Anderson, K.; Quine, T. A.; James, M. R.; Quinton, J.; Brazier, R. E.

2016-12-01

While total sediment capture can accurately quantify soil loss via water erosion, it isn't practical at the field scale and provides little information on the spatial nature of soil erosion processes. Consequently, high-resolution, remote sensing, point cloud data provide an alternative method for quantifying soil loss. The accessibility of Structure-from-Motion Multi-Stereo View (SfM) and the potential for multi-temporal applications, offers an exciting opportunity to spatially quantify soil erosion. Accordingly, published research provides examples of the successful quantification of large erosion features and events, to centimetre accuracy. Through rigorous control of the camera and image network geometry, the centimetre accuracy achievable at the field scale, can translate to sub-millimetre accuracies within a laboratory environment. Accordingly, this study looks to understand how the ultra-high-resolution spatial information on soil surface topography, derived from SfM, can be integrated with a multi-element sediment tracer to develop a mechanistic understanding of rill and inter-rill erosion, under experimental conditions. A rainfall simulator was used to create three soil surface conditions; compaction and rainsplash, inter-rill erosion, and rill erosion, at two experimental scales (0.15 m2 and 3 m2). Total sediment capture was the primary validation for the experiments, allowing the comparison between structurally and volumetrically derived change, and true soil loss. A Terrestrial Laser Scanner (resolution of ca. 0.8mm) has been employed to assess spatial discrepancies within the SfM data sets and to provide an alternative measure of volumetric change. Preliminary results show the SfM approach used can achieve a ground resolution of less than 0.2 mm per pixel, and a RMSE of less than 0.3 mm. Consequently, it is expected that the ultra-high-resolution SfM point clouds can be utilised to provide a detailed assessment of soil loss via water erosion processes.

Characterization of printed planar electromagnetic coils using digital extrusion and roll-to-roll flexographic processes

NASA Astrophysics Data System (ADS)

Rickard, Scott

Electromagnets are a crucial component in a wide range of more complex electrical devices due to their ability to turn electrical energy into mechanical energy and vice versa. The trend for electronics becoming smaller and lighter has led to increased interest in using flat, planar electromagnetic coils, which have been shown to perform better at scaled down sizes. The two-dimensional geometry of a planar electromagnetic coil yields itself to be produced by a roll-to-roll additive manufacturing process. The emergence of the printed electronics field, which uses traditional printing processes to pattern functional inks, has led to new methods of mass-producing basic electrical components. The ability to print a planar electromagnetic coil using printed electronics could rival the traditional subtractive and semi-subtractive PCB process of manufacturing. The ability to print lightweight planar electromagnetic coils on flexible substrates could lead to their inclusion into intelligent packaging applications and could have specific use in actuating devices, transformers, and electromagnetic induction applications such as energy harvesting or wireless charging. In attempts to better understand the limitations of printing planar electromagnetic coils, the effect that the design parameters of the planar coils have on the achievable magnetic field strength were researched. A comparison between prototyping methods of digital extrusion and manufacturing scale flexographic printing are presented, discussing consistency in the printed coils and their performance in generating magnetic fields. A method to predict the performance of these planar coils is introduced to allow for design within required needs of an application. Results from the research include a demonstration of a printed coil being used in a flat speaker design, working off of actuating principles.

Binary black holes' effects on electromagnetic fields.

PubMed

Palenzuela, Carlos; Anderson, Matthew; Lehner, Luis; Liebling, Steven L; Neilsen, David

2009-08-21

In addition to producing gravitational waves, the dynamics of a binary black hole system could induce emission of electromagnetic radiation by affecting the behavior of plasmas and electromagnetic fields in their vicinity. We here study how the electromagnetic fields are affected by a pair of orbiting black holes through the merger. In particular, we show how the binary's dynamics induce a variability in possible electromagnetically induced emissions as well as a possible enhancement of electromagnetic fields during the late-merge and merger epochs. These time dependent features will likely leave their imprint in processes generating detectable emissions and can be exploited in the detection of electromagnetic counterparts of gravitational waves.

Statistics of rocky coast erosion and percolation theory

NASA Astrophysics Data System (ADS)

Baldassarri, A.; Sapoval, B.

2012-04-01

The dynamics of rocky coasts is an erratic phenomenon featuring numerous small erosion events, but sometimes large dramatic collapses. In this sense, its study should not limit or rely on average erosion rates. Recent studies, based on historical as well as recent data, have indicated that the frequency of magnitude of erosion events display long tail distribution, similar to what observed in landslide. In other words the time evolution of a coast morphology does not enter the classical category of Gaussian process, but rather that of critical systems in physics. We recently proposed a minimal dynamical model of rocky coast erosion which is able to reproduce the diversity of rocky coast morphologies and their dynamics. This model is based on a single, simple ingredient, the retroaction of the coast morphology on the erosive power of the sea. It follows from the idea that erosion can spontaneously create irregular seashores, but, in turn, the geometrical irregularity of the coast participates to the damping of sea-waves, decreasing the average wave amplitude and erosive power. The resulting mutual self-stabilization dynamics of the sea erosion power and coastal irregular morphology leads spontaneously the system to a critical dynamics. Our results indicate then that rocky coast erosion and the statistical theory of percolation are closely related. In this framework, the sometimes fractal geometry of coastlines can be recovered and understood in terms of fractal dimension of the external perimeter of a percolation cluster. From a more practical point of view, the analogy with percolation interfaces means that the coast constitutes a strong, but possibly fragile, barrier to sea erosion, emerging from a self-organised selection process. Accordingly, the effect of a slow weathering degradation of the rocks mechanical properties, as well as other perturbations from natural or human cause, can trigger random and large erosion events difficult to predict and control. To the extent that these ideas apply, natural coasts should be "preserved" and managed with care.

When do glaciated landscapes form?

NASA Astrophysics Data System (ADS)

Koppes, M. N.

2015-12-01

Glacial erosion is a fundamental link between climate and the tectonic and surface processes that create topography. Mountain ranges worldwide have undergone large-scale modification due the erosive action of ice masses, yet the mechanisms that control the timing of this modification and the rate by which ice erodes remain poorly understood. Available data report a wide range of erosion rates from individual ice masses over varying timescales, from the modern to orogenic. Recent numerical modeling efforts have focused on replicating the processes that produce the geomorphic signatures of glacial landscapes. Central to these models is a simple index that relates erosion rate to ice dynamics. To provide a quantitative test of the links between glacial erosion, sliding and ice discharge, we examined explicitly the factors controlling modern glacier erosion rates across climatic regimes, from Patagonia to the Antarctic Peninsula. We find that modern, basin-averaged erosion rates vary by three orders of magnitude, from 1->10 mm yr-1 in Patagonia to 0.01-<0.1 mm yr-1 in the AP, largely as a function of temperature and basal thermal regime. Erosion rates also increase non-linearly with both the sliding speed and the ice flux through the ELA, in accord with theories of glacial erosion. Notably, erosion rates decrease by over two orders of magnitude between temperate and polar glaciers with similar discharge rates. The difference in erosion rates between temperate and colder glaciers of similar shape and size is primarily related to the abundance of meltwater accessing the bed. Since all glaciers worldwide have experienced colder than current climatic conditions, the 100-fold decrease in long-term relative to modern erosion rates may in part reflect the temporal averaging of temperate and polar conditions over the lifecycle of these glaciers. Hence, climatic variation, more than the extent of ice cover or tectonic changes, controls the pace at which glaciers shape mountains.

Soil Production and Erosion Rates and Processes in Mountainous Landscapes

NASA Astrophysics Data System (ADS)

Heimsath, A. M.; DiBiase, R. A.; Whipple, K. X.

2012-12-01

We focus here on high-relief, steeply sloped landscapes from the Nepal Himalaya to the San Gabriels of California that are typically thought to be at a critical threshold of soil cover. Observations reveal that, instead, there are significant areas mantled with soil that fit the conceptual framework of a physically mobile layer derived from the underlying parent material with some locally-derived organic content. The extent and persistence of such soils depends on the long-term balance between soil production and erosion despite the perceived discrepancy between high erosion and low soil production rates. We present cosmogenic Be-10-derived soil production and erosion rates that show that soil production increases with catchment-averaged erosion, suggesting a feedback that enhances soil-cover persistence, even in threshold landscapes. Soil production rates do decline systematically with increasing soil thickness, but hint at the potential for separate soil production functions for different erosional regimes. We also show that a process transistion to landslide-dominated erosion results in thinner, patchier soils and rockier topography, but find that there is no sudden transition to bedrock landscapes. Our landslide modeling is combined with a detailed quantification of bedrock exposure for these steep, mountainous landscapes. We also draw an important conclusion connecting the physical processes producing and transporting soil and the chemical processes weathering the parent material by measuring parent material strength across three different field settings. We observe that parent material strength increases with overlying soil thickness and, therefore, the weathered extent of the saprolite. Soil production rates, thus, decrease with increasing parent material competence. These observation highlight the importance of quantifying hillslope hydrologic processes where such multi-facted measurements are made.

Land use and surface process domains on alpine hillslopes

NASA Astrophysics Data System (ADS)

Kuhn, Nikolaus J.; Caviezel, Chatrina; Hunziker, Matthias

2015-04-01

Shrubs and trees are generally considered to protect hillslopes from erosion. As a consequence, shrub encroachment on mountain pastures after abandoning grazing is not considered a threat to soils. However, the abandonment of mown or grazed grasslands causes a shift in vegetation composition and thus a change in landscape ecology and geomorphology. On many alpine slopes, current changes in land use and vegetation cover are accompanied by climate change, potentially generating a new geomorphic regime. Most of the debate focuses on the effect of land abandonment on water erosion rates. Generally, an established perennial vegetation cover improves the mechanical anchoring of the soil and the regulation of the soil water budget, including runoff generation and erosion. However, changing vegetation composition affects many other above- and below-ground properties like root density, -diversity and -geometry, soil structure, pore volume and acidity. Each combination of these properties can lead to a distinct scenario of dominating surface processes, often not reflected by common erosion risk assessment procedures. The study of soil properties along a chronosequence of green alder (alnusviridis) encroachment on the Unteralptal in central Switzerland reveals that shrub encroachment changes soil and vegetation properties towards an increase of resistance to run-off related erosion processes, but a decrease of slope stability against shallow landslides. The latter are a particular threat because of the currently increasing frequency of slide-triggering high magnitude rainfalls. The potential change of process domain on alpine pastures highlights the need for a careful use of erosion models when assessing future land use and climate scenarios. In mountains, but also other intensively managed agricultural landscapes, risk assessment without the appropriate reflection on the shifting relevance of surface processes carries the risk of missing future threats to environmental quality, services and hazards.

Analysing the spatial patterns of erosion scars using point process theory at the coastal chalk cliff of Mesnil-Val, (Normandy, Northern France)

NASA Astrophysics Data System (ADS)

Rohmer, J.; Dewez, D.

2014-09-01

Over the last decade, many cliff erosion studies have focused on frequency-size statistics using inventories of sea cliff retreat sizes. By comparison, only a few paid attention to quantifying the spatial and temporal organisation of erosion scars over a cliff face. Yet, this spatial organisation carries essential information about the external processes and the environmental conditions that promote or initiate sea-cliff instabilities. In this article, we use summary statistics of spatial point process theory as a tool to examine the spatial and temporal pattern of a rockfall inventory recorded with repeated terrestrial laser scanning surveys at the chalk coastal cliff site of Mesnil-Val (Normandy, France). Results show that: (1) the spatial density of erosion scars is specifically conditioned alongshore by the distance to an engineered concrete groin, with an exponential-like decreasing trend, and vertically focused both at wave breaker height and on strong lithological contrasts; (2) small erosion scars (10-3-10-2 m3) aggregate in clusters within a radius of 5 to 10 m, which suggests some sort of attraction or focused causative process, and disperse above this critical distance; (3) on the contrary, larger erosion scars (10-2-101 m3) tend to disperse above a radius of 1 to 5 m, possibly due to the spreading of successive failures across the cliff face; (4) large scars significantly occur albeit moderately, where previous large rockfalls have occurred during preceeding winter; (5) this temporal trend is not apparent for small events. In conclusion, this study shows, with a worked example, how spatial point process summary statistics are a tool to test and quantify the significance of geomorphological observation organisation.

Analysing the spatial patterns of erosion scars using point process theory at the coastal chalk cliff of Mesnil-Val, Normandy, northern France

NASA Astrophysics Data System (ADS)

Rohmer, J.; Dewez, T.

2015-02-01

Over the last decade, many cliff erosion studies have focused on frequency-size statistics using inventories of sea cliff retreat sizes. By comparison, only a few paid attention to quantifying the spatial and temporal organisation of erosion scars over a cliff face. Yet, this spatial organisation carries essential information about the external processes and the environmental conditions that promote or initiate sea-cliff instabilities. In this article, we use summary statistics of spatial point process theory as a tool to examine the spatial and temporal pattern of a rockfall inventory recorded with repeated terrestrial laser scanning surveys at the chalk coastal cliff site of Mesnil-Val (Normandy, France). Results show that: (1) the spatial density of erosion scars is specifically conditioned alongshore by the distance to an engineered concrete groyne, with an exponential-like decreasing trend, and vertically focused both at wave breaker height and on strong lithological contrasts; (2) small erosion scars (10-3 to 10-2 m3) aggregate in clusters within a radius of 5 to 10 m, which suggests some sort of attraction or focused causative process, and disperse above this critical distance; (3) on the contrary, larger erosion scars (10-2 to 101 m3) tend to disperse above a radius of 1 to 5 m, possibly due to the spreading of successive failures across the cliff face; (4) large scars significantly occur albeit moderately, where previous large rockfalls have occurred during preceding winter; (5) this temporal trend is not apparent for small events. In conclusion, this study shows, with a worked example, how spatial point process summary statistics are a tool to test and quantify the significance of geomorphological observation organisation.

Graffiti for science: Qualitative detection of erosional patterns through bedrock erosion painting

NASA Astrophysics Data System (ADS)

Beer, Alexander R.; Kirchner, James W.; Turowski, Jens M.

2016-04-01

Bedrock erosion is a crucial constraint on stream channel incision, and hence whole landscape evolution, in steep mountainous terrain and tectonically active regions. Several interacting processes lead to bedrock erosion in stream channels, with hydraulic shear detachment, plucking, and abrasion due to sediment impacts generally being the most efficient. Bedrock topography, together with the sediment tools and cover effects, regulate the rate and spatial pattern of in situ surface change. Measurements of natural bedrock erosion rates are valuable for understanding the underlying process physics, as well as for modelling landscape evolution and designing engineered structures. However, quantifying spatially distributed bedrock erosion rates in natural settings is challenging and few such measurements exist. We studied spatial bedrock erosion in a 30m-long bedrock gorge in the Gornera, a glacial meltwater stream above Zermatt. This stream is flushed episodically with sediment-laden streamflow due to hydropower operations upstream, with negligible discharge in the gorge in between these flushing events. We coated several bedrock surface patches with environmentally safe, and water-insoluble outdoor paint to document the spatial pattern of surface abrasion, or to be more precise, to document its driving forces. During four consecutive years, the change of the painted areas was recorded repeatedly with photographs before the painting was renewed. These photographs visually documented the spatial patterns of vertical erosion (channel incision), of lateral erosion (channel widening) and of downstream-directed erosion (channel clearance). The observed qualitative patterns were verified through comparison to quantitative change detection analyses based on annual high-resolution terrestrial laser scanning surveys of the bedrock surfaces. Comparison of repeated photographs indicated a temporal cover effect and a general height limit of the tools effect above the streambed during flushing events. Further, the photographs clearly show the erosional development of a UFCS (upstream-facing convex surface) feature with an upstream-facing surface full of impact marks, a sharp crest-line, and an adjacent downstream-facing surface preserved from sediment impacts. This pilot study documents that bedrock erosion painting provides an easy, cost-efficient and clear qualitative method for detecting the spatial distribution of bedrock erosion and inferring its controlling factors. Our results show that the susceptibility of a painted surface to abrasion is controlled by its position in the channel and its spatial orientation relative to the sediment-laden flow. Erosion painting is a scientifically useful form of graffiti that could be widely applied in both natural and laboratory settings, providing insight into patterns and processes of erosion.

Electromagnetic containerless processing requirements and recommended facility concept and capabilities for space lab

NASA Technical Reports Server (NTRS)

Frost, R. T.; Bloom, H. L.; Napaluch, L. J.; Stockhoff, E. H.; Wouch, G.

1974-01-01

Containerless melting, reaction, and solidification experiments and processes which potentially can lead to new understanding of material science and production of new or improved materials in the weightless space environment are reviewed in terms of planning for spacelab. Most of the experiments and processes discussed are amenable to the employment of electromagnetic position control and electromagnetic induction or electron beam heating and melting. The spectrum of relevant properties of materials, which determine requirements for a space laboratory electromagnetic containerless processing facility are reviewed. Appropriate distributions and associated coil structures are analyzed and compared on the basis of efficiency, for providing the functions of position sensing, control, and induction heating. Several coil systems are found capable of providing these functions. Exchangeable modular coils in appropriate sizes are recommended to achieve the maximum power efficiencies, for a wide range of specimen sizes and resistivities, in order to conserve total facility power.

Solid particle impingement erosion characteristics of cylindrical surfaces, pre-existing holes and slits

NASA Technical Reports Server (NTRS)

Rao, P. V.; Buckley, D. H.

1983-01-01

The erosion characteristics of aluminum cylinders sand-blasted with both spherical and angular erodent particles were studied and compared with results from previously studied flat surfaces. The cylindrical results are discussed with respect to impact conditions. The relationship between erosion rate and pit morphology (width, depth, and width to depth ratio) is established. The aspects of (1) erosion rate versus time curves on cylindrical surfaces; (2) long-term exposures; and (3) erosion rate versus time curves with spherical and angular particles are presented. The erosion morphology and characteristics of aluminum surfaces with pre-existing circular cylindrical and conical holes of different sizes were examined using weight loss measurements, scanning electron microscopy, a profilometer, and a depth gage. The morphological features (radial and concentric rings) are discussed with reference to flat surfaces, and the erosion features with spherical microglass beads. The similarities and differences of erosion and morphological features are highlighted. The erosion versus time curves of various shapes of holes are discussed and are compared with those of a flat surface. The erosion process at slits is considered.

Electromagnetic Evidence of Altered Visual Processing in Autism

ERIC Educational Resources Information Center

Neumann, Nicola; Dubischar-Krivec, Anna M.; Poustka, Fritz; Birbaumer, Niels; Bolte, Sven; Braun, Christoph

2011-01-01

Individuals with autism spectrum disorder (ASD) demonstrate intact or superior local processing of visual-spatial tasks. We investigated the hypothesis that in a disembedding task, autistic individuals exhibit a more local processing style than controls, which is reflected by altered electromagnetic brain activity in response to embedded stimuli…

The consequences of land-cover changes on soil erosion distribution in Slovakia

NASA Astrophysics Data System (ADS)

Cebecauer, Tomáš; Hofierka, Jaroslav

2008-06-01

Soil erosion is a complex process determined by mutual interaction of numerous factors. The aim of erosion research at regional scales is a general evaluation of the landscape susceptibility to soil erosion by water, taking into account the main factors influencing this process. One of the key factors influencing the susceptibility of a region to soil erosion is land cover. Natural as well as human-induced changes of landscape may result in both the diminishment and acceleration of soil erosion. Recent studies of land-cover changes indicate that during the last decade more than 4.11% of Slovak territory has changed. The objective of this study is to assess the influence of land-cover and crop rotation changes over the 1990-2000 period on the intensity and spatial pattern of soil erosion in Slovakia. The assessment is based on principles defined in the Universal Soil Loss Equation (USLE) modified for application at regional scale and the use of the CORINE land cover (CLC) databases for 1990 and 2000. The C factor for arable land has been refined using statistical data on the mean crop rotation and the acreage of particular agricultural crops in the districts of Slovakia. The L factor has been calculated using sample areas with parcels identified by LANDSAT TM data. The results indicate that the land-cover and crop rotation changes had a significant influence on soil erosion pattern predominately in the hilly and mountainous parts of Slovakia. The pattern of soil erosion changes exhibits high spatial variation with overall slightly decreased soil erosion risks. These changes are associated with ongoing land ownership changes, changing structure of crops, deforestation and afforestation.

Vegetation canopy cover effects on sediment erosion processes in the upper Colorado River Basin mancos shale formation, Price, Utah

USDA-ARS?s Scientific Manuscript database

This study provides new parameterizations for applying the Rangeland Hydrology and Erosion Model (RHEM) on the highly erosive, rangeland saline soils of the Mancos Shale formation in the Price-San Rafael River Basin in east central Utah. Calibrated hydrologic parameters (Kss and K') values are gener...

Erosion processes and prediction with WEPP technology in forests in the Northwestern U.S.

Treesearch

W. J. Elliot

2013-01-01

In the northwestern U.S., the greatest amounts of forest erosion usually follow infrequent wildfires. Sediment from these fires is gradually routed through the stream system. The forest road network is usually the second greatest source of sediment, generating sediment annually. Erosion rates associated with timber harvest, biomass removal, and prescribed fire are...

Erosion at decommissioned road-stream crossings: case studies from three northern California watersheds

Treesearch

Sam A. Flanagan; David Fuller; Leonard Job; Sam Morrison

2012-01-01

Post-treatment erosion was observed for 41 decommissioned road stream crossings in three northern California watersheds. Sites were purposefully selected in order to characterize the nature and range of post-treatment erosional responses. Sites with the highest visible erosion were selected in order to better understand the dominant process and incorporate any...

Enhancements to the Water Erosion Prediction Project (WEPP) for modeling large snow-dominated mountainous forest watersheds

Treesearch

Anurag Srivastava; Joan Q. Wu; William J. Elliot; Erin S. Brooks

2015-01-01

The Water Erosion Prediction Project (WEPP) model, originally developed for hillslope and small watershed applications, simulates complex interactive processes influencing erosion. Recent incorporations to the model have improved the subsurface hydrology components for forest applications. Incorporation of channel routing has made the WEPP model well suited for large...

Prescribed fire effects on runoff, erosion, and soil water repellency on steeply-sloped sagebrush rangeland over a five year period

USDA-ARS?s Scientific Manuscript database

Fire is an inherent component of sagebrush steppe rangelands in western North America and can dramatically affect runoff and erosion processes. Post-fire flooding and erosion events pose substantial threats to proximal resources, property, and human life. Yet, prescribed fire can serve as a tool to ...

Coupling of phenological information and simulated vegetation index time series: Limitations and potentials for the assessment and monitoring of soil erosion risk

USDA-ARS?s Scientific Manuscript database

Monitoring of agricultural used soils at frequent intervals is needed to get a sufficient understanding of soil erosion processes. This is crucial to support decision making and refining soil policies especially in the context of climate change. Along with rainfall erosivity, soil coverage by vegeta...

Recent findings related to measuring and modeling forest road erosion

Treesearch

W. J. Elliot; R. B. Foltz; P. R. Robichaud

2009-01-01

Sediment is the greatest pollutant of forest streams. In the absence of wildfire, forest road networks are usually the main source of sediment in forest watersheds. An understanding of forest road erosion processes is important to aid in predicting sediment delivery from roads to streams. The flowpath followed by runoff is the key to understanding road erosion...

A physically-based channel-modeling framework integrating HEC-RAS sediment transport capabilities and the USDA-ARS bank-stability and toe-erosion model (BSTEM)

USDA-ARS?s Scientific Manuscript database

Classical, one-dimensional, mobile bed, sediment-transport models simulate vertical channel adjustment, raising or lowering cross-section node elevations to simulate erosion or deposition. This approach does not account for bank erosion processes including toe scour and mass failure. In many systems...

Towards estimates of future rainfall erosivity in Europe based on REDES and WorldClim datasets

NASA Astrophysics Data System (ADS)

Panagos, Panos; Ballabio, Cristiano; Meusburger, Katrin; Spinoni, Jonathan; Alewell, Christine; Borrelli, Pasquale

2017-05-01

The policy requests to develop trends in soil erosion changes can be responded developing modelling scenarios of the two most dynamic factors in soil erosion, i.e. rainfall erosivity and land cover change. The recently developed Rainfall Erosivity Database at European Scale (REDES) and a statistical approach used to spatially interpolate rainfall erosivity data have the potential to become useful knowledge to predict future rainfall erosivity based on climate scenarios. The use of a thorough statistical modelling approach (Gaussian Process Regression), with the selection of the most appropriate covariates (monthly precipitation, temperature datasets and bioclimatic layers), allowed to predict the rainfall erosivity based on climate change scenarios. The mean rainfall erosivity for the European Union and Switzerland is projected to be 857 MJ mm ha-1 h-1 yr-1 till 2050 showing a relative increase of 18% compared to baseline data (2010). The changes are heterogeneous in the European continent depending on the future projections of most erosive months (hot period: April-September). The output results report a pan-European projection of future rainfall erosivity taking into account the uncertainties of the climatic models.

Towards estimates of future rainfall erosivity in Europe based on REDES and WorldClim datasets.

PubMed

Panagos, Panos; Ballabio, Cristiano; Meusburger, Katrin; Spinoni, Jonathan; Alewell, Christine; Borrelli, Pasquale

2017-05-01

The policy requests to develop trends in soil erosion changes can be responded developing modelling scenarios of the two most dynamic factors in soil erosion, i.e. rainfall erosivity and land cover change. The recently developed Rainfall Erosivity Database at European Scale (REDES) and a statistical approach used to spatially interpolate rainfall erosivity data have the potential to become useful knowledge to predict future rainfall erosivity based on climate scenarios. The use of a thorough statistical modelling approach (Gaussian Process Regression), with the selection of the most appropriate covariates (monthly precipitation, temperature datasets and bioclimatic layers), allowed to predict the rainfall erosivity based on climate change scenarios. The mean rainfall erosivity for the European Union and Switzerland is projected to be 857 MJ mm ha -1  h -1  yr -1 till 2050 showing a relative increase of 18% compared to baseline data (2010). The changes are heterogeneous in the European continent depending on the future projections of most erosive months (hot period: April-September). The output results report a pan-European projection of future rainfall erosivity taking into account the uncertainties of the climatic models.

Erosion of a grooved surface caused by impact of particle-laden flow

NASA Astrophysics Data System (ADS)

Jung, Sohyun; Yang, Eunjin; Kim, Ho-Young

2016-11-01

Solid erosion can be a life-limiting process for mechanical elements in erosive environments, thus it is of practical importance in many industries such as construction, mining, and coal conversion. Erosion caused by particle-laden flow occurs through diverse mechanisms, such as cutting, plastic deformation, brittle fracture, fatigue and melting, depending on particle velocity, total particle mass and impingement angle. Among a variety of attempts to lessen erosion, here we investigate the effectiveness of millimeter-sized grooves on the surface. By experimentally measuring the erosion rates of smooth and triangular-grooved surfaces under various impingement angles, we find that erosion can be significantly reduced within a finite range of impingement angles. We show that such erosion resistance is attributed to the swirls of air within grooves and the differences in erosive strength of normal and slanted impact. In particular, erosion is mitigated when we increase the effective area under normal impact causing plastic deformation and fracture while decreasing the area under slanted impact that cuts the surface to a large degree. Our quantitative model for the erosion rate of grooved surfaces considering the foregoing effects agrees with the measurement results.

Particle simulation of electromagnetic emissions from electrostatic instability driven by an electron ring beam on the density gradient

NASA Astrophysics Data System (ADS)

Horký, Miroslav; Omura, Yoshiharu; Santolík, Ondřej

2018-04-01

This paper presents the wave mode conversion between electrostatic and electromagnetic waves on the plasma density gradient. We use 2-D electromagnetic code KEMPO2 implemented with the generation of density gradient to simulate such a conversion process. In the dense region, we use ring beam instability to generate electron Bernstein waves and we study the temporal evolution of wave spectra, velocity distributions, Poynting flux, and electric and magnetic energies to observe the wave mode conversion. Such a conversion process can be a source of electromagnetic emissions which are routinely measured by spacecraft on the plasmapause density gradient.

Influence of electromagnetic field on soliton-mediated charge transport in biological systems.

PubMed

Brizhik, Larissa

2015-01-01

It is shown that electromagnetic fields affect dynamics of Davydov's solitons which provide charge transport processes in macromolecules during metabolism of the system. There is a resonant frequency of the field at which it can cause the transition of electrons from bound soliton states into delocalised states. Such decay of solitons reduces the effectiveness of charge transport, and, therefore, inhibits redox processes. Solitons radiate their own electromagnetic field of characteristic frequency determined by their average velocity. This self-radiated field leads to synchronization of soliton dynamics and charge transport processes, and is the source of the coherence in the system. Exposition of the system to the oscillating electromagnetic field of the frequency, which coincides with the eigen-frequency of solitons can enhance eigen-radiation of solitons, and, therefore, will enhance synchronization of charge transpor, stimulate the redox processes and increase coherence in the system. Electromagnetic oscillating field causes also ratchet phenomenon of solitons, i.e., drift of solitons in macromolecules in the presence of unbiased periodic field. Such additional drift enhances the charge transport processes. It is shown that temperature facilitates the ratchet drift. In particular, temperature fluctuations lead to the lowering of the critical value of the intensity and period of the field, above which the drift of solitons takes place. Moreover, there is a stochastic resonance in the soliton dynamics in external electromagnetic fields. This means, that there is some optimal temperature at which the drift of solitons is maximal.

Smart Rocks for Bridge Scour Monitoring: Design and Localization Using Electromagnetic Techniques and Embedded Orientation Sensors

NASA Astrophysics Data System (ADS)

Radchenko, Andro

River bridge scour is an erosion process in which flowing water removes sediment materials (such as sand, rocks) from a bridge foundation, river beds and banks. As a result, the level of the river bed near a bridge pier is lowering such that the bridge foundation stability can be compromised, and the bridge can collapse. The scour is a dynamic process, which can accelerate rapidly during a flood event. Thus, regular monitoring of the scour progress is necessary to be performed at most river bridges. Present techniques are usually expensive, require large man/hour efforts, and often lack the real-time monitoring capabilities. In this dissertation a new method--'Smart Rocks Network for bridge scour monitoring' is introduced. The method is based on distributed wireless sensors embedded in ground underwater nearby the bridge pillars. The sensor nodes are unconstrained in movement, are equipped with years-lasting batteries and intelligent custom designed electronics, which minimizes power consumption during operation and communication. The electronic part consists of a microcontroller, communication interfaces, orientation and environment sensors (such as are accelerometer, magnetometer, temperature and pressure sensors), supporting power supplies and circuitries. Embedded in the soil nearby a bridge pillar the Smart Rocks can move/drift together with the sediments, and act as the free agent probes transmitting the unique signature signals to the base-station monitors. Individual movement of a Smart Rock can be remotely detected processing the orientation sensors reading. This can give an indication of the on-going scour progress, and set a flag for the on-site inspection. The map of the deployed Smart Rocks Network can be obtained utilizing the custom developed in-network communication protocol with signals intensity (RSSI) analysis. Particle Swarm Optimization (PSO) is applied for map reconstruction. Analysis of the map can provide detailed insight into the scour progress and topology. Smart Rocks Network wireless communication is based on the magnetoinductive (MI) link, at low (125 KHz) frequency, allowing for signal to penetrate through the water, rocks, and the bridge structure. The dissertation describes the Smart Rocks Network implementation, its electronic design and the electromagnetic/computational intelligence techniques used for the network mapping.

In-situ erosion of cohesive sediment in a large shallow lake experiencing long-term decline in wind speed

NASA Astrophysics Data System (ADS)

Wu, Tingfeng; Timo, Huttula; Qin, Boqiang; Zhu, Guangwei; Janne, Ropponen; Yan, Wenming

2016-08-01

In order to address the major factors affecting cohesive sediment erosion using high-frequency in-situ observations in Lake Taihu, and the response of this erosion to long-term decline in wind speed, high-frequency meteorological, hydrological and turbidity sensors were deployed to record continuous field wind-induced wave, current and sediment erosion processes; Statistical analyses and mathematic modeling spanning 44 years were also conducted. The results revealed that the unconsolidated surficial cohesive sediment frequently experiences the processes of erosion, suspension and deposition. Wind waves, generated by the absorption of wind energy, are the principal force driving this cycle. When the wavelength-to-water depth ratio (L/D) is 2-3, wave propagation is affected by lakebed friction and surface erosion occurs. When L/D > 3, the interaction between wave and lakebed increases to induce massive erosion. However, influenced by rapid urbanization in the Lake Taihu basin, wind speed has significantly decreased, by an average rate of -0.022 m s-1 a-1, from 1970 to 2013. This has reduced the erodible area, represented by simulated L/D, at a rate of -16.9 km2 a-1 in the autumn and winter, and -8.1 km2 a-1 in the spring and summer. This significant decrease in surface erosion area, and the near disappearance of areas experiencing massive erosion, imply that Lake Taihu has become calmer, which can be expected to have adverse effects on the lake ecosystem by increasing eutrophication and nuisance cyanobacteria blooms.

Detecting Anthropogenic Disturbance on Weathering and Erosion Processes

NASA Astrophysics Data System (ADS)

Vanacker, V.; Schoonejans, J.; Bellin, N.; Ameijeiras-Mariño, Y.; Opfergelt, S.; Christl, M.

2014-12-01

Anthropogenic disturbance of natural vegetation can profoundly alter the physical, chemical and biological processes within soils. Rapid removal of topsoil during intense farming can result in an imbalance between soil production through chemical weathering and physical erosion, with direct implications on local biogeochemical cycling. However, the feedback mechanisms between soil erosion, chemical weathering and biogeochemical cycling in response to anthropogenic forcing are not yet fully understood. In this paper, we analyze dynamic soil properties for a rapidly changing anthropogenic landscape in the Spanish Betic Cordillera; and focus on the coupling between physical erosion, soil production and soil chemical weathering. Modern erosion rates were quantified through analysis of sediment deposition volumes behind check dams, and represent catchment-average erosion rates over the last 10 to 50 years. Soil production rates are derived from in-situ produced 10Be nuclide concentrations, and represent long-term flux rates. In each catchment, soil chemical weathering intensities were calculated for two soil-regolith profiles. Although Southeast Spain is commonly reported as the European region that is most affected by land degradation, modern erosion rates are low (140 t ha-1 yr-1). About 50 % of the catchments are losing soils at a rate of less than 60 t km-2 yr-1. Our data show that modern erosion rates are roughly of the same magnitude as the long-term or cosmogenically-derived erosion rates in the Betic Cordillera. Soils developed on weathered metamorphic rocks have no well-developed profile characteristics, and are generally thin and stony. Nevertheless, soil chemical weathering intensities are high; and question the occurrence of past soil truncation.

Modeling of soil erosion and sediment transport in the East River Basin in southern China

USGS Publications Warehouse

Wu, Yping; Chen, Ji

2012-01-01

Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide.

Topographic changes detection through Structure-from-Motion in agricultural lands affected by erosion processes

NASA Astrophysics Data System (ADS)

Prosdocimi, Massimo; Pradetto Sordo, Nicoletta; Burguet, Maria; Di Prima, Simone; Terol Esparza, Enric; Tarolli, Paolo; Cerdà, Artemi

2016-04-01

Throughout the world, soil erosion by water is a serious problem, especially in semi-arid and semi-humid areas (Cerdà et al., 2009; Cerdan et al., 2010; García-Ruiz, 2010). Although soil erosion by water consists of physical processes that vary significantly in severity and frequency according to when and where they occur, they are also strongly influenced by anthropic factors such as land-use changes on large scales and unsustainable farming practices (Boardman et al., 1990; Cerdà 1994; Montgomery, 2007). Tillage operations, combined with weather conditions, are recognized to primarily influence soil erosion rates. If, on one hand, tillage operations cause uniform changes based on the tool used, on the other, weather conditions, such as rainfalls, produce more random changes, less easily traceable (Snapir et al., 2014). Within this context, remote-sensing technologies can facilitate the detection and quantification of these topographic changes. In particular, a real opportunity and challenge is offered by the low-cost and flexible photogrammetric technique, called 'Structure-from-Motion' (SfM), combined with the use of smartphones (Micheletti et al., 2014; Prosdocimi et al., 2015). This represents a significant advance compared with more expensive technologies and applications (e.g. Terrestrial Laser Scanner - TLS) (Tarolli, 2014). This work wants to test the Structure from Motion to obtain high-resolution topography for the detection of topographic changes in agricultural lands affected by erosion processes. Two case studies were selected: i) a tilled plot characterized by bare soil and affected by rill erosion located in the hilly countryside of Marche region (central Italy), and ii) a Mediterranean vineyard located within the province of Valencia (south eastern Spain) where rainfall simulation experiments were carried out. Extensive photosets were obtained by using one standalone reflex digital camera and one smartphone built-in digital camera. Digital Terrain Models (DTMs) derived from the smartphone reveled to be comparable to DTMs derived from the reflex camera. The results underlined the effectiveness of SfM for detecting topographic changes in agricultural lands affected by erosion processes, even when pictures are taken from a smartphone. This methodology could be very useful for farmers and/or technician for post-event analyses of erosion processes to implement technical measures to mitigate the problem of soil erosion by water. Acknowledgements The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 603498 (RECARE project) References Boardman, J., Foster, I.D.L., Dearing, J.A., 1990. Soil Erosion on Agricultural Land. John Wiley and Sons Ltd., Chichester. Cerdà, A., 1994. The response of abandoned terraces to simulated rain, in: Rickson, R.J., (Ed.), Conserving Soil Resources: European Perspective, CAB International, Wallingford, pp. 44-55. Cerdà, A., Flanagan, D.C., Le Bissonnais, Y., Boardman, J., 2009. Soil erosion and agriculture. Soil & Tillage Research 106, 107-108. Cerdan, O., Govers, G., Le Bissonnais, Y., Van Oost, K., Poesen, J., Saby, N., Gobin, A., Vacca, A., Quinton, J., Auerwald, K., Klik, A., Kwaad, F.J.P.M., Raclot, D., Ionita, I., Rejman, J., Rousseva, S., Muxart, T., Roxo, M.J., Dostal, T., 2010. Rates and spatial variations of soil erosion in Europe: A study based on erosion plot data. Geomorphology 122, 167-177. Garcìa-Ruiz, J.M., 2010. The effects of land uses on soil erosion in Spain: A review. Catena 81, 1-11. Micheletti, N., Chandler, J.H., Lane, S.N., 2014. Investigating the geomorphological potential of freely available and accessible Structure-from-Motion photogrammetry using a smartphone. Earth Surface Processes and Landforms 40(4), 473-486. DOI: 10.1002/esp.3648 Montgomery, D.R., 2007. Soil erosion and agricultural sustainability. PNAS 104, 13268-13272. Prosdocimi, M., Calligaro, S., Sofia, G., Dalla Fontana, G., Tarolli, P., 2015. Bank rosion in agricultural drainage networks: new challenges from structure-from-motion photogrammetry for post-event analysis. Earth Surface Prosses and Landform 40(14), 1891-1906. DOI: 10.1002/esp.3767. Snapir, B., Hobbs, S., Waine, T.W., 2014. Roughness measurements over an agricultural soil surface with Structure from Motion. ISPRS Journal of Photogrammetry and Remote Sensing 96, 210-223. Tarolli, P., 2014. High-resolution topography for understanding Earth surface processes: opportunities and challenges. Geomorphology 216, 295-312.

The role of bank collapse on tidal creek ontogeny: A novel process-based model for bank retreat

NASA Astrophysics Data System (ADS)

Gong, Zheng; Zhao, Kun; Zhang, Changkuan; Dai, Weiqi; Coco, Giovanni; Zhou, Zeng

2018-06-01

Bank retreat in coastal tidal flats plays a primary role on the planimetric shape of tidal creeks and is commonly driven by both flow-induced bank erosion and gravity-induced bank collapse. However, existing modelling studies largely focus on bank erosion and overlook bank collapse. We build a bank retreat model coupling hydrodynamics, bank erosion and bank collapse. To simulate the process of bank collapse, a stress-deformation model is utilized to calculate the stress variation of bank soil after bank erosion, and the Mohr-Coulomb failure criterion is then applied to evaluate the stability of the tidal creek bank. Results show that the bank failure process can be categorized into three stages, i.e., shear failure at the bank toe (stage I), tensile failure on the bank top (stage II), and sectional cracking from the bank top to the toe (stage III). With only bank erosion, the planimetric shapes of tidal creeks are funneled due to the gradually seaward increasing discharge. In contrast to bank erosion, bank collapse is discontinuous, and the contribution of bank collapse to bank retreat can reach 85%, highlighting that the expansion of tidal creeks can be dominated by bank collapse process. The planimetric shapes of tidal creeks are funneled with a much faster expansion rate when bank collapse is considered. Overall, this study makes a further step toward more physical and realistic simulation of bank retreat in estuarine and coastal settings and the developed bank collapse module can be readily included in other morphodynamic models.

Electromagnetic bonding of plastics to aluminum

NASA Technical Reports Server (NTRS)

Sheppard, A. T.; Silbert, L.

1980-01-01

Electromagnetic curing is used to bond strain gage to aluminum tensile bar. Electromagnetic energy heats only plastic/metal interface by means of skin effect, preventing degradation of heat-treated aluminum. Process can be easily applied to other metals joined by high-temperature-curing plastic adhesives.

WEPP Model applications for evaluations of best management practices

Treesearch

D. C. Flanagan; W. J. Elliott; J. R. Frankenberger; C. Huang

2010-01-01

The Water Erosion Prediction Project (WEPP) model is a process-based erosion prediction technology for application to small watersheds and hillslope profiles, under agricultural, forested, rangeland, and other land management conditions. Developed by the United States Department of Agriculture (USDA) over the past 25 years, WEPP simulates many of the physical processes...

Design, construction and calibration of a portable boundary layer wind tunnel for field use

USDA-ARS?s Scientific Manuscript database

Wind tunnels have been used for several decades to study wind erosion processes. Portable wind tunnels offer the advantage of testing natural surfaces in the field, but they must be carefully designed to insure that a logarithmic boundary layer is formed and that wind erosion processes may develop ...

Radionuclides in Soils Along a Mountain-Basin Transect in the Koratepa Mountains of Uzbekistan

USDA-ARS?s Scientific Manuscript database

Wind tunnels have been used for several decades to study wind erosion processes. Portable wind tunnels offer the advantage of testing natural surfaces in the field, but they must be carefully designed to insure that a logarithmic boundary layer is formed and that wind erosion processes may develop ...

Impacts of fire on hydrology and erosion in steep mountain big sagebrush communities

Treesearch

Frederick B. Pierson; Peter R. Robichaud; Kenneth E. Spaeth; Corey A. Moffet

2003-01-01

Wildfire is an important ecological process and management issue on western rangelands. Major unknowns associated with wildfire are its affects on vegetation and soil conditions that influence hydrologic processes including infiltration, surface runoff, erosion, sediment transport, and flooding. Post wildfire hydrologic response was studied in big sagebrush plant...

Structural and functional connectivity as a driver of hillslope erosion following disturbance

Treesearch

C. Jason Williams; Frederick B. Pierson; Pete Robichaud; Osama Z. Al-Hamdan; Jan Boll; Eva K. Strand

2016-01-01

Hydrologic response to rainfall on fragmented or burnt hillslopes is strongly influenced by the ensuing connectivity of runoff and erosion processes. Yet cross-scale process connectivity is seldom evaluated in field studies owing to scale limitations in experimental design. This study quantified surface susceptibility and hydrologic response across point to...

Distribution of rock fragments and their effects on hillslope soil erosion in purple soil, China

NASA Astrophysics Data System (ADS)

Wang, Xiaoyan

2017-04-01

Purple soil is widely distributed in Sichuan Basin and Three Gorges Reservoir Area. Purple soil region is abundant in soil fertility and hydrothermal resources, playing an important role in the agricultural development of China. Soil erosion has long been recognized as a major environmental problem in the purple soil region where the population is large and slope farming is commonly practiced, and rainstorm is numerous. The existence of rock fragments is one of the most important characteristics of purple soil. Rock fragments at the soil surface or in the soil layer affect soil erosion processes by water in various direct and indirect ways, thus the erosion processes of soil containing rock fragments have unique features. Against the severe soil degradation by erosion of purple soil slope, carrying out the research about the characteristics of purple soil containing rock fragments and understanding the influence of rock fragments on soil erosion processes have important significance, which would promote the rational utilization of purple soil slope land resources and accurate prediction of purple soil loss. Therefore, the aims of this study were to investigate the distribution of rock fragments in purple soil slope and the impact of rock fragment content on soil physical properties and soil erosion. First, field sampling methods were used to survey the spatial variability of rock fragments in soil profiles and along slope and the physical properties of soils containing rock fragments. Secondly, indoor simulated rainfall experiments were used to exam the effect of rock fragments in the soil layer on soil erosion processes and the relationships between rainfall infiltration, change of surface flow velocity, surface runoff volume and sediment on one hand, and rock fragment content (Rv, 0% 30%, which was determined according the results of field investigation for rock fragment distribution) on the other were investigated. Thirdly, systematic analysis about the influence of rock fragment cover on purple soil slope erosion process were carried on, under different conditions with two kind of rock fragment positions (resting on soil surface and embedded into top soil layer), varied rock fragment coverage (Rc, 0% 40%), two kind of soils with textural porosity or structural porosity, and three kind of rainfall intensities (I, 1 mm/min, 1.5 mm/min and 2 mm/min). Simulated rainfall experiments in situ plots in the field, combined with simulated rainfall experiments in soil pans indoor, were used. The main conclusions of this dissertation are as following: 1. The spatial distribution characteristics of rock fragments in purple soil slope and its effects on the soil physical properties were clarified basically. 2. The mechanism of influence of rock fragments within top soil layer on soil erosion processes was understood and a threshold of rock fragment content on the infiltration was figured out. 3. The relationships between surface rock fragment cover and hillslope soil erosion in purple soil under different conditions with varied rock fragment positions, soil structures and rainfall intensities were obtained and the soil and water conservation function of surface rock fragment cover on reducing soil loss was affirmed.

Natural Erosion of Sandstone as Shape Optimisation.

PubMed

Ostanin, Igor; Safonov, Alexander; Oseledets, Ivan

2017-12-11

Natural arches, pillars and other exotic sandstone formations have always been attracting attention for their unusual shapes and amazing mechanical balance that leave a strong impression of intelligent design rather than the result of a stochastic process. It has been recently demonstrated that these shapes could have been the result of the negative feedback between stress and erosion that originates in fundamental laws of friction between the rock's constituent particles. Here we present a deeper analysis of this idea and bridge it with the approaches utilized in shape and topology optimisation. It appears that the processes of natural erosion, driven by stochastic surface forces and Mohr-Coulomb law of dry friction, can be viewed within the framework of local optimisation for minimum elastic strain energy. Our hypothesis is confirmed by numerical simulations of the erosion using the topological-shape optimisation model. Our work contributes to a better understanding of stochastic erosion and feasible landscape formations that could be found on Earth and beyond.

Integrating long-offset transient electromagnetics (LOTEM) with seismics in an exploration environment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Strack, K.M.; Vozoff, K.

The applications of electromagnetics have increased in the past two decades because of an improved understanding of the methods, improves service availability, and the increased focus of exploration in the more complex reservoir characterization issues. For electromagnetic methods surface applications for hydrocarbon Exploration and Production are still a special case, while applications in borehole and airborne research and for engineering and environmental objectives are routine. In the past, electromagnetic techniques, in particular deep transient electromagnetics, made up a completely different discipline in geophysics, although many of the principles are similar to the seismic one. With an understanding of the specificmore » problems related to data processing initially and then acquisition, the inclusion of principles learned from seismics happened almost naturally. Initially, the data processing was very similar to seismic full-waveform processing. The hardware was also changed to include multichannel acquisition systems, and the field procedures became very similar to seismic surveying. As a consequence, the integration and synergism of the interpretation process is becoming almost automatic. The long-offset transient electromagnetic (LOTEM) technique will be summarized from the viewpoint of its similarity to seismics. The complete concept of the method will also be reviewed. An interpretation case history that integrates seismic and LOTEM from a hydrocarbon area in China clearly demonstrates the limitations and benefits of the method.« less

Surface modification of hydroturbine steel using friction stir processing

NASA Astrophysics Data System (ADS)

Grewal, H. S.; Arora, H. S.; Singh, H.; Agrawal, A.

2013-03-01

Friction stir processing (FSP) has proved to be a viable tool for enhancing the mechanical properties of materials, however, the major focus has been upon improving the bulk properties of light metals and their alloys. Hydroturbines are susceptible to damage owing to slurry and cavitation erosion. In this study, FSP of a commonly employed hydroturbine steel, 13Cr4Ni was undertaken. Microstructural characterization of the processed steel was conducted using optical microscopy (OM), scanning electron microscopy (SEM) equipped with energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and electron back scatter diffraction (EBSD) techniques. Mechanical characterization of the steel was undertaken in terms of microhardness and resistance to cavitation erosion (CE). FSP resulted in the refinement of the microstructure with reduction in grain size by a factor of 10. EBSD results confirmed the existence of submicron and ultrafine grained microstructure. The microhardness of the steel was found to enhance by 2.6 times after processing. The processed steel also showed 2.4 times higher resistance against cavitation erosion in comparison to unprocessed steel. The primary erosion mechanism for both the steels was identical in nature, with plastic deformation responsible for the loss of material.

Real-time holographic surveillance system

DOEpatents

Collins, H. Dale; McMakin, Douglas L.; Hall, Thomas E.; Gribble, R. Parks

1995-01-01

A holographic surveillance system including means for generating electromagnetic waves; means for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; means for receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; means for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and means for displaying the processed information to determine nature of the target. The means for processing the electrical signals includes means for converting analog signals to digital signals followed by a computer means to apply a backward wave algorithm.

Estimating rates of coastal cliff erosion in a small island using terrestrial laser scanning and RPAS-based SfM-MVS photogrammetry

NASA Astrophysics Data System (ADS)

Hayakawa, Yuichi S.; Obanawa, Hiroyuki

2017-04-01

Rapid erosion of coastal cliffs has been historically observed to be more than 1 m/y in the outer Boso Peninsula area, eastern Japan. However, due to the modern work of coastal protection, the erosion rates of the coastal cliffs have significantly decreased. This caused coastal erosion in the nearby sand beach, to which sands had been supplied from the formerly eroded rocky coast. In order to assess the relationships between erosion and protection in both rocky and sandy coasts, quantitative evaluation of erosion rates by natural processes would be necessary. The Suzume-jima Island, a small coastal island in the outer Boso Peninsula area, is an ideal site, which is located outside of the coastal protection and natural processes of erosion can still be observed. Here we carried out multiple measurements of the entire shape of the island using remotely piloted aerial system (RPAS) and structure-from-motion multi-view stereo (SfM-MVS) photogrammetry. Terrestrial laser scanning is also performed for the accuracy assessment. The high-frequency (3 times a year) and high-resolution (cm) measurements of the small island for 3 years revealed spatially variable rockfalls and wave erosion, whose volume of mass has been quantitatively revealed from the 3-D point cloud obtained. The relatively short-term measurements are also compared with the long-term 2-D topographic changes in the island by aerial photographs for 50 years.

Examination of electromagnetic powers with the example of a uc(Faraday) disc dynamo

NASA Astrophysics Data System (ADS)

Reich, Felix A.; Müller, Wolfgang H.

2018-03-01

This paper studies the mathematical form of electromagnetic powers and their influence on the balance of energy by using the example of a uc(Faraday) disc. First, two forms of energy (and balances thereof) are discussed. These employ different forms of powers, which can be distinguished w.r.t. their physical origins and their interpretations in context with the notions of supply and production. The stationary uc(Faraday) disc experiment is modeled following the description by Kovetz (Electromagnetic theory, Oxford University Press, Oxford, 2000). Concepts for formulating the electromagnetic field equations for the rotating disc are discussed, and the corresponding approximate analytical solutions are presented. Based on the obtained electromagnetic fields, the powers of the disc are analyzed for a stationary process. The conversion of mechanical power to heating and electromagnetic powering of an external resistor is explained. The paper concludes with the computation of the time evolution of the angular velocity for a magnetically induced breaking process of the disc.

Carbon redistribution by erosion processes in an intensively disturbed catchment

NASA Astrophysics Data System (ADS)

Boix-Fayos, Carolina; Martínez-Mena, María; Pérez Cutillas, Pedro; de Vente, Joris; Barberá, Gonzalo G.; Mosch, Wouter; Navarro Cano, Jose Antonio; Gaspar, Leticia; Navas, Ana

2016-04-01

Understanding how organic carbon moves with sediments along the fluvial system is crucial to close catchment scale carbon budgets. Especially challenging is the analysis of organic carbon dynamics during fluvial transport in heterogeneous, fragile and disturbed environments with ephemeral and intense hydrological pulses, typical of Mediterranean conditions. This paper explores the catchment scale organic carbon redistribution by lateral flows in extreme Mediterranean environmental conditions from a geomorphological perspective. The study area is a catchment (Cárcavo) in SE Spain with a semiarid climate, erodible lithologies, shallow soils, and highly disturbed by agricultural terraces, land levelling, reforestations and construction of check-dams. To increase understanding of erosion induced catchment scale organic carbon redistribution, we studied the subcatchments of 8 check-dams distributed along the catchment main channel in detail. We determined 137Cs, physicochemical characteristics and organic carbon pools of soils and sediments deposited behind each check-dam, performed spatial analysis of properties of the catchment and buffer areas around check-dams, and carried out geomorphological analysis of the slope-channel connections. Soils showed very low Total Organic Carbon (TOC) values oscillating between 15.2 and 4.4 g Kg-1 for forest and agricultural soils, respectively. Sediments mobilized by erosion were poor in TOC compared to the eroded (forest) soils (6.6±0.7 g Kg-1), and the redistribution of organic carbon through the catchment, especially of the Mineral Associated Organic Carbon (MAC) pool, showed the same pattern as clay particles and 137Cs. The TOC erosion rates (0.031±0.03 Mg ha-1 y-1) were comparable to others reported for subhumid Mediterranean catchments and to those modelled worldwide for pasture land. Those lateral fluxes were equivalent to 10.4 % of the TOC stock from the topsoil at the moment of the check-dam construction and reforestation works. However the organic carbon in deposited sediments comes not only from surface erosion processes, but also from deeper soil or sediment layers mobilized by concentrated erosion processes. Sediment richer in organic carbon comes from the soil surface of vegetated (reforested) areas close and well connected to the channels. Subcatchments dominated by laminar erosion processes showed two times higher TOC/total erosion ratio than subcatchments dominated by concentrated flow erosion processes. Lithology, soils and geomorphology exert a more important control on organic carbon redistribution than land use and vegetation cover in this geomorphologically very active catchment.

Extreme rates of riverbank erosion of the high bluff formed by the ice-rich syngenetic permafrost (yedoma), Itkillik River, Northern Alaska

NASA Astrophysics Data System (ADS)

Kanevskiy, M. Z.; Shur, Y.; Fortier, D.; Jorgenson, T.; Stephani, E.; Strauss, J.

2013-12-01

Riverbank erosion in areas underlain by ice-rich permafrost is strongly affected by the processes of thawing of ground ice, which include (1) thermal erosion, and (2) thermal denudation. Thermal erosion is a process of combined thermal and mechanical action of moving water, which results in simultaneous thawing of frozen soil and its removal by water. Thermal erosion can cause block collapse of eroded banks. Thermal denudation is a process of thawing of frozen soils exposed in the bluff due to solar energy and consequent removal of thawed soils by gravity. Studies of riverbank and coastal erosion revealed that the highest rates of erosion are typical of bluffs composed by yedoma (ice- and organic-rich syngenetically frozen silty deposits). Yedoma deposits can be up to 50 m thick, and they contain huge ice wedges up to 10 m wide. Since 2006, we have studied the process of riverbank erosion of the 35 m high exposure of yedoma along the Itkillik River in northern Alaska. Based on five measurements of the areas occupied by wedge ice in panoramic photographs taken in 2006, 2007, 2011, and 2012, the average wedge-ice volume makes 61% of the entire exposed bluff. The total volumetric ground ice content of the Itkillik yedoma, including wedge, segregated and pore ice, is 85%. We detect three main stages of the riverbank erosion for the study site and other similar sites in the areas of ice-rich permafrost: (1) thermal erosion combined with thermal denudation, (2) thermal denudation, and (3) slope stabilization. The first stage includes formation of thermoerosional niches; development of sub-vertical cracks and block-fall collapse of cornices; and thawing and disintegration of blocks of ground ice and frozen soil in the water. All these processes are accompanied by thermal denudation of the exposed bluff. On August 16, 2007, a big portion of the bluff fell down along the crack sub-parallel to the bluff. As a result, the vertical wall more than 65 m long entirely formed by the wedge ice was exposed. This block-fall affected the area of approximately 800 m2, and the volume of frozen soil and ice involved in the block-fall was about 15,000 m3. The riverbank retreat due to thermal erosion and/or thermal denudation, measured from August 2007 to August 2011, varied from less than 10 to almost 100 m. An estimated retreat rate average for the whole 680 m long bluff was 11.4 m/year, but for the most actively eroded central part of the bluff (150 m long) it was 20.3 m/year, ranging from 16 to 24 m/year. During these 4 years, about 650,000 m3 of ice and organic-rich frozen soil were transported to the river from the retreating bank (more than 160,000 m3/year). Analysis of aerial photographs (1948-1979) and satellite images (1974-2013) showed that the riverbank was relatively stable till July 1995, when the Itkillik River changed its course and triggered extremely active thermal erosion. The total retreat of the riverbank in 1995-2010 varied from 180 to 280 m, which means that the average retreat rate for the most actively eroded part of the riverbank reached almost 19 m/year. Such a high rate of riverbank erosion over a long time period has not been reported before for any permafrost regions of Eurasia and North America.

Hydrologic Drivers of Soil Organic Carbon Erosion and Burial: Insights from a Spatially-explicit Model of a Degraded Landscape at the Calhoun Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Dialynas, Y. G.; Bras, R. L.; Richter, D. D., Jr.

2017-12-01

Soil erosion and burial of organic material may constitute a substantial sink of atmospheric CO2. Attempts to quantify impacts of soil erosion on the soil-atmosphere C exchange are limited by difficulties in accounting for the fate of eroded soil organic carbon (SOC), a key factor in estimating of the net effect of erosion on the C cycle. Processes that transport SOC are still inadequately represented in terrestrial carbon (C) cycle models. This study investigates hydrologic controls on SOC redistribution across the landscape focusing on dynamic feedbacks between watershed hydrology, soil erosional processes, and SOC burial. We use tRIBS-ECO (Triangulated Irregular Network-based Real-time Integrated Basin Simulator-Erosion and Carbon Oxidation), a spatially-explicit model of SOC dynamics coupled with a physically-based hydro-geomorphic model. tRIBS-ECO systematically accounts for the fate of eroded SOC across the watershed: Rainsplash erosion and sheet erosion redistribute SOC from upland sites to depositional environments, altering depth-dependent soil biogeochemical properties in diverse soil profiles. Eroded organic material is transferred with sediment and can be partially oxidized upon transport, or preserved from decomposition by burial. The model was applied in the Calhoun Critical Zone Observatory (CZO), a site that is recovering from some of the most serious agricultural erosion in North America. Soil biogeochemical characteristics at multiple soil horizons were used to initialize the model and test performance. Remotely sensed soil moisture data (NASA SMAP) were used for model calibration. Results show significant rates of hydrologically-induced burial of SOC at the Calhoun CZO. We find that organic material at upland eroding soil profiles is largely mobilized by rainsplash erosion. Sheet erosion mainly drives C transport in lower elevation clayey soils. While SOC erosion and deposition rates declined with recent reforestation at the study site, the erosional potential of the degraded landscape remains significant.

Advances in wind erosion modelling in Europe

NASA Astrophysics Data System (ADS)

Borrelli, Pasquale; Lugato, Emanuele; Alewell, Christine; Montanarella, Luca; Panagos, Panos

2017-04-01

Soil erosion by wind is a serious environmental problem often resulting in severe forms of soil degradation. Wind erosion is also a phenomenon relevant for Europe, although this land degradation process has been overlooked until very recently. The state-of-the-art literature presents wind erosion as a process that locally affects the semi-arid areas of the Mediterranean region as well as the temperate climate areas of the northern European countries. Actual observations, field measurements and modelling assessments, however, are all extremely limited and highly unequally distributed across Europe. As a result, we currently lack comprehensive understanding about where and when wind erosion occurs in Europe, and the intensity of erosion that poses a threat to agricultural productivity. Today's challenge is to integrate the insights of local experiments and field-scale models into a new generation of large-scale wind erosion models. While naturally being less accurate than field-scale models, these large-scale modelling approaches still provide essential knowledge about where and when wind erosion occurs and can disclose the level of risk for agricultural productivity in specific areas. Here, we present a geographic information system (GIS) version of the RWEQ (named GIS-RWEQ) to quantitatively assess soil loss by wind over large study areas (Land Degradation & Development, DOI: 10.1002/ldr.2588). The model designed to predict the daily soil loss potential at a ca. 1 km2 spatial resolution shows high consistency with local measurements reported in literature. The average soil loss predicted by GIS-RWEQ for the European arable land totals 62 million Mg yr-1, with an average area-specific soil loss of 0.53 Mg yr-1. The JRC model RUSLE2015, for the same area estimates 295 million Mg yr-1 of soil loss due to water erosion. Notably, soil loss by wind erosion in the European arable land could be as high as 20% of water erosion, even though the areas affected are mainly concentrated in hotspots.

Diet and dental erosion in young people in south-east Brazil.

PubMed

Waterhouse, Paula J; Auad, Sheyla M; Nunn, June H; Steen, Ian N; Moynihan, Paula J

2008-09-01

The regular consumption of acidic foods and drinks may be associated with dental erosion, and soft drink consumption appears to be increasing both in developed and developing countries. Dentists are aware that an acidic diet can contribute to the development of erosion; however, there may be confusion within the profession concerning the general health message of eating five portions of fruits and vegetables each day. The aim of this study was to investigate associations between dental erosion and the consumption of acidic foods and beverages in schoolchildren in south-east Brazil. The objective was to gather information, by means of a dietary questionnaire, on frequency of intake and patterns of consumption of acidic foods and drinks in a group of schoolchildren. The hypothesis was that the experience of dental erosion among the study sample was associated with the frequency and pattern of consumption of soft drinks, fruit juices, fruits, and yogurt. A cross-sectional study was conducted in Três Corações, south-east Brazil. A sample of 458 schoolchildren, mean age 13.8 (SD 0.39) years, completed the study. Information about potential dietary risk factors for dental erosion was collected through a questionnaire survey completed by the schoolchildren. For the dental examinations, the subjects were examined for dental erosion in a school room. Associations between dental erosion and the variables under study were investigated through processes of bivariate and multivariate analyses. The statistical significance level was set at 5%. Analysis of the questionnaire surveys showed that the frequency of consumption of sugared carbonated drinks was the only variable independently associated with the erosive process, with subjects who had a daily consumption of such drinks having a greater likelihood of having erosion (P = 0.015, odds ratio 1.752, 95% confidence interval 1.116-2.750). Of all tested factors in this sample of schoolchildren the consumption of sugared carbonated drinks is most associated with dental erosion.

Vegetation-modulated landscape evolution: Effects of vegetation on landscape processes, drainage density, and topography

NASA Astrophysics Data System (ADS)

Istanbulluoglu, Erkan; Bras, Rafael L.

2005-06-01

Topography acts as a template for numerous landscape processes that include hydrologic, ecologic, and biologic phenomena. These processes not only interact with each other but also contribute to shaping the landscape as they influence geomorphic processes. We have investigated the effects of vegetation on thresholds for channel initiation and landform evolution using both analytical and numerical approaches. Vegetation is assumed to form a uniform ground cover. Runoff erosion is modeled based on a power function of excess shear stress, in which shear stress efficiency is inversely proportional to vegetation cover. This approach is validated using data. Plant effect on slope stability is represented by additional cohesion provided by plant roots. Vegetation cover is assumed to reduce sediment transport rates due to physical creep processes (rainsplash, dry ravel, and expansion and contraction of sediments) according to a negative exponential relationship. Vegetation grows as a function of both available cover and unoccupied space by plants and is killed by geomorphic disturbances (runoff erosion and landsliding) and wildfires. Analytical results suggest that in an equilibrium basin with a fixed vegetation cover, plants may cause a transition in the dominant erosion process at the channel head. A runoff erosion-dominated landscape, under none or poor vegetation cover, may become landslide dominated under a denser vegetation cover. The sign of the predicted relationship between drainage density and vegetation cover depends on the relative influence of vegetation on different erosion phenomena. With model parameter values representative of the Oregon Coast Range (OCR), numerical experiments conducted using the Channel Hillslope Integrated Landscape Development (CHILD) model confirm the findings based on the analytical theory. A highly dissected fluvial landscape emerges when surface is assumed bare. When vegetation cover is modeled, landscape relief increases, resulting in hollow erosion dominated by landsliding. Interestingly, our simulations underscore the importance of vegetation disturbances by geomorphic events and wildfires on the landscape structure. Simulated landscapes resemble real-world catchments in the OCR when such disturbances are considered.

Modeling Paragenesis: Erosion Opposite to Gravity in Cave Channels

NASA Astrophysics Data System (ADS)

Cooper, M. P.; Covington, M. D.

2017-12-01

Sediment plays an important role in bedrock channels, providing both tools and cover that influence patterns of bed erosion. It has also been shown that sediment load influences bedrock channel width, with increased sediment leading to wider channels. A variety of models have been developed to explore these effects. In caves, it is hypothesized that sediments covering the floors of fully flooded channels that are forming beneath the water table (phreatic zone) can force dissolution upwards towards the water table, leading to upward erosion balanced by gradual deposition of sediment within the channel bottom. This strange process is termed paragenesis, and while there are conceptual and experimental models of the process, no prior mathematical models of cave passage evolution has captured these effects. Consequently, there is little quantitative understanding of the processes that drive paragenesis and how they link to the morphology of the cave channels that develop. We adapt a previously developed algorithm for estimating boundary shear stress within channels with free-surface flows to enable calculation of boundary shear stress in pipe-full conditions. This model successfully duplicates scaling relationships in surface channels, and geometries of caves formed in the phreatic zone such as phreatic tubes. Once sediment flux is incorporated the model successfully duplicates the hypothesized processes of paragenetic gallery formation: the cover effect prevents dissolution in the direction of gravity; passages are enlarged upwards reducing the sediment transport capacity; sediment is deposited and the process drives a continuing feedback loop. Simulations reveal that equilibrium paragenetic channel widths scale with both sediment flux and discharge. Unlike in open channel settings, increased sediment load actually narrows paragenetic channels. The cross section evolution model also reveals that the existence of equilibrium widths in such galleries requires erosion to scale with shear stress, suggesting a role of either mechanical erosion or transport limited dissolution. These types of erosion contrast with current numerical models of speleogenesis, where chemically limited dissolution, a process independent of shear stress, is predicted to occur in most turbulent flow settings.

Large-scale assessment of soil erosion in Africa: satellites help to jointly account for dynamic rainfall and vegetation cover

NASA Astrophysics Data System (ADS)

Vrieling, Anton; Hoedjes, Joost C. B.; van der Velde, Marijn

2015-04-01

Efforts to map and monitor soil erosion need to account for the erratic nature of the soil erosion process. Soil erosion by water occurs on sloped terrain when erosive rainfall and consequent surface runoff impact soils that are not well-protected by vegetation or other soil protective measures. Both rainfall erosivity and vegetation cover are highly variable through space and time. Due to data paucity and the relative ease of spatially overlaying geographical data layers into existing models like USLE (Universal Soil Loss Equation), many studies and mapping efforts merely use average annual values for erosivity and vegetation cover as input. We first show that rainfall erosivity can be estimated from satellite precipitation data. We obtained average annual erosivity estimates from 15 yr of 3-hourly TRMM Multi-satellite Precipitation Analysis (TMPA) data (1998-2012) using intensity-erosivity relationships. Our estimates showed a positive correlation (r = 0.84) with long-term annual erosivity values of 37 stations obtained from literature. Using these TMPA erosivity retrievals, we demonstrate the large interannual variability, with maximum annual erosivity often exceeding two to three times the mean value, especially in semi-arid areas. We then calculate erosivity at a 10-daily time-step and combine this with vegetation cover development for selected locations in Africa using NDVI - normalized difference vegetation index - time series from SPOT VEGETATION. Although we do not integrate the data at this point, the joint analysis of both variables stresses the need for joint accounting for erosivity and vegetation cover for large-scale erosion assessment and monitoring.

Assessment of present day geomorphological dynamics to decipher landscape evolution around the Paleolithic sites of Melka Kunture, Ethiopia

NASA Astrophysics Data System (ADS)

Maerker, Michael; Schillaci, Calogero; Melis, Rita; Mussi, Margherita

2014-05-01

The area of Melka Kunture (central Ethiopia) is one of the most important clusters of Paleolithic sites in Eastern Africa. The archaeological record spans from c. 1.7 Ma onwards, with a number of stratified occurrences of Oldowan, Acheulean, Middle Stone Age and Late Stone Age industries, together with faunal remains and human fossils. However, the archaeological sites are endangered by flooding and soil erosion. The main excavation area lies close to the convergence of the Awash river with the Atabella river, one of the main tributaries of the upper Awash catchment. In the semi-arid Ethiopian highlands, gully networks develop especially in the vicinity of the active and inactive river meanders. Various erosion processes are linked to specific driving factors such as the rainfall regime, the land use/cover changes and vertic soils with a specific hydrological behaviour. It was documented in the field and by previous research that the origin of most of the man made erosion channels is due to animal pathways and car tracks. However, paleolandscape features increase the general erosion risk. Former wetland areas and deposition zones are particularly affected by soil erosion processes. Hence, the spatial distribution and characteristics of present day geomorphic processes also reveal information on the paleolandscape. In order to assess landscape evolution and present day geomorphologic dynamics, we mapped the geomorphology describing in detail the present-day slope processes at a 10.000 scale. We performed a detailed terrain analysis based on high resolution DEMs such as SRTM-X with 25m resolution and ALOS/PRISM with 10m resolution to characterize the main erosion processes and surface runoff dynamics. The latter ones are simulated using a Soil Conservation Service Curve Number method. Landuse was delineated for a larger area using ASTER 25m multispectral data. Finally, using calibrated topographic indices and a simple hydrological model we were able to detect and quantify the major present day soil erosion and surface runoff processes. Based on the analysis of the processes and the respective terrain features derived from the digital elevation models we also identified the major paelolandscape features. This will be the basis for assessing conservation risks related to modern land use and climate.

An empirical approach to estimate soil erosion risk in Spain.

PubMed

Martín-Fernández, Luis; Martínez-Núñez, Margarita

2011-08-01

Soil erosion is one of the most important factors in land degradation and influences desertification worldwide. In 2001, the Spanish Ministry of the Environment launched the 'National Inventory of Soil Erosion (INES) 2002-2012' to study the process of soil erosion in Spain. The aim of the current article is to assess the usefulness of this National Inventory as an instrument of control, measurement and monitoring of soil erosion in Spain. The methodology and main features of this National Inventory are described in detail. The results achieved as of the end of May 2010 are presented, together with an explanation of the utility of the Inventory as a tool for planning forest hydrologic restoration, soil protection, erosion control, and protection against desertification. Finally, the authors make a comparative analysis of similar initiatives for assessing soil erosion in other countries at the national and European levels. Copyright © 2011 Elsevier B.V. All rights reserved.

Assessment and management of dental erosion.

PubMed

Wang, Xiaojie; Lussi, Adrian

2010-07-01

Studies have shown a growing trend toward increasing prevalence of dental erosion, associated with the declining prevalence of caries disease in industrialized countries. Erosion is an irreversible chemical process that results in tooth substance loss and leaves teeth susceptible to damage as a result of wear over the course of an individual's lifetime. Therefore, early diagnosis and adequate prevention are essential to minimize the risk of tooth erosion. Clinical appearance is the most important sign to be used to diagnose erosion. The Basic Erosive Wear Examination (BEWE) is a simple method to fulfill this task. The determination of a variety of risk and protective factors (patient-dependent and nutrition-dependent factors) as well as their interplay are necessary to initiate preventive measures tailored to the individual. When tooth loss caused by erosive wear reaches a certain level, oral rehabilitation becomes necessary. Copyright 2010 Elsevier Inc. All rights reserved.

Combined slurry and cavitation erosion resistance of surface modified SS410 stainless steel

NASA Astrophysics Data System (ADS)

Amarendra, H. J.; Pratap, M. S.; Karthik, S.; Punitha Kumara, M. S.; Rajath, H. C.; Ranjith, H.; Shubhatunga, S. V.

2018-03-01

Slurry erosion and combined slurry and cavitation erosion resistance of thermal spray coatings are studied and compared with the as-received martensitic stainless steel material. 70Ni-Cr coatings are deposited on SS 410 material through plasma thermal spray process. The synergy effect of the combined slurry and cavitation erosion resistance of plasma thermal spray coatings were investigated in a slurry pot tester in the presence of bluff bodies known as Cavitation Inducers. Results showed the combined slurry and cavitation erosion resistance of martensitic stainless steel - 410 can be improved by plasma thermal spray coating. It is observed that the plasma spray coated specimens are better erosion resistant than the as- received material, subjected to erosion test under similar conditions. As-received and the surface modified steels are mechanically characterized for its hardness, bending. Morphological studies are conducted through scanning electron microscope.

Land use and climate change impacts on runoff and soil erosion at the hillslope scale in the Brazilian Cerrad

USDA-ARS?s Scientific Manuscript database

Changes in land use and climate can influence runoff and soil erosion, threatening soil and water conservation in the Cerrado biome in Brazil. The adoption of a process-based model was necessary due to the lack of long-term observed data. Our goals were to calibrate the WEPP (Water Erosion Predictio...

The Impact of Hydrodynamics in Erosion - Deposition Process in Can Gio Mangrove Biosphere Reserve, South Viet Nam

NASA Astrophysics Data System (ADS)

Vo-Luong, H. P.

2014-12-01

Can Gio Mangrove Biosphere Reserve is always considered as a friendly green belt to protect and bring up the habitants. However, recently some mangrove areas in the Dong Tranh estuary are being eroded seriously. Based on the field measurements in SW and NE monsoons as well as data of topography changes in 10 years, it is proved that hydrodynamics of waves, tidal currents and riverine currents are the main reasons for erosion-deposition processes at the studied site. The erosion-deposition process changes due to monsoon. The analysed results show that high waves and tidal oscillation cause the increase of the erosion rate in NE monsoon. However, high sediment deposition occurs in SW monsoon due to weak waves and more alluvium from upstream. Many young mangrove trees grow up and develop in the SW monsoon. From the research, it is strongly emphasized the role of mangrove forests in soil retention and energy dissipation.

Assessment of Cavitation-Erosion Resistance of 316LN Stainless Steel Following a Nitro-Carburizing Surface Treatment

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pawel, Steven J

2009-11-01

A nitro-carburizing surface treatment known domestically as the Melonite process was applied to type 316LN stainless steel test pieces and exposed to sonication conditions in mercury using a vibratory horn technique. Cavitation-erosion damage was evaluated for extended exposures and compared to other surface treatments on the same substrate alloy. The results indicate that the Melonite process substantially retards weight loss and crater development for extended periods, but gradually is eroded/destroyed leading to exposure of the substrate and cavitation-erosion behavior similar to untreated specimens. Compared with other surface treatments, cavitation-erosion results indicate that specimens treated with Melonite perform similarly to specimensmore » treated with a simple nitriding process. Neither the simple nitriding nor the Melonite treatment is quite as effective as a previously evaluated low temperature carburizing treatment, the latter being about a factor of three better than Melonite in terms of weight loss during sonication in mercury.« less

High-Temperature Erosive Behavior of Plasma Sprayed Cr3C2-NiCr/Cenosphere Coating

NASA Astrophysics Data System (ADS)

Mathapati, Mahantayya; Doddamani, Mrityunjay; Ramesh, M. R.

2018-02-01

This research examines the deposition of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings on MDN 321 steel through the process of plasma spray. In this process, the solid particle erosion test is established at 200, 400, 600 °C with 30° and 90° impact angles. Alumina erodent is adopted to investigate the erosive behavior of the coating at higher temperatures. The properties of the Cr3C2-NiCr/cenosphere coating are established based on the microhardness, the adhesive strength, the fracture toughness, and the ductility. To quantify volume loss as a result of erosion, an optical profilometer is used. At higher temperature, decrease in the erosion volume loss of Cr3C2-NiCr/cenosphere and Cr3C2-NiCr coatings is observed. The erosion-resistive property of Cr3C2-NiCr/cenosphere coating is higher than that of MDN 321 steel by 76%. This property is influenced by high-temperature stability of mullite, alumina, and protective oxide layer that is formed at elevated temperatures. The morphology of eroded coating discloses a brittle mode of material removal.

The role of erosion, abrasion and attrition in tooth wear.

PubMed

Barbour, Michele E; Rees, Gareth D

2006-01-01

There is increasing clinical awareness of erosion of enamel and dentine by dietary acids and the consequent increased susceptibility to physical wear. Enamel erosion is characterized by acid-mediated surface softening that, if unchecked, will progress to irreversible loss of surface tissue, potentially exposing the underlying dentine. In comparison, dentine erosion is less well understood as the composition and microstructure are more heterogeneous. Factors which affect the erosive potential of a solution include pH, titratable acidity, common ion concentrations, and frequency and method of exposure. Abrasion and attrition are sources of physical wear and are commonly associated with tooth brushing and tooth-to-tooth contact, respectively. A combination of erosion and abrasion or attrition exacerbates wear; however, further research is required to understand the role of fluoride in protecting mineralized tissues from such processes. Abrasive wear may be seen in a wide range of patients, whereas attritive loss is usually seen in individuals with bruxism. Wear processes are implicated in the development of dentine hypersensitivity. Saliva confers the major protective function against wear due to its role in pellicle formation, buffering, acid clearance, and hard tissue remineralization. This review focuses on the physiochemical factors impacting tooth wear.

Intensification of citrus production and soil loss in Eastern Spain

NASA Astrophysics Data System (ADS)

Cerdà, A.; González Peñaloza, F. A.; Burguet, M.; Giménez Morera, A.

2012-04-01

After land abandonment for five decades (Arnáez et al., 2010; Belmonte Serrato et al., 1999) as a widespread process in Spain, agriculture intensification is taken place. This is changing the nature of the soil erosion processes as they were known (Cerdà, 1997; Cammeraat and Imeson, 1999; Ruiz Sinoga et al., 2010; Zavala et al., 2010). Citrus production are being reallocated on slopes due to the new irrigation systems (drip-irrigation), the thermic inversion on the bottom of the valley and then the frost affecting the plantations, the high prices of the bottom valley lands and the investment in agriculture from other economic sectors such as tourism and industry. Those new plantations are based on intense pesticides and herbicides use, and erosion processes are triggered due to the sloping surface developed (Cerdà et al., 2010). Five study sites were selected in the Montesa Municipality research zone, where an increase in the orange and clementines plantations were found during the last 20 years. Measurements were perfomed by a simple method, which consist in measuring the surface characteristics: stoniness, crust, herbs, bare soil, sheet flow, rills and gullies. One thousand meters were monitored at each of the study sites and measurements were done in January and August with a precision of 1 cm. The results show that the erosion rates are controlled by the sheet erosion (78,4 %), although rill and gullies exist (< 1 %) and they are active and contribute to high erosion rates. Stones and vegetation cover was found to by low. The infiltration rates of the soils were measured by means of rainfall simulation experiments and cylinder infiltrometer. The results show that the new citrus plantations results in low infiltration rates, and high erosion rates. This is contributing to a non-sustainable agriculture production due to the high erosion rates. And also a lack in soil services as the surface runoff and then the soil erosion is enhanced; and soil infiltration reduce. The economical value of the land and water lost is making this new intense chemically managed new citrus plantation non sustainable. The intensification of agriculture is triggering new soil erosion processes to be added to the traditional ones (García Ruiz and López Bermúdez, 2009). This research study is being supported by the the research project CGL2008-02879/BTE

Water and processes of degradation in the Martian landscape

NASA Technical Reports Server (NTRS)

Milton, D. J.

1973-01-01

It is shown that erosion has been active on Mars so that many of the surface landforms are products of degradation. Unlike earth, erosion has not been a universal process, but one areally restricted and intermittently active so that a landscape is the product of one or two cycles of erosion and large areas of essentially undisturbed primitive terrain; running water has been the principal agent of degradation. Many features on Mars are most easily explained by assuming running surface water at some time in the past; for a few features, running water is the only possible explanation.

Soil Erosion as a stochastic process

NASA Astrophysics Data System (ADS)

Casper, Markus C.

2015-04-01

The main tools to provide estimations concerning risk and amount of erosion are different types of soil erosion models: on the one hand, there are empirically based model concepts on the other hand there are more physically based or process based models. However, both types of models have substantial weak points. All empirical model concepts are only capable of providing rough estimates over larger temporal and spatial scales, they do not account for many driving factors that are in the scope of scenario related analysis. In addition, the physically based models contain important empirical parts and hence, the demand for universality and transferability is not given. As a common feature, we find, that all models rely on parameters and input variables, which are to certain, extend spatially and temporally averaged. A central question is whether the apparent heterogeneity of soil properties or the random nature of driving forces needs to be better considered in our modelling concepts. Traditionally, researchers have attempted to remove spatial and temporal variability through homogenization. However, homogenization has been achieved through physical manipulation of the system, or by statistical averaging procedures. The price for obtaining this homogenized (average) model concepts of soils and soil related processes has often been a failure to recognize the profound importance of heterogeneity in many of the properties and processes that we study. Especially soil infiltrability and the resistance (also called "critical shear stress" or "critical stream power") are the most important empirical factors of physically based erosion models. The erosion resistance is theoretically a substrate specific parameter, but in reality, the threshold where soil erosion begins is determined experimentally. The soil infiltrability is often calculated with empirical relationships (e.g. based on grain size distribution). Consequently, to better fit reality, this value needs to be corrected experimentally. To overcome this disadvantage of our actual models, soil erosion models are needed that are able to use stochastic directly variables and parameter distributions. There are only some minor approaches in this direction. The most advanced is the model "STOSEM" proposed by Sidorchuk in 2005. In this model, only a small part of the soil erosion processes is described, the aggregate detachment and the aggregate transport by flowing water. The concept is highly simplified, for example, many parameters are temporally invariant. Nevertheless, the main problem is that our existing measurements and experiments are not geared to provide stochastic parameters (e.g. as probability density functions); in the best case they deliver a statistical validation of the mean values. Again, we get effective parameters, spatially and temporally averaged. There is an urgent need for laboratory and field experiments on overland flow structure, raindrop effects and erosion rate, which deliver information on spatial and temporal structure of soil and surface properties and processes.

Evolving Landscapes: the Effect of Genetic Variation on Salt Marsh Erosion

NASA Astrophysics Data System (ADS)

Bernik, B. M.; Blum, M. J.

2014-12-01

Ecogeomorphic studies have demonstrated that biota can exert influence over geomorphic processes, such as sediment transport, which in turn have biotic consequences and generate complex feedbacks. However, little attention has been paid to the potential for feedback to arise from evolutionary processes as population genetic composition changes in response to changing physical landscapes. In coastal ecosystems experiencing land loss, for example, shoreline erosion entails reduced plant survival and reproduction, and thereby represents a geomorphic response with inherent consequences for evolutionary fitness. To get at this topic, we examined the effect of genetic variation in the saltmarsh grass Spartina alterniflora, a renowned ecosystem engineer, on rates of shoreline erosion. Field transplantation studies and controlled greenhouse experiments were conducted to compare different genotypes from both wild and cultivated populations. Plant traits, soil properties, accretion/subsidence, and rates of land loss were measured. We found significant differences in rates of erosion between field plots occupied by different genotypes. Differences in erosion corresponded to variation in soil properties including critical shear stress and subsidence. Plant traits that differed across genotypes included belowground biomass, root tensile strength, and C:N ratios. Our results demonstrate the importance of genetic variation to salt marsh functioning, elucidating the relationship between evolutionary processes and ecogeomorphic dynamics in these systems. Because evolutionary processes can occur on ecological timescales, the direction and strength of ecogeomorphic feedbacks may be more dynamic than previously accounted for.

Short-term Morphodynamics of an Eroding Salt Marsh Shoreline in the Delaware Estuary, USA

NASA Astrophysics Data System (ADS)

Fanta, D.; Quirk, T. E.

2017-12-01

Marsh edge morphology can change rapidly through erosional and depositional processes. Along seemingly similar stretches of marsh shoreline, erosion processes and rates can vary dramatically. In the Delaware Estuary, annual rates of edge erosion vary from a few centimeters to several meters across relatively short stretches of shoreline. Differences in erosion processes observed here include areas with and without vegetation growth seaward of the eroding marsh scarp. To better understand the factors that influence changes in marsh edge morphology, we examined wave energy, marsh scarp profile, and vegetation structure in relation to lateral erosion and accretion along two stretches of the Delaware Estuary for two years. Rates of erosion ranged from 0.01 to over 7 m/yr depending on shoreline exposure to waves and location on marsh scarp depth profile. Sediment deposition and accretion were up to an order of magnitude higher 15 cm from the marsh edge than 5 cm from the marsh edge, and were driven by storm events. In some areas, vegetation persisted seaward of eroding marshes where wave activity was dampened by a shallower bathymetric profile. Wave energy, distance from the edge and marsh elevation all contributed to vegetation structure, and therefore sedimentation and accretion dynamics. These results highlight the interactive nature of biophysical processes leading to lateral retreat or potential resilience of marsh edges.

Erosion of Northern Hemisphere blanket peatlands under 21st-century climate change

NASA Astrophysics Data System (ADS)

Li, Pengfei; Holden, Joseph; Irvine, Brian; Mu, Xingmin

2017-04-01

Peatlands are important terrestrial carbon stores particularly in the Northern Hemisphere. Many peatlands, such as those in the British Isles, Sweden, and Canada, have undergone increased erosion, resulting in degraded water quality and depleted soil carbon stocks. It is unclear how climate change may impact future peat erosion. Here we use a physically based erosion model (Pan-European Soil Erosion Risk Assessment-PEAT), driven by seven different global climate models (GCMs), to predict fluvial blanket peat erosion in the Northern Hemisphere under 21st-century climate change. After an initial decline, total hemispheric blanket peat erosion rates are found to increase during 2070-2099 (2080s) compared with the baseline period (1961-1990) for most of the GCMs. Regional erosion variability is high with changes to baseline ranging between -1.27 and +21.63 t ha-1 yr-1 in the 2080s. These responses are driven by effects of temperature (generally more dominant) and precipitation change on weathering processes. Low-latitude and warm blanket peatlands are at most risk to fluvial erosion under 21st-century climate change.

Slurry Erosive Wear Evaluation of HVOF-Spray Cr2O3 Coating on Some Turbine Steels

NASA Astrophysics Data System (ADS)

Goyal, Deepak Kumar; Singh, Harpreet; Kumar, Harmesh; Sahni, Varinder

2012-09-01

In this study, Cr2O3 coatings were deposited on CF8M and CA6NM turbine steels by high-velocity oxy-fuel (HVOF)-spray process and analyzed with regard to their performance under slurry erosion conditions. High Speed Erosion Test Rig was used for slurry erosion tests, and the effects of three parameters, namely, average particle size, speed (rpm), and slurry concentration on slurry erosion of these materials were investigated. SEM micrographs on the surface of samples, before and after slurry erosion tests, were taken to study the erosion mechanism. For the uncoated steels, CA6NM steel showed better erosion resistance in comparison with CF8M steel. The HVOF-sprayed Cr2O3-coated CF8M and CA6NM steels showed better slurry erosion resistance in comparison with their uncoated counterparts. It may be due to the higher hardness as a result of HVOF-sprayed Cr2O3 coating in comparison with the uncoated CF8M and CA6NM steels.

Zonal characterization of hillslope erosion processes in a semi-arid high mountain catchment

NASA Astrophysics Data System (ADS)

Torres, Raquel; Millares, Agustín; Aguilar, Cristina; Moñino, Antonio; Ángel Losada, Miguel; José Polo, María

2013-04-01

Mediterranean and semi-arid catchments, generally suffer heterogeneous erosive processes at different spatio-temporal scales which produce, in a synergistic manner, a large amount of sediment supply. In mountainous catchments, the influence of pluvio-nival hydrological regime leads to a clear subdivision into homogeneous zones regarding the nature of hillslope processes. Here, a distinction could be addressed with 1) subsurface erosion due to saturated soil by intense snowmelt pulses and 2) steepest mid-mountain soil loss with rill/interrill, small-scale landslides and ephemeral or permanent gullying. Furthermore, the associated channels in these areas are formed by wide alluvial floodplains with important bedload contributions. This complexity conditions the evaluation of erosion and monitoring at catchment scale with elevated costs in time, devices and staff. The catchment of the Guadalfeo river encloses 1200 km², with important presence of snow in the summits height on its right margin, and semiarid low range hills with very erodible soils on its left margin. Gully erosion, landslides and stream bed-load processes, extremely actives in this area, are responsible of a real problem of soil loss and desertification with a high associated cost. This work suggests a methodology for the zonal assessment of different erosive processes taking into account the described heterogeneity and the reduction of research costs. To do this, high resolution bathymetric and topographic surveys supported in a reservoir (110 hm3) allowed the differentiation of bedload and suspended sediments as both are deposited in different locations and hence the validation of the hillslope sediment yield. In parallel, measurements in homogeneous areas were selected in order to obtain zonal results to achieve the representative processes involved. The use of portable samplers allows the remote changing of sampling routines, and thus to capture the temporal scale of the processes and the associated forcing agents. The obtained results validate the proposed methodology with adjustments/fitting between measured suspended sediment regarding the increase of volume registered at the dam. Furthermore, the measures obtained reveal a clear zonal differentiation in sediment yield which represents the heterogeneous dynamic of the processes involved.

Determining Consistency of Tillage Direction with Soil Erosion Protection Requirements as The Element of Decision-Making Process in Planning and Applying Land Consolidation

NASA Astrophysics Data System (ADS)

Bozek, Piotr; Janus, Jaroslaw; Taszakowski, Jaroslaw; Glowacka, Agnieszka

2016-10-01

Water erosion is one of the factors which have negative effect on soil productivity. It often leads to irreversible soil degradation, making soil worthless for agricultural activities. One way of preventing water erosion is making the direction of cultivation perpendicular to the direction of rainwater run-off. Matching the direction with the shape of parcels boundaries in small and extended ones is often possible only through changes in the configuration of property boundaries, which is possible only in the process of land consolidation. The article presents methodology of qualifying the areas for changes in boundaries configuration and cultivation direction in view of existing erosion risk. A computation process was suggested that uses, among others, LIDAR data to model the terrain shape precisely as well as cadastral data that defines the geometry of parcels and, resulting from it, the direction of cultivation and form of use. The suggested process includes also the information on the texture of soil upper horizons from soil agricultural maps. The RUSLE erosion model was applied and the computation process took place in ArcGIS environment with the use of dedicated algorithms suggested and implemented to solve the formulated problem. Computations were conducted for test area of several hundred hectares which was characterized by vast diversity of soil types and landforms. The results prove the usefulness of the suggested method as an element of systems that support decision-making processes used in the stage of determining objects chosen for the realization of consolidating processes (including local consolidation, which covers only chosen fragment of a village). They can also be used in the stage of completing detailed plans of parcels distribution in land consolidation process. The importance of the method is particularly seen in the analysis of areas where land fragmentation indices are unfavourable. Especially in these cases, without the reorganization of boundaries, it is impossible to adapt the direction of cultivation to the requirements of protection against erosion.

Two millennia of soil dynamics derived from ancient desert terraces using high resolution 3-D data

NASA Astrophysics Data System (ADS)

Filin, Sagi; Arav, Reuma; Avni, Yoav

2017-04-01

Large areas in the arid southern Levant are dotted with ancient terrace-based agriculture systems which were irrigated by runoff harvesting techniques. They were constructed and maintained between the 3rd - 9th centuries AD and abandoned in the 10th century AD. During their 600 years of cultivation, these terraces documented the gradual aggradation of alluvial soils, erosion processes within the drainage basins, as well as flashflood damage. From their abandonment and onwards, they documented 1000 years and more of land degradation and soil erosion processes. Examination of these installations presents an opportunity to study natural and anthropogenic induced changes over almost two millennia. On a global scale, such an analysis is unique as it is rare to find intact manifestations of anthropogenic influences over such time-scales because of landscape dynamics. It is also rare to find a near millennia documentation of soil erosion processes. We study in this paper the aggradation processes within intact agriculture plots in the region surrounding the world heritage Roman-Byzantine ancient city of Avdat, Negev Highlands. We follow the complete cycle of the historical desert agriculture, from the configuration pre-dating the first anthropogenic intervention, through the centuries of cultivation, and up to the present erosion phase, which spans over more than a millennium. We use high resolution 3-D laser scans to document the erosion and the environmental dynamics during these two millennia. The high-resolution data is then utilized to compute siltation rates as well as erosion rates. The long-term measures of soil erosion and land degradation we present here significantly improve our understanding of the mechanism of long-term environmental change acting in arid environments. For sustainable desert inhabitation, the study offers insights into better planning of modern agriculture in similar zones as well as insights on strategies needed to protect such historical installations.

B Removal by Zr Addition in Electromagnetic Solidification Refinement of Si with Si-Al Melt

NASA Astrophysics Data System (ADS)

Lei, Yun; Ma, Wenhui; Sun, Luen; Dai, Yongnian; Morita, Kazuki

2016-02-01

This study investigated a new process of enhancing B removal by adding small amounts of Zr in the electromagnetic solidification refinement of Si with Si-Al melt. B in Si was removed by as much as 97.2 pct by adding less than 1057 ppma Zr, and the added Zr was removed by as much as 99.7 pct. In addition, Zr is more effective in enhancing B removal than Ti in the same electromagnetic solidification refining process.

Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

NASA Astrophysics Data System (ADS)

Cadena, M. S. Reyes; Chapul, L. Sánchez; Pérez, Javiér; García, M. N. Jiménez; López, M. A. Jiménez; Espíndola, M. E. Sánchez; Perez, R. Paniagua; Hernández, N. A.; Paniagua, G.; Uribe, F.; Nava, J. J. Godina; Segura, M. A. Rodríguez

2008-08-01

We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-β) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animals subjected to ELF together with the transfer factor.

The Middle Sacramento River: Human Impacts on Physical and Ecological Processes Along a Meandering River

Treesearch

Koll Buer; Dave Forwalter; Mike Kissel; Bill Stohlert

1989-01-01

Native plant and wildlife communities along Northern California's middle Sacramento River (Red Bluff to Colusa) originally adapted to a changing pattern of erosion and deposition across a broad meander belt. The erosion-deposition process was in balance, with the river alternately building and eroding terraces. Human-induced changes to the Sacramento River,...

Geologic controls of erosion and sedimentation on Mars

NASA Technical Reports Server (NTRS)

Tanaka, K. L.; Dohm, J. M.; Carr, M. H.

1993-01-01

Because Mars has had a history of diverse erosional and depositional styles, a variety of erosional landforms and sedimentary deposits can be seen on Viking orbiter images. Here we review how geologic processes involving rock, water, and structure have controlled erosion and sedimentation on Mars. Additionally, we review how further studies will help refine our understanding of these processes.

Arbuscule mycorrhizae: A linkage between erosion and plant processes in a southwest grassland

Treesearch

Mary O' Dea; D. Phillip Guertin; C. P. P. Reid

2000-01-01

Plant and soil processes within a natural ecosystem interact with surface hydrology through their influence on surface roughness, soil structure, and evaporation, and through their relation with soil biota. In the Southwest, decreases in perennial grass cover and erosion on uplands and stream channels can initiate a decline in watershed condition. Agronomic literature...

Geomorphology and the Law of Unintended Consequences (Locke, 1691): Lessons from coastal weathering and erosion at Prawle (UK) and Kaikoura (NZ)

NASA Astrophysics Data System (ADS)

Mottershead, Derek N.; Stephenson, Wayne J.; Hemmingsen, Maree A.

2016-07-01

The sites of two field experiments based on micro-erosion metering, one in UK the other in New Zealand, were independently revisited respectively 33 and 17 years after installation. At both sites natural weathering and erosion processes had been inadvertently interrupted by the experimental works, leading to the development of new microscale landforms. These are interpreted in the context of modifications of the controls on weathering processes, leading to enhanced understanding of the processes themselves. This has lessons for the geomorphologist in maintaining a long-term watching brief over former experimental sites, lest some unintended and potentially beneficial outcome has ensued. This theme is embraced by the Law of Unintended Consequences.

Tracking spatial variation in river load from Andean highlands to inter-Andean valleys

NASA Astrophysics Data System (ADS)

Tenorio, Gustavo E.; Vanacker, Veerle; Campforts, Benjamin; Álvarez, Lenín; Zhiminaicela, Santiago; Vercruysse, Kim; Molina, Armando; Govers, Gerard

2018-05-01

Mountains play an important role in the denudation of continents and transfer erosion and weathering products to lowlands and oceans. The rates at which erosion and weathering processes take place in mountain regions have a substantial impact on the morphology and biogeochemistry of downstream reaches and lowlands. The controlling factors of physical erosion and chemical weathering and the coupling between the two processes are not yet fully understood. In this study, we report physical erosion and chemical weathering rates for five Andean catchments located in the southern Ecuadorian Andes and investigate their mutual interaction. During a 4-year monitoring period, we sampled river water at biweekly intervals, and we analyzed water samples for major ions and suspended solids. We derived the total annual dissolved, suspended sediment, and ionic loads from the flow frequency curves and adjusted rating curves and used the dissolved and suspended sediment yields as proxies for chemical weathering and erosion rates. In the 4-year period of monitoring, chemical weathering exceeds physical erosion in the high Andean catchments. Whereas physical erosion rates do not exceed 30 t km-2 y-1 in the relict glaciated morphology, chemical weathering rates range between 22 and 59 t km-2 y-1. The variation in chemical weathering is primarily controlled by intrinsic differences in bedrock lithology. Land use has no discernible impact on the weathering rate but leads to a small increase in base cation concentrations because of fertilizer leaching in surface water. When extending our analysis with published data on dissolved and suspended sediment yields from the northern and central Andes, we observe that the river load composition strongly changes in the downstream direction, indicating large heterogeneity of weathering processes and rates within large Andean basins.

An Experimental Study on Slurry Erosion Resistance of Single and Multilayered Deposits of Ni-WC Produced by Laser-Based Powder Deposition Process

NASA Astrophysics Data System (ADS)

Balu, Prabu; Hamid, Syed; Kovacevic, Radovan

2013-11-01

Single and multilayered deposits containing different mass fractions of tungsten carbide (WC) in nickel (Ni)-matrix (NT-20, NT-60, NT-80) are deposited on a AISI 4140 steel substrate using a laser-based powder deposition process. The transverse cross section of the coupons reveals that the higher the mass fraction of WC in Ni-matrix leads to a more uniform distribution through Ni-matrix. The slurry erosion resistance of the fabricated coupons is tested at three different impingement angles using an abrasive water jet cutting machine, which is quantified based on the erosion rate. The top layer of a multilayered deposit (i.e., NT-60 in a two-layer NT-60 over NT-20 deposit) exhibits better erosion resistance at all three tested impingement angles when compared to a single-layer (NT-60) deposit. A definite increase in the erosion resistance is noted with an addition of nano-size WC particles. The relationship between the different mass fractions of reinforcement (WC) in the deposited composite material (Ni-WC) and their corresponding matrix (Ni) hardness on the erosion rate is studied. The eroded surface is analyzed in the light of a three-dimensional (3-D) profilometer and a scanning electron microscope (SEM). The results show that a volume fraction of approximately 62% of WC with a Ni-matrix hardness of 540 HV resulting in the gouging out of WC from the Ni-matrix by the action of slurry. It is concluded that the slurry erosion resistance of the AISI 4140 steel can be significantly enhanced by introducing single and multilayered deposits of Ni-WC composite material fabricated by the laser-based powder deposition process.

Comparison of SWAT and GeoWEPP model in predicting the impact of stone bunds on runoff and erosion processes in the Northern Ethiopian Highlands

NASA Astrophysics Data System (ADS)

Demelash, Nigus; Flagler, Jared; Renschler, Chris; Strohmeier, Stefan; Holzmann, Hubert; Feras, Ziadat; Addis, Hailu; Zucca, Claudio; Bayu, Wondimu; Klik, Andreas

2017-04-01

Soil degradation is a major issue in the Ethiopian highlands which are most suitable for agriculture and, therefore, support a major part of human population and livestock. Heavy rainstorms during the rainy season in summer create soil erosion and runoff processes which affect soil fertility and food security. In the last years programs for soil conservation and afforestation were initiated by the Ethiopian government to reduce erosion risk, retain water in the landscape and improve crop yields. The study was done in two adjacent watersheds in the Northwestern highlands of Ethiopia. One of the watersheds is developed by soil and water conservation structures (stone bunds) in 2011 and the other one is without soil and water conservation structures. Spatial distribution of soil textures and other soil properties were determined in the field and in the laboratory and a soil map was derived. A land use map was evaluated based on satellite images and ground truth data. A Digital Elevation Model of the watershed was developed based on conventional terrestrial surveying using a total station. At the outlet of the watersheds weirs with cameras were installed to measure surface runoff. During each event runoff samples were collected and sediment concentration was analyzed. The objective of this study is 1) to assess the impact of stone bunds on runoff and erosion processes by using simulation models, and 2) to compare the performance of two soil erosion models in predicting the measurements. The selected erosion models were the Soil and Water Assessment Tool (SWAT) and the Geospatial Interface to the Water Erosion Prediction Project (GeoWEPP). The simulation models were calibrated/verified for the 2011-2013 periods and validated with 2014-2015 data. Results of this comparison will be presented.

Process-based coastal erosion modeling for Drew Point (North Slope, Alaska)

USGS Publications Warehouse

Ravens, Thomas M.; Jones, Benjamin M.; Zhang, Jinlin; Arp, Christopher D.; Schmutz, Joel A.

2012-01-01

A predictive, coastal erosion/shoreline change model has been developed for a small coastal segment near Drew Point, Beaufort Sea, Alaska. This coastal setting has experienced a dramatic increase in erosion since the early 2000’s. The bluffs at this site are 3-4 m tall and consist of ice-wedge bounded blocks of fine-grained sediments cemented by ice-rich permafrost and capped with a thin organic layer. The bluffs are typically fronted by a narrow (∼ 5  m wide) beach or none at all. During a storm surge, the sea contacts the base of the bluff and a niche is formed through thermal and mechanical erosion. The niche grows both vertically and laterally and eventually undermines the bluff, leading to block failure or collapse. The fallen block is then eroded both thermally and mechanically by waves and currents, which must occur before a new niche forming episode may begin. The erosion model explicitly accounts for and integrates a number of these processes including: (1) storm surge generation resulting from wind and atmospheric forcing, (2) erosional niche growth resulting from wave-induced turbulent heat transfer and sediment transport (using the Kobayashi niche erosion model), and (3) thermal and mechanical erosion of the fallen block. The model was calibrated with historic shoreline change data for one time period (1979-2002), and validated with a later time period (2002-2007).

Rainfall and sheet power model for interrill erosion in steep slope

NASA Astrophysics Data System (ADS)

Shin, Seung Sook; Deog Park, Sand; Nam, Myeong Jun

2015-04-01

The two-phase process of interrill erosion consist of the splash and detachment of individual particles from soil mass by impact of raindrops and the transport by erosive running water. Most experimental results showed that the effect of interaction between rainfall impact and surface runoff increases soil erosion in low or gentle slope. Especially, the combination of rain splash and sheet flow is the dominant runoff and erosion mechanism occurring on most steep hillslopes. In this study, a rainfall simulation was conducted to evaluate interrill erosion in steep slope with cover or non-cover. The kinetic energy of raindrops of rainfall simulator was measured by disdrometer used to measure the drop size distribution and velocity of falling raindrops and showed about 0.563 rate of that calculated from empirical equation between rainfall kinetic energy and rainfall intensity. Surface and subsurface runoff and sediment yield depended on rainfall intensity, gradient of slope, and existence of cover. Sediment from steep plots under rainfall simulator is greatly reduced by existence of the strip cover that the kinetic energy of raindrop approximates to zero. Soil erosion in steep slope with non-cover was nearly 4.93 times of that measured in plots with strip cover although runoff was only 1.82 times. The equation of a rainfall and sheet power was used to evaluate sediment yields in steep slope with cover or non-cover. The power model successfully explained physical processes for interrill erosion that combination of raindrop impact and sheet flow increases greatly soil erosion in steep slope. This research was supported by Basic Science Research Program through the National Research Foundation of Korea(NRF) funded by the Ministry of Education, Science and Technology(No. 2013R1A1A3011962).

Modeling of soil erosion and sediment transport in the East River Basin in southern China.

PubMed

Wu, Yiping; Chen, Ji

2012-12-15

Soil erosion is a major global environmental problem that has caused many issues involving land degradation, sedimentation of waterways, ecological degradation, and nonpoint source pollution. Therefore, it is significant to understand the processes of soil erosion and sediment transport along rivers, and this can help identify the erosion prone areas and find potential measures to alleviate the environmental effects. In this study, we investigated soil erosion and identified the most seriously eroded areas in the East River Basin in southern China using a physically-based model, Soil and Water Assessment Tool (SWAT). We also introduced a classical sediment transport method (Zhang) into SWAT and compared it with the built-in Bagnold method in simulating sediment transport process along the river. The derived spatial soil erosion map and land use based erosion levels can explicitly illustrate the identification and prioritization of the critical soil erosion areas in this basin. Our results also indicate that erosion is quite sensitive to soil properties and slope. Comparison of Bagnold and Zhang methods shows that the latter can give an overall better performance especially in tracking the peak and low sediment concentrations along the river. We also found that the East River is mainly characterized by sediment deposition in most of the segments and at most times of a year. Overall, the results presented in this paper can provide decision support for watershed managers about where the best management practices (conservation measures) can be implemented effectively and at low cost. The methods we used in this study can also be of interest in sediment modeling for other basins worldwide. Published by Elsevier B.V.

Modeling winter hydrological processes under differing climatic conditions: Modifying WEPP

NASA Astrophysics Data System (ADS)

Dun, Shuhui

Water erosion is a serious and continuous environmental problem worldwide. In cold regions, soil freeze and thaw has great impacts on infiltration and erosion. Rain or snowmelt on a thawing soil can cause severe water erosion. Of equal importance is snow accumulation and snowmelt, which can be the predominant hydrological process in areas of mid- to high latitudes and forested watersheds. Modelers must properly simulate winter processes to adequately represent the overall hydrological outcome and sediment and chemical transport in these areas. Modeling winter hydrology is presently lacking in water erosion models. Most of these models are based on the functional Universal Soil Loss Equation (USLE) or its revised forms, e.g., Revised USLE (RUSLE). In RUSLE a seasonally variable soil erodibility factor (K) was used to account for the effects of frozen and thawing soil. Yet the use of this factor requires observation data for calibration, and such a simplified approach cannot represent the complicated transient freeze-thaw processes and their impacts on surface runoff and erosion. The Water Erosion Prediction Project (WEPP) watershed model, a physically-based erosion prediction software developed by the USDA-ARS, has seen numerous applications within and outside the US. WEPP simulates winter processes, including snow accumulation, snowmelt, and soil freeze-thaw, using an approach based on mass and energy conservation. However, previous studies showed the inadequacy of the winter routines in the WEPP model. Therefore, the objectives of this study were: (1) To adapt a modeling approach for winter hydrology based on mass and energy conservation, and to implement this approach into a physically-oriented hydrological model, such as WEPP; and (2) To assess this modeling approach through case applications to different geographic conditions. A new winter routine was developed and its performance was evaluated by incorporating it into WEPP (v2008.9) and then applying WEPP to four study sites at different spatial scales under different climatic conditions, including experimental plots in Pullman, WA and Morris, MN, two agricultural drainages in Pendleton, OR, and a forest watershed in Mica Creek, ID. The model applications showed promising results, indicating adequacy of the mass- and energy-balance-based approach for winter hydrology simulation.

Erosion products of plasma facing materials formed under ITER-like transient load and deuterium retention in them

DOE Office of Scientific and Technical Information (OSTI.GOV)

Putrik, A. B., E-mail: putrik@triniti.ru; Klimov, N. S.; Gasparyan, Yu. M., E-mail: yura@plasma.mephi.ru

2015-12-15

Erosion of the plasma-facing materials in particular evaporation of the materials in a fusion reactor under intense transient events is one of the problems of the ITER. The current experimental data are insufficient to predict the properties of the erosion products, a significant part of which will be formed during transient events (edge-localized modes (ELMs) and disruptions). The paper concerns the experimental investigation of the graphite and tungsten erosion products deposited under pulsed plasma load at the QSPA-T: heat load on the target was 2.6 MJ/m{sup 2} with 0.5 ms pulse duration. The designed diagnostics for measuring the deposition ratemore » made it possible to determine that the deposition of eroded material occurs during discharge, and the deposition rate is in the range (0.1–100) × 10{sup 19} at/(cm{sup 2} s), which is much higher than that for stationary processes. It is found that the relative atomic concentrations D/C and D/(W + C) in the erosion products deposited during the pulse process are on the same level as for the stationary processes. An exposure of erosion products to photonic energy densities typical of those expected at mitigated disruptions in the ITER (pulse duration of 0.5–1 ms, integral energy density of radiation of 0.1–0.5 MJ/m2) significantly decreases the concentration of trapped deuterium.« less

Modeling sediment transport after ditch network maintenance of a forested peatland

NASA Astrophysics Data System (ADS)

Haahti, K.; Marttila, H.; Warsta, L.; Kokkonen, T.; Finér, L.; Koivusalo, H.

2016-11-01

Elevated suspended sediment (SS) loads released from peatlands after drainage operations and the resulting negative effect on the ecological status of the receiving water bodies have been widely recognized. Understanding the processes controlling erosion and sediment transport within the ditch network forms a prerequisite for adequate sediment control. While numerous experimental studies have been reported in this field, model based assessments are rare. This study presents a modeling approach to investigate sediment transport in a peatland ditch network. The transport model describes bed erosion, rain-induced bank erosion, floc deposition, and consolidation of the bed. Coupled to a distributed hydrological model, sediment transport was simulated in a 5.2 ha forestry-drained peatland catchment for 2 years after ditch cleaning. Comparing simulation results to measured SS concentrations suggested that the loose peat material, produced during excavation, contributed markedly to elevated SS concentrations immediately after ditch cleaning. Both snowmelt and summer rainstorms contributed critically to annual loads. Springtime peat erosion during snowmelt was driven by ditch flow whereas during summer rainfalls, bank erosion by raindrop impact was identified as an important process. Relating modeling results to observed spatial topographic changes in the ditch network was challenging and the results were difficult to verify. Nevertheless, the model has potential to identify risk areas for erosion. The results demonstrate that modeling is effective in separating the importance of different processes and complements pure experimental approaches. Modeling results can aid planning and designing efficient sediment control measures and guide the focus of experimental studies.

Statistical characterization of wind-wave induced sediment resuspension events in shallow tidal basins

NASA Astrophysics Data System (ADS)

D'Alpaos, A.; Carniello, L.; Rinaldo, A.

2013-12-01

Wind-wave induced erosion processes play a critical role on the morphodynamic evolution of shallow tidal landscapes. Both in the horizontal and in the vertical planes, patterns of wind-induced bottom shear stresses contribute to control the morphological and biological features of the tidal landscape, through the erosion of tidal-flat surfaces and of salt-marsh margins, the disruption of the polymeric microphytobenthic biofilm, and the increase in suspended sediment concentration which affects the stability of intertidal ecosystems. Towards the goal of developing a synthetic theoretical framework to represent wind wave-induced resuspension events and account for their erosional effects on the long-term biomorphodynamic evolution of tidal systems, we have employed a complete, coupled finite element model accounting for the role of wind waves and tidal currents on the hydrodynamic circulation in shallow basins. Our analysis of the characteristics of combined current and wave-induced exceedances in bottom shear stress over a given threshold for erosion, suggest that wind wave-induced resuspension events can be modeled as a marked Poisson process. Moreover, the analysis of wind-wave induced resuspension events for different historical configurations of the Venice Lagoon shows that the interarrival times of erosion events have decreased through the last two centuries, whereas the intensities of erosion events have increased. This allows us to characterize the threatening erosion and degradation processes that the Venice Lagoon has been experiencing since the beginning of the last century.

Arroyo channel head evolution in a flash-flood-dominated discontinuous ephemeral stream system

USGS Publications Warehouse

DeLong, Stephen B.; Johnson, Joel P.L.; Whipple, Kelin X.

2014-01-01

We study whether arroyo channel head retreat in dryland discontinuous ephemeral streams is driven by surface runoff, seepage erosion, mass wasting, or some combination of these hydrogeomorphic processes. We monitored precipitation, overland flow, soil moisture, and headcut migration over several seasonal cycles at two adjacent rangeland channel heads in southern Arizona. Erosion occurred by headward retreat of vertical to overhanging faces, driven dominantly by surface runoff. No evidence exists for erosion caused by shallow-groundwater–related processes, even though similar theater-headed morphologies are sometimes attributed to seepage erosion by emerging groundwater. At our field site, vertical variation in soil shear strength influenced the persistence of the characteristic theater-head form. The dominant processes of erosion included removal of grains and soil aggregates during even very shallow (1–3 cm) overland flow events by runoff on vertical to overhanging channel headwalls, plunge-pool erosion during higher-discharge runoff events, immediate postrunoff wet mass wasting, and minor intra-event dry mass wasting on soil tension fractures developing subparallel to the headwall. Multiple stepwise linear regression indicates that the migration rate is most strongly correlated with flow duration and total precipitation and is poorly correlated with peak flow depth or time-integrated flow depth. The studied channel heads migrated upslope with a self-similar morphologic form under a wide range of hydrological conditions, and the most powerful flash floods were not always responsible for the largest changes in landscape form in this environment. 

Simulation of the erosion and drainage development of Loess surface based on GIS

NASA Astrophysics Data System (ADS)

Wang, Chun; Tang, Guoan; Ge, Shanshan; Li, Zhanbin; Zhou, Jieyu

2006-10-01

The research probes into the temporal-spatial process of drainage development of Loess Plateau on the basis of a carefully designed experiment. In the experiment, the development of a simulated loess watershed is tested under the condition of lab-simulated rainfall. A close-range photogrammetry survey is employed to establish a series of high precision and resolution DEM (Digit Elevation Model) of the simulated loess surface. Based on the established DEM, the erosion loss, the slope distribution, the topographic index , the gully-brink, and the drainage networks are all derived and discussed through comparison analysis and experimental validation. All the efforts aim at revealing the process and mechanism of erosion and drainage development of loess surface .This study demonstrates: 1) the stimulation result can effectively reflect the truth if those experimental conditions, i.e. loess soil structure, simulated rainfall, are adjusted in accord with true situation; 2) the remarkable character of the erosion and drainage up-growth of loess surface include the drainage traced to the source, the increased of the drainage's density, the enlarged of gully, the durative variety of multiple terrain factor's mean value and its distribution, such as slope and topographic index; 3) The slope spectrum is the more felicitous terrain factor for depicting the erosion and drainage development of loess surface, including the rule of erosion and evolution process. It is the new way and mean for studying the loess physiognomy.

Modelling river bank retreat by combining fluvial erosion, seepage and mass failure

NASA Astrophysics Data System (ADS)

Dapporto, S.; Rinaldi, M.

2003-04-01

Streambank erosion processes contribute significantly to the sediment yielded from a river system and represent an important issue in the contexts of soil degradation and river management. Bank retreat is controlled by a complex interaction of hydrologic, geotechnical, and hydraulic processes. The capability of modelling these different components allows for a full reconstruction and comprehension of the causes and rates of bank erosion. River bank retreat during a single flow event has been modelled by combining simulation of fluvial erosion, seepage, and mass failures. The study site, along the Sieve River (Central Italy), has been subject to extensive researches, including monitoring of pore water pressures for a period of 4 years. The simulation reconstructs fairly faithfully the observed changes, and is used to: a) test the potentiality and discuss advantages and limitations of such type of methodology for modelling bank retreat; c) quantify the contribution and mutual role of the different processes determining bank retreat. The hydrograph of the event is divided in a series of time steps. Modelling of the riverbank retreat includes for each step the following components: a) fluvial erosion and consequent changes in bank geometry; b) finite element seepage analysis; c) stability analysis by limit equilibrium method. Direct fluvial shear erosion is computed using empirically derived relationships expressing lateral erosion rate as a function of the excess of shear stress to the critical entrainment value for the different materials along the bank profile. Lateral erosion rate has been calibrated on the basis of the total bank retreat measured by digital terrestrial photogrammetry. Finite element seepage analysis is then conducted to reconstruct the saturated and unsaturated flow within the bank and the pore water pressure distribution for each time step. The safety factor for mass failures is then computed, using the pore water pressure distribution obtained by the seepage analysis, and the geometry of the upper bank is modified in case of failure.

Modelling soil carbon fate under erosion process in vineyard

NASA Astrophysics Data System (ADS)

Novara, Agata; Scalenghe, Riccardo; Minacapilli, Mario; Maltese, Antonino; Capodici, Fulvio; Borgogno Mondino, Enrico; Gristina, Luciano

2017-04-01

Soil erosion processes in vineyards beyond water runoff and sediment transport have a strong effect on soil organic carbon loss (SOC) and redistribution along the slope. The variation of SOC across the landscape determines a difference in soil fertility and vine productivity. The aim of this research was to study erosion of a Mediterranean vineyard, develop an approach to estimate the SOC loss, correlate the vines vigor with sediment and carbon erosion. The study was carried out in a Sicilian (Italy) vineyard, planted in 2011. Along the slope, six pedons were studied by digging 6 pits up to 60cm depth. Soil was sampled in each pedon every 10cm and SOC was analyzed. Soil erosion, detachment and deposition areas were measured by pole height method. The vigor of vegetation was expressed in term of NDVI (Normalized difference Vegetation Index) derived from a satellite image (RapidEye) acquired at berry pre-veraison stage (July) and characterized by 5 spectral bands in the shortwave region, including a band in the red wavelength (R, 630-685 nm) and in the near infrared (NIR, 760-850 nm) . Results showed that soil erosion, sediments redistribution and SOC across the hill was strongly affected by topographic features, slope and curvature. The erosion rate was 46Mg ha-1 y-1 during the first 6 years since planting. The SOC redistribution was strongly correlated with the detachment or deposition area as highlighted by pole height measurements. The approach developed to estimate the SOC loss showed that during the whole study period the off-farm SOC amounts to 1.6Mg C ha-1. As highlighted by NDVI results, the plant vigor is strong correlated with SOC content and therefore, developing an accurate NDVI approach could be useful to detect the vineyard areas characterized by low fertility due to erosion process.

Enhancing wind erosion monitoring and assessment for U.S. rangelands

USGS Publications Warehouse

Webb, Nicholas P.; Van Zee, Justin W.; Karl, Jason W.; Herrick, Jeffrey E.; Courtright, Ericha M.; Billings, Benjamin J.; Boyd, Robert C.; Chappell, Adrian; Duniway, Michael C.; Derner, Justin D.; Hand, Jenny L.; Kachergis, Emily; McCord, Sarah E.; Newingham, Beth A.; Pierson, Frederick B.; Steiner, Jean L.; Tatarko, John; Tedela, Negussie H.; Toledo, David; Van Pelt, R. Scott

2017-01-01

On the GroundWind erosion is a major resource concern for rangeland managers because it can impact soil health, ecosystem structure and function, hydrologic processes, agricultural production, and air quality.Despite its significance, little is known about which landscapes are eroding, by how much, and when.The National Wind Erosion Research Network was established in 2014 to develop tools for monitoring and assessing wind erosion and dust emissions across the United States.The Network, currently consisting of 13 sites, creates opportunities to enhance existing rangeland soil, vegetation, and air quality monitoring programs.Decision-support tools developed by the Network will improve the prediction and management of wind erosion across rangeland ecosystems.

Tree species and functional traits but not species richness affect interrill erosion processes in young subtropical forests

NASA Astrophysics Data System (ADS)

Seitz, S.; Goebes, P.; Song, Z.; Bruelheide, H.; Härdtle, W.; Kühn, P.; Li, Y.; Scholten, T.

2016-01-01

Soil erosion is seriously threatening ecosystem functioning in many parts of the world. In this context, it is assumed that tree species richness and functional diversity of tree communities can play a critical role in improving ecosystem services such as erosion control. An experiment with 170 micro-scale run-off plots was conducted to investigate the influence of tree species and tree species richness as well as functional traits on interrill erosion in a young forest ecosystem. An interrill erosion rate of 47.5 Mg ha-1 a-1 was calculated. This study provided evidence that different tree species affect interrill erosion differently, while tree species richness did not affect interrill erosion in young forest stands. Thus, different tree morphologies have to be considered, when assessing soil erosion under forest. High crown cover and leaf area index reduced interrill erosion in initial forest ecosystems, whereas rising tree height increased it. Even if a leaf litter cover was not present, the remaining soil surface cover by stones and biological soil crusts was the most important driver for soil erosion control. Furthermore, soil organic matter had a decreasing influence on interrill erosion. Long-term monitoring of soil erosion under closing tree canopies is necessary, and a wide range of functional tree traits should be considered in future research.

Sometimes processes don't matter: the general effect of short term climate variability on erosional systems.

NASA Astrophysics Data System (ADS)

Deal, Eric; Braun, Jean

2017-04-01

Climatic forcing undoubtedly plays an important role in shaping the Earth's surface. However, precisely how climate affects erosion rates, landscape morphology and the sedimentary record is highly debated. Recently there has been a focus on the influence of short-term variability in rainfall and river discharge on the relationship between climate and erosion rates. Here, we present a simple probabilistic argument, backed by modelling, that demonstrates that the way the Earth's surface responds to short-term climatic forcing variability is primarily determined by the existence and magnitude of erosional thresholds. We find that it is the ratio between the threshold magnitude and the mean magnitude of climatic forcing that determines whether variability matters or not and in which way. This is a fundamental result that applies regardless of the nature of the erosional process. This means, for example, that we can understand the role that discharge variability plays in determining fluvial erosion efficiency despite doubts about the processes involved in fluvial erosion. We can use this finding to reproduce the main conclusions of previous studies on the role of discharge variability in determining long-term fluvial erosion efficiency. Many aspects of the landscape known to influence discharge variability are affected by human activity, such as land use and river damming. Another important control on discharge variability, rainfall intensity, is also expected to increase with warmer temperatures. Among many other implications, our findings help provide a general framework to understand and predict the response of the Earth's surface to changes in mean and variability of rainfall and river discharge associated with the anthropogenic activity. In addition, the process independent nature of our findings suggest that previous work on river discharge variability and erosion thresholds can be applied to other erosional systems.

Morphological evolution of Jinshan Trough in Hangzhou Bay (China) from 1960 to 2011

NASA Astrophysics Data System (ADS)

Liu, Yifei; Xia, Xiaoming; Chen, Shenliang; Jia, Jianjun; Cai, Tinglu

2017-11-01

An extensive system of tidal channels, starting with Jinshan Trough in the east, is located along the north shore of Hangzhou Bay, China. This contribution investigates the morphological evolution of Jinshan Trough by using 17 bathymetric charts from a series covering a period of 51 years from 1960 to 2011. Three stages of evolution during this period are distinguishable based on the morphology and annual mean volume data. The first stage (1960-1987) is characterized by extension of the trough; the second stage (1987-1996) is a relatively stable period with some adjustments in the trough morphology; the third stage (1996-2011) is marked by the processes of erosion and deposition in the beginning of the period and a subsequent slow erosion process. Spatio-temporal variability of the trough was evaluated by using empirical orthogonal function (EOF) analysis. The first eigenfunction indicates that erosion is the main evolution process and there exists three stages similar to those distinguished from volume variations. The second eigenfunction mainly reflects erosion and deposition in the northwest part of the trough located in the flood tidal current shadow area of the artificial headland in Jinshan. The third eigenfunction mainly reflects annual fluctuations of erosion and deposition in the side slope at the artificial headland in Jinshan. A particularly intense erosion process occurred between 1996 and 1998. The major effects on morphological evolution in Jinshan Trough from 1960 to 2011 were investigated and tentative conclusions were presented. Continuous coastal reclamations in Jinshan had the most pronounced effect on the morphological evolution during the first and the second stages. The storm surge had a pronounced effect on the evolution at the beginning of the third stage.

Calculating erosion rates of river bank sediment by combining field measurements of erodibility parameters and small-scale topographic features – A case study at the Danube River

USDA-ARS?s Scientific Manuscript database

This paper examines the application of a method for calculating fluvial erosion on river banks. In the investigated area the determination of potential erosion rates are essential to estimating the initiated river widening processes and their effect on navigation. A mini-jet device was employed, for...

The origin and significance of sinuosity along incising bedrock rivers

NASA Astrophysics Data System (ADS)

Barbour, Jonathan Ross

Landscapes evolve through processes acting at the earth's surface in response to tectonics and climate. Rivers that cut into bedrock are particularly important since they set the local baselevel and communicate changes in boundary conditions across the landscape through erosion and deposition; the pace of topographic evolution depends on both the rate of change of the boundary conditions and the speed of the bedrock channel network response. Much of the work so far has considered the effects of tectonically-controlled changes in slope and climatically-controlled changes in discharges to the rate of channel bed erosion while considering bank erosion, if active at all, to be of at best secondary importance to landscape evolution. Sprinkled throughout the literature of the past century are studies that have recognized lateral activity along incising rivers, but conflicting interpretations have left many unanswered questions about how to identify and measure horizontal erosion, what drives it, what effect it has on the landscape, and how it responds to climate and tectonics. In this thesis, I begin to answer some of these questions by focusing on bedrock river sinuosity and its evolution through horizontal erosion of the channel banks. An analysis of synoptic scale topography and climatology of the islands of eastern Asia reveals a quantitative signature of storm frequency in a regional measure of mountain river sinuosity. This is partly explained through a study of the hydro- and morphodynamics of a rapidly evolving bedrock river in Taiwan which shows how the erosive forces vary along a river to influence the spatiotemporal distribution of downcutting, sidecutting, and sediment transport. Through these analyses, I also present evidence that suggests that the relative frequency of erosive events is far more important than the absolute magnitude of extreme events in setting the erosion rate, and I show that the horizontal erosion of bedrock rivers is an important contributor to landscape evolution. This thesis comprises a new look at the processes at work in bedrock rivers which suggests new ideas about the ways that landscape and climate interact, new tools for interpreting landscape morphology, and new insights into the processes that contribute to the evolution of active orogens.

Electromagnetic dissociation of U-238 in heavy-ion collisions at 120 MeV/A

NASA Astrophysics Data System (ADS)

Justice, M. L.

1991-04-01

This thesis describes a measurement of the heavy-ion induced electromagnetic dissociation of a 120 MeV/A U-238 beam incident on five targets: Be-9, Al-27, Cu, Ag, and U. Electromagnetic dissociation at this beam energy is essentially a two step process involving the excitation of a giant resonance followed by particle decay. At 120 MeV/A there is predicted to be a significant contribution of the giant quadrupole resonance to the EMD cross sections. The specific exit channel which was looked at was projectile fission. The two fission fragments were detected in coincidence by an array of solid-state (Delta)E-E detectors, allowing the changes of the fragments to be determined to within (+/-) .5 units. The events were sorted on the basis of the sums of the fragments' charges, acceptance corrections were applied, and total cross sections for the most peripheral events were determined. Electromagnetic fission at the beam energy of this experiment always leads to a true charge sum of 92. Due to the imperfect resolution of the detectors, charge sums of 91 and 93 were included in order to account for all of the electromagnetic fission events. The experimentally observed cross sections are due to nuclear interaction processes as well as electromagnetic processes. Under the conditions of this experiment, the cross sections for the beryllium target are almost entirely due to nuclear processes. The nuclear cross sections for the other four targets were determined by extrapolation from the beryllium data using a geometrical scaling model. After subtraction of the nuclear cross sections, the resulting electromagnetic cross sections are compared to theoretical calculations based on the equivalent photon approximation. Systematic uncertainties are discussed and suggestions for improving the experiment are given.

Quantitative comparison of initial soil erosion processes and runoff generation in Spanish and German vineyards.

PubMed

Rodrigo Comino, J; Iserloh, T; Lassu, T; Cerdà, A; Keestra, S D; Prosdocimi, M; Brings, C; Marzen, M; Ramos, M C; Senciales, J M; Ruiz Sinoga, J D; Seeger, M; Ries, J B

2016-09-15

The aim of this study was to enable a quantitative comparison of initial soil erosion processes in European vineyards using the same methodology and equipment. The study was conducted in four viticultural areas with different characteristics (Valencia and Málaga in Spain, Ruwer-Mosel valley and Saar-Mosel valley in Germany). Old and young vineyards, with conventional and ecological planting and management systems were compared. The same portable rainfall simulator with identical rainfall intensity (40mmh(-1)) and sampling intervals (30min of test duration, collecting the samples at 5-min-intervals) was used over a circular test plot with 0.28m(2). The results of 83 simulations have been analysed and correlation coefficients were calculated for each study area to identify the relationship between environmental plot characteristics, soil texture, soil erosion, runoff and infiltration. The results allow for identification of the main factors related to soil properties, topography and management, which control soil erosion processes in vineyards. The most important factors influencing soil erosion and runoff were the vegetation cover for the ecological German vineyards (with 97.6±8% infiltration coefficients) and stone cover, soil moisture and slope steepness for the conventional land uses. Copyright © 2016 Elsevier B.V. All rights reserved.

Evaluation and selection of indicators for land degradation and desertification monitoring: types of degradation, causes, and implications for management.

PubMed

Kairis, Or; Kosmas, C; Karavitis, Ch; Ritsema, C; Salvati, L; Acikalin, S; Alcalá, M; Alfama, P; Atlhopheng, J; Barrera, J; Belgacem, A; Solé-Benet, A; Brito, J; Chaker, M; Chanda, R; Coelho, C; Darkoh, M; Diamantis, I; Ermolaeva, O; Fassouli, V; Fei, W; Feng, J; Fernandez, F; Ferreira, A; Gokceoglu, C; Gonzalez, D; Gungor, H; Hessel, R; Juying, J; Khatteli, H; Khitrov, N; Kounalaki, A; Laouina, A; Lollino, P; Lopes, M; Magole, L; Medina, L; Mendoza, M; Morais, P; Mulale, K; Ocakoglu, F; Ouessar, M; Ovalle, C; Perez, C; Perkins, J; Pliakas, F; Polemio, M; Pozo, A; Prat, C; Qinke, Y; Ramos, A; Ramos, J; Riquelme, J; Romanenkov, V; Rui, L; Santaloia, F; Sebego, R; Sghaier, M; Silva, N; Sizemskaya, M; Soares, J; Sonmez, H; Taamallah, H; Tezcan, L; Torri, D; Ungaro, F; Valente, S; de Vente, J; Zagal, E; Zeiliguer, A; Zhonging, W; Ziogas, A

2014-11-01

Indicator-based approaches are often used to monitor land degradation and desertification from the global to the very local scale. However, there is still little agreement on which indicators may best reflect both status and trends of these phenomena. In this study, various processes of land degradation and desertification have been analyzed in 17 study sites around the world using a wide set of biophysical and socioeconomic indicators. The database described earlier in this issue by Kosmas and others (Environ Manage, 2013) for defining desertification risk was further analyzed to define the most important indicators related to the following degradation processes: water erosion in various land uses, tillage erosion, soil salinization, water stress, forest fires, and overgrazing. A correlation analysis was applied to the selected indicators in order to identify the most important variables contributing to each land degradation process. The analysis indicates that the most important indicators are: (i) rain seasonality affecting water erosion, water stress, and forest fires, (ii) slope gradient affecting water erosion, tillage erosion and water stress, and (iii) water scarcity soil salinization, water stress, and forest fires. Implementation of existing regulations or policies concerned with resources development and environmental sustainability was identified as the most important indicator of land protection.

Electromagnetic structure of the proton within the CP-violation hypothesis

DOE Office of Scientific and Technical Information (OSTI.GOV)

Krutov, A. F., E-mail: krutov@ssu.samara.ru; Kudinov, M. Yu., E-mail: kudinov@ssu.samara.ru

2013-11-15

The so-called non-Rosenbluth behavior of the proton electromagnetic form factors can be explained within the hypothesis of CP violation in electromagnetic processes involving composite systems of strongly interacting particles. It is shown that this hypothesis leads to the appearance of an additional, anapole, form factor of the proton. The proton electromagnetic form factors, including the anapole form factor, are estimated on the basis of experimental data on elastic electron-proton scattering.

Electromagnetic processes in nucleus-nucleus collisions relating to space radiation research

NASA Technical Reports Server (NTRS)

Norbury, John W.

1992-01-01

Most of the papers within this report deal with electromagnetic processes in nucleus-nucleus collisions which are of concern in the space radiation program. In particular, the removal of one and two nucleons via both electromagnetic and strong interaction processes has been extensively investigated. The theory of relativistic Coulomb fission has also been developed. Several papers on quark models also appear. Finally, note that the theoretical methods developed in this work have been directly applied to the task of radiation protection of astronauts. This has been done by parameterizing the theoretical formalism in such a fashion that it can be used in cosmic ray transport codes.

Real-time holographic surveillance system

DOEpatents

Collins, H.D.; McMakin, D.L.; Hall, T.E.; Gribble, R.P.

1995-10-03

A holographic surveillance system is disclosed including means for generating electromagnetic waves; means for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; means for receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; means for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and means for displaying the processed information to determine nature of the target. The means for processing the electrical signals includes means for converting analog signals to digital signals followed by a computer means to apply a backward wave algorithm. 21 figs.

Investigation of the Degradation Mechanisms of Particulate Reinforced Epoxy Coatings and Zinc-Rich Coatings Under an Erosion and Corrosion Environment for Oil and Gas Industry Applications

NASA Astrophysics Data System (ADS)

Wang, Dailin

During oil and gas production and transportation, the presence of an oil-sand slurry, together with the presence of CO2, H2S, oxygen, and seawater, create an erosive/abrasive and corrosive environment for the interior surfaces of undersea pipelines transporting oil and gas from offshore platforms. Erosion/wear and corrosion are often synergic processes leading to a much greater material loss of pipeline cross-section than that caused by each individual process alone. Both organic coatings and metallic sacrificial coatings have been widely employed to provide protection to the pipeline steels against corrosion through barrier protection and cathodic protection, and these protection mechanisms have been well studied. However, coating performance under the synergic processes of erosion/wear and corrosion have been much less researched and coating degradation mechanisms when erosion/wear and corrosion are both going on has not been well elucidated. In the work presented in this dissertation, steel panels coated with filler reinforced epoxy coatings and carbon nanotubes (CNTs) reinforced zinc-rich coatings have been evaluated under erosion/wear followed by an exposure to a corrosive environment. Electrochemical tests and material characterization methods have been applied to study the degradation mechanisms of the coatings during the tests and coating degradation mechanisms have been proposed. While organic coatings with a lower amount of filler particles provided better protection in a corrosive environment alone and in solid particle impingement erosion testing alone, organic coatings with a higher amount of filler particles showed better performance during wear testing alone. A higher amount of filler particles was also beneficial in providing protection against wear and corrosion environment, and erosion and corrosion environment. Coating thickness played a significant role in the barrier properties of the coatings under both erosion and corrosion tests. When the organic coatings were exposed to a corrosive environment with presence of H2S, thicker coatings provided better protection regardless of the amount and types of filler particles present in the coatings. For zinc-rich coatings, coatings with CNTs provided better barrier protection for the steel substrate than traditional zinc-rich coatings in a corrosive environment alone. However, the CNTs-filled zinc-rich epoxy coatings did not provide adequate protection when the coated specimens were exposed to erosion and corrosion.

Wind and Rock

NASA Image and Video Library

2011-03-09

This image from NASA Mars Odyssey is located west of Zephyria Planum. Surfaces in this region have undergone extensive erosion by the wind. Wind is one of the most active processes of erosion on the surface of Mars today.

The Rangeland Hydrology and Erosion Model

NASA Astrophysics Data System (ADS)

Nearing, M. A.

2016-12-01

The Rangeland Hydrology and Erosion Model (RHEM) is a process-based model that was designed to address rangelands conditions. RHEM is designed for government agencies, land managers and conservationists who need sound, science-based technology to model, assess, and predict runoff and erosion rates on rangelands and to assist in evaluating rangeland conservation practices effects. RHEM is an event-based model that estimates runoff, erosion, and sediment delivery rates and volumes at the spatial scale of the hillslope and the temporal scale of as single rainfall event. It represents erosion processes under normal and fire-impacted rangeland conditions. Moreover, it adopts a new splash erosion and thin sheet-flow transport equation developed from rangeland data, and it links the model hydrologic and erosion parameters with rangeland plant community by providing a new system of parameter estimation equations based on 204 plots at 49 rangeland sites distributed across 15 western U.S. states. A dynamic partial differential sediment continuity equation is used to model the total detachment rate of concentrated flow and rain splash and sheet flow. RHEM is also designed to be used as a calculator, or "engine", within other watershed scale models. From the research perspective RHEM acts as a vehicle for incorporating new scientific findings from rangeland infiltration, runoff, and erosion studies. Current applications of the model include: 1) a web site for general use (conservation planning, research, etc.), 2) National Resource Inventory reports to Congress, 3) as a computational engine within watershed scale models (e.g., KINEROS, HEC), 4) Ecological Site & State and Transition Descriptions, 5) proposed in 2015 to become part of the NRCS Desktop applications for field offices.

A Study on Tribological Behavior of Glass-Epoxy Composite Filled with Granite Dust

NASA Astrophysics Data System (ADS)

Ray, Subhrajit; Rout, Arun Ku; KuSahoo, Ashok

2017-08-01

Granite powder is one of the solid wastes generated from stone processing industry used as organic filler replacing the conventional ceramic fillers in polymer matrix composite to increase the mechanical properties. The present work investigates the addition of granite powder on erosion wear properties of epoxy-glass fiber composite. The solid particle erosion wear rates of these hybrid composites are recorded considering various control parameters as impingement angles, erodent sizes and impact velocities following erosion resistance test in an air erosion test device at room temperatures. The test was conducted as per the Taguchi experimental design to minimize the erosion loss of material. The SEM views show the surface resistivity for the granite added specimens. The microscopic study also indicates various methods of material removal, crater wear and other subjective allocation during erosion experiment of the samples.

Aeolian processes over gravel beds: Field wind tunnel simulation and its application atop the Mogao Grottoes, China

NASA Astrophysics Data System (ADS)

Zhang, Weimin; Tan, Lihai; Zhang, Guobin; Qiu, Fei; Zhan, Hongtao

2014-12-01

The aeolian processes of erosion, transport and deposition are threatening the Mogao Grottoes, a world culture heritage site. A field wind tunnel experiment was conducted atop the Mogao Grottoes using weighing sensors to quantify aeolian processes over protective gravel beds. Results reveal that aeolian erosion and deposition over gravel beds are basically influenced by gravel coverage and wind speed. Erosion is a main aeolian process over gravel beds and its strength level is mainly determined by gravel coverage: strong (<30%), medium (30-50%) and slight (>50%). Aeolian deposition only occurs when gravel coverage is equal to or greater than 30% and wind speeds are between 8 and 12 m s-1, and this process continues until the occurrence of the equilibrium coverage. In addition, the change in conditions of external sand supply affects the transition between aeolian deposition and erosion over gravel beds, and the quantity of sand transport at the height of 0-24 mm is an important indicator of aeolian deposition and erosion over gravel beds. Our results also demonstrate that making the best use of wind regime atop the Mogao Grottoes and constructing an artificial gobi surface in staggered arrays, with 30% coverage and 30-mm-high gravels and in 40 mm spacing can trap westerly invading sand flow and enable the stronger easterly wind to return the deposited sand on the gravel surface back to the Mingsha Mountain so as to minimize the damage of the blown sand flux to the Mogao Grottoes.

The fate of Salicaceae seedlings related to the dynamics of alluvial bars during floods: differentiating bed erosion, uprooting and burying.

NASA Astrophysics Data System (ADS)

Wintenberger, C. L.; Rodrigues, S.; Bréhéret, J. G.; Juge, P.; Villar, M.

2014-12-01

Riparian vegetation is a key factor of the morphological evolution of river. In Europe, riparian Salicaceae is declining following the loss of potential recruitment areas associated with river management. As an exception for lowland rivers, the Loire River (France) shows, in its middle reaches, an efficient sexual regeneration of Populus nigra and Salix alba on bare sediments deposited during flood events. In the literature, the influence of hydrological patterns as a key factor of the seedlings survival is well documented. Some studies focused on seedlings ability to withstand flood constraints and detailed the effect of duration and intensity of floods but few studies characterized precisely the processes applied on seedlings. As a working hypothesis, we consider that three types of flood stresses can induce mortality of seedlings: (i) uprooting by drag applied on the seedlings without sediment erosion, (ii) erosion of the recruited areas and (iii) burying. The distinction of these three processes allows identifying the importance of survival factors due to a strong sediment dynamics (e.g. erosion height > root height) or to the anchorage and resprouting ability. The main issues are: what are the governing processes (type and intensity) determining survival or death of seedlings and which factor (fluvial dynamics vs. own characteristics of seedlings) controls their survival? In-situ measurements were performed on a forced alluvial bar (20.000 m2) to detail the bar dynamics (bathymetry, topography, scour/fill processes, grain size surveys, flow velocity) and to survey the associated recruitment. On 48 plots (1.410 m2) the density, height and species (P. nigra and S. alba) were surveyed the year of recruitment (after dry period) and the next year after flood period. We highlight the following phases of processes during floods. The erosion of substrate dominates at the beginning of the rising limb. The erosion or uprooting processes depend of the balance between available bed shear stress and sediment size. Then the deposit occurs on the back of the bar before the peak discharge and protects them against uprooting by burying during the higher energy of flow. At the end of the falling limb, sediments are reworked, decreasing the burying height of seedlings and allowing possible uprooting (drag) or erosion of sediments.

Vegetation modulated landscape evolution: Effects of vegetation on landscape processes, drainage density and topography

NASA Astrophysics Data System (ADS)

Bras, R. L.; Istanbulluoglu, E.

2004-12-01

Topography acts as a template for numerous landscape processes that includes hydrologic, ecologic and biologic phenomena. These processes not only interact with each other but also contribute to shaping the landscape as they influence geomorphic processes. We have investigated the effects of vegetation on known geomorphic relations, thresholds for channel initiation and landform evolution, using both analytical and numerical approaches. Vegetation is assumed to form a uniform ground cover. Runoff erosion is modeled based on power function of excess shear stress, in which shear stress efficiency is inversely proportional to vegetation cover. Plant effect on slope stability is represented by additional cohesion provided by plant roots. Vegetation cover is assumed to reduce sediment transport rates due to physical creep processes (rainsplash, dry ravel, and expansion and contraction of sediments) according to a negative exponential relationship. Vegetation grows as a function of both available cover and unoccupied space by plants, and is killed by geomorphic disturbances (runoff erosion and landsliding), and wildfires. Analytical results suggest that, in an equilibrium basin with a fixed vegetation cover, plants may cause a transition in the dominant erosion process at the channel head. A runoff erosion dominated landscape, under none or loose vegetation cover, may become landslide dominated under a denser vegetation cover. The sign of the predicted relationship between drainage density and vegetation cover depends on the relative influence of vegetation on different erosion phenomena. With model parameter values representative of the Oregon Coast Range (OCR), numerical experiments conducted using the CHILD model. Numerical experiments reveal the importance of vegetation disturbances on the landscape structure. Simulated landscapes resemble real-world catchments in the OCR when vegetation disturbances are considered.

Changes in metal properties after thermal and electric impulse processing

NASA Astrophysics Data System (ADS)

Shaburova, N. A.

2015-04-01

The results of the experiments on processing metal melts by powerful electromagnetic impulses are given. The generator used in the experiments has the following characteristics: pulse height - 10KV, duration - 1ns, leading edge - 0.1ns, repetition rate - 1KHz, the output - 100KWt. The duration of the processing is 10-15min. The comparative analysis of the processed and unprocessed samples results in the changes of structure, increase of density, solidity, plasticity and resilience of cast metal. The result analysis of different external physical processing methods on alloys shows full agreement with the results of the ultrasonic processing of metals. The hypothesis of ultrasonic shock wave formation at the pulse front was adopted as the main mechanism of the electromagnetic impulse impact on alloys. The theoretical part of the research describes the transformation process of electromagnetic impulses into acoustic ones.

Erosion-vegetation dynamics in the Lucciolabella biancane badland cultural landscape (Southern Tuscany, Italy)

NASA Astrophysics Data System (ADS)

Maccherini, Simona; Vergari, Francesca; Santi, Elisa; Marignani, Michela; Della Seta, Marta; Rossi, Mauro; Torri, Dino; Del Monte, Maurizio

2014-05-01

In this work we present the results of multidisciplinary and long-lasting investigations on the complex cause-effect relationship among water erosion processes and vegetation cover on the Lucciolabella Natural Reserve, located in Upper Orcia Valley (Southern Tuscany). The area is a Site of Community Importance, where the cultural landscape of biancane badlands - water erosion landforms generated on Plio-Pleistocene marine clay outcrops - is preserved. We explored the direction and rate of change in land use and natural habitats of the biancana badland landscapes over the last 50 years, evaluating the erosion-vegetation dynamics and examining the processes involved in the biancana badland area. Historical information, such as early cadastral documents and diachronically analyzed aerial photographs, has been used to construct a database of the natural trends of modifications relative to habitat and plant species distribution, with the analysis of the consequent variations on the frequency of instability events. Old and recent land use maps were compared by using the TWINSPAN classification. Soil erodibility evaluation on the eroded biancana surfaces, regosols and well-developed vertisols, was carried out together with a decadal erosion monitoring program and the investigation of the physico-chemical properties of parent material. We also considered the effects of a few roots on saturated soil shear strength to introduce direct links between plants and soil processes. Moreover we run the LANDPLANER model in order to deepen the effect of the fragmentation of the vegetation cover on water erosion processes affecting biancana badlands. Long-lasting geomorphological survey and field erosion monitoring highlighted that biancana stations experience a very strong surface lowering rate due to water erosion, attaining an average rate of 2.4 - 2.6 cm/a. Moreover, biancanas in a more juvenile development phase, such as the ones of Lucciolabella Natural Reserve, show the maximum erosion rate, which reach more than 4 cm/a, and the most relevant dispersive clay fraction. The surface proneness to water erosion is enhanced by the wide presence of piping in the area. We showed that rills and subsurface micropipes are characterized by analogous erosion processes, meaning that they can be contrasted and eventually halted through a common mitigation strategy, and we observed a clear positive trend that will substantially suppress rilling at very low plant cover (no more than 20%). The analysis of the landscape changes showed a decrease in bare or scarcely vegetated spots of 0.9 ha/a during the last decades. Even if vegetation cover seems to stabilize upper layers of soil profile, rural abandonment and the lack of appropriate management practices have contributed to vegetation encroaching on biancana badland slopes mainly ascribed to generalist ruderal species, causing a loss of elements of high ecological and cultural values. If the encroachment continues to progress at this rate, in 35-40 years from now all the biancana domes will be completely re-vegetated. Badlands were previously kept alive by limited but nonetheless devastating grazing activities. If this picture is correct, then mimicking traditional badland grazing practices seems to be a necessary step towards saving the landscape and biodiversity that the protected areas were established to preserve.

Observations of paraglacial processes on glacier forelands in Aoraki/Mount Cook National Park, Southern Alps, New Zealand

NASA Astrophysics Data System (ADS)

Winkler, Stefan

2015-04-01

The large and extensively debris-covered valley glaciers in Aoraki/Mount Cook National Park immediate east of the Main Divide in the Southern Alps of New Zealand experienced a substantial frontal retreat and vertical downwasting during the past few decades, often connected with the development of a proglacial lake and retreat by calving. Their Holocene glacier forelands are characterised by huge lateral moraines and multi-ridged lateral moraine systems alongside smaller terminal moraines and frontal outwash heads. Placed within a very dynamic general geomorphological regime of various efficient process-systems, these Holocene glacier forelands are currently affected by substantial paraglacial modification. These paraglacial processes have already caused some consequences for the touristic infrastructure in the area and are likely to cause further problems for the accessibility of established tramping routes, tourist huts, and lookouts in the near and medium future. One of the first steps in a project under development presented here is a detailed visual comparison of changes documented during the past 15 Years on the glacier forelands of Hooker, Mueller and Tasman Glaciers in Aoraki/Mount Cook National Park. It reveals considerable erosion especially on the proximal slopes of the lateral moraines by gully development and retreat of erosion scars at their crest in order of several metres in just a few years. Different processes contribute to high erosion rates, among others rill erosion connected to mid-slope springs that only are temporarily active following substantial rainfall events, efficient gully incision, and slumping. Although any quantification of the actual erosion rates is just preliminary and further studies are necessary in order to make reliable predictions for future development, the amount of paraglacial erosion in this environment is very high compared to other regions and highlights the current importance of the paraglacial process-system in the Southern Alps.

Soil erosion and sediment production on watershed landscapes: Processes and control

Treesearch

Peter F. Ffolliott; Kenneth N. Brooks; Daniel G. Neary; Roberto Pizarro Tapia; Pablo Garcia-Chevesich

2013-01-01

Losses of the soil resources from otherwise productive and well functioning watersheds is often a recurring problem confronting hydrologists and watershed managers. These losses of soil have both on-site and off-site effects on the watershed impacted. In addition to the loss of inherent soil resources through erosion processes, on-site effects can include the breakdown...

Distribution and local hydrographic impact of rapid permafrost degradation by thermo-erosion and gullying of ice-wedge polygons in glacier valley C-79 on on Bylot Island , Nunavut, Canada

NASA Astrophysics Data System (ADS)

Godin, E.; Fortier, D.

2010-12-01

Glaciers flowing from local ice-cap in the Canadian High-Arctic often feed fluvio-glacial outwashes flowing toward the sea. These fluvio-glacial outwashes are often bordered by terraces in which ice-wedge polygons developed during the Holocene (Fortier et al. 2004). In the valley of glacier C-79 on Bylot Island, Nunavut (N 73° 09’ - W 79° 57’) these ice-wedge polygons were recently destabilized very rapidly by processes of thermo-erosion related to surface run-off. Thirty-five such gullies were identified, mapped by remote sensing, characterized and georeferenced in detail during field surveys in 2009-2010. The objectives of this paper are to: 1) quantify the area and shape of gully systems in the valley of glacier C-79 in relation with its depositional environment and 2) evaluate the impact of gully development on the local hydrography in the valley. Degradation of permafrost by thermo-erosion processes is very active in the valley C-79. It covered in 2010 an area of approximately 152000 m2, the average gully length was 542 m with a maximum of 3520 m. Thermo-erosion gullies induced by snowmelt runoff water were formed in 3 distinct depositional environments within the valley: 1) in aeolian, organic-poor deposits near the pro-glacial river outwash, 2) in organic-rich, humid, ice-wedges polygon terraces, and 3) in colluviums close to the valley walls. Thermo-erosion of ice wedge polygons resulted in typical landforms such as: sinkholes and tunnels, gully channels with alluvial levees, retrogressive thaw-slump, active layer detachment slide and baydjarakhs (Godin and Fortier, in press). Positive feedback effects, especially at the gully head and around sinkholes, sustain processes of thermo-erosion and enhance permafrost degradation. Thermo-erosion processes and associated heat transfers combined with the effects of gullying significantly affected ice-wedges polygons terraces. The formation of gullies created permanent changes in the landscape and in the hydrographic network such as the total or partial destruction of polygons, drainage of adjacent wetlands and the birth of new drainage systems (Fortier et al. 2007). The hydrographic network layout is affected by newly formed gullies, streams running on the terrace being diverted from their beds toward gully systems. A stabilized gully where thermo-erosion is no more active will continue to drain the terrace and thus these processes causes irreversible changes to the geomorphic configuration of ice wedge polygon terraces. Fortier, D., Allard, M., Shur, Y. 2007. Observation of Rapid Drainage System Development by Thermal Erosion of Ice Wedges on Bylot Island, Canadian Arctic Archipelago. Permafrost and Periglacial Processes, 18: 229-243. Fortier, D., Allard, M. 2004. Late Holocene Syngenetic Ice-wedge Polygons Development, Bylot Island, Canadian Arctic Archipelago. Canadian Journal of Earth Sciences, 41: 997-1012. Godin, E., Fortier, D. (in press) Geomorphology of thermo-erosion gullies - case study from Bylot Island, Nunavut, Canada. Proceedings 6th Canadian Permafrost Conference and 63rd Canadian Geotechnical Conference, Calgary, October 2010.

Mass Loss of Coal Particles Burning in Fluidized Bed

NASA Astrophysics Data System (ADS)

Pełka, Piotr

2017-06-01

In this work many conclusions resulting from research carried out on the coal combustion process of the chosen coal type and its accompanying erosion in a two-phase flow of inert material have been presented. The purpose of this flow was to present a model of the conditions of the central and upper zone of the combustion chamber of the fluidized boiler. In the opinion of many authors (Basu, 1999; Chirone et al., 1991), the erosion process results from the contact of a fuel particle with particles of inert material that is responsible for generating fine fuel particles of less than 100 mm. If the particles are in the upper zone of the boiler where there is oxygen deficit, they can increase the loss of incomplete combustion substantially. The results of research do not confirm this common thesis, but rather indicate that the process of comminution that results from erosion under oxidative conditions contributes to the increase of substantial mass loss of a coal particle, however the increased mass loss of particle during combustion is first and foremost due to the whole process of removal of ash from the reactionary surface of a fuel particle. Nevertheless, in the conditions of oxygen deficit the comminution of particles as a result of the erosion process is negligible

Time compression of soil erosion by the effect of largest daily event. A regional analysis of USLE database.

NASA Astrophysics Data System (ADS)

Gonzalez-Hidalgo, J. C.; Batalla, R.; Cerda, A.; de Luis, M.

2009-04-01

When Thornes and Brunsden wrote in 1977 "How often one hears the researcher (and no less the undergraduate) complain that after weeks of observation "nothing happened" only to learn that, the day after his departure, a flood caused unprecedent erosion and channel changes!" (Thornes and Brunsden, 1977, p. 57), they focussed on two different problems in geomorphological research: the effects of extreme events and the temporal compression of geomorphological processes. The time compression is one of the main characteristic of erosion processes. It means that an important amount of the total soil eroded is produced in very short temporal intervals, i.e. few events mostly related to extreme events. From magnitude-frequency analysis we know that few events, not necessarily extreme by magnitude, produce high amount of geomorphological work. Last but not least, extreme isolated events are a classical issue in geomorphology by their specific effects, and they are receiving permanent attention, increased at present because of scenarios of global change. Notwithstanding, the time compression of geomorphological processes could be focused not only on the analysis of extreme events and the traditional magnitude-frequency approach, but on new complementary approach based on the effects of largest events. The classical approach define extreme event as a rare event (identified by its magnitude and quantified by some deviation from central value), while we define largest events by the rank, whatever their magnitude. In a previous research on time compression of soil erosion, using USLE soil erosion database (Gonzalez-Hidalgo et al., EGU 2007), we described a relationship between the total amount of daily erosive events recorded by plot and the percentage contribution to total soil erosion of n-largest aggregated daily events. Now we offer a further refined analysis comparing different agricultural regions in USA. To do that we have analyzed data from 594 erosion plots from USLE database with different record periods, and located in different climatic regions. Results indicate that there are no significant differences in the mean contribution of aggregated 5-largest daily erosion events between different agricultural divisions (i.e. different regional climate), and the differences detected can be attributed to specific site and plots conditions. Expected contribution of 5-largest daily event for 100 total daily events recorded is estimated around 40% of total soil erosion. We discuss the possible causes of such results and the applicability of them to the design of field research on soil erosion plots.

Minor soil erosion contribution to denudation in Central Nepal Himalaya.

NASA Astrophysics Data System (ADS)

Morin, Guillaume; France-Lanord, Christian; Gallo, Florian; Lupker, Maarten; Lavé, Jérôme; Gajurel, Ananta

2013-04-01

In order to decipher river sediments provenance in terms of erosion processes, we characterized geochemical compositions of hillslope material coming from soils, glaciers and landslide, and compared them to rivers sediments. We focused our study on two South flank Himalayan catchments: (1) Khudi khola, as an example of small High Himalayan catchment (150 km2), undergoing severe precipitation, and rapid erosion ≈ 3.5 mm/yr [A] and (2) the Narayani-Gandak Transhimalayan basin (52000 km2) that drains the whole central Nepal. To assess the question, systematic samplings were conducted on hillslope material from different erosion processes in the basins. River sediment include daily sampling during the 2010 monsoon at two stations, and banks samples in different parts of the basins. Source rocks, soil and landslide samples, are compared to river sediment mobile to immobile element ratios, completed by hydration degree H2O+ analysis[2]. Data show that soils are clearly depleted in mobile elements Na, K, Ca, and highly hydrated compared to source rocks and other erosion products. In the Khudi basin, the contrast between soil and river sediment signatures allow to estimate that soil erosion represents less than 5% of the total sediment exported by the river. Most of the river sediment therefore derives from landslides inputs and to a lesser extent by barren high elevation sub-basins. This is further consistent with direct observation that, during monsoon, significant tributaries of the Khudi river do not export sediments. Considering that active landslide zones represent less than 0.5% of the total watershed area, it implies that erosion distribution is highly heterogeneous. Landslide erosion rate could reach more than 50 cm/yr in the landslide area. Sediments of the Narayani river are not significantly different from those of the Khudi in spite of more diverse geomorphology and larger area of the basin. Only H2O+ and Total Organic Carbon concentrations normalised to Al/Si ratios show distinctly higher values. This suggests that contribution of soil erosion is higher than in the Khudi basin. Nevertheless, soil erosion remains a minor source of sediments implying that more physical processes such as landslide and glaciers dominate the erosional flux. In spite of high deforestation and agricultural land-use [B], soil erosion does not represent an important source of sediments in Nepal Himalaya. [A] Gabet et al. (2008) Earth and Planetary Science Letters 267, 482-494. [B] Gardner et al. (2003) Applied Geography 23, 23-45.

Heterogeneity and topsoil depletion due to tillage erosion and soil co-extraction with root vegetables: a serious threat to sustainable agricultural land use in the UK

NASA Astrophysics Data System (ADS)

Quine, Timothy; van Oost, Kristof

2010-05-01

The term soil erosion has become almost synonymous with water erosion and yet tillage erosion and soil loss with root crop harvest, although less visible, may be responsible for the majority of the on-site costs of soil erosion in many arable areas of the UK. The study reported here is a first attempt to model soil erosion associated with these processes in England and Wales, at the National scale. A GIS-based modelling approach in the Arc/Info environment is employed in order to meet the requirement for large-scale evaluation of erosion severity. Existing models that have been subject to independent test are used or adapted and widely available data is employed in model parameterisation. Tillage erosion is simulated using a diffusion-type model and a slope curvature index derived from coarse-scale topographic data. The curvature index is calibrated by statistical comparison to curvature values derived from a high resolution digital terrain model. Soil loss with root crop harvest is simulated using information concerning patterns of sugar beet and potato cultivation and estimation of soil moisture during the crop harvest season. Soil loss associated with root crop harvest may be as high as 1 t ha-1 year-1 if land is permanently used for root crops in a 3 year rotation. However, when the arable area of the UK is considered as a whole root crop harvest is responsible for a mean rate of soil loss of approximately 0.1 t ha-1 year-1. Tillage erosion is found to be the dominant process of soil redistribution and onsite erosion on arable land, in comparison with both soil loss through root crop harvest and with long-term water erosion rates. Mean gross rates of tillage erosion were found to be 3.7 t ha-1 year-1, representing approximately 7.4 t ha-1 year-1 erosion and the same rate of deposition. Soil redistribution at these rates is generating an heterogeneous soilscape in which continued functioning for food and fibre production may be jeopardized. These problems may be exacerbated by increased water stress in eroded soils if climate change does, as predicted, result in hotter and drier summers.

Prescribed Fire Effects on Runoff, Erosion, and Soil Water Repellency on Steeply-Sloped Sagebrush Rangeland over a Five Year Period

NASA Astrophysics Data System (ADS)

Williams, C. J.; Pierson, F. B.; Al-Hamdan, O. Z.

2014-12-01

Fire is an inherent component of sagebrush steppe rangelands in western North America and can dramatically affect runoff and erosion processes. Post-fire flooding and erosion events pose substantial threats to proximal resources, property, and human life. Yet, prescribed fire can serve as a tool to manage vegetation and fuels on sagebrush rangelands and to reduce the potential for large catastrophic fires and mass erosion events. The impact of burning on event hydrologic and erosion responses is strongly related to the degree to which burning alters vegetation, ground cover, and surface soils and the intensity and duration of precipitation. Fire impacts on hydrologic and erosion response may be intensified or reduced by inherent site characteristics such as topography and soil properties. Parameterization of these diverse conditions in predictive tools is often limited by a lack of data and/or understanding for the domain of interest. Furthermore, hydrologic and erosion functioning change as vegetation and ground cover recover in the years following burning and few studies track these changes over time. In this study, we evaluated the impacts of prescribed fire on vegetation, ground cover, soil water repellency, and hydrologic and erosion responses 1, 2, and 5 yr following burning of a mountain big sagebrush community on steep hillslopes with fine-textured soils. The study site is within the Reynolds Creek Experimental Watershed, southwestern Idaho, USA. Vegetation, ground cover, and soil properties were measured over plot scales of 0.5 m2 to 9 m2. Rainfall simulations (0.5 m2) were used to assess the impacts of fire on soil water repellency, infiltration, runoff generation, and splash-sheet erosion. Overland flow experiments (9 m2) were used to assess the effects of fire-reduced ground cover on concentrated-flow runoff and erosion processes. The study results provide insight regarding fire impacts on runoff, erosion, and soil water repellency in the immediate and short-term post-fire recovery years for steeply-sloped sagebrush sites with fine-textured soils. The study results also serve to inform development and enhancement of the Rangeland Hydrology and Erosion Model for predicting runoff and erosion responses from disturbed and undisturbed sagebrush rangelands.

Soil erosion by snow gliding - a first quantification attempt in a sub-alpine area, Switzerland

NASA Astrophysics Data System (ADS)

Meusburger, K.; Leitinger, G.; Mabit, L.; Mueller, M. H.; Walter, A.; Alewell, C.

2014-03-01

Snow processes might be one important driver of soil erosion in Alpine grasslands and thus the unknown variable when erosion modelling is attempted. The aim of this study is to assess the importance of snow gliding as soil erosion agent for four different land use/land cover types in a sub-alpine area in Switzerland. We used three different approaches to estimate soil erosion rates: sediment yield measurements in snow glide deposits, the fallout radionuclide 137Cs, and modelling with the Revised Universal Soil Loss Equation (RUSLE). The RUSLE model is suitable to estimate soil loss by water erosion, while the 137Cs method integrates soil loss due to all erosion agents involved. Thus, we hypothesise that the soil erosion rates determined with the 137Cs method are higher and that the observed discrepancy between the soil erosion rate of RUSLE and the 137Cs method is related to snow gliding and sediment concentrations in the snow glide deposits. Cumulative snow glide distance was measured for the sites in the winter 2009/10 and modelled for the surrounding area with the Spatial Snow Glide Model (SSGM). Measured snow glide distance ranged from 2 to 189 cm, with lower values at the north facing slopes. We observed a reduction of snow glide distance with increasing surface roughness of the vegetation, which is important information with respect to conservation planning and expected land use changes in the Alps. Our hypothesis was confirmed: the difference of RUSLE and 137Cs erosion rates was related to the measured snow glide distance (R2= 0.64; p < 0.005) and snow sediment yields (R2 = 0.39; p = 0.13). A high difference (lower proportion of water erosion compared to total net erosion) was observed for high snow glide rates and vice versa. The SSGM reproduced the relative difference of the measured snow glide values under different land uses and land cover types. The resulting map highlighted the relevance of snow gliding for large parts of the investigated area. Based on these results, we conclude that snow gliding is a key process impacting soil erosion pattern and magnitude in sub-alpine areas with similar topographic and climatic conditions.

Trend of Soil Erosion Processes within the Southern Half of the Russian Plain for the Last Decades

NASA Astrophysics Data System (ADS)

Golosov, V. N.; Yermolaev, O. P.; Safina, G. R.; Maltsev, K. A.; Gusarov, A. V.; Rysin, I. I.

2018-01-01

Complex approach is applied for assessment of recent trends of sheet, rill and gully erosion in different landscape zones of study area. Investigation is undertaken in 6 selected sectors (area of each transect is about 6-10 thousand km2), uniformly distributed over the area of the Russian Plain. Changes of the different factors, including some meteorological and hydrological parameters, land use change, USLE C-factor, were determined for the period 1980-2015. A set of field methods was used for quantification of sediment redistribution rates for the key small catchments. It was found that erosion rate decreased in forest and forest-steppe zone. Gully density decreases considerably in all landscape zones. The reduction of surface runoff from cultivated slope during snow-melting is the main reason of decreasing of sheet, rill and gully erosion rates in the forest, forest steppe and the north of steppe landscape zones. Increasing the proportion of perennial grasses in crop-rotation is the other factor of serious reduction of erosion processes in the forest zone.

Crop production and economic loss due to wind erosion in hot arid ecosystem of India

NASA Astrophysics Data System (ADS)

Santra, Priyabrata; Moharana, P. C.; Kumar, Mahesh; Soni, M. L.; Pandey, C. B.; Chaudhari, S. K.; Sikka, A. K.

2017-10-01

Wind erosion is a severe land degradation process in hot arid western India and affects the agricultural production system. It affects crop yield directly by damaging the crops through abrasion, burial, dust deposition etc. and indirectly by reducing soil fertility. In this study, an attempt was made to quantify the indirect impact of wind erosion process on crop production loss and associated economic loss in hot arid ecosystem of India. It has been observed that soil loss due to wind erosion varies from minimum 1.3 t ha-1 to maximum 83.3 t ha-1 as per the severity. Yield loss due to wind erosion was found maximum for groundnut (Arachis hypogea) (5-331 kg ha-1 yr-1), whereas minimum for moth bean (Vigna aconitifolia) (1-93 kg ha-1 yr-1). For pearl millet (Pennisetum glaucum), which covers a major portion of arable lands in western Rajasthan, the yield loss was found 3-195 kg ha-1 yr-1. Economic loss was found higher for groundnut and clusterbean (Cyamopsis tetragonoloba) than rest crops, which are about

Ultrastructural Study on Ultra-Low Frequency Electromagnetic Fields and Transfer Factor Effects on Skin Ulcers

DOE Office of Scientific and Technical Information (OSTI.GOV)

Cadena, M. S. Reyes; Chapul, L. Sanchez; Perez, Javier

2008-08-11

We determined the effect of 120Hz ultra low frequency electromagnetic field (ELF) on the healing process of skin in 20 Wistar rats distributed in four groups in which chronic dermal ulcers had been produced. The first two groups received a dose of the transfer factor and interferon-beta (IFN-{beta}) every 24 h during 12 days. The third group (positive control) received only electromagnetic field (ELF) sessions, and in the fourth group (negative control), no treatment was applied. The electromagnetic field was applied through a Helmholtz coils; 30 Gauss of intensity. Results shown histological changes that improve the healing process in animalsmore » subjected to ELF together with the transfer factor.« less

Ecological-site based assessments of wind and water erosion: informing management of accelerated soil erosion in rangelands

NASA Astrophysics Data System (ADS)

Webb, N.; Herrick, J.; Duniway, M.

2013-12-01

This work explores how soil erosion assessments can be structured in the context of ecological sites and site dynamics to inform systems for managing accelerated soil erosion. We evaluated wind and water erosion rates for five ecological sites in southern New Mexico, USA, using monitoring data and rangeland-specific wind and water erosion models. Our results show that wind and water erosion can be highly variable within and among ecological sites. Plots in shrub-encroached and shrub-dominated states were consistently susceptible to both wind and water erosion. However, grassland plots and plots with a grass-succulent mix had a high indicated susceptibility to wind and water erosion respectively. Vegetation thresholds for controlling erosion are identified that transcend the ecological sites and their respective states. The thresholds define vegetation cover levels at which rapid (exponential) increases in erosion rates begin to occur, suggesting that erosion in the study ecosystem can be effectively controlled when bare ground cover is <20% of a site or total ground cover is >50%. Similarly, our results show that erosion can be controlled when the cover of canopy interspaces >50 cm in length reaches ~50%, the cover of canopy interspaces >100 cm in length reaches ~35% or the cover of canopy interspaces >150 cm in length reaches ~20%. This process-based understanding can be applied, along with knowledge of the differential sensitivity of vegetation states, to improve erosion management systems. Land use and management activities that alter cover levels such that they cross thresholds, and/or drive vegetation state changes, may increase the susceptibility of sites to erosion. Land use impacts that are constrained within the natural variability of sites should not result in accelerated soil erosion. Evaluating land condition against the erosion thresholds and natural variability of ecological sites will enable improved identification of where and when accelerated soil erosion occurs and the development of practical management solutions.

Electromagnetic Wave Absorption Coating Material with Self-Healing Properties.

PubMed

Wang, Ya-Min; Pan, Min; Liang, Xiang-Yong; Li, Bang-Jing; Zhang, Sheng

2017-12-01

Electromagnetic wave absorption coatings can effectively minimize electromagnetic radiation and are widely used in the military and civil field. However, even small scratches on the coating can lead to a large decline of absorption ability and bring serious consequences. To enhance the lifetime of electromagnetic wave absorbing coating, a kind of self-healing electromagnetic wave absorbing coating is developed by introducing host-guest interactions between the absorbing fillers and polymer matrix. After being damaged, the cracks on this coating can be healed completely with the aid of small amounts of water. Simultaneously, the electromagnetic absorbing ability of the coating is restored along with the self-healing process. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Spectral perspective on the electromagnetic activity of cells.

PubMed

Kučera, Ondrej; Červinková, Kateřina; Nerudová, Michaela; Cifra, Michal

2015-01-01

In this mini-review, we summarize the current hypotheses, theories and experimental evidence concerning the electromagnetic activity of living cells. We systematically classify the bio-electromagnetic phenomena in terms of frequency and we assess their general acceptance in scientific community. We show that the electromagnetic activity of cells is well established in the low frequency range below 1 kHz and on optical wavelengths, while there is only limited evidence for bio-electromagnetic processes in radio- frequency and millimeter-wave ranges. This lack of generally accepted theory or trustful experimental results is the cause for controversy which accompanies this topic. We conclude our review with the discussion of the relevance of the electromagnetic activity of cells to human medicine.

Electromagnetic perception and individual features of human beings.

PubMed

Lebedeva, N N; Kotrovskaya, T I

2001-01-01

An investigation was made of the individual reactions of human subjects exposed to electromagnetic fields. We performed the study on 86 volunteers separated into two groups. The first group was exposed to the electromagnetic field of infralow frequencies, whereas the second group was exposed to the electromagnetic field of extremely high frequencies. We found that the electromagnetic perception of human beings correlated with their individual features, such as EEG parameters, the critical frequency of flash merging, and the electric current sensitivity. Human subjects who had a high-quality perception of electromagnetic waves showed an optimal balance of cerebral processes, an excellent functional state of the central nervous system, and a good decision criterion.

Immunohistochemical Study of p53 Expression in Patients with Erosive and Non-Erosive Oral Lichen Planus

PubMed Central

Shiva, Atena; Zamanian, Ali; Arab, Shahin; Boloki, Mahsa

2018-01-01

Statement of the Problem: Oral lichen planus is a common mucocutaneous lesion with a chronic inflammatory process mediated by immune factors while a few cases of the disease become malignant. Purpose: This study aimed to determine the frequency of p53 marker as a tumor suppressor in patients with erosive and non-erosive oral lichen planus (OLP) by using immunohistochemical methods. Materials and Method: This descriptive cross-sectional study investigated the p53 expression in 16 erosive OLP, 16 non-erosive OLP samples, and 8 samples of normal oral mucosa through immunohistochemistry. The percentage of stained cells in basal and suprabasal layers, and inflammatory infiltrate were graded according to the degree of staining; if 0%, <10%, 10-25%, and >50% of the cells were stained, they were considered as (-), (+), (++), (+++) and (++++), respectively. The obtained data was statistically analyzed and compared by using Chi square and Fisher’s exact test. Results: The mean percentage of p53 positive cells in erosive OLP (34.5±14.2) was considerably higher than that in non-erosive OLP (23.8±10.4) and normal mucosa (17.5±17). There was a significant difference among the three groups of erosive, non-erosive and control in terms of staining intensity. No significant difference existed between the patients’ age and sex in the two OLP groups. Conclusion: The increased incidence of p53 from normal mucosa to erosive OLP indicated the difference between biological behavior of erosive and non-erosive OLP. It can be claimed that the erosive OLP has great premalignant potential compared with the non-erosive one.

Research on radiation characteristic of plasma antenna through FDTD method.

PubMed

Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

2014-01-01

The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic.

How to explain variations in sea cliff erosion rate?

NASA Astrophysics Data System (ADS)

Prémaillon, Melody; Regard, Vincent; Dewez, Thomas

2017-04-01

Every rocky coast of the world is eroding at different rate (cliff retreat rates). Erosion is caused by a complex interaction of multiple sea weather factors. While numerous local studies exist and explain erosion processes on specific sites, global studies lack. We started to compile many of those local studies and analyse their results with a global point of view in order to quantify the various parameters influencing erosion rates. In other words: is erosion more important in energetic seas? Are chalk cliff eroding faster in rainy environment? etc. In order to do this, we built a database based on literature and national erosion databases. It now contains 80 publications which represents 2500 cliffs studied and more than 3500 erosion rate estimates. A statistical analysis was conducted on this database. On a first approximation, cliff lithology is the only clear signal explaining erosion rate variation: hard lithologies are eroding at 1cm/y or less, whereas unconsolidated lithologies commonly erode faster than 10cm/y. No clear statistical relation were found between erosion rate and external parameters such as sea energy (swell, tide) or weather condition, even on cliff with similar lithology.

Land cover change detection of Hatiya Island, Bangladesh, using remote sensing techniques

NASA Astrophysics Data System (ADS)

Kumar, Lalit; Ghosh, Manoj Kumer

2012-01-01

Land cover change is a significant issue for environmental managers for sustainable management. Remote sensing techniques have been shown to have a high probability of recognizing land cover patterns and change detection due to periodic coverage, data integrity, and provision of data in a broad range of the electromagnetic spectrum. We evaluate the applicability of remote sensing techniques for land cover pattern recognition, as well as land cover change detection of the Hatiya Island, Bangladesh, and quantify land cover changes from 1977 to 1999. A supervised classification approach was used to classify Landsat Enhanced Thematic Mapper (ETM), Thematic Mapper (TM), and Multispectral Scanner (MSS) images into eight major land cover categories. We detected major land cover changes over the 22-year study period. During this period, marshy land, mud, mud with small grass, and bare soil had decreased by 85%, 46%, 44%, and 24%, respectively, while agricultural land, medium forest, forest, and settlement had positive changes of 26%, 45%, 363%, and 59%, respectively. The primary drivers of such landscape change were erosion and accretion processes, human pressure, and the reforestation and land reclamation programs of the Bangladesh Government.

Repeated erosion of cohesive sediments with biofilms

NASA Astrophysics Data System (ADS)

Valentine, K.; Mariotti, G.; Fagherazzi, S.

2014-04-01

This study aims to explore the interplay between biofilms and erodability of cohesive sediments. Erosion experiments were run in four laboratory annular flumes with natural sediments. After each erosion the sediment was allowed to settle, mimicking intermittent physical processes like tidal currents and waves. The time between consecutive erosion events ranged from 1 to 12 days. Turbidity of the water column caused by sediment resuspension was used to determine the erodability of the sediments with respect to small and moderate shear stresses. Erodability was also compared on the basis of the presence of benthic biofilms, which were quantified using a Pulse-Amplitude Modulation (PAM) Underwater Fluorometer. We found that frequent erosion lead to the establishment of a weak biofilm, which reduced sediment erosion at small shear stresses (around 0.1 Pa). If prolonged periods without erosion were present, the biofilm fully established, resulting in lower erosion at moderate shear stresses (around 0.4 Pa). We conclude that an unstructured extracellular polymeric substances (EPS) matrix always affect sediment erodability at low shear stresses, while only a fully developed biofilm mat can reduce sediment erodability at moderate shear stresses.

Solid Particle Erosion Behaviors of Carbon-Fiber Epoxy Composite and Pure Titanium

NASA Astrophysics Data System (ADS)

Cai, Feng; Gao, Feng; Pant, Shashank; Huang, Xiao; Yang, Qi

2016-01-01

Rotor blades of Bell CH-146 Griffon helicopter experience excessive solid particle erosion at low altitudes in desert environment. The rotor blade is made of an advanced light-weight composite which, however, has a low resistance to solid particle erosion. Coatings have been developed and applied to protect the composite blade. However, due to the influence of coating process on composite material, the compatibility between coating and composite base, and the challenges of repairing damaged coatings as well as the inconsistency between the old and new coatings, replaceable thin metal shielding is an alternative approach; and titanium, due to its high-specific strength and better formability, is an ideal candidate. This work investigates solid particle erosion behaviors of carbon-fiber epoxy composite and titanium in order to assess the feasibility of titanium as a viable candidate for erosion shielding. Experiment results showed that carbon-fiber epoxy composite showed a brittle erosion behavior, whereas titanium showed a ductile erosion mode. The erosion rate on composite was 1.5 times of that on titanium at impingement angle 15° and increased to 5 times at impact angle 90°.

Real-Time Measurements of Aft Dome Insulation Erosion on Space Shuttle Reusable Solid Rocket Motor

NASA Technical Reports Server (NTRS)

McWhorter, Bruce; Ewing, Mark; Albrechtsen, Kevin; Noble, Todd; Longaker, Matt

2004-01-01

Real-time erosion of aft dome internal insulation was measured with internal instrumentation on a static test of a lengthened version of the Space Shuffle Reusable Solid Rocket Motor (RSRM). This effort marks the first time that real-time aft dome insulation erosion (Le., erosion due to the combined effects of thermochemical ablation and mechanical abrasion) was measured in this kind of large motor static test [designated as Engineering Test Motor number 3 (ETM3)I. This paper presents data plots of the erosion depth versus time. The data indicates general erosion versus time behavior that is in contrast to what would be expected from earlier analyses. Engineers have long known that the thermal environment in the aft dome is severe and that the resulting aft dome insulation erosion is significant. Models of aft dome erosion involve a two-step process of computational fluid dynamics (CFD) modeling and material ablation modeling. This modeling effort is complex. The time- dependent effects are difficult to verify with only prefire and postfire insulation measurements. Nozzle vectoring, slag accumulation, and changing boundary conditions will affect the time dependence of aft dome erosion. Further study of this data and continued measurements on future motors will increase our understanding of the aft dome flow and erosion environment.

Robotic weld overlay coatings for erosion control

NASA Astrophysics Data System (ADS)

The erosion of materials by the impact of solid particles has received increasing attention during the past twenty years. Recently, research has been initiated with the event of advanced coal conversion processes in which erosion plays an important role. The resulting damage, termed Solid Particle Erosion (SPE), is of concern primarily because of the significantly increased operating costs which result in material failures. Reduced power plant efficiency due to solid particle erosion of boiler tubes and waterfalls has led to various methods to combat SPE. One method is to apply coatings to the components subjected to erosive environments. Protective weld overlay coatings are particularly advantageous in terms of coating quality. The weld overlay coatings are essentially immune to spallation due to a strong metallurgical bond with the substrate material. By using powder mixtures, multiple alloys can be mixed in order to achieve the best performance in an erosive environment. However, a review of the literature revealed a lack of information on weld overlay coating performance in erosive environments which makes the selection of weld overlay alloys a difficult task. The objective of this project is to determine the effects of weld overlay coating composition and microstructure on erosion resistance. These results will lead to a better understanding of erosion mitigation in CFB's.

Global rainfall erosivity assessment based on high-temporal resolution rainfall records.

PubMed

Panagos, Panos; Borrelli, Pasquale; Meusburger, Katrin; Yu, Bofu; Klik, Andreas; Jae Lim, Kyoung; Yang, Jae E; Ni, Jinren; Miao, Chiyuan; Chattopadhyay, Nabansu; Sadeghi, Seyed Hamidreza; Hazbavi, Zeinab; Zabihi, Mohsen; Larionov, Gennady A; Krasnov, Sergey F; Gorobets, Andrey V; Levi, Yoav; Erpul, Gunay; Birkel, Christian; Hoyos, Natalia; Naipal, Victoria; Oliveira, Paulo Tarso S; Bonilla, Carlos A; Meddi, Mohamed; Nel, Werner; Al Dashti, Hassan; Boni, Martino; Diodato, Nazzareno; Van Oost, Kristof; Nearing, Mark; Ballabio, Cristiano

2017-06-23

The exposure of the Earth's surface to the energetic input of rainfall is one of the key factors controlling water erosion. While water erosion is identified as the most serious cause of soil degradation globally, global patterns of rainfall erosivity remain poorly quantified and estimates have large uncertainties. This hampers the implementation of effective soil degradation mitigation and restoration strategies. Quantifying rainfall erosivity is challenging as it requires high temporal resolution(<30 min) and high fidelity rainfall recordings. We present the results of an extensive global data collection effort whereby we estimated rainfall erosivity for 3,625 stations covering 63 countries. This first ever Global Rainfall Erosivity Database was used to develop a global erosivity map at 30 arc-seconds(~1 km) based on a Gaussian Process Regression(GPR). Globally, the mean rainfall erosivity was estimated to be 2,190 MJ mm ha -1 h -1 yr -1 , with the highest values in South America and the Caribbean countries, Central east Africa and South east Asia. The lowest values are mainly found in Canada, the Russian Federation, Northern Europe, Northern Africa and the Middle East. The tropical climate zone has the highest mean rainfall erosivity followed by the temperate whereas the lowest mean was estimated in the cold climate zone.

Fractional models of seismoacoustic and electromagnetic activity

NASA Astrophysics Data System (ADS)

Shevtsov, Boris; Sheremetyeva, Olga

2017-10-01

Statistical models of the seismoacoustic and electromagnetic activity caused by deformation disturbances are considered on the basis of compound Poisson process and its fractional generalizations. Wave representations of these processes are used too. It is discussed five regimes of deformation activity and their role in understanding of the earthquakes precursors nature.

The erosion behaviour of biologically active sewer sediment deposits: observations from a laboratory study.

PubMed

Banasiak, Robert; Verhoeven, Ronny; De Sutter, Renaat; Tait, Simon

2005-12-01

The erosion behaviour of various fine-grained sediment deposits has been investigated in laboratory experiments. This work mainly focused on tests using sewer sediment in which strong biochemical reactions were observed during the deposit formation period. A small number of initial tests were conducted in which the deposits were made from mixtures of "clean" mineral and organic sediments. The erosion behaviour observed in these tests was compared with the erosion characteristics for sediments taken from deposits in a sewer. The impact of the biological processes on physical properties such as bulk density, water content, deposit structure and the erosive behaviour as a function of bed shear stress are quantified and discussed. Based on these observations it is believed that bio-processes weaken the strength of the in-pipe sediment deposits. A significantly weaker sediment surface layer was observed during deposition under quiescent oxygen-rich conditions. This resulted in a deposit with low shear strength which may be a cause of a first foul flush of suspended sediment when flow rates were increased. Comparison between tests with sewer sediments and the artificial representative surrogates suggested that the deposits of the later did not correctly simulate the depositional development and the resultant erosion patterns observed with the more bio-active sewer sediment.

Plasmaspheric Erosion via Plasmasphere Coupling to Ring Current Plasmas: EUV Observations and Modeling

NASA Technical Reports Server (NTRS)

Adrian, M. L.; Gallagher, D. L.; Khazanov, G. V.; Chsang, S. W.; Liemohn, M. W.; Perez, J. D.; Green, J. L.; Sandel, B. R.; Mitchell, D. G.; Mende, S. B.;

Materials for Advanced Turbine Engines (MATE). Project 4: Erosion resistant compressor airfoil coating

NASA Technical Reports Server (NTRS)

Rashid, J. M.; Freling, M.; Friedrich, L. A.

1987-01-01

The ability of coatings to provide at least a 2X improvement in particulate erosion resistance for steel, nickel and titanium compressor airfoils was identified and demonstrated. Coating materials evaluated included plasma sprayed cobalt tungsten carbide, nickel carbide and diffusion applied chromium plus boron. Several processing parameters for plasma spray processing and diffusion coating were evaluated to identify coating systems having the most potential for providing airfoil erosion resistance. Based on laboratory results and analytical evaluations, selected coating systems were applied to gas turbine blades and evaluated for surface finish, burner rig erosion resistance and effect on high cycle fatigue strength. Based on these tests, the following coatings were recommended for engine testing: Gator-Gard plasma spray 88WC-12Co on titanium alloy airfoils, plasma spray 83WC-17Co on steel and nickel alloy airfoils, and Cr+B on nickel alloy airfoils.

The Integrated Soil Erosion Risk Management Model of Central Java, Indonesia

NASA Astrophysics Data System (ADS)

Setiawan, M. A.; Stoetter, J.; Sartohadi, J.; Christanto, N.

2009-04-01

Many types of soil erosion modeling have been developed worldwide; each of models has its own advantage and assumption based on the originated area. Ironically, in the tropical countries where the rainfall intensity is higher than other area, the soil erosion problem gain less attention. As in Indonesia, due the inadequate supporting data and method to dealing with, the soil erosion management appears to be least prior in the policy decision. Hence, there is increasing necessity towards the initiation and integration of risk management model in the soil erosion, to prevent further land degradation problem in Indonesia. The main research objective is to generate a model which can analyze the dynamic system of soil erosion problem. This model will comprehensively consider four main aspects within the dynamic system analysis, i.e.: soil erosion rate modeling, the tolerable soil erosion rate, total soil erosion cost, and soil erosion management measures. The generating model will involve some sub-software i.e. the PC Raster to maintain the soil erosion modeling, Powersim Constructor Ver. 2.5 as the tool to analyze the dynamic system and Python Ver. 2.6.1 to build the main Graphical User Interface model. The first step addressed in this research is figuring the most appropriate soil erosion model to be applied in Indonesia based on landscape, climate, and data availability condition. This appropriate model must have the simplicity aspect in input data but still deal with the process based analysis. By using the soil erosion model result, the total soil erosion cost will be calculated both on-site and off-site effect. The total soil erosion cost will be stated in Rupiah (Indonesian currency) and Dollar. That total result is then used as one of input parameters for the tolerable soil erosion rate. Subsequently, the tolerable soil erosion rate decides whether the soil erosion rate has exceeded the allowed value or not. If the soil erosion rate has bigger value than the tolerable soil erosion rate, the soil erosion management will be applied base on cost and benefit analysis. The soil erosion management measures will conduct as decision maker of defining the best alternative soil conservation method in a certain area. Besides the engineering and theoretical methods, the local wisdom also will be taken into account in defining the alternative manners of soil erosion management. As a prototype, this integrated model will be generated and simulated in Serayu Watershed, Central Java, since this area has a serious issue in soil erosion problem mainly in the upper stream area (Dieng area). The extraordinary monoculture plantation (potatoes) and very intensive soil tillage without proper soil conservation method has accelerated the soil erosion and depleted the soil fertility. Based on the potatoes productivity data (kg/ha) from 1997-2007 showed that there was a declining trend line, approximately minus 8,2% every year. On the other hand the fertilizer and pesticide consumption in agricultural land are significantly increasing every year. In the same time, the high erosion rate causes serious sedimentation problem in lower stream. Those conditions can be used as study case in determining the element at risk of soil erosion and calculation method for the total soil erosion cost (on-site and off-site effect). Moreover, The Serayu Watershed consists of complex landforms which might have variation of soil erosion tolerable rate. In the future, this integrated model can obtain valuable basis data of the soil erosion hazard in spatial and temporal information including its total cost, the sustainability time of certain land or agriculture area, also the consequences price of applying certain agriculture or soil management. Since this model give result explicitly in spatial and temporal, this model can be used by the local authority to run the land use scenario in term of soil erosion impact before applied them in the real condition. In practice, such integrated model could give more understanding knowledge to the local people about the soil erosion, its processes, impacts, and how to manage that. Keywords: Risk assessment, soil erosion, dynamic system, environmental valuation

Propagation of electromagnetic wave in dusty plasma and the influence of dust size distribution

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Hui; China Research Institute of Radio Wave Propagation; Wu, Jian

The effect of charged dust particle and their size distribution on the propagation of electromagnetic wave in a dusty plasma is investigated. It is shown that the additional collision mechanism provided by charged dust particles can significantly alter the electromagnetic properties of a plasma, leading to the appearance of attenuation of electromagnetic wave through dusty plasma. The attenuation coefficient mainly depends on the dust density, radius, and the charge numbers on the dust surface. The results described here will be used to enhance understanding of electromagnetic wave propagation processed in space and laboratory dusty plasma.

Design and Performance Optimizations of Advanced Erosion-Resistant Low Conductivity Thermal Barrier Coatings for Rotorcraft Engines

NASA Technical Reports Server (NTRS)

Zhu, Dongming; Miller, Robert A.; Kuczmarski, Maria A.

2012-01-01

Thermal barrier coatings will be more aggressively designed to protect gas turbine engine hot-section components in order to meet future rotorcraft engine higher fuel efficiency and lower emission goals. For thermal barrier coatings designed for rotorcraft turbine airfoil applications, further improved erosion and impact resistance are crucial for engine performance and durability, because the rotorcraft are often operated in the most severe sand erosive environments. Advanced low thermal conductivity and erosion-resistant thermal barrier coatings are being developed, with the current emphasis being placed on thermal barrier coating toughness improvements using multicomponent alloying and processing optimization approaches. The performance of the advanced thermal barrier coatings has been evaluated in a high temperature erosion burner rig and a laser heat-flux rig to simulate engine erosion and thermal gradient environments. The results have shown that the coating composition and architecture optimizations can effectively improve the erosion and impact resistance of the coating systems, while maintaining low thermal conductivity and cyclic oxidation durability

Contributions to a thermodynamic model of Earth systems on rivers

NASA Technical Reports Server (NTRS)

Iberall, A. S.

1981-01-01

A model for the chemical (ground water) erosion and physical (bed load, including sedimentation) erosion of the land was developed. The rudiments of the relation between a regulated sea level (for the past 2500 million years) and the episodic rise and erosion of continents was examined to obtain some notion of the process scalings. Major process scales of about 200 years, 100,000 years, 3 My, 40 My, 300 My were estimated. It was suggested that a program targeted at ecological management would have to become familiar with processes at the first four scales (i.e., from glaciation to the horizontal movement of continents). The study returns to the initial premise. In order to understand and manage Earth biology (life, and modern man), it is necessary minimally to pursue systems' biogeology at a considerable number of process space and time scales via their irreversible thermodynamic couplings.

Coupling surface and mantle dynamics: A novel experimental approach

NASA Astrophysics Data System (ADS)

Kiraly, Agnes; Faccenna, Claudio; Funiciello, Francesca; Sembroni, Andrea

2015-05-01

Recent modeling shows that surface processes, such as erosion and deposition, may drive the deformation of the Earth's surface, interfering with deeper crustal and mantle signals. To investigate the coupling between the surface and deep process, we designed a three-dimensional laboratory apparatus, to analyze the role of erosion and sedimentation, triggered by deep mantle instability. The setup is constituted and scaled down to natural gravity field using a thin viscous sheet model, with mantle and lithosphere simulated by Newtonian viscous glucose syrup and silicon putty, respectively. The surface process is simulated assuming a simple erosion law producing the downhill flow of a thin viscous material away from high topography. The deep mantle upwelling is triggered by the rise of a buoyant sphere. The results of these models along with the parametric analysis show how surface processes influence uplift velocity and topography signals.

How quickly do earthquakes get locked in the landscape? One year of erosion on El Mayor-Cucapah rupture scarps imaged by repeat terrestrial lidar scans

NASA Astrophysics Data System (ADS)

Elliott, A. J.; Oskin, M. E.; Banesh, D.; Gold, P. O.; Hinojosa-Corona, A.; Styron, R. H.; Taylor, M. H.

2012-12-01

Differencing repeat terrestrial lidar scans of the 2010 M7.2 El Mayor-Cucapah (EMC) earthquake rupture reveals the rapid onset of surface processes that simultaneously degrade and preserve evidence of coseismic fault rupture in the landscape and paleoseismic record. We surveyed fresh fault rupture two weeks after the 4 April 2010 earthquake, then repeated these surveys one year later. We imaged fault rupture through four substrates varying in degree of consolidation and scarp facing-direction, recording modification due to a range of aeolian, fluvial, and hillslope processes. Using lidar-derived DEM rasters to calculate the topographic differences between years results in aliasing errors because GPS uncertainty between years (~1.5cm) exceeds lidar point-spacing (<1.0cm) shifting the raster sampling of the point cloud. Instead, we coregister each year's scans by iteratively minimizing the horizontal and vertical misfit between neighborhoods of points in each raw point cloud. With the misfit between datasets minimized, we compute the vertical difference between points in each scan within a specified neighborhood. Differencing results reveal two variables controlling the type and extent of erosion: cohesion of the substrate controls the degree to which hillslope processes affect the scarp, while scarp facing direction controls whether more effective fluvial erosion can act on the scarp. In poorly consolidated materials, large portions (>50% along strike distance) of the scarp crest are eroded up to 5cm by a combination of aeolian abrasion and diffusive hillslope processes, such as rainsplash and mass-wasting, while in firmer substrate (i.e., bedrock mantled by fault gouge) there is no detectable hillslope erosion. On the other hand, where small gullies cross downhill-facing scarps (<5% along strike distance), fluvial erosion has caused 5-50cm of headward scarp retreat in bedrock. Thus, although aeolian and hillslope processes operate over a greater along-strike distance, fluvial processes concentrated in pre-existing bedrock gullies transport a far greater volume of material across the scarp. Substrate cohesiveness dictates the degree to which erosive processes act to relax the scarp (e.g., gravels erode more easily than bedrock). However, scarp locations that favor fluvial processes suffer rapid, localized erosion of vertical scarp faces, regardless of substrate. Differential lidar also reveals debris cones formed at the base of the scarp below locations of scarp crest erosion. These indicate the rapid growth of a colluvial wedge. Where a fissure occupies the base of the scarp we observe nearly complete in-filling by silt and sand moved by both mass wasting and fluvial deposition, indicating that fissure fills observed in paleoseismic trenches likely bracket the age of an earthquake to within one year. We find no evidence of differential postseismic tectonic deformation across the fault within the ~100m aperture of our surveys.

MAVEN Observations of Escaping Planetary Ions from the Martian Atmosphere: Mass, Velocity, and Spatial Distributions

NASA Astrophysics Data System (ADS)

Dong, Yaxue; Fang, Xiaohua; Brain, D. A.; McFadden, James P.; Halekas, Jasper; Connerney, Jack

2015-04-01

The Mars-solar wind interaction accelerates and transports planetary ions away from the Martian atmosphere through a number of processes, including ‘pick-up’ by electromagnetic fields. The MAVEN spacecraft has made routine observations of escaping planetary ions since its arrival at Mars in September 2014. The SupraThermal And Thermal Ion Composition (STATIC) instrument measures the ion energy, mass, and angular spectra. It has detected energetic planetary ions during most of the spacecraft orbits, which are attributed to the pick-up process. We found significant variations in the escaping ion mass and velocity distributions from the STATIC data, which can be explained by factors such as varying solar wind conditions, contributions of particles from different source locations and different phases during the pick-up process. We also study the spatial distributions of different planetary ion species, which can provide insight into the physics of ion escaping process and enhance our understanding of atmospheric erosion by the solar wind. Our results will be further interpreted within the context of the upstream solar wind conditions measured by the MAVEN Solar Wind Ion Analyzer (SWIA) instrument and the magnetic field environment measured by the Magnetometer (MAG) instrument. Our study shows that the ion spatial distribution in the Mars-Sun-Electric-Field (MSE) coordinate system and the velocity space distribution with respect to the local magnetic field line can be used to distinguish the ions escaping through the polar plume and those through the tail region. The contribution of the polar plume ion escape to the total escape rate will also be discussed.

Bank erosion along the dam-regulated lower Roanoke River, North Carolina

USGS Publications Warehouse

Hupp, C.R.; Schenk, E.R.; Richter, J.M.; Peet, Robert K.; Townsend, Phil A.

2009-01-01

Dam construction and its impact on downstream fluvial processes may substantially alter ambient bank stability and erosion. Three high dams (completed between 1953 and 1963) were built along the Piedmont portion of the Roanoke River, North Carolina; just downstream the lower part of the river flows across largely unconsolidated Coastal Plain deposits. To document bank erosion rates along the lower Roanoke River, >700 bank-erosion pins were installed along 66 bank transects. Additionally, discrete measurements of channel bathymetry, turbidity, and presence or absence of mass wasting were documented along the entire study reach (153 km). A bank-erosion- floodplain-deposition sediment budget was estimated for the lower river. Bank toe erosion related to consistently high low-flow stages may play a large role in increased mid- and upper-bank erosion. Present bank-erosion rates are relatively high and are greatest along the middle reaches (mean 63 mm/yr) and on lower parts of the bank on all reaches. Erosion rates were likely higher along upstream reaches than present erosion rates, such that erosion-rate maxima have since migrated downstream. Mass wasting and turbidity also peak along the middle reaches; floodplain sedimentation systematically increases downstream in the study reach. The lower Roanoke River isnet depositional (on floodplain) with a surplus of ??2,800,000 m3yr. Results suggest that unmeasured erosion, particularly mass wasting, may partly explain this surplus and should be part of sediment budgets downstream of dams. ?? 2009 The Geological Society of America.

Soil erosion by snow gliding - a first quantification attempt in a subalpine area in Switzerland

NASA Astrophysics Data System (ADS)

Meusburger, K.; Leitinger, G.; Mabit, L.; Mueller, M. H.; Walter, A.; Alewell, C.

2014-09-01

Snow processes might be one important driver of soil erosion in Alpine grasslands and thus the unknown variable when erosion modelling is attempted. The aim of this study is to assess the importance of snow gliding as a soil erosion agent for four different land use/land cover types in a subalpine area in Switzerland. We used three different approaches to estimate soil erosion rates: sediment yield measurements in snow glide depositions, the fallout radionuclide 137Cs and modelling with the Revised Universal Soil Loss Equation (RUSLE). RUSLE permits the evaluation of soil loss by water erosion, the 137Cs method integrates soil loss due to all erosion agents involved, and the measurement of snow glide deposition sediment yield can be directly related to snow-glide-induced erosion. Further, cumulative snow glide distance was measured for the sites in the winter of 2009/2010 and modelled for the surrounding area and long-term average winter precipitation (1959-2010) with the spatial snow glide model (SSGM). Measured snow glide distance confirmed the presence of snow gliding and ranged from 2 to 189 cm, with lower values on the north-facing slopes. We observed a reduction of snow glide distance with increasing surface roughness of the vegetation, which is an important information with respect to conservation planning and expected and ongoing land use changes in the Alps. Snow glide erosion estimated from the snow glide depositions was highly variable with values ranging from 0.03 to 22.9 t ha-1 yr-1 in the winter of 2012/2013. For sites affected by snow glide deposition, a mean erosion rate of 8.4 t ha-1 yr-1 was found. The difference in long-term erosion rates determined with RUSLE and 137Cs confirms the constant influence of snow-glide-induced erosion, since a large difference (lower proportion of water erosion compared to total net erosion) was observed for sites with high snow glide rates and vice versa. Moreover, the difference between RUSLE and 137Cs erosion rates was related to the measured snow glide distance (R2 = 0.64; p < 0.005) and to the snow deposition sediment yields (R2 = 0.39; p = 0.13). The SSGM reproduced the relative difference of the measured snow glide values under different land uses and land cover types. The resulting map highlighted the relevance of snow gliding for large parts of the investigated area. Based on these results, we conclude that snow gliding appears to be a crucial and non-negligible process impacting soil erosion patterns and magnitude in subalpine areas with similar topographic and climatic conditions.

Quantized Electromagnetic-Field Propagation in General Non-Local and Non-Stationary Dispersive and Absorbing Media

NASA Astrophysics Data System (ADS)

Jacobs, Verne

Dynamical descriptions for the propagation of quantized electromagnetic fields, in the presence of environmental interactions, are systematically and self-consistently developed in the complimentary Schrödinger and Heisenberg pictures. An open-systems (non-equilibrium) quantum-electrodynamics description is thereby provided for electromagnetic-field propagation in general non-local and non-stationary dispersive and absorbing optical media, including a fundamental microscopic treatment of decoherence and relaxation processes due to environmental collisional and electromagnetic interactions. Particular interest is centered on entangled states and other non-classical states of electromagnetic fields, which may be created by non-linear electromagnetic interactions and detected by the measurement of various electromagnetic-field correlation functions. Accordingly, we present dynamical descriptions based on general forms of electromagnetic-field correlation functions involving both the electric-field and the magnetic-field components of the electromagnetic field, which are treated on an equal footing. Work supported by the Office of Naval Research through the Basic Research Program at The Naval Research Laboratory.

Deglaciation and glacial erosion: a joint control on magma productivity by continental unloading

NASA Astrophysics Data System (ADS)

Sternai, Pietro; Caricchi, Luca; Castelltort, Sebastien

2016-04-01

Glacial-interglacial cycles affect the processes through which water and rocks are redistributed across the Earth's surface, thereby linking solid-Earth and climate dynamics. Regional and global scale studies suggest that continental lithospheric unloading due to ice melting during the transition to interglacials leads to increased continental magmatic, volcanic and degassing activity. Such a climatic forcing on the melting of the Earth's interior, however, has always been evaluated without considering the additional continental unloading associated with erosion. Current datasets relating to the evolution of erosion rates are typically limited by temporal resolutions that are too low or span too short time intervals to allow for direct comparisons between the contributions from ice melting and erosion to continental unloading at the timescale of the late Pleistocene glacial cycles. Yet, they provide a fundamental observational basis on which to calibrate numerical predictions. Here, we present and discuss numerical results involving synthetic but realistic topographies, ice caps and glacial erosion rates suggesting that erosion may be as important as deglaciation in affecting continental unloading, sub-continental decompression melting and magma productivity. Thus, the timing and magnitude of deglaciation and erosion must be characterized if the forcing of climate change on the continental magmatic/volcanic activity is to be extracted from the remnants of eroded volcanic centers. Our study represents an additional step towards a more general understanding of the links between a changing climate, glacial processes and the melting of the solid Earth.

Coastal retreat and shoreface profile variations in the Canadian Beaufort Sea

USGS Publications Warehouse

Hequette, A.; Barnes, P.W.

1990-01-01

The coastline of the southern Canadian Beaufort Sea consists primarily of unconsolidated bluffs. Although the sea is ice-free for 3 months of the year and wave energy is restricted by pack ice, the coast is undergoing regional retreat with erosion rates as high as 10 m a-1 in some locations. Simple and multiple regression analyses were carried out to determine the degree of correlation between the mean retreat rate measured at various locations and the different parameters that may control shoreline recession. Sediment texture, ground-ice content, cliff height, wave energy and shoreface gradient revealed medium to poor correlation with erosion rates, showing that the recessive evolution of the coastline can not be explained solely by wave-induced and subaerial processes. The comparison of nearshore echo-sounding records from 1987 with bathymetry from 1971 showed substantial erosion (up to 1 m) of the submarine profile between 12 and 15 m of water. There is strong evidence that this erosion has been caused by sea ice gouging on the seafloor. From depths of 5 to 9 m, accretion has taken place, possibly induced by ice-push processes, and inshore of the 5 m isobath wave and current erosion of the shoreface has occurred. These results suggest that the erosion of the inner shelf by ice gouging drives the erosion observed inshore on the coastal bluffs and nearshore zone as the shoreface profile strives for a state of dynamic equilibrium. ?? 1990.

Opportunities provided by UAVs to monitor erosion processes in agricultural catchments: a case study from Northern France

NASA Astrophysics Data System (ADS)

Frankl, Amaury; Stal, Cornelis; De Wit, Bart; De Wulf, Alain; Salvador, Pierre-Gil; Nyssen, Jan

2014-05-01

In erosion studies, accurate spatio-temporal data are required to fully understand the processes involved and their relationship with environmental controls. With cameras being mounted on Unmanned Aerial Vehicles (UAVs), the latter allow to collect low-altitude aerial photographs over small catchments in a cost-effective and rapid way. From large data sets of overlapping aerial photographs, Structure from Motion - Multi View Stereo workflows, integrated in various software such as PhotoScan used here, allow to produced detailed Digital Surface Models (DSMs) and ortho-mosaics. In this study we present the results from a survey carried out in a small agricultural catchment near Hallines, in Northern France. A DSM and ortho-mosaic was produced of the catchment using photographs taken from a low-cost radio-controlled microdrone (DroneFlyer Hexacopter). Photographs were taken with a Sony Nex 5 (16.1 M pixels) camera having a fixed normal lens of 50 mm. In the field, Ground Control Points were materialized by unambiguously determinable targets, measured with a 1'' total station (Leica TS15i). Cross-sections of rills and ephemeral gullies were also quantified from total station measurements and from terrestrial image-based 3D modelling. These data allowed to define the accuracy of the DSM and the representation of the erosion features in it. The feasibility of UAVs photographic surveys to improve our understanding on water-erosion processes such as sheet, rill and gully erosion is discussed. Keywords: Ephemeral gully, Erosion study, Image-based 3D modelling, Microdrone, Rill, UAVs.

Visualization and mechanisms of splashing erosion of electrodes in a DC air arc

NASA Astrophysics Data System (ADS)

Wu, Yi; Cui, Yufei; Rong, Mingzhe; Murphy, Anthony B.; Yang, Fei; Sun, Hao; Niu, Chunping; Fan, Shaodi

2017-11-01

The splashing erosion of electrodes in a DC atmospheric-pressure air arc has been investigated by visualization of the electrode surface and the sputtered droplets, and tracking of the droplet trajectories, using image processing techniques. A particle tracking velocimetry algorithm has been introduced to measure the sputtering velocity distribution. Erosion of both tungsten-copper and tungsten-ceria electrodes is studied; in both cases electrode erosion is found to be dominated by droplet splashing rather than metal evaporation. Erosion is directly influenced by both melting and the formation of plasma jets, and can be reduced by the tuning of the plasma jet and electrode material. The results provide an understanding of the mechanisms that lead to the long lifetime of tungsten-copper electrodes, and may provide a path for the design of the electrode system subjected to electric arc to minimize erosion.

Detection of seasonal cycles of erosion processes in a black marl gully from a time series of high-resolution digital elevation models (DEMs)

NASA Astrophysics Data System (ADS)

Bechet, Jacques; Duc, Julien; Loye, Alexandre; Jaboyedoff, Michel; Mathys, Nicolle; Malet, Jean-Philippe; Klotz, Sébastien; Le Bouteiller, Caroline; Rudaz, Benjamin; Travelletti, Julien

2016-10-01

The Roubine catchment located in the experimental research station of Draix-Bléone (south French Alps) is situated in Callovo-Oxfordian black marls, a lithology particularly prone to erosion and weathering processes. For 30 years, this small watershed (0.13 ha) has been monitored for analysing hillslope processes on the scale of elementary gullies. Since 2007, surface changes have been monitored by comparing high-resolution digital elevation models (HRDEMs) produced from terrestrial laser scanner (TLS). The objectives are (1) to detect and (2) to quantify the sediment production and the evolution of the gully morphology in terms of sediment availability/transport capacity vs. rainfall and runoff generation. Time series of TLS observations have been acquired periodically based on the seasonal runoff activity with a very high point cloud density ensuring a resolution of the digital elevation model (DEM) on the centimetre scale. The topographic changes over a time span of 2 years are analysed. Quantitative analyses of the seasonal erosion activity and of the sediment fluxes show and confirm that during winter, loose regolith is created by mechanical weathering, and it is eroded and accumulates in the rills and gullies. Because of limited rainfall intensity in spring, part of the material is transported in the main gullies, which are assumed to be a transport-limited erosion system. In the late spring and summer the rainfall intensities increase, allowing the regolith, weathered and accumulated in the gullies and rills during the earlier seasons, to be washed out. Later in the year the catchment acts as a sediment-limited system because no more loose regolith is available. One interesting result is the fact that in the gullies the erosion-deposition processes are more active around the slope angle value of 35°, which probably indicates a behaviour close to dry granular material. It is also observed that there exist thresholds for the rainfall events that are able to trigger significant erosion; they are above 9 mm rainfall or of an intensity of more than 1 mm min-1, values which can vary if antecedent precipitation is significant within the last 5 days.

This study improves knowledge of the spatial distribution of erosion seasonality in badlands and demonstrates the potential of careful 3-D high-resolution topography using TLS to improve the understanding of erosive processes.

Erosion and lateral surface processes

USDA-ARS?s Scientific Manuscript database

: Erosion can cause serious agricultural and environmental hazards. It can generate severe damage to the landscape, lead to significant loss of agricultural land and consequently to reduction in agricultural productivity, induce surface water pollution due to the transport of sediments and suspende...

Comparing and combining terrestrial laser scanning with ground-and UAV-based imaging for national-level assessment of soil erosion

NASA Astrophysics Data System (ADS)

McShane, Gareth; James, Mike R.; Quinton, John; Anderson, Karen; DeBell, Leon; Evans, Martin; Farrow, Luke; Glendell, Miriam; Jones, Lee; Kirkham, Matthew; Lark, Murray; Rawlins, Barry; Rickson, Jane; Quine, Tim; Wetherelt, Andy; Brazier, Richard

2014-05-01

3D topographic or surface models are increasingly being utilised for a wide range of applications and are established tools in geomorphological research. In this pilot study 'a cost effective framework for monitoring soil erosion in England and Wales', funded by the UK Department for Environment, Food and Rural Affairs (Defra), we compare methods of collecting topographic measurements via remote sensing for detailed studies of dynamic processes such as erosion and mass movement. The techniques assessed are terrestrial laser scanning (TLS), and unmanned aerial vehicle (UAV) photography and ground-based photography, processed using structure-from-motion (SfM) 3D reconstruction software. The methods will be applied in regions of different land use, including arable and horticultural, upland and semi natural habitats, and grassland, to quantify visible erosion pathways at the site scale. Volumetric estimates of soil loss will be quantified using the digital surface models (DSMs) provided by each technique and a modelled pre-erosion surface. Visible erosion and severity will be independently established through each technique, with their results compared and combined effectiveness assessed. A fixed delta-wing UAV (QuestUAV, http://www.questuav.com/) captures photos from a range of altitudes and angles over the study area, with automated SfM-based processing enabling rapid orthophoto production to support ground-based data acquisition. At sites with suitable scale erosion features, UAV data will also provide a DSM for volume loss measurement. Terrestrial laser scanning will provide detailed, accurate, high density measurements of the ground surface over long (100s m) distances. Ground-based photography is anticipated to be most useful for characterising small and difficult to view features. By using a consumer-grade digital camera and an SfM-based approach (using Agisoft Photoscan version 1.0.0, http://www.agisoft.ru/products/photoscan/), less expertise and fewer control measurements are required compared with traditional photogrammetry, and image processing is automated. Differential GPS data will be used to geo-reference the models to facilitate comparison. The relative advantages, limitations and cost-effectiveness of each approach will be established, and which technique, or combination of techniques, is most appropriate to monitor, model and estimate soil erosion at the national scale, determined.

Electromagnetic Imaging Methods for Nondestructive Evaluation Applications

PubMed Central

Deng, Yiming; Liu, Xin

2011-01-01

Electromagnetic nondestructive tests are important and widely used within the field of nondestructive evaluation (NDE). The recent advances in sensing technology, hardware and software development dedicated to imaging and image processing, and material sciences have greatly expanded the application fields, sophisticated the systems design and made the potential of electromagnetic NDE imaging seemingly unlimited. This review provides a comprehensive summary of research works on electromagnetic imaging methods for NDE applications, followed by the summary and discussions on future directions. PMID:22247693

A West Virginia case study: does erosion differ between streambanks clustered by the bank assessment of nonpoint source consequences of sediment (BANCS) model parameters?

Treesearch

Abby L. McQueen; Nicolas P. Zegre; Danny L. Welsch

2013-01-01

The integration of factors and processes responsible for streambank erosion is complex. To explore the influence of physical variables on streambank erosion, parameters for the bank assessment of nonpoint source consequences of sediment (BANCS) model were collected on a 1-km reach of Horseshoe Run in Tucker County, West Virginia. Cluster analysis was used to establish...

Rapid Gorge Formation in an Artificially Created Waterfall

NASA Astrophysics Data System (ADS)

Anton, L.; Mather, A. E.; Stokes, M.; Munoz Martin, A.

2014-12-01

A number of studies have examined rates of gorge formation, nick point retreat, and the controls on those rates via bedrock erodibility, the effectiveness of bedrock erosion mechanisms and the role of hillslope processes. Most findings are based on conceptual / empirical models or long term landscape analysis; but studies of recent quantifiable events are scarce yet highly valuable. Here we present expert eye witness account and quantitative survey of large and rapid fluvial erosion events that occurred over an artificially created waterfall at a spillway mouth. In 6 years a ~270 m long, ~100 m deep and ~100 to 160 m wide canyon was carved, and ~1.58 x106 m3 of granite bedrock was removed from the spillway site. Available flow data indicates that the erosion took place under unremarkable flood discharge conditions. The analysis of historic topographic maps enables the reconstruction of the former topography and successive erosion events, enabling the quantification of bedrock erosion amounts, and rates. Analysis of bedrock erodibility and discontinuity patterns demonstrates that the bedrock is mechanically strong, and that similar rock strength and fracture patterns are found throughout the region. It is apparent that structural pre-conditioning through fracture density and orientation in relation to flow and slope direction is of paramount importance in the gorge development. The presented example provides an exceptional opportunity for studying the evolution process of a bedrock canyon and to precisely measure the rate of bedrock channel erosion over a six year period. Results illustrate the highly episodic nature of the erosion and highlight several key observations for the adjustability of bedrock rivers. The observations have implications for the efficiency of bedrock erosion and raise important questions about incision rates, driving mechanisms and timescale assumptions' in models of landscape change.

Hybrid Contactless Heating and Levitation

NASA Technical Reports Server (NTRS)

Lee, M. C.

1985-01-01

Acoustic and electromagnetic fields applied. In contactless processing apparatus, acoustic and electromagnetic levitating fields employed alternately or simultaneously with amplitude of each controlled to produce various combinations of heating, cooling, and levitation. Apparatus provides rapid heating and cooling or slow heating and cooling for such processes as nucleation, crystallization, incubation, deep undercooling, and heterogeneity control.

Footwear scanning systems and methods

DOEpatents

Fernandes, Justin L.; McMakin, Douglas L.; Sheen, David M.; Tedeschi, Jonathan R.

2017-07-25

Methods and apparatus for scanning articles, such as footwear, to provide information regarding the contents of the articles are described. According to one aspect, a footwear scanning system includes a platform configured to contact footwear to be scanned, an antenna array configured to transmit electromagnetic waves through the platform into the footwear and to receive electromagnetic waves from the footwear and the platform, a transceiver coupled with antennas of the antenna array and configured to apply electrical signals to at least one of the antennas to generate the transmitted electromagnetic waves and to receive electrical signals from at least another of the antennas corresponding to the electromagnetic waves received by the others of the antennas, and processing circuitry configured to process the received electrical signals from the transceiver to provide information regarding contents within the footwear.

Study on electromagnetic radiation and mechanical characteristics of coal during an SHPB test

NASA Astrophysics Data System (ADS)

Chengwu, Li; Qifei, Wang; Pingyang, Lyu

2016-06-01

Dynamic loads provided by a Split Hopkinson pressure bar are applied in the impact failure experiment on coal with an impact velocity of 4.174-17.652 m s-1. The mechanical property characteristics of coal and an electromagnetic radiation signal can be detected and measured during the experiment. The variation of coal stress, strain, incident energy, dissipated energy and other mechanical parameters are analyzed by the unidimensional stress wave theory. It suggests that with an increase of the impact velocity, the mechanical parameters and electromagnetic radiation increased significantly and the dissipated energy of the coal sample has a high discrete growing trend during the failure process of coal impact. Combined with the received energy of the electromagnetic radiation signal, the relationship between these mechanical parameters and electromagnetic radiation during the failure process of coal burst could be analyzed by the grey correlation model. The results show that the descending order of the gray correlation degree between the mechanical characteristics and electromagnetic radiation energy are impact velocity, maximum stress, the average stress, incident energy, the average strain, maximum strain, the average strain rate and dissipation energy. Due to the correlation degree, the impact velocity and incident energy are relatively large, and the main factor affecting the electromagnetic radiation energy of coal is the energy magnitude. While the relationship between extreme stress and the radiation energy change trend is closed, the stress state of coal has a greater impact on electromagnetic radiation than the strain and destruction which can deepen the research of the coal-rock dynamic disaster electromagnetic monitoring technique.

RSRM Nozzle Anomalous Throat Erosion Investigation Overview

NASA Technical Reports Server (NTRS)

Clinton, R. G., Jr.; Wendel, Gary M.

1998-01-01

In September, 1996, anomalous pocketing erosion was observed in the aft end of the throat ring of the nozzle of one of the reusable solid rocket motors (RSRM 56B) used on NASA's space transportation system (STS) mission 79. The RSRM throat ring is constructed of bias tape-wrapped carbon cloth/ phenolic (CCP) ablative material. A comprehensive investigation revealed necessary and sufficient conditions for occurrence of the pocketing event and provided rationale that the solid rocket motors for the subsequent mission, STS-80, were safe to fly. The nozzles of both of these motors also exhibited anomalous erosion similar to, but less extensive than that observed on STS-79. Subsequent to this flight, the investigation to identify both the specific causes and the corrective actions for elimination of the necessary and sufficient conditions for the pocketing erosion was intensified. A detailed fault tree approach was utilized to examine potential material and process contributors to the anomalous performance. The investigation involved extensive constituent and component material property testing, pedigree assessments, supplier audits, process audits, full scale processing test article fabrication and evaluation, thermal and thermostructural analyses, nondestructive evaluation, and material performance tests conducted using hot fire simulation in laboratory test beds and subscale and full scale solid rocket motor static test firings. This presentation will provide an over-view of the observed anomalous nozzle erosion and the comprehensive, fault-tree based investigation conducted to resolve this issue.

Coupled analysis on landscape pattern and hydrological processes in Yanhe watershed of China.

PubMed

Li, J; Zhou, Z X

2015-02-01

As a typical experimental Soil and Water Conservation District, Yanhe watershed has long been plagued by soil erosion due to severe human disturbances. Exerting remote sensing (RS) and geographic information system (GIS) technology, this paper firstly analyzed and simulated ecological hydrological process in Yanhe watershed based on SWAT model, constructed a comprehensive landscape indices which was closely related to soil erosion, and reflected the coupling relationship between regional landscape pattern change and soil erosion. The results are as follows: (1) Areas of different land use types remained relatively stable from 1990 to 2000 and then changed drastically from 2000 to 2010, which was characterized by lawn expansion and cultivated land shrinkage. (2) In terms of the spatial heterogeneity of hydrological response unit (HRUs), the correlation coefficient of seven selected landscape indices and runoff was very small, and cannot pass all significant testing. But correlation between the indices and sediment yield except for Total Core Area (TCA) and Interspersion and Juxtaposition Index (IJI) was remarkable. (3) According to 'the source-sink' theory of soil erosion, new landscape index-slope-HRU landscape index (SHLI) was built, and reflected the relationship between landscape pattern and soil erosion processes to a certain extent. (4) Coupling relationship between SHLI in 2010 and annual sediment was very prominent. In the sub-basin scale, SHLI has obvious regional differentiation from annual sediment. Copyright © 2014 Elsevier B.V. All rights reserved.

Carbon and nitrogen loss during initial erosion processes under litter cover

NASA Astrophysics Data System (ADS)

Seitz, Steffen; Goebes, Philipp; Kühn, Peter; Scholten, Thomas

2013-04-01

Soil erosion translocates carbon (C) and nitrogen (N) from the soil pool. In natural or near-natural ecosystems like forests the soil is usually covered by litter. It can be assumed that litter decomposition and dust particles adhered on the surface of the leaves contribute to C and N fluxes during erosion processes as well. To our knowledge, the contribution of these compartments to the C and N balance of soil erosion is not yet known. As part of the "New Integrated Litter Experiment" within the DFG research unit "Biodiversity and Ecosystem Functioning (BEF)-China" we conducted a rainfall simulation experiment to quantify the role of litter cover for C and N fluxes during soil erosion in subtropical China. 96 mini runoff plots (40cm x 40cm) were established and divided into four blocks, two of them replicates. Seven different domestic litter species were used in this study combined to 1-species, 2-species and 4-species mixtures and complemented by none species plots (bare ground). Erosion processes were initiated by artificial rainfall using a rainfall simulator with a continuous and stable intensity of 60 mm/h. Sediment discharge and runoff volume were measured every 5 minutes for 20 minutes of rainfall duration and filtrated in the laboratory. Two time steps of rainfall simulation were carried out (summer 2012 and autumn 2012). Total C and N content were quantified from the solid sediment and the liquid runoff volume. Leaf decomposition rates were calculated based on the mass, leaf litter coverage was measured and loss of C and N contents from the decomposing leaves were provided by other project members. Additionally, C and N content of corresponding soils were designated. Lab work and statistical analysis are still ongoing. First results show that C and N concentrations of runoff and sediment are slightly higher for plots covered by litter than bare plots during the first run in summer 2012. It seems that 4-species plots have the highest C and N flux during rainfall simulation. Further analysis will focus on the role of litter diversity on C and N concentration and fluxes during initial erosion processes.

The new conversion model MODERN to derive erosion rates from inventories of fallout radionuclides

NASA Astrophysics Data System (ADS)

Arata, Laura; Meusburger, Katrin; Frenkel, Elena; A'Campo-Neuen, Annette; Iurian, Andra-Rada; Ketterer, Michael E.; Mabit, Lionel; Alewell, Christine

2016-04-01

The measurement of fallout radionuclides (FRNs) has become one of the most commonly used methods to quantify soil erosion and depositional processes. FRNs include anthropogenic radionuclides (e.g. 137Cs, 239+240Pu) released into the atmosphere during nuclear bomb tests and power plant accidents (e.g Chernobyl, Fukushima-Daiichi), as well as natural radiotracers such as 210Pbex and 7Be. FRNs reach the land surface by dry and wet fallouts from the atmosphere. Once deposited, FRNs are tightly adsorbed by fine soil particles and their subsequent redistribution is mostly associated with soil erosion processes. FRNs methods are based on a qualitative comparison: the inventory (total radionuclide activity per unit area) at a given sampling site is compared to that of a so called reference site. The conversion of FRN inventories into soil erosion and deposition rates is done with a variety of models, which suitability is dependent on the selected FRN, soil cultivation (ploughed or unploughed) and movement (erosion or deposition). The authors propose a new conversion model, which can be easily and comprehensively used for different FRNs, land uses and soil redistribution processes. This new model i.e. MODERN (MOdelling Deposition and Erosion rates with RadioNuclides) considers the precise depth distribution of a given FRN at a reference site, and allows adapting it for any specific site conditions. MODERN adaptability and performance has been tested on two published case studies: (i) a 137Cs study in an alpine and unploughed area in the Aosta valley (Italy) and (ii) a 210Pbex study on a ploughed area located in Romania. The results show a good agreement and a significant correlation (r= 0.91, p<0.0001) between the results of MODERN and the published models currently used by the FRN scientific community (i.e. the Profile Distribution Model and the Mass Balance Model). The open access code and the cost free accessibility of MODERN will ensure the promotion of a wider application of FRNs for investigating soil erosion and sedimentation processes.

Modelling the impacts of barrier-island transgression and anthropogenic disturbance on blue carbon budgets

NASA Astrophysics Data System (ADS)

Theuerkauf, E. J.; Rodriguez, A. B.

2017-12-01

The size of backbarrier saltmarsh carbon reservoirs are dictated by transgressive processes, such as erosion and overwash, yet these processes are not included in blue carbon budgets. These carbon reservoirs are presumed to increase through time if marsh elevation is keeping pace with sea-level rise. However, changes in marsh width due to erosion and overwash can alter carbon budgets and reservoirs. To explore the impacts of these processes on transgressive barrier island carbon budgets and reservoirs we developed and tested a transect model. The model couples a carbon storage term driven by backbarrier marsh width and a carbon export term driven by ocean and backbarrier shoreline erosion. We tested the model using data collected from two transgressive barrier islands in North Carolina with different backbarrier settings. Core Banks is an undeveloped barrier island with a wide backbarrier marsh and lagoon, hence, landward migration of the island (rollover) is unimpeded. Barrier rollover is impeded at Onslow Beach as there is no backbarrier lagoon and the island is immediately adjacent to steeper mainland topography. Sediment cores were collected to determine carbon storage rates as well as the quantity of carbon exported from eroding marsh. Backbarrier marsh erosion rates, ocean shoreline erosion rates, and changes in marsh width were determined from aerial photographs. Output from the model indicated that hurricane erosion and overwash as well as human disturbance from the construction of the Intracoastal Waterway temporarily transitioned the Onslow Beach sites to carbon sources. Through time, the carbon reservoir at this barrier continued to decrease as carbon export outpaced carbon storage. The carbon reservoir will continue to exhaust as the ocean shoreline migrates landward given the inability for new marsh to form during island rollover. At Core Banks, barrier rollover is unimpeded and new saltmarsh can form during transgression. The Core Banks site only briefly became a carbon source during an erosive period; otherwise the island functioned as a carbon sink and the reservoir increased across the past century. Our model results indicate barrier island setting controls the sustainability of the carbon reservoir and that transgressive processes should be included in coastal carbon budgets.

Geomorphic Implications of Fire and Slope Aspect in the Jemez Mountains, New Mexico, USA

NASA Astrophysics Data System (ADS)

Fitch, E. P.; Meyer, G. A.

2011-12-01

Following a fire, extensive erosion may occur on hillslopes due to reduced infiltration and increased runoff as well as a decrease in vegetative anchoring and surface roughness. This increased erosion and subsequent sedimentation on alluvial fans at the base of the hillslope may be the primary process of geomorphic change in fire-prone mountains in the Western US. Insolation differences on north and south facing slopes may also be another potential influence on geomorphic change due to soil moisture and vegetation differences, which may affect the spatial distribution of erosion as well as sediment transport processes. Due to the long recovery period of forest stands in fire-prone areas, it is important to understand the natural variability of erosion for the purposes of forest and river ecology and management as well as mass movement-flooding hazard. The 2002 Lakes Fire area in the Jemez Mountains, NM, provides a natural study area with incision of alluvial fans after the Lakes Fire exposing the internal structure of these fans. The study area displays steeper, drier ponderosa pine dominated south-facing slopes and less steep, moister Douglas-fir dominated north-facing slopes, which suggests that slope aspect may influence fire regime and post-fire erosion in the Jemez Mountains. In order to determine the importance of fire and aspect on erosion and sedimentation, over 15 sections within alluvial fans with both north and south aspect were studied. Debris flow, hyperconcentrated flow and stream flow make up the majority of sediment transport processes in this area. Therefore, deposits formed by these processes were described, and evidence for fire-related sedimentation was assessed. Additionally, the relative importance of sediment transport types in relation to north versus south slope aspects was examined. Finally, charcoal fragments within deposits from north and south aspects were analyzed in terms of their abundance and angularity in order to aid in estimating the severity of the fire event associated with the deposit. In this way, the importance of fire and aspect in influencing erosion and sediment transport was assessed for the study area.

Erosion risk assessment along coastlines, rivers, and lakes

NASA Astrophysics Data System (ADS)

Eidsvig, Unni; Harbitz, Carl B.; Issler, Dieter; Forsberg, Carl Fredrik; Høydal, Øyvind A.; Glimsdal, Sylfest; Frauenfelder, Regula

2017-04-01

An effect of the expected climate changes is that densely populated areas will be more exposed to natural hazards. There is a rising concern about geotechnical challenges associated with the transition zone between water and land, in particular with regard to erosion. This needs to be considered as part of the climate adaptation strategies in the society and applies to both coastal settlements and to settlements along rivers. Climate change, as reported by the IPCC, includes global warming, sea level rise as well as more precipitation, both with respect to intensity and frequency. A larger number of cities are expected to be affected by floods and with higher frequency. With large floods, the current speed in rivers and hence their erosion potential increases, leading to scouring along riverbanks, where important transport routes and other infrastructure are often located. The frequency and intensity of storm surges are expected to increase, as well as the risk of coastal erosion. In steep terrain, the likelihood of debris flows increases. The project "Multi-scale Erosion Risk under Climate Change" was initiated to prepare for such challenges as well as local climate adaptation. The project is an internal NGI strategic project funded by the Research Council of Norway for the period 2017 - 2019. The project aims to investigate relevant erosive and mass-flow processes in the coastal zone, along rivers, and in lakes. Further, the knowledge and tools to be developed within the project aim to reduce the risk associated with these processes, through appropriate land-use planning and innovative mitigation measures. The project is thematically subdivided into the following five work packages: WP1: Modelling of erosion processes in rivers, at the coast and in mass movements WP2: Floods, debris flows and sediment mobility in complex topography WP3: Coastal hydrodynamic processes WP4: Monitoring, warning and non-physical mitigation measures WP5: Dissemination and knowledge sharing In our contribution, we will give an overview of the ideas and the background of the project and present the first preliminary results.

Magnetic Field Would Reduce Electron Backstreaming in Ion Thrusters

NASA Technical Reports Server (NTRS)

Foster, John E.

2003-01-01

The imposition of a magnetic field has been proposed as a means of reducing the electron backstreaming problem in ion thrusters. Electron backstreaming refers to the backflow of electrons into the ion thruster. Backstreaming electrons are accelerated by the large potential difference that exists between the ion-thruster acceleration electrodes, which otherwise accelerates positive ions out of the engine to develop thrust. The energetic beam formed by the backstreaming electrons can damage the discharge cathode, as well as other discharge surfaces upstream of the acceleration electrodes. The electron-backstreaming condition occurs when the center potential of the ion accelerator grid is no longer sufficiently negative to prevent electron diffusion back into the ion thruster. This typically occurs over extended periods of operation as accelerator-grid apertures enlarge due to erosion. As a result, ion thrusters are required to operate at increasingly negative accelerator-grid voltages in order to prevent electron backstreaming. These larger negative voltages give rise to higher accelerator grid erosion rates, which in turn accelerates aperture enlargement. Electron backstreaming due to accelerator-gridhole enlargement has been identified as a failure mechanism that will limit ionthruster service lifetime. The proposed method would make it possible to not only reduce the electron backstreaming current at and below the backstreaming voltage limit, but also reduce the backstreaming voltage limit itself. This reduction in the voltage at which electron backstreaming occurs provides operating margin and thereby reduces the magnitude of negative voltage that must be placed on the accelerator grid. Such a reduction reduces accelerator- grid erosion rates. The basic idea behind the proposed method is to impose a spatially uniform magnetic field downstream of the accelerator electrode that is oriented transverse to the thruster axis. The magnetic field must be sufficiently strong to impede backstreaming electrons, but not so strong as to significantly perturb ion trajectories. An electromagnet or permanent magnetic circuit can be used to impose the transverse magnetic field downstream of the accelerator-grid electrode. For example, in the case of an accelerator grid containing straight, parallel rows of apertures, one can apply nearly uniform magnetic fields across all the apertures by the use of permanent magnets of alternating polarity connected to pole pieces laid out parallel to the rows, as shown in the left part of the figure. For low-temperature operation, the pole pieces can be replaced with bar magnets of alternating polarity. Alternatively, for the same accelerator grid, one could use an electromagnet in the form of current-carrying rods laid out parallel to the rows.

Analysis of Actual Soil Degradation by Erosion Using Satellite Imagery and Terrain Attributes in the Czech Republic

NASA Astrophysics Data System (ADS)

Zizala, Daniel

2015-04-01

Soil water and wind erosion (possibly tillage erosion) is the most significant soil degradation factor in the Czech Republic. Moreover, this phenomenon also affects seriously quality of water sources., About 50 % of arable land are endangered by water erosion and about 10 % of arable land are endangered wind erosion in the Czech Republic. These processes have been accelerated by human activity. Specific condition of agriculture land in the Czech Republic including highland relief and particularly size of land parcel and intensification of agriculture does not enable to reduce flow of runoff water. Insufficient protection against accelerated erosion processes is related to lack of landscape and hydrographic elements and large area of agricultural plots. Currently, this issue is solved at plot scale by field investigation or at regional scale using numerical and empirical erosion models. Nevertheless, these models enable only to predict the potential of soil erosion. Large scale assessment of actual degradation level of soils is based on expert knowledge. However, there are still many uncertainties in this issue. Therefore characterization of actual degradation level of soil is required especially for assessment of long-term impact of soil erosion on soil fertility. Soil degradation by erosion can be effectively monitored or quantified by modern tools of remote sensing with variable level of detail accessible. Aims of our study is to analyse the applicability of remote sensing for monitoring of actual soil degradation by erosion. Satellite and aerial image data (multispectral and hyperspectral), terrain attributes and data from field investigation are the main source for this analyses. The first step was the delimitation of bare soils using supervised classification of the set of Landsat scenes from 2000 - 2014. The most suitable period of time for obtaining spectral image data with the lowest vegetation cover of soil was determined. The results were verified by statistical data of areas under farm crops from Czech Statistical Office. Information on number of scenes where bare soils are identified for each land parcel is available. This set of images with bare soils is used for assessment of soil degradation stage. Some land parcels were found without vegetation cover up to 40 times. Analysis was performed on 5 test sites in the Czech Republic and also using data from database of Soil Erosion Monitoring of Agricultural Land. Currently, more than 500 erosion events are registered in this database. Additional remote sensing data (Hyperion data, aerial hyperspectral data) was used for detailed analysis on the test sites. Results reveal that satellite imagery set, soil maps, terrain attributes and erosion modelling can be successfully applied in assessment of actual soil degradation by erosion. The research has been supported by the project no. QJ330118 "Using Remote Sensing for Monitoring of Soil Degradation by Erosion and Erosion Effects" funding by Ministry of Agriculture.

Sediment transport dynamics in the Central Himalaya: assessing during monsoon the erosion processes signature in the daily suspended load of the Narayani river

NASA Astrophysics Data System (ADS)

Morin, Guillaume; Lavé, Jérôme; Lanord, Christian France; Prassad Gajurel, Ananta

2017-04-01

The evolution of mountainous landscapes is the result of competition between tectonic and erosional processes. In response to the creation of topography by tectonics, fluvial, glacial, and hillslope denudation processes erode topography, leading to rock exhumation and sediment redistribution. When trying to better document the links between climate, tectonic, or lithologic controls in mountain range evolution, a detailed understanding of the influence of each erosion process in a given environment is fundamental. At the scale of a whole mountain range, a systematic survey and monitoring of all the geomorphologic processes at work can rapidly become difficult. An alternative approach can be provided by studying the characteristics and temporal evolution of the sediments exported out of the range. In central Himalaya, the Narayani watershed presents contrasted lithologic, geochemical or isotopic signatures of the outcropping rocks as well as of the erosional processes: this particular setting allows conducting such type of approach by partly untangling the myopic vision of the spatial integration at the watershed scale. Based on the acquisition and analysis of a new dataset on the daily suspended load concentration and geochemical characteristics at the mountain outlet of one of the largest Himalayan rivers (drainage area = 30000 km2) bring several important results on Himalayan erosion, and on climatic and process controls. 1. Based on discrete depth sampling and on daily surface sampling of suspended load associated to flow characterization through ADCP measurements, we were first able to integrate sediment flux across a river cross-section and over time. We estimate for 2010 year an equivalent erosion rate of 1.8 +0.35/-0.2 mm/yr, and over the last 15 years, using past sediment load records from the DHM of Nepal, an equivalent erosion rate of 1.6 +0.3/-0.2 mm/yr. These rates are also in close agreement with the longer term ( 500 yrs) denudation rates of 1.7 mm/yr obtained from cosmonuclides in Narayani river sands (Lupker et al. 2012). Such stability of the erosion rates suggests that either buffering behaviour of this large watershed or broad spatial integration dampen the variability in monsoon strength or the sporadic nature of extreme mass-wasting events. 2. Paradoxically, the relatively high variability of the daily geochemical signature in suspended load and the apparent absence of delay between high rainfall episodes and sediment export suggest very short transfer time for silt and medium sand load, despite fluvial transfer distance of hundreds of kilometres between the sediment sources and the mountain outlet. This implies the absence of a buffering behaviour of the fluvial network and a very reactive fluvial system, which would be strongly supply limited relative to the fine sediment fraction. 3. By analysing sediments fluxes and using geochemical compositions in deltaD, carbonates content and TOC, which we propose as possible tracers for glacier- and soil-derived material, we show that glacier and soil erosion contribute to annual erosion budget to less than 10% and a few % respectively. Their imprints in Narayani sediment is only visible during the pre- and early monsoon before being overwhelmed by landslide-derived material during the monsoon. 4. Hillslope erosion by landslides appears therefore as the dominant erosional process in central Himalaya, and by comparing the sediment export history to a rainfall/runoff model, we confirm Gabet et al.'s (2004) inference that sediment export and possibly landslide triggering on Himalayan hillslopes are controlled both by pore pressure (depending on cumulated precipitation) and daily rainfall intensity.

Spiders: water-driven erosive structures in the southern hemisphere of Mars.

PubMed

Prieto-Ballesteros, Olga; Fernández-Remolar, David C; Rodríguez-Manfredi, José Antonio; Selsis, Franck; Manrubia, Susanna C

2006-08-01

Recent data from space missions reveal that there are ongoing climatic changes and erosive processes that continuously modify surface features of Mars. We have investigated the seasonal dynamics of a number of morphological features located at Inca City, a representative area at high southern latitude that has undergone seasonal processes. By integrating visual information from the Mars Orbiter Camera on board the Mars Global Surveyor and climatic cycles from a Mars' General Circulation Model, and considering the recently reported evidence for the presence of water-ice and aqueous precipitates on Mars, we propose that a number of the erosive features identified in Inca City, among them spiders, result from the seasonal melting of aqueous salty solutions.

The Future Role of Information Technology in Erosion Modelling

USDA-ARS?s Scientific Manuscript database

Natural resources management and decision-making is a complex process requiring cooperation and communication among federal, state, and local stakeholders balancing biophysical and socio-economic concerns. Predicting soil erosion is common practice in natural resource management for assessing the e...

NEW GIS WATERSHED ANALYSIS TOOLS FOR SOIL CHARACTERIZATION AND EROSION AND SEDIMENTATION MODELING

EPA Science Inventory

A comprehensive procedure for computing soil erosion and sediment delivery metrics has been developed which utilizes a suite of automated scripts and a pair of processing-intensive executable programs operating on a personal computer platform.

An investigation of environmental factors associated with the current and proposed jetty systems at Belle Pass, Louisiana

NASA Technical Reports Server (NTRS)

Dantin, E. J.; Whitehurst, C. A.; Durbin, W. T.

1974-01-01

The history of the existing jetty system at Belle Pass was investigated to determine its past effect on the littoral currents and beach erosion. Present flow patterns and erosion rates were also studied, along with the prevailing recession rates of local beaches not influenced by the jetty system. Aerial photographs and maps were used in conjunction with periodic hydraulic measurements, ground observations, and physical measurements of beach erosion. A scale model was constructed to further the study of flow patterns and velocities. It is shown that the existing jetty has not adversely affected the coastline in the area; erosive processes have been retarded by the jetty and its companion groin. Future erosion patterns are predicted, and projected effects of the proposed jetty system are given.

Water droplet erosion mechanisms of Ti-6Al-4V

NASA Astrophysics Data System (ADS)

Kamkar Zahmatkesh, Niloofar

Water impingement erosion of materials can be a life-limiting phenomenon for the components in many erosive environments. For example, aircraft body exposed to rain, steam turbine blade, and recently in gas turbine coupled with inlet fogging system. The last is the focus of this study. Inlet fogging system is the most common method used to augment gas turbine output during hot days; high ambient temperature causes strong deterioration of the engine performance. Micro-scaled droplets introduced into the inlet airflow allow the cooling of entering air as well as intercooling the compressor (overspray) and thus optimizes the output power. However, erosion damage of the compressor blades in overspray stage is one of the major concerns associated with the inlet fogging system. The main objective of this research work (CRIAQ MANU419 project) is to understand the erosion induced by water droplets on Titanium alloy to eventually optimize the erosion resistance of the Ti-based compressor blade. Therefore, characterization of the water droplet erosion damage on Ti-6Al-4V receives the major importance. The influence of base material microstructure and impact parameters were considered in erosion evaluation in present study. This work covers the characterization of the erosion damage on Ti-6Al-4V alloy in two parts: - The water droplet erosion damage through a novel experimental approach. The collected data were processed both qualitatively and quantitatively for multi-aspects damage study. - The influence of impact velocity on erosion in an attempt to represent the in-service conditions.

Wind, rain and soil erosion rates on bare and plant covered agriculture plots at the experimental station of El Teularet -Sierra de Enguera, Eastern Spain

NASA Astrophysics Data System (ADS)

Cerdà, A.; Azorin-Molina, C.; Iserloh, Th.

2012-04-01

Soil erosion is being scientifically researched for more tan one century, but there is some knowledge lacks that should be researched. Within the factors of the soil erosion wind and rain were studied, but little is know about the impact of the combination of both. Soil erosion by wind was mainly studied on drylands and agriculture land (Sterk and Spaan, 1997; Bielders et al., 2002; Rajot et al., 2003; Zobeck et al., 2003). Soil erosion by water was studied in many ecosystems but it is especially active on agriculture land (Cerdà et al., 2009) and under Mediterranean climatic conditions (Cerdà et al., 2010). The importance of wind on soil erosion is base in the fact that rainstorms occurs with wind, adding a driving component to the falling raindrops. The influence of wind on raindrops is clear, but there is not measurements and there is no information of this influence under field conditions with natural rainfall events.This paper aims to determine the interaction between wind and rain as factors of the soil losses under Mediterranean climatic conditions and different agriculture managements and land uses. Since 2003, the El Teularet-Serra de Enguera Soil Erosion Experimental Station located in Eastern Spain is measuring the soil losses in plots under different land uses and land managements. The station is devoted to study the soil water erosion processes under rain-fed agriculture fields and the rangelands by means of simulated rainfall experiments and plots of different sizes. The soil erosion measure ments are done by means of 13 plots, each of them composed of 5 subplots of 1, 2, 4, 16 and 48 m2 under different land uses and managements. Two plots are covered by two different types of shrubs: Quercus coccifera and Ulex parviflorus, respectively. Three plots reproduce the use of herbicides, one is ploughed, and three plots follow conservation practices (oats and beans with no-tillage, with tillage, and with a vege- tation cover of weeds). Other plots are covered with straw, chipped branches of olive and with a geotextil developed specifically to control erosion on agricultural fields. The Soil Erosion Experimental Station of the El Teularet-Serra de Enguera is located in Eastern Spain. The station is devoted to study the soil water erosion processes under rain-fed agriculture fields and the rangelands. Agriculture is the main source of sedi ments on the mountainous areas of Spain due to the current management. The exper imental station of the El Teularet-Sierra de Enguera is composed also of a meteorological station with tipping-bucket raingauges (0.2 mm), and sensors that measure soil and air moisture and temperature, wind direction and speed and the sun radiation connected to a data-logger that record these data every five minutes. This paper will review the data collected during the period 2004 to 2011 in order to determine if the wind direction and wind speed determined the soil erosion rates. In this way it will be clarified the infliuence of wind on the soil erosion processes.The results will be compared to the measurement collected at the Montesa experimental station devoted to the study of soil erosion on citrus orchards. The experimental setup within the citrus plantation is being supported by the research project CGL2008- 02879/BTE.

Tackling soil degradation and environmental changes in Lake Manyara Basin, Tanzania to support sustainable landscape/ecosystem management.

NASA Astrophysics Data System (ADS)

Munishi, Linus; Mtei, Kelvin; Bode, Samuel; Dume, Bayu; Navas, Ana; Nebiyu, Amsalu; Semmens, Brice; Smith, Hugh; Stock, Brian; Boeckx, Pascal; Blake, Will

2017-04-01

The Lake Manyara Basin (LMB), which encompasses Lake Manyara National Park a world ranking World Biosphere Reserve, is of great ecological and socio-economic value because it hosts a small-holder rain fed and extensive irrigation agriculture, grazing grounds for pastoralists, terrestrial and aquatic habitat for wildlife and tourism business contributing to poverty alleviation. Despite these multiple ecosystem services that support the local communities, the LMB is threatened by; (a) siltation from eroded soil fed from the wider catchment and rift escarpment of the basin and (b) declining water levels due to water capture by agriculture and possibly climate change. These threats to the ecosystem and its services are augmented by increasing human population, pollution by agricultural pesticides, poaching, human encroachment and infrastructure development, and illegal fisheries. Despite these challenges, here is a dearth of information on erosion hotspots and to date soil erosion and siltation problems in LMB have been interpreted largely in qualitative terms, and no coherent interpretative framework of these records exists. Despite concerns that modern sediment fluxes to the Lake may exceed long-term fluxes, little is known about erosion sources, how erosion rates and processes vary across the landscape and how erosion rates are influenced by the strong climate gradients in the basin. This contribution describes a soil erosion and sediment management project that aims to deliver a demonstration dataset generated from inter-disciplinary sediment-source tracing technologies and approaches to assess erosion hotspots, processes and spatial patterns of erosion in the area. The work focuses on a sub basin, the Monduli Sub catchment, located within the greater LMB. This is part of efforts to establish an understanding of soil erosion and landscape degradation in the basin as a pathway for generating and developing knowledge, building capacity to assist conservationists, farmers and pastoralists, agro-entrepreneurs, and their support agents to address the problems while feeding the information into the national development policies in Tanzania and the entire East African region.

High natural erosion rates are the backdrop for enhanced anthropogenic soil erosion in the Middle Hills of Nepal

NASA Astrophysics Data System (ADS)

West, A. J.; Arnold, M.; Aumaître, G.; Bourlès, D. L.; Keddadouche, K.; Bickle, M.; Ojha, T.

2014-08-01

Although agriculturally accelerated soil erosion is implicated in the unsustainable environmental degradation of mountain environments, such as in the Himalaya, the effects of land use can be difficult to quantify in many mountain settings because of the high and variable natural background rates of erosion. In this study, we present new long-term denudation rates, derived from cosmogenic 10Be analysis of quartz in river sediment from the Likhu Khola, a small agricultural river basin in the Middle Hills of central Nepal. Calculated long-term denudation rates, which reflect background natural erosion processes over 1000+ years prior to agricultural intensification, are similar to present-day sediment yields and to soil loss rates from terraces that are well-maintained. Similarity in short- and long-term catchment-wide erosion rates for the Likhu is consistent with data from elsewhere in the Nepal Middle Hills, but contrasts with the very large increases in short-term erosion rates seen in agricultural catchments in other steep mountain settings. Our results suggest that the large sediment fluxes exported from the Likhu and other Middle Hills rivers in the Himalaya are derived in large part from natural processes, rather than from soil erosion as a result of agricultural activity. Because of the high natural background rates, simple comparison of short- and long-term rates may not reveal unsustainable soil degradation, particularly if much of the catchment-scale erosion flux derives from mass wasting. Correcting for the mass wasting contribution in the Likhu implies minimum catchment-averaged soil production rates of ~0.25-0.35 mm yr-1. The deficit between these production rates and soil losses suggests that terraced agriculture in the Likhu may not be associated with a large systematic soil deficit, at least when terraces are well maintained, but that poorly managed terraces, forest and scrubland may lead to rapid depletion of soil resources.

Reconstructing geomorphic patterns and forcing factors from Alpine Lake Sediment

NASA Astrophysics Data System (ADS)

Arnaud, Fabien; Poulenard, Jérôme; Giguet-Covex, Charline; Wilhelm, Bruno; Révillon, Sidonie; Jenny, Jean-Philippe; Revel, Marie; Enters, Dirk; Bajard, Manon; Fouinat, Laurent; Doyen, Elise; Simonneau, Anaëlle; Pignol, Cécile; Chapron, Emmanuel; Vannière, Boris; Sabatier, Pierre

2017-04-01

In this paper we review the scientific efforts that were led over the last decades to reconstruct geomorphic patterns from continuous alpine lake sediment records. Whereas our results point a growing importance of humans as erosion forcing factors, we will focus here on climate-related processes. Our main dataset is made of a regional approach which was led without any a priori regarding erosion forcing factors. We hence integrated a set of sediment sequences from various environment along an altitudinal gradient from 200 up to 2400m asl in Northern French Alps. Altogether our data point climate change as one of the main factor of erosion variability. In particular, the last two cold spells that occurred during the early middle age (Dark Age) and between the 14th and the 20th century AD (Little Ice Age) appear to be outstanding compared to any other periods of enhanced erosion along the Holocene. The climatic forcing of those erosion phases is supported by an increase in the contribution of glacier-eroded material at a regional scale. At local scales, our data also point the growing importance, since at least the mid Bronze Age (ca. 3500 cal. BP) of human activities as a major erosion factor. This influence peaked during the late Iron Age and Antiquity periods (200 BC - 400 AD) when we record a regional generalised period of enhanced erosion in response to the development of pasturing activities. Thanks to provenance and weathering markers, we evidenced a strong relationship between the changes in ecosystems, soil development and erosion patterns. We hence showed the vegetal colonisation of bared soil led to a period of intense weathering while new soils were under formation between 11,000 and 8,000 cal. BP. Soils then knew an optimum until the onset of the Neoglacial at ca. 4,500 cal. BP prior to decline under both climate and human pressures. Altogether our data point the complexity of processes that affected the Earth critical zone along the Holocene. However, we highlight the interest of leading spatialized paleo-investigation in order to reconstruct those dynamics through and thus better understand the processes in play in critical zone dynamics over long time periods.

Process based modelling of soil organic carbon redistribution on landscape scale

NASA Astrophysics Data System (ADS)

Schindewolf, Marcus; Seher, Wiebke; Amorim, Amorim S. S.; Maeso, Daniel L.; Jürgen, Schmidt

2014-05-01

Recent studies have pointed out the great importance of erosion processes in global carbon cycling. Continuous erosion leads to a massive loss of top soils including the loss of organic carbon accumulated over long time in the soil humus fraction. Lal (2003) estimates that 20% of the organic carbon eroded with top soils is emitted into atmosphere, due to aggregate breakdown and carbon mineralization during transport by surface runoff. Furthermore soil erosion causes a progressive decrease of natural soil fertility, since cation exchange capacity is associated with organic colloids. As a consequence the ability of soils to accumulate organic carbon is reduced proportionately to the drop in soil productivity. The colluvial organic carbon might be protected from further degradation depending on the depth of the colluvial cover and local decomposing conditions. Some colluvial sites can act as long-term sinks for organic carbon. The erosional transport of organic carbon may have an effect on the global carbon budget, however, it is uncertain, whether erosion is a sink or a source for carbon in the atmosphere. Another part of eroded soils and organic carbon will enter surface water bodies and might be transported over long distances. These sediments might be deposited in the riparian zones of river networks. Erosional losses of organic carbon will not pass over into atmosphere for the most part. But soil erosion limits substantially the potential of soils to sequester atmospheric CO2 by generating humus. The present study refers to lateral carbon flux modelling on landscape scale using the process based EROSION 3D soil loss simulation model, using existing parameter values. The selective nature of soil erosion results in a preferentially transport of fine particles while less carbonic larger particles remain on site. Consequently organic carbon is enriched in the eroded sediment compared to the origin soil. For this reason it is essential that EROSION 3D provides the grain size distribution (clay, silt and sand) of the transported sediment. A test slope is modeled covering certain land use and soil management scenarios referring to different rainfall events. Results allow first insights on carbon loss and depletion on sediment delivery areas as well as carbon gains and enrichments on deposition areas on landscape scale. Lal, R. (2003). Soil erosion and the global carbon budget. Environment International vol. 29: 437-450.

Assessment of erosion and deposition in steep mountain basins by differencing sequential digital terrain models

NASA Astrophysics Data System (ADS)

Cavalli, Marco; Goldin, Beatrice; Comiti, Francesco; Brardinoni, Francesco; Marchi, Lorenzo

2017-08-01

Digital elevation models (DEMs) built from repeated topographic surveys permit producing DEM of Difference (DoD) that enables assessment of elevation variations and estimation of volumetric changes through time. In the framework of sediment transport studies, DEM differencing enables quantitative and spatially-distributed representation of erosion and deposition within the analyzed time window, at both the channel reach and the catchment scale. In this study, two high-resolution Digital Terrain Models (DTMs) derived from airborne LiDAR data (2 m resolution) acquired in 2005 and 2011 were used to characterize the topographic variations caused by sediment erosion, transport and deposition in two adjacent mountain basins (Gadria and Strimm, Vinschgau - Venosta valley, Eastern Alps, Italy). These catchments were chosen for their contrasting morphology and because they feature different types and intensity of sediment transfer processes. A method based on fuzzy logic, which takes into account spatially variable DTMs uncertainty, was used to derive the DoD of the study area. Volumes of erosion and deposition calculated from the DoD were then compared with post-event field surveys to test the consistency of two independent estimates. Results show an overall agreement between the estimates, with differences due to the intrinsic approximations of the two approaches. The consistency of DoD with post-event estimates encourages the integration of these two methods, whose combined application may permit to overcome the intrinsic limitations of the two estimations. The comparison between 2005 and 2011 DTMs allowed to investigate the relationships between topographic changes and geomorphometric parameters expressing the role of topography on sediment erosion and deposition (i.e., slope and contributing area) and describing the morphology influenced by debris flows and fluvial processes (i.e., curvature). Erosion and deposition relations in the slope-area space display substantial differences between the Gadria and the Strimm basins. While in the former erosion and deposition clusters are reasonably well discriminated, in the latter, characterized by a complex stepped structure, we observe substantial overlapping. Erosion mostly occurred in areas that show persistency of concavity or transformation from convex and flat to concave surfaces, whereas deposition prevailingly took place on convex morphologies. Less expected correspondences between curvature and topographic changes can be explained by the variable sediment transport processes, which are often characterized by alternation of erosion and deposition between different events and even during the same event.

Using Crater Counts to Constrain Erosion Rates on Mars: Implications for the Global Dust Cycle, Sedimentary Rock Erosion and Organic Matter Preservation

NASA Astrophysics Data System (ADS)

Mayer, D. P.; Kite, E. S.

2016-12-01

Sandblasting, aeolian infilling, and wind deflation all obliterate impact craters on Mars, complicating the use of crater counts for chronology, particularly on sedimentary rock surfaces. However, crater counts on sedimentary rocks can be exploited to constrain wind erosion rates. Relatively small, shallow craters are preferentially obliterated as a landscape undergoes erosion, so the size-frequency distribution of impact craters in a landscape undergoing steady exhumation will develop a shallower power-law slope than a simple production function. Estimating erosion rates is important for several reasons: (1) Wind erosion is a source of mass for the global dust cycle, so the global dust reservoir will disproportionately sample fast-eroding regions; (2) The pace and pattern of recent wind erosion is a sorely-needed constraint on models of the sculpting of Mars' sedimentary-rock mounds; (3) Near-surface complex organic matter on Mars is destroyed by radiation in <108 years, so high rates of surface exhumation are required for preservation of near-surface organic matter. We use crater counts from 18 HiRISE images over sedimentary rock deposits as the basis for estimating erosion rates. Each image was counted by ≥3 analysts and only features agreed on by ≥2 analysts were included in the erosion rate estimation. Erosion rates range from 0.1-0.2 {μ }m/yr across all images. These rates represent an upper limit on surface erosion by landscape lowering. At the conference we will discuss the within and between-image variability of erosion rates and their implications for recent geological processes on Mars.

Real-time wideband cylindrical holographic surveillance system

DOEpatents

Sheen, David M.; McMakin, Douglas L.; Hall, Thomas E.; Severtsen, Ronald H.

1999-01-01

A wideband holographic cylindrical surveillance system including a transceiver for generating a plurality of electromagnetic waves; antenna for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; the transceiver also receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; a computer for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and a display for displaying the processed information to determine nature of the target. The computer has instructions to apply Fast Fourier Transforms and obtain a three dimensional cylindrical image.

Real-time wideband holographic surveillance system

DOEpatents

Sheen, David M.; Collins, H. Dale; Hall, Thomas E.; McMakin, Douglas L.; Gribble, R. Parks; Severtsen, Ronald H.; Prince, James M.; Reid, Larry D.

1996-01-01

A wideband holographic surveillance system including a transceiver for generating a plurality of electromagnetic waves; antenna for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; the transceiver also receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; a computer for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and a display for displaying the processed information to determine nature of the target. The computer has instructions to apply a three dimensional backward wave algorithm.

Real-time wideband holographic surveillance system

DOEpatents

Sheen, D.M.; Collins, H.D.; Hall, T.E.; McMakin, D.L.; Gribble, R.P.; Severtsen, R.H.; Prince, J.M.; Reid, L.D.

1996-09-17

A wideband holographic surveillance system including a transceiver for generating a plurality of electromagnetic waves; antenna for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; the transceiver also receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; a computer for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and a display for displaying the processed information to determine nature of the target. The computer has instructions to apply a three dimensional backward wave algorithm. 28 figs.

Illuminating wildfire erosion and deposition patterns with repeat terrestrial lidar

USGS Publications Warehouse

Rengers, Francis K.; Tucker, G.E.; Moody, J.A.; Ebel, Brian

2016-01-01

Erosion following a wildfire is much greater than background erosion in forests because of wildfire-induced changes to soil erodibility and water infiltration. While many previous studies have documented post-wildfire erosion with point and small plot-scale measurements, the spatial distribution of post-fire erosion patterns at the watershed scale remains largely unexplored. In this study lidar surveys were collected periodically in a small, first-order drainage basin over a period of 2 years following a wildfire. The study site was relatively steep with slopes ranging from 17° to > 30°. During the study period, several different types of rain storms occurred on the site including low-intensity frontal storms (2.4 mm h−1) and high-intensity convective thunderstorms (79 mm h−1). These storms were the dominant drivers of erosion. Erosion resulting from dry ravel and debris flows was notably absent at the site. Successive lidar surveys were subtracted from one another to obtain digital maps of topographic change between surveys. The results show an evolution in geomorphic response, such that the erosional response after rain storms was strongly influenced by the previous erosional events and pre-fire site morphology. Hillslope and channel roughness increased over time, and the watershed armored as coarse cobbles and boulders were exposed. The erosional response was spatially nonuniform; shallow erosion from hillslopes (87% of the study area) contributed 3 times more sediment volume than erosion from convergent areas (13% of the study area). However, the total normalized erosion depth (volume/area) was highest in convergent areas. From a detailed understanding of the spatial locations of erosion, we made inferences regarding the processes driving erosion. It appears that hillslope erosion is controlled by rain splash (for detachment) and overland flow (for transport and quasi-channelized erosion), with the sites of highest erosion corresponding to locations with the lowest roughness. By contrast, in convergent areas we found erosion caused by overland flow. Soil erosion was locally interrupted by immobile objects such as boulders, bedrock, or tree trunks, resulting in a patchy erosion network with increasing roughness over time.

Analysis of erosion and transportation features from lunar orbiter and Apollo photography

NASA Technical Reports Server (NTRS)

Gold, T.

1980-01-01

Certain classes of surface features in Lunar Orbiter and Apollo Panoramic Photographs are identifed and possible correlations between the occurrence of these features and their geographical location on the Moon are studied. Whether evidence of erosion and transport processes not encountered on Earth exists is investigated using the lunar photographs. The variety and intensity of transport processes on the Moon resulting from exposure to plasmas is discussed.

Sparsity Aware Adaptive Radar Sensor Imaging in Complex Scattering Environments

DTIC Science & Technology

2015-06-15

while meeting the requirement on the peak to average power ratio. Third, we study impact of waveform encoding on nonlinear electromagnetic tomographic...Enyue Lu. Time Domain Electromagnetic Tomography Using Propagation and Backpropagation Method, IEEE International Conference on Image Processing...Received Paper 3.00 4.00 Yuanwei Jin, Chengdon Dong, Enyue Lu. Waveform Encoding for Nonlinear Electromagnetic Tomographic Imaging, IEEE Global

Research on Radiation Characteristic of Plasma Antenna through FDTD Method

PubMed Central

Zhou, Jianming; Fang, Jingjing; Lu, Qiuyuan; Liu, Fan

2014-01-01

The radiation characteristic of plasma antenna is investigated by using the finite-difference time-domain (FDTD) approach in this paper. Through using FDTD method, we study the propagation of electromagnetic wave in free space in stretched coordinate. And the iterative equations of Maxwell equation are derived. In order to validate the correctness of this method, we simulate the process of electromagnetic wave propagating in free space. Results show that electromagnetic wave spreads out around the signal source and can be absorbed by the perfectly matched layer (PML). Otherwise, we study the propagation of electromagnetic wave in plasma by using the Boltzmann-Maxwell theory. In order to verify this theory, the whole process of electromagnetic wave propagating in plasma under one-dimension case is simulated. Results show that Boltzmann-Maxwell theory can be used to explain the phenomenon of electromagnetic wave propagating in plasma. Finally, the two-dimensional simulation model of plasma antenna is established under the cylindrical coordinate. And the near-field and far-field radiation pattern of plasma antenna are obtained. The experiments show that the variation of electron density can introduce the change of radiation characteristic. PMID:25114961

Experimental research of the influence of the strength of ore samples on the parameters of an electromagnetic signal during acoustic excitation in the process of uniaxial compression

NASA Astrophysics Data System (ADS)

Yavorovich, L. V.; Bespal`ko, A. A.; Fedotov, P. I.

2018-01-01

Parameters of electromagnetic responses (EMRe) generated during uniaxial compression of rock samples under excitation by deterministic acoustic pulses are presented and discussed. Such physical modeling in the laboratory allows to reveal the main regularities of electromagnetic signals (EMS) generation in rock massive. The influence of the samples mechanical properties on the parameters of the EMRe excited by an acoustic signal in the process of uniaxial compression is considered. It has been established that sulfides and quartz in the rocks of the Tashtagol iron ore deposit (Western Siberia, Russia) contribute to the conversion of mechanical energy into the energy of the electromagnetic field, which is expressed in an increase in the EMS amplitude. The decrease in the EMS amplitude when the stress-strain state of the sample changes during the uniaxial compression is observed when the amount of conductive magnetite contained in the rock is increased. The obtained results are important for the physical substantiation of testing methods and monitoring of changes in the stress-strain state of the rock massive by the parameters of electromagnetic signals and the characteristics of electromagnetic emission.

Erosion of cohesive soil layers above underground conduits

NASA Astrophysics Data System (ADS)

Luu, Li-Hua; Philippe, Pierre; Noury, Gildas; Perrin, Jérôme; Brivois, Olivier

2017-06-01

Using a recently developed 2D numerical modelling that combines Discrete Element (DEM) and Lattice Boltzmann methods (LBM), we simulate the destabilisation by an hydraulic gradient of a cohesive granular soil clogging the top of an underground conduit. We aim to perform a multi-scale study that relates the grain scale behavior to the macroscopic erosion process. In particular, we study the influence of the flow conditions and the inter-particle contact forces intensity on the erosion kinetic.

Quaternary bedrock erosion and landscape evolution in the Sør Rondane Mountains, East Antarctica: Reevaluating rates and processes

NASA Astrophysics Data System (ADS)

Matsuoka, Norikazu; Thomachot, Céline E.; Oguchi, Chiaki T.; Hatta, Tamao; Abe, Masahiro; Matsuzaki, Hiroyuki

2006-11-01

Rates and processes of rock weathering, soil formation, and mountain erosion during the Quaternary were evaluated in an inland Antarctic cold desert. The fieldwork involved investigations of weathering features and soil profiles for different stages after deglaciation. Laboratory analyses addressed chemistry of rock coatings and soils, as well as 10Be and 26Al exposure ages of the bedrock. Less resistant gneiss bedrock exposed over 1 Ma shows stone pavements underlain by in situ produced silty soils thinner than 40 cm and rich in sulfates, which reflect the active layer thickness, the absence of cryoturbation, and the predominance of salt weathering. During the same exposure period, more resistant granite bedrock has undergone long-lasting cavernous weathering that produces rootless mushroom-like boulders with a strongly Fe-oxidized coating. The red coating protects the upper surface from weathering while very slow microcracking progresses by the growth of sulfates. Geomorphological evidence and cosmogenic exposure ages combine to provide contrasting average erosion rates. No erosion during the Quaternary is suggested by a striated roche moutonnée exposed more than 2 Ma ago. Differential erosion between granite and gneiss suggests a significant lowering rate of desert pavements in excess of 10 m Ma - 1 . The landscape has been (on the whole) stable, but the erosion rate varies spatially according to microclimate, geology, and surface composition.

Ultrasonic cavitation erosion of 316L steel weld joint in liquid Pb-Bi eutectic alloy at 550°C.

PubMed

Lei, Yucheng; Chang, Hongxia; Guo, Xiaokai; Li, Tianqing; Xiao, Longren

2017-11-01

Liquid lead-bismuth eutectic alloy (LBE) is applied in the Accelerator Driven transmutation System (ADS) as the high-power spallation neutron targets and coolant. A 19.2kHz ultrasonic device was deployed in liquid LBE at 550°C to induce short and long period cavitation erosion damage on the surface of weld joint, SEM and Atomic force microscopy (AFM) were used to map out the surface properties, and Energy Dispersive Spectrometer (EDS) was applied to the qualitative and quantitative analysis of elements in the micro region of the surface. The erosion mechanism for how the cavitation erosion evolved by studying the element changes, their morphology evolution, the surface hardness and the roughness evolution, was proposed. The results showed that the pits, caters and cracks appeared gradually on the erode surface after a period of cavitation. The surface roughness increased along with exposure time. Work hardening by the bubbles impact in the incubation stage strengthened the cavitation resistance efficiently. The dissolution and oxidation corrosion and cavitation erosion that simultaneously happened in liquid LBE accelerated corrosion-erosion process, and these two processes combined to cause more serious damage on the material surface. Contrast to the performance of weld metal, base metal exhibited a much better cavitation resistance. Copyright © 2017. Published by Elsevier B.V.

A simplified close range photogrammetry method for soil erosion assessment

USDA-ARS?s Scientific Manuscript database

With the increased affordability of consumer grade cameras and the development of powerful image processing software, digital photogrammetry offers a competitive advantage as a tool for soil erosion estimation compared to other technologies. One bottleneck of digital photogrammetry is its dependency...

Evaluation of erosion control blanket properties and test criteria for specification and design : final report.

DOT National Transportation Integrated Search

2016-07-01

A research project to investigate the product approval, design process, and ongoing product evaluation of erosion control blankets : (ECBs) for the Missouri Department of Transportation (MoDOT) was conducted. An overview of federal and state environm...

Vegetation in drylands: Effects on wind flow and aeolian sediment transport

USDA-ARS?s Scientific Manuscript database

Drylands are characterised by patchy vegetation, erodible surfaces and erosive aeolian processes. Empirical and modelling studies have shown that vegetation elements provide drag on the overlying airflow, thus affecting wind velocity profiles and altering erosive dynamics on desert surfaces. However...

Relationship between the erosion properties of soils and other parameters

USDA-ARS?s Scientific Manuscript database

Soil parameters are essential for erosion process prediction and ultimately improved model development, especially as they relate to dam and levee failure. Soil parameters including soil texture and structure, soil classification, soil compaction, moisture content, and degree of saturation can play...

A pan-European quantitative assessment of soil loss by wind

NASA Astrophysics Data System (ADS)

Borrelli, Pasqualle; Lugato, Emanuele; Panagos, Panos

2016-04-01

Soil erosion by wind is a serious environmental problem often low perceived but resulting in severe soil degradation forms. On the long-term a considerable part of topsoil - rich in nutrient and organic matters - could be removed compromising the agricultural productivity and inducing an increased use of fertilizers. Field scale studies and observations proven that wind erosion is a serious problem in many European sites. The state-of-the-art suggests a scenario where wind erosion locally affects the temperate climate areas of the northern European countries, as well as the semi-arid areas of the Mediterranean region. However, observations, field measurements and modelling assessments are extremely limited and unequally distributed across Europe. It implies a lack of knowledge about where and when wind erosion occurs, limiting policy actions aimed at mitigating land degradation. To gain a better understanding about soil degradation process, the Soil Resource Assessment working group of the Joint Research Centre carried out the first pan-European assessments of wind-erodible fraction of soil (EF) (Geoderma, 232, 471-478, 2014) and land susceptibility to wind erosion (Land Degradation & Development, DOI: 10.1002/ldr.2318). Today's challenge is to integrate the insights archived by these pan-European assessments, local experiments and field-scale models into a new generation of regional-scale wind erosion models. A GIS version of the Revised Wind Erosion Equation (RWEQ) was developed with the aim to i) move a step forward into the aforementioned challenges, and ii) evaluate the soil loss potential due to wind erosion in the agricoltural land of the EU. The model scheme was designed to describe daily soil loss potential, combining spatiotemporal conditions of soil erodibility, crust factor, soil moisture content, vegetation coverage and wind erosivity at 1 km2 resolution. The average soil loss predicted by GIS-RWEQ in the EU arable land ranges from 0 to 39.9 Mg ha-1 yr-1, with a mean value of 0.53 Mg ha-1 yr-1. A cross-country analysis shows highest mean annual soil loss values in Denmark (3 Mg ha-1 yr-1), the Netherland (2.6 Mg ha-1 yr-1), Bulgaria (1.8 Mg ha-1 yr-1) and to a lesser extent in the United Kingdom (1 Mg ha-1 yr-1) and Romania (0.95 Mg ha-1 yr-1). The cross-validation results provides encouraging outcomes in line with the local measurements reported by academic literature. Novel insights into the spatiotemporal dynamics of wind erosion processes have been achieved, providing knowledge and a tool to gain a more comprehensive understanding of wind erosion processes in Europe.

Simulating CRN derived erosion rates in a transient Andean catchment using the TTLEM model

NASA Astrophysics Data System (ADS)

Campforts, Benjamin; Vanacker, Veerle; Herman, Frédéric; Schwanghart, Wolfgang; Tenrorio Poma, Gustavo; Govers, Gerard

2017-04-01

Assessing the impact of mountain building and erosion on the earth surface is key to reconstruct and predict terrestrial landscape evolution. Landscape evolution models (LEMs) are an essential tool in this research effort as they allow to integrate our growing understanding of physical processes governing erosion and transport of mass across the surface. The recent development of several LEMs opens up new areas of research in landscape evolution. Here, we want to seize this opportunity by answering a fundamental research question: does a model designed to simulate landscape evolution over geological timescales allows to simulate spatially varying erosion rates at a millennial timescale? We selected the highly transient Paute catchment in the Southeastern Ecuadorian Andes as a study area. We found that our model (TTLEM) is capable to better explain the spatial patterns of ca. 30 Cosmogenic Radio Nuclide (CRN) derived catchment wide erosion rates in comparison to a classical, statistical approach. Thus, the use of process-based landscape evolution models may not only be of great help to understand long-term landscape evolution but also in understanding spatial and temporal variations in sediment fluxes at the millennial time scale.

The evolution of concepts for soil erosion modelling

NASA Astrophysics Data System (ADS)

Kirkby, Mike

2013-04-01

From the earliest models for soil erosion, based on power laws relating sediment discharge or yield to slope length and gradient, the development of the Universal Soil Loss Equation was a natural step, although one that has long continued to hinder the development of better perceptual models for erosion processes. Key stumbling blocks have been: 1. The failure to go through runoff generation as a key intermediary 2. The failure to separate hydrological and strength parameters of the soil 3. The failure to treat sediment transport along a slope as a routing problem 4. The failure to analyse the nature of the dependence on vegetation Key advances have been in these directions (among others) 1. Improved understanding of the hydrological processes (e.g. infiltration and runoff, sediment entrainment) leading to KINEROS, LISEM,WEPP, PESERA 2. Recognition of selective sediment transport (e.g. transport- or supply-limited removal, grain travel distances) leading e.g. to MAHLERAN 3. Development of models adapted to particular time/space scales Some major remaining problems 1. Failure to integrate geomorphological and agronomic approaches 2. Tillage erosion - Is erosion loss of sediment or lowering of centre of mass? 3. Dynamic change during an event, as rills etc form.

Electromagnetic Dissociation of Uranium in Heavy Ion Collisions at 120 Mev/a

NASA Astrophysics Data System (ADS)

Justice, Marvin Lealon

The heavy-ion induced electromagnetic dissociation (EMD) of a 120 MeV/A ^{238}U beam incident on five targets (^9Be, ^{27}Al, ^ {nat}Cu, ^{nat} Ag, and ^{nat}U) has been studied experimentally. Electromagnetic dissociation at this beam energy is essentially a two step process involving the excitation of a giant resonance followed by particle decay. At 120 MeV/A there is predicted to be a significant contribution (~25%) of the giant quadrupole resonance to the EMD cross sections. The specific exit channel which was looked at was projectile fission. The two fission fragments were detected in coincidence by an array of solid-state DeltaE-E detectors, allowing the charges of the fragments to be determined to within +/- .5 units. The events were sorted on the basis of the sums of the fragments' charges, acceptance corrections were applied, and total cross sections for the most peripheral events (i.e. those leading to charge sums of approximately 92) were determined. Electromagnetic fission at the beam energy of this experiment always leads to a true charge sum of 92. Due to the imperfect resolution of the detectors, charge sums of 91 and 93 were included in order to account for all of the electromagnetic fission events. The experimentally observed cross sections are due to nuclear interaction processes as well as electromagnetic processes. Under the conditions of this experiment, the cross sections for the beryllium target are almost entirely due to nuclear processes. The nuclear cross sections for the other four targets were determined by extrapolation from the beryllium data using a geometrical scaling model. After subtraction of the nuclear cross sections, the resulting electromagnetic cross sections are compared to theoretical calculations based on the equivalent photon approximation. Systematic uncertainties associated with the normalization of the data make quantitative comparisons with theory difficult, however. The systematic uncertainties are discussed and suggestions for improving the experiment are given.

Electromagnetic cellular interactions.

PubMed

Cifra, Michal; Fields, Jeremy Z; Farhadi, Ashkan

2011-05-01

Chemical and electrical interaction within and between cells is well established. Just the opposite is true about cellular interactions via other physical fields. The most probable candidate for an other form of cellular interaction is the electromagnetic field. We review theories and experiments on how cells can generate and detect electromagnetic fields generally, and if the cell-generated electromagnetic field can mediate cellular interactions. We do not limit here ourselves to specialized electro-excitable cells. Rather we describe physical processes that are of a more general nature and probably present in almost every type of living cell. The spectral range included is broad; from kHz to the visible part of the electromagnetic spectrum. We show that there is a rather large number of theories on how cells can generate and detect electromagnetic fields and discuss experimental evidence on electromagnetic cellular interactions in the modern scientific literature. Although small, it is continuously accumulating. Copyright © 2010 Elsevier Ltd. All rights reserved.

Detection of seasonal erosion processes at the scale of an elementary black marl gully from time series of Hi-Resolution DEMs

NASA Astrophysics Data System (ADS)

Bechet, J.; Duc, J.; Loye, A.; Jaboyedoff, M.; Mathys, N.; Malet, J.-P.; Klotz, S.; Le Bouteiller, C.; Rudaz, B.; Travelletti, J.

2015-12-01

The Roubine catchment located in the experimental research station of Draix-Bléone (south French Alps) is situated in Callovo-Oxfordian black marls, a lithology particularly prone to weathering processes. Since 30 years, this small watershed (0.13 ha) has been monitored for analysing hillslope erosion processes at the scale of elementary gullies. Since 2007, a monitoring of surface changes has been performed by comparing of high-resolution digital elevation models (HR-DEMs) produced from Terrestrial Laser Scanner (TLS). The objectives are (1) to detect and (2) to quantify the sediment production and the evolution of the gully morphology in terms of sediment availability/transport capacity vs. rainfall and runoff generation. Time series of TLS observations have been acquired periodically based on the seasonal runoff activity with a very high point cloud density ensuring a resolution of the DEM at the centimetre scale. The topographic changes over a time span of 4 years are analysed. Quantitative analyses of the seasonal erosion activity and of the sediment fluxes contributing to the recharge of tributary gullies and rills are presented. According to the transport capacity generated by runoff, loose regolith soil sources are eroded at different periods of the year. These are forming transient deposits in the main reach when routed downstream, evolving from a transport-limited to a supply-limited regime through the year. The monitoring allows a better understanding of the seasonal pattern of erosion processes for black marls badland-type slopes and illustrates the mode of sediment production and the temporal storage/entrainment in similar slopes. The observed surface changes caused by erosion (ablation/deposition) are quantified for the complete TLS time-series, and sediment budget maps are presented for each season. Comparisons of the TLS sediment budget map with the in situ sediment monitoring (limnigraph and sedigraph) in the stream are discussed. Intense and long duration rainfall events are the triggering factor of the major erosive events.

Quantitative Relationships Linking Rock Strength to Channel Morphology: A Case Study in Central Arizona

NASA Astrophysics Data System (ADS)

Larimer, J. E.; Yanites, B.

2016-12-01

River morphology is a consequence of the erosive forces acting on the channel boundary and the resisting forces that limit erosion. For bedrock rivers, the erosive forces are generated by the stresses exerted by impacting sediment and flowing water, while the resisting forces are controlled by the internal strength regime of the local rock. We investigate the susceptibility of different rock types to different erosional processes (i.e. abrasion and plucking) and how changes in channel morphology reflect rock strength properties across lithologic boundaries. The bedrock rivers in the Prescott National Forest, AZ flow over a number of rock types with variable strength including sedimentary, igneous, and metamorphic lithologies providing a natural experiment to quantify the influence of rock strength on channel morphology. We collected bedrock samples and channel surveys from 12 different rock types. Rock-strength and rock-mass properties include compressive strength, tensile strength, fatigue strength, decimeter scale P-wave velocity (varies by 8-fold), Schmidt rebound value, fracture spacing, fracture aperture, and slake durability (as a proxy for weathering susceptibility. Morphological measurements include channel width, channel steepness (varies by 10-fold), and grain size distribution. To distinguish between the major mechanisms of erosion we measure bedrock surface roughness factor at the centimeter scale. Preliminary results show that channel steepness (ksn) increases with P-wave velocity while normalized channel width (kwn) decreases with P-wave velocity. We use these data to quantify scaling relationships of channel geometry with rock strength properties. We consider the results in the context of the driving mechanistic process to develop new quantitative understandings of how rock strength properties influence the efficiency of erosion processes and how rock strength is reflected in river morphology. By comparing the results among different rock types in a landscape subject to spatially consistent tectonic and climatic influence, our work seeks to advance process-based river erosion models through field and laboratory measurements.

Monitoring channel head erosion processes in response to an artificially induced abrupt base level change using time-lapse photography

NASA Astrophysics Data System (ADS)

Nichols, M. H.; Nearing, M.; Hernandez, M.; Polyakov, V. O.

2016-07-01

Gullies that terminate at a vertical-wall are ubiquitous throughout arid and semiarid regions. Multi-year assessments of gully evolution and headcut advance are typically accomplished using traditional ground surveys and aerial photographs, with much recent research focused on integrating data collected at very high spatial resolutions using new techniques such as aerial surveys with blimps or kites and ground surveys with LiDar scanners. However, knowledge of specific processes that drive headcut advance is limited due to inadequate observation and documentation of flash floods and subsequent erosion that can occur at temporal resolutions not captured through repeat surveys. This paper presents a method for using very-high temporal resolution ground-based time-lapse photography to capture short-duration flash floods and gully head evolution in response. In 2004, a base level controlling concrete weir was removed from the outlet of a 1.29 ha semiarid headwater drainage on the Walnut Gulch Experimental Watershed in southeastern Arizona, USA. During the ten year period from 2004 to 2014 the headcut migrated upchannel a total of 14.5 m reducing the contributing area at the headwall by 9.5%. Beginning in July 2012, time-lapse photography was employed to observe event scale channel evolution dynamics. The most frequent erosion processes observed during three seasons of time-lapse photography were plunge pool erosion and mass wasting through sidewall or channel headwall slumping that occurred during summer months. Geomorphic change during the ten year period was dominated by a single piping event in August 2014 that advanced the channel head 7.4 m (51% of the overall advance) and removed 11.3 m3 of sediment. High temporal resolution time-lapse photography was critical for identifying subsurface erosion processes, in the absence of time-lapse images piping would not have been identified as an erosion mechanism responsible for advancing the gully headwall at this site.

Modeling the Emergent Impacts of Harvesting Acadian Forests over 100+ Years

NASA Astrophysics Data System (ADS)

Luus, K. A.; Plug, L. J.

2007-12-01

Harvesting strategies and policies for Acadian forest in Nova Scotia, Canada, presently are set using Decision Support Models (DSMs) that aim to maximize the long-term (>100y) value of forests through decisions implemented over short time horizons (5-80 years). However, DSMs typically are aspatial, lack ecological processes and do not treat erosion, so the long-term (>100y) emergent impacts of the prescribed forestry decisions on erosion and vegetation in Acadian forests remain poorly known. To better understand these impacts, we created an equation-based model that simulates the evolution of a ≥4 km2 forest in time steps of 1 y and at a spatial resolution of 3 m2, the footprint of a single mature tree. The model combines 1) ecological processes of recruitment, competition, and mortality; 2) geomorphic processes of hillslope erosion; 3) anthropic processes of tree harvesting, replanting, and road construction under constraints imposed by regulations and cost/benefit ratio. The model uses digital elevation models, parameters (where available), and calibration (where measurements are not available) for conditions presently found in central Cape Breton, Nova Scotia. The model is unique because it 1) deals with the impacts of harvesting on an Acadian forest; and 2) vegetation and erosion are coupled. The model was tested by comparing the species-specific biomass of long-term (40 y) forest plot data to simulated results. At the spatial scale of individual 1 ha plots, model predictions presently account for approximately 50% of observed biomass changes through time, but predictions are hampered by the effects of serendipitous "random" events such as single tree windfall. Harvesting increases the cumulative erosion over 3000 years by 240% when compared to an old growth forest and significantly suppresses the growth of Balsam Fir and Sugar Maple. We discuss further tests of the model, and how it might be used to investigate the long-term sustainability of the recommendations made by DSMs and to better understand the relationship between vegetation, erosion, and forest management strategies.

Estimation of Annual Average Soil Loss, Based on Rusle Model in Kallar Watershed, Bhavani Basin, Tamil Nadu, India

NASA Astrophysics Data System (ADS)

Rahaman, S. Abdul; Aruchamy, S.; Jegankumar, R.; Ajeez, S. Abdul

2015-10-01

Soil erosion is a widespread environmental challenge faced in Kallar watershed nowadays. Erosion is defined as the movement of soil by water and wind, and it occurs in Kallar watershed under a wide range of land uses. Erosion by water can be dramatic during storm events, resulting in wash-outs and gullies. It can also be insidious, occurring as sheet and rill erosion during heavy rains. Most of the soil lost by water erosion is by the processes of sheet and rill erosion. Land degradation and subsequent soil erosion and sedimentation play a significant role in impairing water resources within sub watersheds, watersheds and basins. Using conventional methods to assess soil erosion risk is expensive and time consuming. A comprehensive methodology that integrates Remote sensing and Geographic Information Systems (GIS), coupled with the use of an empirical model (Revised Universal Soil Loss Equation- RUSLE) to assess risk, can identify and assess soil erosion potential and estimate the value of soil loss. GIS data layers including, rainfall erosivity (R), soil erodability (K), slope length and steepness (LS), cover management (C) and conservation practice (P) factors were computed to determine their effects on average annual soil loss in the study area. The final map of annual soil erosion shows a maximum soil loss of 398.58 t/ h-1/ y-1. Based on the result soil erosion was classified in to soil erosion severity map with five classes, very low, low, moderate, high and critical respectively. Further RUSLE factors has been broken into two categories, soil erosion susceptibility (A=RKLS), and soil erosion hazard (A=RKLSCP) have been computed. It is understood that functions of C and P are factors that can be controlled and thus can greatly reduce soil loss through management and conservational measures.

Rates and probable causes of freshwater tidal marsh failure, Potomac River Estuary, Northern Virginia, USA

USGS Publications Warehouse

Litwin, Ronald J.; Smoot, Joseph P.; Pavich, Milan J.; Markewich, Helaine Walsh; Oberg, Erik T.; Steury, Brent W.; Helwig, Ben; Santucci, Vincent L.; Sanders, Geoffrey

2013-01-01

Dyke Marsh, a distal tidal marsh along the Potomac River estuary, is diminishing rapidly in areal extent. This study documents Dyke Marsh erosion rates from the early-1860s to the present during pre-mining, mining, and post-mining phases. From the late-1930s to the mid-1970s, Dyke Marsh and the adjacent shallow riverbottom were mined for gravel, resulting in a ~55 % initial loss of area. Marsh loss continued during the post-mining phase (1976–2012). Causes of post-mining loss were unknown, but were thought to include Potomac River flooding. Post-mining areal-erosion rates increased from 0.138 ha yr−1 (~0.37 ac yr−1) to 0.516 ha yr−1(~1.67 ac yr−1), and shoreline-erosion rates increased from 0.76 m yr−1 (~2.5 ft yr−1) to 2.60 m yr−1 (~8.5 ft yr−1). Results suggest the accelerating post-mining erosion reflects a process-driven feedback loop, enabled by the marsh's severely-altered geomorphic and hydrologic baseline system; the primary post-mining degradation process is wave-induced erosion from northbound cyclonic storms. Dyke Marsh erosion rates are now comparable to, or exceed, rates for proximal coastal marshes in the same region. Persistent and accelerated erosion of marshland long after cessation of mining illustrates the long-term, and potentially devastating, effects that temporally-restricted, anthropogenic destabilization can have on estuarine marsh systems.

The National Wind Erosion Research Network: Building a standardized long-term data resource for aeolian research, modeling and land management

USGS Publications Warehouse

Webb, Nicholas P.; Herrick, Jeffrey E.; Van Zee, Justin W; Courtright, Ericha M; Hugenholtz, Ted M; Zobeck, Ted M; Okin, Gregory S.; Barchyn, Thomas E; Billings, Benjamin J; Boyd, Robert A.; Clingan, Scott D; Cooper, Brad F; Duniway, Michael C.; Derner, Justin D.; Fox, Fred A; Havstad, Kris M.; Heilman, Philip; LaPlante, Valerie; Ludwig, Noel A; Metz, Loretta J; Nearing, Mark A; Norfleet, M Lee; Pierson, Frederick B; Sanderson, Matt A; Sharrat, Brenton S; Steiner, Jean L; Tatarko, John; Tedela, Negussie H; Todelo, David; Unnasch, Robert S; Van Pelt, R Scott; Wagner, Larry

2016-01-01

The National Wind Erosion Research Network was established in 2014 as a collaborative effort led by the United States Department of Agriculture’s Agricultural Research Service and Natural Resources Conservation Service, and the United States Department of the Interior’s Bureau of Land Management, to address the need for a long-term research program to meet critical challenges in wind erosion research and management in the United States. The Network has three aims: (1) provide data to support understanding of basic aeolian processes across land use types, land cover types, and management practices, (2) support development and application of models to assess wind erosion and dust emission and their impacts on human and environmental systems, and (3) encourage collaboration among the aeolian research community and resource managers for the transfer of wind erosion technologies. The Network currently consists of thirteen intensively instrumented sites providing measurements of aeolian sediment transport rates, meteorological conditions, and soil and vegetation properties that influence wind erosion. Network sites are located across rangelands, croplands, and deserts of the western US. In support of Network activities, http://winderosionnetwork.org was developed as a portal for information about the Network, providing site descriptions, measurement protocols, and data visualization tools to facilitate collaboration with scientists and managers interested in the Network and accessing Network products. The Network provides a mechanism for engaging national and international partners in a wind erosion research program that addresses the need for improved understanding and prediction of aeolian processes across complex and diverse land use types and management practices.

Processing Waveform-Based NDE

NASA Technical Reports Server (NTRS)

Roth, Donald J (Inventor)

2011-01-01

A computer implemented process for simultaneously measuring the velocity of terahertz electromagnetic radiation in a dielectric material sample without prior knowledge of the thickness of the sample and for measuring the thickness of a material sample using terahertz electromagnetic radiation in a material sample without prior knowledge of the velocity of the terahertz electromagnetic radiation in the sample is disclosed and claimed. Utilizing interactive software the process evaluates, in a plurality of locations, the sample for microstructural variations and for thickness variations and maps the microstructural and thickness variations by location. A thin sheet of dielectric material may be used on top of the sample to create a dielectric mismatch. The approximate focal point of the radiation source (transceiver) is initially determined for good measurements.

The Effect of Grain Refinement on Solid Particle Erosion of Grade 5 Ti Alloy

NASA Astrophysics Data System (ADS)

Kazarinov, N. A.; Evstifeev, A. D.; Petrov, Y. V.; Atroshenko, S. A.; Valiev, R. R.

2018-04-01

In this work, the results on solid particle erosion of an ultrafine-grained Grade 5 titanium alloy, which was produced using high-pressure torsion (HPT) technique, are presented. In order to assess influence of the HPT treatment on material's behavior in erosive conditions, special experimental procedures were developed. The ultrafine-grained (UFG) alloy was tested alongside with a conventional coarse-grained (CG) Grade 5 titanium alloy in equal conditions. The experiments were conducted in a small-scale wind tunnel with corundum particles as an abrasive material. Both particle dimensions and particle velocities were varied in course of the experiments. Erosion resistance of the samples was evaluated in two ways—mass reduction measurements with subsequent gravimetric erosion rate calculations and investigation of samples' surface roughness after erosion tests. The UFG titanium alloy demonstrated considerable improvement of static mechanical properties (ultimate tensile strength, microhardness), whereas its CG counterpart appeared to be slightly more resistant to solid particle erosion, which might indicate the drop of dynamic strength properties for the HPT-processed material.

Methodological considerations concerning the development of oral dental erosion indexes: literature survey, validity and reliability

PubMed Central

Kutschmann, Marcus; Bardehle, Doris

2008-01-01

Within the context of preventing non-communicable diseases, the World Health Report (2002) and the WHO Global Oral Health Program (2003) put forward a new strategy of disease prevention and health promotion. Greater emphasis is placed on developing global policies in oral health promotion and oral disease prevention. The Decayed, Missing, Filled Teeth (DMFT) index does not meet new challenges in the field of oral health. Dental erosion seems to be a growing problem, and in some countries, an increase in erosion of teeth is associated with an increase in the consumption of beverages containing acids. Therefore, within a revision of the WHO Oral Health Surveys Basic Methods, new oral disease patterns, e.g. dental erosion, have to be taken into account. Within the last 20 years, many studies on dental erosion have been carried out and published. There has been a rapid growth in the number of indexes quantifying dental erosion process in different age groups. However, these indexes are not comparable. This article discusses quality criteria which an index intended for assessing tooth erosion should possess. PMID:18228060

Methods for monitoring erosion using optical coherence tomography

NASA Astrophysics Data System (ADS)

Chan, Kenneth H.; Chan, Andrew C.; Darling, Cynthia L.; Fried, Daniel

Since optical coherence tomography is well suited for measuring small dimensional changes on tooth surfaces it has great potential for monitoring tooth erosion. The purpose of this study was to explore different approaches for monitoring the erosion of enamel. Application of an acid resistant varnish to protect the tooth surface from erosion has proven effective for providing a reference surface for in vitro studies but has limited potential for in vivo studies. Two approaches which can potentially be used in vivo were investigated. The first approach is to measure the remaining enamel thickness, namely the distance from the tooth surface to the dentinal-enamel junction (DEJ). The second more novel approach is to irradiate the surface with a carbon dioxide laser to create a reference layer which resists erosion. Measuring the remaining enamel thickness proved challenging since the surface roughening and subsurface demineralization that commonly occurs during the erosion process can prevent resolution of the underlying DEJ. The areas irradiated by the laser manifested lower rates of erosion compared to the non-irradiated areas and this method appears promising but it is highly dependent on the severity of the acid challenge.

Soil erosion in mountainous areas: how far can we go?

NASA Astrophysics Data System (ADS)

Egli, Markus

2017-04-01

Erosion is the counter part of soil formation, is a natural process and cannot be completely impeded. With respect to soil protection, the term of tolerable soil erosion, having several definitions, has been created. Tolerable erosion is often equalled to soil formation or production. It is therefore crucial that we know the rates of soil formation when discussing sustainability of soil use and management. Natural rates of soil formation or production are determined by mineral weathering or transformation of parent material into soil, dust deposition and organic matter incorporation. In mountain areas where soil depth is a main limiting factor for soil productivity, the use and management of soils must consider how to preserve them from excessive depth loss and consequent degradation of their physical, chemical and biological properties. Even under natural conditions, landscape surfaces and soils are known to evolve in complex, non-linear ways over time. As a result, soil production and erosion change substantially with time. The fact that soil erosion and soil production processes are discontinuous over time is an aspect that is in most cases completely neglected. To conserve a given situation, tolerable values should take these dynamics into account. Measurements of long and short-term physical erosion rates, total denudation, weathering rates and soil production have recently become much more widely available through cosmogenic and fallout nuclide techniques. In addition to this, soil chronosequences deliver a precious insight into the temporal aspect of soil formation and production. Examples from mountainous and alpine areas demonstrate that soil production rates strongly vary as a function of time (with young soils and eroded surfaces having distinctly higher rates than old soils). Extensive erosion promotes rejuvenation of the surface and, therefore, accelerates chemical weathering and soil production - the resulting soil thickness will however be shallow. The comparison of soil production and erosion rates indicates that the present-day management of grassland soils in several alpine and mountain regions will lead in the long-term to very shallow soils (showing the characteristics of young soils). Shallow soils go along with high 'tolerable' erosion rates. It is, however, strongly doubtful whether this matches the deeper sense of sustainability.

Reactive Molecular Dynamics Simulations on the Disintegration of PVDF, FP-POSS, and Their Composite during Atomic Oxygen Impact.

PubMed

Zeng, Fanlin; Peng, Chao; Liu, Yizhi; Qu, Jianmin

2015-07-30

Poly(vinylidene fluoride) (PVDF) is a kind of important piezoelectric polymer used in spacecraft industry. But the atomic oxygen (AO) is the most abundant element in the low Earth orbit (LEO) environment. AO collision degradation is an important issue in the application of PVDF on spacecrafts. To investigate the erosion behaviors of PVDF during AO impacts and how to improve the stability of PVDF against AO impacts, the temperature evolution, mass loss, and erosion yields of neat PVDF, neat polyhedral oligomeric silsesquioxanes compound (3,3,3-trifluoropropyl)8Si8O12 (FP-POSS) and the PVDF/FP-POSS composite under AO impacts, as well as some key disintegrated structures and separated chemical compositions, were researched using the molecular dynamics (MD) simulations and the reactive ReaxFF force field. The simulation erosion yield result of PVDF is very close to the experiment results, which shows our simulations are reliable. The results of the temperature evolution, mass loss, and erosion yield of three materials show that the antierosion performance of PVDF is not outstanding. However, incorporating FP-POSS into PVDF matrix enhances the stability of PVDF against AO impact greatly and reduces the temperature rise, mass loss, and the erosion yield of PVDF rapidly. A detailed analysis on the flight chemical compositions and key snapshots of the structures reveals that the erosion process on PVDF and PVDF/FP-POSS is continuous and should be derived from the same PVDF matrix in two materials. In contrast, the erosion process on FP-POSS is stepped. The erosion will not take place until the number of AO reaches a specific value. There is a barrier for the erosion of high-energy AO because of the stable cagelike Si-O frame in FP-POSS molecules. This should be chiefly responsible for the high stability of FP-POSS and the reinforcement mechanism of FP-POSS on PVDF against AO impacts. This work is helpful for people to understand the erosion details of PVDF and POSS and provides valuable information to design effective protective structure for PVDF against AO impacts in LEO environment.

The age of vines as a controlling factor of soil erosion processes in Mediterranean vineyards.

PubMed

Rodrigo-Comino, Jesús; Brevik, Eric C; Cerdà, Artemi

2018-03-01

Vineyards incur the highest soil and water losses among all Mediterranean agricultural fields. The state-of-the-art shows that soil erosion in vineyards has been primarily surveyed with topographical methods, soil erosion plots and rainfall simulations, but these techniques do not typically assess temporal changes in soil erosion. When vines are planted they are about 30cm high×1cm diameter without leaves, the root system varies from 2 to over 40cm depth, and sometimes the lack of care used during transplanting can result in a field with highly erodible bare soils. This means that the time since vine plantation plays a key role in soil erosion rates, but very little attention has been paid to this by the scientific community. Thus, the main goal of this research was to estimate soil losses and assess soil erosion processes in two paired vineyard plantations of different ages. To achieve this goal, the improved stock unearthing method (ISUM) was applied to vineyards on colluvial parent materials with similar soil properties, topographical characteristics and land managements in the Les Alcusses Valley, southwestern Valencia province, Spain. Our findings suggested that the old vineyards showed lower erosion rates (-1.61Mgha -1 yr -1 ) than those that were recently planted (-8.16Mgha -1 yr -1 ). This is because of the damage that the plantation of the vines causes to soil. Tillage after planting (4 times per year) resulted in changes in the inter-row and row morphology, promoting the development of a ridge underneath the vines that disconnected the inter-rows and reduced soil losses with time. After the second year and until the 25th year after plantation, soil erosion was approximately 1Mgha -1 y -1 , which means that most of the erosion took place during the first two years after the plantation. Soil conservation strategies should be applied immediately after the plantation works to allow sustainable grape production. That is when soil erosion most needs to be controlled. Copyright © 2017 Elsevier B.V. All rights reserved.

Anthropogenic Increase Of Soil Erosion In The Gangetic Plain Revealed By Geochemical Budget Of Erosion

NASA Astrophysics Data System (ADS)

Galy, V.; France-Lanord, C.; Galy, A.; Gaillardet, J.

2007-12-01

Tectonic and climatic factors are the key natural variables controlling the erosion through complex interactions. Nonetheless, over the last few hundred years, human activity also exerts a dominant control in response to extensive land use. The geochemical budget of erosion allows the balance between the different erosion processes to be quantified. The chemical composition of river sediment results from the chemical composition of the source rock modified by (1) weathering reactions occurring during erosion and (2) physical segregation during transport. If erosion is at steady state, the difference between the chemical composition of source rocks and that of river sediments must therefore be counterbalanced by the dissolved flux. However, climatic variations or anthropic impact can induce changes in the erosion distribution in a given basin resulting in non steady state erosion. Using a mass balance approach, the comparison of detailed geochemical data on river sediments with the current flux of dissolved elements allows the steady state hypothesis to be tested. In this study, we present a geochemical budget of weathering for the Ganga basin, one of the most densely populated basin in the world, based on detailed sampling of Himalayan rivers and of the Ganga in the delta. Sampling includes depth profile in the river, to assess the variability generated by transport processes. Himalayan river sediments are described by the dilution of an aluminous component (micas + clays + feldspars) by quartz. Ganga sediments on the other hand correspond to the mixing of bedload, similar to coarse Himalayan sediments, with an aluminous component highly depleted in alkaline elements. Compared with the dissolved flux, the depletion of alkaline elements in Ganga sediments shows that the alkaline weathering budget is imbalanced. This imbalance results from an overabundance of fine soil material in the Ganga sediment relative to other less weathered material directly derived from Himalaya. Based on the average composition of the suspended load and of floodplain soils, we estimate that 250x106 t/yr i.e. 5 t/ha/yr is eroded from soil surfaces of the Ganga floodplain. This enhanced soil erosion is likely triggered by intense deforestation and change in land use due to increasing human activity in the basin.

Mid-Pleistocene climate transition drives net mass loss from rapidly uplifting St. Elias Mountains, Alaska.

PubMed

Gulick, Sean P S; Jaeger, John M; Mix, Alan C; Asahi, Hirofumi; Bahlburg, Heinrich; Belanger, Christina L; Berbel, Glaucia B B; Childress, Laurel; Cowan, Ellen; Drab, Laureen; Forwick, Matthias; Fukumura, Akemi; Ge, Shulan; Gupta, Shyam; Kioka, Arata; Konno, Susumu; LeVay, Leah J; März, Christian; Matsuzaki, Kenji M; McClymont, Erin L; Moy, Chris; Müller, Juliane; Nakamura, Atsunori; Ojima, Takanori; Ribeiro, Fabiana R; Ridgway, Kenneth D; Romero, Oscar E; Slagle, Angela L; Stoner, Joseph S; St-Onge, Guillaume; Suto, Itsuki; Walczak, Maureen D; Worthington, Lindsay L; Bailey, Ian; Enkelmann, Eva; Reece, Robert; Swartz, John M

2015-12-08

Erosion, sediment production, and routing on a tectonically active continental margin reflect both tectonic and climatic processes; partitioning the relative importance of these processes remains controversial. Gulf of Alaska contains a preserved sedimentary record of the Yakutat Terrane collision with North America. Because tectonic convergence in the coastal St. Elias orogen has been roughly constant for 6 My, variations in its eroded sediments preserved in the offshore Surveyor Fan constrain a budget of tectonic material influx, erosion, and sediment output. Seismically imaged sediment volumes calibrated with chronologies derived from Integrated Ocean Drilling Program boreholes show that erosion accelerated in response to Northern Hemisphere glacial intensification (∼ 2.7 Ma) and that the 900-km-long Surveyor Channel inception appears to correlate with this event. However, tectonic influx exceeded integrated sediment efflux over the interval 2.8-1.2 Ma. Volumetric erosion accelerated following the onset of quasi-periodic (∼ 100-ky) glacial cycles in the mid-Pleistocene climate transition (1.2-0.7 Ma). Since then, erosion and transport of material out of the orogen has outpaced tectonic influx by 50-80%. Such a rapid net mass loss explains apparent increases in exhumation rates inferred onshore from exposure dates and mapped out-of-sequence fault patterns. The 1.2-My mass budget imbalance must relax back toward equilibrium in balance with tectonic influx over the timescale of orogenic wedge response (millions of years). The St. Elias Range provides a key example of how active orogenic systems respond to transient mass fluxes, and of the possible influence of climate-driven erosive processes that diverge from equilibrium on the million-year scale.

Small scale rainfall simulators: Challenges for a future use in soil erosion research

NASA Astrophysics Data System (ADS)

Ries, Johannes B.; Iserloh, Thomas; Seeger, Manuel

2013-04-01

Rainfall simulation on micro-plot scale is a method used worldwide to assess the generation of overland flow, soil erosion, infiltration and interrelated processes such as soil sealing, crusting, splash and redistribution of solids and solutes. The produced data are of great significance not only for the analysis of the simulated processes, but also as a source of input-data for soil erosion modelling. The reliability of the data is therefore of paramount importance, and quality management of rainfall simulation procedure a general responsibility of the rainfall simulation community. This was an accepted outcome at the "International Rainfall Simulator Workshop 2011" at Trier University. The challenges of the present and near future use of small scale rainfall simulations concern the comparability of results and scales, the quality of the data for soil erosion modelling, and further technical developments to overcome physical limitations and constraints. Regarding the high number of research questions, different fields of application, and due to the great technical creativity of researchers, a large number of different types of rainfall simulators is available. But each of the devices produces a different rainfall, leading to different kinetic energy values influencing soil surface and erosion processes. Plot sizes are also variable, as well as the experimental simulation procedures. As a consequence, differing runoff and erosion results are produced. The presentation summarises the three important aspects of rainfall simulations, following a processual order: 1. Input-factor "rain" and its calibration 2. Surface-factor "plot" and its documentation 3. Output-factors "runoff" and "sediment concentration" Finally, general considerations about the limitations and challenges for further developments and applications of rainfall simulation data are presented.

Using the raindrop size distribution to quantify the soil detachment rate at the laboratory scale

NASA Astrophysics Data System (ADS)

Jomaa, S.; Jaffrain, J.; Barry, D. A.; Berne, A.; Sander, G. C.

2010-05-01

Rainfall simulators are beneficial tools for studying soil erosion processes and sediment transport for different circumstances and scales. They are useful to better understand soil erosion mechanisms and, therefore, to develop and validate process-based erosion models. Simulators permit experimental replicates for both simple and complex configurations. The 2 m × 6 m EPFL erosion flume is equipped with a hydraulic slope control and a sprinkling system located on oscillating bars 3 m above the surface. It provides a near-uniform spatial rainfall distribution. The intensity of the precipitation can be adjusted by changing the oscillation interval. The flume is filled to a depth of 0.32 m with an agricultural loamy soil. Raindrop detachment is an important process in interrill erosion, the latter varying with the soil properties as well as the raindrop size distribution and drop velocity. Since the soil detachment varies with the kinetic energy of raindrops, an accurate characterization of drop size distribution (DSD, measured, e.g., using a laser disdrometer) can potentially support erosion calculations. Here, a laser disdrometer was used at different rainfall intensities in the EPFL flume to quantify the rainfall event in terms of number of drops, diameter and velocity. At the same time, soil particle motion was measured locally using splash cups. These cups measured the detached material rates into upslope and downslope compartments. In contrast to previously reported splash cup experiments, the cups used in this study were equipped at the top with upside-down funnels, the upper part having the same diameter as the soil sampled at the bottom. This ensured that the soil detached and captured by the device was not re-exposed to rainfall. The experimental data were used to quantify the relationship between the raindrop distribution and the splash-driven sediment transport.

Current research issues related to post-wildfire runoff and erosion processes

USGS Publications Warehouse

Moody, John A.; Shakesby, Richard A.; Robichaud, Peter R.; Cannon, Susan H.; Martin, Deborah A.

2013-01-01

Research into post-wildfire effects began in the United States more than 70 years ago and only later extended to other parts of the world. Post-wildfire responses are typically transient, episodic, variable in space and time, dependent on thresholds, and involve multiple processes measured by different methods. These characteristics tend to hinder research progress, but the large empirical knowledge base amassed in different regions of the world suggests that it should now be possible to synthesize the data and make a substantial improvement in the understanding of post-wildfire runoff and erosion response. Thus, it is important to identify and prioritize the research issues related to post-wildfire runoff and erosion. Priority research issues are the need to: (1) organize and synthesize similarities and differences in post-wildfire responses between different fire-prone regions of the world in order to determine common patterns and generalities that can explain cause and effect relations; (2) identify and quantify functional relations between metrics of fire effects and soil hydraulic properties that will better represent the dynamic and transient conditions after a wildfire; (3) determine the interaction between burned landscapes and temporally and spatially variable meso-scale precipitation, which is often the primary driver of post-wildfire runoff and erosion responses; (4) determine functional relations between precipitation, basin morphology, runoff connectivity, contributing area, surface roughness, depression storage, and soil characteristics required to predict the timing, magnitudes, and duration of floods and debris flows from ungaged burned basins; and (5) develop standard measurement methods that will ensure the collection of uniform and comparable runoff and erosion data. Resolution of these issues will help to improve conceptual and computer models of post-wildfire runoff and erosion processes.

Mid-Pleistocene climate transition drives net mass loss from rapidly uplifting St. Elias Mountains, Alaska

PubMed Central

Jaeger, John M.; Mix, Alan C.; Asahi, Hirofumi; Bahlburg, Heinrich; Belanger, Christina L.; Berbel, Glaucia B. B.; Childress, Laurel; Cowan, Ellen; Drab, Laureen; Forwick, Matthias; Fukumura, Akemi; Ge, Shulan; Gupta, Shyam; Konno, Susumu; LeVay, Leah J.; März, Christian; McClymont, Erin L.; Moy, Chris; Müller, Juliane; Nakamura, Atsunori; Ojima, Takanori; Ribeiro, Fabiana R.; Ridgway, Kenneth D.; Romero, Oscar E.; Slagle, Angela L.; Stoner, Joseph S.; St-Onge, Guillaume; Suto, Itsuki; Walczak, Maureen D.; Worthington, Lindsay L.; Bailey, Ian; Enkelmann, Eva; Reece, Robert; Swartz, John M.

2015-01-01

Erosion, sediment production, and routing on a tectonically active continental margin reflect both tectonic and climatic processes; partitioning the relative importance of these processes remains controversial. Gulf of Alaska contains a preserved sedimentary record of the Yakutat Terrane collision with North America. Because tectonic convergence in the coastal St. Elias orogen has been roughly constant for 6 My, variations in its eroded sediments preserved in the offshore Surveyor Fan constrain a budget of tectonic material influx, erosion, and sediment output. Seismically imaged sediment volumes calibrated with chronologies derived from Integrated Ocean Drilling Program boreholes show that erosion accelerated in response to Northern Hemisphere glacial intensification (∼2.7 Ma) and that the 900-km-long Surveyor Channel inception appears to correlate with this event. However, tectonic influx exceeded integrated sediment efflux over the interval 2.8–1.2 Ma. Volumetric erosion accelerated following the onset of quasi-periodic (∼100-ky) glacial cycles in the mid-Pleistocene climate transition (1.2–0.7 Ma). Since then, erosion and transport of material out of the orogen has outpaced tectonic influx by 50–80%. Such a rapid net mass loss explains apparent increases in exhumation rates inferred onshore from exposure dates and mapped out-of-sequence fault patterns. The 1.2-My mass budget imbalance must relax back toward equilibrium in balance with tectonic influx over the timescale of orogenic wedge response (millions of years). The St. Elias Range provides a key example of how active orogenic systems respond to transient mass fluxes, and of the possible influence of climate-driven erosive processes that diverge from equilibrium on the million-year scale. PMID:26598689

THE IMPACT OF HUMANS ON CONTINENTAL EROSION AND SEDIMENTATION (Invited)

NASA Astrophysics Data System (ADS)

Wilkinson, B.; McElroy, B.

2009-12-01

Tectonic uplift and erosional denudation of orogenic belts have long been the most important geologic processes that serve to shape continental surfaces, but the rate of geomorphic change resulting from these natural phenomena has now been outstripped by human activities associated with agriculture, construction, and mining. Although humans are now the most important geomorphic agent on the planet’s surface, natural and anthropogenic processes serve to modify quite different parts of the Earth landscape. In order to better understand the impact of humans on continental erosion, we have examined both long-term and short-term data on rates of sediment transfer in response to glacio-fluvial and anthropogenic processes. Phanerozoic rates of subaerial denudation inferred from preserved volumes of sedimentary rock require a mean continental erosion rate on the order of 16 meters per million years (m/My), resulting in the accumulation of about 5 giga-tons of sediment per year (Gt/y). Erosion irregularly increased over the ~542 million year span of Phanerozoic time to a Pliocene value of 81 m/My (~19 Gt/y). Current estimates of large river sediment loads are similar to this late Neogene value, and require net denudation of ice-free land surfaces at a rate of about 74 m/My (~25 Gt/y). Consideration of variation in large river sediment loads and the geomorphology of respective river basin catchments suggests that natural erosion is primarily confined to drainage headwaters; ~83% of the global river sediment flux is derived from the highest 10% of the Earth’s surface. Subaerial erosion as a result of human activity, primarily through agricultural practices, has resulted in a sharp increase in net rates of continental denudation; although less well constrained than estimates based on surviving rock volumes or current river loads, available data suggest that present farmland denudation is proceeding at a rate of about 600 m/My (~74 Gt/y), and is largely confined to lower elevations of the Earth’s land surface, primarily along passive continental margins; ~83% of cropland erosion occurs over the lower 65% of the Earth’s surface. The conspicuous disparity between natural sediment fluxes suggested by data on rock volumes and river loads (~25 Gt/y) and anthropogenic fluxes inferred from measured and modeled cropland soil losses (74 Gt/y) is readily resolved by data on thicknesses and ages of alluvial sediment that has been deposited immediately down slope from eroding croplands over the history of human agriculture. Accumulation of post-settlement alluvium on higher order tributary channels and floodplains (mean rate ~12,600 m/My) is the most important geomorphic process in terms of the erosion and deposition of sediment that is currently shaping the landscape of the Earth. It far exceeds even the impact of Pleistocene continental glaciers or the current impact of alpine erosion by glacial and/or fluvial processes. Human beings are therefore the dominant agent of topographic change operating on the surface of the planet today.

Climate-sensitive feedbacks between hillslope processes and fluvial erosion in sediment-driven incision models

NASA Astrophysics Data System (ADS)

Skov, Daniel S.; Egholm, David L.

2016-04-01

Surface erosion and sediment production seem to have accelerated globally as climate cooled in the Late Cenozoic, [Molnar, P. 2004, Herman et al 2013]. Glaciers emerged in many high mountain ranges during the Quaternary, and glaciation therefore represents a likely explanation for faster erosion in such places. Still, observations and measurements point to increases in erosion rates also in landscapes where erosion is driven mainly by fluvial processes [Lease and Ehlers (2013), Reusser (2004)]. Flume experiments and fieldwork have shown that rates of incision are to a large degree controlled by the sediment load of streams [e.g. Sklar and Dietrich (2001), Beer and Turowski (2015)]. This realization led to the formulation of sediment-flux dependent incision models [Sklar and Dietrich (2004)]. The sediment-flux dependence links incision in the channels to hillslope processes that supply sediment to the channels. The rates of weathering and soil transport on the hillslopes are processes that are likely to respond to changing temperatures, e.g. because of vegetation changes or the occurrence of frost. In this study, we perform computational landscape evolution experiments, where the coupling between fluvial incision and hillslope processes is accounted for by coupling a sediment-flux-dependent model for fluvial incision to a climate-dependent model for weathering and hillslope sediment transport. The computational experiments first of all demonstrate a strong positive feedback between channel and hillslope processes. In general, faster weathering leads to higher rates of channel incision, which further increases the weathering rates, mainly because of hillslope steepening. Slower weathering leads to the opposite result. The experiments also demonstrate, however, that the feedbacks vary significantly between different parts of a drainage network. For example, increasing hillslope sediment production may accelerate incision in the upper parts of the catchment, while at the same time the channel bed in the lower parts become shielded from incision by a perpetual sediment cover and incision stalls. These differences cause transients of erosion to migrate through the drainage network. Beer, Alexander R., and J. M. Turowski. "Bedload transport controls bedrock erosion under sediment-starved conditions." Earth Surface Dynamics 3.3 (2015): 291-309. Herman, Frédéric, et al. "Worldwide acceleration of mountain erosion under a cooling climate." Nature 504.7480 (2013): 423-426. Lease, Richard O., and Todd A. Ehlers. "Incision into the Eastern Andean plateau during Pliocene cooling." Science 341.6147 (2013): 774-776. Molnar, Peter. "Late Cenozoic increase in accumulation rates of terrestrial sediment: how might climate change have affected erosion rates?." Annu. Rev. Earth Planet. Sci. 32 (2004): 67-89. Reusser, Luke J., et al. "Rapid Late Pleistocene incision of Atlantic passive-margin river gorges." Science 305.5683 (2004): 499-502. Sklar, Leonard S., and William E. Dietrich. "Sediment and rock strength controls on river incision into bedrock." Geology 29.12 (2001): 1087-1090. Sklar, Leonard S., and William E. Dietrich. "A mechanistic model for river incision into bedrock by saltating bed load." Water Resources Research 40.6 (2004).

LANDPLANER (LANDscape, Plants, LANdslide and ERosion): a model to describe the dynamic response of slopes (or basins) under different changing scenarios

NASA Astrophysics Data System (ADS)

Rossi, Mauro; Torri, Dino; Santi, Elisa; Bacaro, Giovanni; Marchesini, Ivan

2014-05-01

Landslide phenomena and erosion processes are widespread and cause every year extensive damages to the environment and sensible reduction of ecosystem services. These processes are in competition among them, and their complex interaction control the landscapes evolution. Landslide phenomena and erosion processes can be strongly influenced by land use, vegetation, soil characteristics and anthropic actions. Such type of phenomena are mainly model separately using empirical and physically based approaches. The former rely upon the identification of simple empirical laws correlating/relating the occurrence of instability processes to some of their potential causes. The latter are based on physical descriptions of the processes, and depending on the degree of complexity they can integrate different variables characterizing the process and their trigger. Those model often couple an hydrological model with an erosion or a landslide model. The spatial modeling schemas are heterogeneous, but mostly the raster (i.e. matrices of data) or the conceptual (i.e. cascading planes and channels) description of the terrain are used. The two model types are generally designed and applied at different scales. Empirical models, less demanding in terms of input data cannot consider explicitly the real process triggering mechanisms and commonly they are exploited to assess the potential occurrence of instability phenomena over large areas (small scale assessment). Physically-based models are high-demanding in term of input data, difficult to obtain over large areas if not with large uncertainty, and their applicability is often limited to small catchments or single slopes (large scale assessment). More those models, even if physically-based, are simplified description of the instability processes and can neglect significant issues of the real triggering mechanisms. For instance the influence of vegetation has been considered just partially. Although in the literature a variety of model approaches have been proposed to model separately landslide and erosion processes, only few attempts were made to model both jointly, mostly integrating pre-existing models. To overcome this limitation we develop a new model called LANDPLANER (LANDscape, Plants, LANdslide and ERosion), specifically design to describe the dynamic response of slopes (or basins) under different changing scenarios including: (i) changes of meteorological factors, (ii) changes of vegetation or land-use, (iii) and changes of slope morphology. The was applied in different study area in order to check its basic assumptions, and to test its general operability and applicability. Results show a reasonable model behaviors and confirm its easy applicability in real cases.

Organo luminescent semiconductor nanocrystal probes for biological applications and process for making and using such probes

DOEpatents

Weiss, Shimon [Pinole, CA; Bruchez, Jr., Marcel; Alivisatos, Paul [Oakland, CA

2008-01-01

A semiconductor nanocrystal compound is described capable of linking to an affinity molecule. The compound comprises (1) a semiconductor nanocrystal capable of emitting electromagnetic radiation and/or absorbing energy, and/or scattering or diffracting electromagnetic radiation--when excited by an electromagnetic radiation source or a particle beam; and (2) an affinity molecule linked to the semiconductor nanocrystal. The semiconductor nanocrystal is linked to an affinity molecule to form a semiconductor nanocrystal probe capable of bonding with a detectable substance. Exposure of the semiconductor nanocrystal to excitation energy will excite the semiconductor nanocrystal causing the emission of electromagnetic radiation. Further described are processes for respectively: making the luminescent semiconductor nanocrystal compound; making the semiconductor nanocrystal probe; and using the probe to determine the presence of a detectable substance in a material.

Spontaneous ultraweak photon emission from biological systems and the endogenous light field.

PubMed

Schwabl, Herbert; Klima, Herbert

2005-04-01

Still one of the most astonishing biological electromagnetic phenomena is the ultraweak photon emission (UPE) from living systems. Organisms and tissues spontaneously emit measurable intensities of light, i.e. photons in the visible part of the electromagnetic spectrum (380-780 nm), in the range from 1 to 1,000 photons x s-1 x cm-2, depending on their condition and vitality. It is important not to confuse UPE from living systems with other biogenic light emitting processes such as bioluminescence or chemiluminescence. This article examines with basic considerations from physics on the quantum nature of photons the empirical phenomenon of UPE. This leads to the description of the non-thermal origin of this radiation. This is in good correspondence with the modern understanding of life phenomena as dissipative processes far from thermodynamic equilibrium. UPE also supports the understanding of life sustaining processes as basically driven by electromagnetic fields. The basic features of UPE, like intensity and spectral distribution, are known in principle for many experimental situations. The UPE of human leukocytes contributes to an endogenous light field of about 1011 photons x s-1 which can be influenced by certain factors. Further research is needed to reveal the statistical properties of UPE and in consequence to answer questions about the underlying mechanics of the biological system. In principle, statistical properties of UPE allow to reconstruct phase-space dynamics of the light emitting structures. Many open questions remain until a proper understanding of the electromagnetic interaction of the human organism can be achieved: which structures act as receptors and emitters for electromagnetic radiation? How is electromagnetic information received and processed within cells?

Broadband electromagnetic analysis of compacted kaolin

NASA Astrophysics Data System (ADS)

Bore, Thierry; Wagner, Norman; Cai, Caifang; Scheuermann, Alexander

2017-01-01

The mechanical compaction of soil influences not only the mechanical strength and compressibility but also the hydraulic behavior in terms of hydraulic conductivity and soil suction. At the same time, electric and dielectric parameters are increasingly used to characterize soil and to relate them with mechanic and hydraulic parameters. In the presented study electromagnetic soil properties and suction were measured under defined conditions of standardized compaction tests. The impact of external mechanical stress conditions of nearly pure kaolinite was analyzed on soil suction and broadband electromagnetic soil properties. An experimental procedure was developed and validated to simultaneously determine mechanical, hydraulic and broadband (1 MHz-3 GHz) electromagnetic properties of the porous material. The frequency dependent electromagnetic properties were modeled with a classical mixture equation (advanced Lichtenecker and Rother model, ALRM) and a hydraulic-mechanical-electromagnetic coupling approach was introduced considering water saturation, soil structure (bulk density, porosity), soil suction (pore size distribution, water sorption) as well as electrical conductivity of the aqueous pore solution. Moreover, the relaxation behavior was analyzed with a generalized fractional relaxation model concerning a high-frequency water process and two interface processes extended with an apparent direct current conductivity contribution. The different modeling approaches provide a satisfactory agreement with experimental data for the real part. These results show the potential of broadband electromagnetic approaches for quantitative estimation of the hydraulic state of the soil during densification.

Integrating WEPP into the WEPS infrastructure

USDA-ARS?s Scientific Manuscript database

The Wind Erosion Prediction System (WEPS) and the Water Erosion Prediction Project (WEPP) share a common modeling philosophy, that of moving away from primarily empirically based models based on indices or "average conditions", and toward a more process based approach which can be evaluated using ac...

Enhancing wind erosion monitoring and assessment for US rangelands

USDA-ARS?s Scientific Manuscript database

Wind erosion is a major resource concern for rangeland managers because it can impact soil health, ecosystem structure and function, hydrologic processes, agricultural production and air quality. Despite its significance, little is known about which landscapes are eroding, by how much, and when. T...

Surface kinetic roughening caused by dental erosion: An atomic force microscopy study

NASA Astrophysics Data System (ADS)

Quartarone, Eliana; Mustarelli, Piercarlo; Poggio, Claudio; Lombardini, Marco

2008-05-01

Surface kinetic roughening takes place both in case of growth and erosion processes. Teeth surfaces are eroded by contact with acid drinks, such as those used to supplement mineral salts during sporting activities. Calcium-phosphate based (CPP-ACP) pastes are known to reduce the erosion process, and to favour the enamel remineralization. In this study we used atomic force microscopy (AFM) to investigate the surface roughening during dental erosion, and the mechanisms at the basis of the protection role exerted by a commercial CPP-ACP paste. We found a statistically significant difference (p<0.01) in the roughness of surfaces exposed and not exposed to the acid solutions. The treatment with the CPP-ACP paste determined a statistically significant reduction of the roughness values. By interpreting the AFM results in terms of fractal scaling concepts and continuum stochastic equations, we showed that the protection mechanism of the paste depends on the chemical properties of the acid solution.

Hybrid-PIC Computer Simulation of the Plasma and Erosion Processes in Hall Thrusters

NASA Technical Reports Server (NTRS)

Hofer, Richard R.; Katz, Ira; Mikellides, Ioannis G.; Gamero-Castano, Manuel

2010-01-01

HPHall software simulates and tracks the time-dependent evolution of the plasma and erosion processes in the discharge chamber and near-field plume of Hall thrusters. HPHall is an axisymmetric solver that employs a hybrid fluid/particle-in-cell (Hybrid-PIC) numerical approach. HPHall, originally developed by MIT in 1998, was upgraded to HPHall-2 by the Polytechnic University of Madrid in 2006. The Jet Propulsion Laboratory has continued the development of HPHall-2 through upgrades to the physical models employed in the code, and the addition of entirely new ones. Primary among these are the inclusion of a three-region electron mobility model that more accurately depicts the cross-field electron transport, and the development of an erosion sub-model that allows for the tracking of the erosion of the discharge chamber wall. The code is being developed to provide NASA science missions with a predictive tool of Hall thruster performance and lifetime that can be used to validate Hall thrusters for missions.

Effects of soil type and rainfall intensity on sheet erosion processes and sediment characteristics along the climatic gradient in central-south China.

PubMed

Wu, Xinliang; Wei, Yujie; Wang, Junguang; Xia, Jinwen; Cai, Chongfa; Wei, Zhiyuan

2018-04-15

Soil erosion poses a major threat to the sustainability of natural ecosystems. The main objective of this study was to investigate the effects of soil type and rainfall intensity on sheet erosion processes (hydrological, erosional processes and sediment characteristics) from temperate to tropical climate. Field plot experiments were conducted under pre-wetted bare fallow condition for five soil types (two Luvisols, an Alisol, an Acrisol and a Ferralsol) with heavy textures (silty clay loam, silty clay and clay) derived separately from loess deposits, quaternary red clays and basalt in central-south China. Rainfall simulations were performed at two rainfall intensities (45 and 90mmh -1 ) and lasted one hour after runoff generation. Runoff coefficient, sediment concentration, sediment yield rate and sediment effective size distribution were determined at 3-min intervals. Runoff temporal variations were similar at the high rainfall intensity, but exhibited a remarkable difference at the low rainfall intensity among soil types except for tropical Ferralsol. Illite was positively correlated with runoff coefficient (p<0.05). Rainfall intensity significantly contributed to the erosional process (p<0.001). Sediment concentration and yield rate were the smallest for the tropical Ferralsol and sediment concentration was the largest for the temperate Luvisol. The regimes (transport and detachment) limiting erosion varied under the interaction of rainfall characteristics (intensity and duration) and soil types, with amorphous iron oxides and bulk density jointly enhancing soil resistance to erosive forces (Adj-R 2 >88%, p<0.001). Sediment size was dominated by <0.1mm size fraction for the Luvisols and bimodally distributed with the peaks at <0.1mm and 1-0.5mm size for the other soil types. Exchangeable sodium decreased sediment size while rainfall intensity and clay content increased it (Adj-R 2 =96%, p<0.01). These results allow to better understand the climate effect on erosion processes at the spatial-temporal scale from the perspective of soil properties. Copyright © 2017 Elsevier B.V. All rights reserved.

Influence of Spectral Transfer Processes in Compressible Low Frequency Plasma Turbulence on Scattering and Refraction of Electromagnetic Signals

DTIC Science & Technology

2015-01-01

AFRL-RY-WP-TR-2014-0230 INFLUENCE OF SPECTRAL TRANSFER PROCESSES IN COMPRESSIBLE LOW FREQUENCY PLASMA TURBULENCE ON SCATTERING AND...INFLUENCE OF SPECTRAL TRANSFER PROCESSES IN COMPRESSIBLE LOW FREQUENCY PLASMA TURBULENCE ON SCATTERING AND REFRACTION OF ELECTROMAGNETIC SIGNALS 5a...research is to analyze influence of plasma turbulence on hypersonic sensor systems and NGOTHR applications and to meet the Air Force’s ever-increasing

LAPSUS: soil erosion - landscape evolution model

NASA Astrophysics Data System (ADS)

van Gorp, Wouter; Temme, Arnaud; Schoorl, Jeroen

2015-04-01

LAPSUS is a soil erosion - landscape evolution model which is capable of simulating landscape evolution of a gridded DEM by using multiple water, mass movement and human driven processes on multiple temporal and spatial scales. It is able to deal with a variety of human landscape interventions such as landuse management and tillage and it can model their interactions with natural processes. The complex spatially explicit feedbacks the model simulates demonstrate the importance of spatial interaction of human activity and erosion deposition patterns. In addition LAPSUS can model shallow landsliding, slope collapse, creep, solifluction, biological and frost weathering, fluvial behaviour. Furthermore, an algorithm to deal with natural depressions has been added and event-based modelling with an improved infiltration description and dust deposition has been pursued. LAPSUS has been used for case studies in many parts of the world and is continuously developing and expanding. it is now available for third-party and educational use. It has a comprehensive user interface and it is accompanied by a manual and exercises. The LAPSUS model is highly suitable to quantify and understand catchment-scale erosion processes. More information and a download link is available on www.lapsusmodel.nl.

Mathematical modeling of degradation for bulk-erosive polymers: applications in tissue engineering scaffolds and drug delivery systems.

PubMed

Chen, Yuhang; Zhou, Shiwei; Li, Qing

2011-03-01

The degradation of polymeric biomaterials, which are widely exploited in tissue engineering and drug delivery systems, has drawn significant attention in recent years. This paper aims to develop a mathematical model that combines stochastic hydrolysis and mass transport to simulate the polymeric degradation and erosion process. The hydrolysis reaction is modeled in a discrete fashion by a fundamental stochastic process and an additional autocatalytic effect induced by the local carboxylic acid concentration in terms of the continuous diffusion equation. Illustrative examples of microparticles and tissue scaffolds demonstrate the applicability of the model. It is found that diffusive transport plays a critical role in determining the degradation pathway, whilst autocatalysis makes the degradation size dependent. The modeling results show good agreement with experimental data in the literature, in which the hydrolysis rate, polymer architecture and matrix size actually work together to determine the characteristics of the degradation and erosion processes of bulk-erosive polymer devices. The proposed degradation model exhibits great potential for the design optimization of drug carriers and tissue scaffolds. Copyright © 2010 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

Modeling runoff and erosion risk in a~small steep cultivated watershed using different data sources: from on-site measurements to farmers' perceptions

NASA Astrophysics Data System (ADS)

Auvet, B.; Lidon, B.; Kartiwa, B.; Le Bissonnais, Y.; Poussin, J.-C.

2015-09-01

This paper presents an approach to model runoff and erosion risk in a context of data scarcity, whereas the majority of available models require large quantities of physical data that are frequently not accessible. To overcome this problem, our approach uses different sources of data, particularly on agricultural practices (tillage and land cover) and farmers' perceptions of runoff and erosion. The model was developed on a small (5 ha) cultivated watershed characterized by extreme conditions (slopes of up to 55 %, extreme rainfall events) on the Merapi volcano in Indonesia. Runoff was modelled using two versions of STREAM. First, a lumped version was used to determine the global parameters of the watershed. Second, a distributed version used three parameters for the production of runoff (slope, land cover and roughness), a precise DEM, and the position of waterways for runoff distribution. This information was derived from field observations and interviews with farmers. Both surface runoff models accurately reproduced runoff at the outlet. However, the distributed model (Nash-Sutcliffe = 0.94) was more accurate than the adjusted lumped model (N-S = 0.85), especially for the smallest and biggest runoff events, and produced accurate spatial distribution of runoff production and concentration. Different types of erosion processes (landslides, linear inter-ridge erosion, linear erosion in main waterways) were modelled as a combination of a hazard map (the spatial distribution of runoff/infiltration volume provided by the distributed model), and a susceptibility map combining slope, land cover and tillage, derived from in situ observations and interviews with farmers. Each erosion risk map gives a spatial representation of the different erosion processes including risk intensities and frequencies that were validated by the farmers and by in situ observations. Maps of erosion risk confirmed the impact of the concentration of runoff, the high susceptibility of long steep slopes, and revealed the critical role of tillage direction. Calibrating and validating models using in situ measurements, observations and farmers' perceptions made it possible to represent runoff and erosion risk despite the initial scarcity of hydrological data. Even if the models mainly provided orders of magnitude and qualitative information, they significantly improved our understanding of the watershed dynamics. In addition, the information produced by such models is easy for farmers to use to manage runoff and erosion by using appropriate agricultural practices.

Electromagnetic Components of Auroral Hiss and Lower Hybrid Waves in the Polar Magnetosphere

NASA Technical Reports Server (NTRS)

Wong, H. K.

1995-01-01

DE-1 has frequently observed waves in the whistler and lower hybrid frequencies range. Besides the electrostatic components, these waves also exhibit electromagnetic components. It is generally believed that these waves are excited by the electron acoustic instability and the electron-beam-driven lower hybrid instability. Because the electron acoustic and the lower hybrid waves are predominately electrostatic waves, they cannot account for the observed electromagnetic components. In this work, it is suggested that these electromagnetic components can be explained by waves that are generated near the resonance cone and that propagate away from the source. The role that these electromagnetic waves can play in particle acceleration processes at low altitude is discussed.

Channelization in porous media driven by erosion and deposition.

PubMed

Jäger, R; Mendoza, M; Herrmann, H J

2017-01-01

We develop and validate a new model to study simultaneous erosion and deposition in three-dimensional porous media. We study the changes of the porous structure induced by the deposition and erosion of matter on the solid surface and find that when both processes are active, channelization in the porous structure always occurs. The channels can be stable or only temporary depending mainly on the driving mechanism. Whereas a fluid driven by a constant pressure drop in general does not form steady channels, imposing a constant flux always produces stable channels within the porous structure. Furthermore we investigate how changes of the local deposition and erosion properties affect the final state of the porous structure, finding that the larger the range of wall shear stress for which there is neither erosion nor deposition, the more steady channels are formed in the structure.

Microwave thawing package and method

DOEpatents

Fathi, Zakaryae; Lauf, Robert J.

2004-03-16

A package for containing frozen liquids during an electromagnetic thawing process includes: a first section adapted for containing a frozen material and exposing the frozen material to electromagnetic energy; a second section adapted for receiving thawed liquid material and shielding the thawed liquid material from further exposure to electromagnetic energy; and a fluid communication means for allowing fluid flow between the first section and the second section.

Slurry Erosion Studies on Surface Modified 13Cr-4Ni Steels: Effect of Angle of Impingement and Particle Size

NASA Astrophysics Data System (ADS)

Manisekaran, T.; Kamaraj, M.; Sharrif, S. M.; Joshi, S. V.

2007-10-01

Hydroturbine steels, such as 13Cr-4Ni martensitic steels, are generally subjected to heavy-erosive wear and loss of efficiency due to solid particulate entrainment in the water. Surface-modified steels have proven to give better performance in terms of erosive wear resistance. In the present study, an attempt is made to investigate the effect of angle of impingement and particle size on slurry-jet erosion behavior of pulsed plasma nitrided and laser hardened 13Cr-4Ni steels. Laser hardening process has shown good performance at all angles of impingement due to martensitic transformation of retained austenite. Plastic deformation mode of material removal was also an evident feature of all laser-hardened surface damage locations. However, pulsed-plasma nitrided steels have exhibited chip formation and micro-cutting mode of erosive wear. Erosion with 150-300 μm size was twice compared to 150 μm size slurry particulates.

Mapping regional soil water erosion risk in the Brittany-Loire basin for water management agency

NASA Astrophysics Data System (ADS)

Degan, Francesca; Cerdan, Olivier; Salvador-Blanes, Sébastien; Gautier, Jean-Noël

2014-05-01

Soil water erosion is one of the main degradation processes that affect soils through the removal of soil particles from the surface. The impacts for environment and agricultural areas are diverse, such as water pollution, crop yield depression, organic matter loss and reduction in water storage capacity. There is therefore a strong need to produce maps at the regional scale to help environmental policy makers and soil and water management bodies to mitigate the effect of water and soil pollution. Our approach aims to model and map soil erosion risk at regional scale (155 000 km²) and high spatial resolution (50 m) in the Brittany - Loire basin. The factors responsible for soil erosion are different according to the spatial and time scales considered. The regional scale entails challenges about homogeneous data sets availability, spatial resolution of results, various erosion processes and agricultural practices. We chose to improve the MESALES model (Le Bissonnais et al., 2002) to map soil erosion risk, because it was developed specifically for water erosion in agricultural fields in temperate areas. The MESALES model consists in a decision tree which gives for each combination of factors the corresponding class of soil erosion risk. Four factors that determine soil erosion risk are considered: soils, land cover, climate and topography. The first main improvement of the model consists in using newly available datasets that are more accurate than the initial ones. The datasets used cover all the study area homogeneously. Soil dataset has a 1/1 000 000 scale and attributes such as texture, soil type, rock fragment and parent material are used. The climate dataset has a spatial resolution of 8 km and a temporal resolution of mm/day for 12 years. Elevation dataset has a spatial resolution of 50 m. Three different land cover datasets are used where the finest spatial resolution is 50 m over three years. Using these datasets, four erosion factors are characterized and quantified: the soil factors (soil sealing, erodibility and runoff), the rate of land cover over three years for each season and for 77 land use classes, the topographic factor (slope and drainage area) and the climate hazard (seasonal amount and rainfall erosivity). These modifications of the original MESALES model allow to better represent erosion risk for arable and bare land. We validated model results by stakeholder consultations and meetings over all the study area. The model has finally been modified taking into account validation results. Results are provided with a spatial resolution of 1 km, and then integrated into 2121 catchments. An erosion risk map for each season and an annual erosion risk map are produced. These new maps allow to organize in hierarchy 2121 catchments into three erosion risk classes. In the annual erosion risk map, 347 catchments have the highest erosion risk, which corresponds to 16 % of total Brittany-Loire basin area. Water management agency now uses these maps to identify priority areas and to plan specific preservation practices.

Evaluation of Karst Soil Erosion and Nutrient Loss Based on RUSLE Model in Guizhou Province

NASA Astrophysics Data System (ADS)

Zeng, Cheng; Li, Yangbing; Bai, Xiaoyong; Luo, Guangjie

2018-01-01

Based on GIS technology and RUSLE model, the spatial variation characteristics of soil erosion were analyzed in karst areas, and the relationship between soil erosion and soil nutrient loss was discussed. The results showed that the soil differences in spatial variation between nutrient losses. The results illustrate the total soil erosion in is 10316.31 × 104t • a-1, accounting for 84.95% of the total land area in Guizhou Province. The spatial distribution of soil erosion showing the characteristics of the southeast to the northwest strip. The annual average soil erosion modulu is 691.94 t • km-2 • a-1, of which karst is 720.28t • km-2 • a-1 and non-karst is 689.53 t • km-2 • a-1. The total nutrient losses such as soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP) and total potassium (TK) were 596.72 × 104t • a-1 due to soil erosion, and SOC, TN and TP and TK were 38.13, 1.61, 0.41 and 14.70t • km-2 • a-1, respectively. The average amount of loss and total loss are the largest in non-karst, and four kinds of nutrient is the smallest in karst gorge. The spatial variation of soil erosion in the study area is the process of increasing the erosion area with the increase of the erosion rate, and the difference of the spatial distribution of soil erosion determines the spatial distribution of soil nutrient loss.

An Assessment of the Impact of Urbanization on Soil Erosion in Inner Mongolia.

PubMed

Wang, Li-Yan; Xiao, Yi; Rao, En-Ming; Jiang, Ling; Xiao, Yang; Ouyang, Zhi-Yun

2018-03-19

Inner Mongolia, an autonomous region of the People's Republic of China, has experienced severe soil erosion following a period of rapid economic development and urbanization. To investigate how urbanization has influenced the extent of soil erosion in Inner Mongolia, we used urbanization and soil erosion data from 2000 through 2010 to determine the relationship between urbanization and soil erosion patterns. Two empirical equations-the Revised Universal Soil Loss Equation (RUSLE) and the Revised Wind Erosion Equation (RWEQ)-were used to estimate the intensity of soil erosion, and we performed backward linear regression to model how it changed with greater urbanization. There was an apparent increase in the rate of urbanization and a decrease in the area affected by soil erosion in 2010 compared to the corresponding values for 2000. The urban population stood at 11.32 million in 2010, which represented a 16.47% increase over that in 2000. The area affected by soil erosion in 2000 totaled 704,817 km², yet it had decreased to 674,135 km² by 2010. However, a path of modest urban development (rural-urban mitigation) and reasonable industrial structuring (the development of GDP-2) may partially reduce urbanization's ecological pressure and thus indirectly reduce the threat of soil erosion to human security. Therefore, to better control soil erosion in Inner Mongolia during the process of urbanization, the current model of economic development should be modified to improve the eco-efficiency of urbanization, while also promoting new modes of urbanization that are environmentally sustainable, cost-effective, and conserve limited resources.

An Assessment of the Impact of Urbanization on Soil Erosion in Inner Mongolia

PubMed Central

Xiao, Yi; Rao, En-Ming; Jiang, Ling; Xiao, Yang; Ouyang, Zhi-Yun

2018-01-01

Inner Mongolia, an autonomous region of the People’s Republic of China, has experienced severe soil erosion following a period of rapid economic development and urbanization. To investigate how urbanization has influenced the extent of soil erosion in Inner Mongolia, we used urbanization and soil erosion data from 2000 through 2010 to determine the relationship between urbanization and soil erosion patterns. Two empirical equations—the Revised Universal Soil Loss Equation (RUSLE) and the Revised Wind Erosion Equation (RWEQ)—were used to estimate the intensity of soil erosion, and we performed backward linear regression to model how it changed with greater urbanization. There was an apparent increase in the rate of urbanization and a decrease in the area affected by soil erosion in 2010 compared to the corresponding values for 2000. The urban population stood at 11.32 million in 2010, which represented a 16.47% increase over that in 2000. The area affected by soil erosion in 2000 totaled 704,817 km2, yet it had decreased to 674,135 km2 by 2010. However, a path of modest urban development (rural–urban mitigation) and reasonable industrial structuring (the development of GDP-2) may partially reduce urbanization’s ecological pressure and thus indirectly reduce the threat of soil erosion to human security. Therefore, to better control soil erosion in Inner Mongolia during the process of urbanization, the current model of economic development should be modified to improve the eco-efficiency of urbanization, while also promoting new modes of urbanization that are environmentally sustainable, cost-effective, and conserve limited resources. PMID:29562707

Cavitation Erosion in Hydraulic Turbine Components and Mitigation by Coatings: Current Status and Future Needs

NASA Astrophysics Data System (ADS)

Singh, Raghuvir; Tiwari, S. K.; Mishra, Suman K.

2012-07-01

Cavitation erosion is a frequently observed phenomenon in underwater engineering materials and is the primary reason for component failure. The damage due to cavitation erosion is not yet fully understood, as it is influenced by several parameters, such as hydrodynamics, component design, environment, and material chemistry. This article gives an overview of the current state of understanding of cavitation erosion of materials used in hydroturbines, coatings and coating methodologies for combating cavitation erosion, and methods to characterize cavitation erosion. No single material property fully characterizes the resistance to cavitation erosion. The combination of ultimate resilience, hardness, and toughness rather may be useful to estimate the cavitation erosion resistance of material. Improved hydrodynamic design and appropriate surface engineering practices reduce damage due to cavitation erosion. The coatings suggested for combating the cavitation erosion encompasses carbides (WC Cr2C3, Cr3C2, 20CrC-80WC), cermets of different compositions (e.g., 56W2C/Ni/Cr, 41WC/Ni/Cr/Co), intermetallic composites, intermetallic matrix composites with TiC reinforcement, composite nitrides such as TiAlN and elastomers. A few of them have also been used commercially. Thermal spraying, arc plasma spraying, and high velocity oxy-fuel (HVOF) processes have been used commercially to apply the coatings. Boronizing, laser surface hardening and cladding, chemical vapor deposition, physical vapor deposition, and plasma nitriding have been tried for surface treatments at laboratory levels and have shown promise to be used on actual components.

How well does the Post-fire Erosion Risk Management Tool (ERMiT) really work?

NASA Astrophysics Data System (ADS)

Robichaud, Peter; Elliot, William; Lewis, Sarah; Miller, Mary Ellen

2016-04-01

The decision of where, when, and how to apply the most effective postfire erosion mitigation treatments requires land managers to assess the risk of damaging runoff and erosion events occurring after a fire. The Erosion Risk Management Tool (ERMiT) was developed to assist post fire assessment teams identify high erosion risk areas and effectiveness of various mitigation treatments to reduce that risk. ERMiT is a web-based application that uses the Water Erosion Prediction Project (WEPP) technology to estimate erosion, in probabilistic terms, on burned and recovering forest, range, and chaparral lands with and without the application of mitigation treatments. User inputs are processed by ERMiT to combine rain event variability with spatial and temporal variabilities of hillslope burn severity and soil properties which are then used as WEPP inputs. Since 2007, the model has been used in making hundreds of land management decisions in the US and elsewhere. We use eight published field study sites in the Western US to compare ERMiT predictions to observed hillslope erosion rates. Most sites experience only a few rainfall events that produced runoff and sediment except for a California site with a Mediterranean climate. When hillslope erosion occurred, significant correlations occurred between the observed hillslope erosion and those predicted by ERMiT. Significant correlation occurred for most mitigation treatments as well as the five recovery years. These model validation results suggest reasonable estimates of probabilistic post-fire hillslope sediment delivery when compared to observation.

Electrical wire insulation and electromagnetic coil

DOEpatents

Bich, George J.; Gupta, Tapan K.

1984-01-01

An electromagnetic coil for high temperature and high radiation application in which glass is used to insulate the electrical wire. A process for applying the insulation to the wire is disclosed which results in improved insulation properties.

Erosion Rates of Volcanic-ash Derived Soils in the Blue Mountains of Eastern Oregon, USA: A Comparison Across Sales in Space and Time.

NASA Astrophysics Data System (ADS)

Wondzell, S. M.; Clifton, C. F.; Harris, R. M.; Ritchie, J. C.

2007-12-01

We examined present day rates of erosion in the Blue Mountains of eastern Oregon to quantify background erosion rates to provide standards for assessing possible accelerated rates of erosion resulting from wild fire or from land-management activities such as prescribed fire. The Skookum Creek watersheds, where stream discharge and sediment yield have been recorded continuously since the watersheds were gauged in 1992, provided a watershed-scale estimate of erosion rates. We installed hillslope erosion plots on north- and south- facing slopes within the watersheds in 2002 and collected data for three years to estimate short-term, hillslope- scale erosion rates. We also collected soil samples and analyzed them for 137Cs to get a 40-yr time- integrated estimate of hillslope erosion rates. Our results showed large differences between whole-watershed sediment yields and hillslope erosion rates measured from plots, suggesting that episodic processes dominated sediment production and transport and therefore controlled watershed-scale sediment budgets. At the hillslope-scale, short-term erosion resulted primarily from digging by small mammals and trampling by elk. Visual observations at the plots suggested that annual down-slope sediment movement was usually less than one meter. There were no significant difference among slope positions, but erosion rates were significantly higher on south-facing aspects and positively correlated to the amount of bare ground. In contrast, the 137Cs data suggested that erosion rates differed with slope position. Higher erosion rates were measured in toe- and mid-slope positions, with little erosion occurring on upper slopes and ridge tops. We examine these results in light of the present-day pattern of surface soils resulting from redistribution of volcanic ash from upper- slope to lower-slope positions and the effects of disturbance, including wildfire and the preferential grazing of riparian and lower-slope positions by domestic livestock.

Prediction of Soil Erosion Rates in Japan where Heavily Forested Landscape with Unstable Terrain

NASA Astrophysics Data System (ADS)

Nanko, K.; Oguro, M.; Miura, S.; Masaki, T.

2016-12-01

Soil is fundamental for plant growth, water conservation, and sustainable forest management. Multidisciplinary interest in the role of the soil in areas such as biodiversity, ecosystem services, land degradation, and water security has been growing (Miura et al., 2015). Forest is usually protective land use from soil erosion because vegetation buffers rainfall power and erosivity. However, some types of forest in Japan show high susceptibility to soil erosion due to little ground cover and steep slopes exceeding thirty degree, especially young Japanese cypress (Chamaecyparis obtusa) plantations (Miura et al., 2002). This is a critical issue for sustainable forest management because C. obtusaplantations account for 10% of the total forest coverage in Japan (Forestry Agency, 2009). Prediction of soil erosion rates on nationwide scale is necessary to make decision for future forest management plan. To predict and map soil erosion rates across Japan, we applied three soil erosion models, RUSLE (Revised Universal Soil Loss Equation, Wischmeier and Smith, 1978), PESERA (Pan-European Soil Erosion Risk Assessment, Kirkby et al., 2003), and RMMF (Revised Morgan-Morgan-Finney, Morgan, 2001). The grid scale is 1-km. RUSLE and PESERA are most widely used erosion models today. RMMF includes interactions between rainfall and vegetation, such as canopy interception and ratio of canopy drainage in throughfall. Evaporated rainwater by canopy interception, generally accounts for 15-20% in annual rainfall, does not contribute soil erosion. Whereas, larger raindrops generated by canopy drainage produced higher splash erosion rates than gross rainfall (Nanko et al., 2008). Therefore, rainfall redistribution process in canopy should be considered to predict soil erosion rates in forested landscape. We compared the results from three erosion models and analyze the importance of environmental factors for the prediction of soil erosion rates. This research was supported by the Environment Research and Technology Development Fund (S15-2-2) of the Ministry of the Environment, Japan.

Bank Erosion, Mass Wasting, Water Clarity, Bathymetry and a Sediment Budget Along the Dam-Regulated Lower Roanoke River, North Carolina

USGS Publications Warehouse

Schenk, Edward R.; Hupp, Cliff R.; Richter, Jean M.; Kroes, Daniel E.

2010-01-01

Dam construction and its impact on downstream fluvial processes may substantially alter ambient bank stability, floodplain inundation patterns, and channel morphology. Most of the world's largest rivers have been dammed, which has prompted management efforts to mitigate dam effects. Three high dams (completed between 1953 and 1963) occur along the Piedmont portion of the Roanoke River, North Carolina; just downstream, the lower part of the river flows across largely unconsolidated Coastal Plain deposits. To document bank erosion rates along the lower Roanoke River, more than 700 bank erosion pins were installed along 124 bank transects. Additionally, discrete measurements of channel bathymetry, water clarity, and presence or absence of mass wasting were documented along the entire 153-kilometer-long study reach. Amounts of bank erosion in combination with prior estimates of floodplain deposition were used to develop a bank erosion and floodplain deposition sediment budget for the lower river. Present bank erosion rates are relatively high [mean 42 milimeters per year (mm/yr)] and are greatest along the middle reaches (mean 60 mm/yr) and on lower parts of the bank on all reaches. Erosion rates were likely higher along upstream reaches than present erosion rates such that erosion rate maxima have migrated downstream. Mass wasting and water clarity also peak along the middle reaches.

Dental erosion and its association with diet in Libyan schoolchildren.

PubMed

Huew, R; Waterhouse, P J; Moynihan, P J; Kometa, S; Maguire, A

2011-10-01

To investigate any association between dental erosion and its potential dietary risk factors in a group of schoolchildren in Benghazi, Libya. A cross-sectional observational study. A random sample of 12-year-old schoolchildren in 36 randomly selected schools completed a questionnaire to provide dietary data and underwent dental examination. Dental erosion was assessed using UK National Diet and Nutrition Survey (2000) criteria. Associations between erosion and dietary variables under study were investigated through processes of bivariate and multivariate analyses. Of 791 schoolchildren dentally examined, 40.8% had dental erosion; erosion into enamel affecting 32.5%, into dentine affecting 8% and into pulp affecting 0.3% of subjects. Bivariate analysis showed frequency of fruit-based sugary drink intake was statistically significantly and positively associated with erosion (p=0.006, Odds Ratio; 1.498, 95% CI; 1.124, 1.996) as was the length of time taken to consume acidic drinks (p≠0.005, Odds Ratio; 1.593, 95%CI; 1.161, 2.186). Additionally, multivariate analysis showed frequency of consumption of fruit other than bananas, sugared tea with milk and flavoured milk to also be positively associated with erosion (p=<0.05). In this group of Libyan 12-year-olds, frequency of consumption of fruit-based sugary drinks and length of time taken to consume acidic drinks were the primary statistically significant positive risk factors for dental erosion.

Characterization of cathode keeper wear by surface layer activation

NASA Technical Reports Server (NTRS)

Polk, James E.

2003-01-01

In this study, the erosion rates of the discharge cathode keeper in a 30 cm NSTAR configuration ion thruster were measured using a technique known as Surface Layer Activation (SLA). This diagnostic technique involves producing a radioactive tracer in a given surface by bombardment with high energy ions. The decrease in activity of the tracer material may be monitored as the surface is subjected to wear processes and correlated to a depth calibration curve, yielding the eroded depth. Analysis of the activities was achieved through a gamma spectroscopy system. The primary objectives of this investigation were to reproduce erosion data observed in previous wear studies in order to validate the technique, and to determine the effect of different engine operating parameters on erosion rate. The erosion profile at the TH 15 (23 kw) setting observed during the 8200 hour Life Demonstration Test (LDT) was reproduced. The maximum keeper erosion rate at this setting was determined to be 0.085 pm/hr. Testing at the TH 8 (1.4 kw) setting demonstrated lower erosion rates than TH 15, along with a different wear profile. Varying the keeper voltage was shown to have a significant effect on the erosion, with a positive bias with respect to cathode potential decreasing the erosion rate significantly. Accurate measurements were achieved after operating times of only 40 to 70 hours, a significant improvement over other erosion diagnostic methods.

Process-based soil erodibility estimation for empirical water erosion models

USDA-ARS?s Scientific Manuscript database

A variety of modeling technologies exist for water erosion prediction each with specific parameters. It is of interest to scrutinize parameters of a particular model from the point of their compatibility with dataset of other models. In this research, functional relationships between soil erodibilit...

Intra-storm temporal patterns of rainfall in China using Huff curves

USDA-ARS?s Scientific Manuscript database

The intra-storm temporal distributions of precipitation are important to infiltration, runoff and erosion processes and models. A convenient and established method for characterizing precipitation hyetographs is with the use of Huff curves. In this study, 11,801 erosive rainfall events with one-mi...

An application of LOTEM around salt dome near Houston, Texas

NASA Astrophysics Data System (ADS)

Paembonan, Andri Yadi; Arjwech, Rungroj; Davydycheva, Sofia; Smirnov, Maxim; Strack, Kurt M.

2017-07-01

A salt dome is an important large geologic structure for hydrocarbon exploration. It may seal a porous reservoir of rocks that form petroleum reservoirs. Several techniques such as seismic, gravity, and electromagnetic including magnetotelluric have successfully yielded salt dome interpretation. Seismic has difficulties seeing through the salt because the seismic energy gets trapped by the salt due to its high velocity. Gravity and electromagnetics are more ideal methods. Long Offset Transient Electromagnetic (LOTEM) and Focused Source Electromagnetic (FSEM) were tested over a salt dome near Houston, Texas. LOTEM data were recorded at several stations with varying offset, and the FSEM tests were also made at some receiver locations near a suspected salt overhang. The data were processed using KMS's processing software: First, for assurance, including calibration and header checking; then transmitter and receiver data are merged and microseismic data is separated; Finally, data analysis and processing follows. LOTEM processing leads to inversion or in the FSEM case 3D modeling. Various 3D models verify the sensitivity under the salt dome. In addition, the processing was conducted pre-stack, stack, and post-stack. After pre-stacking, the noise was reduced, but showed the ringing effect due to a low-pass filter. Stacking and post-stacking with applying recursive average could reduce the Gibbs effect and produce smooth data.

The microscale evolution of the erosion front of blood clots exposed to ultrasound stimulated microbubbles.

PubMed

Acconcia, Christopher N; Leung, Ben Y C; Goertz, David E

2016-05-01

Serial two-photon microscopy of blood clots with fluorescently tagged fibrin networks was conducted during microbubble-mediated sonothrombolysis to examine the microscale evolution of the resulting erosion front. The development of a complex zonal erosion pattern was observed, comprised of a cell depleted layer of fibrin network overlying intact clot which then underwent progressive recession. The fibrin zone architecture was dependent on exposure conditions with 0.1 MPa causing no erosion, 0.39 MPa resulting in homogenous structure, and combination 0.39/0.96 MPa pulses forming large-scale tunnels. High speed imaging and Coulter counter data indicated the fibrin zone formation process involves the ejection of intact erythrocytes.

Real-time wideband cylindrical holographic surveillance system

DOEpatents

Sheen, D.M.; McMakin, D.L.; Hall, T.E.; Severtsen, R.H.

1999-01-12

A wideband holographic cylindrical surveillance system is disclosed including a transceiver for generating a plurality of electromagnetic waves; antenna for transmitting the electromagnetic waves toward a target at a plurality of predetermined positions in space; the transceiver also receiving and converting electromagnetic waves reflected from the target to electrical signals at a plurality of predetermined positions in space; a computer for processing the electrical signals to obtain signals corresponding to a holographic reconstruction of the target; and a display for displaying the processed information to determine nature of the target. The computer has instructions to apply Fast Fourier Transforms and obtain a three dimensional cylindrical image. 13 figs.

Post-fire hillslope debris flows: Evidence of a distinct erosion process

NASA Astrophysics Data System (ADS)

Langhans, Christoph; Nyman, Petter; Noske, Philip J.; Van der Sant, Rene E.; Lane, Patrick N. J.; Sheridan, Gary J.

2017-10-01

After wildfire a hitherto unexplained erosion process that some authors have called 'miniature debris flows on hillslopes' and that leave behind levee-lined rills has been observed in some regions of the world. Despite the unusual proposition of debris flow on planar hillslopes, the process has not received much attention. The objectives of this study were to (1) accumulate observational evidence of Hillslope Debris Flows (HDF) as we have defined the process, to (2) understand their initiation process by conducting runoff experiments on hillslopes, to (3) propose a conceptual model of HDF, and to (4) contrast and classify HDF relative to other erosion and transport processes in the post-wildfire hillslope domain. HDF have been observed at relatively steep slope gradients (0.4-0.8), on a variety of geologies, and after fire of at least moderate severity and consist of a lobe of gravel- to cobble-sized material 0.2-1 m wide that is pushed by runoff damming up behind it. During initiation, runoff moved individual particles that accumulated a small distance downslope until the accumulation of grains failed and formed the granular lobe of the HDF. HDF are a threshold process, and runoff rates of 0.5 L s- 1 2 L s- 1 were required for their initiation during the experiments. The conceptual model highlights HDF as a geomorphic process distinct from channel debris flows, because they occur on planar, unconfined hillslopes rather than confined channels. HDF can erode very coarse non-cohesive surface soil, which distinguishes them from rill erosion that have suspended and bedload transport. On a matrix of slope and grain size, HDF are enveloped between purely gravity-driven dry ravel, and mostly runoff driven bedload transport in rills.

Soil erosion measurements by means of experimental plots to determine best land management strategies in vineyards and olive orchards

NASA Astrophysics Data System (ADS)

Cerdà, Artemi; Keesstra, Saskia; Jordan, Antonio; Brevik, Erik; Nova, Agata; Prosdocimi, Massimo; Azorín-Molina, César; Yazdanpanah, Najme; Mahmoodabadi, Majid; Pereira, Paulo; Burguet, María

2016-04-01

In order to design sustainable land management there is a need to have accurate information on the impact this land management strategies have on water and sediment dynamics. This is especially important when a proper management is designed to reduce the soil losses due to the complex interaction of mechanisms that interact within the soil erosion process. Soil erosion is an non-linear process, both spatially and temporally, and as a consequence of that only well-monitored and accurate measurements can give insights in the processes and how these processes can be influenced by management to reduce soil losses (Cerdà, 2007; Ligonja and Shrestha, 2015; Nanko et al., 2015; Seutloali and Beckedahl, 2015). This is necessary at different scales: pedon, slope, and watershed because the governing processes differ at different scale (Keesstra, 2007; Jordán and Martínez Zavala, 2008; Borrelli et al., 2015). Soil erosion plots can give information about the temporal and spatial variability of soil losses. We present here a strategy developed by the Soil Erosion and Degradation Research Group from the University of Valencia to assess the soil erosion rates in Eastern Spain. In 2002 the Soil Erosion Experimental Station in El Teularet-Sierra de Enguera was installed, to assess soil losses in rainfed agriculture orchards, and 73 plots of 1, 2, 4, 16 and 48 m2 were installed. In 2005 6 plots of 300 m2 were installed in the nearby Montesa soil erosion station to assess soil losses in citrus orchards. In 2011 16 plots of 2 m2 where installed in Les Alcusses to determine soil losses in olive orchards, and in 2015 8 plots in Celler del Roure vineyard to assess the impact of land management in vineyards and 8 plots in the El Teularet to study the impact of straw mulch on soil erosion rates. All erosion stations are located in several kilometres distance from each other. This research which we developed since 2002 is complementary to previous research where we used rainfall simulation experiments to assess soil properties under different management (Cerdà, 1997; Cerdà, 1998a; Cerdà 1998b; Cerdà, 2001). The results from the soil erosion plots monitoring demonstrate the positive impact of vegetation to reduce soil loss. In addition, we proved that the use of straw, chipped pruned branches and rock fragments as surface cover reduces soil losses (Cerdà et al., 2015, Pereira et al., 2015; Prosdocimi et al., 2016). Acknowledgements The research leading to these results has received funding from the European Union Seventh Framework Programme (FP7/2007-2013) under grant agreement n° 603498 (RECARE project) and by the Spanish Government with the research Project CGL2013- 47862-C2-1-R. References Borrelli, P., Märker, M., Schütt, B. 2015. Modelling Post-Tree-Harvesting soil erosion and sediment deposition potential in the turano river basin (Italian central apennine. Land Degradation and Development, 26, 356-366. DOI: 10.1002/ldr.2214 Cerdà, A. 1997.The effect of patchy distribution of Stipa tenacissima L. on runoff and erosion. Journal of Arid Environments, 36 (1), pp. 37-51.DOI: 10.1006/jare.1995.0198 Cerdà, A. 1998a. Changes in overland flow and infiltration after a rangeland fire in a Mediterranean scrubland. Hydrological Processes, 12 (7), pp. 1031-1042. Cerdà, A. 1998b Soil aggregate stability under different Mediterranean vegetation types. Catena, 32 (2), pp. 73-86. DOI: 10.1016/S0341-8162(98)00041-1 Cerdà, A. 2001. Effects of rock fragment cover on soil infiltration, interrill runoff and erosion. European Journal of Soil Science, 52 (1), pp. 59-68. DOI: 10.1046/j.1365-2389.2001.00354.x Cerdà, A. 2007. Soil water erosion on road embankments in eastern Spain. Science of the Total Environment, 378 (1-2), 151-155. DOI: 10.1016/j.scitotenv.2007.01.041 Cerdà, A., González-Pelayo, O., Giménez-Morera, A., Jordán, A., Pereira, P., Novara, A., Brevik, E.C., Prosdocimi, M., Mahmoodabadi, M., Keesstra, S., García Orenes, F., Ritsema, C., 2015. The use of barley straw residues to avoid high erosion and runoff rates on persimmon plantations in Eastern Spain under low frequency - high magnitude simulated rainfall events. Soil Res. (In press) Jordán, A., & Martínez-Zavala, L. 2008. Soil loss and runoff rates on unpaved forest roads in southern Spain after simulated rainfall. Forest Ecology and Management, 255(3), 913-919. Keesstra, S.D. 2007. Impact of natural reforestation on floodplain sedimentation in the Dragonja basin, SW Slovenia. Earth Surface Processes and Landforms, 32(1): 49-65. DOI: 10.1002/esp.1360 Ligonja, P.J., Shrestha, R.P. 2015. Soil erosion assessment in kondoa eroded area in Tanzania using universal soil loss equation, geographic information systems and socioeconomic approach (2015) Land Degradation and Development, 26 (4), pp. 367-379. DOI: 10.1002/ldr.2215 Nanko, K., Giambelluca, T.W., Sutherland, R.A., Mudd, R.G., Nullet, M.A., Ziegler, A.D. 2015.Erosion potential under miconia calvescens stands on the island of hawai'i. Land Degradation and Development, 26 (3), pp. 218-226. DOI: 10.1002/ldr.2200 Pereira, P., Giménez-Morera, A., Novara, A., Keesstra, S., Jordán, A., Masto, R. E., Brevik, E., Azorin-Molina, C. Cerdà, A. 2015. The impact of road and railway embankments on runoff and soil erosion in eastern Spain. Hydrology and Earth System Sciences Discussions, 12, 12947-12985. Prosdocimi,M., Jordán, A., Tarolli, P., Keesstra, S., Novara, A., Cerdà, A. 2016. The immediate effectiveness of barley straw mulch in reducing soil erodibility and surface runoff generation in Mediterranean vineyards. Science of The Total Environment, 547, 15 ,323-330, doi:10.1016/j.scitotenv.2015.12.076 Seutloali, K.E., Beckedahl, H.R. 2015. Understanding the factors influencing rill erosion on roadcuts in the south eastern region of South Africa. Solid Earth, 6 (2) 633-641. DOI: 10.5194/se-6-633-2015

Conceptual model of sediment processes in the upper Yuba River watershed, Sierra Nevada, CA

USGS Publications Warehouse

Curtis, J.A.; Flint, L.E.; Alpers, Charles N.; Yarnell, S.M.

2005-01-01

This study examines the development of a conceptual model of sediment processes in the upper Yuba River watershed; and we hypothesize how components of the conceptual model may be spatially distributed using a geographical information system (GIS). The conceptual model illustrates key processes controlling sediment dynamics in the upper Yuba River watershed and was tested and revised using field measurements, aerial photography, and low elevation videography. Field reconnaissance included mass wasting and channel storage inventories, assessment of annual channel change in upland tributaries, and evaluation of the relative importance of sediment sources and transport processes. Hillslope erosion rates throughout the study area are relatively low when compared to more rapidly eroding landscapes such as the Pacific Northwest and notable hillslope sediment sources include highly erodible andesitic mudflows, serpentinized ultramafics, and unvegetated hydraulic mine pits. Mass wasting dominates surface erosion on the hillslopes; however, erosion of stored channel sediment is the primary contributor to annual sediment yield. We used GIS to spatially distribute the components of the conceptual model and created hillslope erosion potential and channel storage models. The GIS models exemplify the conceptual model in that landscapes with low potential evapotranspiration, sparse vegetation, steep slopes, erodible geology and soils, and high road densities display the greatest hillslope erosion potential and channel storage increases with increasing stream order. In-channel storage in upland tributaries impacted by hydraulic mining is an exception. Reworking of stored hydraulic mining sediment in low-order tributaries continues to elevate upper Yuba River sediment yields. Finally, we propose that spatially distributing the components of a conceptual model in a GIS framework provides a guide for developing more detailed sediment budgets or numerical models making it an inexpensive way to develop a roadmap for understanding sediment dynamics at a watershed scale.