Quantification of long-term erosion rates from root exposure/tree age relationships in an alpine meadow catchment

NASA Astrophysics Data System (ADS)

Scuderi, Louis A.

2017-04-01

Erosion rates derived using dendrogeomorphology have been used to quantify slope degradation in many localities globally. However, with the exception of the western United States, most of these estimates are derived from short-lived trees whose lifetimes may not adequately reflect the complete range of slope processes which can include erosion, deposition, impacts of extreme events and even long-term hiatuses. Erosion rate estimates at a given site using standard techniques therefore reflect censored local point erosion estimates rather than long-term rates. We applied a modified dendrogeomorphic approach to rapidly estimate erosion rates from dbh/age relationships to assess the difference between short and long-term rates and found that the mean short-term rate was 0.13 cm/yr with high variability, while the uncensored long-term rate was 0.06 cm/yr. The results indicate that rates calculated from short-lived trees, while possibly appropriate for local short-term point estimates of erosion, are highly variable and may overestimate regional long-term rates by > 50%. While these findings do not invalidate the use of dendrogeomorphology to estimate erosion rates they do suggest that care must be taken to select older trees that incorporate a range of slope histories in order to best approximate regional long-term rates.

Quantification Of Erosion Rates Of Agriculturally Used Soils By Artificial

NASA Astrophysics Data System (ADS)

Jha, Abhinand

2010-05-01

. PIC Figure 4: Profiles of sediment calculated for different erosion rates by Cs-137 within the ploughed soil 3 Conclusions and outlook Erosion rates for agricultural soils at Young Moraine regions of North-East Germany were determined by using two radionuclides, 137Cs and 7Be. In combination, the two radionuclides provide a valuable means of investigating soil erosion and assessing erosion risk in the study area. Potentials and limitations of the erosion measurement techniques using radiotracers are discussed in this study. The models used to quantify erosion rates using 137Cs and 7Be were studied. Erosion rates calculated by theses models are difficult to measure over a period of 50 years. A validation of these erosion rates for the time period (50 years) used in the 137Cs-based models will give a new perspective to the use of soil erosion modeling. Most of the regions in India are suffering from high erosion rates [7]. By using the new techniques in erosion quantification the land management practices can be improved and the erosion risk can be reduced in India.

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

Long-term erosion rates of Panamanian drainage basins determined using in situ 10Be

NASA Astrophysics Data System (ADS)

Gonzalez, Veronica Sosa; Bierman, Paul R.; Nichols, Kyle K.; Rood, Dylan H.

2016-12-01

Erosion rates of tropical landscapes are poorly known. Using measurements of in situ-produced 10Be in quartz extracted from river and landslide sediment samples, we calculate long-term erosion rates for many physiographic regions of Panama. We collected river sediment samples from a wide variety of watersheds (n = 35), and then quantified 24 landscape-scale variables (physiographic, climatic, seismic, geologic, and land-use proxies) for each watershed before determining the relationship between these variables and long-term erosion rates using linear regression, multiple regression, and analysis of variance (ANOVA). We also used grain-size-specific 10Be analysis to infer the effect of landslides on the concentration of 10Be in fluvial sediment and thus on erosion rates. Cosmogenic 10Be-inferred, background erosion rates in Panama range from 26 to 595 m My- 1, with an arithmetic average of 201 m My- 1, and an area-weighted average of 144 m My- 1. The strongest and most significant relationship in the dataset was between erosion rate and silicate weathering rate, the mass of material leaving the basin in solution. None of the topographic variables showed a significant relationship with erosion rate at the 95% significance level; we observed weak but significant correlation between erosion rates and several climatic variables related to precipitation and temperature. On average, erosion rates in Panama are higher than other cosmogenically-derived erosion rates in tropical climates including those from Puerto Rico, Madagascar, Australia and Sri Lanka, likely the result of Panama's active tectonic setting and thus high rates of seismicity and uplift. Contemporary sediment yield and cosmogenically-derived erosion rates for three of the rivers we studied are similar, suggesting that human activities are not increasing sediment yield above long-term erosion rate averages in Panama. 10Be concentration is inversely proportional to grain size in landslide and fluvial samples

Natural and anthropogenic rates of soil erosion

USDA-ARS?s Scientific Manuscript database

Regions of land that are brought into crop production from native vegetation typically undergo a period of soil erosion instability, and long term erosion rates are greater than for natural lands as long as the land continues being used for crop production. Average rates of soil erosion under natur...

Quantification of soil erosion rates related to ancient Maya deforestation

NASA Astrophysics Data System (ADS)

Anselmetti, Flavio S.; Hodell, David A.; Ariztegui, Daniel; Brenner, Mark; Rosenmeier, Michael F.

2007-10-01

We used seismic and sediment core data to quantify soil erosion rates for the past ˜6000 yr in the closed catchment of Lake Salpetén, in the tropical lowlands of northern Guatemala. The region was affected by ancient Maya land use from before ca. 1000 B.C. to A.D. 900. This period of human impact coincided with deposition in the lake of a detrital unit (Maya Clay) as much as 7 m thick that contrasts sharply with the relatively organic-rich gyttja deposited both before and after Maya occupation of the watershed. The greatest soil loss, with mean sustained values of ˜1000 t/km2yr-1, occurred in the Middle and Late Preclassic Periods (700 B.C. to A.D. 250), associated with relatively low Maya population densities. Soil erosion slowed during the period of maximum population density in the Late Classic Period (A.D. 550-830), indicating a decoupling between human population density and soil erosion rate. The most rapid soil loss occurred early during initial land clearance, suggesting that even low numbers of people can have profound impacts on lowland tropical karst landscapes.

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.

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.

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.

Decoupling of long-term exhumation and short-term erosion rates in the Sikkim Himalaya

NASA Astrophysics Data System (ADS)

Abrahami, Rachel; van der Beek, Peter; Huyghe, Pascale; Hardwick, Elisabeth; Carcaillet, Julien

2016-01-01

Understanding the relative strengths of tectonic and climatic forcing on erosion at different spatial and temporal scales is important to understand the evolution of orogenic topography. To address this question, we quantified exhumation rates at geological timescales and erosion rates at millennial timescales in modern river sands from 10 sub-catchments of the Tista River drainage basin in the Sikkim Himalaya (northeast India) using detrital apatite fission-track thermochronology and cosmogenic 10Be analyses, respectively. We compare these rates to several potential geomorphic or climatic forcing parameters. Our results show that millennial erosion rates are generally higher and spatially more variable than long-term exhumation rates in Sikkim. They also show strongly contrasting spatial patterns, suggesting that the processes controlling these rates are decoupled. At geological timescales, exhumation rates decrease from south to north, with rates up to 1.2 ± 0.6 mm/yr recorded in southwest Sikkim and as low as 0.5 ± 0.2 mm/yr in the northernmost catchment. Long-term exhumation rates do not correlate with any geomorphic or climatic parameter. We suggest they are tectonically controlled: high rates in southwest Sikkim may be linked to the building of the Lesser Himalaya Rangit Duplex, whereas low rates in north Sikkim are consistent with cessation of extensional exhumation along the South Tibetan Detachment after 13 Ma. The highest apparent erosion rates recorded by cosmogenic nuclides (∼5 mm/yr) occur in catchments spanning the Main Central Thrust Zone, but these appear to be strongly influenced by recent landsliding. High millennial erosion rates (1-2 mm/yr) also occur in north Sikkim and may be climatically driven through strong glacial inheritance of the landscape, as attested by high channel-steepness values close to the maximum extent of glaciers during the Last Glacial Maximum. In contrast, variations in rainfall rate do not seem to strongly influence

Quantifying gully erosion contribution from morphodynamic analysis of historical aerial photographs in a large catchment SW Spain

NASA Astrophysics Data System (ADS)

Hayas, Antonio; Giráldez, Juan V.; Laguna, Ana; Peña, Peña; Vanwalleghem, Tom

2015-04-01

Gully erosion is widely recognized as an important erosion process and source of sediment, especially in Mediterranean basins. Recent advances in monitoring techniques, such as ground-based LiDAR, drone-bounded cameras or photoreconstruction, allow quantifying gully erosion rates with unprecedented accuracy. However, many studies only focus on gully growth during a short period. In agricultural areas, farmers frequently erase gullies artificially. Over longer time scales, this results in an important dynamic of gully growth and infilling. Also, given the significant temporal variability of precipitation, land use and the proper gully erosion processes, gully growth is non-linear over time. This study therefore aims at analyzing gully morphodynamics over a long time scale (1957-2011) in a large catchment in order to quantify gully erosion processes and its contribution to overall sediment dynamics. The 20 km2 study area is located in SW Spain. The extension of the gully network was digitized by photographic interpretation based on aerial photographs from 1957, 1981, 1985, 1999, 2002, 2005, 2007, 2009 and 2011. Gully width was measured at representative control points for each of these years. During this period, the dominant land use changed considerably from herbaceous crops to olive orchards. A field campaign was conducted in 2014 to measure current gully width and depth. Total gully volume and uncertainty was determined by Monte Carlo-based simulations of gully cross-sectional area for unmeasured sections. The extension of the gully network both increased and decreased in the study period. Gully density varied between 1.93 km km-2 in 1957, with a minimum of 1.37 km km-2 in 1981 and a maximum of 5.40 km km-2 in 2011. Gully width estimated in selected points from the orthophotos range between 0.9 m and 59.2 m, and showed a good lognormal fit. Field campaigns results in a collection of cross-section measures with gullies widths between 1.87 and 28.5 m and depths from

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...

Using 10Be to quantify rates of landscape change in 'dead' orogens - millennial scale rates of bedrock and basin-scale erosion in the southern and central Appalachian Mountains

NASA Astrophysics Data System (ADS)

Bierman, P. R.; Reusser, L.; Portenga, E.

2011-12-01

The Appalachian Mountain chain stretches north-south along the eastern margin of North America, in places rising a thousand meters and more above the adjacent piedmont. Here, Davis built his paradigm of landscape evolution, seeing landscape rejuvenation and dissected peneplains, a transient landscape. Hack saw the Appalachians as a dynamic system where topography was adjusted to rock strength, a steady-state landscape. Neither had quantitative data by which to test their theories. Today, we approach landscapes of the Appalachian Mountains quite differently. Over the past decade, we and others have measured in situ-produced 10Be in more than 300 samples of quartz isolated from Appalachian drainage basin sediments and in more than 100 samples from exposed Appalachian bedrock outcrops, most of which are on ridgelines. Samples have been collected from the Susquehanna, Potomac, and Shenandoah drainage basins as well as from the area around the Great Smoky Mountain National Park and the Blue Ridge escarpment, and from rivers draining from the Appalachians across the southeastern United States Piedmont. Most areas of the Appalachian Mountains are eroding only slowly; the average for all drainage basin samples analyzed to date is ~18 m/My (n=328). The highest basin-scale erosion rates, 25-70 m/My are found in the Appalachian Plateau and in the Great Smoky Mountains. Lower rates, on the order on 10-20 m/My, characterize the Shenandoah, Potomac, and Blue Ridge escarpment areas. There is a significant, positive relationship between basin-scale erosion rates and average basin slope. Steeper basins are in general eroding more rapidly than less steep basins. On the whole, the erosion rates of bedrock outcrops are either lower than or similar to those measured at a basin scale. The average erosion rate for samples of outcropping bedrock collected from the Appalachians is ~15 m/My (n=101). In the Potomac River Basin and the Great Smoky Mountains, bedrock and basin-scale erosion

Global evaluation of erosion rates in relation to tectonics

NASA Astrophysics Data System (ADS)

Hecht, Hagar; Oguchi, Takashi

2017-12-01

Understanding the mechanisms and controlling factors of erosion rates is essential in order to sufficiently comprehend bigger processes such as landscape evolution. For decades, scientists have been researching erosion rates where one of the main objectives was to find the controlling factors. A variety of parameters have been suggested ranging from climate-related, basin morphometry and the tectonic setting of an area. This study focuses on the latter. We use previously published erosion rate data obtained mainly using 10Be and sediment yield and sediment yield data published by the United States Geological Survey. We correlate these data to tectonic-related factors, i.e., distance to tectonic plate boundary, peak ground acceleration ( PGA), and fault distribution. We also examine the relationship between erosion rate and mean basin slope and find significant correlations of erosion rates with distance to tectonic plate boundary, PGA, and slope. The data are binned into high, medium, and low values of each of these parameters and grouped in all combinations. We find that groups with a combination of high PGA (> 0.2.86 g) and long distance (> 1118.69 km) or low PGA (< 0.68 g) and short distance (< 94.34 km) are almost inexistent suggesting a strong coupling between PGA and distance to tectonic plate boundary. Groups with low erosion rates include long distance and/or low PGA, and groups with high erosion rates include neither of these. These observations indicate that tectonics plays a major role in determining erosion rates, which is partly ascribable to steeper slopes produced by active crustal movements. However, our results show no apparent correlation of slope with erosion rates, pointing to problems with using mean basin-wide slope as a slope indicator because it does not represent the complex slope distribution within a basin.

A watershed scale spatially-distributed model for streambank erosion rate driven by channel curvature

NASA Astrophysics Data System (ADS)

McMillan, Mitchell; Hu, Zhiyong

2017-10-01

Streambank erosion is a major source of fluvial sediment, but few large-scale, spatially distributed models exist to quantify streambank erosion rates. We introduce a spatially distributed model for streambank erosion applicable to sinuous, single-thread channels. We argue that such a model can adequately characterize streambank erosion rates, measured at the outsides of bends over a 2-year time period, throughout a large region. The model is based on the widely-used excess-velocity equation and comprised three components: a physics-based hydrodynamic model, a large-scale 1-dimensional model of average monthly discharge, and an empirical bank erodibility parameterization. The hydrodynamic submodel requires inputs of channel centerline, slope, width, depth, friction factor, and a scour factor A; the large-scale watershed submodel utilizes watershed-averaged monthly outputs of the Noah-2.8 land surface model; bank erodibility is based on tree cover and bank height as proxies for root density. The model was calibrated with erosion rates measured in sand-bed streams throughout the northern Gulf of Mexico coastal plain. The calibrated model outperforms a purely empirical model, as well as a model based only on excess velocity, illustrating the utility of combining a physics-based hydrodynamic model with an empirical bank erodibility relationship. The model could be improved by incorporating spatial variability in channel roughness and the hydrodynamic scour factor, which are here assumed constant. A reach-scale application of the model is illustrated on ∼1 km of a medium-sized, mixed forest-pasture stream, where the model identifies streambank erosion hotspots on forested and non-forested bends.

Climate change and mountain-front morphology: Estimating Late Glacial to Holocene erosion rates from the shape of fault-bounded hillslopes

NASA Astrophysics Data System (ADS)

Tucker, G. E.; McCoy, S. W.; Whittaker, A. C.; Roberts, G.; Lancaster, S. T.; Phillips, R. J.

2011-12-01

The existence of well-preserved Holocene bedrock fault scarps along active normal faults in the Mediterranean region and elsewhere suggests a dramatic reduction in rates of rock weathering and erosion that correlates with the transition from glacial to interglacial climate. We test and quantify this interpretation using a case study in the Italian Central Apennines. Holocene rates are derived from measurements of weathering-pit depth along the Magnola scarp, where previous cosmogenic 36Cl analyses constrain exposure history. To estimate the average hillslope erosion rate over ˜105 years, we introduce a simple geometric model of normal-fault footwall slope evolution. The model predicts that the gradient of a weathering-limited footwall hillslope is set by fault dip angle and by the ratio of slip rate to erosion rate; if either slip or erosion rate is known, the other can be derived. Applying this model to the Magnola fault yields an estimated average weathering rate on the order of 0.2-0.4 mm/yr, more than 10x higher than either the Holocene scarp weathering rate or modern regional limestone weathering rates. A numerical model of footwall growth and erosion, in which erosion rate tracks the oxygen-isotope curve, reproduces the main features of hillslope and scarp morphology and suggests that the hillslope erosion rate has varied by about a factor of 30 over the past one to two glacial cycles. We conclude that preservation of carbonate fault scarps reflects strong climatic control on rock breakdown by frost cracking.

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.

Coastal erosion and accretion rates in Greece

NASA Astrophysics Data System (ADS)

Foteinis, Spyros; Papadopoulos, Costas; Koutsogiannaki, Irini; Synolakis, Costas

2010-05-01

Erosion threatens many coastal regions of Greece. Anthropogenic changes of landforms such as coastal roads built on even narrow beaches, sand mining for construction, poor design of coastal structures that interfere with sediment, and dams without sediment bypasses have significantly reduced beach widths. We present erosion rates for different beaches, some of which are in sensitive ecosystems, otherwise "protected" by local and EU ordinances. By comparing inferences of beach widths in varying intervals from 1933 to 2006, we infer that the construction of dams in Acheloos river in western Greece, built in a faraonic attempt to partially divert its flows to eastern Greece, this is responsible for up to 20m/year erosion rates observed in certain locales in the Acheloos delta. More characteristic erosion rates in the region are ~ 2m/year. By contrast, there appears rapid accretion of up to 4m/year in the beaches around the Nestos delta in northern Greece (Papadopoulos, 2009). In beaches that are not near large river deltas, erosion rates range from 0.5m/year to 1m/year. While we have not done comprehensive comparisons among coastlines with different levels of coastal development, it does appear that rapid coastal development correlates well with erosion rates. The underlying problem is the complete lack of any semblance of coastal zone management in Greece and substandard design of coastal structures, which are often sited without any measurements of waves and currents offshore (Synolakis et al, 2008). Beach maintenance remains an exotic concept for most local authorities, who invariably prefer to build hard coastal structures to "protect" versus nourish, siting lack of experience with nourishment and "environmental" concerns. In certain cases, choices are dictated by costs, the larger the cost the easier the project gets approved by regulatory authorities, hence the preference for concrete or rubble structures. We conclude that, unless urgent salvage measures are

Investigation of erosion rates of field samples using FDOT's enhanced sediment erosion rate flume (SERF).

DOT National Transportation Integrated Search

2013-09-01

The first part of this project was to enhance and improve the Florida Department of Transportations : Sediment Erosion Rate Flume (SERF) device. Notable improvements include a pump repair, laser : system enhancement, installation of a digital vide...

Erosion in radial inflow turbines. Volume 4: Erosion rates on internal surfaces

NASA Technical Reports Server (NTRS)

Clevenger, W. B., Jr.; Tabakoff, W.

1975-01-01

An analytic study of the rate at which material is removed by ingested dust impinging on the internal surfaces of a typical radial inflow turbine is presented. Results show that there are several regions which experience very severe erosion loss, and other regions that experience moderate levels of erosion loss: (1) the greatest amount of material loss occurs on the trailing edges of the nozzle blades where very high velocity, moderate angle impacts occur. The tip regions of ductile materials are also subjected to serious levels of erosion loss; (2) moderate amounts of erosion occur near the end of the scroll and on a few of the nozzle blades near this location. Results are presented in the form of surface contours that exist on the scroll and blade surfaces after continuous particulate ingestion with time.

Testing the Control of Mineral Supply Rates on Chemical Erosion Rates in the Klamath Mountains

NASA Astrophysics Data System (ADS)

West, N.; Ferrier, K.

2016-12-01

The relationship between rates of chemical erosion and mineral supply is central to many problems in Earth science, including how tightly Earth's climate should be coupled to tectonics, how strongly nutrient supply to soils and streams depends on soil production, and how much lithology affects landscape evolution. Despite widespread interest in this relationship, there remains no consensus on how closely coupled chemical erosion rates should be to mineral supply rates. To address this, we have established a network of field sites in the Klamath Mountains along a latitudinal transect that spans an expected gradient in mineral supply rates associated with the geodynamic response to the migration of the Mendocino Triple Junction. Here, we present new measurements of regolith geochemistry and topographic analyses that will be compared with cosmogenic 10Be measurements to test hypotheses about supply-limited and kinetically-limited chemical erosion on granodioritic ridgetops. Previous studies in this area suggest a balance between rock uplift rates and basin wide erosion rates, implying the study ridgetops may have adjusted to an approximate steady state. Preliminary data are consistent with a decrease in chemical depletion fraction (CDF) with increasing ridgetop curvature. To the extent that ridgetop curvature reflects ridgetop erosion rates, this implies that chemical erosion rates at these sites are influenced by both mineral supply rates and dissolution kinetics.

Understanding erosion rates in the Himalayan orogen: A case study from the Arun Valley

NASA Astrophysics Data System (ADS)

Olen, Stephanie M.; Bookhagen, Bodo; Hoffmann, Bernd; Sachse, Dirk; Adhikari, D. P.; Strecker, Manfred R.

2015-10-01

Understanding the rates and pattern of erosion is a key aspect of deciphering the impacts of climate and tectonics on landscape evolution. Denudation rates derived from terrestrial cosmogenic nuclides (TCNs) are commonly used to quantify erosion and bridge tectonic (Myr) and climatic (up to several kiloyears) time scales. However, how the processes of erosion in active orogens are ultimately reflected in 10Be TCN samples remains a topic of discussion. We investigate this problem in the Arun Valley of eastern Nepal with 34 new 10Be-derived catchment-mean denudation rates. The Arun Valley is characterized by steep north-south gradients in topography and climate. Locally, denudation rates increase northward, from <0.2 mm yr-1 to ~1.5 mm yr-1 in tributary samples, while main stem samples appear to increase downstream from ~0.2 mm yr-1 at the border with Tibet to 0.91 mm yr-1 in the foreland. Denudation rates most strongly correlate with normalized channel steepness (R2 = 0.67), which has been commonly interpreted to indicate tectonic activity. Significant downstream decrease of 10Be concentration in the main stem Arun suggests that upstream sediment grains are fining to the point that they are operationally excluded from the processed sample. This results in 10Be concentrations and denudation rates that do not uniformly represent the upstream catchment area. We observe strong impacts on 10Be concentrations from local, nonfluvial geomorphic processes, such as glaciation and landsliding coinciding with areas of peak rainfall rates, pointing toward climatic modulation of predominantly tectonically driven denudation rates.

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.

Quantifying thresholds for significant dune erosion along the Sefton Coast, Northwest England

NASA Astrophysics Data System (ADS)

Esteves, Luciana S.; Brown, Jennifer M.; Williams, Jon J.; Lymbery, Graham

2012-03-01

Field and model hindcast data are used to establish a critical dune erosion threshold for the Sefton Coast (NW England). Events are classified as causing significant erosion if they result in: (a) a mean dune retreat along the entire study area of > 2 m; (b) a dune retreat of ≥ 5 m along a coastal segment ≥ 2 km in length; and (c) an eroded area ≥ 20,000 m2. For the period 1996 to 2008, individual storms were characterised using hindcast results from a POLCOMS-WAM model and measured data from the Liverpool Bay Coastal Observatory. Results show that combined extreme surge levels (> 1.5 m) and wave heights (> 4 m), or tidal water levels above 9.0 m Chart Datum (CD), do not always result in significant dune erosion. Evidence suggests that erosion is more likely to occur when wave heights are > 2.6 m, peak water level is > 10.2 m CD at Liverpool and when consecutive tidal cycles provide 10 h or more of water levels above 9.4 m CD. However, lower water levels and wave heights, and shorter events of sustained water levels, can cause significant erosion in the summer. While the return period for events giving rise to the most severe erosion in the winter is > 50 years, significant erosion in the summer can be caused by events with return periods < 1 year. It is suggested that this may be attributable to a known reduction in the mean dune toe elevation c. 30 cm. Although the study shows it might be possible to characterise objectively storm events based on oceanographic conditions, the resultant morphological change at the coast is demonstrated to depend on the time and duration of events, and on other variables which are not so easy to quantify. Further investigation is needed to understand the influence of alongshore and seasonal variability in beach/dune morphology in determining the response to the hydrodynamic and meteorological conditions causing significant erosion. Improved monitoring pre- and post-storm of changes in beach/dune morphology is required to

The economic cost of upland and gully erosion on subsistence agriculture for a watershed in the Ethiopian highlands

USDA-ARS?s Scientific Manuscript database

This paper quantifies the cost of erosion; it uses nutrient replacement cost to value topsoil nutrient depletion, daily wage rate to monetize the opportunity cost of labour due to gully erosion and local market price to quantify the lost animal and cash crop trees. Soil erosion rate is estimated fro...

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.

Internal erosion rates of a 10-kW xenon ion thruster

NASA Technical Reports Server (NTRS)

Rawlin, Vincent K.

1988-01-01

A 30 cm diameter divergent magnetic field ion thruster, developed for mercury operation at 2.7 kW, was modified and operated with xenon propellant at a power level of 10 kW for 567 h to evaluate thruster performance and lifetime. The major differences between this thruster and its baseline configuration were elimination of the three mercury vaporizers, use of a main discharge cathode with a larger orifice, reduction in discharge baffle diameter, and use of an ion accelerating system with larger acceleration grid holes. Grid thickness measurement uncertainties, combined with estimates of the effects of reactive residual facility background gases gave a minimum screen grid lifetime of 7000 h. Discharge cathode orifice erosion rates were measured with three different cathodes with different initial orifice diameters. Three potential problems were identified during the wear test: the upstream side of the discharge baffle eroded at an unacceptable rate; two of the main cathode tubes experienced oxidation, deformation, and failure; and the accelerator grid impingement current was more than an order of magnitude higher than that of the baseline mercury thruster. The charge exchange ion erosion was not quantified in this test. There were no measurable changes in the accelerator grid thickness or the accelerator grid hole diameters.

Using Structure-from-Motion to Quantify Sediment Accumulation and Bedrock Erosion in a Debris-Flow Dominated Channel

NASA Astrophysics Data System (ADS)

Reitman, N. G.; Rengers, F.; Kean, J. W.

2016-12-01

One of the highest frequencies of observed debris flows in the US is located at the Chalk Cliffs in central Colorado. This high rate of debris-flow activity ( 3 per year) is supported by a similarly high rate of sediment supply from rock fall and ravel due to frost weathering of the highly-erodible, hydrothermally-altered quartz monzonite cliffs during the winter months. A first step toward understanding debris-flow initiation, and channel and hillslope evolution, is to quantify the magnitude and spatial distribution of sediment that accumulates by the end of the winter period. Here we test the ability of structure-from-motion photogrammetric surveys to produce high-resolution point clouds in order to quantify sediment deposition, and possibly bedrock erosion. We use point clouds obtained from surveys conducted in late September 2015 and early June 2016 to measure sediment deposition in a 42-m-long channel over one winter. All surveys are co-registered with control points (screws drilled into bedrock) measured in a local coordinate system with a total station. Point clouds derived from these surveys have average point densities >200,000 pts/m2, and accuracies within 2 cm. Initial analysis shows accumulation of 10-50 cm ( 10 m3) of unconsolidated loose sediment over eight months, providing ample material for debris-flow initiation during the following summer season. Sediment accumulated in a spatially-variable pattern dependent on existing channel-bottom bedrock topography. Future surveys are planned in order to measure bedrock erosion by debris flows and variation in sediment deposition rate through time. Our analysis indicates that photogrammetric surveys provide a high level of detail at low cost, and thus are a useful geomorphic monitoring tool that will ultimately lead to better understanding of the processes that contribute to debris-flow activity and landscape evolution.

What can we learn from national-scale geodata describing soil erosion?

NASA Astrophysics Data System (ADS)

Benaud, Pia; Anderson, Karen; Carvalho, Jason; Evans, Martin; Glendell, Miriam; James, Mike; Lark, Murray; Quine, Timothy; Quinton, John; Rawlins, Barry; Rickson, Jane; Truckell, Ian; Brazier, Richard

2017-04-01

The United Kingdom has a rich dataset of soil erosion observations, which have been collected using a wide range of methodologies, across various spatial and temporal scales. Yet, while observations of soil erosion have been carried out along-side agricultural development and intensification, understanding whether or not the UK has a soil erosion problem remains a question to be answered. Furthermore, although good reviews of existing soil erosion rates exist, there is no single resource that brings all of this work together. Therefore, the primary aim of this research was to build a picture of why attempts to quantify erosion rates across the UK empirically have fallen short, through: (1) Collating all available, UK-based and empirically-derived soil erosion datasets into a spatially explicit and open-access database, (2) Developing an understanding of observed magnitudes of erosion, in the UK, (3) Evaluating impact of non-environmental controls on erosion observations i.e. study methodologies, and (4) Exploring trends between environmental controls and erosion rates. To-date, the database holds over 1500 records, which include results from both experimental and natural conditions, across arable, grassland and upland environments. Of the studies contained in the database, erosion has been observed ca. 40% of instances, ranging from <0.01 t.ha-1.yr-1 to 143 t.ha-1.yr-1. However, preliminary analysis has highlighted that over 90% of the studies included in the database only quantify soil loss via visible erosion features, such as rills or gullies, through volumetric assessments. Furthermore, there has been an inherent bias in the UK towards quantifying soil erosion in locations with either a known history or high probability of erosion occurrence. As a consequence, we conclude that such databases, may not be used to make a statistically unbiased assessment of national-scale erosion rates, however, they can highlight maximum likely rates under a wide range of soil

Slow Long-Term Erosion Rates of Banks Peninsula, New Zealand

NASA Astrophysics Data System (ADS)

Dudunake, T.; Nichols, K. K.; Pugsley, E.; Nelson, S.; Colton, J.

2017-12-01

Banks Peninsula, located south of Christchurch, New Zealand, is composed of a multi-aged complex of volcanic centers. The oldest, Lyttelton Volcano is 12 to 10 Ma, and 350 km3. The largest volcano, Akaroa Volcano, is 9 to 8 Ma and 1200 km3. Both of these volcanoes have large embayments (Lyttelton Harbour and Akaroa Harbour) that connect the central volcano (the location of the former volcanic summits) to the ocean. The other eruptive centers, Mt. Herbert ( 9.5 to 8 Ma) and Diamond Harbor (7 to 5.8 Ma), have not eroded to sea level. We used inferred original surfaces and present day topography to calculate the volume of rock eroded from river valleys draining the flanks of Lyttelton (n=11) and Akaroa (n=26) volcanoes and from the large embayments that penetrate the eroding Lyttelton (n=8) and Akaroa (n=25) volcanoes. We used the youngest age of the eruptions as the start of erosion (Lyttelton = 10 Ma and Akaroa = 8 Ma) to determine erosion rates. Preliminary data suggest average erosion rates of 8.2 ± 2.4 m/My (averaged over 10 Ma) on the flanks of Lyttelton Volcano and 12 ± 5.1 m/My (averaged over 8 Ma) on the flanks of Akaroa Volcano. Dating control and formation processes of Lyttelton Harbour and Akaroa Harbour are poorly constrained. The youngest lava flows, Diamond Harbor, are 5.7 Ma and flow into the Lyttelton Harbour embayment. Using endmembers of embayment age for Lyttelton Harbour (10 Ma to 5.7 Ma) the erosion rates range between 18 ± 5.8 m/My and 31 ± 10 m/My. Similarly, the hillslopes of Akaroa Harbour have slow erosion rates (based on endmember ages of 8 Ma and 5.7 Ma) and range between 22 ± 18 and 31 ± 25 m/My. Even the fastest erosion rates on Banks Peninsula are an order of magnitude slower than the erosion rates of other basalt volcanoes in the world's oceans. Using a similar methodology, Tahiti is eroding between 1200 and 2700 m/Ma (Hildenbrand et al., 2008). Other erosion rates, based on sediment yields and water chemistry for La Reunion (400

Erosion rates and landscape evolution of the lowlands of the Upper Paraguay river basin (Brazil) from cosmogenic 10Be

NASA Astrophysics Data System (ADS)

Pupim, Fabiano do Nascimento; Bierman, Paul R.; Assine, Mario Luis; Rood, Dylan H.; Silva, Aguinaldo; Merino, Eder Renato

2015-04-01

The importance of Earth's low sloping areas in regard to global erosion and sediment fluxes has been widely and vigorously debated. It is a crucial area of research to elucidate geologically meaningful rates of land-surface change and thus the speed of element cycling on Earth. However, there are large portions of Earth where erosion rates have not been well or extensively measured, for example, the tropical lowlands. The Cuiabana lowlands are an extensive low-altitude and low-relief dissected metamorphic terrain situated in the Upper Paraguay river basin, central-west Brazil. Besides exposures of highly variable dissected metamorphic rocks, flat residual lateritic caps related to a Late Cenozoic planation surface dominate interfluves of the Cuiabana lowlands. The timescale over which the lowlands evolved and the planation surface developed, and the rate at which they have been modified by erosion, are poorly known. Here, we present measurements of in situ produced cosmogenic 10Be in outcropping metamorphic bedrock and clastic-lateritic caps to quantify rates of erosion of the surface and associated landforms in order to better understand the Quaternary landscape evolution of these lowlands. Overall, slow erosion rates (mean 10 m/Ma) suggest a stable tectonic environment in these lowlands. Erosion rates vary widely between different lithologies (range 0.57 to 28.3 m/Ma) consistent with differential erosion driving regional landform evolution. The lowest erosion rates are associated with the low-relief area (irregular plains), where clastic-laterite (mean 0.67 m/Ma) and quartzite (mean 2.6 m/Ma) crop out, whereas the highest erosion rates are associated with dissection of residual hills, dominated by metasandstone (mean 11.6 m/Ma) and phyllite (mean 27.6 m/Ma). These data imply that the Cuiabana lowland is comprised of two dominant landform sets with distinct and different dynamics. Because the planation surface (mostly lowlands) is lowering and losing mass more

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.

Catchment-scale denudation and chemical erosion rates determined from 10Be and mass balance geochemistry (Mt. Lofty Ranges of South Australia)

NASA Astrophysics Data System (ADS)

Bestland, Erick A.; Liccioli, Caterina; Soloninka, Lesja; Chittleborough, David J.; Fink, David

2016-10-01

Global biogeochemical cycles have, as a central component, estimates of physical and chemical erosion rates. These erosion rates are becoming better quantified by the development of a global database of cosmogenic radionuclide 10Be (CRN) analyses of soil, sediment, and outcrops. Here we report the denudation rates for two small catchments (~ 0.9 km2) in the Mt. Lofty Ranges of South Australia as determined from 10Be concentrations from quartz sand from the following landscape elements: 1) dissected plateaux, or summit surfaces (14.10 ± 1.61 t km- 2 y- 1), 2) sandstone outcrops (15.37 ± 1.32 t km- 2 y- 1), 3) zero-order drainages (27.70 ± 1.42 t km- 2 y- 1), and 4) stream sediment which reflect a mix of landscape elements (19.80 ± 1.01 t km- 2 y- 1). Thus, the more slowly eroding plateaux and ridges, when juxtaposed with the more rapidly eroding side-slopes, are leading to increased relief in this landscape. Chemical erosion rates for this landscape are determined by combining cosmogenic denudation rates with the geochemical mass balance of parent rock, soil and saprolite utilizing zirconium immobility and existing mass balance methods. Two different methods were used to correct for chemical weathering and erosion in the saprolite zone that is shielded at depth from CRN production. The corrected values are higher than uncorrected values: total denudation of 33.24 or 29.11 t km- 2 y- 1, and total chemical erosion of 15.64 or 13.68 t km- 2 y- 1. Thus, according to these methods, 32-40% of the denudation is taking place by chemical weathering and erosion in the saprolite below CRN production depth. Compared with other similar areas, the overall denudation and chemical erosion rates are low. In most areas with sub-humid climates and tectonic uplift, physical erosion is much greater than chemical erosion. The low physical erosion rates in these Mt. Lofty Range catchments, in what is a relatively active tectonic setting, are thought to be due to low rainfall intensity

Absolute Density Calibration Cell for Laser Induced Fluorescence Erosion Rate Measurements

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.; Stevens, Richard E.

2001-01-01

Flight qualification of ion thrusters typically requires testing on the order of 10,000 hours. Extensive knowledge of wear mechanisms and rates is necessary to establish design confidence prior to long duration tests. Consequently, real-time erosion rate measurements offer the potential both to reduce development costs and to enhance knowledge of the dependency of component wear on operating conditions. Several previous studies have used laser-induced fluorescence (LIF) to measure real-time, in situ erosion rates of ion thruster accelerator grids. Those studies provided only relative measurements of the erosion rate. In the present investigation, a molybdenum tube was resistively heated such that the evaporation rate yielded densities within the tube on the order of those expected from accelerator grid erosion. This work examines the suitability of the density cell as an absolute calibration source for LIF measurements, and the intrinsic error was evaluated.

How do subcritical cracking rates and styles influence rock erosion? A test case from the Blue Ridge Mountains of Virginia.

NASA Astrophysics Data System (ADS)

Eppes, M. C.; Hancock, G. S.; Dewers, T. A.; Chen, X.; Eichhubl, P.

2017-12-01

There is a disconnect between measured rates of rock erosion and regolith production and our understanding of the factors and processes that drive them. Here we examine the mechanical weathering (cracking) characteristics of natural, bare bedrock outcrops characterized by 10Be derived erosion rates that vary from 2 to 40 m/my in the Blue Ridge Mountains, VA. Observed erosion rate variance generally correlates with rock type; we seek to characterize and quantify to what extent the mechanical weathering properties of the different rock types drive erosion rates. We assert that subcritical cracking constitutes the primary mechanism by which the outcrops increase their porosity and subsequently weather and erode. We therefore hypothesize that rock parameters that control rates and styles of subcritical cracking set the outcrop erosion rates. For each outcrop, we measured crack characteristics along transects: for every crack >2 cm length, we measured its length, width, orientation, and weathering characteristics (rounded vs sharp edges); and we measured the thickness of all `steps' (spallation remnants) encountered in the transects. For most outcrops, we collected surface samples in order to characterize their mineralogy and microcracking characteristics through thin section analysis. For each rock type, we collected samples for which we measured fracture toughness, as well as the subcritical crack growth index under different moisture conditions. Preliminary analysis of the field crack data indicates that each rock type (granite, sandstone, quartzite) is characterized by unique macro- and micro-scale crack characteristics consistent with known generic subcritical cracking parameters for those rocks. Crack density and length correlate with erosion rates in faster eroding rock types, but not slowly eroding ones. Overall, we hope these data will help to shed light on the driving and limiting factors for the mechanical production of porosity in rock at and near Earth

Comparing Background and Recent Erosion Rates in Degraded Areas of Southeastern Brazil

NASA Astrophysics Data System (ADS)

Fernandes, N.; Bierman, P. R.; Sosa-Gonzalez, V.; Rood, D. H.; Fontes, R. L.; Santos, A. C.; Godoy, J. M.; Bhering, S.

2014-12-01

Soil erosion is a major problem in northwestern Rio de Janeiro State where, during the last three centuries, major land-use changes took place, associated with the replacement of the original rainforest by agriculture and grazing. The combination of steep hillslopes, erodible soils, sparse vegetation, natural and human-induced fires, as well as downslope ploughing, led to an increase in surface runoff and surface erosion on soil-mantled hillslopes; together, these actions and responses caused a decline in soil productivity. In order to estimate changes in erosion rates over time, we compared erosion rates measured at different spatial and temporal scales, both background (natural) and short-term (human-induced during last few decades). Background long-term erosion rates were measured using in-situ produced cosmogenic 10Be in the sand fraction quartz of active river channel sediment in four basins in the northwestern portion of Rio de Janeiro State. In these basins, average annual precipitation varies from 1,200 to 1,300 mm, while drainage areas vary from 15 to 7,200 km2. Short-term erosion rates were measured in one of these basins from fallout 210Pb in soil samples collected along a hillslope transect located in an abandoned agriculture field. In this transect, 190 undisturbed soil samples (three replicates) were collected from the surface to 0.50 m depth (5 cm vertical intervals) in six soil pits. 10Be average background, basin-wide, erosion rates in the area are ~ 13 m/My; over the last decades, time-integrated (210Pb) average hillslope erosion rates are around 1450 m/Myr, with maximum values at the steepest portion of convex hillslopes of about 2000 m/Myr. These results suggest that recent hillslope erosion rates are about 2 orders of magnitude above background rates of sediment generation integrated over many millennia. This unsustainable rate of soil loss has severely decreased soil productivity eventually leading to the abandonment of farming activities in

Reassessment of soil erosion on the Chinese loess plateau: were rates overestimated?

NASA Astrophysics Data System (ADS)

Zhao, Jianlin; Govers, Gerard

2014-05-01

Several studies have estimated regional soil erosion rates (rill and interrill erosion) on the Chinese loess plateau using an erosion model such as the RUSLE (e.g. Fu et al., 2011; Sun et al., 2013). However, the question may be asked whether such estimates are realistic: studies have shown that the use of models for large areas may lead to significant overestimations (Quinton et al., 2010). In this study, soil erosion rates on the Chinese loess plateau were reevaluated by using field measured soil erosion data from erosion plots (216 plots and 1380 plot years) in combination with a careful extrapolation procedure. Data analysis showed that the relationship between slope and erosion rate on arable land could be well described by erosion-slope relationships reported in the literature (Nearing, 1997). The increase of average erosion rate with slope length was clearly degressive, as could be expected from earlier research. However, for plots with permanent vegetation (grassland, shrub, forest) no relationship was found between erosion rates and slope gradient and/or slope length. This is important, as it implies that spatial variations of erosion on permanently vegetated areas cannot be modeled using topographical functions derived from observations on arable land. Application of relationships developed for arable land will lead to a significant overestimation of soil erosion rates. Based on our analysis we estimate the total soil erosion rate in the Chinese Loess plateau averages ca. 6.78 t ha-1 yr-1 for the whole loess plateau, resulting in a total sediment mobilisation of ca. 0.38 Gt yr-1. Erosion rates on arable land average ca. 15.10 t ha-1 yr-1. These estimates are 2 to 3 times lower than previously published estimates. The main reason why previous estimates are likely to be too high is that the values of (R)USLE parameters such as K, P and LS factor were overestimated. Overestimations of the K factor are due to the reliance of nomograph calculations, resulting

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

Quantifying streambank erosion: a comparative study using an unmanned aerial system (UAS) and a terrestrial laser scanner

NASA Astrophysics Data System (ADS)

Rizzo, D.; Hamshaw, S. D.; Dewoolkar, M.; ONeil-Dunne, J.; Frolik, J.; Bryce, T. G.; Waldron, A. Y.

2015-12-01

Streambank erosion is a common non-point source contributing to suspended sediment and nutrient loading of waterways, and recently has been estimated to account for 30-80% of sediment loading into receiving waters. There is interest in developing reliable methods to quantify bank erosion in watersheds, so effective management strategies can be devised. However, current methods can be either cost prohibitive or unreliable. Direct measurement approaches (surveys and erosion pins) are labor intensive and yield site-specific measurements that are limited for extrapolation to larger scales. Similar issues arise with analytical methods such as slope stability analysis, which require material parameters that are resource intensive to determine. Newer approaches such as use of aerial LiDAR data have proved effective for watershed level assessment, but come with long turnaround times and high cost. Terrestrial laser scanning (TLS) is also effective and offers high accuracy, however collection over large areas is impractical and post-processing is labor intensive. New technology in the form of unmanned aerial systems (UAS) has the potential to significantly enhance the ability to monitor channel migration and quantify bank erosion at variable scales. In this study, 20 km of the Mad and Winooski Rivers in Vermont were flown using a senseFly eBee UAS. Flights were made in spring and fall 2015 in leaf-off conditions with selected portions also flown after large storms in the summer. Change in bank profiles between spring and fall flights provide a comprehensive estimate of bank erosion along the study reaches. Six sites with varying bank heights, erosion sensitivity, and vegetation conditions were selected for simultaneous surveying using a TLS. Point cloud data from both the TLS and UAS were compared to assess the accuracy of the UAS for capturing the bank profile. Changes in bank cross-sections and in volumes calculated from 3D digital surface models were used to compare the

Catchment-wide weathering and erosion rates of mafic, ultramafic, and granitic rock from cosmogenic meteoric 10Be/9Be ratios

NASA Astrophysics Data System (ADS)

Dannhaus, N.; Wittmann, H.; Krám, P.; Christl, M.; von Blanckenburg, F.

2018-02-01

Quantifying rates of weathering and erosion of mafic rocks is essential for estimating changes to the oceans alkalinity budget that plays a significant role in regulating atmospheric CO2 levels. In this study, we present catchment-wide rates of weathering, erosion, and denudation measured with cosmogenic nuclides in mafic and ultramafic rock. We use the ratio of the meteoric cosmogenic nuclide 10Be, deposited from the atmosphere onto the weathering zone, to stable 9Be, a trace metal released by silicate weathering. We tested this approach in stream sediment and water from three upland forested catchments in the north-west Czech Republic. The catchments are underlain by felsic (granite), mafic (amphibolite) and ultramafic (serpentinite) lithologies. Due to acid rain deposition in the 20th century, the waters in the granite catchment exhibit acidic pH, whereas waters in the mafic catchments exhibit neutral to alkaline pH values due to their acid buffering capability. The atmospheric depositional 10Be flux is estimated to be balanced with the streams' dissolved and particulate meteoric 10Be export flux to within a factor of two. We suggest a correlation method to derive bedrock Be concentrations, required as an input parameter, which are highly heterogeneous in these small catchments. Derived Earth surface metrics comprise (1) Denudation rates calculated from the 10Be/9Be ratio of the "reactive" Be (meaning sorbed to mineral surfaces) range between 110 and 185 t km-2 y-1 (40 and 70 mm ky-1). These rates are similar to denudation rates we obtained from in situ-cosmogenic 10Be in quartz minerals present in the bedrock or in quartz veins in the felsic and the mafic catchment. (2) The degree of weathering, calculated from the fraction of 9Be released from primary minerals as a new proxy, is about 40-50% in the mafic catchments, and 10% in the granitic catchment. Lastly, (3) erosion rates were calculated from 10Be concentrations in river sediment and corrected for sorting

The Roles of Tectonics and Climate in Driving Erosion Rates in the Eastern Himalaya

NASA Astrophysics Data System (ADS)

Larsen, I. J.; Montgomery, D.; Stone, J. O.

2016-12-01

Landslide erosion governs the flux of sediment from non-glaciated mountains. Hence patterns in landslide erosion rates have the potential to reveal how such landscapes respond to spatially-varying climatic and tectonic forcing. Across strong spatial gradients in precipitation and exhumation rates in the eastern Himalaya, we mapped 27,611 landslides and measured 10Be in river sediment in a swath spanning from the Himalayan mountain front northward to the Yarlung Tsangpo Gorge. For the entire landscape, landslide erosion and 10Be-based denudation rates are not correlated with mean annual precipitation. However, erosion and denudation rates increase non-linearly as a function of mean hillslope angles, which is diagnostic of tectonic-driven landslide erosion on threshold hillslopes. Dividing the landscape into distinct geologic-tectonic terranes reveals that erosion rates scale positively with both mean hillslope angles and exhumation rates, but also that threshold topography has not developed throughout the region. Mean annual precipitation rates range from 0.5 to 3 m across the terranes, and erosion rates are highest in the relatively dry Yarlung Tsangpo Gorge, which receives 1.5 m of precipitation annually. However, for areas south of the Gorge, where moisture sources from the south first interact with the orographic barrier of the Himalaya, there is a modest linear increase in erosion rate with increasing mean annual rainfall. These results indicate that tectonics is the main control on spatial patterns of erosion in the eastern Himalaya, but that climate may play a modulating role. Hence the relative roles tectonics and climate play in driving erosion rates likely vary at the sub-orogen scale.

Can control of soil erosion mitigate water pollution by sediments?

PubMed

Rickson, R J

2014-01-15

The detrimental impact of sediment and associated pollutants on water quality is widely acknowledged, with many watercourses in the UK failing to meet the standard of 'good ecological status'. Catchment sediment budgets show that hill slope erosion processes can be significant sources of waterborne sediment, with rates of erosion likely to increase given predicted future weather patterns. However, linking on-site erosion rates with off-site impacts is complicated because of the limited data on soil erosion rates in the UK and the dynamic nature of the source-pathway-receptor continuum over space and time. Even so, soil erosion control measures are designed to reduce sediment production (source) and mobilisation/transport (pathway) on hill slopes, with consequent mitigation of pollution incidents in watercourses (receptors). The purpose of this paper is to review the scientific evidence of the effectiveness of erosion control measures used in the UK to reduce sediment loads of hill slope origin in watercourses. Although over 73 soil erosion mitigation measures have been identified from the literature, empirical data on erosion control effectiveness are limited. Baseline comparisons for the 18 measures where data do exist reveal erosion control effectiveness is highly variable over time and between study locations. Given the limitations of the evidence base in terms of geographical coverage and duration of monitoring, performance of the different measures cannot be extrapolated to other areas. This uncertainty in effectiveness has implications for implementing erosion/sediment risk reduction policies, where quantified targets are stipulated, as is the case in the EU Freshwater Fish and draft Soil Framework Directives. Also, demonstrating technical effectiveness of erosion control measures alone will not encourage uptake by land managers: quantifying the costs and benefits of adopting erosion mitigation is equally important, but these are uncertain and difficult to

Dust and chemical erosion biases in cosmogenic nuclide studies: A factor-of-ten problem that could mask strong climatic effects on landscape evolution

NASA Astrophysics Data System (ADS)

Riebe, C. S.; Arvin, L.; Ferrier, K.; Aciego, S.

2017-12-01

Cosmogenic nuclides have been widely used to quantify erosion in mountain ranges around the world, creating a global database of erosion rates from climatically and lithologically diverse sites, and providing vital clues about how mountain landscape evolution is coupled to Earth's carbon cycle and thus global climate change over geologic timescales. Despite this wealth of data, few studies have observed the widely expected strong control of erosion rates by climatic factors such as precipitation and temperature. Here we show that cosmogenic nuclide studies are prone to biases due to dust deposition and chemical erosion, which together can obscure strong relationships between climate and erosion rates. Erosion rates of sites exposed to intense chemical weathering can be underestimated by two-fold due to chemical enrichment of the cosmogenic target mineral quartz — a result of its high chemical erosion resistance, which increases its residence time and thus reduces its apparent erosion rate compared to other soil minerals. Meanwhile, erosion rates of sites with rapid dust deposition can be overestimated by more than ten-fold, due to dust's contributions to soil mass and target mineral abundance. Compilations of dust fluxes and cosmogenic nuclide data suggest that steep climatic trends in erosion rates, ranging from slow erosion rates in dry settings to twenty-fold faster erosion rates in wet settings, could be largely masked by the combined effects of dust deposition and chemical erosion. We argue that these effects need to be quantified in many cosmogenic nuclide studies of erosion rates. Doing so will require dust input rates; soil depth and density; quartz-enrichment ratios in both saprolite relative to bedrock and soil relative to saprolite; and quartz concentrations in deposited dust. Failure to quantify these crucial parameters can lead to misinterpretation of the strength — and even the sign — of feedbacks between climate and erosion rates in mountain

Hillslope-channel coupling in a steep Hawaiian catchment accelerates erosion rates over 100-fold

NASA Astrophysics Data System (ADS)

Stock, J. D.; Hanshaw, M. N.; Rosener, M.; Schmidt, K. M.; Brooks, B. A.; Tribble, G.; Jacobi, J.

2009-12-01

In tropical watersheds, hillslope changes are producing increasing amounts of fine sediment that can be quickly carried to reefs by channels. Suspended sediment concentrations off the reefs of Molokai, Hawaii, chronically exceed a toxic level of 10 mg/L, threatening reef ecosystems. We hypothesize that historic conversion of watersheds from soil creep to overland flow erosion increased both magnitude and frequency of sediment flooding adjacent reefs. We combined surficial and ecological mapping, hillslope and stream gages, and novel sensors to locate, quantify and model the generation of fine sediments polluting the Molokai reef. Ecological and geomorphic mapping from LiDAR and multi-spectral imagery located a subset of overland flow areas with vegetation cover below a threshold value preventing erosion. Here, feral goat grazing exposed cohesive volcanic soils whose low matrix hydraulic conductivities (1-20 mm/hour) promote Horton overland flow erosion. We instrumented steep, barren hillslopes with soil moisture sensors, overland flow meters, Parshall flumes, ISCO sediment samplers, and a rain gage and conducted repeat Tripod LiDAR and infiltration tests. To characterize soil resistance here and elsewhere to overland flow erosion, we deployed a Cohesive Strength Meter (CSM) to simulate the stresses of flowing water. At the 13.5 km 2 watershed mouth we used a USGS stream gage and ISCO sediment sampler to estimate total load. Over 2 years, storms triggered overland flow during rainfall intensities above 10-15 mm/hr. Overland flow meters indicate such flows can be up to 3 cm deep, with a tendency to deepen downslope. CSM tests indicate that these depths are insufficient to erode soils where vegetation is dense, but far above threshold values of 2-3 mm depth for bare soil erosion. Sediment ratings curves for both hillslope and downstream catchment gages show strong clock-wise hysteresis during the first intense storms in the Fall, becoming linear later in the rainy

Testing the control of mineral supply rates on chemical erosion in the Klamath Mountains

NASA Astrophysics Data System (ADS)

West, N.; Ferrier, K.

2017-12-01

The relationship between rates of chemical erosion and mineral supply is central to many problems in Earth science, including the role of tectonics in the global carbon cycle, nutrient supply to soils and streams via soil production, and lithologic controls on landscape evolution. We aim to test the relationship between mineral supply rates and chemical erosion in the forested uplands of the Klamath mountains, along a latitudinal transect of granodioritic plutons that spans an expected gradient in mineral supply rates associated with the geodynamic response to the migration of the Mendocino Triple Junction. We present 10Be-derived erosion rates and Zr-derived chemical depletion factors, as well as bulk soil and rock geochemistry on 10 ridgetops along the transect to test hypotheses about supply-limited and kinetically-limited chemical erosion. Previous studies in this area, comparing basin-averaged erosion rates and modeled uplift rates, suggest this region may be adjusted to an approximate steady state. Our preliminary results suggest that chemical erosion at these sites is influenced by both mineral supply rates and dissolution kinetics.

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

Modern erosion rates and loss of coastal features and sites, Beaufort Sea coastline, Alaska

USGS Publications Warehouse

Jones, Benjamin M.; Hinkel, Kenneth M.; Arp, C.D.; Eisner, Wendy R.

2008-01-01

This study presents modern erosion rate measurements based upon vertical aerial photography captured in 1955, 1979, and 2002 for a 100 km segment of the Beaufort Sea coastline. Annual erosion rates from 1955 to 2002 averaged 5.6 m a-1. However, mean erosion rates increased from 5.0 m a-1 in 1955-79 to 6.2 m a-1 in 1979-2002. Furthermore, from the first period to the second, erosion rates increased at 60% (598) of the 992 sites analyzed, decreased at 31% (307), and changed less than ?? 30 cm at 9% (87). Historical observations and quantitative studies over the past 175 years allowed us to place our erosion rate measurements into a longer-term context. Several of the coastal features along this stretch of coastline received Western place names during the Dease and Simpson expedition in 1837, and the majority of those features had been lost by the early 1900s as a result of coastline erosion, suggesting that erosion has been active over at least the historical record. Incorporation of historical and modern observations also allowed us to detect the loss of both cultural and historical sites and modern infrastructure. U.S. Geological Survey topographic maps reveal a number of known cultural and historical sites, as well as sites with modern infrastructure constructed as recently as the 1950s, that had disappeared by the early 2000s as a result of coastal erosion. We were also able to identify sites that are currently being threatened by an encroaching coastline. Our modern erosion rate measurements can potentially be used to predict when a historical site or modern infrastructure will be affected if such erosion rates persist. ?? The Arctic Institute of North America.

The influence of basal-ice debris on patterns and rates of glacial erosion

NASA Astrophysics Data System (ADS)

Ugelvig, Sofie V.; Egholm, David L.

2018-05-01

Glaciers have played a key role for shaping much of Earth's high topography during the cold periods of the Late Cenozoic. However, despite of their distinct influence on landscapes, the mechanisms of glacial erosion, and the properties that determine their rate of operation, are still poorly understood. Theoretical models of subglacial erosion generally highlight the influence of basal sliding in setting the pace of erosion, but they also point to a strong influence of other subglacial properties, such as effective bed pressure and basal-ice debris concentration. The latter properties are, however, not easily measured in existing glaciers, and hence their influence cannot readily be confirmed by observations. In order to better connect theoretical models for erosion to measurable properties in glaciers, we used computational landscape evolution experiments to study the expected influence of basal-ice debris concentration for subglacial abrasion at the scale of glaciers. The computational experiments couple the two erosion processes of quarrying and abrasion, and furthermore integrate the flow of ice and transport of debris within the ice, thus allowing for the study of dynamic feedbacks between subglacial erosion and systematic glacier-scale variations in basal-ice debris concentration. The experiments explored several physics-based models for glacial erosion, in combination with different models for basal sliding to elucidate the relationship between sliding speed, erosion rate and basal-ice debris concentration. The results demonstrate how differences in debris concentration can explain large variations in measured rates. The experiments also provide a simple explanation for the observed dependence of glacier-averaged rate of erosion on glacier size: that large glacier uplands feed more debris into their lower-elevation parts, thereby strengthening their erosive power.

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.

Can post-fire erosion rates be estimated using a novel plastic optical fibre turbidity sensor?

NASA Astrophysics Data System (ADS)

Keizer, Jan Jacob; Bilro, Lúcia; Martins, Martinho M. A.; Machado, Ana Isabel; Karine Boulet, Anne; Vieira, Diana C. S.; Sequeira, Filipa; Prats, Sergio A.; Nogueira, Rogério

2014-05-01

It is well-established that wildfires can play an important role in the hydrological and erosion response of forested catchments, substantially increasing overland as well as stream flow and associated sediment yield during the earlier stages of the window-of-disturbance. Even so, it continues a major challenge to quantify post-fire erosion rates and their evolution with time-since-fire, both for plot and catchment outlets. This constraint could to some extent be overcome by low-cost turbidity sensors, placed in runoff collection tanks and at multiple points across stream flow sections. Plastic optical fibre turbidity sensors (POF) have, in that respect, much potential, due to their reduced costs, suitability for multiplexing and robustness under adverse monitoring conditions. The present study explores this potential for recently burnt areas, where the characteristics of the transported sediments can be expected to change markedly over time due to exhaustion of ashes. To this end, a large number of plot- and catchment-scale runoff samples were studied that had been collected in the course of 1- to 2-weekly field monitoring of a recently burnt study area in north-central Portugal. Comparison of the sediment and organic matter contents of these samples with turbidity readings obtained with a novel POF sensor suggested that the POF sensor would greatly facilitate obtaining rough estimates of post-fire erosion rates but would not dispense of regular calibration under changing sediment load characteristics.

Integrating river incision rates over timescales in the Ecuadorian Andes: from uplift history to current erosion rates

NASA Astrophysics Data System (ADS)

Campforts, Benjamin; Govers, Gerard; Vanacker, Veerle; Tenorio, Gustavo

2013-04-01

River profile development is studied at different timescales, from the response to uplift over millions of years over steady state erosion rates over millennia to the response to a single event, such as a major landslide. At present, few attempts have been made to compare data obtained over various timescales. Therefore we do not know to what extent data and model results are compatible: do long-term river profile development models yield erosion rates that are compatible with information obtained over shorter time spans, both in terms of absolute rates and spatial patterns or not? Such comparisons could provide crucial insights into the nature of river development and allow us to assess the confidence we may have when predicting river response at different timescales (e.g. Kirchner et al., 2001). A major issue hampering such comparison is the uncertainty involved in the calibration of long-term river profile development models. Furthermore, calibration data on different timescales are rarely available for a specific region. In this research, we set up a river profile development model similar to the one used by Roberts & White (2010) and successfully calibrated it for the northern Ecuadorian Andes using detailed uplift and sedimentological data. Subsequently we used the calibrated model to simulate river profile development in the southern Ecuadorian Andes. The calibrated model allows to reconstruct the Andean uplift history in southern Ecuador, which is characterized by a very strong uplift phase during the last 5 My. Erosion rates derived from the modeled river incision rates were then compared with 10Be derived basin-wide erosion rates for a series of basins within the study area. We found that the model-inferred erosion rates for the last millennia are broadly compatible with the cosmogenic derived denudation rates, both in terms of absolute erosion rates as well as in terms of their spatial distribution. Hence, a relatively simple river profile development

In-situ real time measurements of net erosion rates of copper during hydrogen plasma exposure

NASA Astrophysics Data System (ADS)

Kesler, Leigh; Wright, Graham; Peterson, Ethan; Whyte, Dennis

2013-10-01

In order to properly understand the dynamics of net erosion/deposition in fusion reactors, such as tokamaks, a diagnostic measuring the real time rates of net erosion/deposition during plasma exposure is necessary. The DIONISOS experiment produces real time measurements of net erosion/deposition by using Rutherford backscattering spectroscopy (RBS) ion beam analysis simultaneously with plasma exposure from a helicon plasma source. This in-situ method improves on ex-situ weight loss measurements by allowing measurement of possible synergistic effects of high ion implantation rates and net erosion rate and by giving a real time response to changes in plasma parameters. Previous work has validated this new technique for measuring copper (Cu) erosion from helium (He) plasma ion bombardment. This technique is now extended to measure copper erosion due to deuterium and hydrogen plasma ion exposure. Targets used were a 1.5 μm Cu layer on an aluminum substrate. Cu layer thickness is tracked in real time using 1.2 MeV proton RBS. Measured erosion rates will be compared to results from literature and He erosion rates. Supported by US DoE award DE-SC00-02060.

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.

A closer look at the Neogene erosion and accumulation rate increase

NASA Astrophysics Data System (ADS)

Willenbring, J.; von Blanckenburg, F.

2008-12-01

Glacial erosion and Quaternary cold-stage warm-stage climate cycling have been cited as mechanisms to explain observations of increased Neogene marine sedimentation rates. Quantification of long-term glacial erosion rates from cosmogenic radionuclides from large areas mostly covered by cold-based ice during the Quaternary show very low erosion rates over several glacial cycles. In addition, isotope ratio proxies of dissolved metals in seawater, measured in chemical ocean sediments, lack clear evidence for an increase in terrigenous denudation. In particular, the stable isotope 9Be, derived from continental erosion, shows no change in its ratio to meteoric cosmogenic nuclide 10Be, derived from rain over the past 10 My. Radiogenic Pb and Nd isotopes, mainly show a change in the style of denudation from more chemical to more physical processes in the Quaternary. These data are at odds with a suggested increase in marine sedimentation rates during the late Cenozoic. In order to resolve this contradiction we have scrutinized these sedimentation rate calculations from ocean cores to identify whether they might show only apparent increases in the Neogene sections. Potential explanations are that in some cases, measured sediment thicknesses for different time intervals lack corrections for sediment compaction. Compaction of the lower portions of the cores drastically increases the apparent thickness of the more recent (Quaternary) sediment. In addition, sedimentation rates often only appear higher for recent sections in cores due to an artifact of an averaging timescale that decreases up-core. Such an averaging time scale decrease arises from better chronological resolution in recent times (Sadler et al., 1999). Cannibalization of older sediment might add to this effect. Together, these data question a clear, global-scale Quaternary climate-erosion connection that would be unique in Earth's history.

Wind driven erosion and the effects of particulate electrification

NASA Astrophysics Data System (ADS)

Merrison, J. P.; Bak, E.; Finster, K.; Gunnlaugsson, H. P.; Holstein-Rathlou, C.; Knak Jensen, S.; Nørnberg, P.; Rasmussen, K. R.

2012-09-01

Several related aspects of Aeolian activity are presently being studied in the laboratory, the most recent advances in this field will be presented. These include simulating wind driven erosion in the laboratory, quantifying erosion rates and the study of mineral change due to mechanical activation. Also advances in our understanding of the electrification of sand/dust particles is being made and how this phenomenon affects their behavior.

A Bayesian Hierarchical Modeling Scheme for Estimating Erosion Rates Under Current Climate Conditions

NASA Astrophysics Data System (ADS)

Lowman, L.; Barros, A. P.

2014-12-01

Computational modeling of surface erosion processes is inherently difficult because of the four-dimensional nature of the problem and the multiple temporal and spatial scales that govern individual mechanisms. Landscapes are modified via surface and fluvial erosion and exhumation, each of which takes place over a range of time scales. Traditional field measurements of erosion/exhumation rates are scale dependent, often valid for a single point-wise location or averaging over large aerial extents and periods with intense and mild erosion. We present a method of remotely estimating erosion rates using a Bayesian hierarchical model based upon the stream power erosion law (SPEL). A Bayesian approach allows for estimating erosion rates using the deterministic relationship given by the SPEL and data on channel slopes and precipitation at the basin and sub-basin scale. The spatial scale associated with this framework is the elevation class, where each class is characterized by distinct morphologic behavior observed through different modes in the distribution of basin outlet elevations. Interestingly, the distributions of first-order outlets are similar in shape and extent to the distribution of precipitation events (i.e. individual storms) over a 14-year period between 1998-2011. We demonstrate an application of the Bayesian hierarchical modeling framework for five basins and one intermontane basin located in the central Andes between 5S and 20S. Using remotely sensed data of current annual precipitation rates from the Tropical Rainfall Measuring Mission (TRMM) and topography from a high resolution (3 arc-seconds) digital elevation map (DEM), our erosion rate estimates are consistent with decadal-scale estimates based on landslide mapping and sediment flux observations and 1-2 orders of magnitude larger than most millennial and million year timescale estimates from thermochronology and cosmogenic nuclides.

Responses of chemical erosion rates to transient perturbations in physical erosion rates, and implications for relationships between chemical and physical erosion rates in regolith-mantled hillslopes

NASA Astrophysics Data System (ADS)

Ferrier, Ken L.; West, Nicole

2017-09-01

Understanding the relationship between chemical erosion rates (W) and physical erosion rates (E) is of wide interest due to their roles in driving landscape evolution, supplying nutrients to soils and streams, and modulating the global carbon cycle. Measured relationships between W and E vary around the globe, with some regions exhibiting positive correlations between W and E, some negative correlations, and others no correlation within uncertainty. Here we use a numerical model for mineral weathering in well-mixed ridgetop regolith to explore how complex W- E relationships can be generated by simple transient perturbations in E. We show that a Gaussian perturbation in E can produce positive or negative responses in W, and can result in a variety of hysteresis loops - clockwise, counterclockwise, or figure-eight - in plots of W against E. The nature of the transient response depends on the shape of the steady-state W- E relationship, which is set by regolith mineralogy, and the ratio of E to the maximum possible regolith production rate. The response time of W is controlled by the response time of soluble mineral concentrations at low E, where soluble mineral concentrations are low, and by the response time of regolith thickness at high E, where regolith thickness is low. These complex W- E relationships arise in the absence of variations in climate and lithology, which suggests that transients may account for some of the observed differences in W- E relationships among field sites, even among sites that share the same climate and lithology.

Rate estimates for lateral bedrock erosion based on radiocarbon ages, Duck River, Tennessee

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

Brakenridge, G.R.

Rates of bedrock erosion in ingrown meandering rivers can be inferred from the location of buried relict flood-plain and river-bank surfaces, associated paleosols, and radiocarbon dates. Two independent methods are used to evaluate the long-term rates of limestone bedrock erosion by the Duck River. Radiocarbon dates on samples retrieved from buried Holocene flood-plain and bank surfaces indicate lateral migration of the river bank at average rates of 0.6-1.9 m/100 yr. Such rates agree with lateral bedrock cliff erosion rates of 0.5-1.4 m/100 yr, as determined from a comparison of late Pleistocene and modern bedrock cliff and terrace scarp positions. Thesemore » results show that lateral bedrock erosion by this river could have occurred coevally with flood-plain and terrace formation and that the resulting evolution of valley meander bends carved into bedrock is similar in many respects to that of channel meanders cut into alluvium. 11 references, 5 figures.« less

Erosion of Earthen Levees by Wave Action

NASA Astrophysics Data System (ADS)

Ozeren, Y.; Wren, D. G.; Reba, M. L.

2016-02-01

Earthen levees of aquaculture and irrigation reservoirs in the United States often experience significant erosion due to wind-generated waves. Typically constructed using local soils, unprotected levees are subjected to rapid erosion and retreat due to wind generated waves and surface runoff. Only a limited amount of published work addresses the erosion rates for unprotected levees, and producers who rely on irrigation reservoirs need an economic basis for selecting a protection method for vulnerable levees. This, in turn, means that a relationship between wave energy and erosion of cohesive soils is needed. In this study, laboratory experiments were carried out in order to quantify wave induced levee erosion and retreat. A model erodible bank was packed using a soil consisting of approximately 14% sand, 73% silt, and 13% clay in a 20.6 m long 0.7 m wide and 1.2 m deep wave tank at the USDA-ARS, National Sedimentation Laboratory in Oxford MS. The geometry of the levee face was monitored by digital camera and the waves were measured by means of 6 capacitance wave staffs. Relationships were established between levee erosion, edge and retreat rates, and incident wave energy.

Modelling Deposition and Erosion rates with RadioNuclides (MODERN) - Part 2: A comparison of different models to convert 239+240Pu inventories into soil redistribution rates at unploughed sites.

PubMed

Arata, Laura; Alewell, Christine; Frenkel, Elena; A'Campo-Neuen, Annette; Iurian, Andra-Rada; Ketterer, Michael E; Mabit, Lionel; Meusburger, Katrin

2016-10-01

Sheet erosion is one of the major threats to alpine soils. To quantify its role and impact in the degradation processes of alpine grasslands, the application of Fallout Radionuclides (FRN) showed very promising results. The specific characteristics of plutonium 239 + 240 ( 239+240 Pu), such as the homogeneous fallout distribution, the long half-life and the cost and time effective measurements make this tracer application for investigating soil degradation in Alpine grasslands more suitable than any other FRN (e.g. 137 Cs). However, the conversion of 239+240 Pu inventories into soil erosion rates remains a challenge. Currently available conversion models have been developed mainly for 137 Cs with later adaptation to other FRN (e.g. Excess 210 Pb, and 7 Be), each model being defined for specific land use (ploughed and/or unploughed) and processes (erosion or deposition). As such, they may fail in describing correctly the distribution of Pu isotopes in the soil. A new conversion model, MODERN, with an adaptable algorithm to estimate erosion and deposition rates from any FRN inventory changes was recently proposed (Arata et al., 2016). In this complementary contribution, the authors compare the application of MODERN to other available conversion models. The results show a good agreement between soil redistribution rates obtained from MODERN and from the models currently used by the FRN scientific community (i.e. the Inventory Method). Copyright © 2016 The Authors. Published by Elsevier Ltd.. All rights reserved.

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.

Estimating Sedimentation from an Erosion-Hazard Rating

Treesearch

R.M. Rice; S.A. Sherbin

1977-01-01

Data from two watersheds in northern California were used to develop an interpretation of the erosion hazard rating (EHR) of the Coast Forest District as amount of sedimentation. For the Caspar Creek Experimental Watershed (North Fork and South Fork), each EHR unit was estimated as equivalent to 0.0543 cubic yards per acre per year, on undisturbed forest. Experience...

Estimating sedimentation from an erosion-hazard rating

Treesearch

R. M. Rice; S. A. Sherbin

1977-01-01

Data from two watersheds in northern California were used to develop an interpretation of the erosion-hazard rating (EHR) of the Coast Forest District as amount of sedimentation. For the Caspar Creek Experimental Watershed (North Fork and South Fork), each EHR unit was estimated as equivalent to 0.0543 cubic yards per acre per year, on undisturbed forest. Experience...

AERO: A decision support tool for wind erosion assessment in rangelands and croplands

USDA-ARS?s Scientific Manuscript database

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 identify...

Dental erosion and salivary flow rate in cerebral palsy individuals with gastroesophageal reflux.

PubMed

Guaré, Renata O; Ferreira, Maria C D; Leite, Mariana F; Rodrigues, Jonas A; Lussi, Adrian; Santos, Maria T B R

2012-05-01

A high prevalence of gastroesophageal reflux (GERD) has been observed in individuals with cerebral palsy (CP). One of the main risks for dental erosion is GERD. This study aimed to evaluate the presence of GERD, variables related to dental erosion and associated with GERD (diet consumption, gastrointestinal symptoms, bruxism), and salivary flow rate, in a group of 46 non-institutionalized CP individuals aged from 3 to 13 years. Twenty CP individuals with gastroesophageal reflux (GERDG) and 26 without gastroesophageal reflux (CG) were examined according to dental erosion criteria, drinking habits, presence of bruxism, and salivary flow rate. A face-to-face detailed questionnaire with the consumption and frequency of acid drinks, gastrointestinal symptoms (regurgitation and heart burn), and the presence of bruxism were answered by the caregivers of both groups. Unstimulated whole saliva was collected under slight suction, and salivary flow rate (ml/min) was calculated. The GERDG presented higher percentages of younger quadriplegics individuals compared to CG. The presence of regurgitation, heart burn, and tooth erosion (Grade 1) was significantly more prevalent in GERDG. It was observed difference in the salivary flow rate between the studied groups. On logistic multivariate regression analysis, the unique variable independently associated with the presence of GERD was dental erosion (P = 0.012, OR 86.64). The presence of GERD contributes significantly to dental erosion in the most compromised individuals with quadriplegics cerebral palsy individuals, increasing the risk of oral disease in this population. © 2011 John Wiley & Sons A/S.

Southern Appalachian hillslope erosion rates measured by soil and detrital radiocarbon in hollows

USGS Publications Warehouse

Hales, T.C.; Scharer, K.M.; Wooten, R.M.

2012-01-01

Understanding the dynamics of sediment generation and transport on hillslopes provides important constraints on the rate of sediment output from orogenic systems. Hillslope sediment fluxes are recorded by organic material found in the deposits infilling unchanneled convergent topographic features called hollows. This study describes the first hollow infilling rates measured in the southern Appalachian Mountains. Infilling rates (and bedrock erosion rates) were calculated from the vertical distribution of radiocarbon ages at two sites in the Coweeta drainage basin, western North Carolina. At each site we dated paired charcoal and silt soil organic matter samples from five different horizons. Paired radiocarbon samples were used to bracket the age of the soil material in order to capture the range of complex soil forming processes and deposition within the hollows. These dates constrain hillslope erosion rates of between 0.051 and 0.111mmyr-1. These rates are up to 4 times higher than spatially-averaged rates for the Southern Appalachian Mountains making creep processes one of the most efficient erosional mechanisms in this mountain range. Our hillslope erosion rates are consistent with those of forested mountain ranges in the western United States, suggesting that the mechanisms (dominantly tree throw) driving creep erosion in both the western United States and the Southern Appalachian Mountains are equally effective. ?? 2011 Elsevier B.V.

Erosion rates as a potential bottom-up control of forest structural characteristics in the Sierra Nevada Mountains.

PubMed

Milodowski, David T; Mudd, Simon M; Mitchard, Edward T A

2015-01-01

The physical characteristics of landscapes place fundamental constraints on vegetation growth and ecosystem function. In actively eroding landscapes, many of these characteristics are controlled by long-term erosion rates: increased erosion rates generate steeper topography and reduce the depth and extent of weathering, limiting moisture storage capacity and impacting nutrient availability. Despite the potentially important bottom-up control that erosion rates place on substrate characteristics, the relationship between the two is largely unexplored. We investigate spatial variations in aboveground biomass (AGB) across a structurally diverse mixed coniferous/deciduous forest with an order of magnitude erosion-rate gradient in the Northern Californian Sierra Nevada, USA, using high resolution LiDAR data and field plots. Mean basin slope, a proxy for erosion rate, accounts for 32% of variance in AGB within our field area (P < 0.001), considerably outweighing the effects of mean annual precipitation, temperature, and bedrock lithology. This highlights erosion rate as a potentially important, but hitherto unappreciated, control on AGB and forest structure.

Evaluation of rate of swelling and erosion of verapamil (VRP) sustained-release matrix tablets.

PubMed

Khamanga, Sandile M; Walker, Roderick B

2006-01-01

Tablets manufactured in-house were compared to a marketed sustained-release product of verapamil to investigate the rate of hydration, erosion, and drug-release mechanism by measuring the wet and subsequent dry weights of the products. Swelling and erosion rates depended on the polymer and granulating fluid used, which ultimately pointed to their permeability characteristics. Erosion rate of the marketed product was highest, which suggests that the gel layer that formed around these tablets was weak as opposed to the robust and resistant layers of test products. Anomalous and near zero-order transport mechanisms were dominant in tests and commercial product, respectively.

Structure-from-Motion as a method to quantify erosion volumes and to identify sediment sources in eroding rills

NASA Astrophysics Data System (ADS)

Brings, Christine; André Remke, Alexander; Gronz, Oliver; Becker, Kerstin; Seeger, Manuel; Ries, Johannes B.

2014-05-01

One particular problem in the study of rill erosion is the lack of information about sediment sources. So far, the sediment sources can only be identified by observation during the event or the experiment. Furthermore, only large and clear visible changes are considered and observations do not allow the quantification of erosion rates. A solution to this problem can be provided by 3D-modeling using the Structure from Motion (SfM)technique. Digital elevation models (DEM) from terrestrial and aircraft based images have been produced for many years; however, traditional photogrammetric analysis techniques require considerable expertise both for imaging and for data processing. The recent development of SfM providing for geoscientific applications the potential and greatly facilitated conditions for creating accurate 3D models from terrestrial and aerial photographs that were recorded by standard, non-metric cameras. Before and after the rill erosion experiments, coherent and largely overlapping terrestrial photos have been acquired. Afterwards, VisualSfM constructs 3D models by searching unique features in single images, searching for common features in image pairs and by triangulation of camera and feature positions using these pairs. The results are point clouds with x-, y- and z-coordinates, which are the basis for the preparation of the 3D-digital elevation models or volumetric surface models. The before and after models are all in their own, arbitrary coordinate systems and therefore they need to be superimposed and scaled. From the point clouds, surface models are created and via difference calculations of the before and after models, sediment sources can be detected, and erosion volumes can be quantified. Until now, the volume deviations between the 3D models and reference volumes do not exceed 10%. The noise of the 3D models in the worst dimension (z-axis) does not exceed the pixel spacing times 4-5. The results show that VisualSfM is a good, easy to apply and

Assessment of Spectroscopic, Real-time Ion Thruster Grid Erosion-rate Measurements

NASA Technical Reports Server (NTRS)

Domonkos, Matthew T.; Stevens, Richard E.

2000-01-01

The success of the ion thruster on the Deep Space One mission has opened the gate to the use of primary ion propulsion. Many of the projected planetary missions require throughput and specific impulse beyond those qualified to date. Spectroscopic, real-time ion thruster grid erosion-rate measurements are currently in development at the NASA Glenn Research Center. A preliminary investigation of the emission spectra from an NSTAR derivative thruster with titanium grid was conducted. Some titanium lines were observed in the discharge chamber; however, the signals were too weak to estimate the erosion of the screen grid. Nevertheless, this technique appears to be the only non-intrusive real-time means to evaluate screen grid erosion, and improvement of the collection optics is proposed. Direct examination of the erosion species using laser-induced fluorescence (LIF) was determined to be the best method for a real-time accelerator grid erosion diagnostic. An approach for a quantitative LIF diagnostic was presented.

Swelling and erosion properties of hydroxypropylmethylcellulose (Hypromellose) matrices--influence of agitation rate and dissolution medium composition.

PubMed

Kavanagh, Nicole; Corrigan, Owen I

2004-07-26

The effect of dissolution medium variables, such as medium composition, ionic strength and agitation rate, on the swelling and erosion of Hypromellose (hydroxypropylmethylcellulose, HPMC) matrices of different molecular weights was examined. Swelling and erosion of HPMC polymers was determined by measuring the wet and subsequent dry weights of matrices. It was possible to describe the rate of dissolution medium uptake in terms of a square root relationship and the erosion of the polymer in terms of the cube root law. The extent of swelling increased with increasing molecular weight, and decreased with increasing agitation rate. The erosion rate was seen to increase with decrease in polymer molecular weight, with a decrease in ionic strength and with increasing agitation rate. The sensitivity of polymer erosion to the degree of agitation may influence the ability of these polymers to give reproducible, agitation-independent release, compared to more rigid non-eroding matrix materials, in the complex hydrodynamic environment of the gastrointestinal tract.

Quantifying erosion over timescales of one million years: A photogrammetric approach on the amount of Rhenish erosion in southwestern Germany

NASA Astrophysics Data System (ADS)

Strasser, Annette; Strasser, Marcel; Seyfried, Hartmut

2010-10-01

The Lein valley in southwestern Germany possesses well-preserved Pliocene to mid Pleistocene land surfaces featuring a gentle relief and sediments accumulated by former tributaries of the Danube. This ancient Danubian land surface was captured and incised by mid Pleistocene to Holocene tributaries of the River Rhine. In a photogrammetric approach we calculated the volume of material extracted by Rhenish erosion providing a first quantification of the effects of stream piracy on timescales of about 1 Ma. Using stereoscopic surface modelling software a DEM was generated with a resolution of 5 m. From borehole data, literature, geological maps, and own field observations we determined the morphometric parameters of the ancient Danubian Ur-Lein valley. The gradient was imported as a 3D-breakline into the model where it controls the reinterpolation of surrounding data points. The result is a high-resolution DEM of the valley of the Ur-Lein. Subtraction of the DEM of the actual landscape from the DEM of the ancient Ur-Lein valley yields a model representing the rock volume eroded by the Rhenish Lein which totals 1.39 km 3 and converts into a rate of erosion between 63 and 74 mm/ka over a period of 700 to 600 ka, respectively, in accordance with figures obtained elsewhere in Central Europe through cosmogenic nuclides. It reflects the dominance of frequent fluctuations in climate and is considered to be mainly a product of strong changes in temperature and related processes during the transitional times between mid to late Pleistocene warm and cold states. A filtering procedure applied to cold and transitional state erosion rates of the Middle and Late Pleistocene yielded peak values between 66 and 77 mm/ka, up to three times higher than the modern rate or the rate of warm-state episodes. An assessment of the contribution of Rhenish stream piracy on long-term mid Pleistocene denudation under changing climate conditions resulted in a maximum 4.9-fold acceleration.

Erosion Rates at the Mars Exploration Rover Landing Sites and Long-Term Climate Change on Mars

NASA Technical Reports Server (NTRS)

Golombek, M. P.; Grant, J. A.; Crumpler, L. S.; Greeley, R.; Arvidson, R. E.; Bell, J. F., III; Weitz, C. M.; Sullivan, R.; Christensen, P. R.; Soderblom, L. A.;

Erosion rates at the Mars Exploration Rover landing sites and long-term climate change on Mars

USGS Publications Warehouse

Golombek, M.P.; Grant, J. A.; Crumpler, L.S.; Greeley, R.; Arvidson, R. E.; Bell, J.F.; Weitz, C.M.; Sullivan, R.J.; Christensen, P.R.; Soderblom, L.A.; Squyres, S. W.

2006-01-01

Erosion rates derived from the Gusev cratered plains and the erosion of weak sulfates by saltating sand at Meridiani Planum are so slow that they argue that the present dry and desiccating environment has persisted since the Early Hesperian. In contrast, sedimentary rocks at Meridiani formed in the presence of groundwater and occasional surface water, and many Columbia Hills rocks at Gusev underwent aqueous alteration during the Late Noachian, approximately coeval with a wide variety of geomorphic indicators that indicate a wetter and likely warmer environment. Two-toned rocks, elevated ventifacts, and perched and undercut rocks indicate localized deflation of the Gusev plains and deposition of an equivalent amount of sediment into craters to form hollows, suggesting average erosion rates of ???0.03 nm/yr. Erosion of Hesperian craters, modification of Late Amazonian craters, and the concentration of hematite concretions in the soils of Meridiani yield slightly higher average erosion rates of 1-10 nm/yr in the Amazonian. These erosion rates are 2-5 orders of magnitude lower than the slowest continental denudation rates on Earth, indicating that liquid water was not an active erosional agent. Erosion rates for Meridiani just before deposition of the sulfate-rich sediments and other eroded Noachian areas are comparable with slow denudation rates on Earth that are dominated by liquid water. Available data suggest the climate change at the landing sites from wet and likely warm to dry and desiccating occurred sometime between the Late Noachian and the beginning of the Late Hesperian (3.7-3.5 Ga). Copyright 2006 by the American Geophysical Union.

Erosive Augmentation of Solid Propellant Burning Rate: Motor Size Scaling Effect

NASA Technical Reports Server (NTRS)

Strand, L. D.; Cohen, Norman S.

1990-01-01

Two different independent variable forms, a difference form and a ratio form, were investigated for correlating the normalized magnitude of the measured erosive burning rate augmentation above the threshold in terms of the amount that the driving parameter (mass flux or Reynolds number) exceeds the threshold value for erosive augmentation at the test condition. The latter was calculated from the previously determined threshold correlation. Either variable form provided a correlation for each of the two motor size data bases individually. However, the data showed a motor size effect, supporting the general observation that the magnitude of erosive burning rate augmentation is reduced for larger rocket motors. For both independent variable forms, the required motor size scaling was attained by including the motor port radius raised to a power in the independent parameter. A boundary layer theory analysis confirmed the experimental finding, but showed that the magnitude of the scale effect is itself dependent upon scale, tending to diminish with increasing motor size.

Covariation of climate and long-term erosion rates acrossa steep rainfall gradient on the Hawaiian island of Kaua'i

USGS Publications Warehouse

Ken Ferrier,; J. Taylor Perron,; Sujoy Mukhopadhyay,; Matt Rosener,; Stock, Jonathan; Slosberg, Michelle; Kimberly L. Huppert,

2013-01-01

Erosion of volcanic ocean islands creates dramatic landscapes, modulates Earth’s carbon cycle, and delivers sediment to coasts and reefs. Because many volcanic islands have large climate gradients and minimal variations in lithology and tectonic history, they are excellent natural laboratories for studying climatic effects on the evolution of topography. Despite concerns that modern sediment fluxes to island coasts may exceed long-term fluxes, little is known about how erosion rates and processes vary across island interiors, how erosion rates are influenced by the strong climate gradients on many islands, and how modern island erosion rates compare to long-term rates. Here, we present new measurements of erosion rates over 5 yr to 5 m.y. timescales on the Hawaiian island of Kaua‘i, across which mean annual precipitation ranges from 0.5 to 9.5 m/yr. Eroded rock volumes from basins across Kaua‘i indicate that million-year-scale erosion rates are correlated with modern mean annual precipitation and range from 8 to 335 t km–2 yr–1. In Kaua‘i’s Hanalei River basin, 3He concentrations in detrital olivines imply millennial-scale erosion rates of >126 to >390 t km–2 yr–1 from olivine-bearing hillslopes, while fluvial suspended sediment fluxes measured from 2004 to 2009 plus estimates of chemical and bed-load fluxes imply basin-averaged erosion rates of 545 ± 128 t km–2 yr–1. Mapping of landslide scars in satellite imagery of the Hanalei basin from 2004 and 2010 implies landslide-driven erosion rates of 30–47 t km–2 yr–1. These measurements imply that modern erosion rates in the Hanalei basin are no more than 2.3 ± 0.6 times faster than millennial-scale erosion rates, and, to the extent that modern precipitation patterns resemble long-term patterns, they are consistent with a link between precipitation rates and long-term erosion rates.

Soil aggregation, erodibility, and erosion rates in mountain soils (NW Alps, Italy)

NASA Astrophysics Data System (ADS)

Stanchi, S.; Falsone, G.; Bonifacio, E.

2015-04-01

Erosion is a relevant soil degradation factor in mountain agrosilvopastoral ecosystems that can be enhanced by the abandonment of agricultural land and pastures left to natural evolution. The on-site and off-site consequences of soil erosion at the catchment and landscape scale are particularly relevant and may affect settlements at the interface with mountain ecosystems. RUSLE (Revised Universal Soil Loss Equation) estimates of soil erosion consider, among others, the soil erodibility factor (K), which depends on properties involved in structure and aggregation. A relationship between soil erodibility and aggregation should therefore be expected. However, erosion may limit the development of soil structure; hence aggregates should not only be related to erodibility but also partially mirror soil erosion rates. The aim of the research was to evaluate the agreement between aggregate stability and erosion-related variables and to discuss the possible reasons for discrepancies in the two kinds of land use considered (forest and pasture). Topsoil horizons were sampled in a mountain catchment under two vegetation covers (pasture vs. forest) and analyzed for total organic carbon, total extractable carbon, pH, and texture. Soil erodibility was computed, RUSLE erosion rate was estimated, and aggregate stability was determined by wet sieving. Aggregation and RUSLE-related parameters for the two vegetation covers were investigated through statistical tests such as ANOVA, correlation, and regression. Soil erodibility was in agreement with the aggregate stability parameters; i.e., the most erodible soils in terms of K values also displayed weaker aggregation. Despite this general observation, when estimating K from aggregate losses the ANOVA conducted on the regression residuals showed land-use-dependent trends (negative average residuals for forest soils, positive for pastures). Therefore, soil aggregation seemed to mirror the actual topsoil conditions better than soil

An assessment for the erosion rate of DEMO first wall

NASA Astrophysics Data System (ADS)

Tokar, M. Z.

2018-01-01

In a fusion reactor a significant fraction of plasma particles lost from the confined volume will reach the vessel wall. The recombination of these charged species, electrons and ions of hydrogen isotopes, is a source of neutral molecules and atoms, recycling back into the plasma. Here they participate, in particular, in charge-exchange (c-x) collisions with the plasma ions and, as a result, atoms of high energies with chaotically oriented velocities are generated. A significant fraction of these hot neutrals will hit the wall, leading, as well as the outflowing fuel and impurity ions, to its erosion, limiting the reactor operation time. The rate of the wall erosion in DEMO is assessed by applying a one-dimensional model which takes into account the transport of charged and neutral species across the flux surfaces in the main part of the scrape-off layer, beyond the X-point vicinity and divertor, and by considering the shift of the centers of flux surfaces, their elongation and triangularity. Atoms generated by c-x of recycling neutrals are modeled kinetically to define firmly their energy spectrum, being of particular importance for the erosion assessment. It is demonstrated the erosion rate of the DEMO wall armor of tungsten will have a pronounced ballooning character with a significant maximum of 0.3 mm per full power year at the low field side, decreasing with an increase in the anomalous perpendicular transport in the ‘far’ SOL or the plasma density at the separatrix.

Erosion rates of wood during natural weathering. Part I, Effects of grain angle and surface texture

Treesearch

R. Sam Williams; Mark T. Knaebe; Peter G. Sotos; William C. Feist

2001-01-01

This is the first in a series of reports on the erosion rates of wood exposed outdoors near Madison, Wisconsin. The specimens were oriented vertically, facing south; erosion was measured annually for the first several years and biannually for the remainder of the exposure. In the work reported here, the erosion rates of earlywood and latewood were determined for smooth...

Modulation of erosion rates of uplifting landscapes by long-term climate change: Experimental investigation

NASA Astrophysics Data System (ADS)

Moussirou, Bérangé; Bonnet, Stéphane

2017-04-01

Whether climatic variations play a major role, or not, in setting the erosion rate of continental landscapes is key for demonstrating the influence of climate on the tectonic evolution of mountain belts, as expected from analytical, numerical and analog modelling approaches. These models actually demonstrate that any modification in surface erosion rate that would affect significantly the gravitational loading of the continental crust might change its state of stress and consequently its deformation. However field evidences of these interactions has proved challenging to demonstrate unambiguously, the question of the climatic control on erosion efficiency at the geological time-scale being among the most critical issues. Here, we investigate how a change in precipitation influences the erosional dynamics of a landscape on the basis of an experimental approach where we surveyed the erosion by runoff of water of laboratory-scale landscapes that evolved under the combination of uplift and rainfall forcings (e.g. Bonnet and Crave, 2006). The experimental facility used is a modified of a device initially developed in the Geosciences Rennes laboratory and now set up in the Geosciences Environnement Toulouse laboratory. Following early experiments of Bonnet and Crave (2003) where the effect of a sudden drop in precipitation was investigated, we consider here the impact of decreasing rainfall events of finite duration on the erosive response of a landscape forced by a constant uplift (10 mm/h) and initially at steady-state (SS1). We performed several experiments with the same amplitude (from 160 to 60mm/h) but with different duration of rainfall drop (Tp: 0, 60, 300, 500, 700 min). As predicted theoretically and already observed in numerical and experimental modelling studies, a sudden drop of precipitation rate (Tp=0) induced a decrease of the mean erosion rate of the landscape (E), resulting in surface uplift. Then, landscape mean elevation stabilized to a higher value

Vegetation effects on soil water erosion rates and nutrient losses at Santa Catarina highlands, south Brazil

NASA Astrophysics Data System (ADS)

Bertol, I.; Barbosa, F. T.; Vidal Vázquez, E.; Paz Ferreiro, J.

2009-04-01

Water erosion involves three main processes: detachment, transport and deposition of soil particles. The main factors affecting water erosion are rainfall, soil, topography, soil management and land cover and use. Soil erosion potential is increased if the soil has no or very little vegetative cover of plants and/or crop residues, whereas plant and residue cover substantially decrease rates of soil erosion. Plant and residue cover protects the soil from raindrop impact and splash, tends to slow down the movement of surface runoff and allows excess surface water to infiltrate. Moreover, plant and residue cover improve soil physical, chemical and biological properties. Soils with improved structure have a greater resistance to erosion. By contrast, accelerated soil erosion is accentuated by deforestation, biomass burning, plowing and disking, cultivation of open-row crops, etc. The erosion-reducing effectiveness of plant and/or residue covers depends on the type, extent and quantity of cover. Vegetation and residue combinations that completely cover the soil are the most efficient in controlling soil. Partially incorporated residues and residual roots are also important, as these provide channels that allow surface water to move into the soil. The effectiveness of any crop, management system or protective cover also depends on how much protection is available at various periods during the year, relative to the amount of erosive rainfall that falls during these periods. Most of the erosion on annual row crop land can be reduced by leaving a residue cover greater after harvest and over the winter months, or by inter-seeding a forage crop. Soil erosion potential is also affected by tillage operations and tillage system. Conservation tillage reduces water erosion in relation to conventional tillage by increasing soil cover and soil surface roughness. Here, we review the effect of vegetation on soil erosion in the Santa Catarina highlands, south of Brazil, under

Dynamics of erosion in a compressional mountain range revealed by 10Be paleoerosion rates

NASA Astrophysics Data System (ADS)

Val, P.; Hoke, G. D.; Fosdick, J. C.; Wittmann, H.

2015-12-01

The temporal evolution of erosion over million-year timescales is key to understanding the evolution of mountain ranges and adjacent fold-and-thrust belts. While models of orogenic wedge evolution predict an instantaneous response of erosion to pulses of rock uplift, stream-power based landscape evolution models predict catchment-wide erosion maxima that lag behind a rock uplift pulse. Here, we explore the relationships between rock uplift, erosion, and sediment deposition in the Argentine Precordillera fold-and-thrust belt at 30°S where extensive previous work documents deformation, climate and sediment accumulation histories. Sandstone samples spanning 8.8 to 1.8 Ma were collected from the previously dated wedge-top (Iglesia) and foredeep basins (Bermejo) for quartz purification and 10Be extraction. 10Be concentrations due to burial and exhumation were estimated and subtracted from the measured concentrations and yielded the inherited 10Be concentrations, which were then corrected for sample magnetostratigraphic age. The inherited concentrations were then used to calculate paleoerosion rates. We modeled various pre-burial and post-burial exposure scenarios in order to assess potential sources of uncertainty in the recovered paleoerosion rates. The modeling results reveal that pre-burial and post-burial exposure periods only marginally affect our results. By combining the 10Be-derived paleoerosion rates and geomorphic observations with detrital zircon provenance, we document the isolation of the wedge-top basin, which was later reconnected by an upstream migrating pulse of erosion in a process that was directly controlled by thrust activity and base level. The data further indicate that the attainment of maximum upland erosion rates lags maximum rates of deformation and subsidence over million-year timescales. The magnitudes and causes of the erosional delays shed new light on the catchment erosional response to tectonic deformation and rock uplift in orogenic

From minerals to hillslopes: Towards an integrated framework for interpreting chemical and physical erosion

NASA Astrophysics Data System (ADS)

Hahm, W.; Riebe, C. S.; Ferrier, K.; Kirchner, J. W.

2011-12-01

Traditional frameworks for conceptualizing hillslope denudation distinguish between the movement of mass in solution (chemical erosion) and mass moved via mechanical processes (physical erosion). At the hillslope scale, physical and chemical erosion rates can be quantified by combining measurements of regolith chemistry with cosmogenic nuclide concentrations in bedrock and sediment, while basin-scale rates are often inferred from riverine solute and sediment loads. These techniques integrate the effects of numerous weathering and erosion mechanisms and do not provide prima facie information about the precise nature and scale of those mechanisms. For insight into erosional process, physical erosion has been considered in terms of two limiting regimes. When physical erosion outpaces weathering front advance, regolith is mobilized downslope as soon as it is sufficiently loosened by weathering, and physical erosion rates are limited by rates of mobile regolith production. This is commonly termed weathering-limited erosion. Conversely, when weathering front advance outpaces erosion, the mobile regolith layer grows thicker over time, and physical erosion rates are limited by the efficiency of downslope transport processes. This is termed transport-limited erosion. This terminology brings the description of hillslope evolution closer to the realm of essential realism, to the extent that measurable quantities from the field can be cast in a process-based framework. An analogous process-limitation framework describes chemical erosion. In supply-limited chemical erosion, chemical weathering depletes regolith of its reactive phases during residence on a hillslope, and chemical erosion rates are limited by the supply of fresh minerals to the weathering zone. Alternatively, hillslopes may exhibit kinetic-limited chemical erosion, where physical erosion transports regolith downslope before weatherable phases are completely removed by chemical erosion. We show how supply- and

Factors Influencing Watershed Average Erosion Rates Calculated from Reservoir Sedimentation in Eastern USA

NASA Astrophysics Data System (ADS)

Ahamed, A.; Snyder, N. P.; David, G. C.

2014-12-01

The Reservoir Sedimentation Database (ResSed), a catalogue of reservoirs and depositional data that has recently become publically available, allows for rapid calculation of sedimentation rates and rates of capacity loss over short (annual to decadal) timescales. This study is a statistical investigation of factors controlling watershed average erosion rates (E) in eastern United States watersheds. We develop an ArcGIS-based model that delineates watersheds upstream of ResSed dams and calculate drainage areas to determine E for 191 eastern US watersheds. Geomorphic, geologic, regional, climatic, and land use variables are quantified within study watersheds using GIS. Erosion rates exhibit a large amount of scatter, ranging from 0.001 to 1.25 mm/yr. A weak inverse power law relationship between drainage area (A) and E (R2 = 0.09) is evident, similar to other studies (e.g. Milliman and Syvitski, 1992; Koppes and Montgomery, 2009). Linear regressions reveal no relationship between mean watershed slope (S) and E, possibly due to the relatively low relief of the region (mean S for all watersheds is 6°). Analysis of Variance shows that watersheds in formerly glaciated regions exhibit a statistically significant lower mean E (0.06 mm/year) than watersheds in unglaciated regions (0.12 mm/year), but that watersheds with different dam purposes show no significant differences in mean E. Linear regressions reveal no relationships between E and land use parameters like percent agricultural land and percent impervious surfaces (I), but classification and regression trees indicate that watersheds in highly developed regions (I > 34%) exhibit mean E (0.36 mm/year) that is four times higher than watersheds in less developed (I < 34%) regions (0.09 mm/year). Further, interactions between land use variables emerge in formerly glaciated regions, where increased agricultural land results in higher rates of annual capacity loss in reservoirs (R2 = 0.56). Plots of E versus timescale of

Comparing erosion rates in burnt forests and agricultural fields for a mountain catchment in NW Iberia

NASA Astrophysics Data System (ADS)

Nunes, João Pedro; Marisa Santos, Juliana; Bernard-Jannin, Léonard; Keizer, Jan Jacob

2013-04-01

A large part of northwestern Iberia is nowadays covered by commercial forest plantations of eucalypts and maritime pines, which have partly replaced traditional agricultural land-uses. The humid Mediterranean climate, with mild wet winters and warm dry summers, creates favorable conditions for the occurrence of frequent and recurrent forest fires. Erosion rates in recently burnt areas have been the subject of numerous studies; however, there is still a lack of information on their relevance when compared with agricultural erosion rates, impairing a comprehensive assessment of the role of forests for soil protection. This study focuses on Macieira de Alcoba, head-water catchment in the Caramulo Mountain Range, north-central Portugal, with a mixture of agricultural fields (mostly a rotation between winter pastures and summer cereals) on the lower slopes and forest plantations (mostly eucalypts) on the upper slopes. Agricultural erosion in this catchment has been monitored since 2010; a forest fire in 2011 presented an opportunity to compare post-fire and agricultural erosion rates at nearby sites with comparable soil and climatic conditions. Erosion rates were monitored between 2010 and 2013 by repeated surveys of visible erosion features and, in particular, by mapping and measuring rills and gullies after important rainfall events. During the 2011/2012 hydrological year, erosion rates in the burnt forest were two orders of magnitude above those in agricultural fields, amounting to 17.6 and. 0.1 Mg ha-1, respectively. Rills were widespread in the burnt area, while in the agricultural area they were limited to a small number of fields with higher slope; these particular fields experienced an erosion rate of 2.3 Mg ha-1, still one order of magnitude lower than at the burnt forest site. The timing of the erosion features was also quite distinct for the burnt area and the agricultural fields. During the first nine months after the fire, rill formation was not observed in

Evaluation of soil erosion rates in the southern half of the Russian Plain: methodology and initial results

NASA Astrophysics Data System (ADS)

Golosov, Valentin; Gusarov, Artem; Litvin, Leonid; Yermolaev, Oleg; Chizhikova, Nelly; Safina, Guzel; Kiryukhina, Zoya

2017-03-01

The Russian Plain (RP) is divided into two principally different parts. The northern half of the RP is a predominantly forested area with a low proportion of arable fields. In contrast, the southern half of the RP has a very high proportion of arable land. During the last 30 years, this agricultural region of the RP has experienced considerable land use transformation and changes in precipitation due to climate change have altered soil erosion rates. This paper describes the use of erosion model calculations and GIS spatial analytical methods for the evaluation of trends in erosion rates in the RP. Climate change (RIHMI World Data Center, 2016), land use transformation and crop rotation modification (Rosstat, 2016; R Core Team, 2016) are the main factors governing erosion rates in the region during recent decades. It was determined that mean annual erosion rates have decreased from 7.3 to 4.1 t ha-1 yr-1 in the forest zone mostly because of the serious reduction in the surface runoff coefficient for periods of snowmelt. At the same time, the erosion rates have increased from 3.9 to 4.6 t ha-1 yr-1 in the steppe zone due to the increasing frequency of heavy rain-storms.

Spatial Patterns of Long-Term Erosion Rates Beneath the Marine West Antarctic Ice Sheet: Insights into the Physics of Continental Scale Glacial Erosion from a Comparison with the Ice-Velocity Field

NASA Astrophysics Data System (ADS)

Howat, I. M.; Tulaczyk, S.; Mac Gregor, K.; Joughin, I.

2001-12-01

As part of the effort to build quantitative models of glacial erosion and sedimentation, it is particularly important to construct scaled relations between erosion, transport, and sedimentation rates and appropriate glaciological variables (e.g., ice velocity). Recent acquisition of bed topography and ice velocity data for the marine West Antarctic Ice Sheet (WAIS)[Joughin et al., 1999; Lythe et al., in press] provides an unprecedented opportunity to investigate continental-scale patterns of glacial erosion and their relationship to the ice velocity field. Utilizing this data, we construct a map of estimated long-term erosion rates beneath the WAIS. In order to calculate long-term erosion rates from the available data, we assume that: (1) the ice sheet has been present for ~5 mill. years, (2) the initial topography beneath the WAIS was that of a typical ( ~200 m.b.s.l.) continental shelf, and (3) the present topography is near local isostatic equilibrium (Airy type). The map of long-term erosion rates constructed in this fashion shows an intriguing pattern of relatively high rates (of the order of 0.1 mm/yr) concentrated beneath modern ice stream tributaries (ice velocity ~100 m/yr), but much lower erosion rates (of the order of 0.01 mm/yr) beneath both the modern fast-moving ice streams ( ~400 m/yr.) and the slow-moving parts of the ice sheet ( ~10 m/yr). This lack of clear correlation between the estimated erosion rates and ice velocity is somewhat unexpected given that both observational and theoretical studies have shown that bedrock erosion rates beneath mountain glaciers can often be calculated by multiplying the basal sliding velocity by a constant (typically of the order of ~10^-4)(Humphrey and Raymond, 1993 and Mac Gregor et al., 2000). We obtain an improved match between estimated erosion rates and bed topography by calculating erosion rates using horizontal gradients within the ice velocity field rather than the magnitude of ice velocity, as consistent

Improvements in Quantifying Bank Erosion for Sediment Budgets within the Chesapeake Bay Watershed by Integrating Structure-From-Motion Photogrammetry

NASA Astrophysics Data System (ADS)

Bell, J. M.; Cashman, M. J.; Nibert, L.; Jackson, S.

2017-12-01

approach of quantifying geomorphic change, when coupled with bank-sediment bulk density, has promise to accurately quantify volumetric change as well as sediment loads originating from bank erosion, and may provide valuable data of the quantification of bank erosion for incorporation into regional sediment models.

Soil erosion rates (particulate and dissolved fluxes) variations in a temperate river basin

NASA Astrophysics Data System (ADS)

Cerdan, Olivier; Gay, Aurore; Négrel, Philippe; Pételet-Giraud, Emmanuelle; Salvador Blanes, Sébastien; Degan, Francesca

2015-04-01

Soil erosion is one of the major drivers of landscape evolution in Western Europe. However, depending on the land use characteristics and on the geological and topographical settings, miscellaneous forms of erosion may lead to a very diverse morphological evolution. To understand these landscape evolutions different scientific questions remain to be answered or quantified. The main difficulty arises from the nonlinear interactions between different erosional processes that act at different temporal and spatial scales. This study proposes to investigate different datasets describing particulate and dissolved sediment fluxes within a French River basin (The Loire River) at different spatial scales and at temporal scales ranging from the flood event to several decades. The particulate sediment load values at the outlet of the catchments range from 2.5 102 to 8.6 105 t yr-1, and the sediment yield values range from 2.9 to 32.4 t km 2 yr-1. Sediment exports from the Loire and Brittany river basins are low compared with mountainous regions and European exports. However, a strong spatial variability within this territory exists. The expected results on the sediment yield spatial pattern distribution and the correlation between SY values and basin sizes are not observed. An analysis of the sediment yield values at different time steps shows a strong effect of the seasonal availability of detached particles to be transported. High concentrations of suspended sediments during the winter and lower values during the summer and autumn are observed. Inter-annual variations are also observed, with export values varying by a factor 2 to 10 between years for one catchment. The influence of rainfall on the sediment exports is predominant, but investigations on physical characteristics of each catchment (e.g., lithology, slope, land use) are required to better understand the production and transfer processes within a drainage basin. These inter-annual variations imply that long

Uncertainties in assessing tillage erosion - How appropriate are our measuring techniques?

NASA Astrophysics Data System (ADS)

Fiener, P.; Wilken, F.; Aldana-Jague, E.; Deumlich, D.; Gómez, J. A.; Guzmán, G.; Hardy, R. A.; Quinton, J. N.; Sommer, M.; Van Oost, K.; Wexler, R.

2018-03-01

Tillage erosion on arable land is a very important process leading to a net downslope movement of soil and soil constitutes. Tillage erosion rates are commonly in the same order of magnitude as water erosion rates and can be even higher, especially under highly mechanized agricultural soil management. Despite its prevalence and magnitude, tillage erosion is still understudied compared to water erosion. The goal of this study was to bring together experts using different techniques to determine tillage erosion and use the different results to discuss and quantify uncertainties associated with tillage erosion measurements. The study was performed in northeastern Germany on a 10 m by 50 m plot with a mean slope of 8%. Tillage erosion was determined after two sequences of seven tillage operations. Two different micro-tracers (magnetic iron oxide mixed with soil and fluorescent sand) and one macro-tracer (passive radio-frequency identification transponders (RFIDs), size: 4 × 22 mm) were used to directly determine soil fluxes. Moreover, tillage induced changes in topography were measured for the entire plot with two different terrestrial laser scanners and an unmanned aerial system for structure from motion topography analysis. Based on these elevation differences, corresponding soil fluxes were calculated. The mean translocation distance of all techniques was 0.57 m per tillage pass, with a relatively wide range of mean soil translocation distances ranging from 0.39 to 0.72 m per pass. A benchmark technique could not be identified as all used techniques have individual error sources, which could not be quantified. However, the translocation distances of the macro-tracers used were consistently smaller than the translocation distances of the micro-tracers (mean difference = - 26 ± 12%), which questions the widely used assumption of non-selective soil transport via tillage operations. This study points out that tillage erosion measurements, carried out under almost

Post-fire mulching for runoff and erosion mitigation; Part I: Effectiveness at reducing hillslope erosion rates

Treesearch

Peter R. Robichaud; Sarah A. Lewis; Joseph W. Wagenbrenner; Louise E. Ashmun; Robert E. Brown

2013-01-01

Mulch treatments often are used to mitigate post-fire increases in runoff and erosion rates but the comparative effectiveness of various mulches is not well established. The ability of mulch treatments to reduce sediment yields from natural rainfall and resulting overland flow was measured using hillslope plots on areas burned at high severity following four wildfires...

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...

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.

Implications of sediment transport by subglacial water flow for interpreting contemporary glacial erosion rates

NASA Astrophysics Data System (ADS)

Beaud, Flavien; Flowers, Gwenn E.; Venditti, Jeremy G.

2017-04-01

The role of glaciers in landscape evolution is central to the interactions between climate and tectonic forces at high latitudes and in mountainous regions. Sediment yields from glacierized basins are used to quantify contemporary erosion rates on seasonal to decadal timescales, often under the assumption that subglacial water flow is the main contributor to these yields. Two recent studies have furthermore used such sediment fluxes to calibrate a glacial erosion rule, where erosion rate scales with ice sliding speed raised to a power greater than one. Subglacial sediment transport by water flow has however seldom been studied, thus the controls on sediment yield from glacierized basins remain enigmatic. To bridge this gap, we develop a 1-D model of morphodynamics in semi-circular bedrock-floored subglacial channels. We adapt a sediment conservation law from the fluvial literature, developed for both mixed bedrock / alluvial and alluvial conditions, to subglacial channels. Channel evolution is a function of the traditional melt-opening due to viscous heat dissipation from the water flow, and creep closure of the overlying ice, to which we add the closure or enlargement due to sediment deposition or removal, respectively. Using a simple ice geometry representing a land-terminating glacier, we find that the shear stresses produced by the water flow on the bed decrease significantly near the terminus. As the ice thins, creep closure decreases and large hydraulic potential gradients cannot be sustained. The resulting gradients in sediment transport lead to a bottleneck, and sediment accumulates if the sediment supply is adequate. A similar bottleneck occurs if a channel is well established and water discharge drops. Whether such constriction happens in space of time, in the presence of a sufficiently large sediment supply sediment accumulates temporarily near the terminus, followed shortly thereafter by enhanced sediment transport. Reduction in the cross-sectional area

Finding balance between fire hazard reduction and erosion control in the Lake Tahoe Basin, California–Nevada

Treesearch

Nicolas M. Harrison; Andrew P. Stubblefield; J. Morgan Varner; Eric E. Knapp

2016-01-01

The 2007 Angora Fire served as a stark reminder of the need for fuel reduction treatments in the Lake Tahoe Basin, California–Nevada, USA. Concerns exist, however, that the corresponding removal of forest floor fuels could increase erosion rates, negatively affecting the clarity of Lake Tahoe. To quantify trade-offs between fuel reduction and erosion, we conducted...

Assessment of Pole Erosion in a Magnetically Shielded Hall Thruster

NASA Technical Reports Server (NTRS)

Mikellides, Ioannis G.; Ortega, Alejandro L.

2014-01-01

Numerical simulations of a 6-kW laboratory Hall thruster called H6 have been performed to quantify the erosion rate at the inner pole. The assessments have been made in two versions of the thruster, namely the unshielded (H6US) and magnetically shielded (H6MS) configurations. The simulations have been performed with the 2-D axisymmetric code Hall2De which employs a new multi-fluid ion algorithm to capture the presence of low-energy ions in the vicinity of the poles. It is found that the maximum computed erosion rate at the inner pole of the H6MS exceeds the measured rate of back-sputtered deposits by 4.5 times. This explains only part of the surface roughening that was observed after a 150-h wear test, which covered most of the pole area exposed to the plasma. For the majority of the pole surface the computed erosion rates are found to be below the back-sputter rate and comparable to those in the H6US which exhibited little to no sputtering in previous tests. Possible explanations for the discrepancy are discussed.

Effect of Impact Angle on the Erosion Rate of Coherent Granular Soil, with a Chernozemic Soil as an Example

NASA Astrophysics Data System (ADS)

Larionov, G. A.; Bushueva, O. G.; Gorobets, A. V.; Dobrovol'skaya, N. G.; Kiryukhina, Z. P.; Krasnov, S. F.; Kobylchenko Kuksina, L. V.; Litvin, L. F.; Sudnitsyn, I. I.

2018-02-01

It has been shown in experiments in a hydraulic flume with a knee-shaped bend that the rate of soil erosion more than doubles at the flow impact angles to the channel side from 0° to 50°. At higher channel bends, the experiment could not be performed because of backwater. Results of erosion by water stream approaching the sample surface at angles between 2° and 90° are reported. It has been found that the maximum erosion rate is observed at flow impact angles of about 45°, and the minimum rate at 90°. The minimum soil erosion rate is five times lower than the maximum erosion rate. This is due to the difference in the rate of free water penetration into the upper soil layer, and the impact of the hydrodynamic pressure, which is maximum at the impact angle of 90°. The penetration of water into the interaggregate space results in the breaking of bonds between aggregates, which is the main condition for the capture of particles by the flow.

Constraining Quaternary ice covers and erosion rates using cosmogenic 26Al/10Be nuclide concentrations

NASA Astrophysics Data System (ADS)

Knudsen, Mads Faurschou; Egholm, David Lundbek

2018-02-01

Paired cosmogenic nuclides are often used to constrain the exposure/burial history of landforms repeatedly covered by ice during the Quaternary, including tors, high-elevation surfaces, and steep alpine summits in the circum-Arctic regions. The approach generally exploits the different production rates and half-lives of 10Be and 26Al to infer past exposure/burial histories. However, the two-stage minimum-limiting exposure and burial model regularly used to interpret the nuclides ignores the effect of variable erosion rates, which potentially may bias the interpretation. In this study, we use a Monte Carlo model approach to investigate systematically how the exposure/burial and erosion history, including variable erosion and the timing of erosion events, influence concentrations of 10Be and 26Al. The results show that low 26Al/10Be ratios are not uniquely associated with prolonged burial under ice, but may as well reflect ice covers that were limited to the coldest part of the late Pleistocene combined with recent exhumation of the sample, e.g. due to glacial plucking during the last glacial period. As an example, we simulate published 26Al/10Be data from Svalbard and show that it is possible that the steep alpine summits experienced ice-free conditions during large parts of the late Pleistocene and varying amounts of glacial erosion. This scenario, which contrasts with the original interpretation of more-or-less continuous burial under non-erosive ice over the last ∼1 Myr, thus challenge the conventional interpretation of such data. On the other hand, high 26Al/10Be ratios do not necessarily reflect limited burial under ice, which is the common interpretation of high ratios. In fact, high 26Al/10Be ratios may also reflect extensive burial under ice, combined with a change from burial under erosive ice, which brought the sample close to the surface, to burial under non-erosive ice at some point during the mid-Pleistocene. Importantly, by allowing for variable

Small crater modification on Meridiani Planum and implications for erosion rates and climate change on Mars

USGS Publications Warehouse

Golombek, M.P.; Warner, N.H.; Ganti, V.; Lamb, M.P.; Parker, T.J.; Fergason, Robin L.; Sullivan, R.

2014-01-01

A morphometric and morphologic catalog of ~100 small craters imaged by the Opportunity rover over the 33.5 km traverse between Eagle and Endeavour craters on Meridiani Planum shows craters in six stages of degradation that range from fresh and blocky to eroded and shallow depressions ringed by planed off rim blocks. The age of each morphologic class from <50–200 ka to ~20 Ma has been determined from the size-frequency distribution of craters in the catalog, the retention age of small craters on Meridiani Planum, and the age of the latest phase of ripple migration. The rate of degradation of the craters has been determined from crater depth, rim height, and ejecta removal over the class age. These rates show a rapid decrease from ~1 m/Myr for craters <1 Ma to ~ <0.1 m/Myr for craters 10–20 Ma, which can be explained by topographic diffusion with modeled diffusivities of ~10−6 m2/yr. In contrast to these relatively fast, short-term erosion rates, previously estimated average erosion rates on Mars over ~100 Myr and 3 Gyr timescales from the Amazonian and Hesperian are of order <0.01 m/Myr, which is 3–4 orders of magnitude slower than typical terrestrial rates. Erosion rates during the Middle-Late Noachian averaged over ~250 Myr, and ~700 Myr intervals are around 1 m/Myr, comparable to slow terrestrial erosion rates calculated over similar timescales. This argues for a wet climate before ~3 Ga in which liquid water was the erosional agent, followed by a dry environment dominated by slow eolian erosion.

WTP Pretreatment Facility Potential Design Deficiencies--Sliding Bed and Sliding Bed Erosion Assessment

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

Hansen, E. K.

2015-05-06

This assessment is based on readily available literature and discusses both Newtonian and non-Newtonian slurries with respect to sliding beds and erosion due to sliding beds. This report does not quantify the size of the sliding beds or erosion rates due to sliding beds, but only assesses if they could be present. This assessment addresses process pipelines in the Pretreatment (PT) facility and the high level waste (HLW) transfer lines leaving the PT facility to the HLW vitrification facility concentrate receipt vessel.

Developing an Erosion Rate Map for Myanmar Using USLE, GIS and Remote Sensing

NASA Astrophysics Data System (ADS)

Emtehani, Sobhan; Rutten, Martine

2017-04-01

Predicting erosion and estimating sediment loads in rivers are of major tasks in water resources system planning and management. In Myanmar erosion and collapse of river banks is common during the rainy season and riverine communities are frequently forced to relocate as their homes are dangerously close to the disintegrating river banks (Mann 2013). Myanmar is one of climatically most diverse countries located in Southeast Asia, where sheet, rill, and gully erosion affect crop yields as well as livelihood strategies of many people (Htwe, Brinkmann et al. 2015). In Myanmar, soil erosion measurement and monitoring approaches are increasingly important for land management planning to effectively avoid erosion and soil degradation, but such monitoring is limited by the availability of data and budgetary constraints. Therefore, spatial modeling approaches using GIS and remote sensing techniques play an important role for rapid risk assessments (Htwe 2016). In this study ''Model Builder'' tool in ArcGIS was used to create a model which generates an erosion rate map using Universal Soil Loss Equation (USLE). USLE is the product of five factors: rainfall erosivity factor (R), soil erodibility factor (K), slope length and steepness factor (LS), crop management factor (C), and support practice factor (P). Input data files for this model were acquired from online open source databases. Precipitation data was downloaded from Tropical Rainfall Measuring Mission (TRMM) for calculation of R factor. The resolution of TRMM data is very coarse (0.25 degree × 0.25 degree), therefore it was spatially downscaled by developing a relation between TRMM and Normalized Difference Vegetation Index (NDVI) using regression analysis method. Soil maps depicting percentages of sand, clay and silt were obtained from soilgrids website for calculation of K factor. Digital Elevation Model (DEM) with resolution of 90 meters was taken from Shuttle Radar Topography Mission (SRTM) for calculation of LS

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

USDA-ARS?s Scientific Manuscript database

Rainfall erosivity quantifies the climatic effect on water erosion. In the framework of the Universal Soil Loss Equation, rainfall erosivity, also known as the R-factor, is defined as the mean annual sum of event erosivity values. For a new global soil erosion assessment, also in the broad context...

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.

Solar radiation and landscape evolution: co-evolution of topography, vegetation, and erosion rates in a semi-arid ecosystem

NASA Astrophysics Data System (ADS)

Istanbulluoglu, Erkan; Yetemen, Omer

2016-04-01

In this study CHILD landscape evolution model (LEM) is used to study the role of solar radiation on the co-evolution of landscape morphology, vegetation patterns, and erosion rates in a central New Mexico catchment. In the study site north facing slopes (NFS) are characterized by steep diffusion-dominated planar hillslopes covered by co-exiting juniper pine and grass vegetation. South facing slopes (SFS) are characterized by shallow slopes and covered by sparse shrub vegetation. Measured short-term and Holocene-averaged erosion rates show higher soil loss on SFS than NFS. In this study CHILD LEM is first confirmed with ecohydrologic field data and used to systematically examine the co-evolution of topography, vegetation pattern, and erosion rates. Aspect- and network-control are identified as the two main topographic drivers of soil moisture and vegetation organization on the landscape. Landscape-scale and long-term implications of solar radiation driven ecohdrologic patterns emerged in modeled landscape: NFS supported denser vegetation cover and became steeper and planar, while on SFS vegetation grew sparser and slopes declined with more fluvial activity. At the landscape scale, these differential erosion processes led to asymmetric development of catchment forms, consistent with regional observations. While the general patterns of vegetation and topography were reproduced by the model using a stationary representation of the current climate, the observed differential Holocene erosion rates were captured by the model only when cyclic climate is used. This suggests sensitivity of Holocene erosion rates to long-term climate fluctuations.

High Voltage TAL Erosion Characterization

NASA Technical Reports Server (NTRS)

Jacobson, David T.

2003-01-01

Extended operation of a D-80 anode layer thruster at high voltage was investigated. The thruster was operated for 1200 hours at 700 Volts and 4 Amperes. Laser profilometry was employed to quantify the erosion of the thruster's graphite guard rings and electrodes at 0, 300, 600, 900, and 1200 hours. Thruster performance and electrical characteristics were monitored over the duration of the investigation. The guard rings exhibited asymmetric erosion that was greatest in the region of the cathode. Erosion of the guard rings exposed the magnet poles between 600 to 900 hours of operation.

Evaluation of post-wildfire runoff and erosion on semiarid ecological sites

Treesearch

Ginger B. Paige; Jeffry J. Stone; D. Phillip Guertin

2005-01-01

Field studies are being conducted to quantify runoff and erosion rates following wildfires in semiarid rangelands. Rainfall simulator experiments were conducted on two grassland sites and one oak woodland site in Southern Arizona immediately following wildfires in 2002 and 2003. The experiments applied a range of rainfall intensities between 50 and 180 mm/h....

Impacts of the post-fire erosion processes compared with the agricultural erosion rates for a mountain catchment in NW Iberia

NASA Astrophysics Data System (ADS)

Marisa Santos, Juliana; Nunes, João Pedro; Bernard-Jannin, Léonard; Gonzalez Pelayo, Oscar; Keizer, Jan Jacob

2014-05-01

after forest fires. The last forest fire in August 2011 burned 10% of the total area in the north-west part of the catchment. Post-fire management operations 9 month after the fire (clear-cutting and deep plowing operations) and after plantation of "Quercus robur" left the soil exposed, and relatively mild rainstorms led to large amounts of soil loss, including a large amount of rills and other erosion features. This constituted an opportunity to compare these erosion rates with the ones observed in agricultural fields for similar edapho-climatic conditions, and also observe distinct timing of erosion occurrence which was linked with different periods when soils are exposed. This communication presents the assessment of the impact of this fire on soil erosion rates, where results indicate that soil losses after soil preparation for forest replanting might be equivalent, in long-term, to soil losses in agricultural fields.

Numerical simulation of mud erosion rate in sand-mud alternate layer and comparison with experiment

NASA Astrophysics Data System (ADS)

Yoshida, T.; Yamaguchi, T.; Oyama, H.; Sato, T.

2015-12-01

For gas production from methane hydrates in sand-mud alternate layers, depressurization method is expected as feasible. After methane hydrate is dissociated, gas and water flow in pore space. There is a concern about the erosion of mud surface and it may result in flow blockage that disturbs the gas production. As a part of a Japanese National hydrate research program (MH21, funded by METI), we developed a numerical simulation of water-induced mud erosion in pore-scale sand-mud domains to model such mud erosion. The size of which is of the order of 100 micro meter. Water flow is simulated using a lattice Boltzmann method (LBM) and mud surface is treated as solid boundary with arbitrary shape, which changes with time. Periodic boundary condition is adopted at the domain boundaries, except for the surface of mud layers and the upper side. Shear stress acting on the mud surface is calculated using a momentum-exchange method. Mud layer is eroded when the shear stress exceeds a threshold coined a critical shear stress. In this study, we compared the simulated mud erosion rate with experimental data acquired from an experiment using artificial sand-mud core. As a result, the simulated erosion rate agrees well with that of the experiment.

Does introduced fauna influence soil erosion? A field and modelling assessment.

PubMed

Hancock, G R; Lowry, J B C; Dever, C; Braggins, M

2015-06-15

Pigs (Sus scrofa) are recognised as having significant ecological impacts in many areas of the world including northern Australia. The full consequences of the introduction of pigs are difficult to quantify as the impacts may only be detected over the long-term and there is a lack of quantitative information on the impacts of feral pigs globally. In this study the effect of feral pigs is quantified in an undisturbed catchment in the monsoonal tropics of northern Australia. Over a three-year period, field data showed that the areal extent of pig disturbance ranged from 0.3-3.3% of the survey area. The mass of material exhumed through these activities ranged from 4.3 t ha(-1) yr(-1) to 36.0 t ha(-1) yr(-1). The findings demonstrate that large introduced species such as feral pigs are disturbing large areas as well as exhuming considerable volumes of soil. A numerical landscape evolution and soil erosion model was used to assess the effect of this disturbance on catchment scale erosion rates. The modelling demonstrated that simulated pig disturbance in previously undisturbed areas produced lower erosion rates compared to those areas which had not been impacted by pigs. This is attributed to the pig disturbance increasing surface roughness and trapping sediment. This suggests that in this specific environment, disturbance by pigs does not enhance erosion. However, this conclusion is prefaced by two important caveats. First, the long term impact of soil disturbance is still very uncertain. Secondly, modelling results show a clear differentiation between those from an undisturbed environment and those from a post-mining landscape, in which pig disturbance may enhance erosion. Copyright © 2015. Published by Elsevier B.V.

Quantifying Anthropogenic Dust Emissions

NASA Astrophysics Data System (ADS)

Webb, Nicholas P.; Pierre, Caroline

2018-02-01

Anthropogenic land use and land cover change, including local environmental disturbances, moderate rates of wind-driven soil erosion and dust emission. These human-dust cycle interactions impact ecosystems and agricultural production, air quality, human health, biogeochemical cycles, and climate. While the impacts of land use activities and land management on aeolian processes can be profound, the interactions are often complex and assessments of anthropogenic dust loads at all scales remain highly uncertain. Here, we critically review the drivers of anthropogenic dust emission and current evaluation approaches. We then identify and describe opportunities to: (1) develop new conceptual frameworks and interdisciplinary approaches that draw on ecological state-and-transition models to improve the accuracy and relevance of assessments of anthropogenic dust emissions; (2) improve model fidelity and capacity for change detection to quantify anthropogenic impacts on aeolian processes; and (3) enhance field research and monitoring networks to support dust model applications to evaluate the impacts of disturbance processes on local to global-scale wind erosion and dust emissions.

Quantifying the effect of ecological restoration on soil erosion in China's Loess Plateau region: an application of the MMF approach.

PubMed

Li, Changbin; Qi, Jiaguo; Feng, Zhaodong; Yin, Runsheng; Guo, Biyun; Zhang, Feng; Zou, Songbing

2010-03-01

Land degradation due to erosion is one of the most serious environmental problems in China. To reduce land degradation, the government has taken a number of conservation and restoration measures, including the Sloping Land Conversion Program (SLCP), which was launched in 1999. A logical question is whether these measures have reduced soil erosion at the regional level. The objective of this article is to answer this question by assessing soil erosion dynamics in the Zuli River basin in the Loess Plateau of China from 1999 to 2006. The MMF (Morgan, Morgan and Finney) model was used to simulate changes in runoff and soil erosion over the period of time during which ecological restoration projects were implemented. Some model variables were derived from remotely sensed images to provide improved land surface representation. With an overall accuracy rate of 0.67, our simulations show that increased ground vegetation cover, especially in forestlands and grasslands, has reduced soil erosion by 38.8% on average from 1999 to 2006. During the same time period, however, the change in rainfall pattern has caused a 13.1% +/- 4.3% increase in soil erosion, resulting in a net 25.7% +/- 8.5% reduction in soil erosion. This suggests that China's various ecological restoration efforts have been effective in reducing soil loss.

Estimating Erosion Rates using Caesium-137 Tracers in the Ethiopian Highlands

NASA Astrophysics Data System (ADS)

Guzman, C. D.; Tilahun, S. A.; Zegeye, A. D.; Yitaferu, B.; Kay, R. W.; Steenhuis, T. S.

2016-12-01

The effects and seriousness of soil erosion have been gaining more attention recently, especially with respect to shortening the life of reservoirs for hydroelectric power generation and diminished agricultural productivity. A central aim of this study on soil erosion and conservation is to compare and contrast estimates and identification of eroding areas and patterns in the Ethiopian highlands. In Debre Mawi, Ethiopia, we examined spatial variations in erosion from an agricultural watershed using the soil-adsorbed radionuclide caesium-137(Cs-137) as a sediment tracer. Sixteen sites were monitored in this small watershed 30 km south of Lake Tana, with characteristic semi-monsoonal rains, during the long (kremt) rainy season for topsoil depth change, groundwater table height, and ceasium-137 inventory. These sixteen sites are divided among cropped and fallow land and are spread out among upslope, midslope, and downslope areas within the watershed. The Cs-137 tracer method mapped the upland mildly sloping areas to be eroding at a greater average rate than any of the mid-slope or toe-slope areas. From comparisons with the sediment concentration in the downstream weir and groundwater table measurements, we draw information helpful in understanding why and how sediment concentration and erosion decreases or increases at certain times during the rainy season. By combining these different detection methods we hope to enable the development of more effective and sustainable conservation practices.

Influence of liquid temperature and flow rate on enamel erosion and surface softening.

PubMed

Eisenburger, M; Addy, M

2003-11-01

Enamel erosion and softening are based on chemical processes which could be influenced by many factors including temperature and acid flow rate. Knowledge of the influence of these variables could have relevance to research experiments and clinical outcomes. Both parameters were investigated using an ultrasonication and profilometry method to assess erosion depth and surface softening of enamel. The influence of temperature was studied by eroding polished human enamel samples at 4, 20, 35 or 50 degrees C for 2 h. Secondly, different liquid flow conditions were established by varying acid agitation. Additionally, a slow laminar flow and a jet of citric acid, to simulate drinking through a straw, were applied to specimens. Erosion depth increased significantly with acid temperature from 11.0 microm at 4 degrees C to 35.8 microm at 50 degrees C. Surface softening increased much more slowly and plateaued at 2.9 microm to 3.5 microm after 35 degrees C. A strong dependence of erosion on liquid flow was revealed. In unstirred conditions only 8.6 microm erosion occurred, which increased to 22.2 microm with slow stirring and 40.9 microm with fast stirring. Surface softening did not increase correspondingly with its largest extent at slow stirring at 3.4 microm.The implication of these data are: first, the conditions for erosion experiments in vitro or in situ need to be specified for reliable comparisons between studies. Secondly, erosion of teeth by soft drinks are likely to be influenced both by the temperature of the drink and individual drinking habits.

Latitudinal variation of sedimentation and erosion rates from Patagonia and Antarctic Peninsula tidewater glaciers (46°-65° S)

NASA Astrophysics Data System (ADS)

Fernandez-Vasquez, R. A.; Anderson, J. B.; Wellner, J. S.; Minzoni, R. L.

2012-12-01

We present the results of the study of tidewater glacier depositional basins, across a broad latitudinal transect from central Patagonia (46°S) to the Antarctic Peninsula (65°S). Based on sediment cores and seismic records, we estimate accumulation rates at several timescales as well as sediment-volume derived erosion rates (Er) for millennial time scales. In the Antarctic Peninsula, accumulation rates are ~100 mm/yr for centennial and millennial timescales. In Patagonia, proximal basins are in general well isolated and have short timescale (decadal-centennial) sedimentary records and high accumulation rates, whereas medial (more distal) basins have millennial scale sedimentary records and low accumulation rates. We hypothesize that the "Saddler effect" in the accumulation rates of the Patagonian study areas exists because Neoglacial advance and recent post-Little Ice Age retreat has left well isolated proximal basins that effectively trap sediments. This, along with high sediment yields, produces high decadal accumulation rates. There is no such organization of basins in the Antarctic Peninsula fjords and bays and no such clear manifestation of Neoglacial advances or morphologies. Erosion rates span two orders of magnitude from 0.03 mm/yr for Lapeyrère Bay at Anvers Island, Antarctica (~64.5°S), to 1.09 mm/yr for San Rafael Glacier in northern Patagonia (~46.5°S). Rates for Antarctic Peninsula glaciers are in general lower than those of temperate Patagonian glaciers. A good correlation of erosion rates and modern sea level annual temperature was found. A latitudinal decrease in millennial erosion rates is interpreted as a result of decreasing annual temperature although decreasing annual precipitation may also be a factor. However, local variability within each region might be influenced by differences in bedrock geology (e.g. Herbert Sound versus Lapeyrère and Andvord bays ) and drainage basin morphology (hypsometry, number of glaciers and length of overall

Impact of glaciations on the long-term erosion in Southern Patagonian Andes

NASA Astrophysics Data System (ADS)

Simon-Labric, Thibaud; Herman, Frederic; Baumgartner, Lukas; Shuster, David L.; Braun, Jean; Reiners, Pete W.; Valla, Pierre G.; Leuthold, Julien

2014-05-01

The Southern Patagonian Andes are an ideal setting to study the impact of Late-Cenozoic climate cooling and onset of glaciations impact on the erosional history of mountain belts. The lack of tectonic activity during the last ~12 Myr makes the denudation history mainly controlled by surface processes, not by tectonics. Moreover, the glaciations history of Patagonia shows the best-preserved records within the southern hemisphere (with the exception of Antarctica). Indeed, the dry climate on the leeward side of Patagonia and the presence of lava flows interbedded with glacial deposits has allowed an exceptional preservation of late Cenozoic moraines with precise dating using K-Ar analyses on lava flow. The chronology of moraines reveals a long history covering all the Quaternary, Pliocene, and up to the Upper Miocene. The early growth of large glaciers flowing on eastern foothills started at ~7-6 Myr, while the maximum ice-sheet extent dates from approximately 1.1 Myr. In order to quantify the erosion history of the Southern Patagonian Andes and compare it to the glaciations sediment record, we collected samples along an age-elevation profile for low-temperature thermochronology in the eastern side of the mountain belt (Torres del Paine massif). The (U-Th)/He age-elevation relationship shows a clear convex shape providing an apparent long-term exhumation rate of ~0.2 km/Myr followed by an exhumation rate increase at ~6 Myr. Preliminary results of 4He/3He thermochronometry for a subset of samples complete the erosion history for the Plio-Pleistocene epoch. We used inverse procedure predicting 4He distributions within an apatite grain using a radiation-damage and annealing model to quantify He-diffusion kinetics in apatite. The model also allows quantifying the impact of potential U-Th zonation throughout each apatite crystal. Inversion results reveal a denudation history composed by a pulse of denudation at ~6 Ma, as suggested by the age-elevation relationship

Ultrasonic Measurement of Erosion/corrosion Rates in Industrial Piping Systems

NASA Astrophysics Data System (ADS)

Sinclair, A. N.; Safavi, V.; Honarvar, F.

2011-06-01

Industrial piping systems that carry aggressive corrosion or erosion agents may suffer from a gradual wall thickness reduction that eventually threatens pipe integrity. Thinning rates could be estimated from the very small change in wall thickness values measured by conventional ultrasound over a time span of at least a few months. However, measurements performed over shorter time spans would yield no useful information—minor signal distortions originating from grain noise and ultrasonic equipment imperfections prevent a meaningful estimate of the minuscule reduction in echo travel time. Using a Model-Based Estimation (MBE) technique, a signal processing scheme has been developed that enables the echo signals from the pipe wall to be separated from the noise. This was implemented in a laboratory experimental program, featuring accelerated erosion/corrosion on the inner wall of a test pipe. The result was a reduction in the uncertainty in the wall thinning rate by a factor of four. This improvement enables a more rapid response by system operators to a change in plant conditions that could pose a pipe integrity problem. It also enables a rapid evaluation of the effectiveness of new corrosion inhibiting agents under plant operating conditions.

A morphology independent methodology for quantifying planview river change and characteristics from remotely sensed imagery

DOE PAGES

Rowland, Joel C.; Shelef, Eitan; Pope, Paul A.; ...

2016-07-15

Remotely sensed imagery of rivers has long served as a means for characterizing channel properties and detection of planview change. In the last decade the dramatic increase in the availability of satellite imagery and processing tools has created the potential to greatly expand the spatial and temporal scale of our understanding of river morphology and dynamics. To date, the majority of GIS and automated analyses of planview changes in rivers from remotely sensed data has been developed for single-threaded meandering river systems. These methods have limited applicability to many of the earth's rivers with complex multi-channel planforms. Here we presentmore » the methodologies of a set of analysis algorithms collectively called Spatially Continuous Riverbank Erosion and Accretion Measurements (SCREAM). SCREAM analyzes planview river metrics regardless of river morphology. These algorithms quantify both the erosion and accretion rates of riverbanks from binary masks of channels generated from imagery acquired at two time periods. Additionally, the program quantifies the area of change between river channels and the surrounding floodplain and area of islands lost or formed between these two time periods. To examine variations in erosion rates in relation to local channel attributes and make rate comparisons between river systems of varying sizes, the program determines channel widths and bank curvature at every bank pixel. SCREAM was developed and tested on rivers with diverse and complex planform morphologies in imagery acquired from a range of observational platforms with varying spatial resolutions. Here, validation and verification of SCREAM-generated metrics against manual measurements show no significant measurement errors in determination of channel width, erosion, and bank aspects. SCREAM has the potential to provide data for both the quantitative examination of the controls on erosion rates and for the comparison of these rates across river systems

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.

Extremely low glacial headwall retreat rates quantified using debris-covered glaciers in the Transantarctic Mountains

NASA Astrophysics Data System (ADS)

Mackay, S. L.; Marchant, D. R.

2017-12-01

The McMurdo Dry Valleys (MDV) region of Antarctica is considered to be one of the most geomorphically stable regions on Earth. The extreme landscape stability is attributed primarily to persistent cold-polar desert conditions, and has enabled the multi-million-year preservation of near-surface terrestrial archives that are critical to our understanding of Antarctic ice sheet dynamics and climate change over at least the last 14 Ma. Correct interpretation of these archives requires well-constrained estimates of the rate of landscape alteration and erosion. Previous studies using tephrochronology of in situ ash deposits and terrestrial cosmogenic nuclides from bedrock and regolith on ridge crests, valley bottoms, and other low-angled, sub-horizontal surfaces have yielded inferred erosion rates of 5×10-5 to 9×10-4mm a-1 . However, estimates for erosion of cliff faces in topographically complex terrain that dominates the upland region of the MDV are largely unknown. Here we measure, for the first time in the MDV, the average rate of erosion and headwall-retreat for near-vertical glaciated cirques. To accomplish this, we analyze the sediment flux through the Mullins and Friedman glaciers; these are cold-based, topographically constrained, and slow-moving debris-covered alpine glaciers that collect and transport debris sourced entirely from rockfall at the headwall cirque. Using data from 15 km of ground penetrating radar profiles, 12 shallow ice cores, and 180 shallow surface excavations, we compile an estimated total sediment load for each glacier. We then combine this sediment load with measurements of the debris source area and a glacial chronology based on cosmogenic nuclide dating and measured ice flow velocities. Results indicate average headwall erosion rates of 1×10-3-5×10-3 mm a-1 and slope-adjusted headwall retreat rates of 9×10-4-4×10-3 mm a-1 over the past 225 ka. These values are the lowest yet reported and are several orders of magnitude lower than

Rates and drivers of erosion in the Southern Pyrenees: a 10Be-supported model for the Valle de la Fueva catchments

NASA Astrophysics Data System (ADS)

Stange, Kurt Martin; Midtkandal, Ivar; Petter Nystuen, Johan; Sohbati, Reza; Murray, Andrew Sean; Spiegel, Cornelia; Kuss, Jochen

2017-04-01

Intramontane basins are typical features of every mountain chain. These topographic depressions function as sediment traps during the syn- and postorogenic evolution of a range. Hence, studying their sedimentary archives and morphogenetic development may deliver important insights into the dynamics and magnitudes of erosion-sedimentation processes in mountain catchments and their susceptibility towards changing environmental conditions. Aiming at quantifying Quaternary catchment erosion rates in the Southern Pyrenees and determining the timing and driving parameters of basin excavation stages, this research project focusses on a number of adjacent watersheds in the Valle de la Fueva in Aragon, Spain. Besides providing a comprehensive OSL and 10Be-supported catchment erosion model, potential relationships of intense late stage erosion phases with watershed capture, base level changes and climatic controls are addressed. The Valle de la Fueva comprises a number of sub-catchments of the Ainsa depression - an Eocene sedimentary basin situated in the southern Pyrenean fold and thrust belt (SPFZ) which is recognized as a prime analogue for reservoir geometries and turbidite systems. The Valle de la Fueva is a highly erodible catchment, typical for the SPFZ with its shallow and deep marine strata, conglomerates and synorogenic debris. Preliminary observations revealed systems of "cut-in-fill" alluvial terraces and residual erosion surfaces - i.e. pediments and glacis that are strongly dissected by gullies and barrancos. Basin outlet canyons are deeply entrenched into the Los Molinos thrust front and represent dramatic landscape features that are relevant to the base level and opening history of the Valle de la Fueva catchments. Combining digital terrain analysis with field surveys and exposure/burial dating, first results revealed differences in stream profile gradation and incision magnitudes among several sub-catchments. Since they share a common base level, the main

Erosion of volcanic ocean islands: insights from modeling, topographic analyses, and cosmogenic exposure dating

NASA Astrophysics Data System (ADS)

Huppert, K.; Perron, J. T.; Ferrier, K.; Mukhopadhyay, S.; Rosener, M.; Douglas, M.

2016-12-01

With homogeneous bedrock, dramatic rainfall gradients, paleoshorelines, and datable remnant topography, volcanic ocean islands provide an exceptional natural experiment in landscape evolution. Analyses traversing gradients in island climate and bedrock age have the potential to advance our understanding of landscape evolution in a diverse range of continental settings. However, as small, conical, dominantly subsiding, and initially highly permeable landmasses, islands are unique, and it remains unclear how these properties influence their erosional history. We use a landscape evolution model and observations from the Hawaiian island of Kaua'i and other islands to characterize the topographic evolution of volcanic ocean islands. We present new measurements of helium-3 concentrations in detrital olivine from 20 rivers on Kaua'i. These measurements indicate that minimum erosion rates over the past 3 to 48 kyr are on average 2.6 times faster than erosion rates averaged over the past 3.9 to 4.4 Myr estimated from the volume of river canyons. This apparent acceleration of erosion rates on Kaua'i is consistent with observations on other islands; erosion rates estimated from the volume of river canyons on 31 islands worldwide, combined with observations of minimal incision on young island volcanoes, suggest a progressive increase in erosion rates over the first few million years of island landscape development. Using a landscape evolution model, we perform a set of experiments to quantify the contribution of subsidence, climate change, and initial geometry to changes in island erosion rates through time. We base these experiments on the evolution of Kaua'i, and we use measured erosion rates and the observed topography to calibrate the model. We find that progressive steepening of island topography by canyon incision drives an acceleration of erosion rates over time. Increases in mean channel and hillslope gradient with island age in the global compilation suggest this may

Comparison of Erosion Rates Estimated by Sediment Budget Techniques and Suspended Sediment Monitoring and Regulatory Implications

NASA Astrophysics Data System (ADS)

O'Connor, M.; Eads, R.

2007-12-01

Watersheds in the northern California Coast Range have been designated as "impaired" with respect to water quality because of excessive sediment loads and/or high water temperature. Sediment budget techniques have typically been used by regulatory authorities to estimate current erosion rates and to develop targets for future desired erosion rates. This study examines erosion rates estimated by various methods for portions of the Gualala River watershed, designated as having water quality impaired by sediment under provisions of the Clean Water Act Section 303(d), located in northwest Sonoma County (~90 miles north of San Francisco). The watershed is underlain by Jurassic age sedimentary and meta-sedimentary rocks of the Franciscan formation. The San Andreas Fault passes through the western edge of watershed, and other active faults are present. A substantial portion of the watershed is mantled by rock slides and earth flows, many of which are considered dormant. The Coast Range is geologically young, and rapid rates of uplift are believed to have contributed to high erosion rates. This study compares quantitative erosion rate estimates developed at different spatial and temporal scales. It is motivated by a proposed vineyard development project in the watershed, and the need to document conditions in the project area, assess project environmental impacts and meet regulatory requirements pertaining to water quality. Erosion rate estimates were previously developed using sediment budget techniques for relatively large drainage areas (~100 to 1,000 km2) by the North Coast Regional Water Quality Control Board and US EPA and by the California Geological Survey. In this study, similar sediment budget techniques were used for smaller watersheds (~3 to 8 km2), and were supplemented by a suspended sediment monitoring program utilizing Turbidity Threshold Sampling techniques (as described in a companion study in this session). The duration of the monitoring program to date

Temporally and spatially uniform rates of erosion in the southern Appalachian Great Smoky Mountains

USGS Publications Warehouse

Matmon, A.; Bierman, P.R.; Larsen, J.; Southworth, S.; Pavich, M.; Caffee, M.

2003-01-01

We measured 10Be in fluvial sediment samples (n = 27) from eight Great Smoky Mountain drainages (1-330 km2). Results suggest spatially homogeneous sediment generation (on the 104-105 yr time scale and > 100 km2 spatial scale) at 73 ?? 11 t km-2 yr-1, equivalent to 27 ?? 4 m/m.y. of bedrock erosion. This rate is consistent with rates derived from fission-track, long-term sediment budget, and sediment yield data, all of which indicate that the Great Smoky Mountains and the southern Appalachians eroded during the Mesozoic and Cenozoic at ???30 m/m.y. In contrast, unroofing rates during the Paleozoic orogenic events that formed the Appalachian Mountains were higher (???102 m/m.y.). Erosion rates decreased after termination of tectonically driven uplift, enabling the survival of this ancient mountain belt with its deep crustal root as an isostatically maintained feature in the contemporary landscape.

In-Situ Measurement of Hall Thruster Erosion Using a Fiber Optic Regression Probe

NASA Technical Reports Server (NTRS)

Polzin, Kurt; Korman, Valentin

2009-01-01

One potential life-limiting mechanism in a Hall thruster is the erosion of the ceramic material comprising the discharge channel. This is especially true for missions that require long thrusting periods and can be problematic for lifetime qualification, especially when attempting to qualify a thruster by analysis rather than a test lasting the full duration of the mission. In addition to lifetime, several analytical and numerical models include electrode erosion as a mechanism contributing to enhanced transport properties. However, there is still a great deal of dispute over the importance of erosion to transport in Hall thrusters. The capability to perform an in-situ measurement of discharge channel erosion is useful in addressing both the lifetime and transport concerns. An in-situ measurement would allow for real-time data regarding the erosion rates at different operating points, providing a quick method for empirically anchoring any analysis geared towards lifetime qualification. Erosion rate data over a thruster s operating envelope would also be useful in the modeling of the detailed physics inside the discharge chamber. There are many different sensors and techniques that have been employed to quantify discharge channel erosion in Hall thrusters. Snapshots of the wear pattern can be obtained at regular shutdown intervals using laser profilometry. Many non-intrusive techniques of varying complexity and sensitivity have been employed to detect the time-varying presence of erosion products in the thruster plume. These include the use quartz crystal microbalances, emission spectroscopy, laser induced flourescence, and cavity ring-down spectroscopy. While these techniques can provide a very accurate picture of the level of eroded material in the thruster plume, it is more difficult to use them to determine the location from which the material was eroded. Furthermore, none of the methods cited provide a true in-situ measure of erosion at the channel surface while

Bank erosion of navigation canals in the western and central Gulf of Mexico

USGS Publications Warehouse

Thatcher, Cindy A.; Hartley, Stephen B.; Wilson, Scott A.

2011-01-01

Erosion of navigation canal banks is a direct cause of land loss, but there has been little quantitative analysis to determine why certain major canals exhibit faster widening rates (indicative of erosion) than others in the coastal zones of Texas, Louisiana, Mississippi, and Alabama. We hypothesize that navigation canals exhibit varying rates of erosion based on soil properties of the embankment substrate, vegetation type, geologic region (derived from digital versions of state geologic maps), and the presence or absence of canal bank armaments (that is, rock rip-rap, concrete bulkheads, or other shoreline protection structures). The first objective of this project was to map the shoreline position and substrate along both banks of the navigation canals, which were digitized from 3 different time periods of aerial photography spanning the years of 1978/79 to 2005/06. The second objective was to quantify the erosion rates of the navigation canals in the study area and to determine whether differences in erosion rates are related to embankment substrate, vegetation type, geologic region, or soil type. To measure changes in shoreline position over time, transects spaced at 50-m (164-ft) intervals were intersected with shorelines from all three time periods, and an annual rate of change was calculated for each transect. Mean annual rates of shoreline change ranged from 1.75 m/year (5.74 ft/year) on the west side of the Atchafalaya River, La., where there was shoreline advancement or canal narrowing, to -3.29 m/year (-10.79 ft/year) on the south side of the Theodore Ship Channel, Ala., where there was shoreline retreat or erosion. Statistical analysis indicated that there were significant differences in shoreline retreat rates according to geologic region and marsh vegetation type, and a weak relationship with soil organic content. This information can be used to better estimate future land loss rates associated with navigation canals and to prioritize the location of

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.

Validating and Improving Interrill Erosion Equations

PubMed Central

Zhang, Feng-Bao; Wang, Zhan-Li; Yang, Ming-Yi

2014-01-01

Existing interrill erosion equations based on mini-plot experiments have largely ignored the effects of slope length and plot size on interrill erosion rate. This paper describes a series of simulated rainfall experiments which were conducted according to a randomized factorial design for five slope lengths (0.4, 0.8, 1.2, 1.6, and 2 m) at a width of 0.4 m, five slope gradients (17%, 27%, 36%, 47%, and 58%), and five rainfall intensities (48, 62.4, 102, 149, and 170 mm h−1) to perform a systematic validation of existing interrill erosion equations based on mini-plots. The results indicated that the existing interrill erosion equations do not adequately describe the relationships between interrill erosion rate and its influencing factors with increasing slope length and rainfall intensity. Univariate analysis of variance showed that runoff rate, rainfall intensity, slope gradient, and slope length had significant effects on interrill erosion rate and that their interactions were significant at p = 0.01. An improved interrill erosion equation was constructed by analyzing the relationships of sediment concentration with rainfall intensity, slope length, and slope gradient. In the improved interrill erosion equation, the runoff rate and slope factor are the same as in the interrill erosion equation in the Water Erosion Prediction Project (WEPP), with the weight of rainfall intensity adjusted by an exponent of 0.22 and a slope length term added with an exponent of −0.25. Using experimental data from WEPP cropland soil field interrill erodibility experiments, it has been shown that the improved interrill erosion equation describes the relationship between interrill erosion rate and runoff rate, rainfall intensity, slope gradient, and slope length reasonably well and better than existing interrill erosion equations. PMID:24516624

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.

Mountain erosion over decades and millennia: New insights from sediment yields and cosmogenic nuclides

NASA Astrophysics Data System (ADS)

Callahan, R. P.; Riebe, C. S.; Ferrier, K.

2017-12-01

For more than two decades, cosmogenic nuclides have been used to quantify catchment-wide erosion rates averaged over tens of thousands of years. These rates have been used as baselines for comparison with sediment yields averaged over decades, leading to insights on how human activities such as deforestation and agriculture have influenced the production and delivery of sediment to streams and oceans. Here we present new data from the southern Sierra Nevada, California, where sediment yields have been measured over the last ten years using sediment trapping and gauging methods. Cosmogenic nuclides measured in stream sediment reveal erosion rates that are between 13 and 400 (average = 94) times faster than erosion rates inferred from annual accumulations in sediment traps. We show that the discrepancy can be explained by extremely low sediment trapping efficiency, which leads to bias in the short-term rates due to incomplete capture of suspended sediment. Thus the short-term rates roughly agree with the long-term rates, despite intensive timber harvesting in the study catchments over the last century. This differs from results obtained in similar forested granitic catchments of Idaho, where long-term rates are more than ten times greater than short-term rates because large, rare events do not contribute to the short-term averages. Our analysis of a global database indicates that both the magnitude and sign of differences between short- and long-term average erosion rates are difficult to predict, even when the history of land use in known.

MINErosion 3: Using measurements on a tilting flume-rainfall simulator facility to predict erosion rates from post-mining landscapes in Central Queensland, Australia

PubMed Central

Khalifa, Ashraf M.; Yu, Bofu; Caroll, Chris; Burger, Peter; Mulligan, David

2018-01-01

Open-cut coal mining in Queensland results in the formation of extensive saline overburden spoil-piles with steep slopes at the angle of repose (approximately 75% or 37o). These spoil-piles are generally found in multiple rows, several kilometers in length and heights of up to 50 or 60 m above the original landscape. They are highly dispersive and erodible. Legislation demands that these spoil piles be rehabilitated to minimize on-site and off-site discharges of sediment and salt into the surrounding environment. To achieve this, the steep slopes must be reduced, stabilized against erosion, covered with topsoil and re-vegetated. Key design criteria (slope gradient, slope length and vegetation cover) are required for the construction of post-mining landscapes that will result in acceptable erosion rates. A novel user-friendly hillslope computer model MINErosion 3.4 was developed that can accurately predict potential erosion rates from field scale hillslopes using parameters measured with a 3m laboratory tilting flume-rainfall simulator or using routinely measured soil physical and chemical properties. This model links MINErosion 2 with a novel consolidation and above ground vegetation cover factors, to the RUSLE and MUSLE equations to predict the mean annual and storm event erosion rates. The RUSLE-based prediction of the mean annual erosion rates allow minesites to derive the key design criteria of slope length, slope gradient and vegetation cover that would lead to acceptable erosion rates. The MUSLE-based prediction of storm event erosion rates will be useful as input into risk analysis of potential damage from erosion. MINErosion 3.4 was validated against erosion measured on 20 m field erosion plots established on post-mining landscapes at the Oakey Creek and Curragh coalmines, as well as on 120 and 70 m erosion plots on postmining landscapes at Kidston Gold Mine. PMID:29590190

MINErosion 3: Using measurements on a tilting flume-rainfall simulator facility to predict erosion rates from post-mining landscapes in Central Queensland, Australia.

PubMed

So, Hwat Bing; Khalifa, Ashraf M; Yu, Bofu; Caroll, Chris; Burger, Peter; Mulligan, David

2018-01-01

Open-cut coal mining in Queensland results in the formation of extensive saline overburden spoil-piles with steep slopes at the angle of repose (approximately 75% or 37o). These spoil-piles are generally found in multiple rows, several kilometers in length and heights of up to 50 or 60 m above the original landscape. They are highly dispersive and erodible. Legislation demands that these spoil piles be rehabilitated to minimize on-site and off-site discharges of sediment and salt into the surrounding environment. To achieve this, the steep slopes must be reduced, stabilized against erosion, covered with topsoil and re-vegetated. Key design criteria (slope gradient, slope length and vegetation cover) are required for the construction of post-mining landscapes that will result in acceptable erosion rates. A novel user-friendly hillslope computer model MINErosion 3.4 was developed that can accurately predict potential erosion rates from field scale hillslopes using parameters measured with a 3m laboratory tilting flume-rainfall simulator or using routinely measured soil physical and chemical properties. This model links MINErosion 2 with a novel consolidation and above ground vegetation cover factors, to the RUSLE and MUSLE equations to predict the mean annual and storm event erosion rates. The RUSLE-based prediction of the mean annual erosion rates allow minesites to derive the key design criteria of slope length, slope gradient and vegetation cover that would lead to acceptable erosion rates. The MUSLE-based prediction of storm event erosion rates will be useful as input into risk analysis of potential damage from erosion. MINErosion 3.4 was validated against erosion measured on 20 m field erosion plots established on post-mining landscapes at the Oakey Creek and Curragh coalmines, as well as on 120 and 70 m erosion plots on postmining landscapes at Kidston Gold Mine.

Uplift history of the Sila Massif, southern Italy, deciphered from cosmogenic 10Be erosion rates and river longitudinal profile analysis

USGS Publications Warehouse

Olivetti, Valerio; Cyr, Andrew J.; Molin, Paola; Faccenna, Claudio; Granger, Darryl E.

2012-01-01

The Sila Massif in the Calabrian Arc (southern Italy) is a key site to study the response of a landscape to rock uplift. Here an uplift rate of ∼1 mm/yr has imparted a deep imprint on the Sila landscape recorded by a high-standing low-relief surface on top of the massif, deeply incised fluvial valleys along its flanks, and flights of marine terraces in the coastal belt. In this framework, we combined river longitudinal profile analysis with hillslope erosion rates calculated by 10Be content in modern fluvial sediments to reconstruct the long-term uplift history of the massif. Cosmogenic data show a large variation in erosion rates, marking two main domains. The samples collected in the high-standing low-relief surface atop Sila provide low erosion rates (from 0.09 ± 0.01 to 0.13 ± 0.01 mm/yr). Conversely, high values of erosion rate (up to 0.92 ± 0.08 mm/yr) characterize the incised fluvial valleys on the massif flanks. The analyzed river profiles exhibit a wide range of shapes diverging from the commonly accepted equilibrium concave-up form. Generally, the studied river profiles show two or, more frequently, three concave-up segments bounded by knickpoints and characterized by different values of concavity and steepness indices. The wide variation in cosmogenic erosion rates and the non-equilibrated river profiles indicate that the Sila landscape is in a transient state of disequilibrium in response to a strong and unsteady uplift not yet counterbalanced by erosion.

Patterns, rates and possible causes of saltmarsh erosion in the Greater Thames area (UK)

NASA Astrophysics Data System (ADS)

van der Wal, Daphne; Pye, Kenneth

2004-08-01

The estuary-dominated coast of the Greater Thames in England has experienced rapid lateral erosion and internal dissection of saltmarshes. This paper provides an overview of saltmarsh development in this area, and re-examines the role of environmental and human forcing factors. It draws on documentary evidence, including historical maps, survey data and time-series data of forcing factors. Lateral marsh retreat began in the 19th century in the Medway and Blackwater Estuaries, followed by other estuaries in the Greater Thames region at the beginning of the 20th century. The outer estuaries and the wider parts of the inner estuaries especially have experienced erosion. Erosion has been modest in wave-sheltered areas, e.g., the Colne and the inner Crouch. In the 1960s and, more widely, the 1970s, a phase of rapid erosion took place, with erosion rates of up to ca. 16 ha year -1 per site, notably along the open coast of Dengie and Foulness, and in the Blackwater and Thames Estuaries. At all sites, vertical sediment accretion was well able to keep up with sea level rise over the past century. Evidence indicates that there may have been several causes for the erosion of saltmarshes. These are notably land claim and embankment construction (increasing the tidal range and current velocities) and a continuous rise of, especially, high and extreme water levels. The latest episode of rapid erosion in the 1970s is largely attributed to changes in the wind/wave climate. For example, erosion at wave-exposed sites coincided with a peak in high magnitude waves combined with a high incidence of southeasterly waves. The study shows that many factors, including natural forcing factors and human activities, have to be taken into account when explaining saltmarsh development.

Modulation of the erosion rate of an uplifting landscape by long-term climate change: An experimental investigation

NASA Astrophysics Data System (ADS)

Moussirou, Bérangé; Bonnet, Stéphane

2018-02-01

Whether or not climatic variations play a major role in setting the erosion rate of continental landscapes is a key factor in demonstrating the influence of climate on the tectonic evolution of mountain belts and understanding how clastic deposits preserved in sedimentary basins may record climatic variations. Here, we investigate how a change in precipitation influences the erosional dynamics of laboratory-scale landscapes that evolved under a combination of uplift and rainfall forcings. We consider here the impact of a decrease in the precipitation rate of finite duration on the erosive response of a landscape forced by a constant uplift and initially at a steady state (SS1). We performed several experiments with the same amplitude but different durations of precipitation decrease (Tp). We observe that the decrease in precipitation induces a phase of surface uplift of landscapes to a new steady state condition (SS2); however, the details of the uplift histories (timing, rate) differ between the experiments according to Tp. We also observe a decrease in the erosion rate induced by the precipitation change; however, the timing and amplitude of this decrease vary according to Tp, defining a delayed and damped erosion signal. Our data show that the landscape response to precipitation change is dictated by a critical water-to-rock ratio (ratio of precipitation over uplift) that likely corresponds to a geomorphic threshold. Our study suggests that variations in precipitation that occur at a geological time scale (> 106 years) may have a weak impact on the erosion of landscapes and on the delivery of siliciclastic material to large rivers and sedimentary basins.

Shoreline erosion at selected areas along Lake Sharpe on the Lower Brule Reservation in South Dakota, 1966–2015

USGS Publications Warehouse

Thompson, Ryan F.; Stamm, John F.

2018-06-21

The Lower Brule Reservation in central South Dakota is losing land because of shoreline erosion along Lake Sharpe, a reservoir on the Missouri River, which has caused detrimental effects for the Lower Brule Sioux Tribe including losses of cultural sites, recreation access points, wildlife habitat, irrigated cropland, and landmass. To better understand and quantify shoreline erosion, the Lower Brule Sioux Tribe and the U.S. Geological Survey cooperated on a series of data-collection efforts and study of shoreline erosion along Lake Sharpe. Data collected or compiled for 1966–2015 were used to describe and quantify shoreline erosion along Lake Sharpe. The progression of shoreline erosion near the community of Lower Brule, South Dakota, was tracked by comparing current or recent aerial imagery with existing historical maps. At 33 evaluation lines along a 7-mile reach of Lake Sharpe shoreline near Lower Brule, cumulative change of shoreline from 1966 to 2010 ranged from about −224 feet of deposition to 770 feet of erosion.Photographic and location data were collected for this study to understand the processes affecting erosion and estimate erosion rates. Photographs were collected only in the 7-mile reach near Lower Brule, but locations of the bank over time were collected at the 7-mile reach and two additional reaches within the Lower Brule Reservation. Global navigation satellite system equipment was used in real-time kinematic mode to collect bank locations along three reaches of interest. Reach-length data were collected four times between November 2011 and November 2012. A small, unmanned aerial system (drone) was used to capture digital video along the shoreline of the 7-mile reach.Water-level fluctuations contribute to the number of wet-dry cycles experienced by the soils at the shoreline or bank. The soils present under the current (2017) location of the reservoir are predominantly terrace alluvium, consisting of sand and silt. Detailed soils data for Lyman

Minimal erosion of Arctic alpine topography during late Quaternary glaciation

NASA Astrophysics Data System (ADS)

Gjermundsen, Endre F.; Briner, Jason P.; Akçar, Naki; Foros, Jørn; Kubik, Peter W.; Salvigsen, Otto; Hormes, Anne

2015-10-01

The alpine topography observed in many mountainous regions is thought to have formed during repeated glaciations of the Quaternary period. Before this time, landscapes had much less relief. However, the spatial patterns and rates of Quaternary exhumation at high latitudes--where cold-based glaciers may protect rather than erode landscapes--are not fully quantified. Here we determine the exposure and burial histories of rock samples from eight summits of steep alpine peaks in northwestern Svalbard (79.5° N) using analyses of 10Be and 26Al concentrations. We find that the summits have been preserved for at least the past one million years. The antiquity of Svalbard’s alpine landscape is supported by the preservation of sediments older than one million years along a fjord valley, which suggests that both mountain summits and low-elevation landscapes experienced very low erosion rates over the past million years. Our findings support the establishment of northwestern Svalbard’s alpine topography during the early Quaternary. We suggest that, as the Quaternary ice age progressed, glacial erosion in the Arctic became inefficient and confined to ice streams, and high-relief alpine landscapes were preserved by minimally erosive glacier armour.

Extracting information on the spatial variability in erosion rate stored in detrital cooling age distributions in river sands

NASA Astrophysics Data System (ADS)

Braun, Jean; Gemignani, Lorenzo; van der Beek, Peter

2018-03-01

One of the main purposes of detrital thermochronology is to provide constraints on the regional-scale exhumation rate and its spatial variability in actively eroding mountain ranges. Procedures that use cooling age distributions coupled with hypsometry and thermal models have been developed in order to extract quantitative estimates of erosion rate and its spatial distribution, assuming steady state between tectonic uplift and erosion. This hypothesis precludes the use of these procedures to assess the likely transient response of mountain belts to changes in tectonic or climatic forcing. Other methods are based on an a priori knowledge of the in situ distribution of ages to interpret the detrital age distributions. In this paper, we describe a simple method that, using the observed detrital mineral age distributions collected along a river, allows us to extract information about the relative distribution of erosion rates in an eroding catchment without relying on a steady-state assumption, the value of thermal parameters or an a priori knowledge of in situ age distributions. The model is based on a relatively low number of parameters describing lithological variability among the various sub-catchments and their sizes and only uses the raw ages. The method we propose is tested against synthetic age distributions to demonstrate its accuracy and the optimum conditions for it use. In order to illustrate the method, we invert age distributions collected along the main trunk of the Tsangpo-Siang-Brahmaputra river system in the eastern Himalaya. From the inversion of the cooling age distributions we predict present-day erosion rates of the catchments along the Tsangpo-Siang-Brahmaputra river system, as well as some of its tributaries. We show that detrital age distributions contain dual information about present-day erosion rate, i.e., from the predicted distribution of surface ages within each catchment and from the relative contribution of any given catchment to the

Designing a national soil erosion monitoring network for England and Wales

NASA Astrophysics Data System (ADS)

Lark, Murray; Rawlins, Barry; Anderson, Karen; Evans, Martin; Farrow, Luke; Glendell, Miriam; James, Mike; Rickson, Jane; Quine, Timothy; Quinton, John; Brazier, Richard

2014-05-01

Although soil erosion is recognised as a significant threat to sustainable land use and may be a priority for action in any forthcoming EU Soil Framework Directive, those responsible for setting national policy with respect to erosion are constrained by a lack of robust, representative, data at large spatial scales. This reflects the process-orientated nature of much soil erosion research. Recognising this limitation, The UK Department for Environment, Food and Rural Affairs (Defra) established a project to pilot a cost-effective framework for monitoring of soil erosion in England and Wales (E&W). The pilot will compare different soil erosion monitoring methods at a site scale and provide statistical information for the final design of the full national monitoring network that will: provide unbiased estimates of the spatial mean of soil erosion rate across E&W (tonnes ha-1 yr-1) for each of three land-use classes - arable and horticultural grassland upland and semi-natural habitats quantify the uncertainty of these estimates with confidence intervals. Probability (design-based) sampling provides most efficient unbiased estimates of spatial means. In this study, a 16 hectare area (a square of 400 x 400 m) positioned at the centre of a 1-km grid cell, selected at random from mapped land use across E&W, provided the sampling support for measurement of erosion rates, with at least 94% of the support area corresponding to the target land use classes. Very small or zero erosion rates likely to be encountered at many sites reduce the sampling efficiency and make it difficult to compare different methods of soil erosion monitoring. Therefore, to increase the proportion of samples with larger erosion rates without biasing our estimates, we increased the inclusion probability density in areas where the erosion rate is likely to be large by using stratified random sampling. First, each sampling domain (land use class in E&W) was divided into strata; e.g. two sub

Contributions of solar-wind induced potential sputtering to the lunar surface erosion rate and it's exosphere

NASA Astrophysics Data System (ADS)

Alnussirat, S. T.; Barghouty, A. F.; Edmunson, J. E.; Sabra, M. S.; Rickman, D. L.

2018-04-01

Sputtering of lunar regolith by solar-wind protons and heavy ions with kinetic energies of about 1 keV/amu is an important erosive process that affects the lunar surface and exosphere. It plays an important role in changing the chemical composition and thickness of the surface layer, and in introducing material into the exosphere. Kinetic sputtering is well modeled and understood, but understanding of mechanisms of potential sputtering has lagged behind. In this study we differentiate the contributions of potential sputtering from the standard (kinetic) sputtering in changing the chemical composition and erosion rate of the lunar surface. Also we study the contribution of potential sputtering in developing the lunar exosphere. Our results show that potential sputtering enhances the total characteristic sputtering erosion rate by about 44%, and reduces sputtering time scales by the same amount. Potential sputtering also introduces more material into the lunar exosphere.

Quantifying the Spatial Distribution of Hill Slope Erosion Using a 3-D Laser Scanner

NASA Astrophysics Data System (ADS)

Scholl, B. N.; Bogonko, M.; He, Y.; Beighley, R. E.; Milberg, C. T.

2007-12-01

Soil erosion is a complicated process involving many interdependent variables including rainfall intensity and duration, drop size, soil characteristics, ground cover, and surface slope. The interplay of these variables produces differing spatial patterns of rill versus inter-rill erosion by changing the effective energy from rain drop impacts and the quantities and timing of sheet and shallow, concentrated flow. The objective of this research is to characterize the spatial patterns of rill and inter-rill erosion produced from simulated rainfall on different soil densities and surface slopes using a 3-D laser scanner. The soil used in this study is a sandy loam with bulk density due to compaction ranging from 1.25-1.65 g/cm3. The surface slopes selected for this study are 25, 33, and 50 percent and represent common slopes used for grading on construction sites. The spatial patterns of soil erosion are measured using a Trimble GX DR 200+ 3D Laser Scanner which employs a time of flight calculation averaged over 4 points using a class 2, pulsed, 532 nm, green laser at a distance of 2 to 11 m from the surface. The scanner measures point locations on an approximately 5 mm grid. The pre- and post-erosion scan surfaces are compared to calculate the change in volume and the dimensions of rills and inter-rill areas. The erosion experiments were performed in the Soil Erosion Research Laboratory (SERL), part of the Civil and Environmental Engineering department at San Diego State University. SERL experiments utilize a 3-m by 10-m tilting soil bed with a soil depth of 0.5 meters. Rainfall is applied to the soil surface using two overhead Norton ladder rainfall simulators, which produce realistic rain drop diameters (median = 2.25 mm) and impact velocities. Simulated storm events used in this study consist of rainfall intensities ranging from 5, 10 to 15 cm/hr for durations of 20 to 30 minutes. Preliminary results are presented that illustrate a change in runoff processes and

Measuring low rates of erosion from forest fuel reduction operations

Treesearch

William J. Elliot; Ina Sue Miller

2004-01-01

A study was carried out to evaluate three methods for measuring low levels of hillside soil erosion associated with forest fuel management activities, and to measure erosion from cable logging and skid trails. The tipping bucket device with a sediment basin appears to be a better tool for this application than silt fences or rillmeter analysis. The greatest erosion...

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.

Erosion rate diagnostics in ion thrusters using laser-induced fluorescence

NASA Technical Reports Server (NTRS)

Gaeta, C. J.; Matossian, J. N.; Turley, R. S.; Beattie, J. R.; Williams, J. D.; Williamson, W. S.

1993-01-01

We have used laser-induced fluorescence (LIF) to monitor the charge-exchange ion erosion of the molybdenum accelerator electrode in ion thrusters. This real-time, nonintrusive method was implemented by operating a 30cm-diam ring-cusp thruster using xenon propellant. With the thruster operating at a total power of 5 kW, laser radiation at a wavelength of 390 nm (corresponding to a ground state atomic transition of molybdenum) was directed through the extracted ion beam adjacent to the downstream surface of the molybdenum accelerator electrode. Molybdenum atoms, sputtered from this surface as a result of charge-exchange ion erosion, were excited by the laser radiation. The intensity of the laser-induced fluorescence radiation, which is proportional to the sputter rate of the molybdenum atoms, was measured and correlated with variations in thruster operating conditions such as accelerator electrode voltage, accelerator electrode current, and test facility background pressure. We also demonstrated that the LIF technique has sufficient sensitivity and spatial resolution to evaluate accelerator electrode lifetime in ground-based test facilities.

Geochemical budget of erosion in the Himalayan system

NASA Astrophysics Data System (ADS)

France-Lanord, C.; Lupker, M.; Lavé, J.

2011-12-01

Geochemistry of detrital sediment allow to constrain present and past processes of erosion and may be used to infer large scale budgets. The sediment flux exported by major rivers, corresponds to net physical erosion of a basin and, if combined with the river's dissolved flux, it allows in principle to quantify total erosion rates as well as the balance between chemical and physical erosion. This is nevertheless depending on our ability to quantify riverine fluxes, sediment composition and average source rock composition. Sediment composition results from weathering, attrition, mixing and sorting processes which determine their properties at a given location and time in the drainage basin. Particle sorting during transport exerts a first order control on bulk sediment composition as well as on trace and isotopic compositions. Repeated sampling of river sediments in the Ganga and Brahmaputra Rivers during the monsoon using depth sampling combined to river velocity profiling (ACDP) show the sensitivity of sediment composition to particle sorting effects that can be linked to hydrodynamic conditions. Applied to the Ganga in Bangladesh, and using a Rousean model, we estimate the average grain size and major element composition (Si, Al, Fe) of sediments exported by the Ganga (Lupker et al. 2011, JGR E.S. in press). This leads to a net sediment flux of ca. 380 million tons/yr which is comparable to fluxes reported from hydrological measurements. The average Al/Si ratio of the sediment is 0.23 which is well bellow values reported for the Upper Continental Crust (UCC≈0.27-0.29) and slightly above estimate of the Himalayan Silicate Crust (HSC) composition deduced from a Central Nepal geological sample collection. Deviations from UCC reflect the recycled nature of Himalayan formations having undergone several orogenic cycles and being enriched in quartz. The similarity with HSC suggest that either (1) there is no segregation due to floodplain sequestration, or (2) that the

Protection from erosion following wildfire

Treesearch

Peter R. Robichaud; William J. Elliot

2006-01-01

Erosion in the first year after a wildfire can be up to three orders of magnitude greater than the erosion from undisturbed forests. To mitigate potential postfire erosion, various erosion control treatments are applied on highly erodible areas with downstream resources in need of protection. Because postfire erosion rates generally decline by an order of magnitude for...

Erosivity, surface runoff, and soil erosion estimation using GIS-coupled runoff-erosion model in the Mamuaba catchment, Brazil.

PubMed

Marques da Silva, Richarde; Guimarães Santos, Celso Augusto; Carneiro de Lima Silva, Valeriano; Pereira e Silva, Leonardo

2013-11-01

This study evaluates erosivity, surface runoff generation, and soil erosion rates for Mamuaba catchment, sub-catchment of Gramame River basin (Brazil) by using the ArcView Soil and Water Assessment Tool (AvSWAT) model. Calibration and validation of the model was performed on monthly basis, and it could simulate surface runoff and soil erosion to a good level of accuracy. Daily rainfall data between 1969 and 1989 from six rain gauges were used, and the monthly rainfall erosivity of each station was computed for all the studied years. In order to evaluate the calibration and validation of the model, monthly runoff data between January 1978 and April 1982 from one runoff gauge were used as well. The estimated soil loss rates were also realistic when compared to what can be observed in the field and to results from previous studies around of catchment. The long-term average soil loss was estimated at 9.4 t ha(-1) year(-1); most of the area of the catchment (60%) was predicted to suffer from a low- to moderate-erosion risk (<6 t ha(-1) year(-1)) and, in 20% of the catchment, the soil erosion was estimated to exceed > 12 t ha(-1) year(-1). Expectedly, estimated soil loss was significantly correlated with measured rainfall and simulated surface runoff. Based on the estimated soil loss rates, the catchment was divided into four priority categories (low, moderate, high and very high) for conservation intervention. The study demonstrates that the AvSWAT model provides a useful tool for soil erosion assessment from catchments and facilitates the planning for a sustainable land management in northeastern Brazil.

Influence of sodium dodecyl sulfate on swelling, erosion and release behavior of HPMC matrix tablets containing a poorly water-soluble drug.

PubMed

Zeng, Aiguo; Yuan, Bingxiang; Fu, Qiang; Wang, Changhe; Zhao, Guilan

2009-01-01

The effect of sodium dodecyl sulfate (SDS) on the swelling, erosion and release behavior of HPMC matrix tablets was examined. Swelling and erosion of HPMC matrix tablets were determined by measuring the wet and subsequent dry weights of matrices. The rate of uptake of the dissolution medium by the matrix was quantified using a square root relationship whilst the erosion of the polymer was described using the cube root law. The extent of swelling decreased with increasing SDS concentrations in the dissolution medium but the rate of erosion was found to follow a reverse trend. Such phenomena might have been caused by the attractive hydrophobic interaction between HPMC and SDS as demonstrated by the cloud points of the solutions containing both the surfactant and polymer. Release profiles of nimodipine from HPMC tablets in aqueous media containing different concentrations of SDS were finally studied. Increasing SDS concentrations in the medium was shown to accelerate the release of nimodipine from the tablets, possibly due to increasing nimodipine solubility and increasing rate of erosion by increasing SDS concentrations in the dissolution medium.

Fast rates of subduction erosion along the Costa Rica Pacific margin: Implications for nonsteady rates of crustal recycling at subduction zones

USGS Publications Warehouse

Vannucchi, P.; Ranero, C.R.; Galeotti, S.; Straub, S.M.; Scholl, D. W.; McDougall-Ried, K.

2003-01-01

At least since the middle Miocene (???16 Ma), subduction erosion has been the dominant process controlling the tectonic evolution of the Pacific margin of Costa Rica. Ocean Drilling Program Site 1042 recovered 16.5 Ma nearshore sediment at ???3.9 km depth, ???7 km landward of the trench axis. The overlying Miocene to Quaternary sediment contains benthic foraminifera documenting margin subsidence from upper bathyal (???200 m) to abyssal (???2000 m) depth. The rate of subsidence was low during the early to middle Miocene but increased sharply in the late Miocene-early Pliocene (5-6.5 Ma) and at the Pliocene-Pleistocene boundary (2.4 Ma). Foraminifera data, bedding dip, and the geometry of slope sediment indicate that tilting of the forearc occurred coincident with the onset of rapid late Miocene subsidence. Seismic images show that normal faulting is widespread across the continental slope; however, extension by faulting only accounts for a minor amount of the post-6.5 Ma subsidence. Basal tectonic erosion is invoked to explain the subsidence. The short-term rate of removal of rock from the forearc is about 107-123 km3 Myr-1 km-1. Mass removal is a nonsteady state process affecting the chemical balance of the arc: the ocean sediment input, with the short-term erosion rate, is a factor of 10 smaller than the eroded mass input. The low 10Be concentration in the volcanic arc of Costa Rica could be explained by dilution with eroded material. The late Miocene onset of rapid subsidence is coeval with the arrival of the Cocos Ridge at the subduction zone. The underthrusting of thick and thermally younger ocean crust decreased the subduction angle of the slab along a large segment of the margin and changed the dynamic equilibrium of the margin taper. This process may have induced the increase in the rate of subduction erosion and thus the recycling of crustal material to the mantle. Copyright 2003 by the American Geophysical Union.

Surface ages and rates of erosion at the Calico Archaeological Site in the Mojave Desert, Southern California

NASA Astrophysics Data System (ADS)

Owen, Lewis A.; Davis, Teresa; Caffee, Marc W.; Budinger, Fred; Nash, David

2011-01-01

Erosion rates and surface exposure ages were determined at the Calico Archaeological Site in the Calico Hills of the Mojave Desert, California, using 10Be terrestrial cosmogenic nuclides (TCN) methods. The Calico Hills are composed of Miocene lacustrine deposits of the Barstow Formation and fanglomerates/debris flows of the Pleistocene Yermo Deposits. These deposits are highly denuded and dissected by arroyos that have surfaces armored with chert. Surface erosion rates based on cosmogenic 10Be concentrations in stream sediments range from 19 to 39 m/Ma, with an average of 30.5 ± 6.2 m/Ma. Surface boulders have 10Be TCN ages that range from 27 ka to 198 ka, reflecting significant erosion of the Calico Hills. The oldest boulder age (197 ± 20 ka) places a minimum limit on the age of Yermo deposits. Depth profile ages at four locations within the study area have minimum ages that range from 31 to 84 ka and erosion rate-corrected surface exposure ages ranging from 43 to 139 ka. These surface exposure ages support the view that the surfaces in Yermo deposits formed during the Late Pleistocene to latest Middle Pleistocene. This chronology has important implications for interpreting the context of possible artifacts/geofacts at the site that might provide evidence for early human occupation of North America, and for reconstructing paleoenvironment change and landscape evolution in the region.

Assessment of Holocene soil erosion rates on the loess plateau in East Poland using sedimentary archives from closed depressions

NASA Astrophysics Data System (ADS)

Kołodyńska-Gawrysiak, Renata; Poesen, Jean; Gawrysiak, Leszek

2016-04-01

Closed depressions (CDs) are typical geomorphological features of the European loess belt. They are closed sedimentation basins that enable the estimation of long-term soil erosion rates for different land use environments. This study was conducted in eastern Poland (Nałęczów Plateau). In this region CDs are rather small landforms and the area of 70% of all CDs does not exceed 1500 m2. The study objective was to assess Holocene soil erosion rates in the loess plateau based on a quantitative analysis of colluvial sediments deposited in CDs. Two representative CDs were selected for this study: one CD is located in an old (long-term) forest and the other is situated in a long-term agricultural land. The maximum depth of the CD in the forest, the mean slope gradient and area of the corresponding catchment are 4.9 m, 3.410 and 7568 m² respectively. For the CD in agricultural land these values are 3.2 m, 2.760 and 5156 m² respectively. In both CDs several dozen of drillings and two trenches (2 m long, 1m wide, 2 m deep) were made in the deepest point of the CDs. Mean long-term soil erosion rates were calculated based on the stratigraphy of the soil-sediment sequence infilling the CDs. C-14 and OSL datings of soils and colluvial sediments within the CDs were obtained. For the long-term agricultural used catchment of the CD it was calculated that since 6.31 ± 0.35 ka BP the mean annual soil loss due to water and tillage erosion is 0.63-0.7 t/ha/year or 279.3 mm. In the prehistoric period since 6.31 ± 0.35 ka BP until 1026-1162 AD the mean annual soil erosion rate amounted to 0,10-0.11 t/ha/year or 41.5 mm. During the last ca. 1000 years mean soil erosion rates increased to 3.99-4.63 t/ha/year or 249.2 mm. Results of long-term soil erosion rates (calculated using colluvial sediment sequences in CDs) from agricultural catchments in the loess regions of eastern Poland (this study) and Central Belgium (Gillijns et al. 2005) are quite similar. For the forested catchment

Validating a mass balance accounting approach to using 7Be measurements to estimate event-based erosion rates over an extended period at the catchment scale

NASA Astrophysics Data System (ADS)

Porto, Paolo; Walling, Des E.; Cogliandro, Vanessa; Callegari, Giovanni

2016-07-01

Use of the fallout radionuclides cesium-137 and excess lead-210 offers important advantages over traditional methods of quantifying erosion and soil redistribution rates. However, both radionuclides provide information on longer-term (i.e., 50-100 years) average rates of soil redistribution. Beryllium-7, with its half-life of 53 days, can provide a basis for documenting short-term soil redistribution and it has been successfully employed in several studies. However, the approach commonly used introduces several important constraints related to the timing and duration of the study period. A new approach proposed by the authors that overcomes these constraints has been successfully validated using an erosion plot experiment undertaken in southern Italy. Here, a further validation exercise undertaken in a small (1.38 ha) catchment is reported. The catchment was instrumented to measure event sediment yields and beryllium-7 measurements were employed to document the net soil loss for a series of 13 events that occurred between November 2013 and June 2015. In the absence of significant sediment storage within the catchment's ephemeral channel system and of a significant contribution from channel erosion to the measured sediment yield, the estimates of net soil loss for the individual events could be directly compared with the measured sediment yields to validate the former. The close agreement of the two sets of values is seen as successfully validating the use of beryllium-7 measurements and the new approach to obtain estimates of net soil loss for a sequence of individual events occurring over an extended period at the scale of a small catchment.

Solid motor aft closure insulation erosion. [heat flux correlation for rate analysis

NASA Technical Reports Server (NTRS)

Stampfl, E.; Landsbaum, E. M.

1973-01-01

The erosion rate of aft closure insulation in a number of large solid propellant motors was empirically analyzed by correlating the average ablation rate with a number of variables that had previously been demonstrated to affect heat flux. The main correlating parameter was a heat flux based on the simplified Bartz heat transfer coefficient corrected for two-dimensional effects. A multiplying group contained terms related to port-to-throat ratio, local wall angle, grain geometry and nozzle cant angle. The resulting equation gave a good correlation and is a useful design tool.

Erosion rates from forests and rangelands following fuel management

Treesearch

William J. Elliot; Peter R. Robichaud; I. Sue Miller

2007-01-01

In both forest and rangelands, fuel reduction operations are now common practices. Mechanical thinning followed by prescribed fire is common in forests, while fire is frequently applied to rangelands. Studies at different scales (50 sq m to 389 ha) measure the erosion from fuel management. This presentation compares runoff and erosion from these studies. Plot size has...

Wear rate quantifying in real-time using the charged particle surface activation

NASA Astrophysics Data System (ADS)

Alexandreanu, B.; Popa-Simil, L.; Voiculescu, D.; Racolta, P. M.

1997-02-01

Surface activation, commonly known as Thin Layer Activation (TLA), is currently employed in over 30 accelerator laboratories around the world for wear and/or corrosion monitoring in industrial plants [1-6]. TLA was primarily designed and developed to meet requirements of potential industrial partners, in order to transfer this technique from research to industry. The method consists of accelerated ion bombardment of a surface of interest, e.g., a machine part subjected to wear. Loss of material owing to wear, erosive corrosion or abrasion is characterized by monitoring the resultant changes in radioactivity. In principle, depending upon the case at hand, one may choose to measure either the remnant activity of the component of interest or to monitor the activity of the debris. For applications of the second type, especially when a lubricating agent is involved, dedicated installations have been constructed and adapted to an engine or a tribological testing stand in order to assure oil circulation around an externally placed detection gauge. This way, the wear particles suspended in the lubricant can be detected and the material loss rates quantified in real time. Moreover, in specific cases, such as the one presented in this paper, remnant activity measurements prove to be useful tools for complementary results. This paper provides a detailed presentation of such a case: in situ resistance-to-wear testing of two types of piston rings.

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.

Climatic controls on the pace of glacier erosion

NASA Astrophysics Data System (ADS)

Koppes, Michele; Hallet, Bernard; Rignot, Eric; Mouginot, Jeremie; Wellner, Julia; Love, Katherine

2016-04-01

Mountain ranges worldwide have undergone large-scale modification due the erosive action of ice, 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, suggesting that modern erosion rates exceed orogenic rates by 2-3 orders of magnitude. These modern rates are presumed to be due to dynamic acceleration of the ice masses during deglaciation and retreat. Recent numerical models have focused on replicating the processes that produce the geomorphic signatures of glacial landscapes. Central to these models is a simple quantitative index that relates erosion rate to ice dynamics and to climate. To provide such an index, we examined explicitly the factors controlling modern glacier erosion rates across climatic regimes. Holding tectonic history, bedrock lithology and glacier hypsometries relatively constant across a latitudinal transect 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 for temperate tidewater glaciers to 0.01-<0.1 mm yr-1 for polar outlet glaciers, 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 theory. The general relationship between ice dynamics and erosion suggests that the erosion rate scales non-linearly with basal sliding speed, with an exponent n ≈ 2-2.62. Notably, erosion rates decrease by over two orders of magnitude between temperate and polar glaciers with similar ice 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

[Erosive petechial gastritis].

PubMed

Llorens, P

1988-01-01

We studied 20 patients in which a variety of erosive gastritis is described. We named it petechial erosive gastritis. We have to bring up that its sequence is due to the presence of the petechiae in the center of the mucosal area. Then in degrees of higher intensity erosions occur also at the center of the area mucosa. Occasionally the erosions meet, become larger and may bleed. An endoscopic classification of petechial erosive gastritis is established it rates mild, moderate, severe and hemorrhagic degrees. Even if the histopathologic study does not keep a strict correspondence with the severity of endoscopic observation of the lesions, it is possible to separate easily a petechial stage from an erosive stage. Demonstration of these lesions at their sequence from petechial to bleeding erosion constitutes an important contribution to the study of acute gastric lesions and it might open a way to a better study of the alterations of the irrigation of the gastric mucosa and the etiology of erosive lesions and acute ulcer.

Radar-derived asteroid shapes point to a 'zone of stability' for topography slopes and surface erosion rates

NASA Astrophysics Data System (ADS)

Richardson, J.; Graves, K.; Bowling, T.

2014-07-01

Previous studies of the combined effects of asteroid shape, spin, and self-gravity have focused primarily upon the failure limits for bodies with a variety of standard shapes, friction, and cohesion values [1,2,3]. In this study, we look in the opposite direction and utilize 22 asteroid shape-models derived from radar inversion [4] and 7 small body shape-models derived from spacecraft observations [5] to investigate the region in shape/spin space [1,2] wherein self-gravity and rotation combine to produce a stable minimum state with respect to surface potential differences, dynamic topography, slope magnitudes, and erosion rates. This erosional minimum state is self-correcting, such that changes in the body's rotation rate, either up or down, will increase slope magnitudes across the body, thereby driving up erosion rates non-linearly until the body has once again reached a stable, minimized surface state [5]. We investigated this phenomenon in a systematic fashion using a series of synthesized, increasingly prolate spheroid shape models. Adjusting the rotation rate of each synthetic shape to minimize surface potential differences, dynamic topography, and slope magnitudes results in the magenta curve of the figure (right side), defining the zone of maximum surface stability (MSS). This MSS zone is invariant both with respect to body size (gravitational potential and rotational potential scale together with radius), and density when the scaled-spin of [2] is used. Within our sample of observationally derived small-body shape models, slow rotators (Group A: blue points), that are not in the maximum surface stability (MSS) zone and where gravity dominates the slopes, will generally experience moderate erosion rates (left plot) and will tend to move up and to the right in shape/spin space as the body evolves (right plot). Fast rotators (Group C: red points), that are not in the MSS zone and where spin dominates the slopes, will generally experience high erosion rates

The effect of wet-dry weathering on the rate of bedrock river channel erosion by saltating gravel

USGS Publications Warehouse

Inoue, Takuya; Yamaguchi, Satomi; Nelson, Jonathan M.

2017-01-01

Previous work has shown that the bedrock erosion rate E because of collisions of saltating bedload can be expressed by E = βqb(1-Pc), where qb is the sediment transport rate, Pc is the extent of alluvial cover, and β is the abrasion coefficient. However, the dependence of the abrasion coefficient on the physical characteristics of the bedrock material is poorly known, and in particular, the effects of wet-dry weathering on the saltation-abrasion bedrock incision has not been specifically characterized. Observation suggests that the typical wet-dry cycling of exposed bedrock in river beds gives rise to cracks and voids that are likely to alter the incision rate of the material when subjected to impacts of moving sediment. In this study, flume experiments are performed to develop an understanding of how wet-dry cycling affects the rock tensile strength and the bedrock erosion rate. To represent the physical effects of weathering, boring cores taken from natural bedrock channel are exposed to artificial wet-dry cycles. The experimental results suggest the following: (1) the abrasion coefficient for fresh bedrock is estimated by β = 1.0 × 10− 4σT− 2(d/ksb)0.5, where σT is the tensile strength, d is the diameter of colliding gravel, and ksb is the hydraulic roughness height of bedrock; (2) the tensile strength of the bedrock decreases exponentially as a result of repeated wet-dry cycles, σT/σT0 = exp (-CTNWa0/σT0), where σT0 is the initial tensile strength, Wa0 is the initial normalized rate of water absorption., N is the number of wet-dry cycles, and CT is a constant; (3) the erosion rate of fresh bedrock depends on the inverse of the square of tensile strength, but the erosion rate of weathered bedrock depends on the − 1.5 power of tensile strength.

Scenario Studies on Effects of Soil Infiltration Rates, Land Slope, and Furrow Irrigation Characteristics on Furrow Irrigation-Induced Erosion.

PubMed

Dibal, Jibrin M; Ramalan, A A; Mudiare, O J; Igbadun, H E

2014-01-01

Furrow irrigation proceeds under several soil-water-furrow hydraulics interaction dynamics. The soil erosion consequences from such interactions in furrow irrigation in Samaru had remained uncertain. A furrow irrigation-induced erosion (FIIE) model was used to simulate the potential severity of soil erosion in irrigated furrows due to interactive effects of infiltration rates, land slope, and some furrow irrigation characteristics under different scenarios. The furrow irrigation characteristics considered were furrow lengths, widths, and stream sizes. The model itself was developed using the dimensional analysis approach. The scenarios studied were the interactive effects of furrow lengths, furrow widths, and slopes steepness; infiltration rates and furrow lengths; and stream sizes, furrow lengths, and slopes steepness on potential furrow irrigation-induced erosion, respectively. The severity of FIIE was found to relate somewhat linearly with slope and stream size, and inversely with furrow lengths and furrow width. The worst soil erosion (378.05 t/ha/yr) was found as a result of the interactive effects of 0.65 m furrow width, 50 m furrow length, and 0.25% slope steepness; and the least soil erosion (0.013 t/ha/yr) was induced by the combined effects of 0.5 l/s, 200 m furrow length, and 0.05% slope steepness. Evidently considering longer furrows in furrow irrigation designs would be a better alternative of averting excessive FIIE.

Measurements of erosion potential using Gust chamber in Yolo Bypass near Sacramento, California

USGS Publications Warehouse

Work, Paul A.; Schoellhamer, David H.

2018-04-27

This report describes work performed to quantify the erodibility of surface soils in the Yolo Bypass (Bypass) near Sacramento, California, for use in the California Department of Water Resources (DWR) Yolo Bypass D-MCM mercury model. The Bypass, when not serving as a floodway, is heavily utilized for agriculture. During flood events, surface water flows over the soil, resulting in the application of a shear stress to the soil. The shear stress is a function of flow speed and is often assumed to vary as the square of flow speed. Once the shear stress reaches a critical value, erosion commences, and the erosion rate typically increases with applied shear stress. The goal of the work described here was to quantify this process and how it varies throughout the major land uses found in the Yolo Bypass.Each of the major land uses found in the Bypass was targeted for sediment coring and two side-by-side cores, 10 centimeters in diameter, were extracted at each site for testing in a Gust erosion chamber. This device consists of a cylinder with a piston and cap installed to contain a sediment sample and overlying water. In most instances, coring was done with the cylinder, the piston and cap were installed, and testing commenced immediately. The cap at the top of the cylinder contains vanes to induce rotation of the flow and is driven by an electric motor, simulating the bed shear stress experienced by the soil in a flood event. Ambient water is introduced to the cylinder, passes through the device, and carries eroded sediment out of the chamber. The exiting water is tested for turbidity, and water samples obtained to relate turbidity to suspended sediment concentration are used to compute erosion rates for each of the applied shear stresses.The result for each sediment core is (1) definition of the critical shear stress required to initiate sediment erosion and (2) estimation of coefficients required to relate erosion rate to applied shear

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

Climate change impacts on soil erosion in the Great Lakes Region

USDA-ARS?s Scientific Manuscript database

Quantifying changes in potential soil erosion under projections of changing climate is important for the sustainable management of land resources, especially for regions dominated by agricultural land use, as soil loss estimates will be helpful in identifying areas susceptible to erosion, targeting ...

Multi-temporal Soil Erosion Modelling over the Mt Kenya Region with Multi-Sensor Earth Observation Data

NASA Astrophysics Data System (ADS)

Symeonakis, Elias; Higginbottom, Thomas

2015-04-01

Accelerated soil erosion is the principal cause of soil degradation across the world. In Africa, it is seen as a serious problem creating negative impacts on agricultural production, infrastructure and water quality. Regarding the Mt Kenya region, specifically, soil erosion is a serious threat mainly due to unplanned and unsustainable practices linked to tourism, agriculture and rapid population growth. The soil types roughly correspond with different altitudinal zones and are generally very fertile due to their volcanic origin. Some of them have been created by eroding glaciers while others are due to millions of years of fluvial erosion. The soils on the mountain are easily eroded once exposed: when vegetation is removed, the soil quickly erodes down to bedrock by either animals or humans, as tourists erode paths and local people clear large swaths of forested land for agriculture, mostly illegally. It is imperative, therefore, that a soil erosion monitoring system for the Mt Kenya region is in place in order to understand the magnitude of, and be able to respond to, the increasing number of demands on this renewable resource. In this paper, we employ a simple regional-scale soil erosion modelling framework based on the Thornes model and suggest an operational methodology for quantifying and monitoring water runoff and soil erosion using multi-sensor and multi-temporal remote sensing data in a GIS framework. We compare the estimates of this study with general data on the severity of soil erosion over Kenya and with measured rates of soil loss at different locations over the area of study. The results show that the measured and estimated rates of erosion are generally similar and within the same order of magnitude. They also show that, over the last years, erosion rates are increasing in large parts of the region at an alarming rate, and that mitigation measures are needed to reverse the negative effects of uncontrolled socio-economic practices.

The comparison of various approach to evaluation erosion risks and design control erosion measures

NASA Astrophysics Data System (ADS)

Kapicka, Jiri

2015-04-01

In the present is in the Czech Republic one methodology how to compute and compare erosion risks. This methodology contain also method to design erosion control measures. The base of this methodology is Universal Soil Loss Equation (USLE) and their result long-term average annual rate of erosion (G). This methodology is used for landscape planners. Data and statistics from database of erosion events in the Czech Republic shows that many troubles and damages are from local episodes of erosion events. An extent of these events and theirs impact are conditional to local precipitation events, current plant phase and soil conditions. These erosion events can do troubles and damages on agriculture land, municipally property and hydro components and even in a location is from point of view long-term average annual rate of erosion in good conditions. Other way how to compute and compare erosion risks is episodes approach. In this paper is presented the compare of various approach to compute erosion risks. The comparison was computed to locality from database of erosion events on agricultural land in the Czech Republic where have been records two erosion events. The study area is a simple agriculture land without any barriers that can have high influence to water flow and soil sediment transport. The computation of erosion risks (for all methodology) was based on laboratory analysis of soil samples which was sampled on study area. Results of the methodology USLE, MUSLE and results from mathematical model Erosion 3D have been compared. Variances of the results in space distribution of the places with highest soil erosion where compared and discussed. Other part presents variances of design control erosion measures where their design was done on based different methodology. The results shows variance of computed erosion risks which was done by different methodology. These variances can start discussion about different approach how compute and evaluate erosion risks in areas

Potential impacts of climate change on soil erosion vulnerability across the conterminous United States

Treesearch

C. Segura; G. Sun; S. McNulty; Y. Zhang

2014-01-01

Rainfall runoff erosivity (R) is one key climate factor that controls water erosion. Quantifying the effects of climate change-induced erosivity change is important for identifying critical regions prone to soil erosion under a changing environment. In this study we first evaluate the changes of R from 1970 to 2090 across the United States under nine climate conditions...

Short communication: Massive erosion in monsoonal central India linked to late Holocene land cover degradation

NASA Astrophysics Data System (ADS)

Giosan, Liviu; Ponton, Camilo; Usman, Muhammed; Blusztajn, Jerzy; Fuller, Dorian Q.; Galy, Valier; Haghipour, Negar; Johnson, Joel E.; McIntyre, Cameron; Wacker, Lukas; Eglinton, Timothy I.

2017-12-01

Soil erosion plays a crucial role in transferring sediment and carbon from land to sea, yet little is known about the rhythm and rates of soil erosion prior to the most recent few centuries. Here we reconstruct a Holocene erosional history from central India, as integrated by the Godavari River in a sediment core from the Bay of Bengal. We quantify terrigenous fluxes, fingerprint sources for the lithogenic fraction and assess the age of the exported terrigenous carbon. Taken together, our data show that the monsoon decline in the late Holocene significantly increased soil erosion and the age of exported organic carbon. This acceleration of natural erosion was later exacerbated by the Neolithic adoption and Iron Age extensification of agriculture on the Deccan Plateau. Despite a constantly elevated sea level since the middle Holocene, this erosion acceleration led to a rapid growth of the continental margin. We conclude that in monsoon conditions aridity boosts rather than suppresses sediment and carbon export, acting as a monsoon erosional pump modulated by land cover conditions.

A simplified 137Cs transport model for estimating erosion rates in undisturbed soil.

PubMed

Zhang, Xinbao; Long, Yi; He, Xiubin; Fu, Jiexiong; Zhang, Yunqi

2008-08-01

(137)Cs is an artificial radionuclide with a half-life of 30.12 years which released into the environment as a result of atmospheric testing of thermo-nuclear weapons primarily during the period of 1950s-1970s with the maximum rate of (137)Cs fallout from atmosphere in 1963. (137)Cs fallout is strongly and rapidly adsorbed by fine particles in the surface horizons of the soil, when it falls down on the ground mostly with precipitation. Its subsequent redistribution is associated with movements of the soil or sediment particles. The (137)Cs nuclide tracing technique has been used for assessment of soil losses for both undisturbed and cultivated soils. For undisturbed soils, a simple profile-shape model was developed in 1990 to describe the (137)Cs depth distribution in profile, where the maximum (137)Cs occurs in the surface horizon and it exponentially decreases with depth. The model implied that the total (137)Cs fallout amount deposited on the earth surface in 1963 and the (137)Cs profile shape has not changed with time. The model has been widely used for assessment of soil losses on undisturbed land. However, temporal variations of (137)Cs depth distribution in undisturbed soils after its deposition on the ground due to downward transport processes are not considered in the previous simple profile-shape model. Thus, the soil losses are overestimated by the model. On the base of the erosion assessment model developed by Walling, D.E., He, Q. [1999. Improved models for estimating soil erosion rates from cesium-137 measurements. Journal of Environmental Quality 28, 611-622], we discuss the (137)Cs transport process in the eroded soil profile and make some simplification to the model, develop a method to estimate the soil erosion rate more expediently. To compare the soil erosion rates calculated by the simple profile-shape model and the simple transport model, the soil losses related to different (137)Cs loss proportions of the reference inventory at the Kaixian

The contribution of mulches to control high soil erosion rates in vineyards in Eastern Spain

NASA Astrophysics Data System (ADS)

Cerdà, Artemi; Jordán, Antonio; Zavala, Lorena; José Marqués, María; Novara, Agata

2014-05-01

Soil erosion take place in degraded ecosystem where the lack of vegetation, drought, erodible parent material and deforestation take place (Borelli et al., 2013; Haregeweyn et al., 2013; Zhao et al., 2013). Agriculture management developed new landscapes (Ore and Bruins, 2012) and use to trigger non-sustainable soil erosion rates (Zema et al., 2012). High erosion rates were measured in agriculture land (Cerdà et al., 2009), but it is also possible to develop managements that will control the soil and water losses, such as organic amendments (Marqués et al., 2005), plant cover (Marqués et al., 2007) and geotextiles (Giménez Morera et al., 2010). The most successful management to restore the structural stability and the biological activity of the agriculture soil has been the organic mulches (García Orenes et al; 2009; 2010; 2012). The straw mulch is also very successful on bare fire affected soil (Robichaud et al., 2013a; 2013b), which also contributes to a more stable soil moisture content (García-Moreno et al., 2013). The objective of this research is to determine the impact of two mulches: wheat straw and chipped branches, on the soil erosion rates in a rainfed vineyard in Eastern Spain. The research site is located in the Les Alcusses Valley within the Moixent municipality. The Mean annual temperature is 13 ºC, and the mean annual rainfall 455 mm. Soil are sandy loam, and are developed at the foot-slope of a Cretaceous limestone range, the Serra Grossa range. The soils use to be ploughed and the features of soil erosion are found after each thunderstorm. Rills are removed by ploughing. Thirty rainfall simulation experiments were carried out in summer 2011 during the summer drought period. The simulated rainfall lasted during 1 hour at a 45 mmh-1 intensity on 1 m2 plots (Cerdà and Doerr, 2010; Cerdà and Jurgensen 2011). Ten experiments were carried out on the control plots (ploughed), 10 on straw mulch covered plots, and 10 on chipped branches covered

Riparian erosion vulnerability model based on environmental features.

PubMed

Botero-Acosta, Alejandra; Chu, Maria L; Guzman, Jorge A; Starks, Patrick J; Moriasi, Daniel N

2017-12-01

Riparian erosion is one of the major causes of sediment and contaminant load to streams, degradation of riparian wildlife habitats, and land loss hazards. Land and soil management practices are implemented as conservation and restoration measures to mitigate the environmental problems brought about by riparian erosion. This, however, requires the identification of vulnerable areas to soil erosion. Because of the complex interactions between the different mechanisms that govern soil erosion and the inherent uncertainties involved in quantifying these processes, assessing erosion vulnerability at the watershed scale is challenging. The main objective of this study was to develop a methodology to identify areas along the riparian zone that are susceptible to erosion. The methodology was developed by integrating the physically-based watershed model MIKE-SHE, to simulate water movement, and a habitat suitability model, MaxEnt, to quantify the probability of presences of elevation changes (i.e., erosion) across the watershed. The presences of elevation changes were estimated based on two LiDAR-based elevation datasets taken in 2009 and 2012. The changes in elevation were grouped into four categories: low (0.5 - 0.7 m), medium (0.7 - 1.0 m), high (1.0 - 1.7 m) and very high (1.7 - 5.9 m), considering each category as a studied "species". The categories' locations were then used as "species location" map in MaxEnt. The environmental features used as constraints to the presence of erosion were land cover, soil, stream power index, overland flow, lateral inflow, and discharge. The modeling framework was evaluated in the Fort Cobb Reservoir Experimental watershed in southcentral Oklahoma. Results showed that the most vulnerable areas for erosion were located at the upper riparian zones of the Cobb and Lake sub-watersheds. The main waterways of these sub-watersheds were also found to be prone to streambank erosion. Approximatively 80% of the riparian zone (streambank

Age-erosion constraints on an Early Pleistocene paleosol in Yukon, Canada, with profiles of 10Be and 26Al: Evidence for a significant loess cover effect on cosmogenic nuclide production rates

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

Hidy, Alan J.; Gosse, John C.; Sanborn, Paul

We report that Wounded Moose type paleosols developed on remnant deposits of Late Pliocene to Early Pleistocene [pre-Reid] Cordilleran Ice Sheet [CIS] glaciations in central Yukon, Canada. It is an important regional soil-geomorphic marker at the boundary between early CIS advances and the non-glaciated regions of Yukon and Alaska. Yet, at present, its age is poorly constrained between the Reid [0.2 Ma] and earliest [2.84 Ma] CIS advances. Here, we apply depth profiles of in situ-produced cosmogenic 26Al and 10Be to obtain both a minimum exposure age [1.12 +0.44/ -0.36 Ma, 2σ] and maximum erosion rate [1.1 +0.9/ -0.5 mmore » Myr -1] for the Wounded Moose paleosol. Here, our results show that this soil formed under exceptionally stable conditions [max erosion rate similar to polar bedrock erosion rates] and that it pre-dates the emergence of the 100 ka [eccentricity] climate cycle. Contrasting our results from single- and joint-nuclide depth profile models reveals a significant discrepancy between calculated and effective 10Be and 26Al production rates [40–65% of expected values]. We interpret this discrepancy as the result of intermittent loess cover—with a time-averaged depth between 60 and 110 cm—which significantly reduced apparent exposure ages obtained from the single–nuclide model. The observation of such a significant loess-cover effect on cosmogenic nuclide production has implications for exposure dating in glacial and periglacial environments; a multi-nuclide sampling strategy is required to quantify this effect.« less

Age-erosion constraints on an Early Pleistocene paleosol in Yukon, Canada, with profiles of 10Be and 26Al: Evidence for a significant loess cover effect on cosmogenic nuclide production rates

DOE PAGES

Hidy, Alan J.; Gosse, John C.; Sanborn, Paul; ...

2018-02-16

We report that Wounded Moose type paleosols developed on remnant deposits of Late Pliocene to Early Pleistocene [pre-Reid] Cordilleran Ice Sheet [CIS] glaciations in central Yukon, Canada. It is an important regional soil-geomorphic marker at the boundary between early CIS advances and the non-glaciated regions of Yukon and Alaska. Yet, at present, its age is poorly constrained between the Reid [0.2 Ma] and earliest [2.84 Ma] CIS advances. Here, we apply depth profiles of in situ-produced cosmogenic 26Al and 10Be to obtain both a minimum exposure age [1.12 +0.44/ -0.36 Ma, 2σ] and maximum erosion rate [1.1 +0.9/ -0.5 mmore » Myr -1] for the Wounded Moose paleosol. Here, our results show that this soil formed under exceptionally stable conditions [max erosion rate similar to polar bedrock erosion rates] and that it pre-dates the emergence of the 100 ka [eccentricity] climate cycle. Contrasting our results from single- and joint-nuclide depth profile models reveals a significant discrepancy between calculated and effective 10Be and 26Al production rates [40–65% of expected values]. We interpret this discrepancy as the result of intermittent loess cover—with a time-averaged depth between 60 and 110 cm—which significantly reduced apparent exposure ages obtained from the single–nuclide model. The observation of such a significant loess-cover effect on cosmogenic nuclide production has implications for exposure dating in glacial and periglacial environments; a multi-nuclide sampling strategy is required to quantify this effect.« less

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.

Rating educational quality: factors in the erosion of professional standards.

PubMed

Albanese, M

1999-06-01

Changes in the health care environment are putting increasing pressure on medical schools to make faculty accountable and to document the quality of the medical education they provide. Faculty's ratings of students' performances and students' ratings of faculty's teaching are important elements in these efforts to document educational quality. This article discusses selected research related to factors affecting raters' judgments, analyzes how changes in the health care environment are influencing such judgments, and links these influences to the system that upholds professional standards. Ratings are known to have a positive bias (generosity error), provide limited discrimination, and often fail to document serious deficits. The potential sources of these problems relate to the mechanics of the rating task, the system used to obtain ratings, and factors affecting rater judgment. As managed care demands reduce the time faculty have for teaching, as system-wide disincentives to provide negative ratings proliferate, and as social engineering challenges, such as the Americans with Disabilities Act, impose differential standards for students, the natural tendency to avoid giving negative ratings becomes even harder to resist. Ultimately, these forces compromise the capability of faculty to uphold the standards of the profession. The author calls for a national effort to stem the erosion of those standards.

Frost for the trees: Did climate increase erosion in unglaciated landscapes during the late Pleistocene?

PubMed Central

Marshall, Jill A.; Roering, Joshua J.; Bartlein, Patrick J.; Gavin, Daniel G.; Granger, Darryl E.; Rempel, Alan W.; Praskievicz, Sarah J.; Hales, Tristram C.

2015-01-01

Understanding climatic influences on the rates and mechanisms of landscape erosion is an unresolved problem in Earth science that is important for quantifying soil formation rates, sediment and solute fluxes to oceans, and atmospheric CO2 regulation by silicate weathering. Glaciated landscapes record the erosional legacy of glacial intervals through moraine deposits and U-shaped valleys, whereas more widespread unglaciated hillslopes and rivers lack obvious climate signatures, hampering mechanistic theory for how climate sets fluxes and form. Today, periglacial processes in high-elevation settings promote vigorous bedrock-to-regolith conversion and regolith transport, but the extent to which frost processes shaped vast swaths of low- to moderate-elevation terrain during past climate regimes is not well established. By combining a mechanistic frost weathering model with a regional Last Glacial Maximum (LGM) climate reconstruction derived from a paleo-Earth System Model, paleovegetation data, and a paleoerosion archive, we propose that frost-driven sediment production was pervasive during the LGM in our unglaciated Pacific Northwest study site, coincident with a 2.5 times increase in erosion relative to modern rates. Our findings provide a novel framework to quantify how climate modulates sediment production over glacial-interglacial cycles in mid-latitude unglaciated terrain. PMID:26702434

Frost for the trees: Did climate increase erosion in unglaciated landscapes during the late Pleistocene?

PubMed

Marshall, Jill A; Roering, Joshua J; Bartlein, Patrick J; Gavin, Daniel G; Granger, Darryl E; Rempel, Alan W; Praskievicz, Sarah J; Hales, Tristram C

2015-11-01

Understanding climatic influences on the rates and mechanisms of landscape erosion is an unresolved problem in Earth science that is important for quantifying soil formation rates, sediment and solute fluxes to oceans, and atmospheric CO2 regulation by silicate weathering. Glaciated landscapes record the erosional legacy of glacial intervals through moraine deposits and U-shaped valleys, whereas more widespread unglaciated hillslopes and rivers lack obvious climate signatures, hampering mechanistic theory for how climate sets fluxes and form. Today, periglacial processes in high-elevation settings promote vigorous bedrock-to-regolith conversion and regolith transport, but the extent to which frost processes shaped vast swaths of low- to moderate-elevation terrain during past climate regimes is not well established. By combining a mechanistic frost weathering model with a regional Last Glacial Maximum (LGM) climate reconstruction derived from a paleo-Earth System Model, paleovegetation data, and a paleoerosion archive, we propose that frost-driven sediment production was pervasive during the LGM in our unglaciated Pacific Northwest study site, coincident with a 2.5 times increase in erosion relative to modern rates. Our findings provide a novel framework to quantify how climate modulates sediment production over glacial-interglacial cycles in mid-latitude unglaciated terrain.

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

Comparison of unmanned aircraft systems (UAS) to LiDAR for streambank erosion measurement at the site-specific and river network scales

NASA Astrophysics Data System (ADS)

Hamshaw, S. D.; Dewoolkar, M. M.; Rizzo, D.; ONeil-Dunne, J.; Frolik, J.

2016-12-01

Measurement of rates and extent of streambank erosion along river corridors is an important component of many catchment studies and necessary for engineering projects such as river restoration, hazard assessment, and total maximum daily load (TMDL) development. A variety of methods have been developed to quantify streambank erosion, including bank pins, ground surveys, photogrammetry, LiDAR, and analytical models. However, these methods are not only resource intensive, but many are feasible and appropriate only for site-specific studies and not practical for erosion estimates at larger scales. Recent advancements in unmanned aircraft systems (UAS) and photogrammetry software provide capabilities for more rapid and economical quantification of streambank erosion and deposition at multiple scales (from site-specific to river network). At the site-specific scale, the capability of UAS to quantify streambank erosion was compared to terrestrial laser scanning (TLS) and RTK-GPS ground survey and assessed at seven streambank monitoring sites in central Vermont. Across all sites, the UAS-derived bank topography had mean errors of 0.21 m compared to TLS and GPS data. Highest accuracies were achieved in early spring conditions where mean errors approached 10 cm. The cross sectional area of bank erosion at a typical, vegetated streambank site was found to be reliably calculated within 10% of actual for erosion areas greater than 3.5 m2. At the river network-level scale, 20 km of river corridor along the New Haven, Winooski, and Mad Rivers was flown on multiple dates with UAS and used to generate digital elevation models (DEMs) that were then compared for change detection analysis. Airborne LiDAR data collected prior to UAS surveys was also compared to UAS data to determine multi-year rates of bank erosion. UAS-based photogrammetry for generation of fine scale topographic data shows promise for the monitoring of streambank erosion both at the individual site scale and river

Spatial Analysis of Coastal Erosion over Five Decades near Barrow, Alaska

NASA Astrophysics Data System (ADS)

Manley, W. F.

2004-12-01

There has been increasing interest in processes affecting Arctic coastlines, including shoreline erosion. The prospect of continued -- and possibly accelerated -- coastal erosion is a major concern for many Arctic communities. Documenting and understanding spatial variability in erosion rates are increasingly attainable as high-resolution imagery becomes available, and as GIS and remote-sensing tools are more widely accepted. This study presents such an analysis for a broad area near Barrow, Alaska. Shoreline erosion and accretion were quantified by comparison of coregistered datasets and imagery. Orthorectified Radar Imagery (ORRI) was acquired in July, 2002 at 1.25 m resolution. Twenty frames of aerial photos from August, 1955 were scanned and georectified to the ORRI using a polynomial transformation in ArcGIS, with resulting resolution of about 1.4 m and RMS error of 2.6 m. The 2002 and 1955 shorelines were digitized with points spaced every 20 m along the 250 km of mainland coastline. For barrier islands and the Barrow Spit, the 1955 coastline was digitized from DRG files depicting the USGS 15-minute maps. Using a variety of vector ArcInfo commands, horizontal displacement of the mainland shoreline was converted to erosion and accretion rates for the intervening 47 years. (Note that time-averaged rates will underrepresent episodically high rates during storm events). Overall error considering georectification, digitizing, and transient waterline shifts due to microtidal fluctuation and wave-set up is approx. 3.1 m for the mainland coast, equating with 0.07 m/yr. For barrier features, where the DRG's are less accurate, error is about 28 m (0.6 m/yr). Nearly all of the mainland coast (91%) has experienced erosion. Highly variable, rates average -0.91 m/yr, with an average horizontal shoreline displacement of -42.5 m. (Rates and displacements are negative for erosion). Relatively low rates of about -0.3 m/yr occur along the Chukchi coast, where sand- and gravel

Mechanical weathering and rock erosion by climate-dependent subcritical cracking

NASA Astrophysics Data System (ADS)

Eppes, Martha-Cary; Keanini, Russell

2017-06-01

This work constructs a fracture mechanics framework for conceptualizing mechanical rock breakdown and consequent regolith production and erosion on the surface of Earth and other terrestrial bodies. Here our analysis of fracture mechanics literature explicitly establishes for the first time that all mechanical weathering in most rock types likely progresses by climate-dependent subcritical cracking under virtually all Earth surface and near-surface environmental conditions. We substantiate and quantify this finding through development of physically based subcritical cracking and rock erosion models founded in well-vetted fracture mechanics and mechanical weathering, theory, and observation. The models show that subcritical cracking can culminate in significant rock fracture and erosion under commonly experienced environmental stress magnitudes that are significantly lower than rock critical strength. Our calculations also indicate that climate strongly influences subcritical cracking—and thus rock weathering rates—irrespective of the source of the stress (e.g., freezing, thermal cycling, and unloading). The climate dependence of subcritical cracking rates is due to the chemophysical processes acting to break bonds at crack tips experiencing these low stresses. We find that for any stress or combination of stresses lower than a rock's critical strength, linear increases in humidity lead to exponential acceleration of subcritical cracking and associated rock erosion. Our modeling also shows that these rates are sensitive to numerous other environment, rock, and mineral properties that are currently not well characterized. We propose that confining pressure from overlying soil or rock may serve to suppress subcritical cracking in near-surface environments. These results are applicable to all weathering processes.

A Study of Cavitation Erosion

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

Hiromu Isaka; Masatsugu Tsutsumi; Tadashi Shiraishi

2002-07-01

The authors performed experimental study for the purpose of the following two items from a viewpoint of cavitation erosion of a cylindrical orifice in view of a problem at the letdown orifice in PWR (Pressurized Water Reactor). 1. To get the critical cavitation parameter of the cylindrical orifice to establish the design criteria for prevention of cavitation erosion, and 2. to ascertain the erosion rate in such an eventuality that the cavitation erosion occurs with the orifice made of stainless steel with precipitation hardening (17-4-Cu hardening type stainless steel), so that we confirm the appropriateness of the design criteria. Regardingmore » the 1. item, we carried out the cavitation tests to get the critical cavitation parameters inside and downstream of the orifice. The test results showed that the cavitation parameter at inception is independent of the length or the diameter of the orifice. Moreover, the design criteria of cavitation erosion of cylindrical orifices have been established. Regarding the 2. item, we tested the erosion rate under high-pressure conditions. The cavitation erosion actually occurred in the cylindrical orifice at the tests that was strongly resemble to the erosion occurred at the plant. It will be seldom to reproduce resemble cavitation erosion in a cylindrical orifice with the hard material used at plants. We could establish the criteria for preventing the cavitation erosion from the test results. (authors)« less

Using (137)Cs measurements to estimate soil erosion rates in the Pčinja and South Morava River Basins, southeastern Serbia.

PubMed

Petrović, Jelena; Dragović, Snežana; Dragović, Ranko; Đorđević, Milan; Đokić, Mrđan; Zlatković, Bojan; Walling, Desmond

2016-07-01

The need for reliable assessments of soil erosion rates in Serbia has directed attention to the potential for using (137)Cs measurements to derive estimates of soil redistribution rates. Since, to date, this approach has not been applied in southeastern Serbia, a reconnaissance study was undertaken to confirm its viability. The need to take account of the occurrence of substantial Chernobyl fallout was seen as a potential problem. Samples for (137)Cs measurement were collected from a zone of uncultivated soils in the watersheds of Pčinja and South Morava Rivers, an area with known high soil erosion rates. Two theoretical conversion models, the profile distribution (PD) model and diffusion and migration (D&M) model were used to derive estimates of soil erosion and deposition rates from the (137)Cs measurements. The estimates of soil redistribution rates derived by using the PD and D&M models were found to differ substantially and this difference was ascribed to the assumptions of the simpler PD model that cause it to overestimate rates of soil loss. The results provided by the D&M model were judged to more reliable. Copyright © 2016 Elsevier Ltd. All rights reserved.

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

Experimental study on copper cathode erosion rate and rotational velocity of magnetically driven arcs in a well-type cathode non-transferred plasma torch operating in air

NASA Astrophysics Data System (ADS)

Chau, S. W.; Hsu, K. L.; Lin, D. L.; Tzeng, C. C.

2007-04-01

The cathode erosion rate, arc root velocity and output power of a well-type cathode (WTC), non-transferred plasma torch operating in air are studied experimentally in this paper. An external solenoid to generate a magnetically driven arc and a circular swirler to produce a vortex flow structure are equipped in the studied torch system, which is designed to reduce the erosion rate at the cathode. A least square technique is applied to correlate the system parameters, i.e. current, axial magnetic field and mass flow rate, with the cathode erosion rate, arc root velocity and system power output. In the studied WTC torch system, the cathode erosion has a major thermal erosion component and a minor component due to the ion-bombardment effect. The cathode erosion increases with the increase of current due to the enhancement in both Joule heating and ion bombardment. The axial magnetic field can significantly reduce the cathode erosion by reducing the thermal loading of cathode materials at the arc root and improving the heat transfer to gas near the cathode. But, the rise in the mass flow rate leads to the deterioration of erosion, since the ion-bombardment effect prevails over the convective cooling at the cathode. The most dominant system parameter to influence the arc root velocity is the axial magnetic field, which is mainly contributed to the magnetic force driving the arc. The growth in current has a negative impact on increasing the arc root velocity, because the friction force acting at the spot due to a severe molten condition becomes the dominant component counteracting the magnetic force. The mass flow rate also suppresses the arc root velocity, as a result of which the arc root moves in the direction against that of the swirled working gas. All system parameters such as current, magnetic field and gas flow rate increase with the increase in the torch output power. The experimental evidences suggest that the axial magnetic field is the most important parameter

Use of 137Cs measurements to estimate changes in soil erosion rates associated with changes in soil management practices on cultivated land.

PubMed

Schuller, P; Walling, D E; Sepúlveda, A; Trumper, R E; Rouanet, J L; Pino, I; Castillo, A

2004-05-01

Intensification of agricultural production in south-central Chile since the 1970s has caused problems of increased soil erosion and associated soil degradation. These problems have prompted a shift from conventional tillage to no-till management practices. Faced with the need to establish the impact of this shift in soil management on rates of soil loss, the use of caesium-137 (137Cs) measurements has been explored. A novel procedure for using measurements of the 137Cs depth distribution to estimate rates of soil loss at a sampling point under the original conventional tillage and after the shift to no-till management has been developed. This procedure has been successfully applied to a study site at Buenos Aires farm near Carahue in the 9th region of Chile. The results obtained indicate that the shift from conventional tillage to no-till management has caused net rates of soil loss to decrease to about 40% of those existing under conventional tillage. This assessment of the impact of introducing no-till management at the study site must, however, be seen as provisional, since only a limited number of sampling points were used. A simplified procedure aimed at documenting the reduction in erosion rates at additional sampling points, based solely on measurements of the 137Cs inventory of bulk cores and the 137Cs activity in the upper part of the soil has been developed and successfully tested at the study site. Previous application of 137Cs measurements to estimate erosion rates has been limited to estimation of medium-term erosion rates during the period extending from the beginning of fallout receipt to the time of sampling. The procedures described in this paper, which permits estimation of the change in erosion rates associated with a shift in land management practices, must be seen as representing a novel application of 137Cs measurements in soil erosion investigations.

Monthly Rainfall Erosivity Assessment for Switzerland

NASA Astrophysics Data System (ADS)

Schmidt, Simon; Meusburger, Katrin; Alewell, Christine

2016-04-01

Water erosion is crucially controlled by rainfall erosivity, which is quantified out of the kinetic energy of raindrop impact and associated surface runoff. Rainfall erosivity is often expressed as the R-factor in soil erosion risk models like the Universal Soil Loss Equation (USLE) and its revised version (RUSLE). Just like precipitation, the rainfall erosivity of Switzerland has a characteristic seasonal dynamic throughout the year. This inter-annual variability is to be assessed by a monthly and seasonal modelling approach. We used a network of 86 precipitation gauging stations with a 10-minute temporal resolution to calculate long-term average monthly R-factors. Stepwise regression and Monte Carlo Cross Validation (MCCV) was used to select spatial covariates to explain the spatial pattern of R-factor for each month across Switzerland. The regionalized monthly R-factor is mapped by its individual regression equation and the ordinary kriging interpolation of its residuals (Regression-Kriging). As covariates, a variety of precipitation indicator data has been included like snow height, a combination of hourly gauging measurements and radar observations (CombiPrecip), mean monthly alpine precipitation (EURO4M-APGD) and monthly precipitation sums (Rhires). Topographic parameters were also significant explanatory variables for single months. The comparison of all 12 monthly rainfall erosivity maps showed seasonality with highest rainfall erosivity in summer (June, July, and August) and lowest rainfall erosivity in winter months. Besides the inter-annual temporal regime, a seasonal spatial variability was detectable. Spatial maps of monthly rainfall erosivity are presented for the first time for Switzerland. The assessment of the spatial and temporal dynamic behaviour of the R-factor is valuable for the identification of more susceptible seasons and regions as well as for the application of selective erosion control measures. A combination with monthly vegetation

Erosion characteristics and horizontal variability for small erosion depths in the Sacramento-San Joaquin River Delta, California, USA

NASA Astrophysics Data System (ADS)

Schoellhamer, David H.; Manning, Andrew J.; Work, Paul A.

2017-06-01

Erodibility of cohesive sediment in the Sacramento-San Joaquin River Delta (Delta) was investigated with an erosion microcosm. Erosion depths in the Delta and in the microcosm were estimated to be about one floc diameter over a range of shear stresses and times comparable to half of a typical tidal cycle. Using the conventional assumption of horizontally homogeneous bed sediment, data from 27 of 34 microcosm experiments indicate that the erosion rate coefficient increased as eroded mass increased, contrary to theory. We believe that small erosion depths, erosion rate coefficient deviation from theory, and visual observation of horizontally varying biota and texture at the sediment surface indicate that erosion cannot solely be a function of depth but must also vary horizontally. We test this hypothesis by developing a simple numerical model that includes horizontal heterogeneity, use it to develop an artificial time series of suspended-sediment concentration (SSC) in an erosion microcosm, then analyze that time series assuming horizontal homogeneity. A shear vane was used to estimate that the horizontal standard deviation of critical shear stress was about 30% of the mean value at a site in the Delta. The numerical model of the erosion microcosm included a normal distribution of initial critical shear stress, a linear increase in critical shear stress with eroded mass, an exponential decrease of erosion rate coefficient with eroded mass, and a stepped increase in applied shear stress. The maximum SSC for each step increased gradually, thus confounding identification of a single well-defined critical shear stress as encountered with the empirical data. Analysis of the artificial SSC time series with the assumption of a homogeneous bed reproduced the original profile of critical shear stress, but the erosion rate coefficient increased with eroded mass, similar to the empirical data. Thus, the numerical experiment confirms the small-depth erosion hypothesis. A linear

Erosion characteristics and horizontal variability for small erosion depths in the Sacramento-San Joaquin River Delta, California, USA

USGS Publications Warehouse

Schoellhamer, David H.; Manning, Andrew J.; Work, Paul A.

2017-01-01

Erodibility of cohesive sediment in the Sacramento-San Joaquin River Delta (Delta) was investigated with an erosion microcosm. Erosion depths in the Delta and in the microcosm were estimated to be about one floc diameter over a range of shear stresses and times comparable to half of a typical tidal cycle. Using the conventional assumption of horizontally homogeneous bed sediment, data from 27 of 34 microcosm experiments indicate that the erosion rate coefficient increased as eroded mass increased, contrary to theory. We believe that small erosion depths, erosion rate coefficient deviation from theory, and visual observation of horizontally varying biota and texture at the sediment surface indicate that erosion cannot solely be a function of depth but must also vary horizontally. We test this hypothesis by developing a simple numerical model that includes horizontal heterogeneity, use it to develop an artificial time series of suspended-sediment concentration (SSC) in an erosion microcosm, then analyze that time series assuming horizontal homogeneity. A shear vane was used to estimate that the horizontal standard deviation of critical shear stress was about 30% of the mean value at a site in the Delta. The numerical model of the erosion microcosm included a normal distribution of initial critical shear stress, a linear increase in critical shear stress with eroded mass, an exponential decrease of erosion rate coefficient with eroded mass, and a stepped increase in applied shear stress. The maximum SSC for each step increased gradually, thus confounding identification of a single well-defined critical shear stress as encountered with the empirical data. Analysis of the artificial SSC time series with the assumption of a homogeneous bed reproduced the original profile of critical shear stress, but the erosion rate coefficient increased with eroded mass, similar to the empirical data. Thus, the numerical experiment confirms the small-depth erosion hypothesis. A linear

Spatial and temporal variations of wind erosion climatic erosivity in the farming-pastoral zone of Northern China

NASA Astrophysics Data System (ADS)

Yue, Shuping; Yang, Ruixin; Yan, Yechao; Yang, Zhengwei; Wang, Dandan

2018-03-01

Wind erosion climatic erosivity is an important parameter to assess the possible effects of climatic conditions on wind erosion. In this paper, the wind erosion climatic factor (C-factor), which was used to quantify the wind erosion climatic erosivity, was calculated for the period 1960-2014 based on monthly meteorological data collected from 101 stations in the farming-pastoral zone of Northern China. The Mann-Kendall (M-K) test, trend analysis, and geostatistical analysis methods were used to explore the spatial and temporal characteristics of the wind erosion climatic erosivity in this region. The result suggests that the annual C-factor, with a maximum of 76.05 in 1969 and a minimum of 26.57 in 2007, has a significant decreasing trend over the past 55 years. Strong seasonality in the C-factor was found, with the highest value in spring, which accounts for a significant proportion of the annual C-factor (41.46%). However, the coefficient of variation of the seasonal C-factor reaches a maximum in winter and a minimum in spring. The mean annual C-factor varies substantially across the region. Areas with high values of the mean annual C-factor (C ≥ 100) are located in Ulanqab and Dingxi, while areas with low values (C ≤ 10) lie in Lanzhou, Linxia, Dingxi, Xining, and Chengde. Spatial analysis on the trend of the C-factor reveals that 81% of the stations show statistically significant decreases at a 90% confidence level. An examination of the concentration ratio of the C-factor shows that the wind erosion climatic erosivity is concentrated in spring, especially in April, which makes this period particularly important for implementing soil conservation measures.

Effect of stone coverage on soil erosion

NASA Astrophysics Data System (ADS)

Jomaa, S.; Barry, D. A.; Heng, B. P.; Brovelli, A.; Sander, G. C.; Parlange, J.

2010-12-01

Soil surface coverage has a significant impact on water infiltration, runoff and soil erosion yields. In particular, surface stones protect the soils from raindrop detachment, they retard the overland flow therefore decreasing its sediment transport capacity, and they prevent surface sealing. Several physical and environmental factors control to what extent stones on the soil surface modify the erosion rates and the related hydrological response. Among the most important factors are the moisture content of the topsoil, stone size, emplacement, coverage density and soil texture. Owing to the different inter-related processes, there is ambiguity concerning the quantitative effect of stones, and process-based understanding is limited. Experiments were performed (i) to quantify how stone features affect sediment yields, (ii) to understand the local effect of isolated surface stones, that is, the changes of the soil particle size distribution in the vicinity of a stone and (iii) to determine how stones attenuate the development of surface sealing and in turn how this affects the local infiltration rate. A series of experiments using the EPFL 6-m × 2-m erosion flume were conducted at different rainfall intensities (28 and 74 mm h-1) and stone coverage (20 and 40%). The total sediment concentration, the concentration of the individual size classes and the flow discharge were measured. In order to analyze the measurements, the Hairsine and Rose (HR) erosion model was adapted to account for the shielding effect of the stone cover. This was done by suitably adjusting the parameters based on the area not covered by stones. It was found that the modified HR model predictions agreed well with the measured sediment concentrations especially for the long time behavior. Changes in the bulk density of the topsoil due to raindrop-induced compaction with and without stone protection revealed that the stones protect the upper soil surface against the structural seals resulting in

Growth and erosion of mountain ranges at the northeastern margin of Tibet

NASA Astrophysics Data System (ADS)

Hetzel, Ralf; Palumbo, Luigi; Giese, Jörg; Guo, Jianming

2010-05-01

The hypothesis that mountain belts may reach a steady state, in which rock uplift is balanced by erosion, has been supported by numerous field studies and numerical models. The early evolution of mountain ranges, however, and especially the relation between fault growth and topographic response has received little attention. By using a space-for-time substitution we illustrate how active thrust faults and small, fault-bounded mountain ranges evolve into mature mountain chains that will ultimately be incorporated into the laterally growing Tibetan Plateau. At an early stage of development, when faults propagate laterally, slip rates are constant along strike [1-3]. As long as no significant topographic relief has developed, tectonic uplift is at least an order of magnitude faster than the rate of erosion [2,4]. During progressive relief growth and the establishment of drainage basins, erosion of the rising mountain ranges becomes more important, but the studied ranges are still in a pre-steady state and continue to grow both vertically and laterally [5]. During this stage the rate of erosion is linearly correlated to the mean hillslope gradient and the mean local relief, if differences in lithology or rock strength are negligible [6]. The rate of relief growth may be inferred from the difference between local erosion rates on ridge crests and catchment-wide denudation rates [7] - the latter may be taken as a surrogate for the rate of river incision. As hillslopes approach a threshold value, landsliding becomes the dominant process of mass transport and erosion rates increase non-linearly with slope. Once a steady state has been reached, the erosion rate is equal to the rate of rock uplift. A key problem is how the rate of rock uplift can be quantified in such regions, because the stochastic distribution of landslides causes the denudation rates inferred from 10Be in river sediment to be highly variable [8]. References [1] Hetzel et al. (2004). Implications of the

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

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.

Aeolian Induced Erosion and Particle Entrainment

NASA Technical Reports Server (NTRS)

Saint, Brandon

2007-01-01

The Granular Physics Department at The Kennedy Space Center is addressing the problem of erosion on the lunar surface. The early stages of research required an instrument that would produce erosion at a specific rate with a specific sample variation. This paper focuses on the development and experimental procedures to measure and record erosion rates. This was done with the construction of an open air wind tunnel, and examining the relationship between airflow and particle motion.

Sediment budget for Murder Creek, Georgia, USA, from Pu239+240 - determined soil erosion rates

NASA Astrophysics Data System (ADS)

Stubblefield, A. P.; Matissoff, G.; Ketterer, M. E.; Whiting, P. J.

2005-12-01

Soil inventories of the radionuclides Cs137 and Pb210 have been used in a variety of environments as indicators for erosion and depositional processes. Development of sediment budgets for entire watersheds from radionuclide data has been somewhat constrained because limited sample numbers may not adequately characterize the wide range of geomorphic conditions and land uses found in heterogeneous environments. The measurement of Pu239+240 shows great potential for developing quantitative watershed sediment budgets. With inductively-coupled plasma mass spectrometry, hundreds of samples may be processed in dramatically shorter times than the gamma spectrometry method used for Cs137 or alpha spectrometry method used for Pb210. We collected surface soil samples from Murder Creek in the Piedmont region of Georgia, USA, to compare Pu239+240 inventories with Cs137 and Pb210 inventories for a range of land uses in a predominantly forested watershed. Excellent correlations were found for radionuclide inventories (r2 =0.88, n = 38) and high resolution (4 mm) depth profiles. The second objective was to generate a sediment budget using the full Pu239+240 dataset (n = 309). Average Pu239+240 inventories were 70.0 Bq/m2 for hardwood forest, 60.0 Bq/m2 for pine plantation, 65.1 Bq/m2 for pine forest, 66.7 Bq/m2 for row crop agriculture and 67.9 Bq/m2 for pasture. The sediment budget will be constructed by converting inventories into site-specific erosion rates. Erosion rates will be scaled up to the watershed scale using GIS coverages of land use, soil, slope, and slope position. Results will be compared with Murder Creek sediment budgets in the scientific literature generated from RUSLE erosion modeling, USGS monitoring networks and reservoir sedimentation.

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

Nonmonotonic and spatial-temporal dynamic slope effects on soil erosion during rainfall-runoff processes

NASA Astrophysics Data System (ADS)

Wu, Songbai; Yu, Minghui; Chen, Li

2017-02-01

The slope effect on flow erosivity and soil erosion still remains a controversial issue. This theoretical framework explained and quantified the direct slope effect by coupling the modified Green-Ampt equation accounting for slope effect on infiltration, 1-D kinematic wave overland flow routing model, and WEPP soil erosion model. The flow velocity, runoff rate, shear stress, interrill, and rill erosion were calculated on 0°-60° isotropic slopes with equal horizontal projective length. The results show that, for short-duration rainfall events, the flow erosivity and erosion amounts exhibit a bell-shaped trend which first increase with slope gradient, and then decrease after a critical slope angle. The critical slope angles increase significantly or even vanish with increasing rainfall duration but are nearly independent of the slope projective length. The soil critical shear stress, rainfall intensity, and temporal patterns have great influences on the slope effect trend, while the other soil erosion parameters, soil type, hydraulic conductivity, and antecedent soil moisture have minor impacts. Neglecting the slope effect on infiltration would generate smaller erosion and reduce critical slope angles. The relative slope effect on soil erosion in physically based model WEPP was compared to those in the empirical models USLE and RUSLE. The trends of relative slope effect were found quite different, but the difference may diminish with increasing rainfall duration. Finally, relatively smaller critical slope angles could be obtained with the equal slope length and the range of variation provides a possible explanation for the different critical slope angles reported in previous studies.

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

The relative importance of different grass components in controlling runoff and erosion on a hillslope under simulated rainfall

NASA Astrophysics Data System (ADS)

Li, Changjia; Pan, Chengzhong

2018-03-01

The effects of vegetation cover on overland flow and erosion processes on hillslopes vary with vegetation type and spatial distribution and the different vegetation components, including the above- and below-ground biomass. However, few attempts have been made to quantify how these factors affect erosion processes. Field experimental plots (5 m × 2 m) with a slope of approximately 25° were constructed and simulated rainfall (60 mm hr-1) (Rainfall) and simulated rainfall combined with upslope overland flow (20 L min-1) (Rainfall + Flow) were applied. Three grass species were planted, specifically Astragalus adsurgens (A. adsurgens), Medicago sativa (M. sativa) and Cosmos bipinnatus (C. bipinnatus). To isolate and quantify the relative contributions of the above-ground grass parts (stems, litter cover and leaves) and the roots to reducing surface runoff and erosion, each of the three grass species was subjected to three treatments: intact grass control (IG), no litter or leaves (only the grass stems and roots were reserved) (NLL), and only roots remaining (OR). The results showed that planting grass significantly reduced overland flow rate and velocity and sediment yield, and the mean reductions were 21.8%, 29.1% and 67.1%, respectively. M. sativa performed the best in controlling water and soil losses due to its thick canopy and dense, fine roots. Grasses reduced soil erosion mainly during the early stage of overland flow generation. The above-ground grass parts primarily contributed to reducing overland flow rate and velocity, with mean relative contributions of 64% and 86%, respectively. The roots played a predominant role in reducing soil erosion, with mean contribution of 84%. Due to the impact of upslope inflow, overland flow rate and velocity and sediment yield increased under the Rainfall + Flow conditions. The results suggest that grass species on downslope parts of semi-arid hillslopes performed better in reducing water and soil losses. This study is

Effect of mechanical properties on erosion resistance of ductile materials

NASA Astrophysics Data System (ADS)

Levin, Boris Feliksovih

Solid particle erosion (SPE) resistance of ductile Fe, Ni, and Co-based alloys as well as commercially pure Ni and Cu was studied. A model for SPE behavior of ductile materials is presented. The model incorporates the mechanical properties of the materials at the deformation conditions associated with SPE process, as well as the evolution of these properties during the erosion induced deformation. An erosion parameter was formulated based on consideration of the energy loss during erosion, and incorporates the material's hardness and toughness at high strain rates. The erosion model predicts that materials combining high hardness and toughness can exhibit good erosion resistance. To measure mechanical properties of materials, high strain rate compression tests using Hopkinson bar technique were conducted at strain rates similar to those during erosion. From these tests, failure strength and strain during erosion were estimated and used to calculate toughness of the materials. The proposed erosion parameter shows good correlation with experimentally measured erosion rates for all tested materials. To analyze subsurface deformation during erosion, microhardness and nanoindentation tests were performed on the cross-sections of the eroded materials and the size of the plastically deformed zone and the increase in materials hardness due to erosion were determined. A nanoindentation method was developed to estimate the restitution coefficient within plastically deformed regions of the eroded samples which provides a measure of the rebounding ability of a material during particle impact. An increase in hardness near the eroded surface led to an increase in restitution coefficient. Also, the stress rates imposed below the eroded surface were comparable to those measured during high strain-rate compression tests (10sp3-10sp4 ssp{-1}). A new parameter, "area under the microhardness curve" was developed that represents the ability of a material to absorb impact energy. By

Extensive rill erosion and gullying on abandoned pit mining sites in Lusatia, Germany

NASA Astrophysics Data System (ADS)

Kunth, Franziska; Kaiser, Andreas; Vláčilová, Markéta; Schindewolf, Marcus; Schmidt, Jürgen

2015-04-01

As the major economic driver in the province of Lusatia, Eastern Germany, the large open-cast lignite mining sites characterize the landscape and leave vast areas of irreversible changed post-mining landscapes behind. Cost-intensive renaturation projects have been implemented in order to restructure former mine sites into stabile self-sustaining ecosystems and local recreation areas. With considerable expenditure the pits are stabilized, flooded and surrounding areas are restructured. Nevertheless, heavy soil erosion, extensive gullying and slope instability are challenges for the restructuring and renaturation of the abandoned open-cast mining sites. The majority of the sites remain inaccessible to the public due to instable conditions resulting in uncontrolled slides and large gullies. In this study a combined approach of UAV-based aerial imagery, 3D multi-vision surface reconstruction and physically-based soil erosion modelling is carried out in order to document, quantify and better understand the causes of erosion processes on mining sites. Rainfall simulations have been carried out in lausatian post mining areas to reproduce soil detachment processes and observe the responsible mechanisms for the considerable erosion rates. Water repellency and soil sealing by biological crusts were hindering infiltration and consequently increasing runoff rates despite the mainly sandy soil texture. On non-vegetated experimental plots runoff coefficients up to 87 % were measured. In a modelling routine for a major gully catchment regarding a 50 years rainfall event, simulation results reveal runoff coefficients of up to 84% and erosion rates of 118 Mg*ha^-1. At the sediment pass over point 450Mg of sediments enter the surface water bodies. A system response of this order of magnitude were unexpected by the authorities. By applying 3D multi-vision surface reconstruction a model validation is now possible and further may illustrate the great importance of soil conservation

Use of Sediment Budgets for Watershed Erosion Control Planning: A Case Study From Northern California

NASA Astrophysics Data System (ADS)

O'Connor, M.; McDavitt, W.

2002-05-01

Erosion, sedimentation and peak flow increases caused by forest management for commercial timber production may negatively affect aquatic habitat of endangered anadromous fish such as coho salmon ({\\ it O. kisutch}). This paper summarizes a portion of a Watershed Analysis study performed for Pacific Lumber Company, Scotia, CA, focusing on erosion and sedimentation processes and rates and downstream sediment routing and water quality in the Freshwater Creek watershed in northwest California. Hillslope, road and bank erosion, channel sedimentation and sediment rates were quantified using field surveys, aerial photo interpretation, and empirical modeling approaches for different elements of the study. Sediment transport rates for bedload were modeled, and sediment transport rates for suspended sediment were estimated based on size distribution of sediment inputs in relation to sizes transported in suspension. The resulting sediment budget was validated through comparison using recent short-term, high-quality estimates of suspended sediment yield collected by a community watershed group at a downstream monitoring site with technical assistance from the US Forest Service. Another check on the sediment budget was provided by bedload yield data from an adjacent watershed, Jacoby Creek. The sediment budget techniques and bedload routing models used for this study provide sediment yield estimates that are in good agreement with available data. These results suggest that sediment budget techniques that require moderate levels of fieldwork can be used to provide relatively accurate technical assessments for use in the TMDL process. The sediment budget also identifies the most significant sediment sources and suggests a framework within which effective erosion control strategies can be developed.

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

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

Rill erosion in natural and disturbed forests: 1. Measurements

Treesearch

P. R. Robichaud; J. W. Wagenbrenner; R. E. Brown

2010-01-01

Rill erosion can be a large portion of the total erosion in disturbed forests, but measurements of the runoff and erosion at the rill scale are uncommon. Simulated rill erosion experiments were conducted in two forested areas in the northwestern United States on slopes ranging from 18 to 79%. We compared runoff rates, runoff velocities, and sediment flux rates from...

Decreasing soil erosion rates with evolving land-use techniques in a central European catchment

NASA Astrophysics Data System (ADS)

Larsen, Annegret; Heckmann, Tobias; Hans-Rudolf, Bork; Alexander, Fuelling

2015-04-01

Agricultural societies around the world have caused accelerated soil erosion. Soil erosion and a decrease in soil fertility may also have caused the abandonment of entire landscapes and the collapse of civilizations. In central Europe, Medieval land-use is thought to have lead to the largest loss of top soil in history, which in turn lead to a malnutrition of the population and abandonment of agricultural land. However, this might be only part of the picture, as people are also able to adapt to changing environmental conditions, including the type of land-use they adopt. Within a catchment in the central European mountain belt, we were able to distinguish the evolution between three main types of land-use techniques between ~ 900 AD and 1950 AD: horticulture, agriculture and shifting cultivation. We were able to relate these techniques with different soil erosion rates, which differ by an order of magnitude, ranging from 0.83 ± 0.09 mm/yr to 1.62 ± 0.17 mm/yr. Using high-resolution surface data and chrono-stratigraphical methods in combination with soil charcoal analysis, we were able to reconstruct past land-use techniques on a local scale. This illustrates that less erosive and more sustainable techniques were developed through time, and hypothesize that people were able to adapt to the less favorable environmental conditions by changing the cultivation techniques. Although cultural adaptation to changing environmental conditions has been extensively discussed, this study is able to quantitatively demonstrate improved soil management with evolving land-use in central Europe.

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.

Boreal forest soil erosion and soil-atmosphere carbon exchange

NASA Astrophysics Data System (ADS)

Billings, S. A.; Harden, J. W.; O'Donnell, J.; Sierra, C. A.

2013-12-01

Erosion may become an increasingly important agent of change in boreal systems with climate warming, due to enhanced ice wedge degradation and increases in the frequency and intensity of stand-replacing fires. Ice wedge degradation can induce ground surface subsidence and lateral movement of mineral soil downslope, and fire can result in the loss of O horizons and live roots, with associated increases in wind- and water-promoted erosion until vegetation re-establishment. It is well-established that soil erosion can induce significant atmospheric carbon (C) source and sink terms, with the strength of these terms dependent on the fate of eroded soil organic carbon (SOC) and the extent to which SOC oxidation and production characteristics change with erosion. In spite of the large SOC stocks in the boreal system and the high probability that boreal soil profiles will experience enhanced erosion in the coming decades, no one has estimated the influence of boreal erosion on the atmospheric C budget, a phenomenon that can serve as a positive or negative feedback to climate. We employed an interactive erosion model that permits the user to define 1) profile characteristics, 2) the erosion rate, and 3) the extent to which each soil layer at an eroding site retains its pre-erosion SOC oxidation and production rates (nox and nprod=0, respectively) vs. adopts the oxidation and production rates of previous, non-eroded soil layers (nox and nprod=1, respectively). We parameterized the model using soil profile characteristics observed at a recently burned site in interior Alaska (Hess Creek), defining SOC content and turnover times. We computed the degree to which post-burn erosion of mineral soil generates an atmospheric C sink or source while varying erosion rates and assigning multiple values of nox and nprod between 0 and 1, providing insight into the influence of erosion rate, SOC oxidation, and SOC production on C dynamics in this and similar profiles. Varying nox and nprod

Dimensionless erosion laws for cohesive sediment

USGS Publications Warehouse

Walder, Joseph S.

2016-01-01

A method of achieving a dimensionless collapse of erosion-rate data for cohesive sediments is proposed and shown to work well for data collected in flume-erosion tests on mixtures of sand and mud (silt plus clay sized particles) for a wide range of mud fraction. The data collapse corresponds to a dimensional erosion law of the form E∼(τ−τc)m">E∼(τ−τc)mE∼(τ−τc)m, where E">EE is erosion rate, τ">ττ is shear stress, τc">τcτc is the threshold shear stress for erosion to occur, and m≈7/4">m≈7/4m≈7/4. This result contrasts with the commonly assumed linear erosion law E=kd(τ−τc)">E=kd(τ−τc)E=kd(τ−τc), where kd">kdkd is a measure of how easily sediment is eroded. The data collapse prompts a re-examination of the way that results of the hole-erosion test (HET) and jet-erosion test (JET) are customarily analyzed, and also calls into question the meaningfulness not only of proposed empirical relationships between kd">kdkd and τc">τcτc, but also of the erodibility parameter kd">kdkd itself. Fuller comparison of flume-erosion data with hole-erosion and jet-erosion data will require revised analyses of the HET and JET that drop the assumption m=1">m=1m=1 and, in the case of the JET, certain simplifying assumptions about the mechanics of jet scour.

Whole watershed quantification of net carbon fluxes by erosion and deposition within the Christina River Basin Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Aufdenkampe, A. K.; Karwan, D. L.; Aalto, R. E.; Marquard, J.; Yoo, K.; Wenell, B.; Chen, C.

2012-12-01

We have proposed that the rate at which fresh, carbon-free minerals are delivered to and mix with fresh organic matter determines the rate of carbon preservation at a watershed scale (Aufdenkampe et al. 2011). Although many studies have examined the role of erosion in carbon balances, none consider that fresh carbon and fresh minerals interact. We believe that this mechanism may be a dominant sequestration process in watersheds with strong anthropogenic impacts. Our hypothesis - that the rate of mixing fresh carbon with fresh, carbon-free minerals is a primary control on watershed-scale carbon sequestration - is central to our Christina River Basin Critical Zone Observatory project (CRB-CZO, http://www.udel.edu/czo/). The Christina River Basin spans 1440 km2 from piedmont to Atlantic coastal plain physiographic provinces in the states of Pennsylvania and Delaware, and experienced intensive deforestation and land use beginning in the colonial period of the USA. Here we present a synthesis of multi-disciplinary data from the CRB-CZO on materials as they are transported from sapprolite to topsoils to colluvium to suspended solids to floodplains, wetlands and eventually to the Delaware Bay estuary. At the heart of our analysis is a spatially-integrated, flux-weighted comparison of the organic carbon to mineral surface area ratio (OC/SA) of erosion source materials versus transported and deposited materials. Because source end-members - such as forest topsoils, farmed topsoils, gullied subsoils and stream banks - represent a wide distribution of initial, pre-erosion OC/SA, we quantify source contributions using geochemical sediment fingerprinting approaches (Walling 2005). Analytes used for sediment fingerprinting include: total mineral elemental composition (including rare earth elements), fallout radioisotope activity for common erosion tracers (beryllium-7, beryllium-10, lead-210, cesium-137), particle size distribution and mineral specific surface area, in addition

The use of 137Cs to establish longer-term soil erosion rates on footpaths in the UK.

PubMed

Rodway-Dyer, S J; Walling, D E

2010-10-01

There is increasing awareness of the damage caused to valuable and often unique sensitive habitats by people pressure as degradation causes a loss of plant species, disturbance to wildlife, on-site and off-site impacts of soil movement and loss, and visual destruction of pristine environments. This research developed a new perspective on the problem of recreational induced environmental degradation by assessing the physical aspects of soil erosion using the fallout radionuclide caesium-137 ((137)Cs). Temporal sampling problems have not successfully been overcome by traditional research methods monitoring footpath erosion and, to date, the (137)Cs technique has not been used to estimate longer-term soil erosion in regard to sensitive recreational habitats. The research was based on-sites within Dartmoor National Park (DNP) and the South West Coast Path (SWCP) in south-west England. (137)Cs inventories were reduced on the paths relative to the reference inventory (control), indicating loss of soil from the path areas. The Profile Distribution Model estimated longer-term erosion rates (ca. 40 years) based on the (137)Cs data and showed that the combined mean soil loss for all the sites on 'paths' was 1.41 kg m(-2) yr(-1) whereas the combined 'off path' soil loss was 0.79 kg m(-2) yr(-1), where natural (non-recreational) soil redistribution processes occur. Recreational pressure was shown to increase erosion in the long-term, as greater soil erosion occurred on the paths, especially where there was higher visitor pressure. Copyright (c) 2010 Elsevier Ltd. All rights reserved.

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

Comparing global-scale topographic and climatic metrics to long-term erosion rates using ArcSwath, an efficient new ArcGIS tool for swath profile analysis

NASA Astrophysics Data System (ADS)

Blomqvist, Niclas; Whipp, David

2016-04-01

The topography of the Earth's surface is the result of the interaction of tectonics, erosion and climate. Thus, topography should contain a record of these processes that can be extracted by topographic analysis. The question considered in this study is whether the spatial variations in erosion that have sculpted the modern topography are representative of the long-term erosion rates in mountainous regions. We compare long-term erosion rates derived from low-temperature thermochronometry to erosional proxies calculated from topographic and climatic data analysis. The study has been performed on a global scale including six orogens: The Himalaya, Andes, Taiwan, Olympic Mountains, Southern Alps in New Zealand and European Alps. The data was analyzed using a new swath profile analysis tool for ArcGIS called ArcSwath (https://github.com/HUGG/ArcSwath) to determine the correlations between the long-term erosion rates and modern elevations, slope angles, relief in 2.5-km- and 5-km-diameter circles, erosion potential, normalized channel steepness index ksn, and annual rainfall. ArcSwath uses a Python script that has been incorporated into an ArcMap 10.2 add-in tool, extracting swath profiles in about ten seconds compared to earlier workflows that could take more than an hour. In ArcMap, UTM-projected point or raster files can be used for creating swath profiles. Point data are projected onto the swath and the statistical parameters (minimum, mean and maximum of the values across the swath) are calculated for the raster data. Both can be immediately plotted using the Python matplotlib library, or plotted externally using the csv-file that is produced by ArcSwath. When raster and point data are plotted together, it is easier to make comparisons and see correlations between the selected data. An unambiguous correlation between the topographic or climatic metrics and long-term erosion rates was not found. Fitting of linear regression lines to the topographic/ climatic metric

Using cosmogenic nuclides to contrast rates of erosion and sediment yield in a semi-arid, arroyo-dominated landscape, Rio Puerco Basin, New Mexico

USGS Publications Warehouse

Bierman, P.R.; Reuter, J.M.; Pavich, M.; Gellis, A.C.; Caffee, M.W.; Larsen, J.

2005-01-01

Analysis of in-situ-produced 10Be and 26Al in 52 fluvial sediment samples shows that millennial-scale rates of erosion vary widely (7 to 366 m Ma-1) through the lithologically and topographically complex Rio Puerco Basin of northern New Mexico. Using isotopic analysis of both headwater and downstream samples, we determined that the semi-arid, Rio Puerco Basin is eroding, on average, about 100 m Ma-1. This rapid rate of erosion is consistent with estimates made using other techniques and is likely to result from a combination of easily eroded lithologies, sparse vegetation, and monsoon-dominated rainfall. Data from 331 stream water samples collected by the US Geological Survey between 1960 and 1995 are consistent with basin-wide, average chemical denudation rates of only about 1??4 m Ma-1; thus, the erosion rates we calculate may be considered rates of sediment generation because physical weathering accounts for almost 99 per cent of mass loss. The isotopic data reveal that sediment is generally well mixed downstream with the area-weighted average sediment generation rate for 16 headwater samples (234 ton km-2 a-1 for basin area 170 to 1169 km2) matching well that estimated from a single sample collected far downstream (238 ton km-2 a-1, basin area = 14 225 km2). A series of 15 samples, collected from an arroyo wall and representing deposition through the late Holocene, indicates that 10Be concentration in sediment delivered by the fluvial system has not changed appreciably over the last 1200 years despite at least two cycles of arroyo cutting and filling. Other samples (n = 21) were collected along the drainage network. Rio Puerco erosion rates scale directly with a variety of metrics describing vegetation, precipitation, and rock erodibility. Using the headwater basins for calibration, the erosion rates for both the downstream samples and also the data set as a whole, are best modelled by considering a combination of relief and vegetation metrics, both of which co

Effects of roads and well pads on erosion in the Largo Canyon watershed, New Mexico, 2001-02

USGS Publications Warehouse

Matherne, Anne Marie

2006-01-01

Largo Canyon, located in the San Juan Basin of northwestern New Mexico, is one of the longest dry washes in the world. Oil and gas production in the San Juan Basin, which began in the 1940's, required the development of an extensive network of dirt roads to service the oil and gas wells in the Navajo Reservoir area. Presently, there are about eight wells per square mile, and the density of oil and gas wells is expected to increase. Potential environmental effects on landscape stability that may result from the additional roads and well pads have not been documented. In 2001, the U.S. Geological Survey began a study in cooperation with the Bureau of Land Management to evaluate the effects of roads and well pads associated with oil and gas operations on the erosion potential of Bureau of Land Management lands in the Largo Canyon watershed. The effects of roads and well pads on erosion were quantified by installing sediment dams (dams) and by surveying transects across roads and well pads. Data from 26 dams were used in the analysis. Dams were installed at 43 sites: 21 on hillsides upslope from roads or pads to measure erosion from hillslopes, 11 at the downslope edges of roads to measure erosion from roads, and 11 at the downslope edges of well pads to measure erosion from well pads. Pairs of survey transects were established at nine well pads and two road locations. Sediment-accumulation data for 26 dams, recorded at 17 measurement intervals, indicate that average erosion rates at the dams significantly correlate to size of the contributing area. The average erosion rate normalized by drainage area was 0.001 foot per year below roads, 0.003 foot per year on hillslopes, and 0.011 foot per year below well pads. Results of a two-sample t-test indicate that there was no significant difference in average erosion rates for dams located on hillslopes and below roads, whereas average erosion rates were significantly greater for dams below well pads than for dams on

Mars sedimentary rock erosion rates constrained using crater counts, with applications to organic-matter preservation and to the global dust cycle

NASA Astrophysics Data System (ADS)

Kite, Edwin S.; Mayer, David P.

2017-04-01

Small-crater counts on Mars light-toned sedimentary rock are often inconsistent with any isochron; these data are usually plotted then ignored. We show (using an 18-HiRISE-image, > 104-crater dataset) that these non-isochron crater counts are often well-fit by a model where crater production is balanced by crater obliteration via steady exhumation. For these regions, we fit erosion rates. We infer that Mars light-toned sedimentary rocks typically erode at ∼102 nm/yr, when averaged over 10 km2 scales and 107-108 yr timescales. Crater-based erosion-rate determination is consistent with independent techniques, but can be applied to nearly all light-toned sedimentary rocks on Mars. Erosion is swift enough that radiolysis cannot destroy complex organic matter at some locations (e.g. paleolake deposits at SW Melas), but radiolysis is a severe problem at other locations (e.g. Oxia Planum). The data suggest that the relief of the Valles Marineris mounds is currently being reduced by wind erosion, and that dust production on Mars < 3 Gya greatly exceeds the modern reservoir of mobile dust.

Late Miocene to Early Pleistocene Paleo-Erosion Rates and Provenance Change in the NE Argentinian Andes: Apparent Coupling of Sediment Fluxes with 400-kyr Eccentricity Cycles

NASA Astrophysics Data System (ADS)

Burch Fisher, G.; Amidon, William H.; Burbank, Douglas W.; Luna, Lisa V.

2016-04-01

Proposed linkages among climate, erosion, and tectonics provide an appealing framework for interpretation of the interplay among tectonic forcing, topographic form, climatic inputs, and rates of erosion. More rapid deformation is hypothesized to create higher and steeper topography that focuses precipitation, drives faster erosion, and enhances slip rates. But, a determination of cause and effect or synchrony in any proposed tectonic-climate-erosion coupling is commonly difficult to extract. Typically constraints on age and provenance are too loose, or records are too short, irregular, or sparse to permit nuanced interpretations. In fact, clear records in active orogens that reveal a persistent climatic imprint on erosion rates (such as ones scaled by Milankovich-type cyclicity) are rare, especially for pre-Quaternary intervals. Here, along the Rio Iruya on the eastern flank of the NE Argentinian Andes, we exploit a unique field setting in which a 100-m-deep canyon has been cut during the past century through a 6-km-thick tilted sequence of upper Cenozoic synorogenic strata. Sample ages in the Iruya gorge are provided by a high-quality magnetostratigraphy (~100-kyr resolution) that is calibrated with U-Pb zircon ages of interbedded tephra. Detrital zircon ages and quartz trace elements provide a provenance record for the sampled section. Here, we report 49 new detrital 10Be cosmogenic paleo-erosion rates spanning from the Late Miocene to Early Pleistocene (~5.8 to 1.8 Ma). Paired with each 10Be sample that is younger than ~3.3 Ma, 23 26Al samples provide a second proxy for paleo-erosion rates. 20th-century canyon cutting obviates the typical uncertainties associated with unconstrained Late Quaternary cosmogenic production due to exhumation prior to sampling. Three different erosion-rate regimes are apparent: from 1.8 to 2.3 Ma, rates are high with few oscillations; from 2.3 to 4.0 Ma, rates oscillate by a factor of 5 on a ~400-kyr timescale; and from 5.8 to 4.0 Ma

Erosion-corrosion and cavitation-erosion measurements on copper alloys utilizing thin layer activation technique

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

Tsai, C.H.; Hsu, K.Y.; Kai, J.J.

1992-12-31

The surface layers of copper alloy specimens were made radioactive by bombarding with 5 MeV protons from a van de Graaff accelerator which converted Cu-65 into Zn-65 through (p,n) reaction. The amount of surface material loss could then be monitored by measuring the total remaining {gamma}-ray activity generated from Zn-65 decay. This technique, termed thin layer activation (TLA), has the advantage of in situ monitoring the rate of surface removal due to corrosion, erosion-corrosion, wearing, etc. In this work, the erosion-corrosion tests on aluminum brass and 90Cu-10Ni were conducted in circulating sea water and the erosion-corrosion rates measured using TLAmore » and conventional methods such as linear polarization resistance (LPR) method and weight loss coupons were compared. A vibrational cavitation-erosion test was also performed on aluminum bronze, in which the measurements by TLA were compared with those of weight loss measurements.« less

Ability of One-Dimensional Hairsine-Rose Erosion Model to Predict Sediment Transport over a Soil with Significant Surface Stones

NASA Astrophysics Data System (ADS)

Jomaa, S.; Barry, D. A.; Sander, G. C.; Parlange, J.-Y.; Heng, B. C. P.; Tromp-van Meerveld, H. J.

2010-05-01

Surface stones affect erosion rates by reducing raindrop-driven detachment and protecting the original soil against overland flow induced-hydraulic stress. Numerous studies have shown that the effect of surface stones on erosion depends on both the stone characteristics (e.g., size, distribution) and the soil properties. The aim of this study was (i) to quantify how the stone characteristics can affect the total sediment concentration and the concentrations of the individual size classes, (ii) to test if stones affect preferentially a particular size class within the eroded sediment and (iii) to determine whether the 1D Hairsine-Rose (H-R) erosion model can represent the experimental data. A series of laboratory experiments were conducted using the 2 m × 6 m EPFL erosion flume for a high rainfall intensity (60 mm/h) event on a gentle slope (2.2%). The flume was divided into two identical 1-m wide flumes. This separation was done to allow simultaneous replicate experiments. Experiments were conducted with different configurations and scenarios (stone coverage, size and emplacement). Three coverage proportions (20%, 40%, and 70%), two stone diameters (3-4 and 6-7 cm) and two emplacement types (topsoil and partially embedded) were tested. For each experiment, the total sediment concentration, the concentration for the individual size classes, and the flume discharge were measured. Infiltration rates were measured at different depths and locations. A high resolution laser scanner provided details of the surface change due to erosion during the experiments. This technique allowed us to quantify the spatial distribution of eroded soil and to understand better if sediment transport is 1D or rather 2D over the flumes. The one-dimensional Hairsine-Rose (H-R) erosion model was used to fit the integrated data and to provide estimates of the parameters. The ability of the 1D H-R model to predict the measured sediment concentrations in the presence of stones in the soil matrix

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.

Techniques to Evaluate Dental Erosion: A Systematic Review of Literature.

PubMed

Joshi, Mahasweta; Joshi, Nikhil; Kathariya, Rahul; Angadi, Prabhakar; Raikar, Sonal

2016-10-01

This article reviews different techniques for evaluating dental erosion, weighs the advantages and disadvantages of these techniques, and presents the latest trends in the study of dental erosion. In May 2014, an initial search was carried out in the PubMed/MEDLINE database of indexed journals from 1975 to 2013 using the following keywords: dental erosion; dental erosion In-vitro; and dental erosion in-vivo. Bibliographic citations from the papers found were then used to find other useful sources. The authors categorize the techniques into three classes: in-vitro, in-vivo and in-vitro/in-vivo. The article discusses the instrumentation required to use each of these techniques, as well as their rationale, merits and applications. The emergence of in-vitro/in-vivo techniques offers the potential to accurately quantify tooth wear in clinical situations. Cross-sectional as well as longitudinal studies show that these techniques will improve diagnosis, treatment planning and management of dental erosion.

Techniques to Evaluate Dental Erosion: A Systematic Review of Literature

PubMed Central

Joshi, Mahasweta; Joshi, Nikhil; Angadi, Prabhakar; Raikar, Sonal

2016-01-01

This article reviews different techniques for evaluating dental erosion, weighs the advantages and disadvantages of these techniques, and presents the latest trends in the study of dental erosion. In May 2014, an initial search was carried out in the PubMed/MEDLINE database of indexed journals from 1975 to 2013 using the following keywords: dental erosion; dental erosion In-vitro; and dental erosion in-vivo. Bibliographic citations from the papers found were then used to find other useful sources. The authors categorize the techniques into three classes: in-vitro, in-vivo and in-vitro/in-vivo. The article discusses the instrumentation required to use each of these techniques, as well as their rationale, merits and applications. The emergence of in-vitro/in-vivo techniques offers the potential to accurately quantify tooth wear in clinical situations. Cross-sectional as well as longitudinal studies show that these techniques will improve diagnosis, treatment planning and management of dental erosion. PMID:27891489

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

Erosion rates of a small coastal island revealed by repeated measurements using TLS and UAS-SfM photogrammetry

NASA Astrophysics Data System (ADS)

Hayakawa, Y. S.; Obanawa, H.

2016-12-01

Due to the weak bedrock and constant wave erosion, sea cliffs along the outer Boso Peninsula, central Japan, have been eroded at ca. 1 m per year for centuries. Modern coastal protection work had significantly reduced the erosion rate, while this became a cause of limited supply of sands along beaches in this area. Among the almost complete protection, a small coastal island, so-called Suzume-Jima Island (70 km southeast of Tokyo), has not been protected, in which we can still observe processes of coastal cliff erosion at the original rate. We have performed multi-temporal (3 times a year), high-resolution (centimeters) topographic measurements of the small island for 3 years, using terrestrial laser scanning (TLS) and structure-from-motion multi-view stereo (SfM-MVS) photogrammetry with an unmanned aerial system (UAS). Landside of the island can be measured by both TLS and UAS, but the seaside could only be captured by UAS, therefore these data are combined to analyze the entire island morphology with a reasonable accuracy. Frequent, spatially variable wave erosion and rockfalls were observed during the measurement period. The dominant wave direction and geologic structure (joint location and orientation) may account for these differences. A severe notch development in the cliff suggests a possible formation of a sea cave through the island in the near future. The measured, short-term results were also compared with the longer-term development of the island shape, obtained by historical aerial photographs for 50 years.

Quantifying recent erosion and sediment delivery using probability sampling: A case study

Treesearch

Jack Lewis

2002-01-01

Abstract - Estimates of erosion and sediment delivery have often relied on measurements from locations that were selected to be representative of particular terrain types. Such judgement samples are likely to overestimate or underestimate the mean of the quantity of interest. Probability sampling can eliminate the bias due to sample selection, and it permits the...

Predicting the impact of logging activities on soil erosion and water quality in steep, forested tropical islands

NASA Astrophysics Data System (ADS)

Wenger, Amelia S.; Atkinson, Scott; Santini, Talitha; Falinski, Kim; Hutley, Nicholas; Albert, Simon; Horning, Ned; Watson, James E. M.; Mumby, Peter J.; Jupiter, Stacy D.

2018-04-01

Increasing development in tropical regions provides new economic opportunities that can improve livelihoods, but it threatens the functional integrity and ecosystem services provided by terrestrial and aquatic ecosystems when conducted unsustainably. Given the small size of many islands, communities may have limited opportunities to replace loss and damage to the natural resources upon which they depend for ecosystem service provisioning, thus heightening the need for proactive, integrated management. This study quantifies the effectiveness of management strategies, stipulated in logging codes-of-practice, at minimizing soil erosion and sediment runoff as clearing extent increases, using Kolombangara Island, Solomon Islands as a case study. Further, we examine the ability of erosion reduction strategies to maintain sustainable soil erosion rates and reduce potential downstream impacts to drinking water and environmental water quality. We found that increasing land clearing—even with best management strategies in place—led to unsustainable levels of soil erosion and significant impacts to downstream water quality, compromising the integrity of the land for future agricultural uses, consistent access to clean drinking water, and important downstream ecosystems. Our results demonstrate that in order to facilitate sustainable development, logging codes of practice must explicitly link their soil erosion reduction strategies to soil erosion and downstream water quality thresholds, otherwise they will be ineffective at minimizing the impacts of logging activities. The approach taken here to explicitly examine soil erosion rates and downstream water quality in relation to best management practices and increasing land clearing should be applied more broadly across a range of ecosystems to inform decision-making about the socioeconomic and environmental trade-offs associated with logging, and other types of land use change.

Cropping and tillage systems effects on soil erosion under climate change in Oklahoma

USDA-ARS?s Scientific Manuscript database

Soil erosion under future climate change is very likely to increase due to projected increases in frequency and magnitude of heavy storms. The objective of this study is to quantify the effects of common cropping and tillage systems on soil erosion and surface runoff during 2010-2039 in central Okl...

Characterizing Sediment Supply to Rivers: Effects of Lithology, Climate, Weathering and Erosion on Rock-fragment Abundance in Granitic, Hillslope Soils

NASA Astrophysics Data System (ADS)

Riebe, C. S.; Marshall, J. A.; Sklar, L. S.; Granger, D. E.

2008-12-01

River incision sets the pace of landscape evolution and so is crucial to linkages among climate, tectonics and topography. Theoretical and experimental studies indicate that bedrock river incision should be regulated by both the quantity and caliber of sediment supply, which together affect the availability and persistence of bed-scouring tools in the channel. Rates of sediment supply are now quantified routinely using cosmogenic- radionuclide-based (CRN) measurements of hillslope erosion rates. Although grain-size data are also measured routinely (e.g., as part of state and federal soil surveys), they are not widely available for soils with well-constrained rates of erosion and weathering. As a result, there is much to learn about how weathering and erosion interrelate to regulate grain-size distributions in hillslope soils. Moreover, we lack a strong empirical basis for investigating how the rate and caliber of sediment supply affect bedrock river incision in natural systems. Here we compare new grain-size data with existing CRN-based rates of erosion and weathering for a series of granitic soils at two climatically diverse sites in the Sierra Nevada, California. Our results indicate that the percentage of coarse material---which presumably becomes the bedload that abrades and lowers channels---varies significantly across each site. At the colder, wetter site, differences in grain size and soil depth are substantial, despite little variability in erosion rates; coarse material abundance appears to increase with the density of bedrock outcrops, which increases with hillslope gradients, according to previous work. At the hotter, drier site, where rates of erosion and weathering vary by 10-fold, soil thickness and texture and the abundance of outcrops do not vary systematically across the landscape. We speculate that the differences in soil development across our two sites partly reflect effects of small differences in the ratio of biotite to hornblende in the

Flight Test Techniques for Quantifying Pitch Rate and Angle of Attack Rate Dependencies

NASA Technical Reports Server (NTRS)

Grauer, Jared A.; Morelli, Eugene A.; Murri, Daniel G.

2017-01-01

Three different types of maneuvers were designed to separately quantify pitch rate and angle of attack rate contributions to the nondimensional aerodynamic pitching moment coefficient. These maneuvers combined pilot inputs and automatic multisine excitations, and were own with the subscale T-2 and Bat-4 airplanes using the NASA AirSTAR flight test facility. Stability and control derivatives, in particular C(sub mq) and C(sub m alpha(.)) were accurately estimated from the flight test data. These maneuvers can be performed with many types of aircraft, and the results can be used to increase simulation prediction fidelity and facilitate more accurate comparisons with wind tunnel experiments or numerical investigations.

Polyacrylamide application versus forest residue mulching for reducing post-fire runoff and soil erosion.

PubMed

Prats, Sergio Alegre; Martins, Martinho António Dos Santos; Malvar, Maruxa Cortizo; Ben-Hur, Meni; Keizer, Jan Jacob

2014-01-15

For several years now, forest fires have been known to increase overland flow and soil erosion. However, mitigation of these effects has been little studied, especially outside the USA. This study aimed to quantify the effectiveness of two so-called emergency treatments to reduce post-fire runoff and soil losses at the microplot scale in a eucalyptus plantation in north-central Portugal. The treatments involved the application of chopped eucalyptus bark mulch at a rate of 10-12 Mg ha(-1), and surface application of a dry, granular, anionic polyacrylamide (PAM) at a rate of 50 kg ha(-1). During the first year after a wildfire in 2010, 1419 mm of rainfall produced, on average, 785 mm of overland flow in the untreated plots and 8.4 Mg ha(-1) of soil losses. Mulching reduced these two figures significantly, by an average 52 and 93%, respectively. In contrast, the PAM-treated plots did not differ from the control plots, despite slightly lower runoff but higher soil erosion figures. When compared to the control plots, mean key factors for runoff and soil erosion were different in the case of the mulched but not the PAM plots. Notably, the plots on the lower half of the slope registered bigger runoff and erosion figures than those on the upper half of the slope. This could be explained by differences in fire intensity and, ultimately, in pre-fire standing biomass. © 2013 Elsevier B.V. All rights reserved.

Incidence and Pattern of Dental Erosion in Gastroesophageal Reflux Disease Patients.

PubMed

Ramachandran, Anupama; Raja Khan, Sulthan Ibrahim; Vaitheeswaran, Nandinee

2017-11-01

Gastroesophageal reflux disease (GERD) is a very common condition whose consequences of are localized not only in the esophagus; extra-esophageal involvement has frequently been reported. The aim of the study is to examine the incidence and pattern of dental erosion in GERD patients. A total of 50 patients were recruited in this study (control -25 and GERD -25). All participants diagnosed having GERD by the endoscopic examination by their gastroenterologist are included. The patients were examined for dental erosion and will be quantified using Basic erosive wear examination index. The results showed that the incidence of dental erosion was 88% as compared to 32% in the control group which was found to be statistically significant.

Lateral transport of soil carbon and land−atmosphere CO2 flux induced by water erosion in China

PubMed Central

Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G. L.; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

2016-01-01

Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land−atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt C⋅y−1 of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt C⋅y−1, equivalent to 8–37% of the terrestrial carbon sink previously assessed in China. Interestingly, the “hotspots,” largely distributed in mountainous regions in the most intensive sink areas (>40 g C⋅m−2⋅y−1), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty. PMID:27247397

Lateral transport of soil carbon and land-atmosphere CO2 flux induced by water erosion in China

NASA Astrophysics Data System (ADS)

Yue, Yao; Ni, Jinren; Ciais, Philippe; Piao, Shilong; Wang, Tao; Huang, Mengtian; Borthwick, Alistair G. L.; Li, Tianhong; Wang, Yichu; Chappell, Adrian; Van Oost, Kristof

2016-06-01

Soil erosion by water impacts soil organic carbon stocks and alters CO2 fluxes exchanged with the atmosphere. The role of erosion as a net sink or source of atmospheric CO2 remains highly debated, and little information is available at scales larger than small catchments or regions. This study attempts to quantify the lateral transport of soil carbon and consequent land-atmosphere CO2 fluxes at the scale of China, where severe erosion has occurred for several decades. Based on the distribution of soil erosion rates derived from detailed national surveys and soil carbon inventories, here we show that water erosion in China displaced 180 ± 80 Mt Cṡy-1 of soil organic carbon during the last two decades, and this resulted a net land sink for atmospheric CO2 of 45 ± 25 Mt Cṡy-1, equivalent to 8-37% of the terrestrial carbon sink previously assessed in China. Interestingly, the “hotspots,” largely distributed in mountainous regions in the most intensive sink areas (>40 g Cṡm-2ṡy-1), occupy only 1.5% of the total area suffering water erosion, but contribute 19.3% to the national erosion-induced CO2 sink. The erosion-induced CO2 sink underwent a remarkable reduction of about 16% from the middle 1990s to the early 2010s, due to diminishing erosion after the implementation of large-scale soil conservation programs. These findings demonstrate the necessity of including erosion-induced CO2 in the terrestrial budget, hence reducing the level of uncertainty.

(210)Pb as a tracer of soil erosion, sediment source area identification and particle transport in the terrestrial environment.

PubMed

Matisoff, Gerald

2014-12-01

Although (137)Cs has been used extensively to study soil erosion and particle transport in the terrestrial environment, there has been much less work using excess or unsupported (210)Pb ((210)Pbxs) to study the same processes. Furthermore, since (137)Cs activities in soils are decreasing because of radioactive decay, some locations have an added complication due to the addition of Chernobyl-derived (137)Cs, and the activities of (137)Cs in the southern hemisphere are low, there is a need to develop techniques that use (210)Pbxs to provide estimates of rates of soil erosion and particle transport. This paper reviews the current status of (210)Pbxs methods to quantify soil erosion rates, to identify and partition suspended sediment source areas, and to determine the transport rates of particles in the terrestrial landscape. Soil erosion rates determined using (210)Pbxs are based on the unsupported (210)Pb ((210)Pbxs) inventory in the soil, the depth distribution of (210)Pbxs, and a mass balance calibration ('conversion model') that relates the soil inventory to the erosion rate using a 'reference site' at which neither soil erosion nor soil deposition has occurred. In this paper several different models are presented to illustrate the effects of different model assumptions such as the timing, depth and rates of the surface soil mixing on the calculated erosion rates. The suitability of model assumptions, including estimates of the depositional flux of (210)Pbxs to the soil surface and the post-depositional mobility of (210)Pb are also discussed. (210)Pb can be used as one tracer to permit sediment source area identification. This sediment 'fingerprinting' has been extended far beyond using (210)Pb as a single radioisotope to include numerous radioactive and stable tracers and has been applied to identifying the source areas of suspended sediment based on underlying rock type, land use (roads, stream banks, channel beds, cultivated or uncultivated lands, pasture lands

ERMiT: Estimating Post-Fire Erosion in Probabilistic Terms

NASA Astrophysics Data System (ADS)

Pierson, F. B.; Robichaud, P. R.; Elliot, W. J.; Hall, D. E.; Moffet, C. A.

2006-12-01

Mitigating the impact of post-wildfire runoff and erosion on life, property, and natural resources have cost the United States government tens of millions of dollars over the past decade. The decision of where, when, and how to apply the most effective 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) is a web-based application that estimates erosion in probabilistic terms on burned and recovering forest, range, and chaparral lands. Unlike most erosion prediction models, ERMiT does not provide `average annual erosion rates;' rather, it provides a distribution of erosion rates with the likelihood of their occurrence. ERMiT combines rain event variability with spatial and temporal variabilities of hillslope burn severity, soil properties, and ground cover to estimate Water Erosion Prediction Project (WEPP) model input parameter values. Based on 20 to 40 individual WEPP runs, ERMiT produces a distribution of rain event erosion rates with a probability of occurrence for each of five post-fire years. Over the 5 years of modeled recovery, the occurrence probability of the less erodible soil parameters is increased and the occurrence probability of the more erodible soil parameters is decreased. In addition, the occurrence probabilities and the four spatial arrangements of burn severity (arrangements of overland flow elements (OFE's)), are shifted toward lower burn severity with each year of recovery. These yearly adjustments are based on field measurements made through post-fire recovery periods. ERMiT also provides rain event erosion rate distributions for hillslopes that have been treated with seeding, straw mulch, straw wattles and contour-felled log erosion barriers. Such output can help managers make erosion mitigation treatment decisions based on the probability of high sediment yields occurring, the value of resources at risk for damage, cost, and

Integration of fluvial erosion factors for predicting landslides along meandering rivers

NASA Astrophysics Data System (ADS)

Chen, Yi-chin; Chang, Kang-tsung; Ho, Jui-yi

2015-04-01

River incision and lateral erosion are important geomorphologic processes in mountainous areas of Taiwan. During a typhoon or storm event, the increase of water discharge, flow velocity, and sediment discharge enhances the power of river erosion on channel bank. After the materials on toe of hillslope were removed by river erosion, landslides were triggered at outer meander bends. Although it has been long expected that river erosion can trigger landslide, studies quantifying the effects of river erosion on landslide and the application of river erosion index in landslide prediction are still overlooked. In this study, we investigated the effect of river erosion on landslide in a particular meanders landscape of the Jhoukou River, southern Taiwan. We developed a semi-automatic model to separate meandering lines into several reach segments based on the inflection points and to calculate river erosion indexes, e.g. sinuosity of meander, stream power, and stream order, for each reach segment. This model, then, built the spatial relationship between the reaches and its corresponding hillslopes, of which the toe was eroded by the reach. Based on the spatial relationship, we quantified the correlations between these indexes and landslides triggered by Typhoon Morakot in 2009 to examine the effects of river erosion on landslide. The correlated indexes were then used as landslide predictors in logistic regression model. Results of the study showed that there is no significant correlation between landslide density and meander sinuosity. This may be a result of wider channel dispersing the erosion at a meandering reach. On the other hand, landslide density at concave bank is significantly higher than that at convex bank in the downstream (stream order > 3), but that is almost the same in the upstream (stream order < 3). This may imply that river sediment play different roles between down- and upstream segments. River sediment in the upstream is an erosion agent vertically

High rate of vaginal erosions associated with the mentor ObTape.

PubMed

Yamada, Brian S; Govier, Fred E; Stefanovic, Ksenija B; Kobashi, Kathleen C

2006-08-01

The transobturator tape method is a newer surgical technique for the treatment of stress urinary incontinence. Limited data exist related to complications with this approach or the types of mesh products used. We report our experience with vaginal erosions associated with the Mentor ObTape and American Medical Systems Monarc transobturator slings. Beginning in December 2003 selected female patients with anatomic urinary incontinence were prospectively followed after placement of the Mentor ObTape. Beginning in January 2004 we also began using the American Medical Systems Monarc in similar patients. Patients were admitted overnight after surgery, discharged on oral antibiotics, and seen in the clinic at 6 weeks postoperatively. A total of 67 patients have undergone placement of the Mentor ObTape and 9 of those patients (13.4%) have had vaginal extrusions of the sling. Eight patients reported a history of persistent vaginal discharge. One patient presented initially to an outside facility with a left thigh abscess tracking to the left inguinal incision site. Each patient was taken back to the operating room for mesh removal. A total of 56 patients have undergone placement of the AMS Monarc and none have had any vaginal erosions. Our high rate of vaginal extrusion using the ObTape has led us to discontinue the use of this product in our institution. Continued followup of all of these patients will be of critical importance.

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.

Controlled Ultrasound Tissue Erosion

PubMed Central

Xu, Zhen; Ludomirsky, Achiau; Eun, Lucy Y.; Hall, Timothy L.; Tran, Binh C.; Fowlkes, J. Brian; Cain, Charles A.

2009-01-01

The ability of ultrasound to produce highly controlled tissue erosion was investigated. This study is motivated by the need to develop a noninvasive procedure to perforate the neonatal atrial septum as the first step in treatment of hypoplastic left heart syndrome. A total of 232 holes were generated in 40 pieces of excised porcine atrial wall by a 788 kHz single-element transducer. The effects of various parameters [e.g., pulse repetition frequency (PRF), pulse duration (PD), and gas content of liquid] on the erosion rate and energy efficiency were explored. An Isppa of 9000 W/cm2, PDs of 3, 6, 12, and 24 cycles; PRFs between 1.34 kHz and 66.7 kHz; and gas saturation of 40–55% and 79–85% were used. The results show that very short pulses delivered at certain PRFs could maximize the erosion rate and energy efficiency. We show that well-defined perforations can be precisely located in the atrial wall through the controlled ultrasound tissue erosion (CUTE) process. A preliminary in vivo experiment was conducted on a canine subject, and the atrial septum was perforated using CUTE. PMID:15244286

Smartphone imagery to analyze animal-induced erosion in riverbanks

NASA Astrophysics Data System (ADS)

Sofia, Giulia; Masin, Roberta; Tarolli, Paolo

2016-04-01

Among the most invasive species, the Coypu (Myocastor coypus) best exemplifies the widespread damage caused by alien species to ecosystems, with effects on crops, riverine systems, and hydraulic structures. The extent of the latter impact is still rarely quantified, despite the increasing economic and social importance. In northern Italy, Coypu damages to the drainage network have multiple aspects. One main issue is related to the weakening of earthen structures: burrows significantly reduce the integrity of the banks, and potentially contribute to the bank failure. A second concern is related to the agricultural activities nearby the channels. When burrows are present, soil may collapse when subjected to the weight of heavy objects on the surface (such as vehicles and farm machinery). A third issue is connected on the impact of burrowing activities on riparian buffer zones. Coypu burrows create specific flowing paths for the water, delivering water and sediment from the fields directly to the drainage system, thus possibly reducing the efficiency of these zones, and improving the risk of surface water contamination. The purpose of this research is to provide a new perspective, from a geoscience point of view, on Coypu damages to riverbanks, showing the effectiveness of a low-cost approach to model surface burrowing damages and to quantify the related erosion. The work is based on the Structure-from-Motion (SfM) photogrammetric method. To quantify the damages, high-resolution 3D models of the riverbanks were reconstructed from imagery acquired with a smartphone (Prosdocimi et al. 2015). From these models, it was possible to determine the volume of the animal-induced erosion. Proven its effectiveness, the proposed method could allow the creation of a database of damages. Researchers could test the flexibility of the approach to determine the distribution of erosion along the whole drainage system as an index of damage region wide, and to determine the severity of

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.

Development of a virtual tool for the quantification and the analysis of soil erosion in olive orchards based on RUSLE

NASA Astrophysics Data System (ADS)

Marín, Víctor; Taguas, Encarnación V.; Redel, María Dolores; Gómez, Jose A.

2013-04-01

Erosion rates above 30 t ha-1 yr-1 have been measured in hilly agricultural regions such as Andalusia in Southern Spain, associated to orchard crops (Gómez et al., 2008). In this region, there are 1.48 Mha of olive groves (CAP, 2007), which are essential in terms of income, employment and landscape. The acquisition of training and experience in modelling soil erosion is difficult by the conventional system teaching for students as well as specific technicians. This paper presents a telematic training/analysis tool, CREO (Calculator of Rates of Erosion in Olive crops/ Calculadora RUSLE para Erosión en Olivar), to quantify erosion rates in olive grove areas based on the Revised Universal Soil Loss Equation (RUSLE; Renard et al., 1997) and on specific information published on soil losses and soil characteristics in olive orchards in Southern Spain. The tool has been programmed with Matlab R2008a from MathWorks Inc. (USA), although it could be used as an executable program in Spanish and English language by interested users. It consists of seven menus with visual material where different sources, databases and methodologies are presented to quantify soil rates (A = R.K.LS.C.P) by the calculation of six factors.A is computed in t ha-1 yr-1; R is the rainfall erosivity factor (MJ mm ha-1.h-1 yr-1); K represents the soil erodibility (t ha h ha-1 MJ-1 mm-1); L is the slope length factor and S is the slope gradient factor (dimensionless); C is a cover management factor (dimensionless) and P is a support practice factor (dimensionless). Different equations and methodologies can be selected by the user for the calculation of each factor while recommendations and advice can be showed for the suitable use of the tool. It is expected that CREO was a valuable helpful tool in environmental studies associated to olive orchard land use and its further use allows a better understanding of the interaction among the different factors involved, and better access to available

Glacier Erosion and Response to Climate in Chilean Patagonia

NASA Astrophysics Data System (ADS)

Koppes, M.; Hallet, B.; Stewart, R.

2006-12-01

A vibrant dimension in current research on landscape evolution is the potential impact of climate change on erosion rates due to differences in efficiency of glacial and non-glacial erosion processes. The climate-sensitive rate and spatial distribution of erosion can be as important as the tectonic environment in determining the development of mountain ranges. To evaluate properly how glacial erosion influences orogenic processes and reflects climate variability, it is necessary to understand how ice dynamics control erosion rates. The Patagonian Andes are a unique laboratory for documenting glacial erosion in a range of precipitation and thermal regimes, as zonal atmospheric circulation in the region creates strong latitudinal gradients. We will present relevant findings from two tidewater glaciers in Chilean Patagonia: San Rafael glacier, which drains the northern portion of the North Patagonian Icefield (46.6S, 74W), and Marinelli glacier, the largest glacier in the Cordillera Darwin of Tierra del Fuego (54.6S, 69W). Both glaciers have been in steady retreat during the latter half of the 20th century, and both calve into a fjord or lagoon, which provides an efficient trap for the sediment eroded by the glacier and deposited at the calving front. The reconstructed flux of ice into the glaciers is compared to the retreat of the ice fronts and to the sediment flux to examine the influence of ice dynamics on the rate of glacier erosion. NCEP-NCAR Reanalysis climate data, adjusted to local conditions by correlation with automatic weather stations installed at the glacier termini and coupled to a model of orographic enhancement of precipitation over the glacier basin, were used to reconstruct the daily precipitation input into and ablation output from the glaciers during the last 50 years. The sediment flux out of the glaciers during this period was calculated from acoustic reflection profiles of the sediments accumulated in the proglacial fjords, and used to infer

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.

The barley straw residues avoid high erosion rates in persimmon plantations. Eastern Spain

NASA Astrophysics Data System (ADS)

Cerdà, Artemi; González Pelayo, Óscar; Giménez-Morera, Antonio; Jordán, Antonio; Novara, Agata; Pereira, Paulo; Mataix-Solera, Jorge

2015-04-01

World persimmon production is 4 Millions tones and China produce more than 80 % of the total world yield. Korea and Japan are the second and the third producers respectively with 0.4 and 0.2 millions tones, and all three Asian countries concentrate more than 95 % of the world production. Spain produce less than 0.1 million tones but there is a sudden increase in new plantations due to the high prices and the new marked developed in Europe, Brazil and Arabic countries. The new chemically managed and highly mechanized plantations in Eastern Spain are using high doses of herbicides and the lack of vegetation is triggering high erosion rates. This paper aims to contribute with information about the soil losses on this new persimmon plantations and to develop strategies to reduce the soil and water losses. A 15 years old plantation of persimmon (Dyospirus lotus) was selected in Eastern Spain (Canals Municipality, La Costera District) to measure the soil losses on No-Tillage bare (herbicide treatments) management and on barley straw covered plots. The straw cover was applied 3 days before the expereriments at at doses that cover more than 50 % of the soil surface using 75 gr of straw per m2. Rainfall simulations under 55 mm h-1 rainfall intensity during one hour on 0.25 m2 plots were carried out on plots paired plots: bare and covered with straw. The measurements were carried out during July 2014 on paired plots, under very dry soil moisture contents ranging from 4.65 to 7.87 %. The results show that the 3% cover of vegetation of the control plots moved to more than 60% due to the application of the straw. This induced a delayed ponding (from 60 to 309 seconds) and surface runoff (from 262 to 815 seconds) and runoff outlet (418 to 1221 seconds). The runoff coefficients moved from 60 % in the control plots to 29 % in the straw covered and the runoff sediment concentration was dramatically reduced from 11 to 1 g l-1. The total soil losses were higher that 1 Kg per plot in

QUANTIFICATION OF GLACIAL EROSION IN THE ALPS USING VERY LOW-TEMPERATURE THERMOCHRONOLOGY (OSL & AHe)

NASA Astrophysics Data System (ADS)

Champagnac, J.; Herman, F.; Rhodes, E. J.; Fellin, M.; Jaiswal, M.; Schwenninger, J.; Reverman, R. L.

2009-12-01

The impact of glaciations on the topography of the Alps is still unclear: Long-term denudation rate determined by low-T thermochronology are in the range of 0.2 to 1 mm/yr, and increased during the Plio-Quaternary by 3 fold (Vernon et al., 2008). Such an increase is also documented by peri-alpine sediment budget (Kuhleman, 2000), with a similar increase in sediment yields since 5-3 Ma. This increase was considered as evidence of a climatically-driven surface process change, attributed to increased precipitation (Cederbom et al., 2004) and erosion by glacial processes (Champagnac et al., 2007). The timing of the onset of intense glacial erosion as well as its rates are still ambiguous. The glacial erosion seems to have accelerated around 0.9 Ma as suggested by the ten fold increase of incision rates of a valley in the Central Alps (Häuselmann et al., 2007), and by information about vegetation and sedimentologic changes (Muttoni et al., 2003). There is however no direct quantification of topographic change during the Plio-Quaternary. We present here how we use OSL-thermochronology, a new thermochronometer of exceptionally low closure temperature (about 30°-40°C) (Herman et al subm.), new {U-Th}/He on apatites data, and a glacial erosion model (Herman and Braun 2008) to estimate topographic changes in the Alps in response to glaciations. Because of their low closure temperature, OSL and AHe thermochronology enables quantification of events of less than 1 Ma at very small wavelength of the topography. We collected two vertical profiles, one in the Zermatt Valley (Valais) and one in Maurienne Valley (Savoy). We infer from these results changes in topography, date and quantify relief creation under glacial-interglacial cycles. Cederbom, C.E, et al., Climate induced rebound and exhumation of the European Alps. Geology 32, 709-712 (2000). Champagnac, J.-D., et al., Quaternary erosion-induced isostatic rebound in the western Alps. Geology 35, 195-198 (2007). Ha

Effect of erodent particles on the erosion of metal specimens

NASA Astrophysics Data System (ADS)

Razzaque, M. Mahbubur; Alam, M. Khorshed; Khan, M. Ishak

2016-07-01

This paper presents the experimental results of the measurement of erosion rate of carbon steel specimens in sand water slurry system in a slurry pot tester. Sylhet sand has been sieved to get three sizes of erodent particles; namely, less than 250 micron, 250 to 590 micron and 590 to 1190 micron. Experiments are done with three sand concentrations (10%, 15% and 20%). The rate of erosion of the carbon steel specimens is measured as the loss of weight per unit surface area per unit time under the dynamic action of solid particles. The eroded surfaces of the specimens are examined using Scanning Electron Microscopy (SEM) to visualize the impact of the slurry of various conditions. It is seen that irrespective of the particle size the rate of erosion increases with the increase of slurry concentration. This increment of erosion rate at high concentration is high for large particles. High erosion rate is observed in case of large sand particles. In case of small and fine particles erosion rate is small because of low impact energy as well as the wastage of energy to overcome the hindrance of the finer particles before striking on the specimen surface.

Erosion and re-deposition of lithium and boron coatings under high-flux plasma bombardment

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

Abrams, Tyler Wayne

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

Effects of cropping and tillage systems on soil erosion under climate change in Oklahoma

USDA-ARS?s Scientific Manuscript database

Soil erosion under future climate change is very likely to increase due to projected increases in frequency and magnitude of heavy storms. The objective of this study is to quantify the effects of common cropping and tillage systems on soil erosion and surface runoff during 2010-2039 in central Okl...

Tolerable soil erosion in Europe

NASA Astrophysics Data System (ADS)

Verheijen, Frank; Jones, Bob; Rickson, Jane; Smith, Celina

2010-05-01

Soil loss by erosion has been identified as an important threat to soils in Europe* and is recognised as a contributing process to soil degradation and associated deterioration, or loss, of soil functioning. From a policy perspective, it is imperative to establish well-defined baseline values to evaluate soil erosion monitoring data against. For this purpose, accurate baseline values - i.e. tolerable soil loss - need to be differentiated at appropriate scales for monitoring and, ideally, should take soil functions and even changing environmental conditions into account. The concept of tolerable soil erosion has been interpreted in the scientific literature in two ways: i) maintaining the dynamic equilibrium of soil quantity, and ii) maintaining biomass production, at a location. The first interpretation ignores soil quality by focusing only on soil quantity. The second approach ignores many soil functions by focusing only on the biomass (particularly crop) production function of soil. Considering recognised soil functions, tolerable soil erosion may be defined as 'any mean annual cumulative (all erosion types combined) soil erosion rate at which a deterioration or loss of one or more soil functions does not occur'. Assumptions and problems of this definition will be discussed. Soil functions can generally be judged not to deteriorate as long as soil erosion does not exceed soil formation. At present, this assumption remains largely untested, but applying the precautionary principle appears to be a reasonable starting point. Considering soil formation rates by both weathering and dust deposition, it is estimated that for the majority of soil forming factors in most European situations, soil formation rates probably range from ca. 0.3 - 1.4 t ha-1 yr-1. Although the current agreement on these values seems relatively strong, how the variation within the range is spatially distributed across Europe and how this may be affected by climate, land use and land management

Corneal erosions, bacterial contamination of contact lenses, and microbial keratitis.

PubMed

Willcox, Mark D P; Naduvilath, Thomas J; Vaddavalli, Pravin K; Holden, Brien A; Ozkan, Jerome; Zhu, Hua

2010-11-01

To estimate the rate of corneal erosion coupled with gram-negative bacterial contamination of contact lenses and compare this with the rate of microbial keratitis (MK) with contact lenses. The rate of corneal erosion and contact lens contamination by gram-negative bacteria were calculated from several prospective trials. These rates were used to calculate the theoretical rate of corneal erosion happening at the same time as wearing a contact lens contaminated with gram-negative bacteria. This theoretical rate was then compared with the rates of MK reported in various epidemiological and clinical trials. Corneal erosions were more frequent during extended wear (0.6-2.6% of visits) compared with daily wear (0.01-0.05% of visits). No corneal erosions were observed for lenses worn on a daily disposable basis. Contamination rates for lenses worn on a daily disposable basis were the lowest (2.4%), whereas they were the highest for low Dk lenses worn on an extended wear basis (7.1%). The estimated rate of corneal erosions occurring at the same time as wearing lenses contaminated with gram-negative bacteria was the lowest during daily wear of low Dk lenses (1.56/10,000 [95% CI: 0.23-10.57]) and the highest during extended wear of high Dk lenses (38.55/10,000 [95% CI: 24.77-60.04]). These rates were similar in magnitude to the rates reported for MK of different hydrogel lenses worn on differing wear schedules. The coincidence of corneal erosions during lens wear with gram-negative bacterial contamination of lenses may account for the relative incidence of MK during lens wear with different lens materials and modes of use.

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

Whole Watershed Quantification of Net Carbon Fluxes by Erosion and Deposition within the Christina River Basin Critical Zone Observatory

NASA Astrophysics Data System (ADS)

Aufdenkampe, A. K.; Karwan, D. L.; Aalto, R. E.; Marquard, J.; Yoo, K.; Wenell, B.; Chen, C.

2013-12-01

We have proposed that the rate at which fresh, carbon-free minerals are delivered to and mix with fresh organic matter determines the rate of carbon preservation at a watershed scale (Aufdenkampe et al. 2011). Although many studies have examined the role of erosion in carbon balances, none consider that fresh carbon and fresh minerals interact. We believe that this mechanism may be a dominant sequestration process in watersheds with strong anthropogenic impacts. Our hypothesis - that the rate of mixing fresh carbon with fresh, carbon-free minerals is a primary control on watershed-scale carbon sequestration - is central to our Christina River Basin Critical Zone Observatory project (CRB-CZO, http://www.udel.edu/czo/). The Christina River Basin spans 1440 km2 from piedmont to Atlantic coastal plain physiographic provinces in the states of Pennsylvania and Delaware, and experienced intensive deforestation and land use beginning in the colonial period of the USA. Here we present a synthesis of multi-disciplinary data from the CRB-CZO on materials as they are transported from sapprolite to topsoils to colluvium to suspended solids to floodplains, wetlands and eventually to the Delaware Bay estuary. At the heart of our analysis is a spatially-integrated, flux-weighted comparison of the organic carbon to mineral surface area ratio (OC/SA) of erosion source materials versus transported and deposited materials. Because source end-members - such as forest topsoils, farmed topsoils, gullied subsoils and stream banks - represent a wide distribution of initial, pre-erosion OC/SA, we quantify source contributions using geochemical sediment fingerprinting approaches (Walling 2005). Analytes used for sediment fingerprinting include: total mineral elemental composition (including rare earth elements), fallout radioisotope activity for common erosion tracers (beryllium-7, beryllium-10, lead-210, cesium-137), particle size distribution and mineral specific surface area, in addition

Investigation of plasma-induced erosion of multilayer condenser optics

NASA Astrophysics Data System (ADS)

Anderson, Richard J.; Buchenauer, Dean A.; Williams, K. A.; Clift, W. M.; Klebanoff, L. E.; Edwards, N. V.; Wood, O. R., II; Wurm, S.

2005-05-01

Experiments are presented that investigate the mechanistic cause of multilayer erosion observed from condenser optics exposed to EUV laser-produced plasma (LPP) sources. Using a Xe filament jet source excited with Nd-YAG laser radiation (300 mJ/pulse), measurements were made of material erosion from Au, Mo, Si and C using coated quartz microbalances located 127 mm from the plasma. The observed erosion rates were as follows: Au=99nm/106 shots, Mo= 26nm/106 shots, Si=19nm/106 shots, and C=6nm/106 shots. The relative ratio Au:Mo:Si:C of erosion rates observed experimentally, 16:4:3:1 compares favorably with that predicted from an atomic sputtering model assuming 20 kV Xe ions, 16:6:4:1. The relative agreement indicates that Xe-substrate sputtering is largely responsible for the erosion of Mo/Si multilayers on condenser optics that directly face the plasma. Time-of-flight Faraday cup measurements reveal the emission of high energy Xe ions from the Xe-filament jet plasma. The erosion rate does not depend on the repetition rate of the laser, suggesting a thermal mechanism is not operative. The Xe-filament jet erosion is ~20x that observed from a Xe spray jet. Since the long-lived (millisecond time scale) plasma emanating from these two sources are the same to within ~30%, sputtering from this long-lived plasma can be ruled out as an erosion agent.

Erosion rate study at the Allchar deposit (Macedonia) based on radioactive and stable cosmogenic nuclides (26 Al, 36 Cl, 3 He, and 21 Ne)

PubMed Central

Cvetković, V.; Niedermann, S.; Pejović, V.; Amthauer, G.; Boev, B.; Bosch, F.; Aničin, I.; Henning, W. F.

2016-01-01

Abstract This paper focuses on constraining the erosion rate in the area of the Allchar Sb‐As‐Tl‐Au deposit (Macedonia). It contains the largest known reserves of lorandite (TlAsS2), which is essential for the LORanditeEXperiment (LOREX), aimed at determining the long‐term solar neutrino flux. Because the erosion history of the Allchar area is crucial for the success of LOREX, we applied terrestrial in situ cosmogenic nuclides including both radioactive (26Al and 36Cl) and stable (3He and 21Ne) nuclides in quartz, dolomite/calcite, sanidine, and diopside. The obtained results suggest that there is accordance in the values obtained by applying 26Al, 36Cl, and 21Ne for around 85% of the entire sample collection, with resulting erosion rates varying from several tens of m/Ma to ∼165 m/Ma. The samples from four locations (L‐8 CD, L1b/R, L1c/R, and L‐4/ADR) give erosion rates between 300 and 400 m/Ma. Although these localities reveal remarkably higher values, which may be explained by burial events that occurred in part of Allchar, the erosion rate estimates mostly in the range between 50 and 100 m/Ma. This range further enables us to estimate the vertical erosion rate values for the two main ore bodies Crven Dol and Centralni Deo. We also estimate that the lower and upper limits of average paleo‐depths for the ore body Centralni Deo from 4.3 Ma to the present are 250–290 and 750–790 m, respectively, whereas the upper limit of paleo‐depth for the ore body Crven Dol over the same geological age is 860 m. The estimated paleo‐depth values allow estimating the relative contributions of 205Pb derived from pp‐neutrino and fast cosmic‐ray muons, respectively, which is an important prerequisite for the LOREX experiment. PMID:27587984

Quantifying Hillslope to Watershed Erosional Response Following Wildfire

NASA Astrophysics Data System (ADS)

Vega, S.; Pierson, F. B.; Williams, C. J.; Brooks, E. S.; Strand, E. K.; Seyfried, M. S.; Murdock, M.; Pierce, J. L.; Roehner, C.; Lindsay, K.; Robichaud, P. R.; Brown, R. E.

2017-12-01

Across the western US, wildfires in sagebrush vegetation are occurring at a more frequent rate and higher severity. This has resulted in a decline of sagebrush rangeland. The changing fire regime can be attributed to invasive plant species and warming climate conditions. As the result of wildfire, protective vegetation cover is removed leaving the soil bare and exposed to erosion. Erosion following wildfire is a main concern among land managers due to the threat it poses to resources, infrastructure, and human health. Numerous studies have used artificial rainfall to assess post-fire runoff and erosion and rehabilitation treatment effectiveness. These results have found that high intensity rain events typical of summer convective storms drive post-fire erosion. The purpose of this study is to improve scientific understanding of how site-specific physical and biological attributes affect hillslope to watershed scale sediment yield on a mountainous burned sagebrush landscape. This study uses natural rainfall and a network of silt fences to quantify hillslope to watershed scale erosion response. The erosional drivers over various spatial scales were evaluated in context with vegetation recovery for a 2 year post-fire period. A network of silt fences was installed over long and short hillslope distances and in swales within the 130 ha Murphy Creek catchment in the Reynolds Creek Experimental Watershed in southwestern Idaho. We evaluated: 1) vegetation, soils, and sediment delivery across multiple spatial scales associated with 30 silt fences spanning north and south facing aspects, 2) precipitation input at two meteorological stations, and 3) watershed streamflow and sediment discharge from an existing weir. During the first and second year post-fire, the swales on both aspects produced more sediment than the short and long hillslopes. The results suggest that significant amounts of sediment and organic matter were deposited in the swales creating drifts. Sediment

Solid particle erosion of polymers and composites

NASA Astrophysics Data System (ADS)

Friedrich, K.; Almajid, A. A.

2014-05-01

After a general introduction to the subject of solid particle erosion of polymers and composites, the presentation focusses more specifically on the behavior of unidirectional carbon fiber (CF) reinforced polyetheretherketone (PEEK) composites under such loadings, using different impact conditions and erodents. The data were analyzed on the basis of a newly defined specific erosive wear rate, allowing a better comparison of erosion data achieved under various testing conditions. Characteristic wear mechanisms of the CF/PEEK composites consisted of fiber fracture, matrix cutting and plastic matrix deformation, the relative contribution of which depended on the impingement angles and the CF orientation. The highest wear rates were measured for impingement angles between 45 and 60°. Using abrasion resistant neat polymer films (in this case PEEK or thermoplastic polyurethane (TPU) ones) on the surface of a harder substrate (e.g. a CF/PEEK composite plate) resulted in much lower specific erosive wear rates. The use of such polymeric films can be considered as a possible method to protect composite surfaces from damage caused by minor impacts and erosion. In fact, they are nowadays already successfully applied as protections for wind energy rotor blades.

River Bank Erosion and the Influence of Environmental Flow Management.

PubMed

Vietz, Geoff J; Lintern, Anna; Webb, J Angus; Straccione, David

2018-03-01

Environmental flows aim to influence river hydrology to provide appropriate physical conditions for ecological functioning within the restrictions of flow regulation. The hydrologic characteristics of flow events, however, may also lead to unintended morphologic effects in rivers, such as increases in riverbank erosion beyond natural rates. This may negatively impact habitat for biota, riparian infrastructure, and land use. Strategic environmental flow delivery linked to monitoring and adaptive management can help mitigate risks. We monitor riverbank condition (erosion and deposition) relative to environmental flows on the Goulburn River, Victoria, Australia. We describe the process of adaptive management aimed at reducing potential impacts of flow management on bank condition. Field measurements (erosion pins) quantify the hydrogeomorphic response of banks to the delivery of planned and natural flow events. Managed flows provide opportunities for monitoring riverbank response to flows, which in turn informs planning. The results demonstrate that environmental flows have little influence on bank erosion and visual perceptions in the absence of monitoring are an unreliable guide. This monitoring project represents a mutually beneficial, science-practice partnership demonstrating that a traditional 'know then do' approach can be foreshortened by close collaboration between researchers and managers. To do so requires transparent, often informal lines of communication. The benefits for researchers-a more strategic and targeted approach to monitoring activities; and benefits for the practitioners-reduced time between actions and understanding response; mean that a learn by doing approach is likely to have better outcomes for researchers, stakeholders, the public, and the environment.

River Bank Erosion and the Influence of Environmental Flow Management

NASA Astrophysics Data System (ADS)

Vietz, Geoff J.; Lintern, Anna; Webb, J. Angus; Straccione, David

2018-03-01

Environmental flows aim to influence river hydrology to provide appropriate physical conditions for ecological functioning within the restrictions of flow regulation. The hydrologic characteristics of flow events, however, may also lead to unintended morphologic effects in rivers, such as increases in riverbank erosion beyond natural rates. This may negatively impact habitat for biota, riparian infrastructure, and land use. Strategic environmental flow delivery linked to monitoring and adaptive management can help mitigate risks. We monitor riverbank condition (erosion and deposition) relative to environmental flows on the Goulburn River, Victoria, Australia. We describe the process of adaptive management aimed at reducing potential impacts of flow management on bank condition. Field measurements (erosion pins) quantify the hydrogeomorphic response of banks to the delivery of planned and natural flow events. Managed flows provide opportunities for monitoring riverbank response to flows, which in turn informs planning. The results demonstrate that environmental flows have little influence on bank erosion and visual perceptions in the absence of monitoring are an unreliable guide. This monitoring project represents a mutually beneficial, science-practice partnership demonstrating that a traditional `know then do' approach can be foreshortened by close collaboration between researchers and managers. To do so requires transparent, often informal lines of communication. The benefits for researchers-a more strategic and targeted approach to monitoring activities; and benefits for the practitioners-reduced time between actions and understanding response; mean that a learn by doing approach is likely to have better outcomes for researchers, stakeholders, the public, and the environment.

Preventive Effect of CPP-ACPF Paste and Fluoride Toothpastes Against Erosion and Erosion Plus Abrasion 
In Vitro - A 3D Profilometric Analysis.

PubMed

Soares, Genaina Guimarães; Magalhães, Pâmela Amorim; Fonseca, Ana Beatriz Monteiro; Tostes, Monica Almeida; Silva, Eduardo Moreira da; Coutinho, Thereza Christina Lopes

To evaluate the effect of CPP-ACPF paste and fluoride toothpastes on enamel subjected to erosion and erosion plus abrasion in vitro. A total of 220 human enamel blocks were divided into eleven groups (n = 20): CPP-ACPF paste (MPP), potassium nitrate/sodium fluoride toothpaste (PE), sodium fluoride toothpaste (FD), fluoride-free toothpaste (SO) and control (erosion only with no paste or toothpastes; CO) according to the experimental design: erosion or erosion plus abrasion immediately after erosion (ERO+I-ABR) or 30 min after erosion (ERO+30min-ABR). For 5 days, the specimens were subjected to: (1) erosive challenge (EC) (cola drink, 4 x 5 min/day), topical application of the undiluted paste or diluted toothpastes (1:2 w/w) (4 x 1 min/ day) plus 1 h in artificial saliva (AS) between cycles and overnight; or (2) EC plus abrasion (4 x /60 s/day) performed with the diluted toothpastes (no MMP) plus 1 h in AS between cycles and overnight. Erosion depth was quantified through a 3D profilometer. Data were analysed using Kruskal-Wallis, Mann-Whitney and Wilcoxon tests (p = 0.05). CPP-ACPF paste and NaF toothpaste showed lowest enamel wear among groups and reduced tissue loss by 89% in erosion challenge. Abrasion led to higher enamel wear than erosion only (p = 0.030). ERO+30min-ABR had no protective effect when compared to ERO+I-ABR (p > 0.05). A high frequency of CPP-ACPF paste application (4x daily) is effective in reducing the effects of erosion. A waiting period before performing toothbrushing does not protect enamel against erosion regardless the composition of the toothpastes.

Are erosion regimes in SE Australian forests responding to anthropogenic climate change?

NASA Astrophysics Data System (ADS)

Nyman, P.; Rutherfurd, I.; Lane, P. N. J.; Sheridan, G. J.

2017-12-01

In southeast Australia a series of exceptional climate events over the last decade have resulted in widespread debris flow activity across the region. The Millennium Drought (1996-2010), extreme fire-weather and record breaking rainfall in the La Nina year of 2011 have all contributed to an intensification of processes such as runoff production and mass failures that lead to debris flows. Debris flows in landmark locations such as the Grampians and Wilsons Promontory National Parks in 2011 were triggered by mass failure as a result of large volumes of intense summer rainfall. Runoff generated debris flows in burned areas have been occurring regularly and in large numbers along the East Coast Dividing Range from the Warrumbungle Mountains (New South Wales) in the north to Kinglake (Victoria) in the south. In northeast Victoria debris flows have been delivering sediment to the Ovens River following wildfires in 2003, 2007, 2009 and in 2013. The impact of these erosion events on infrastructure, water quality and aquatic ecosystems are considerable and important questions are emerging around i) how frequently events have occurred in the past, ii) the importance of fire as a geomorphic agent, and iii) the effects of climate change on erosion regimes. In this paper we investigate the conditions under which these debris flows occurred, and examine the underlying climatic events in context of historical records. Using data on rainfall distributions and fire history dating back to the 1960s we quantify the frequency with which catchments are primed for extreme erosion events. With these data we begin to speculate on whether or not current catchment conditions (e.g. soil depths, colluvial storage and accumulation rate) is consistent with the erosion regimes we observe. The broader aim of our research is to quantify debris flow thresholds using geophysical response models and use these models to determine the sensitivity of debris flow frequency to climatic forcing. In the

Stable isotope labeling tandem mass spectrometry (SILT) to quantify protein production and clearance rates

PubMed Central

Bateman, Randall J.; Munsell, Ling Y.; Chen, Xianghong; Holtzman, David M.; Yarasheski, Kevin E.

2007-01-01

In all biological systems, protein amount is a function of the rate of production and clearance. The speed of a response to a disturbance in protein homeostasis is determined by turnover rate. Quantifying alterations in protein synthesis and clearance rates is vital to understanding disease pathogenesis (e.g., aging, inflammation). No methods exist for quantifying production and clearance rates of low abundance (femtomole) proteins in vivo. We describe a novel, mass spectrometry-based method for quantitating low abundance protein synthesis and clearance rates in vitro and in vivo in animals and humans. The utility of this method is demonstrated with amyloid-beta (Aß), an important low abundance protein involved in Alzheimer's disease pathogenesis. We used in vivo stable isotope labeling, immunoprecipitation of Aß from cerebrospinal fluid, and quantitative liquid chromatography electrospray-ionization tandem mass spectrometry (LC-ESI-tandem MS) to quantify human Aß protein production and clearance rates. The method is sensitive and specific for stable isotope labeled amino acid incorporation into CNS (± 1% accuracy). This in vivo method can be used to identify pathophysiologic changes in protein metabolism; and may serve as a biomarker for monitoring disease risk, progression, or response to novel therapeutic agents. The technique is adaptable to other macromolecules, such as carbohydrates or lipids. PMID:17383190

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.

Granitic boulder erosion caused by chaparral wildfire: Implications for cosmogenic radionuclide dating of bedrock surfaces

USGS Publications Warehouse

Kendrick, Katherine J.; Camille Partin,; Graham, Robert C.

2016-01-01

Rock surface erosion by wildfire is significant and widespread but has not been quantified in southern California or for chaparral ecosystems. Quantifying the surface erosion of bedrock outcrops and boulders is critical for determination of age using cosmogenic radionuclide techniques, as even modest surface erosion removes the accumulation of the cosmogenic radionuclides and causes significant underestimate of age. This study documents the effects on three large granitic boulders following the Esperanza Fire of 2006 in southern California. Spalled rock fragments were quantified by measuring the removed rock volume from each measured boulder. Between 7% and 55% of the total surface area of the boulders spalled in this single fire. The volume of spalled material, when normalized across the entire surface area, represents a mean surface lowering of 0.7–12.3 mm. Spalled material was thicker on the flanks of the boulders, and the height of the fire effects significantly exceeded the height of the vegetation prior to the wildfire. Surface erosion of boulders and bedrock outcrops as a result of wildfire spalling results in fresh surfaces that appear unaffected by chemical weathering. Such surfaces may be preferentially selected by researchers for cosmogenic surface dating because of their fresh appearance, leading to an underestimate of age.

Scaling up from field to region for wind erosion prediction using a field-scale wind erosion model and GIS

USGS Publications Warehouse

Zobeck, T.M.; Parker, N.C.; Haskell, S.; Guoding, K.

2000-01-01

Factors that affect wind erosion such as surface vegetative and other cover, soil properties and surface roughness usually change spatially and temporally at the field-scale to produce important field-scale variations in wind erosion. Accurate estimation of wind erosion when scaling up from fields to regions, while maintaining meaningful field-scale process details, remains a challenge. The objectives of this study were to evaluate the feasibility of using a field-scale wind erosion model with a geographic information system (GIS) to scale up to regional levels and to quantify the differences in wind erosion estimates produced by different scales of soil mapping used as a data layer in the model. A GIS was used in combination with the revised wind erosion equation (RWEQ), a field-scale wind erosion model, to estimate wind erosion for two 50 km2 areas. Landsat Thematic Mapper satellite imagery from 1993 with 30 m resolution was used as a base map. The GIS database layers included land use, soils, and other features such as roads. The major land use was agricultural fields. Data on 1993 crop management for selected fields of each crop type were collected from local government agency offices and used to 'train' the computer to classify land areas by crop and type of irrigation (agroecosystem) using commercially available software. The land area of the agricultural land uses was overestimated by 6.5% in one region (Lubbock County, TX, USA) and underestimated by about 21% in an adjacent region (Terry County, TX, USA). The total estimated wind erosion potential for Terry County was about four times that estimated for adjacent Lubbock County. The difference in potential erosion among the counties was attributed to regional differences in surface soil texture. In a comparison of different soil map scales in Terry County, the generalised soil map had over 20% more of the land area and over 15% greater erosion potential in loamy sand soils than did the detailed soil map. As

Quantifying tasks, ergonomic exposures and injury rates among school custodial workers.

PubMed

Village, J; Koehoorn, M; Hossain, S; Ostry, A

2009-06-01

A job exposure matrix of ergonomics risk factors was constructed for school custodial workers in one large school district in the province of British Columbia using 100 h of 1-min fixed-interval observations, participatory worker consensus on task durations and existing employment and school characteristic data. Significant differences in ergonomics risk factors were found by tasks and occupations. Cleaning and moving furniture, handling garbage, cleaning washrooms and cleaning floors were associated with the most physical risks and the exposure was often higher during the summer vs. the school year. Injury rates over a 4-year period showed the custodian injury rate was four times higher than the overall injury rate across all occupations in the school district. Injury rates were significantly higher in the school year compared with summer (12.2 vs. 7.0 per 100 full-time equivalents per year, p < 0.05). Custodial workers represent a considerable proportion of the labour force and have high injury rates, yet ergonomic studies are disproportionately few. Previous studies that quantified risk factors in custodial workers tended to focus on a few tasks or specific risk factors. This study, using participatory ergonomics and observational methods, systematically quantifies the broad range of musculoskeletal risk factors across multiple tasks performed by custodial workers in schools, adding considerably to the methodological literature.

Decadal-scale variation in dune erosion and accretion rates: An investigation of the significance of changing storm tide frequency and magnitude on the Sefton coast, UK

NASA Astrophysics Data System (ADS)

Pye, K.; Blott, S. J.

2008-12-01

Monitoring of frontal dune erosion and accretion on the Sefton coast in northwest England over the past 50 years has revealed significant spatial and temporal variations. Previous work has shown that the spatial variations primarily reflect longshore differences in beach and nearshore morphology, energy regime and sediment budget, but the causes of temporal variations have not previously been studied in detail. This paper presents the results of work carried out to test the hypothesis that a major cause of temporal variation is changes in the frequency and magnitude of storms, surges and resulting high tides. Dune toe erosion/accretion records dating from 1958 have been compared with tide gauge records at Liverpool and Heysham. Relatively high dune erosion rates at Formby Point 1958-1968 were associated with a relatively large number of storm tides. Slower erosion at Formby, and relatively rapid accretion in areas to the north and south, occurred during the 1970's and 1980's when there were relatively few major storm tides. After 1990 rates of dune erosion at Formby increased again, and dunes to the north and south experienced slower accretion. During this period high storm tides have been more frequent, and the annual number of hours with water levels above the critical level for dune erosion has increased significantly. An increase in the rate of mean sea-level rise at both Liverpool and Heysham is evident since 1990, but we conclude that this factor is of less importance than the occurrence of extreme high tides and wave action associated with storms. The incidence of extreme high tides shows an identifiable relationship with the lunar nodal tidal cycle, but the evidence indicates that meteorological forcing has also had a significant effect. Storms and surges in the eastern Irish Sea are associated with Atlantic depressions whose direction and rate of movement have a strong influence on wind speeds, wave energy and the height of surge tides. However

Hillslope erosion rates in the oak savannas of the southwestern borderlands region

Treesearch

Aaron T. Kauffman; Cody L. Stropki; Peter F. Ffolliott; Gerald J. Gottfried; Daniel G. Neary

2007-01-01

Hillslope soil erosion on watershed landscapes can lower the productivity of upland sites and adversely impact water quality and downstream (off-site) areas. It is not surprising, therefore, that excessive soil erosion and the consequent sedimentation can represent significant costs to the land and people that are affected. The first known estimates of hillslope soil...

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

Soil erosion, sedimentation and the carbon cycle

NASA Astrophysics Data System (ADS)

Cammeraat, L. H.; Kirkels, F.; Kuhn, N. J.

2012-04-01

Historically soil erosion focused on the effects of on-site soil quality loss and consequently reduced crop yields, and off-site effects related to deposition of material and water quality issues such as increased sediment loads of rivers. In agricultural landscapes geomorphological processes reallocate considerable amounts of soil and soil organic carbon (SOC). The destiny of SOC is of importance because it constitutes the largest C pool of the fast carbon cycle, and which cannot only be understood by looking at the vertical transfer of C from soil to atmosphere. Therefore studies have been carried out to quantify this possible influence of soil erosion and soil deposition and which was summarized by Quinton et al. (2010) by "We need to consider soils as mobile systems to make accurate predictions about the consequences of global change for terrestrial biogeochemical cycles and climate feedbacks". Currently a debate exists on the actual fate of SOC in relation to the global carbon cycle, represented in a controversy between researchers claiming that erosion is a sink, and those who claim the opposite. This controversy is still continuing as it is not easy to quantify and model the dominating sink and source processes at the landscape scale. Getting insight into the balance of the carbon budget requires a comprehensive research of all relevant processes at broad spatio-temporal scales, from catchment to regional scales and covering the present to the late Holocene. Emphasising the economic and societal benefits, the merits for scientific knowledge of the carbon cycle and the potential to sequester carbon and consequently offset increasing atmospheric CO2 concentrations, make the fate of SOC in agricultural landscapes a high-priority research area. Quinton, J.N., Govers, G., Van Oost, K., Bardgett, R.D., 2010. The impact of agricultural soil erosion on biogeochemical cycling. Nature Geosci, 3, 311-314.

Tectonic and Climatic Implications of Late Miocene to Pleistocene (5.8-1.8 Ma) Paleo-Erosion Rates from the Rio Iruya Canyon, Northwest Argentina (23°S)

NASA Astrophysics Data System (ADS)

Fisher, G. B.; Amidon, W. H.; Luna, L. V.; Burbank, D. W.

2015-12-01

One fundamental hypothesis that underpins tectonic geomorphology is that climate can modify the pattern and magnitude of erosion in orogenic landscapes and in turn control deformation. While conceptually appealing, empirical evidence is often ambiguous owing to the inherent spatial coupling between present-day tectonic and precipitation maxima and/or the long-term blurring of climate signals by thermochronologic techniques. Although cosmogenic nuclides provide considerable insight into centennial to millennial scale tectonic-erosion-climate linkages, extracting long-term records of erosion from older sedimentary deposits has proved challenging. If successful, such records have the potential to reveal long-term relationships between erosion, uplift, and climate, which should integrate over time to match long term exhumation rates obtained from low temperature thermochronology. Here we utilize a unique field setting along a 100-m deep, young canyon (~100 years old) along the Rio Iruya in northwestern Argentina to create a high-resolution (~100 kyr) terrestrial record of paleo-erosion rates in the eastern Cordillera spanning the late Miocene to Pleistocene (5.8-1.8 Mya). In total, 49 cosmogenic 10Be samples were analyzed along with detailed magnetostratigraphy, U-Pb tephra ages, detrital zircon, and quartz trace elements to yield a detailed paleo-erosion rate, chronology, and provenance record for the Rio Iruya section. Apparent erosion rates occur in three different regimes: from 5.8-4.0 Ma rates are high with little variability, from 4.0- 2.3 Ma rates oscillate by a factor of 5 on a ~400 kyr timescale, and from 2.3-1.8 Ma they are again high without clear oscillations. These three regimes correspond to changes in provenance recorded by detrital zircons and quartz chemistry, and suggest that during the late Pliocene the eastern Cordillera was responding strongly to the 400 kyr eccentricity paced orbital frequency. This unique finding is both perplexing and

Soil carbon and nitrogen erosion in forested catchments: implications for erosion-induced terrestrial carbon sequestration

Treesearch

E. M. Stacy; S. C. Hart; C. T. Hunsaker; D. W. Johnson; A. A. Berhe

2015-01-01

Lateral movement of organic matter (OM) due to erosion is now considered an important flux term in terrestrial carbon (C) and nitrogen (N) budgets, yet most published studies on the role of erosion focus on agricultural or grassland ecosystems. To date, little information is available on the rate and nature of OM eroded from forest ecosystems. We present annual...

Effect of erodent particles on the erosion of metal specimens

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

Razzaque, M. Mahbubur, E-mail: mmrazzaque@me.buet.ac.bd; Alam, M. Khorshed; Khan, M. Ishak, E-mail: ishak.buet@gmail.com

2016-07-12

This paper presents the experimental results of the measurement of erosion rate of carbon steel specimens in sand water slurry system in a slurry pot tester. Sylhet sand has been sieved to get three sizes of erodent particles; namely, less than 250 micron, 250 to 590 micron and 590 to 1190 micron. Experiments are done with three sand concentrations (10%, 15% and 20%). The rate of erosion of the carbon steel specimens is measured as the loss of weight per unit surface area per unit time under the dynamic action of solid particles. The eroded surfaces of the specimens aremore » examined using Scanning Electron Microscopy (SEM) to visualize the impact of the slurry of various conditions. It is seen that irrespective of the particle size the rate of erosion increases with the increase of slurry concentration. This increment of erosion rate at high concentration is high for large particles. High erosion rate is observed in case of large sand particles. In case of small and fine particles erosion rate is small because of low impact energy as well as the wastage of energy to overcome the hindrance of the finer particles before striking on the specimen surface.« less

Challenges to Progress in Studies of Climate-Tectonic-Erosion Interactions

NASA Astrophysics Data System (ADS)

Burbank, D. W.

2016-12-01

Attempts to unravel the relative importance of climate and tectonics in modulating topography and erosion should compare relevant data sets at comparable temporal and spatial scales. Given that such data are uncommonly available, how can we compare diverse data sets in a robust fashion? Many erosion-rate studies rely on detrital cosmogenic nuclides. What time scales can such data address, and what landscape conditions do they require to provide accurate representations of long-term erosion rates? To what extent do large-scale, but infrequent erosional events impact long-term rates? Commonly, long-term erosion rates are deduced from thermochronologic data. What types of data are needed to test for consistency of rates across a given interval or change in rates through time? Similarly, spatial and temporal variability in precipitation or tectonics requires averaging across appropriate scales. How are such data obtained in deforming mountain belts, and how do we assess their reliability? This study describes the character and temporal duration of key variables that are needed to examine climate-tectonic-erosion interactions, explores the strengths and weaknesses of several study areas, and suggests the types of data requirements that will underpin enlightening "tests" of hypotheses related to the mutual impacts of climate, tectonics, and erosion.

Quantifying consumption rates of dissolved oxygen along bed forms

NASA Astrophysics Data System (ADS)

Boano, Fulvio; De Falco, Natalie; Arnon, Shai

2016-04-01

Streambed interfaces represent hotspots for nutrient transformations because they host different microbial species, and the evaluation of these reaction rates is important to assess the fate of nutrients in riverine environments. In this work we analyze a series of flume experiments on oxygen demand in dune-shaped hyporheic sediments under losing and gaining flow conditions. We employ a new modeling code to quantify oxygen consumption rates from observed vertical profiles of oxygen concentration. The code accounts for transport by molecular diffusion and water advection, and automatically determines the reaction rates that provide the best fit between observed and modeled concentration values. The results show that reaction rates are not uniformly distributed across the streambed, in agreement with the expected behavior predicted by hyporheic exchange theory. Oxygen consumption was found to be highly influenced by the presence of gaining or losing flow conditions, which controlled the delivery of labile DOC to streambed microorganisms.

Assessment of soil erosion sensitivity and post-timber-harvesting erosion response in a mountain environment of Central Italy

NASA Astrophysics Data System (ADS)

Borrelli, Pasquale; Schütt, Brigitta

2014-01-01

This study aimed to assess the effects of forest management on the occurrence of accelerated soil erosion by water. The study site is located in a mountainous area of the Italian Central Apennines. Here, forest harvesting is a widespread forestry activity and is mainly performed on the moderate to steep slopes of the highlands. Through modeling operations based on data on soil properties and direct monitoring of changes in the post-forest-harvesting soil surface level at the hillslope scale, we show that the observed site became prone to soil erosion after human intervention. Indeed, the measured mean soil erosion rate of 49 t ha- 1 yr- 1 for the harvested watershed is about 21 times higher than the rate measured in its neighboring undisturbed forested watershed (2.3 t ha- 1 yr- 1). The erosive response is greatly aggravated by exposing the just-harvested forest, with very limited herbaceous plant cover, to the aggressive attack of the heaviest annual rainfall without adopting any conservation practices. The erosivity of the storms during the first four months of field measurements was 1571 MJ mm h- 1 ha- 1 in total (i.e., from September to December 2008). At the end of the experiment (16 months), 18.8%, 26.1% and 55.1% of the erosion monitoring sites in the harvested watershed recorded variations equal or greater than 0-5, 5-10 and > 10 mm, respectively. This study also provides a quantification of Italian forestland surfaces with the same pedo-lithological characteristics exploited for wood supply. Within a period of ten years (2002-2011), about 9891 ha of coppice forest changes were identified and their potential soil erosion rates modeled.

Quantifying Temporal Genomic Erosion in Endangered Species.

PubMed

Díez-Del-Molino, David; Sánchez-Barreiro, Fatima; Barnes, Ian; Gilbert, M Thomas P; Dalén, Love

2018-03-01

Many species have undergone dramatic population size declines over the past centuries. Although stochastic genetic processes during and after such declines are thought to elevate the risk of extinction, comparative analyses of genomic data from several endangered species suggest little concordance between genome-wide diversity and current population sizes. This is likely because species-specific life-history traits and ancient bottlenecks overshadow the genetic effect of recent demographic declines. Therefore, we advocate that temporal sampling of genomic data provides a more accurate approach to quantify genetic threats in endangered species. Specifically, genomic data from predecline museum specimens will provide valuable baseline data that enable accurate estimation of recent decreases in genome-wide diversity, increases in inbreeding levels, and accumulation of deleterious genetic variation. Copyright © 2017 Elsevier Ltd. All rights reserved.

The Rockfall Buzzsaw: Quantifying the role of frost processes on mountain evolution

NASA Astrophysics Data System (ADS)

Hales, T.; Roering, J. J.

2006-12-01

The height and relief of high mountains reflects a balance between uplift, caused by tectonic and isostatic forces, and erosion, by fluvial, glacial, periglacial, and hillslope processes. Recently, models of mountain evolution have focused on the importance of glaciers in eroding deep valleys, a process referred to as the "glacial buzzsaw". Little attention has been paid to the role of periglacial processes, despite large scree slopes and rubble-covered glaciers being common in mountains. Frost cracking induced rockfall erosion has wide acceptance in the literature and a number of local studies have calculated high rockfall erosion rates in cold environments; but the question remains, how important is frost cracking in eroding bedrock in mountainous environments? We quantify how and where ice-driven mechanical erosion occurs in cold, bedrock-dominated landscapes using a simple one-dimensional numerical heat flow model. In our model, ice grows by water migration to colder regions in shallow rock by the reduction in chemical potential associated with intermolecular forces between ice and mineral surfaces, a process called segregation ice growth. Positive MAT sites are characterized by intense cracking in the top meter of the rock mass and a maximum frost penetration of ~4m. In contrast, negative MAT areas have an order of magnitude less intense cracking that primarily occurs at depths between 50 and 800 cm. This suggests that periglacial erosion may be concentrated in a narrow elevation range (corresponding to areas with a MAT between 0 and 2°C). At higher MATs ice growth is limited to very shallow depths. As MATs dip below zero, frost cracking intensity is reduced considerably resulting in a high and frozen condition. These results suggest that rocks with a fracture spacing of less than 400cm provide more sites for the nucleation and growth of segregation ice, and are therefore more susceptible to frost-induced bedrock weathering. To quantify the effect of ice

Debris-flow deposits and watershed erosion rates near southern Death Valley, CA, United States

USGS Publications Warehouse

Schmidt, K.M.; Menges, C.M.; ,

2003-01-01

Debris flows from the steep, granitic hillslopes of the Kingston Range, CA are commensurate in age with nearby fluvial deposits. Quaternary chronostratigraphic differentiation of debris-flow deposits is based upon time-dependent characteristics such as relative boulder strength, derived from Schmidt Hammer measurements, degree of surface desert varnish, pedogenesis, and vertical separation. Rock strength is highest for Holocene-aged boulders and decreases for Pleistocene-aged boulders weathering to grus. Volumes of age-stratified debris-flow deposits, constrained by deposit thickness above bedrock, GPS surveys, and geologic mapping, are greatest for Pleistocene deposits. Shallow landslide susceptibility, derived from a topographically based GIS model, in conjunction with deposit volumes produces watershed-scale erosion rates of ???2-47 mm ka-1, with time-averaged Holocene rates exceeding Pleistocene rates. ?? 2003 Millpress.

Regionalization of monthly rainfall erosivity patternsin Switzerland

NASA Astrophysics Data System (ADS)

Schmidt, Simon; Alewell, Christine; Panagos, Panos; Meusburger, Katrin

2016-10-01

One major controlling factor of water erosion is rainfall erosivity, which is quantified as the product of total storm energy and a maximum 30 min intensity (I30). Rainfall erosivity is often expressed as R-factor in soil erosion risk models like the Universal Soil Loss Equation (USLE) and its revised version (RUSLE). As rainfall erosivity is closely correlated with rainfall amount and intensity, the rainfall erosivity of Switzerland can be expected to have a regional characteristic and seasonal dynamic throughout the year. This intra-annual variability was mapped by a monthly modeling approach to assess simultaneously spatial and monthly patterns of rainfall erosivity. So far only national seasonal means and regional annual means exist for Switzerland. We used a network of 87 precipitation gauging stations with a 10 min temporal resolution to calculate long-term monthly mean R-factors. Stepwise generalized linear regression (GLM) and leave-one-out cross-validation (LOOCV) were used to select spatial covariates which explain the spatial and temporal patterns of the R-factor for each month across Switzerland. The monthly R-factor is mapped by summarizing the predicted R-factor of the regression equation and the corresponding residues of the regression, which are interpolated by ordinary kriging (regression-kriging). As spatial covariates, a variety of precipitation indicator data has been included such as snow depths, a combination product of hourly precipitation measurements and radar observations (CombiPrecip), daily Alpine precipitation (EURO4M-APGD), and monthly precipitation sums (RhiresM). Topographic parameters (elevation, slope) were also significant explanatory variables for single months. The comparison of the 12 monthly rainfall erosivity maps showed a distinct seasonality with the highest rainfall erosivity in summer (June, July, and August) influenced by intense rainfall events. Winter months have the lowest rainfall erosivity. A proportion

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.

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

Quantifying trail erosion and stream sedimentation with sediment tracers

Treesearch

Mark S. Riedel

2006-01-01

Abstract--The impacts of forest disturbance and roads on stream sedimentation have been rigorously investigated and documented. While historical research on turbidity and suspended sediments has been thorough, studies of stream bed sedimentation have typically relied on semi-quantitative measures such as embeddedness or marginal pool depth. To directly quantify the...

A probabilistic approach to modeling erosion for spatially-varied conditions

Treesearch

William J. Elliot; Peter R. Robichaud; C. D. Pannkuk

2001-01-01

In the years following a major forest disturbance, such as fire, the erosion rate is greatly influenced by variability in weather, in soil properties, and in spatial distribution. This paper presents a method to incorporate these variabilities into the erosion rate predicted by the Water Erosion Prediction Project model. It appears that it is not necessary to describe...

Exhumation of Basement-cored Uplifts: Example of the Kyrgyz Range Quantified with Apatite Fission-track Thermochronology

NASA Technical Reports Server (NTRS)

Sobel, Edward R.; Oskin, Michael; Burbank, Douglas; Mikolaichuk, Alexander

2005-01-01

The Kyrgyz Range, the northernmost portion of the Kyrgyzstan Tien Shan, displays topographic evidence for lateral propagation of surface uplift and exhumation. The highest and most deeply dissected segment lies in the center of the range. To the east, topography and relief decrease, and preserved remnants of a Cretaceous regional erosion surface imply minimal amounts of bedrock exhumation. The timing of exhumation of range segments defines the lateral propagation rate of the range-bounding reverse fault and quantifies the time and erosion depth needed to transform a mountain range from a juvenile to a mature morphology. New apatite fission-track (AFT) data from three transects from the eastern Kyrgyz Range, combined with published AFT data, demonstrate that the range has propagated over 110 km eastwards over the last 7-11 Myr. Based on the thermal and topographic evolutionary history, we present a model for a time-varying exhumation rate driven by rock uplift and changes in erodability and the time scale of geomorphic adjustment to surface uplift. Easily eroded, Cenozoic sedimentary rocks overlying resistant basement control early, rapid exhumation and slow surface upliftrates. As increasing amounts of resistant basement are exposed, exhumation rates decrease while surface uplift rates are sustained or increase, thereby growing topography. As the range becomes high enough to cause ice accumulation and develop steep river valleys, fluvial and glacial erosion become more powerful and exhumation rates once again increase. Independently determined range-noma1 shortening rates have also varied over time, suggesting a feedback between erosional efficiency and shortening rate.

Relative contributions of wind and water erosion to total soil loss and its effect on soil properties in sloping croplands of the Chinese Loess Plateau.

PubMed

Tuo, Dengfeng; Xu, Mingxiang; Gao, Guangyao

2018-08-15

Wind and water erosion are two dominant types of erosion that lead to soil and nutrient losses. Wind and water erosion may occur simultaneously to varying extents in semi-arid regions. The contributions of wind and water erosion to total erosion and their effects on soil quality, however, remains elusive. We used cesium-137 ( 137 Cs) inventories to estimate the total soil erosion and used the Revised Universal Soil Loss Equation (RUSLE) to quantify water erosion in sloping croplands. Wind erosion was estimated from the subtraction of the two. We also used 137 Cs inventories to calculate total soil erosion and validate the relationships of the soil quality and erosion at different slope aspects and positions. The results showed that wind erosion (1460tkm -2 a -1 ) on northwest-facing slope was responsible for approximately 39.7% of the total soil loss, and water erosion (2216tkm -2 a -1 ) accounted for approximately 60.3%. The erosion rates were 58.8% higher on northwest- than on southeast-facing slopes. Northwest-facing slopes had lower soil organic carbon, total nitrogen, clay, and silt contents than southeast-facing slopes, and thus, the 137 Cs inventories were lower, and the total soil erosions were higher on the northwest-facing slopes. The variations in soil physicochemical properties were related to total soil erosion. The lowest 137 Cs inventories and nutrient contents were recorded at the upper positions on the northwest-facing slopes due to the successive occurrence of more severe wind and water erosion at the same site. The results indicated that wind and water could accelerate the spatial variability of erosion rate and soil properties and cause serious decreases in the nutrient contents in sloping fields. Our research could help researchers develop soil strategies to reduce soil erosion according to the dominant erosion type when it occurs in a hilly agricultural area. Copyright © 2018 Elsevier B.V. All rights reserved.

Spatial distribution of erosion in the Hangay Mountains of Mongolia and implications for the development of epeirogenic topography

NASA Astrophysics Data System (ADS)

West, A.; Fox, M.; Walker, R. T.; Carter, A.; Watts, A. B.; Gantulga, B.

2012-12-01

Potential feedbacks between climate-driven erosion and the development of intra-continental topography have received relatively little attention, particularly compared to the significant efforts to understand the interplay of climate, erosion, and uplift in orogenic settings. But such links may be vital for understanding the topographic evolution of epeirogenic topography and for making inferences about geodynamic processes based on associated sedimentary and geomorphic signals. In this study, we consider the role of orographically-driven climate variability in shaping continental topography by focusing on the Hangay mountain range, a uplifted dome in central Mongolia. The work presented here is based on results from a topographic analysis of the Hangay, making use of the flat-topped peaks that effectively represent preserved remnants of a pre-erosional surface. We have determined the scale and distribution of erosion by recreating this pre-erosional surface and subtracting the present-day, dissected topography. Our results show that the extent of erosion correlates with spatial variation in mean annual precipitation, but not with the extent of total surface uplift. The morphology of the range reflects the higher, climate-driven fluvial erosion rates by northern rivers that receive higher precipitation when compared to the southern rivers, which have steeper relief as a result of the asymmetric main drainage divide. Overall asymmetry in inferred isostatic response to erosional unloading is not mirrored in asymmetry of total surface uplift, hinting at interaction between surface erosion and the forces sustaining topography. This has important implications for understanding the geodynamics of epeirogenic uplift. In addition to these main outcomes from our topographic analysis, we will also present preliminary findings from detrital thermochronology and cosmogenic analyses that help to pinpoint the location of erosion and provide a basis for quantifying rates.

Long-term predictive capability of erosion models

NASA Technical Reports Server (NTRS)

Veerabhadra, P.; Buckley, D. H.

1983-01-01

A brief overview of long-term cavitation and liquid impingement erosion and modeling methods proposed by different investigators, including the curve-fit approach is presented. A table was prepared to highlight the number of variables necessary for each model in order to compute the erosion-versus-time curves. A power law relation based on the average erosion rate is suggested which may solve several modeling problems.

Time-Dependent Erosion of Ion Optics

NASA Technical Reports Server (NTRS)

Wirz, Richard E.; Anderson, John R.; Katz, Ira; Goebel, Dan M.

2008-01-01

The accurate prediction of thruster life requires time-dependent erosion estimates for the ion optics assembly. Such information is critical to end-of-life mechanisms such as electron backstreaming. CEX2D was recently modified to handle time-dependent erosion, double ions, and multiple throttle conditions in a single run. The modified code is called "CEX2D-t". Comparisons of CEX2D-t results with LDT and ELT post-tests results show good agreement for both screen and accel grid erosion including important erosion features such as chamfering of the downstream end of the accel grid and reduced rate of accel grid aperture enlargement with time.

The effects of climate change and extreme wildfire events on runoff erosion over a mountain watershed

Treesearch

Mingliang Liu; Michael E. Barber; Keith A. Cherkauer; Pete Robichaud; Jennifer C. Adam

2016-01-01

Increases in wildfire occurrence and severity under an altered climate can substantially impact terrestrial ecosystems through enhancing runoff erosion. Improved prediction tools that provide high resolution spatial information are necessary for location-specific soil conservation and watershed management. However, quantifying the magnitude of soil erosion and...

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.

Degradation of the Mitchell River fluvial megafan by alluvial gully erosion increased by post-European land use change, Queensland, Australia

NASA Astrophysics Data System (ADS)

Shellberg, J. G.; Spencer, J.; Brooks, A. P.; Pietsch, T. J.

2016-08-01

Along low gradient rivers in northern Australia, there is widespread gully erosion into unconfined alluvial deposits of active and inactive floodplains. On the Mitchell River fluvial megafan in northern Queensland, river incision and fan-head trenching into Pleistocene and Holocene megafan units with sodic soils created the potential energy for a secondary cycle of erosion. In this study, rates of alluvial gully erosion into incipiently-unstable channel banks and/or pre-existing floodplain features were quantified to assess the influence of land use change following European settlement. Alluvial gully scarp retreat rates were quantified at 18 sites across the megafan using recent GPS surveys and historic air photos, demonstrating rapid increases in gully area of 1.2 to 10 times their 1949 values. Extrapolation of gully area growth trends backward in time suggested that the current widespread phase of gullying initiated between 1880 and 1950, which is post-European settlement. This is supported by young optically stimulated luminescence (OSL) dates of gully inset-floodplain deposits, LiDAR terrain analysis, historic explorer accounts of earlier gully types, and archival records of cattle numbers and land management. It is deduced that intense cattle grazing and associated disturbance concentrated in the riparian zones during the dry season promoted gully erosion in the wet season along steep banks, adjacent floodplain hollows and precursor gullies. This is a result of reduced native grass cover, increased physical disturbance of soils, and the concentration of water runoff along cattle tracks, in addition to fire regime modifications, episodic drought, and the establishment of exotic weed and grass species. Geomorphic processes operating over geologic time across the fluvial megafan predisposed the landscape to being pushed by land used change across an intrinsically close geomorphic threshold towards instability. The evolution of these alluvial gullies is discussed

Contribution of bank erosion to the sediment budget of a drained agricultural lowland catchment

NASA Astrophysics Data System (ADS)

Cerdan, Olivier; Foucher, Anthony; Vandromme, Rosalie; Salvador-Blanes, Sébastien; Gay, Aurore; Landemaine, Valentin; Evrard, Olivier

2017-04-01

Following the shift towards more intensive agriculture in cultivated lowlands in Europe, field sizes have increased and stream valley meanderings have been removed and realigned along new straight field borders. These modifications have led to profound alterations of the hydromorphology of the streams. To test the impact of these modifications, the long-term and current volumes of sediment originating from stream banks were calculated as they provided potential sources of sediment in a large pond located at the outlet of a small agricultural lowland basin under strong anthropogenic pressure. Bank erosion was measured using several methodologies, i) over a short period using a set of erosion pins along a small stream (1400 m long) to quantify the material exported during a single winter season (2012/2013); ii) over the last 69 years using an original approach involving the comparison of a compilation of three-dimensional historical stream redesign plans from 1944 vs. new measurements conducted in 2013 (DGPS and LiDAR data); iii) over several decades by using tracers (137Cs) that can differentiate between surface and subsoil erosion. At the catchment scale, total sediment exports were estimated from 1945 to 2013 combining seismic imagery and core dating in the lake. Sediment exports decreased with time, from 300 t. km-2.yr-between 1954 and 1980 to 95 t. km-2.yr-1 between 1980 and 2013. Today, erosion rates recorded at the outlet of the catchment vary between 90-102 t.km-2.yr-1. Therefore, the order of magnitude of the mean export rate is approximately 180 t. km-2.yr-1 for the last 70 years. The contribution of channel banks to this sediment export was the highest ( 30%) between 1954 and 1980 when the ditches were constructed. For the entire period since the landscape modification, the contribution of bank erosion is lower but still reaches 20%. Bank erosion can therefore be considered as a significant contributor to the sediment budget of the lowland catchments that

Polymers Erosion and Contamination Experiment Being Developed

NASA Technical Reports Server (NTRS)

deGroh, Kim K.; Banks, Bruce A.; Barney-Barton, Elyse A.; Sechkar, Edward; Hunt, Patricia

1999-01-01

The Polymers Erosion and Contamination Experiment (PEACE) is currently being developed at the NASA Lewis Research Center by the Electro-Physics Branch in conjunction with students and faculty from Hathaway Brown School in Cleveland. The experiment is a Get Away Special Canister shuttle flight experiment sponsored by the American Chemical Society. The two goals of this experiment are (1) to measure ram atomic oxygen erosion rates of approximately 40 polymers that have potential use in space applications and (2) to validate a method for identifying sources of silicone contamination that occur in the shuttle bay. Equipment to be used in this flight experiment is shown in the schematic diagram. Spacecraft materials subjected to attack by atomic oxygen in the space environment experience significant degradation over the span of a typical mission. Therefore, learning the rates of atomic oxygen erosion of a wide variety of polymers would be of great benefit to future missions. PEACE will use two independent techniques to determine the atomic oxygen erosion rates of polymers. Large (1-in.-diameter) samples will be used for obtaining mass loss. Preflight and postflight dehydrated masses will be obtained, and the mass lost during flight will be determined. Small (0.5-in.-diameter) samples will be protected with isolated particles (such as NaCl crystals) and then exposed to the space environment. After flight, the protective particles will be removed (washed off) and atomic force microscopy (AFM) will be used to measure the erosion depth from protected mesas. Erosion depth measurements are more sensitive than traditional mass measurements and are very useful for materials with low erosion yields or with very low fluence missions.

Leveraging Distant Relatedness to Quantify Human Mutation and Gene-Conversion Rates

PubMed Central

Palamara, Pier Francesco; Francioli, Laurent C.; Wilton, Peter R.; Genovese, Giulio; Gusev, Alexander; Finucane, Hilary K.; Sankararaman, Sriram; Sunyaev, Shamil R.; de Bakker, Paul I.W.; Wakeley, John; Pe’er, Itsik; Price, Alkes L.

2015-01-01

The rate at which human genomes mutate is a central biological parameter that has many implications for our ability to understand demographic and evolutionary phenomena. We present a method for inferring mutation and gene-conversion rates by using the number of sequence differences observed in identical-by-descent (IBD) segments together with a reconstructed model of recent population-size history. This approach is robust to, and can quantify, the presence of substantial genotyping error, as validated in coalescent simulations. We applied the method to 498 trio-phased sequenced Dutch individuals and inferred a point mutation rate of 1.66 × 10−8 per base per generation and a rate of 1.26 × 10−9 for <20 bp indels. By quantifying how estimates varied as a function of allele frequency, we inferred the probability that a site is involved in non-crossover gene conversion as 5.99 × 10−6. We found that recombination does not have observable mutagenic effects after gene conversion is accounted for and that local gene-conversion rates reflect recombination rates. We detected a strong enrichment of recent deleterious variation among mismatching variants found within IBD regions and observed summary statistics of local sharing of IBD segments to closely match previously proposed metrics of background selection; however, we found no significant effects of selection on our mutation-rate estimates. We detected no evidence of strong variation of mutation rates in a number of genomic annotations obtained from several recent studies. Our analysis suggests that a mutation-rate estimate higher than that reported by recent pedigree-based studies should be adopted in the context of DNA-based demographic reconstruction. PMID:26581902

Time effect of erosion by solid particle impingement on ductile materials

NASA Technical Reports Server (NTRS)

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

1983-01-01

Erosion and morphological studies of several metals and alloys eroded by normal impingement jets of spherical glass beads and angular crushed-glass erodent particles were conducted. Erosion morphology (the width, depth, and width-depth ratio of the pit) was studied in order to fully investigate the effect of time on erosion rate. The eroded surfaces were studied with a scanning electron microscope, and surface profiles were measured with a profilometer. A large amount of experimental data reported in the literature was also analyzed in order to understand the effect of variables such as the type of device, the erodent particle size and shape, the impact velocity, and the abrasive charge on erosion-rate-versus-time curves. In the present experiments the pit-width-versus-time or pit-depth-versus-time curves were similar to erosion-versus-time curves for glass-bead impingement. The pit-depth-rate-versus-time curves were similar to erosion-rate-versus-time curves for crushed-glass impingement. Analysis of experimental data with two forms of glass resulted in four types of erosion-rate-versus-time curves: (1) incubation, acceleration, and steady-state periods (type I), (2) incubation, acceleration, deceleration, and steady-state periods (type III), (3) incubation, acceleration, peak rate, and deceleration periods (type IV), and (4) incubation, acceleration, steady-state, and deceleration periods (type V).

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.

Using (1)(0)Be cosmogenic isotopes to estimate erosion rates and landscape changes during the Plio-Pleistocene in the Cradle of Humankind, South Africa.

PubMed

Dirks, Paul H G M; Placzek, Christa J; Fink, David; Dosseto, Anthony; Roberts, Eric

2016-07-01

Concentrations of cosmogenic (10)Be, measured in quartz from chert and river sediment around the Cradle of Humankind (CoH), are used to determine basin-averaged erosion rates and estimate incision rates for local river valleys. This study focusses on the catchment area that hosts Malapa cave with Australopithecus sediba, in order to compare regional versus localized erosion rates, and better constrain the timing of cave formation and fossil entrapment. Basin-averaged erosion rates for six sub-catchments draining the CoH show a narrow range (3.00 ± 0.28 to 4.15 ± 0.37 m/Mega-annum [Ma]; ±1σ) regardless of catchment size or underlying geology; e.g. the sub-catchment with Malapa Cave (3 km(2)) underlain by dolomite erodes at the same rate (3.30 ± 0.30 m/Ma) as the upper Skeerpoort River catchment (87 km(2)) underlain by shale, chert and conglomerate (3.23 ± 0.30 m/Ma). Likewise, the Skeerpoort River catchment (147 km(2)) draining the northern CoH erodes at a rate (3.00 ± 0.28 m/Ma) similar to the Bloubank-Crocodile River catchment (627 km(2)) that drains the southern CoH (at 3.62 ± 0.33 to 4.15 ± 0.37 m/Ma). Dolomite- and siliciclastic-dominated catchments erode at similar rates, consistent with physical weathering as the rate controlling process, and a relatively dry climate in more recent times. Erosion resistant chert dykes along the Grootvleispruit River below Malapa yield an incision rate of ∼8 m/Ma at steady-state erosion rates for chert of 0.86 ± 0.54 m/Ma. Results provide better palaeo-depth estimates for Malapa Cave of 7-16 m at the time of deposition of A. sediba. Low basin-averaged erosion rates and concave river profiles indicate that the landscape across the CoH is old, and eroding slowly; i.e. the physical character of the landscape changed little in the last 3-4 Ma, and dolomite was exposed on surface probably well into the Miocene. The apparent absence of early Pliocene- or Miocene-aged cave deposits and

Predicting the Rate of River Bank Erosion Caused by Large Wood Log

NASA Astrophysics Data System (ADS)

Zhang, N.; Rutherfurd, I.; Ghisalberti, M.

2016-12-01

When a single tree falls into a river channel, flow is deflected and accelerated between the tree roots and the bank face, increasing shear stress and scouring the bank. The scallop shaped erosion increases the diversity of the channel morphology, but also causes concern for adjacent landholders. Concern about increased bank erosion is one of the main reasons for large wood to still be removed from channels in SE Australia. Further, the hydraulic effect of many logs in the channel can reduce overall bank erosion rates. Although both phenomena have been described before, this research develops a hydraulic model that estimates their magnitude, and tests and calibrates this model with flume and field measurements, with logs with various configurations and sizes. Specifically, the model estimates the change in excess shear stress on the bank associated . The model addresses the effect of the log angle, distance from bank, and log size and flow condition by solving the mass continuity and energy conservation between the cross section at the approaching flow and contracted flow. Then, we evaluate our model against flume experiment preformed with semi-realistic log models to represent logs in different sizes and decay stages by comparing the measured and simulated velocity increase in the gap between the log and the bank. The log angle, distance from bank, and flow condition are systemically varied for each log model during the experiment. Final, the calibrated model is compared with the field data collected in anabranching channels of Murray River in SE Australia where there are abundant instream logs and regulated and consistent high flow for irrigation. Preliminary results suggest that a log can significantly increase the shear stress on the bank, especially when it positions perpendicular to the flow. The shear stress increases with the log angle in a rising curve (The log angle is the angle between log trunk and flow direction. 0o means log is parallel to flow with

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.

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

Dynamic Analysis of Soil Erosion in Songhua River Watershed

NASA Astrophysics Data System (ADS)

Zhang, Yujuan; Li, Xiuhai; Wang, Qiang; Liu, Jiang; Liang, Xin; Li, Dan; Ni, Chundi; Liu, Yan

2018-01-01

In this paper, based on RS and GIS technology and Revised Universal Soil Loss Equation (RUSLE), the soil erosion dynamic changes during the two periods of 1990 and 2010 in Bin County was analyzed by using the Landsat TM data of the two periods, so as to reveal the soil erosion spatial distribution pattern and spatial and temporal dynamic evolution rule in the region. The results showed that: the overall patterns of soil erosion were basically the same in both periods, mainly featuring slight erosion and mild erosion, with the area proportions of 80.68% and 74.71% respectively. The slight and extremely intensive erosion changing rates showed a narrowing trend; mild, moderate and intensive erosion was increasing, with a trend of increased soil erosion; mild and intensive erosion were developing towards moderate erosion and moderate and extremely intensive erosion were progressing towards intensive erosion.

Synergistic erosion/corrosion of superalloys in PFB coal combustor effluent

NASA Technical Reports Server (NTRS)

Benford, S. M.; Zellars, G. R.; Lowell, C. E.

1981-01-01

Two Ni-based superalloys were exposed to the high velocity effluent of a pressurized fluidized bed coal combustor. Targets were 15 cm diameter rotors operating at 40,000 rpm and small flat plate specimens. Above an erosion rate threshold, the targets were eroded to bare metal. The presence of accelerated oxidation at lower erosion rates suggests erosion/corrosion synergism. Various mechanisms which may contribute to the observed oxide growth enhancement include erosive removal of protective oxide layers, oxide and subsurface cracking, and chemical interaction with sulfur in the gas and deposits through damaged surface layers.

Spatial and temporal assessment of back-barrier erosion on Cumberland Island National Seashore, Georgia, 2011–2013

USGS Publications Warehouse

Calhoun, Daniel L.; Riley, Jeffrey W.

2016-07-15

Much research has been conducted to better understand erosion and accretion processes for the seaward zones of coastal barrier islands; however, at Cumberland Island National Seashore, Georgia, the greater management concern is the effect that erosion is having on the resources of the island’s western shoreline, or the back barrier. Catastrophic slumping and regular rates of erosion greater than 1 meter per year threaten important habitat, historical and pre-historical resources, and modern infrastructure on the island. Prior research has helped National Park Service (NPS) staff identify the most severe and vulnerable areas, but in order to develop effective management actions, information is needed on what forces and conditions cause erosion. To this end, the U.S. Geological Survey, in cooperation with the NPS, conducted two longitudinal surveys, one each at the beginning and end of the approximately year-long monitoring period from late 2011 to early 2013, along five selected segments of the back barrier of the Cumberland Island National Seashore. Monitoring stations were constructed at four of these locations that had previously been identified as erosional hotspots. The magnitude of erosion at each location was quantified to determine the relative influence of causative agents. Results indicate that erosion is, in general, highly variable within and among these segments of the Cumberland Island National Seashore’s back barrier. Observed erosion ranged from a maximum of 2.5 meters of bluff-line retreat to some areas that exhibited no net erosion over the 1-year study period. In terms of timing of erosion, three of the four sites were primarily affected by punctuated erosional events that were coincident with above-average high tides and elevated wind speeds. The fourth site exhibited steady, low-magnitude retreat throughout the study period. While it is difficult to precisely subscribe certain amounts of erosion to specific agents, this study provides

Simulation of erosion by a particulate airflow through a ventilator

NASA Astrophysics Data System (ADS)

Ghenaiet, A.

2015-08-01

Particulate flows are a serious problem in air ventilation systems, leading to erosion of rotor blades and aerodynamic performance degradation. This paper presents the numerical results of sand particle trajectories and erosion patterns in an axial ventilator and the subsequent blade deterioration. The flow field was solved separately by using the code CFX- TASCflow. The Lagrangian approach for the solid particles tracking implemented in our inhouse code considers particle and eddy interaction, particle size distribution, particle rebounds and near walls effects. The assessment of erosion wear is based on the impact frequency and local values of erosion rate. Particle trajectories and erosion simulation revealed distinctive zones of impacts with high rates of erosion mainly on the blade pressure side, whereas the suction side is eroded around the leading edge.

The null hypothesis: steady rates of erosion, weathering and sediment accumulation during Late Cenozoic mountain uplift and glaciation

NASA Astrophysics Data System (ADS)

Willenbring, J. K.; Jerolmack, D. J.

2015-12-01

At the largest time and space scales, the pace of erosion and chemical weathering is determined by tectonic uplift rates. Deviations from this equilibrium condition arise from the transient response of landscape denudation to climatic and tectonic perturbations, and may be long lived. We posit that the constraint of mass balance, however, makes it unlikely that such disequilibrium persists at the global scale over millions of years, as has been proposed for late Cenozoic erosion. To support this contention, we synthesize existing data for weathering fluxes, global sedimentation rates, sediment yields and tectonic motions. The records show a remarkable constancy in the pace of Earth-surface evolution over the last 10 million years. These findings provide strong support for the null hypothesis; that global rates of landscape change have remained constant over the last ten million years, despite global climate change and massive mountain building events. Two important implications are: (1) global climate change may not change global denudation rates, because the nature and sign of landscape responses are varied; and (2) tectonic and climatic perturbations are accommodated in the long term by changes in landscape form. This work undermines the hypothesis that increased weathering due to late Cenozoic mountain building or climate change was the primary agent for a decrease in global temperatures.

Tectonic control of erosion in the southern Central Andes

NASA Astrophysics Data System (ADS)

Val, Pedro; Venerdini, Agostina L.; Ouimet, William; Alvarado, Patricia; Hoke, Gregory D.

2018-01-01

Landscape evolution modeling and global compilations of exhumation data indicate that a wetter climate, mainly through orographic rainfall, can govern the spatial distribution of erosion rates and crustal strain across an orogenic wedge. However, detecting this link is not straightforward since these relationships can be modulated by tectonic forcing and/or obscured by heavy-tailed frequencies of catchment discharge. This study combines new and published along-strike average rates of catchment erosion constrained by 10Be and river-gauge data in the Central Andes between 28°S and 36°S. These data reveal a nearly identical latitudinal pattern in erosion rates on both sides of the range, reaching a maximum of 0.27 mm/a near 34°S. Collectively, data on topographic and fluvial relief, variability of rainfall and discharge, and crustal seismicity suggest that the along-strike pattern of erosion rates in the southern Central Andes is largely independent of climate, but closely relates to the N-S distribution of shallow crustal seismicity and diachronous surface uplift. The consistently high erosion rates on either side of the orogen near 34°S imply that climate plays a secondary role in the mass flux through an orogenic wedge where the perturbation to base level is similar on both sides.

Erosion associated with cable and tractor logging in northwestern California

Treesearch

R. M. Rice; P. A. Datzman

1981-01-01

Abstract - Erosion and site conditions were measured at 102 logged plots in northwestern California. Erosion averaged 26.8 m 3 /ha. A log-normal distribution was a better fit to the data. The antilog of the mean of the logarithms of erosion was 3.2 m 3 /ha. The Coast District Erosion Hazard Rating was a poor predictor of erosion related to logging. In a new equation...

A sediment budget from a glaciated catchment: reconciling subglacial and periglacial erosion on short timescales

NASA Astrophysics Data System (ADS)

Delaney, Ian; Gindraux, Saskia; Weidmann, Yvo; Bauder, Andreas

2017-04-01

Glaciated catchments are known to expel great amounts of sediment, particularly during periods of climatic perturbation. Sediment in these catchments either originates subglacially, where it is eroded by pressurized water below the glacier, or from periglacial areas, which are commonly comprised of easily erodible, unconsolidated material no longer buttressed and held in place by ice. To better forecast sediment dynamics and erosion rates in to the future, contributions of subglacial and periglacial sediment must be quantified, and the processes controlling erosion in these respective sources described. To determine the relative contributions of these sources, we examine the Griesgletscher catchment in the Swiss Alps. Its rather simplistic geometry, as well as, the presence of a proglacial reservoir that serves as a sediment trap, provides an unusually constrained environment to directly measure sediment sources and sinks in the catchment. Subtraction of three digital elevation models created from structure-from-motion and photogrammetric techniques over a one year period, from October 2015 to October 2016, were used to measured sediment flux from the proglacial area. Furthermore, comparison of bathymetries collected from the proglacial reservoir in fall of 2015 and 2016 determined total sediment flux from the entire catchment over this 10 km2time period. Data from a turbidity meter, installed below the reservoir outflow, suggest that negligible amounts of sediment leave the reservoir. Thus comparison of reservoir bathymetry and sediment fluxes from the proglacial area give estimates of the relative contribution of proglacial and subglacial sediment erosion to total catchment sedimentation. Analysis of this data suggest that while the proglacial area experiences a greater erosion rate, it is likely more sediment originates subglacially. As proglacial areas are expected to grow in area and partially stabilize, and glacial areas are predicted to shrink and possibly

Erosion of iron-chromium alloys by glass particles

NASA Technical Reports Server (NTRS)

Salik, J.; Buckley, D. H.

1984-01-01

The material loss upon erosion was measured for several iron-chromium alloys. Two types of erodent material were used: spherical glass beads and sharp particles of crushed glass. For erosion with glass beads the erosion resistance (defined as the reciprocal of material loss rate) was linearly dependent on hardness. This is in accordance with the erosion behavior of pure metals, but contrary to the erosion behavior of alloys of constant composition that were subjected to different heat treatments. For erosion with crushed glass, however, no correlation existed between hardness and erosion resistance. Instead, the erosion resistance depended on alloy composition rather than on hardness and increased with the chromium content of the alloy. The difference in erosion behavior for the two types of erodent particles suggested that two different material removal mechanisms were involved. This was confirmed by SEM micrographs of the eroded surfaces, which showed that for erosion with glass beads the mechanism of material removal was deformation-induced flaking of surface layers, or peening, whereas for erosion with crushed glass it was cutting or chopping.

Erosion of water-based fracturing fluid containing particles in a sudden contraction of horizontal pipe

NASA Astrophysics Data System (ADS)

Cheng, Jiarui; Cao, Yinping; Dou, Yihua; Li, Zhen

2017-10-01

A lab experiment was carried out to study the effects of pipe flow rate, particle concentration and pipe inner diameter ratio on proppant erosion of the reducing wall in hydraulic fracturing. The results show that the erosion rate and erosion distribution are different not only in radial direction but also in circumferential direction of the sample. The upper part of sample always has a minimum erosion rate and erosion area. Besides, the erosion rate of reducing wall is most affected by fluid flow velocity, and the erosion area is most sensitive to the change in the diameter ratio. Meanwhile, the erosion rate of reducing wall in crosslinked fracturing fluid is mainly determined by the fluid flowing state due to the high viscosity of the liquid. In general, the increase in flow velocity and diameter ratio not only cause the expansion of erosion-affected flow region in sudden contraction section, but also lead to more particles impact the wall.

Detection of soil erosion within pinyon-juniper woodlands using Thematic Mapper (TM) data

NASA Technical Reports Server (NTRS)

Price, Kevin P.

1993-01-01

Multispectral measurements collected by Landsat Thematic Mapper (TM) were correlated with field measurements, direct soil loss estimates, and Universal Soil Loss Equation (USLE) estimates to determine the sensitivity of TM data to varying degrees of soil erosion in pinyon-juniper woodland in central Utah. TM data were also evaluated as a predictor of the USLE Crop Management C factor for pinyon-juniper woodlands. TM spectral data were consistently better predictors of soil erosion factors than any combination of field factors. TM data were more sensitive to vegetation variations than the USLE C factor. USLE estimates showed low annual rates of erosion which varied little among the study sites. Direct measurements of rate of soil loss using the SEDIMENT (Soil Erosion DIrect measureMENT) technique, indicated high and varying rates of soil loss among the sites since tree establishment. Erosion estimates from the USLE and SEDIMENT methods suggest that erosion rates have been severe in the past, but because significant amounts of soil have already been eroded, and the surface is now armored by rock debris, present erosion rates are lower. Indicators of accelerated erosion were still present on all sites, however, suggesting that the USLE underestimated erosion within the study area.

Validation of Water Erosion Prediction Project (WEPP) model for low-volume forest roads

Treesearch

William Elliot; R. B. Foltz; Charlie Luce

1995-01-01

Erosion rates of recently graded nongravel forest roads were measured under rainfall simulation on five different soils. The erosion rates observed on 24 forest road erosion plots were compared with values predicted by the Water Erosion Prediction Project (WEPP) Model, Version 93.1. Hydraulic conductivity and soil erodibility values were predicted from methods...

Comparison of the soil losses from (7)Be measurements and the monitoring data by erosion pins and runoff plots in the Three Gorges Reservoir region, China.

PubMed

Shi, Zhonglin; Wen, Anbang; Zhang, Xinbao; Yan, Dongchun

2011-10-01

The potential for using (7)Be measurements to document soil redistribution associated with a heavy rainfall was estimated using (7)Be method on a bare purple soil plot in the Three Gorges Reservoir region of China. The results were compared with direct measurement from traditional approaches of erosion pins and runoff plots. The study shows that estimation of soil losses from (7)Be are comparable with the monitoring results provided by erosion pins and runoff plots, and are also in agreement with the existing knowledge provided by 137Cs measurements. The results obtained from this study demonstrated the potential for using (7)Be technique to quantify short-term erosion rates in these areas. Copyright © 2011 Elsevier Ltd. All rights reserved.

Legacy effects of colonial millponds on floodplain sedimentation, bank erosion, and channel morphology, MID-Atlantic, USA

USGS Publications Warehouse

Schenk, E.R.; Hupp, C.R.

2009-01-01

Many rivers and streams of the Mid-Atlantic Region, United States (U.S.) have been altered by postcolonial floodplain sedimentation (legacy sediment) associated with numerous milldams. Little Conestoga Creek, Pennsylvania, a tributary to the Susquehanna River and the Chesapeake Bay, is one of these streams. Floodplain sedimentation rates, bank erosion rates, and channel morphology were measured annually during 2004-2007 at five sites along a 28-km length of Little Conestoga Creek with nine colonial era milldams (one dam was still in place in 2007). This study was part of a larger cooperative effort to quantify floodplain sedimentation, bank erosion, and channel morphology in a high sediment yielding region of the Chesapeake Bay watershed. Data from the five sites were used to estimate the annual volume and mass of sediment stored on the floodplain and eroded from the banks for 14 segments along the 28-km length of creek. A bank and floodplain reach based sediment budget (sediment budget) was constructed for the 28 km by summing the net volume of sediment deposited and eroded from each segment. Mean floodplain sedimentation rates for Little Conestoga Creek were variable, with erosion at one upstream site (-5 mm/year) to deposition at the other four sites (highest = 11 mm/year) despite over a meter of floodplain aggradation from postcolonial sedimentation. Mean bank erosion rates range between 29 and 163 mm/year among the five sites. Bank height increased 1 m for every 10.6 m of channel width, from upstream to downstream (R2 = 0.79, p < 0.0001) resulting in progressively lowered hydraulic connectivity between the channel and the floodplain. Floodplain sedimentation and bank erosion rates also appear to be affected by the proximity of the segments to one existing milldam, which promotes deposition upstream and scouring downstream. The floodplain and bank along the 28-km reach produced a net mean sediment loss of 5,634 Mg/year for 2004-2007, indicating that bank

A model for multiple-drop-impact erosion of brittle solids

NASA Technical Reports Server (NTRS)

Engel, O. G.

1971-01-01

A statistical model for the multiple-drop-impact erosion of brittle solids was developed. An equation for calculating the rate of erosion is given. The development is not complete since two quantities that are needed to calculate the rate of erosion with use of the equation must be assessed from experimental data. A partial test of the equation shows that it gives results that are in good agreement with experimental observation.

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.

Plio-Pleistocene paleo-erosion rates as a recorder of orographic barrier uplift in the NW-Argentine Andes (Humahuaca Basin)

NASA Astrophysics Data System (ADS)

Pingel, Heiko; Schildgen, Taylor; Wittmann, Hella

2017-04-01

As an integral part of the Eastern Cordillera, the intermontane Humahuaca Basin in the NW Argentine Andes is located in transition between the arid and internally drained Puna Plateau to the west and the humid broken foreland to the east. In combination with moisture-bearing air masses sourced in the Atlantic Ocean and the Amazon Basin, the present-day topographic gradient of the eastern Andean margin comprises an efficient orographic barrier that results in a strong precipitation gradient, with rainfall of more than 2,000 mm/a along the eastern flanks and <200 mm/a on the plateau. Ultimately, variable moisture availability affects surface processes, such as fluvial erosion and transport of eroded material, with decreasing erosion rates towards the orogenic hinterland. Paleoenvironmental reconstructions of the Humahuaca Basin suggest that this region became disconnected from the foreland during the Mio-Pliocene by the growth of fault-bounded mountain ranges. This led to an increase in accommodation space and enabled the trapping of largely fluvial, late Miocene to Quaternary basin filling units. Subsequently, the basin was uplifted and internally deformed. Fossil records, sedimentologic evidence, and stable-isotopes (δD from volcanic glass) moreover imply that the re-routing of the fluvial network, an initial increase in precipitation, and, as the windward ranges attained threshold elevations to incoming moisture, reduced moisture availability by ca. 3 Ma, were all a consequence of the Mio-Pliocene uplift. In this study, we present first results of terrestrial cosmogenic nuclide-derived paleo-erosion rates from quartz-bearing fluvial sands and gravels of known stratigraphic age. In most cases, the age control is based on previously published U-Pb zircon data of intercalated volcanic ash deposits, but also utilizes new OSL and AMS14C ages. A reassessment of the sediment-accumulation history of the basin highlights important changes of the depositional system

Nozzle erosion characterization and minimization for high-pressure rocket motor applications

NASA Astrophysics Data System (ADS)

Evans, Brian

Understanding of the processes that cause nozzle throat erosion and developing methods for mitigation of erosion rate can allow higher operating pressures for advanced rocket motors. However, erosion of the nozzle throat region, which is a strong function of operating pressure, must be controlled to realize the performance gains of higher operating pressures. The objective of this work was the study the nozzle erosion rates at a broad range of pressures from 7 to 34.5 MPa (1,000 to 5,000 psia) using two different rocket motors. The first is an instrumented solidpropellant motor (ISPM), which uses two baseline solid propellants; one is a non-metallized propellant called Propellant S and the other is a metallized propellant called Propellant M. The second test rig is a non-metallized solid-propellant rocket motor simulator (RMS). The RMS is a gas rocket with the ability to vary the combustion-product species composition by systematically varying the flow rates of gaseous reactants. Several reactant mixtures were utilized in the study to determine the relative importance of different oxidizing species (such as H2O, OH, and CO2). Both test rigs are equipped with a windowed nozzle section for real-time X-ray radiography diagnostics of the instantaneous throat variations for deducing the instantaneous erosion rates. The nozzle test section for both motors can also incorporate a nozzle boundary-layer control system (NBLCS) as a means of nozzle erosion mitigation. The effectiveness of the NBLCS at preventing nozzle throat erosion was demonstrated for both the RMS and the ISPM motors at chamber pressures up to 34 MPa (4930 psia). All tests conducted with the NBLCS showed signs of coning of the propellant surface, leading to increased mass burning rate and resultant chamber pressure. Two correlations were developed for the nozzle erosion rates from solid propellant testing, one for metallized propellant and one for non-metallized propellants. The non-metallized propellant

Effect of flow velocity on erosion-corrosion behaviour of QSn6 alloy

NASA Astrophysics Data System (ADS)

Huang, Weijiu; Zhou, Yongtao; Wang, Zhenguo; Li, Zhijun; Zheng, Ziqing

2018-05-01

The erosion-corrosion behaviour of QSn6 alloy used as propellers in marine environment was evaluated by erosion-corrosion experiments with/without cathodic protection, electrochemical tests and scanning electron microscope (SEM) observations. The analysis was focused on the effect of flow velocity. The dynamic polarization curves showed that the corrosion rate of the QSn6 alloy increased as the flow velocity increased, due to the protective surface film removal at higher velocities. The lowest corrosion current densities of 1.26 × 10‑4 A cm‑2 was obtained at the flow velocity of 7 m s‑1. Because of the higher particle kinetic energies at higher flow velocity, the mass loss rate of the QSn6 alloy increased as the flow velocity increased. The mass loss rate with cathodic protection was lower than that without cathodic protection under the same conditions. Also, the lowest mass loss rate of 0.7 g m‑2 · h‑1 was acquired at the flow velocity of 7 m s‑1 with cathodic protection. However, the increase rate of corrosion rate and mass loss were decreased with increasing the flow velocity. Through observation the SEM morphologies of the worn surfaces, the main wear mechanism was ploughing with/without cathodic protection. The removal rates of the QSn6 alloy increased as the flow velocity increased in both pure erosion and erosion-corrosion, whereas the erosion and corrosion intensified each other. At the flow velocity of 7 m s‑1, the synergy rate (ΔW) exceeded by 5 times the erosion rate (Wwear). Through establishment and observation the erosion-corrosion mechanism map, the erosion-corrosion was the dominant regime in the study due to the contribution of erosion on the mass loss rate exceeded the corrosion contribution. The QSn6 alloy with cathodic protection is feasible as propellers, there are higher security at lower flow velocity, such as the flow velocity of 7 m s‑1 in the paper.

A study of cathode erosion in high power arcjets

NASA Astrophysics Data System (ADS)

Harris, William Jackson, III

Cathode erosion continues to be one of the predominant technology concerns for high power arcjets. This study will show that cathode erosion in these devices is significantly affected by several mitigating factors, including propellant composition, propellant flowrate, current level, cathode material, and power supply current ripple. In a series of 50-hour and 100-hour long duration experiments, using a water-cooled 30 kilowatt laboratory arcjet, variations in the steady-state cathode erosion rate were characterized for each of these factors using nitrogen propellant at a fixed arc current of 250 Amperes. A complementary series of measurements was made using hydrogen propellant at an arc current of 100 Amperes. The cold cathode erosion rate was also differentiated from the steady-state cathode erosion rate in a series of multi-start cathode erosion experiments. Results of these measurements are presented, along with an analysis of the significant effects of current ripple on arcjet cathode erosion. As part of this study, over a dozen refractory cathode materials were evaluated to measure their resistance to arcjet cathode erosion. Among the materials tested were W-ThO2(1%, 2%, 4%), poly and mono-crystalline W, W-LaB6, W-La2O3, W-BaO2, W-BaCaAl2O4, W-Y2O3, and ZrB2. Based on these measurements, several critical material properties were identified, such work function, density, porosity, melting point, and evaporation rate. While the majority of the materials failed to outperform traditional W-ThO2, these experimental results are used to develop a parametric model of the arcjet cathode physics. The results of this model, and the results of a finite-element thermal analysis of the arcjet cathode, are presented to better explain the relative performance of the materials tested.

Saliva composition in three selected groups with normal stimulated salivary flow rates, but yet major differences in caries experience and dental erosion.

PubMed

Bardow, Allan; Lykkeaa, Joan; Qvist, Vibeke; Ekstrand, Kim; Twetman, Svante; Fiehn, Niels-Erik

2014-08-01

It was hypothesized that, by comparing matched subjects with major differences in these dental diseases, but yet normal saliva flow rates, it would be possible to obtain data on the effect of saliva composition on dental disease isolated from the effect of the flow rate. Thus, the aim of the study was to compare the major physicochemical characteristics of stimulated whole saliva in three groups of 85 subjects, each with normal saliva flow rates and at least 24 remaining teeth. A group with very little dental disease (healthy), a group with dental erosion (erosion) and a group with very high caries experience (caries) were chosen. Furthermore, the aim was to determine whether differences among groups could also be found on an individual level. Although it was not possible to retrieve three groups whose members were completely identical, the present study points in the direction that, on a group level, subjects with very little dental disease seemed to have a more favorable physicochemical saliva composition with respect to higher calcium, phosphate, bicarbonate, pH, degree of saturation with respect to hydroxyapatite and a lower critical pH (p < 0.05 or less). However, on an individual level the explanatory power for the saliva composition was only 10% for caries experience and only 11% for dental erosion (p < 0.001). The compositional analyses performed in this study on stimulated whole saliva, including major physicochemical characteristics of saliva, will most likely have little predictive value for future dental caries and erosion in single individuals.

Heart rate measurement as a tool to quantify sedentary behavior.

PubMed

Åkerberg, Anna; Koshmak, Gregory; Johansson, Anders; Lindén, Maria

2015-01-01

Sedentary work is very common today. The aim of this pilot study was to attempt to differentiate between typical work situations and to investigate the possibility to break sedentary behavior, based on physiological measurement among office workers. Ten test persons used one heart rate based activity monitor (Linkura), one pulse oximeter device (Wrist) and one movement based activity wristband (Fitbit Flex), in different working situations. The results showed that both heart rate devices, Linkura and Wrist, were able to detect differences in heart rate between the different working situations (resting, sitting, standing, slow walk and medium fast walk). The movement based device, Fitbit Flex, was only able to separate differences in steps between slow walk and medium fast walk. It can be concluded that heart rate measurement is a promising tool for quantifying and separating different working situations, such as sitting, standing and walking.

"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)...

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.

Constraining the fault slip rate using morphology of normal fault footwalls: insights from analog and numerical models (Invited)

NASA Astrophysics Data System (ADS)

Strak, V.; Dominguez, S.; Petit, C.; Meyer, B.; Loget, N.

2013-12-01

Relief evolution in active tectonic areas is controlled by the interactions between tectonics and surface processes (erosion, transport and sedimentation). These interactions lead to the formation of geomorphologic markers that remain stable during the equilibrium reached in the long-term between tectonics and erosion. In regions experiencing active extension, drainage basins and faceted spurs (triangular facets) are such long-lived morphologic markers and they can help in quantifying the competing effects between tectonics, erosion and sedimentation. We performed analog and numerical models simulating the morphologic evolution of a mountain range bounded by a normal fault. In each approach we imposed identical initial conditions. We carried out several models by varying the fault slip rate (V) and keeping a constant rainfall rate allowing us to study the effect of V on morphology. Both approaches highlight the main control of V on the topographic evolution of the footwall. The experimental approach shows that V controls erosion rates (incision rate, erosion rate of slopes and regressive erosion rate) and possibly the height of triangular facets. This approach indicates likewise that the parameter K of the stream power law depends on V even for non-equilibrium topography. The numerical approach corroborates the control of V on erosion rates and facet height. It also shows a correlation between the shape of drainage basins and V (slope-area relationship) and it suggests the same for the parameters of the stream power law. Therefore both approaches suggest the possibility of using the height of triangular facets and the slope-area relationship to infer the fault slip rate of normal faults situated in a given climatic context.