Floodplain Backwater Restoration: A Case Study

USDA-ARS?s Scientific Manuscript database

Current thinking in stream ecology emphasizes the importance of floodplain backwaters within lowland riverine ecosystems. However, these types of habitat are becoming increasingly rare as development is transforming floodplain landscapes in fundamental ways. Two floodplain backwaters (severed mean...

Seasonal variation in nutrient retention during inundation of a short-hydroperiod floodplain

USGS Publications Warehouse

Noe, G.B.; Hupp, C.R.

2007-01-01

Floodplains are generally considered to be important locations for nutrient retention or inorganic-to-organic nutrient conversions in riverine ecosystems. However, little is known about nutrient processing in short-hydroperiod floodplains or seasonal variation in floodplain nutrient retention. Therefore, we quantified the net uptake, release or transformation of nitrogen (N), phosphorus (P) and suspended sediment species during brief periods (1-2 days) of overbank flooding through a 250-m floodplain flowpath on the fourth-order Mattawoman Creek, Maryland U.S.A. Sampling occurred during a winter, two spring and a summer flood in this largely forested watershed with low nutrient and sediment loading. Concentrations of NO3- increased significantly in surface water flowing over the floodplain in three of the four floods, suggesting the floodplain was a source of NO3-. The upper portion of the floodplain flowpath consistently exported NH4+, most likely due to the hyporheic: flushing of floodplain soil NH4+, which was then likely nitrified to NO3- in floodwaters. The floodplain was a sink for particulate organic P (POP) during two floods and particulate organic N and inorganic suspended sediment (ISS) during one flood. Large releases of all dissolved inorganic N and P species occurred following a snowmelt and subsequent cold winter flood. Although there was little consistency in most patterns of nutrient processing among the different floods, this floodplain, characterized by brief inundation, low residence time and low nutrient loading, behaved oppositely from the conceptual model for most floodplains in that it generally exported inorganic nutrients and imported organic nutrients.

The potential for dams to impact lowland meandering river floodplain geomorphology.

PubMed

Marren, Philip M; Grove, James R; Webb, J Angus; Stewardson, Michael J

2014-01-01

The majority of the world's floodplains are dammed. Although some implications of dams for riverine ecology and for river channel morphology are well understood, there is less research on the impacts of dams on floodplain geomorphology. We review studies from dammed and undammed rivers and include influences on vertical and lateral accretion, meander migration and cutoff formation, avulsion, and interactions with floodplain vegetation. The results are synthesized into a conceptual model of the effects of dams on the major geomorphic influences on floodplain development. This model is used to assess the likely consequences of eight dam and flow regulation scenarios for floodplain geomorphology. Sediment starvation downstream of dams has perhaps the greatest potential to impact on floodplain development. Such effects will persist further downstream where tributary sediment inputs are relatively low and there is minimal buffering by alluvial sediment stores. We can identify several ways in which floodplains might potentially be affected by dams, with varying degrees of confidence, including a distinction between passive impacts (floodplain disconnection) and active impacts (changes in geomorphological processes and functioning). These active processes are likely to have more serious implications for floodplain function and emphasize both the need for future research and the need for an "environmental sediment regime" to operate alongside environmental flows.

The Potential for Dams to Impact Lowland Meandering River Floodplain Geomorphology

PubMed Central

Marren, Philip M.; Grove, James R.; Webb, J. Angus; Stewardson, Michael J.

2014-01-01

The majority of the world's floodplains are dammed. Although some implications of dams for riverine ecology and for river channel morphology are well understood, there is less research on the impacts of dams on floodplain geomorphology. We review studies from dammed and undammed rivers and include influences on vertical and lateral accretion, meander migration and cutoff formation, avulsion, and interactions with floodplain vegetation. The results are synthesized into a conceptual model of the effects of dams on the major geomorphic influences on floodplain development. This model is used to assess the likely consequences of eight dam and flow regulation scenarios for floodplain geomorphology. Sediment starvation downstream of dams has perhaps the greatest potential to impact on floodplain development. Such effects will persist further downstream where tributary sediment inputs are relatively low and there is minimal buffering by alluvial sediment stores. We can identify several ways in which floodplains might potentially be affected by dams, with varying degrees of confidence, including a distinction between passive impacts (floodplain disconnection) and active impacts (changes in geomorphological processes and functioning). These active processes are likely to have more serious implications for floodplain function and emphasize both the need for future research and the need for an “environmental sediment regime” to operate alongside environmental flows. PMID:24587718

Quantitative model of the growth of floodplains by vertical accretion

USGS Publications Warehouse

Moody, J.A.; Troutman, B.M.

2000-01-01

A simple one-dimensional model is developed to quantitatively predict the change in elevation, over a period of decades, for vertically accreting floodplains. This unsteady model approximates the monotonic growth of a floodplain as an incremental but constant increase of net sediment deposition per flood for those floods of a partial duration series that exceed a threshold discharge corresponding to the elevation of the floodplain. Sediment deposition from each flood increases the elevation of the floodplain and consequently the magnitude of the threshold discharge resulting in a decrease in the number of floods and growth rate of the floodplain. Floodplain growth curves predicted by this model are compared to empirical growth curves based on dendrochronology and to direct field measurements at five floodplain sites. The model was used to predict the value of net sediment deposition per flood which best fits (in a least squares sense) the empirical and field measurements; these values fall within the range of independent estimates of the net sediment deposition per flood based on empirical equations. These empirical equations permit the application of the model to estimate of floodplain growth for other floodplains throughout the world which do not have detailed data of sediment deposition during individual floods. Copyright (C) 2000 John Wiley and Sons, Ltd.

Aquatic methane dynamics in a human-impacted river-floodplain of the Danube.

PubMed

Sieczko, Anna Katarzyna; Demeter, Katalin; Singer, Gabriel Andreas; Tritthart, Michael; Preiner, Stefan; Mayr, Magdalena; Meisterl, Karin; Peduzzi, Peter

2016-11-01

River-floodplain systems are characterized by changing hydrological connectivity and variability of resources delivered to floodplain water bodies. Although the importance of hydrological events has been recognized, the effect of flooding on CH 4 concentrations and emissions from European, human-impacted river-floodplains is largely unknown. This study evaluates aquatic concentrations and emissions of CH 4 from a highly modified, yet partly restored river-floodplain system of the Danube near Vienna (Austria). We covered a broad range of hydrological conditions, including a 1-yr flood event in 2012 and a 100-yr flood in 2013. Our findings demonstrate that river-floodplain waters were supersaturated with CH 4 , hence always serving as a source of CH 4 to the atmosphere. Hydrologically isolated habitats in general have higher concentrations and produce higher fluxes despite lower physically defined velocities. During surface connection, however, CH 4 is exported from the floodplain to the river, suggesting that the main channel serves as an "exhaust pipe" for the floodplain. This mechanism was especially important during the 100-yr flood, when a clear pulse of CH 4 was flushed from the floodplain with surface floodwaters. Our results emphasize the importance of floods differing in magnitude for methane evasion from river-floodplains; 34% more CH 4 was emitted from the entire system during the year with the 100-yr flood compared to a hydrologically "normal" year. Compared to the main river channel, semiisolated floodplain waters were particularly strong sources of CH 4 . Our findings also imply that the predicted increased frequency of extreme flooding events will have significant consequences for methane emission from river-floodplain systems.

Measuring floodplain spatial patterns using continuous surface metrics at multiple scales

USGS Publications Warehouse

Scown, Murray W.; Thoms, Martin C.; DeJager, Nathan R.

2015-01-01

Interactions between fluvial processes and floodplain ecosystems occur upon a floodplain surface that is often physically complex. Spatial patterns in floodplain topography have only recently been quantified over multiple scales, and discrepancies exist in how floodplain surfaces are perceived to be spatially organised. We measured spatial patterns in floodplain topography for pool 9 of the Upper Mississippi River, USA, using moving window analyses of eight surface metrics applied to a 1 × 1 m2 DEM over multiple scales. The metrics used were Range, SD, Skewness, Kurtosis, CV, SDCURV,Rugosity, and Vol:Area, and window sizes ranged from 10 to 1000 m in radius. Surface metric values were highly variable across the floodplain and revealed a high degree of spatial organisation in floodplain topography. Moran's I correlograms fit to the landscape of each metric at each window size revealed that patchiness existed at nearly all window sizes, but the strength and scale of patchiness changed within window size, suggesting that multiple scales of patchiness and patch structure exist in the topography of this floodplain. Scale thresholds in the spatial patterns were observed, particularly between the 50 and 100 m window sizes for all surface metrics and between the 500 and 750 m window sizes for most metrics. These threshold scales are ~ 15–20% and 150% of the main channel width (1–2% and 10–15% of the floodplain width), respectively. These thresholds may be related to structuring processes operating across distinct scale ranges. By coupling surface metrics, multi-scale analyses, and correlograms, quantifying floodplain topographic complexity is possible in ways that should assist in clarifying how floodplain ecosystems are structured.

Evaluating the effects of local floodplain management policies on property owner behavior

NASA Astrophysics Data System (ADS)

Bollens, Scott A.; Kaiser, Edward J.; Burby, Raymond J.

1988-05-01

Floodplain management programs have been adopted by more than 85% of local governments in the nation with designated flood hazard areas. Yet, there has been little evaluation of the influence of floodplain policies on private sector decisions. This article examines the degree to which riverine floodplain management affects purchase and mitigation decisions made by owners of developed floodplain property in ten selected cities in the United States. We find that the stringency of such policies does not lessen floodplain property buying because of the overriding importance of site amenity factors. Indeed, flood protection measures incorporated into development projects appear to add to the attractiveness of floodplain location by increasing the perceived safety from the hazard. Property owner responses to the flood hazard after occupancy involve political action more often than individual on-site mitigation. Floodplain programs only minimally encourage on-site mitigation by the owner because most owners have not experienced a flood and many are unaware of the flood threat. It is suggested that floodplain programs will be more effective in meeting their objectives if they are directed at intervention points earlier in the land conversion process.

Spatial variation in population dynamics of Sitka mice in floodplain forests.

Treesearch

T.A. Hanley; J.C. Barnard

1999-01-01

Population dynamics and demography of the Sitka mouse, Peromyscus keeni sitkensis, were studied by mark-recapture live-trapping over a 4-year period in four floodplain and upland forest habitats: old-growth Sitka spruce (Picea sitchensis) floodplain; red alder (Alnus rubra) floodplain; beaver-pond...

Influence of flow variability on floodplain formation and destruction, Little Missouri River, North Dakota

USGS Publications Warehouse

Miller, J.R.; Friedman, J.M.

2009-01-01

Resolving observations of channel change into separate planimetric measurements of floodplain formation and destruction reveals distinct relations between these processes and the flow regime. We analyzed a time sequence of eight bottomland images from 1939 to 2003 along the Little Missouri River, North Dakota, to relate geomorphic floodplain change to flow along this largely unregulated river. At the decadal scale, floodplain formation and destruction varied independently. Destruction was strongly positively correlated with the magnitude of infrequent high flows that recur every 5-10 yr, whereas floodplain formation was negatively correlated with the magnitude of frequent low flows exceeded 80% of the time. At the century scale, however, a climatically induced decrease in peak flows has reduced the destruction rate, limiting the area made available for floodplain formation. The rate of destruction was not uniform across the floodplain. Younger surfaces were consistently destroyed at a higher rate than older surfaces, suggesting that throughput of contaminants would have occurred more rapidly than predicted by models that assume uniform residence time of sediment across the floodplain. Maps of floodplain ages produced by analysis of sequential floodplain images are similar to maps of forest ages produced through dendrochronology, confirming the assumption of dendrogeomorphic studies that riparian tree establishment in this system is limited to recent channel locations. ?? 2009 Geological Society of America.

Climate change, urbanization, and optimal long-term floodplain protection

NASA Astrophysics Data System (ADS)

Zhu, Tingju; Lund, Jay R.; Jenkins, Marion W.; Marques, Guilherme F.; Ritzema, Randall S.

2007-06-01

This paper examines levee-protected floodplains and economic aspects of adaptation to increasing long-term flood risk due to urbanization and climate change. The lower American River floodplain in the Sacramento, California, metropolitan area is used as an illustration to explore the course of optimal floodplain protection decisions over long periods. A dynamic programming model is developed and suggests economically desirable adaptations for floodplain levee systems given simultaneous changes in flood climate and urban land values. Economic engineering optimization analyses of several climate change and urbanization scenarios are made. Sensitivity analyses consider assumptions about future values of floodplain land and damageable property along with the discount rate. Methodological insights and policy lessons are drawn from modeling results, reflecting the joint effects and relationships that climate, economic costs, and regional economic growth can have on floodplain levee planning decisions.

Characterising the Geomorphology of Forested Floodplains Using High Resolution Terrestrial Laser Scanning

NASA Astrophysics Data System (ADS)

Sear, D. A.; Brasington, J.; Darby, S. E.

2007-12-01

Forested floodplain environments represent the undisturbed land cover of most temperate and tropical river systems, but they are under threat from human resource management (Hughes et al., 2005, FLOBAR II Project report). A scientific understanding of forest floodplain processes therefore has relevance to ecosystem conservation and restoration, and the interpretation of pre-historic river and floodplain evolution. Empirical research has highlighted how overbank flows are relatively shallow and strongly modified by floodplain topography and the presence of vegetation and organic debris on the woodland floor [Jeffries et al., 2003, Geomorphology, 51, 61-80; Millington and Sear, 2007, Earth. Surf. Proc. Landforms, 32, doi: 10.1002/esp.1552]. In such instances flow blockage and diversions are common, and there is the possibility of frequent switches from sub-critical to locally super-critical flow. Such conditions also favour turbulence generation, both by wakes and by shear. Consequently, the floodplain terrain (where we take 'terrain' to include the underlying topography, root structures, and organic debris) plays a key role in modulating the processes of erosion and sedimentation that underpin the physical habitat diversity and hydraulic characteristics of complex wooded floodplain surfaces. However, despite the importance of these issues, as yet there are no formal, quantitative, descriptions of the highly complex and spatially diverse micro- and meso-topography that appears to be characteristic of forested floodplain surfaces. To address this gap, we have undertaken detailed surveys on a small floodplain reach within the Highland Water Research Catchment (HWRC: see http://www.geog.soton.ac.uk/research/nfrc/default.asp), which is a UK national reference site for lowland floodplain forest streams. This involved the deployment of a Leica ScanStation terrestrial laser-scanner from 14 setups and ranges of less than 30 m to acquire an extremely high resolution, accurate (185 million xyz observations, with absolute mean registration errors of 2 mm) 3-d point cloud model of the floodplain. These raw data were processed using a combination of Leica CYCLONE and bespoke filtering algorithms to construct a multi-resolution DTM of the forested floodplain at hitherto unprecedented detail (median point density ~4500 pts m-2). A key point is that the extreme precision and point density permit relevant features of the terrain (micro-topography, protruding roots, branches and stems, and surficial debris) that contribute to the floodplain roughness, to be readily and directly be incorporated in the DTM as topographic features. To characterise the morphology of the floodplain surface we have used the DTM to analyse a range of floodplain morphometric indices, in particular focusing on derivative surface roughness metrics (including roughness height) which are relevant in the parameterization of flow resistance. These are analysed at the floodplain scale to show the spatial distribution of roughness, and at a patch scale selected from a simple classification of floodplain surface. The analysis demonstrates spatial variability in roughness metrics at both scales, which have implications for parameterising flow resistance in models of wooded floodplains.

Radioactive contamination of the Balchug (Upper Yenisey) floodplain, Russia in relation to sedimentation processes and geomorphology.

PubMed

Linnik, V G; Brown, J E; Dowdall, M; Potapov, V N; Surkov, V V; Korobova, E M; Volosov, A G; Vakulovsky, S M; Tertyshnik, E G

2005-03-01

The radioactive contamination of a riverine floodplain, heavily influenced by discharges from Krasnoyarsk-26, has been studied with respect to sedimentation processes and the geomorphology of the Upper Yenisey floodplain. The study was effected by implementation of a regime of in situ observations and measurements, sampling, and the interpretation of satellite images. The results of the study indicate that on the Balchug Bypass Floodplain, radionuclide contamination is primarily influenced by the thickness of the deposited sediments, and the area can be considered as two depositional environments. The Balchug floodplain area was contaminated due to sedimentation of radionuclide-contaminated alluvium, whose depositional regime significantly changed after the construction of a hydroelectric power station in 1967. Contamination levels are lower on the upstream part of the floodplain where sediment depth is less than 0.2-0.3 m, and this contamination started to accumulate in 1967, while the downstream part of the floodplain, exhibiting deeper deposits, displays higher levels of radionuclide contamination because radionuclides began to deposit here in 1958 when the Krasnoyarsk-26 Mining and Chemical Combine (KMCC) commenced operation. Radionuclide contamination of the floodplain is also related to the elevation of the floodplain, higher regions of the floodplain typically having lower contamination than low-lying areas, which tend to be frequently inundated with sediments being deposited during such inundations. Local relief, its orientation, and vegetation cover have also combined to form sediment traps with significantly higher radionuclide contamination. Lithological analysis combined with radiometric assay indicates a total 137Cs floodplain inventory of 33.7 GBq.

Songbird use of floodplain and upland forests along the Upper Mississippi River corridor during spring migration

USGS Publications Warehouse

Kirsch, Eileen M.; Heglund, Patricia J.; Gray, Brian R.; Mckann, Patrick

2013-01-01

The Upper Mississippi River is thought to provide important stopover habitat for migrating landbirds because of its north-south orientation and floodplain forests. The river flows through the Driftless Area of southwestern Wisconsin and southeastern Minnesota where forests are plentiful, yet forests of the floodplain and Driftless Area uplands differ greatly in landscape setting, tree species composition, and topography. We compared landbird assemblages in these upland and floodplain forests over three springs, 2005–2007, using line-transect surveys at randomly selected areas in and within 16 km of the floodplain. We found more species of both transient and locally breeding migrants per survey in floodplain than in upland forest. Detections of transient neotropical migrants did not differ statistically by habitat. Detections of locally breeding neotropical and temperate-zone migrants and transient temperate-zone migrants were greater in floodplain than in upland forest. Between floodplain and upland forest, assemblages of locally breeding species, including neotropical and temperate-zone migrants (of which some individuals were in transit), differed substantially, but assemblages of transients (including both neotropical and temperate-zone migrants) did not differ as much. Only two species of transient migrants had clear affinities for floodplain forest, and none had an affinity for upland forest, whereas most locally breeding migrants had an affinity for either upland or floodplain forest. Within each spring, however, detections of transient neotropical migrants shifted from being greater in floodplain to greater in upland forests. This intraseasonal shift may be related to the phenology of certain tree species.

7 CFR 650.25 - Flood-plain management.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 7 Agriculture 6 2010-01-01 2010-01-01 false Flood-plain management. 650.25 Section 650.25... Flood-plain management. Through proper planning, flood plains can be managed to reduce the threat to... encourages sound flood-plain management decisions by land users. (a) Policy—(1) General. NRCS provides...

32 CFR 644.320 - Floodplain management.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 32 National Defense 4 2012-07-01 2011-07-01 true Floodplain management. 644.320 Section 644.320... ESTATE HANDBOOK Disposal § 644.320 Floodplain management. The requirements of Executive Order 11988, Floodplain Management, 42 FR 26951, (24 May 1977) and its implementation will be outlined in subpart H (to be...

32 CFR 644.320 - Floodplain management.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 32 National Defense 4 2011-07-01 2011-07-01 false Floodplain management. 644.320 Section 644.320... ESTATE HANDBOOK Disposal § 644.320 Floodplain management. The requirements of Executive Order 11988, Floodplain Management, 42 FR 26951, (24 May 1977) and its implementation will be outlined in subpart H (to be...

32 CFR 644.320 - Floodplain management.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 32 National Defense 4 2013-07-01 2013-07-01 false Floodplain management. 644.320 Section 644.320... ESTATE HANDBOOK Disposal § 644.320 Floodplain management. The requirements of Executive Order 11988, Floodplain Management, 42 FR 26951, (24 May 1977) and its implementation will be outlined in subpart H (to be...

77 FR 22774 - Estes to Flatiron Substation Transmission Lines Rebuild Project, Larimer County, CO

Federal Register 2010, 2011, 2012, 2013, 2014

2012-04-17

... Floodplain and Wetlands Involvement. SUMMARY: Western Area Power Administration currently owns and operates... floodplains and wetlands, so this Notice of Intent (NOI) also serves as a notice of proposed floodplain or wetland action in accordance with DOE floodplain and wetland environmental review requirements. DATES...

32 CFR 644.320 - Floodplain management.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 32 National Defense 4 2010-07-01 2010-07-01 true Floodplain management. 644.320 Section 644.320... ESTATE HANDBOOK Disposal § 644.320 Floodplain management. The requirements of Executive Order 11988, Floodplain Management, 42 FR 26951, (24 May 1977) and its implementation will be outlined in subpart H (to be...

7 CFR 650.25 - Flood-plain management.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 6 2011-01-01 2011-01-01 false Flood-plain management. 650.25 Section 650.25... Flood-plain management. Through proper planning, flood plains can be managed to reduce the threat to... encourages sound flood-plain management decisions by land users. (a) Policy—(1) General. NRCS provides...

A Geomorphic Analysis of Floodplain Lakes along the Embanked Lower Mississippi River for Managing Hydrologic Connectivity

NASA Astrophysics Data System (ADS)

Hudson, Paul; Boot, Dax; Sounny-Slitinne, M. Anwar; Kristensen, Kristiaan

2015-04-01

A Geomorphic Analysis of Floodplain Lakes along the Embanked Lower Mississippi River for Managing Hydrologic Connectivity Floodplain lakes are vital to the environmental integrity of lowland rivers. Embankment by levees (dikes) for flood control greatly reduces the size of lowland floodplains and is detrimental to the quality and functioning of floodplain water bodies, presenting a challenge to government agencies charged with environmental management. The embanked floodplain of the Lower Mississippi River is an enormous surface which includes a variety of lake types formed by geomorphic and anthropogenic processes. While much is known about the channel and hydrologic regime, very little is known about the physical structure and functioning of the embanked floodplain of the lower Mississippi. Importantly, management agencies do not have an inventory of the basic characteristics (e.g., type, frequency, location, size, shape) of water bodies within the lower Mississippi embanked floodplain. An analysis of lakes along the Lower Mississippi River embanked floodplain is performed by utilizing the National Hydrographic Dataset (NHD) from the U.S. Geological Survey, a LiDAR digital elevation model (DEM), as well as streamflow data from the USGS. The vector NHD data includes every official mapped water body (blue line polygons) on USGS topographic maps at scales of 1:100,000 and 1:24,000. Collectively, we identify thousands of discreet water bodies within the embanked floodplain. Utilizing planimetric properties the water bodies were classified into the following lake types: cutoffs (neck and chute), sloughs, crevasse (scour), local drainage (topographic), and borrow pits. The data is then statistically analyzed to examine significant differences in the spatial variability in lake types along the entire lower Mississippi embanked floodplain in association with geomorphic divisions and hydrologic regime. The total embanked floodplain area of the LMR is 7,303 km2,. The total area of floodplain lakes within the embanked floodplain is 382 km2, or 5.2% of the embanked floodplain surface area. Considerable variability in embanked floodplain area along the lower Mississippi, however, results in spatial variability in the frequency of specific lake types. Meander cutoff lakes represent the largest proportion of lake area, at 49%, with approximately half of this area comprised of artificial cutoff lakes. The next largest class of lakes are borrow pit lakes (at 16%), which are anthropogenic water bodies created for the process of levee (dike) construction and maintenance, but which represent valuable environmental habitat. Meander cutoff lakes are especially dominant in the upper reaches of the Lower Mississippi and diminish moving downstream, where the area of embanked floodplain also decreases. Interestingly, anthropogenic lakes (borrow pits) become increasingly prevalent further downstream and dominate over natural formed lakes. The location of lake types along the Lower Mississippi does not correspond with recent historic geomorphic and hydrologic activity. The highest frequency of meander cutoff and crevasse lakes are not located within floodplain sections which historically had the highest rates of lateral migration (m/yr) and flooding (duration). Although overbank hydrologic connectivity varies along the river, it does not vary necessarily where it would be most advantageous to the connectivity of specific types of lakes. The research results provide government agencies with a spatial inventory and methodological approach to improve the management of floodplain water bodies for sustaining valuable aquatic habitat, whether by artificially restricting or enhancing hydrologic connectivity. Key words: floodplain lakes, fluvial geomorphology, hydrologic connectivity, anthropogenic impacts, Lower Mississippi River

78 FR 70035 - Notice of Intent To Prepare an Environmental Impact Statement for the San Luis Transmission...

Federal Register 2010, 2011, 2012, 2013, 2014

2013-11-22

... Floodplain and Wetlands Involvement. SUMMARY: Western Area Power Administration (Western) is a power... floodplains and wetlands, so this Notice of Intent (NOI) also serves as a notice of proposed floodplain or wetland action in accordance with DOE floodplain and wetland environmental review requirements. DATES...

Response of fishes to floodplain connectivity during and following a 500-year flood event in the unimpounded upper Mississippi River

USGS Publications Warehouse

Barko, V.A.; Herzog, D.P.; O'Connell, M. T.

2006-01-01

We examined data collected on fish assemblage structure among three differing floodplain types (broad, moderate, and narrow) during the 1993 flood in the unimpounded reach of the upper Mississippi River. This 500 year flood event provided a unique opportunity to investigate fish-floodplain function because the main river channel is otherwise typically disjunct from approximately 82% of its floodplain by an extensive levee system. Fishes were sampled during three separate periods, and 42 species of adult and young-of-the-year (YOY) fishes were captured. Analysis of similarity (ANOSIM) revealed a significant and distinguishable difference between both adult and YOY assemblage structure among the three floodplain types. Analysis of variance revealed that Secchi transparency, turbidity, water velocity, and dissolved oxygen were significantly different among the floodplain types. However, only depth of gear deployment and Secchi transparency were significantly correlated with adult assemblage structure. None of these variables were significantly correlated with YOY assemblage structure. The numerically abundant families (adult and YOY catches combined) on the floodplain included Centrarchidae, Ictularidae, and Cyprinidae. Both native and non-native fishes were captured on the floodplain, and several of the numerically abundant species that were captured on the floodplain peaked in catch-per-unit-effort 1-3 years after the 1993 flood event. This suggests that some species may have used flooded terrestrial habitat for spawning, feeding, or both. The findings from our study provide much needed insight into fish-floodplain function in a temperate, channelized river system and suggest that lateral connectivity of the main river channel to less degraded reaches of its floodplain should become a management priority not only to maintain faunal biodiversity but also potentially reduce the impacts of non-native species in large river systems.

Quantifying Spatially Integrated Floodplain and Wetland Systems for the Conterminous US

NASA Astrophysics Data System (ADS)

Lane, C.; D'Amico, E.; Wing, O.; Bates, P. D.

2017-12-01

Wetlands interact with other waters across a variable connectivity continuum, from permanent to transient, from fast to slow, and from primarily surface water to exclusively groundwater flows. Floodplain wetlands typically experience fast and frequent surface and near-surface groundwater interactions with their river networks, leading to an increasing effort to tailor management strategies for these wetlands. Management of floodplain wetlands is contingent on accurate floodplain delineation, and though this has proven challenging, multiple efforts are being made to alleviate this data gap at the conterminous scale using spatial, physical, and hydrological floodplain proxies. In this study, we derived and contrasted floodplain extents using the following nationally available approaches: 1) a geospatial-buffer floodplain proxy (Lane and D'Amico 2016, JAWRA 52(3):705-722, 2) a regionalized flood frequency analysis coupled to a 30m resolution continental-scale hydraulic model (RFFA; Smith et al. 2015, WRR 51:539-553), and 3) a soils-based floodplain analysis (Sangwan and Merwade 2015, JAWRA 51(5):1286-1304). The geospatial approach uses National Wetlands Inventory and buffered National Hydrography Datasets. RFFA estimates extreme flows based on catchment size, regional climatology and upstream annual rainfall and routes these flows through a hydraulic model built with data from USGS HydroSHEDS, NOAA, and the National Elevation Dataset. Soil-based analyses define floodplains based on attributes within the USDA soil-survey data (SSURGO). Nearly 30% (by count) of U.S. freshwater wetlands are located within floodplains with geospatial analyses, contrasted with 37% (soils-based), and 53% (RFFA-based). The dichotomies between approaches are mainly a function of input data-layer resolution, accuracy, coverage, and extent, further discussed in this presentation. Ultimately, these spatial analyses and findings will improve floodplain and integrated wetland system extent assessment. This will lead to better management of the physically, chemically, and biologically integrated floodplain wetlands affecting the integrity of downstream waterbodies at multiple scales.

Biogeochemical and metabolic responses to the flood pulse in a semiarid floodplain

USGS Publications Warehouse

Valett, H.M.; Baker, M.A.; Morrice, J.A.; Crawford, C.S.; Molles, M.C.; Dahm, Clifford N.; Moyer, D.L.; Thibault, J.R.; Ellis, L.M.

2005-01-01

Flood pulse inundation of riparian forests alters rates of nutrient retention and organic matter processing in the aquatic ecosystems formed in the forest interior. Along the Middle Rio Grande (New Mexico, USA), impoundment and levee construction have created riparian forests that differ in their inter-flood intervals (IFIs) because some floodplains are still regularly inundated by the flood pulse (i.e., connected), while other floodplains remain isolated from flooding (i.e., disconnected). This research investigates how ecosystem responses to the flood pulse relate to forest IFI by quantifying nutrient and organic matter dynamics in the Rio Grande floodplain during three years of experimental flooding of the disconnected floodplain and during a single year of natural flooding of the connected floodplain. Surface and subsurface conditions in paired sites (control, flood) established in the two floodplain types were monitored to address metabolic and biogeochemical responses. Compared to dry controls, rates of respiration in the flooded sites increased by up to three orders of magnitude during the flood pulse. In the disconnected forest, month-long experimental floods produced widespread anoxia of four-week duration during each of the three years of flooding. In contrast, water in the connected floodplain remained well oxygenated (3-8 ppm). Material budgets for experimental floods showed the disconnected floodplain to be a sink for inorganic nitrogen and suspended solids, but a potential source of dissolved organic carbon (DOC). Compared to the main stem of the Rio Grande, flood-water on the connected floodplain contained less nitrate, but comparable concentrations of DOC, phosphate-phosphorus, and ammonium-nitrogen. Results suggest that floodplain IFI drives metabolic and biogeochemical responses during the flood pulse. Impoundment and fragmentation have altered floodplains from a mosaic of patches with variable IFI to a bimodal distribution. Relatively predictable flooding occurs in the connected forest, while inundation of the disconnected forest occurs only as the result of managed application of water. In semiarid floodplains, water is scarce except during the flood pulse. Ecosystem responses to the flood pulse are related to the IFI and other measures of flooding history that help describe spatial variation in ecosystem function.

Deep soil dynamics of floodplain carbon in the Central Valley of California

NASA Astrophysics Data System (ADS)

Steger, Kristin; Kim, Amy T.; Viers, Joshua H.; Fiener, Peter; Smart, David R.

2017-04-01

Active floodplains can putatively store large amounts of organic carbon (SOC) in subsoils originating from catchment erosion processes with subsequent floodplain deposition. Changes in catchment land use patterns and river management to optimize agricultural use of the floodplain or to restore the floodplain back to natural systems may alter SOC stocks in these soils. Our study focussed on the assessment of SOC pools associated with alluvial floodplain soils converting from conventional arable use to restored flooding and floodplain vegetation. We evaluated depth-dependent SOC contents using 21 drillings down to 3m and 10 drillings down to 7m along a transect through a floodplain area of the lower Cosumnes River, a non-constrained tributary to the Sacramento - San Joaquin Delta in California. In general, our data underline the importance of carbon stocks in subsoils >1m, which represent up to 19 and 6% of SOC stocks at the different sampling locations accounting for drillings down to 3 and 7m, respectively. All of our sampling sites revealed a SOC-rich buried A horizon between 70 and 130cm with SOC concentrations between 11 and 17g/kg, representative of the functioning floodplain system pre-disturbance. Radiocarbon dating showed that the 14C age in the buried horizon was younger than in the overlaying soils, indicating a substantial sedimentation phase with sediments of low SOC concentrations and higher carbon age. This sedimentation phase was probably associated with the huge upstream sediment production resulting from the hydraulic gold mining at the Cosumnes River starting around 1860. Apart from larger SOC contents in the buried horizon compared to the recent topsoil, its 13C and 15N isotopic signature also differed suggesting a change in long-term input of plant organic matter as well as different fertilization regimes during the agricultural use of the area from approx. 1890 onwards. In summary, deep alluvial soils in floodplains store large amounts of SOC not yet accounted for in global models. Intensive agricultural use of these floodplains often combined with river regulation and embanking of floodplain areas may lead to a slow but continuous release of the buried SOC to the atmosphere. However, restoration of floodplains may promote the stabilization of alluvial SOC in floodplains and hence contribute to more sustainable soils.

Denitrification mitigates N flux through the stream-floodplain complex of a desert city.

PubMed

Roach, W John; Grimm, Nancy B

2011-10-01

The Indian Bend Wash (IBW) flood-control project relies on a greenbelt to carry floods through Scottsdale, Arizona, USA. The greenbelt is characterized by a chain of shallow artificial lakes in a larger floodplain of irrigated turf, which has been protected from encroaching urban development. As such, this urban stream-floodplain complex can be divided into three subsystems: artificial lakes, channelized stream segments, and floodplain. We conducted experiments to evaluate which, if any, of these subsystems were important sites of denitrification, and to explore factors controlling denitrification rates. Denitrification enzyme activity (DEA) bioassays were conducted on sediments from eight lake and six stream segments as well as soil samples from eight floodplain transects. Mass-specific potential denitrification rates were significantly higher in lakes than in streams or floodplains. Nutrient limitation bioassays revealed that nitrate (NO3-) limited denitrification in lake sediments, a surprising finding given that NO3(-)-rich groundwater additions frequently raised lake NO3(-) concentration above 1 mg N/L. Experiments on intact lake cores suggested that denitrification was limited by the rate NO3(-) diffused into sediments, rather than its availability in overlying water. Floodplain denitrification was limited by water content, not NO3(-) or C, and irrigation of soils stimulated denitrification. We constructed a N budget for the IBW stream-floodplain complex based on our experimental results. We found that both lakes and floodplains removed large quantities of N, with denitrification removing 261 and 133 kg N ha(-1) yr(-1) from lake sediments and floodplain soils, respectively, indicating that lakes are hotspots for denitrification. Nevertheless, because floodplain area was >4.5 times that of lakes, floodplain soils removed nearly 2.5 times as much N as lake sediments. Given the desert's low annual precipitation, a finding that floodplain soils are active sites of denitrification might seem implausible; however, irrigation is common in urban landscapes, and it elevated annual denitrification in IBW. Based on our results, we conclude that construction of artificial lakes created hotspots while application of irrigation water created hot moments for denitrification in the stream-floodplain complex, demonstrating that management decisions can improve the ability of urban streams to provide critical ecosystem services like N retention.

Improved Calibration of Modeled Discharge and Storage Change in the Atchafalaya Floodplain Using SAR Interferometry

NASA Technical Reports Server (NTRS)

Jung, Hahn Chul; Jasinski, Michael; Kim, Jin-Woo; Shum, C. K.; Bates, Paul; Neal, Jeffrey; Lee, Hyongki; Alsdorf, Doug

2011-01-01

This study focuses on the feasibility of using SAR interferometry to support 2D hydrodynamic model calibration and provide water storage change in the floodplain. Two-dimensional (2D) flood inundation modeling has been widely studied using storage cell approaches with the availability of high resolution, remotely sensed floodplain topography. The development of coupled 1D/2D flood modeling has shown improved calculation of 2D floodplain inundation as well as channel water elevation. Most floodplain model results have been validated using remote sensing methods for inundation extent. However, few studies show the quantitative validation of spatial variations in floodplain water elevations in the 2D modeling since most of the gauges are located along main river channels and traditional single track satellite altimetry over the floodplain are limited. Synthetic Aperture Radar (SAR) interferometry recently has been proven to be useful for measuring centimeter-scale water elevation changes over the floodplain. In the current study, we apply the LISFLOOD hydrodynamic model to the central Atchafalaya River Basin, Louisiana, during a 62 day period from 1 April to 1 June 2008 using two different calibration schemes for Manning's n. First, the model is calibrated in terms of water elevations from a single in situ gauge that represents a more traditional approach. Due to the gauge location in the channel, the calibration shows more sensitivity to channel roughness relative to floodplain roughness. Second, the model is calibrated in terms of water elevation changes calculated from ALOS PALSAR interferometry during 46 days of the image acquisition interval from 16 April 2008 to 1 June 2009. Since SAR interferometry receives strongly scatters in floodplain due to double bounce effect as compared to specular scattering of open water, the calibration shows more dependency to floodplain roughness. An iterative approach is used to determine the best-fit Manning's n for the two different calibration approaches. Results suggest similar floodplain roughness but slightly different channel roughness. However, application of SAR interferometry provides a unique view of the floodplain flow gradients, not possible with a single gauge calibration. These gradients, allow improved computation of water storage change over the 46-day simulation period. Overall, the results suggest that the use of 2D SAR water elevation changes in the Atchafalaya basin offers improved understanding and modeling of floodplain hydrodynamics.

Non-linearities in Holocene floodplain sediment storage

NASA Astrophysics Data System (ADS)

Notebaert, Bastiaan; Nils, Broothaerts; Jean-François, Berger; Gert, Verstraeten

2013-04-01

Floodplain sediment storage is an important part of the sediment cascade model, buffering sediment delivery between hillslopes and oceans, which is hitherto not fully quantified in contrast to other global sediment budget components. Quantification and dating of floodplain sediment storage is data and financially demanding, limiting contemporary estimates for larger spatial units to simple linear extrapolations from a number of smaller catchments. In this paper we will present non-linearities in both space and time for floodplain sediment budgets in three different catchments. Holocene floodplain sediments of the Dijle catchment in the Belgian loess region, show a clear distinction between morphological stages: early Holocene peat accumulation, followed by mineral floodplain aggradation from the start of the agricultural period on. Contrary to previous assumptions, detailed dating of this morphological change at different shows an important non-linearity in geomorphologic changes of the floodplain, both between and within cross sections. A second example comes from the Pre-Alpine French Valdaine region, where non-linearities and complex system behavior exists between (temporal) patterns of soil erosion and floodplain sediment deposition. In this region Holocene floodplain deposition is characterized by different cut-and-fill phases. The quantification of these different phases shows a complicated image of increasing and decreasing floodplain sediment storage, which hampers the image of increasing sediment accumulation over time. Although fill stages may correspond with large quantities of deposited sediment and traditionally calculated sedimentation rates for such stages are high, they do not necessary correspond with a long-term net increase in floodplain deposition. A third example is based on the floodplain sediment storage in the Amblève catchment, located in the Belgian Ardennes uplands. Detailed floodplain sediment quantification for this catchments shows that a strong multifractality is present in the scaling relationship between sediment storage and catchment area, depending on geomorphic landscape properties. Extrapolation of data from one spatial scale to another inevitably leads to large errors: when only the data of the upper floodplains are considered, a regression analysis results in an overestimation of total floodplain deposition for the entire catchment of circa 115%. This example demonstrates multifractality and related non-linearity in scaling relationships, which influences extrapolations beyond the initial range of measurements. These different examples indicate how traditional extrapolation techniques and assumptions in sediment budget studies can be challenged by field data, further complicating our understanding of these systems. Although simplifications are often necessary when working on large spatial scale, such non-linearities may form challenges for a better understanding of system behavior.

Floodwater Chemistry in the Yolo Bypass during Winter and Spring 1998

USGS Publications Warehouse

Schemel, Laurence E.; Cox, Marisa H.

2007-01-01

A preliminary investigation of temporal and spatial variations in floodwater chemistry was conducted during winter and spring 1998 in the Yolo Bypass floodplain of the Sacramento River system. Samples were collected at locations along the eastern margin of the floodplain over the duration of the study and across the floodplain during major periods of inundation. Specific conductance and dissolved organic carbon concentrations along the eastern margin of the Yolo Bypass varied inversely with discharge. The Sacramento River was the greatest source of discharge to the floodplain during major periods of inundation. Increases in specific conductance and dissolved organic carbon were observed along the eastern margin during periods of lower discharge, when local streams accounted for a significant fraction of the total discharge through the Yolo Bypass. Apparent influences of local stream discharges also were observed in surface waters near the western margin of the floodplain during major periods of inundation. Although river and local stream sources of suspended particulate matter appeared important, in-floodplain processes were likely contributors to temporal and spatial variability in concentrations. Values for the C:N ratio of the particulate matter were lowest during periods of decreasing and low discharge through the floodplain, indicating production of phytoplankton in floodplain waters or supply to the floodplain by local stream sources. Phytoplankton discharged from the Yolo Bypass was detected by chlorophyll a monitors downstream in the Sacramento River during this study.

Estimating floodplain sedimentation in the Laguna de Santa Rosa, Sonoma County, CA

USGS Publications Warehouse

Curtis, Jennifer A.; Flint, Lorraine E.; Hupp, Cliff R.

2013-01-01

We present a conceptual and analytical framework for predicting the spatial distribution of floodplain sedimentation for the Laguna de Santa Rosa, Sonoma County, CA. We assess the role of the floodplain as a sink for fine-grained sediment and investigate concerns regarding the potential loss of flood storage capacity due to historic sedimentation. We characterized the spatial distribution of sedimentation during a post-flood survey and developed a spatially distributed sediment deposition potential map that highlights zones of floodplain sedimentation. The sediment deposition potential map, built using raster files that describe the spatial distribution of relevant hydrologic and landscape variables, was calibrated using 2 years of measured overbank sedimentation data and verified using longer-term rates determined using dendrochronology. The calibrated floodplain deposition potential relation was used to estimate an average annual floodplain sedimentation rate (3.6 mm/year) for the ~11 km2 floodplain. This study documents the development of a conceptual model of overbank sedimentation, describes a methodology to estimate the potential for various parts of a floodplain complex to accumulate sediment over time, and provides estimates of short and long-term overbank sedimentation rates that can be used for ecosystem management and prioritization of restoration activities.

Planning practice in support of economically and environmentally sustainable roads in floodplains: the case of the Mekong delta floodplains.

PubMed

Douven, Wim; Buurman, Joost

2013-10-15

Road development in relatively undisturbed floodplain systems, such as the floodplains of the Mekong River, will impact hydraulics and interrupt the natural flow of water. This affects the ecology and environment, and the livelihoods of people who depend on fishing and agriculture. On the other hand, floods can severely damage road infrastructure in years with large floods and can cause high annual maintenance costs. Improving road development practices in floodplains is a complex, multidimensional task involving hydraulic and geotechnical analysis, ecosystem analysis, socio-economic analysis, policy analysis, etc. This paper analyses the planning practice of road development and rehabilitation and how this practice can be improved in support of economically and environmentally sustainable roads in floodplains. It is concluded that although ample technical, planning and environmental assessment guidelines exist, guidelines need updating to address cumulative impacts at floodplain level and factors hampering the implementation in guidelines should be addressed in the guideline design (process). Copyright © 2013 Elsevier Ltd. All rights reserved.

Cosmogenic nuclide budgeting of floodplain sediment transfer

NASA Astrophysics Data System (ADS)

Wittmann, H.; von Blanckenburg, F.

2009-08-01

Cosmogenic nuclides produced in quartz may either decay or accumulate while sediment is moved through a river basin. A change in nuclide concentration resulting from storage in a floodplain is potentially important in large drainage basins in which sediment is prone to repeated burial and remobilization as a river migrates through its floodplain. We have modeled depth- and time-dependent cosmogenic nuclide concentration changes for 10Be, 26Al, and 14C during sediment storage and mixing in various active floodplain settings ranging from confined, shallow rivers with small floodplains to foreland-basin scale floodplains traversed by deep rivers. Floodplain storage time, estimated from channel migration rates, ranges from 0.4 kyr for the Beni River basin (Bolivia) to 7 kyr for the Amazon River basin, while floodplain storage depth, estimated from channel depth, ranges from 1 to 25 m. For all modeled active floodplain settings, the long-lived nuclides 10Be and 26Al show neither significant increase in nuclide concentration from irradiation nor decrease from decay. We predict a hypothetical response time after which changes in 10Be or 26Al concentrations become analytically resolvable. This interval ranges from 0.07 to 2 Myr and exceeds in all cases the typical residence time of sediment in a floodplain. Due to the much shorter half life of 14C, nuclide concentrations modeled for the in situ-produced variety of this nuclide are, however, sensitive to floodplain storage on residence times of < 20 kyr. The cosmogenic nuclide composition of old deposits in currently inactive floodplains that have been isolated for periods of millions of years from the river that once deposited them is predicted to either increase or decrease in 10Be and 26Al concentration, depending on the depositional depth. These conditions can be evaluated using the 26Al/ 10Be ratio that readily discloses the depth and duration of storage. We illustrate these models with examples from the Amazon basin. As predicted, modern bedload collected from an Amazon tributary, the Bolivian Beni River, shows no systematic change in nuclide concentration as sediment is moved through 500 km of floodplain by river meandering. In contrast, in the central Amazon floodplain currently untouched by the modern river system, low 26Al/ 10Be ratios account for minimum burial depths of 5 to 10 m for a duration of > 5 Myr. The important result of this analysis is that in all likely cases of active floodplains, cosmogenic 10Be and 26Al concentrations remain virtually unchanged over the interval sediment usually spends in the basin. Thus, spatially-averaged denudation rates of the sediment-producing area can be inferred throughout the entire basin, provided that nuclide production rates are scaled for the altitudes of the sediment-producing area only, because floodplain storage does not modify nuclide concentrations introduced from the sediment source area.

Geomorphic floodplain with organic matter (biomass) estimates for Fanno Creek, Oregon

USGS Publications Warehouse

Sobieszczyk, Steven

2011-01-01

Fanno Creek is a tributary to the Tualatin River and flows though parts of the southwest Portland metropolitan area. The stream is heavily influenced by urban runoff and shows characteristic flashy streamflow and poor water quality commonly associated with urban streams. This data set represents the geomorphic floodplain as derived from light detection and ranging (LiDAR) data and aerial photographic imagery. The floodplain represents current conditions including both anthropogenic alterations and natural historic floodplain features. The floodplain dataset is divided into 13 reach segments and attributed with corresponding organic material load estimates for each reach.

Active overbank deposition during the last century, South River, Virginia

NASA Astrophysics Data System (ADS)

Pizzuto, Jim; Skalak, Katherine; Pearson, Adam; Benthem, Adam

2016-03-01

We quantify rates of overbank deposition over decadal to centennial timescales along the South River in Virginia using four independent methods. Detailed mercury profiles sampled adjacent to the stream channel preserve the peak historic mercury concentration on suspended sediment dating from 1955 to 1961 and suggest sedimentation rates of 8 to 50 cm/100 years. Sediment accumulation over the roots of trees suggest rates of 0 to 100 cm/100 years, with significantly higher values on levees and lower values on floodplains farther from the channel. Profiles of 137Cs and 210Pb from two eroding streambanks are fit with an advection-diffusion model calibrated at an upland reference site; these methods suggest sedimentation rates of 44 to 73 cm/100 years. Mercury inventories from 107 floodplain cores, combined with a previously published reconstruction of the history of mercury concentration on suspended sediment, provide spatially comprehensive estimates of floodplain sedimentation: median sedimentation rates are 3.8 cm/100 years for the < 0.3-year floodplain, 1.37 cm/100 years for the 0.3- to 2-year floodplain, 0.4 cm/100 years for the 2- to 5-year floodplain, and 0.1 cm/100 years for the 5- to 62-year floodplain. While these sedimentation rates are relatively low, the total mass of sediment stored from 1930 to 2007 is 4.9 ± 1.7 (95% confidence interval) × 107 kg, corresponding to an average thickness of 2.5 cm (3.2 cm/100 years). These results demonstrate that floodplains of our 4.5-km-long study reach have stored 8 to 12% of the total suspended sediment supplied to the study reach of the South River. Hydrologic Engineering Center-River Analysis System (HEC-RAS) modeling demonstrates that the floodplain of the South River remains hydraulically connected to the channel: 56% of the 100-year floodplain is inundated every two years, and 83% of the floodplain is inundated every five years. These results, combined with previously published data, provide the basis for a regional synthesis of floodplain deposition rates since European settlement. Floodplain sedimentation rates were high following European settlement, with published estimates ranging from 50 to 200 cm/100 years. Sedimentation rates decreased by 1 to 2 orders of magnitude during the twentieth and twenty-first centuries; but despite these lower sedimentation rates, floodplains continue to store a significant fraction of total suspended sediment load. Many floodplains of the mid-Atlantic region are active landforms fully connected to the rivers that flow within them and should not be considered terraces isolated from contemporary fluvial processes by post-settlement aggradation.

Effects of river-floodplain exchange on water quality and nutrient export in the dam-impacted Kafue River (Zambia)

NASA Astrophysics Data System (ADS)

Zurbrugg, R.; Wamulume, J.; Blank, N.; Nyambe, I.; Wehrli, B.; Senn, D. B.

2010-12-01

Biogeochemical processes in river-floodplain ecosystems are strongly influenced by hydrology and, in particular, river-floodplain exchange. In tropical systems, where the hydrology is dominated by distinct dry and rainy seasons, annual flood waters trigger organic matter mineralization within and nutrient export from the dried and rewetted floodplain, and the magnitude of hydrological exchange between a river and its floodplain has the potential to substantially influence nutrient and carbon exports and water quality in the river. In this study we examined the extent and the effects of hydrological river-floodplain exchange in the Kafue River and its floodplain, the Kafue Flats, in Zambia. The Kafue Flats is a 7000 km2 seasonal wetland whose hydrological regime has been impacted by upstream and downstream large dams constructed in the 1970s, leading to changes in the flooding pattern in this high-biodiversity ecosystem. Field campaigns, carried out during flood recession (May 2008, 2009, 2010) and covering a ~400 km river stretch, revealed a steep decline in dissolved oxygen from 6 mg/L to 1 mg/L over a ~20 km stretch of river beginning approximately 200 km downstream from the first dam, with low oxygen persisting for an additional 150 km downstream. To further explore this phenomenon discharge measurements (ADCP) were conducted in May 2009 and May 2010. River discharge decreased from ~600 m3/s at the upstream dam to 100 m3/s midway through the Kafue Flats, and increased to >800 m3/s towards the end of the floodplain (400 km downstream). River cross section data indicate that the dramatic decrease in discharge occured primarily because of variations in channel area and channel carrying capacity, with channel constrictions forcing ~85% of the discharge out of the river channel and into the floodplain. Using specific conductivity and δ18O-H2O as tracers for floodplain water, we estimate that the downstream increases in flow occur through lateral inflows of receding floodplain waters, induced by an expansion of the river channel, and that 80% of the downstream flow came from the floodplain. Model calculations indicate that intense exchange between river and floodplain and the introduction of low-oxygen floodplain water into the river was the primary cause of the low dissolved oxygen levels observed in the river during flood recession in May 2008-2010. This exchange also appears to play an important role in nutrient and carbon export, with the floodplain acting as a net source of phosphate (220 tons/yr), total nitrogen (1300 tons/yr, of which ~90% was organic nitrogen) and total organic carbon (50,000 tons/yr) to downstream systems.

A method to quantify and value floodplain sediment and nutrient retention ecosystem services

USGS Publications Warehouse

Hopkins, Kristina G.; Noe, Gregory; Franco, Fabiano; Pindilli, Emily J.; Gordon, Stephanie; Metes, Marina J.; Claggett, Peter; Gellis, Allen; Hupp, Cliff R.; Hogan, Dianna

2018-01-01

Floodplains provide critical ecosystem services to local and downstream communities by retaining floodwaters, sediments, and nutrients. The dynamic nature of floodplains is such that these areas can both accumulate sediment and nutrients through deposition, and export material downstream through erosion. Therefore, estimating floodplain sediment and nutrient retention should consider the net flux of both depositional and erosive processes. An ecosystem services framework was used to quantify and value the sediment and nutrient ecosystem service provided by floodplains in the Difficult Run watershed, a small (151 km2) suburban watershed located in the Piedmont of Virginia (USA). A sediment balance was developed for Difficult Run and two nested watersheds. The balance included upland sediment delivery to streams, stream bank flux, floodplain flux, and stream load. Upland sediment delivery was estimated using geospatial datasets and a modified Revised Universal Soil Loss Equation. Predictive models were developed to extrapolate field measurements of the flux of sediment, sediment-bound nitrogen (N), and sediment-bound phosphorus (P) from stream banks and floodplains to 3232 delineated stream segments in the study area. A replacement cost approach was used to estimate the economic value of the sediment and nutrient retention ecosystem service based on estimated net stream bank and floodplain flux of sediment-bound N for all streams in the study area. Results indicated the net fluvial fluxes of sediment, sediment-bound N, and sediment-bound P were −10,439 Mg yr−1 (net export), 57,300 kg-N yr−1(net trapping), and 98 kg-P yr−1(net trapping), respectively. For sediment, floodplain retention was offset by substantial losses from stream bank erosion, particularly in headwater catchments, resulting in a net export of sediment. Nutrient retention in the floodplain exceeded that lost through stream bank erosion resulting in net retention of nutrients (TN and TP). Using a conservative cost estimate of $12.69 (USD) per kilogram of nitrogen, derived from wastewater treatment costs, the estimated annual value for sediment and nutrient retention on Difficult Run floodplains was $727,226 ± 194,220 USD/yr. Values and differences in floodplain nitrogen retention among stream reaches can be used to target areas for floodplain conservation and stream restoration. The methods presented are scalable and transferable to other areas if appropriate datasets are available for validation.

Managing the Mississippi River floodplain: Achieving ecological benefits requires more than hydrological connection to the river: Chapter

USGS Publications Warehouse

Schramm, Harold; Richardson, William B.; Knights, Brent C.

2015-01-01

Floodplains are vital to the structure and function of river-floodplain ecosystems. Among the many ecological services provided by floodplains are nutrient cycling and seasonal habitats for fish, including spawning, nursery, foraging and wintering habitats. Connections between the river channel and floodplain habitats are essential to realize these ecological services, but spatial and temporal aspects of the connection and contemporary geomorphology must also be considered in restoration efforts. This chapter synthesizes available information to compare floodplain function and needed management strategies in two extensive reaches (upper impounded and lower free-flowing) of the Mississippi River, USA. The upper impounded reach is the 523-km reach from about Minneapolis, Minnesota to Clinton, Iowa. This reach has been impounded and channelized for navigation. Mean annual water-level fluctuation ranges from 1 to 2 m in the navigation pools in this reach. Floodplain environmental conditions that affect nitrogen cycling and fish production vary seasonally and longitudinally within and among navigation pools. Significant issues affecting ecological services include sedimentation, constrained water level fluctuations, island erosion and seasonal hypoxia. The lower free-flowing reach, the 1570-km reach from the confluence of the Ohio and Mississippi rivers to the Gulf of Mexico, has no dams and average annual fluctuations of 7 m throughout most of the reach. Despite the substantial flood pulse, floodplain inundation is often brief and may not occur annually. Significant issues affecting floodplain ecological function are the short duration and thermal asynchrony of the flood pulse, sedimentation and loss of connection between the river channel and permanent/semi-permanent floodplain water bodies due to channel incision. Needs and strategies for floodplain enhancement to increase ecological services, particularly nitrogen cycling and fish production, differ along the longitudinal gradient of the Mississippi River and provide informative contrasts to guide floodplain management. Prediction of the effects of climate change on this system will be complicated by the magnitude of the watershed that encompasses 41 % of the continental USA and multiple climatic regions.

Carbon, nitrogen, and phosphorus accumulation in floodplains of Atlantic Coastal Plain rivers, USA

USGS Publications Warehouse

Noe, G.B.; Hupp, C.R.

2005-01-01

Net nutrient accumulation rates were measured in riverine floodplains of the Atlantic Coastal Plain in Virginia, Maryland, and Delaware, USA. The floodplains were located in watersheds with different land use and included two sites on the Chickahominy River (urban), one site on the Mattaponi River (forested), and five sites on the Pocomoke River (agricultural). The Pocomoke River floodplains lie along reaches with natural hydrogeomorphology and on reaches with restricted flooding due to channelization and levees. A network of feldspar clay marker horizons was placed on the sediment surface of each floodplain site 3-6 years prior to sampling. Sediment cores were collected from the material deposited over the feldspar clay pads. This overlying sediment was separated from the clay layer and then dried, weighed, and analyzed for its total carbon (C), nitrogen (N), and phosphorus (P) content. Mean C accumulation rates ranged from 61 to 212 g??m-2??yr-1, N accumulation rates ranged from 3.5 to 13.4 g??m -2??yr-1, and P accumulation rates ranged from 0.2 to 4.1 g??m-2??yr-1 among the eight floodplains. Patterns of intersite variation in mineral sediment and P accumulation rates were similar to each other, as was variation in organic sediment and C and N accumulation rates. The greatest sediment and C, N, and P accumulation rates were observed on Chickahominy River floodplains downstream from the growing metropolitan area of Richmond, Virginia. Nutrient accumulation rates were lowest on Pocomoke River floodplains that have been hydraulically disconnected from the main channel by channelization and levees. Sediment P concentrations and P accumulation rates were much greater on the hydraulically connected floodplain immediately downstream of the limit of channelization and dense chicken agriculture of the upper Pocomoke River watershed. These findings indicate that (1) watershed land use has a large effect on sediment and nutrient retention in floodplains, and (2) limiting the hydraulic connectivity between river channels and floodplains minimizes material retention by floodplains in fluvial hydroscapes. ?? 2005 by the Ecological Society of America.

Tradeoffs of strategically reconnecting rivers to their floodplains: The case of the Lower Illinois River (USA).

PubMed

Guida, Ross J; Remo, Jonathan W F; Secchi, Silvia

2016-12-01

During the latter half of the 19th Century and first half of the 20th Century, the Illinois River was heavily altered through leveeing off large portions of its floodplain, draining wetlands, and the construction of dams and river-training structures that facilitated navigation. As a result of these alterations, flood stages continue to rise, increasing flood risk and threatening to overtop levees along the La Grange Segment (LGS) of the Illinois River. Over the last two decades, more emphasis has been placed on reconnecting portions of floodplains to rivers in order to solve the long-term problem of rising flood heights attributed to continual heightening of levees to provide flood protection. Multiple studies have suggested that strategically reconnecting larger portions of the LGS could result in more sustainable floodplain management. However, the true costs and benefits of reconnecting the floodplain are not known. We use a novel hydrodynamic, geospatial, economic, and habitat suitability framework to assess the tradeoffs of strategically reconnecting the Illinois River to its floodplain in order to decrease flood risk, improve floodplain habitats, and limit the costs of reconnection. Costs include building-associated losses, lost agricultural profits, and levee removal and construction costs. Tested scenarios demonstrate that while flood heights and environmental benefits are maximized through the most aggressive levee setbacks and removals, these scenarios also have the highest costs. However, the tradeoff of implementing lower-cost scenarios is that there is less flood-height reduction and less floodplain habitat available. Several individual levee districts have high potential for reconnection based on limiting potential damages as well as providing floodplain habitat. To implement large-scale strategic floodplain reconnection, costs range from $1.2-$4.3 billion. As such, payments for ecosystem services will likely be necessary to compensate landowners for decreased long-term agricultural production and building losses that result in flood-reduction benefits and increased floodplain habitat. Copyright © 2016 Elsevier B.V. All rights reserved.

Managing Floodplain Expectations on the Lower Missouri River, USA.

NASA Astrophysics Data System (ADS)

Bulliner, E. A., IV; Jacobson, R. B.; Lindner, G. A.; Paukert, C.; Bouska, K.

2017-12-01

The Missouri River is an archetype of the challenges of managing large rivers and their floodplains for multiple objectives. At 1.3 million km2 drainage area, the Missouri boasts the largest reservoir system in North America with 91 km3 of total storage; in an average year the system generates 10 billion kilowatt hours of electricity. The Lower Missouri River floodplain extends 1,300 km downstream from the reservoir system and encompasses approximately 9,200 km2. For the past 150 years, the floodplain has been predominantly used for agriculture much of which is protected from flooding by private and Federal levees. Reservoir system operating policies prioritize flood-hazard reduction but in recent years, large, damaging floods have demonstrated system limitations. These large floods and changing societal values have created new expectations about how conversion of floodplain agricultural lands to conservation lands might increase ecosystem services, in particular decreasing flood risk and mitigating fluxes of nutrients to the Gulf of Mexico. Our research addresses these expectations at multiple spatial scales by starting with hydrologic and hydraulic models to understand controls on floodplain hydrodynamics. The results document the substantial regional spatial variability in floodplain connectivity that exists because of multi-decadal channel adjustments to channelization and sediment budgets. Exploration of levee setback scenarios with 1- and 2-dimensional hydrodynamic models indicates modest and spatially variable gains in flood-hazard reduction are possible if substantial land areas (50% or more) are converted from agricultural production. Estimates of potential denitrification benefits of connecting floodplains indicate that the floodplain has the capacity to remove 100's to 1,000's of metric tons of N each year, but amounts to a maximum of about 5% the existing load of 200,000 ton*y-1. The results indicate that in this river-floodplain system, the ecosystem services associated with floodplain conversion can be substantial, but the sum of benefits needed to justify land conversion over broad areas remains uncertain.

Influences of Altered River Geomorphology on Channel-Floodplain Mass and Momentum Transfer

NASA Astrophysics Data System (ADS)

Byrne, C. F.; Stone, M. C.

2017-12-01

River management strategies, including both river engineering and restoration, have altered river geomorphology and associated lateral channel-floodplain connectivity throughout the world. This altered connectivity is known to drive changes in ecologic and geomorphic processes during floods, however, quantification of altered connectivity is difficult due to the highly dynamic spatial and temporal nature of flood wave conditions. The objective of this research was to quantify the physical processes of lateral mass and momentum transfer at the channel-floodplain interface. The objective was achieved with the implementation of novel scripting and high-resolution, two-dimensional hydrodynamic modeling techniques under unsteady flow conditions. The process-based analysis focused on three geomorphic feature types within the Middle Rio Grande, New Mexico, USA: (1) historical floodplain surfaces, (2) inset floodplain surfaces formed as a result of channel training and hydrologic alteration, and (3) mechanically restored floodplain surfaces. Results suggest that inset floodplain feature types are not only subject to greater mass and momentum transfer magnitudes, but those connections are also more heterogeneous in nature compared with historical feature types. While restored floodplain feature types exhibit transfer magnitudes and heterogeneity comparable to inset feature types, the surfaces are not of great enough spatial extent to substantially influence total channel-floodplain mass and momentum transfer. Mass and momentum transfer also displayed differing characteristic changes as a result of increased flood magnitude, indicating that linked hydrodynamic processes can be altered differently as a result of geomorphic and hydrologic change. The results display the potential of high-resolution modeling strategies in capturing the spatial and temporal complexities of river processes. In addition, the results have implications for other fields of river science including biogeochemical exchange at the channel-floodplain interface and quantification of process associated with environmental flow and river restoration strategies.

Floodplain-wide coupling of flooding and vegetation patterns in the Tonle Sap of the Mekong River

NASA Astrophysics Data System (ADS)

Arias, M. E.; Haberstroh, C.

2017-12-01

Floodplain vegetation is one of the prime drivers of ecosystem productivity, thus floodplain-wide monitoring is critical to ensure the well-being of these ecosystems and the important services they provide to riparian societies. Therefore, the objective of this presentation is to introduce a novel methodology to monitor long-term and large-scale patterns of rooted vegetation in seasonally inundated floodplains. We applied this methodology to an floodplain area of ac. 18,000 km2 in the Tonle Sap (Cambodia), a complex hydro-ecological system directly connected to the Mekong River. The overall hypothesis of this study is that floodplain vegetation condition is dictated by gradients of disturbance from the uplands and from the flood-pulse itself. We first demonstrate that spatial vegetation patterns represented by the normalized difference vegetation index (NDVI) during the dry season -when interference from cloud cover and partial inundation is minimal- correspond well to meaningful land use/land cover groups as well as canopy cover data collected in the field. Annual trends (2000-2016) in NDVI spatial distribution showed that the modality of dry season NDVI is largely governed by the magnitude of flooding in the antecedent hydrological year. Indeed, we found a significant relationship between flood duration -defined as the number of months annually a floodplain pixel remains flooded- and floodplain-wide NDVI. We also determined that ac. 115 km2 yr-1 of the highest quality vegetation, were replaced by fallow land during the period of study. This research has important insights on the main drivers of floodplain vegetation in the Tonle Sap, and the proposed methodology, using data from freely available worldwide satellite imagery (MODIS), promises to be an effective method to monitor ecosystem change in large floodplains across the world.

Increasing floodplain connectivity through urban stream restoration increases nutrient and sediment retention

USGS Publications Warehouse

McMillan, Sara K.; Noe, Gregory

2017-01-01

Stream restoration practices frequently aim to increase connectivity between the stream channel and its floodplain to improve channel stability and enhance water quality through sediment trapping and nutrient retention. To measure the effectiveness of restoration and to understand the drivers of these functional responses, we monitored five restored urban streams that represent a range of channel morphology and restoration ages. High and low elevation floodplain plots were established in triplicate in each stream to capture variation in floodplain connectivity. We measured ecosystem geomorphic and soil attributes, sediment and nutrient loading, and rates of soil nutrient biogeochemistry processes (denitrification; N and P mineralization) then used boosted regression trees (BRT) to identify controls on sedimentation and nutrient processing. Local channel and floodplain morphology and position within the river network controlled connectivity with increased sedimentation at sites downstream of impaired reaches and at floodplain plots near the stream channel and at low elevations. We observed that nitrogen loading (both dissolved and particulate) was positively correlated with denitrification and N mineralization and dissolved phosphate loading positively influenced P mineralization; however, none of these input rates or transformations differed between floodplain elevation categories. Instead, continuous gradients of connectivity were observed rather than categorical shifts between inset and high floodplains. Organic matter and nutrient content in floodplain soils increased with the time since restoration, which highlights the importance of recovery time after construction that is needed for restored systems to increase ecosystem functions. Our results highlight the importance of restoring floodplains downstream of sources of impairment and building them at lower elevations so they flood frequently, not just during bankfull events. This integrated approach has the greatest potential for increasing trapping of sediment, nutrients, and associated pollutants in restored streams and thereby improving water quality in urban watersheds.

Floodplain complexity and surface metrics: influences of scale and geomorphology

USGS Publications Warehouse

Scown, Murray W.; Thoms, Martin C.; DeJager, Nathan R.

2015-01-01

Many studies of fluvial geomorphology and landscape ecology examine a single river or landscape, thus lack generality, making it difficult to develop a general understanding of the linkages between landscape patterns and larger-scale driving variables. We examined the spatial complexity of eight floodplain surfaces in widely different geographic settings and determined how patterns measured at different scales relate to different environmental drivers. Floodplain surface complexity is defined as having highly variable surface conditions that are also highly organised in space. These two components of floodplain surface complexity were measured across multiple sampling scales from LiDAR-derived DEMs. The surface character and variability of each floodplain were measured using four surface metrics; namely, standard deviation, skewness, coefficient of variation, and standard deviation of curvature from a series of moving window analyses ranging from 50 to 1000 m in radius. The spatial organisation of each floodplain surface was measured using spatial correlograms of the four surface metrics. Surface character, variability, and spatial organisation differed among the eight floodplains; and random, fragmented, highly patchy, and simple gradient spatial patterns were exhibited, depending upon the metric and window size. Differences in surface character and variability among the floodplains became statistically stronger with increasing sampling scale (window size), as did their associations with environmental variables. Sediment yield was consistently associated with differences in surface character and variability, as were flow discharge and variability at smaller sampling scales. Floodplain width was associated with differences in the spatial organization of surface conditions at smaller sampling scales, while valley slope was weakly associated with differences in spatial organisation at larger scales. A comparison of floodplain landscape patterns measured at different scales would improve our understanding of the role that different environmental variables play at different scales and in different geomorphic settings.

Absolute water storages in the Congo River floodplains from integration of InSAR and satellite radar altimetry

NASA Astrophysics Data System (ADS)

Lee, H.; Yuan, T.; Jung, H. C.; Aierken, A.; Beighley, E.; Alsdorf, D. E.; Tshimanga, R.; Kim, D.

2017-12-01

Floodplains delay the transport of water, dissolved matter and sediments by storing water during flood peak seasons. Estimation of water storage over the floodplains is essential to understand the water balances in the fluvial systems and the role of floodplains in nutrient and sediment transport. However, spatio-temporal variations of water storages over floodplains are not well known due to their remoteness, vastness, and high temporal variability. In this study, we propose a new method to estimate absolute water storages over the floodplains by establishing relations between water depths (d) and water volumes (V) using 2-D water depth maps from the integration of Interferometric Synthetic Aperture Radar (InSAR) and altimetry measurements. We applied this method over the Congo River floodplains and modeled the d-V relation using a power function (note that d-V indicates relation between d and V, not d minus V), which revealed the cross-section geometry of the floodplains as a convex curve. Then, we combined this relation and Envisat altimetry measurements to construct time series of floodplain's absolute water storages from 2002 to 2011. Its mean annual amplitude over the floodplains ( 7,777 km2) is 3.860.59 km3 with peaks in December, which lags behind total water storage (TWS) changes from the Gravity Recovery and Climate Experiment (GRACE) and precipitation changes from Tropical Rainfall Measuring Mission (TRMM) by about one month. The results also exhibit inter-annual variability, with maximum water volume to be 5.9 +- 0.72 km3 in the wet year of 2002 and minimum volume to be 2.01 +- 0.63 km3 in the dry year of 2005. The inter-annual variation of water storages can be explained by the changes of precipitation from TRMM.

Hydrological Signature From River-Floodplain Interactions

NASA Astrophysics Data System (ADS)

Paiva, R. C. D.; Fleischmann, A. S.; Collischonn, W.; Sorribas, M.; Pontes, P. R.

2015-12-01

Understanding river-floodplain hydraulic processes is fundamental to promote comprehension of related water paths, biogeochemicalcyclesand ecosystems. Large river basins around the globe present enormous developed floodplains, which strongly affect flood waves and water dynamics. Since most of these river-floodplain interactions are not monitored, it is interesting to develop strategies to understand such processes through characteristic hydrological signatures, e.g. hydrographs. We studied observed hydrographs from large South American rivers and found that in several cases rivers with extensive wetlands present a particular hydrograph shape, with slower rising limb in relation to the receding one, due to storage effects and the associated decrease of wave celerity with stage. A negative asymmetry in the hydrograph is generated, which is higher when more water flows through floodplains upstream of the observed point. Finally, we studied the Amazon basin using gauged information and simulation results from the MGB-IPH regional hydrological model. Major rivers with larger wetland areas (e.g. Purus, Madeira and Juruá) were identified with higher negative asymmetry in their hydrographs. The hydrodynamic model was run in scenarios with and without floodplains, and results supported that floodplain storage affects hydrographs in creating a negative asymmetry, besides attenuating peaks, increasing hydrograph smoothness and increasing minimum flows. Finally, different wetland types could be distinguished with hydrograph shape, e.g. differing wetlands fed by local rainfall from wetlands due to overbank flow (floodplains). These metrics and concepts on hydrograph features have great potential to infer about river-floodplain processes from large rivers and wetland systems.

Gravel-bed river floodplains are the ecological nexus of glaciated mountain landscapes

USGS Publications Warehouse

Hauer, F. Richard; Locke, Harvey; Dreitz, Victoria; Hebblewhite, Mark; Lowe, Winsor; Muhlfeld, Clint C.; Nelson, Cara; Proctor, Michael F.; Rood, Stewart B.

2016-01-01

Gravel-bed river floodplains in mountain landscapes disproportionately concentrate diverse habitats, nutrient cycling, productivity of biota, and species interactions. Although stream ecologists know that river channel and floodplain habitats used by aquatic organisms are maintained by hydrologic regimes that mobilize gravel-bed sediments, terrestrial ecologists have largely been unaware of the importance of floodplain structures and processes to the life requirements of a wide variety of species. We provide insight into gravel-bed rivers as the ecological nexus of glaciated mountain landscapes. We show why gravel-bed river floodplains are the primary arena where interactions take place among aquatic, avian, and terrestrial species from microbes to grizzly bears and provide essential connectivity as corridors for movement for both aquatic and terrestrial species. Paradoxically, gravel-bed river floodplains are also disproportionately unprotected where human developments are concentrated. Structural modifications to floodplains such as roads, railways, and housing and hydrologicaltering hydroelectric or water storage dams have severe impacts to floodplain habitat diversity and productivity, restrict local and regional connectivity, and reduce the resilience of both aquatic and terrestrial species, including adaptation to climate change. To be effective, conservation efforts in glaciated mountain landscapes intended to benefit the widest variety of organisms need a paradigm shift that has gravel-bed rivers and their floodplains as the central focus and that prioritizes the maintenance or restoration of the intact structure and processes of these critically important systems throughout their length and breadth.

Gravel-bed river floodplains are the ecological nexus of glaciated mountain landscapes.

PubMed

Hauer, F Richard; Locke, Harvey; Dreitz, Victoria J; Hebblewhite, Mark; Lowe, Winsor H; Muhlfeld, Clint C; Nelson, Cara R; Proctor, Michael F; Rood, Stewart B

2016-06-01

Gravel-bed river floodplains in mountain landscapes disproportionately concentrate diverse habitats, nutrient cycling, productivity of biota, and species interactions. Although stream ecologists know that river channel and floodplain habitats used by aquatic organisms are maintained by hydrologic regimes that mobilize gravel-bed sediments, terrestrial ecologists have largely been unaware of the importance of floodplain structures and processes to the life requirements of a wide variety of species. We provide insight into gravel-bed rivers as the ecological nexus of glaciated mountain landscapes. We show why gravel-bed river floodplains are the primary arena where interactions take place among aquatic, avian, and terrestrial species from microbes to grizzly bears and provide essential connectivity as corridors for movement for both aquatic and terrestrial species. Paradoxically, gravel-bed river floodplains are also disproportionately unprotected where human developments are concentrated. Structural modifications to floodplains such as roads, railways, and housing and hydrologic-altering hydroelectric or water storage dams have severe impacts to floodplain habitat diversity and productivity, restrict local and regional connectivity, and reduce the resilience of both aquatic and terrestrial species, including adaptation to climate change. To be effective, conservation efforts in glaciated mountain landscapes intended to benefit the widest variety of organisms need a paradigm shift that has gravel-bed rivers and their floodplains as the central focus and that prioritizes the maintenance or restoration of the intact structure and processes of these critically important systems throughout their length and breadth.

Gravel-bed river floodplains are the ecological nexus of glaciated mountain landscapes

PubMed Central

Hauer, F. Richard; Locke, Harvey; Dreitz, Victoria J.; Hebblewhite, Mark; Lowe, Winsor H.; Muhlfeld, Clint C.; Nelson, Cara R.; Proctor, Michael F.; Rood, Stewart B.

2016-01-01

Gravel-bed river floodplains in mountain landscapes disproportionately concentrate diverse habitats, nutrient cycling, productivity of biota, and species interactions. Although stream ecologists know that river channel and floodplain habitats used by aquatic organisms are maintained by hydrologic regimes that mobilize gravel-bed sediments, terrestrial ecologists have largely been unaware of the importance of floodplain structures and processes to the life requirements of a wide variety of species. We provide insight into gravel-bed rivers as the ecological nexus of glaciated mountain landscapes. We show why gravel-bed river floodplains are the primary arena where interactions take place among aquatic, avian, and terrestrial species from microbes to grizzly bears and provide essential connectivity as corridors for movement for both aquatic and terrestrial species. Paradoxically, gravel-bed river floodplains are also disproportionately unprotected where human developments are concentrated. Structural modifications to floodplains such as roads, railways, and housing and hydrologic-altering hydroelectric or water storage dams have severe impacts to floodplain habitat diversity and productivity, restrict local and regional connectivity, and reduce the resilience of both aquatic and terrestrial species, including adaptation to climate change. To be effective, conservation efforts in glaciated mountain landscapes intended to benefit the widest variety of organisms need a paradigm shift that has gravel-bed rivers and their floodplains as the central focus and that prioritizes the maintenance or restoration of the intact structure and processes of these critically important systems throughout their length and breadth. PMID:27386570

Importance of floodplain connectivity to fish populations in the Apalachicola River, Florida

USGS Publications Warehouse

Burgess, O.T.; Pine, William E.; Walsh, S.J.

2013-01-01

Floodplain habitats provide critical spawning and rearing habitats for many large-river fishes. The paradigm that floodplains are essential habitats is often a key reason for restoring altered rivers to natural flow regimes. However, few studies have documented spatial and temporal utilization of floodplain habitats by adult fish of sport or commercial management interest or assessed obligatory access to floodplain habitats for species' persistence. In this study, we applied telemetry techniques to examine adult fish movements between floodplain and mainstem habitats, paired with intensive light trap sampling of larval fish in these same habitats, to assess the relationships between riverine flows and fish movement and spawning patterns in restored and unmodified floodplain distributaries of the Apalachicola River, Florida. Our intent is to inform resource managers on the relationships between the timing, magnitude and duration of flow events and fish spawning as part of river management actions. Our results demonstrate spawning by all study species in floodplain and mainstem river habitat types, apparent migratory movements of some species between these habitats, and distinct spawning events for each study species on the basis of fish movement patterns and light trap catches. Additionally, Micropterus spp., Lepomis spp. and, to a lesser degree, Minytrema melanops used floodplain channel habitat that was experimentally reconnected to the mainstem within a few weeks of completing the restoration. This result is of interest to managers assessing restoration activities to reconnect these habitats as part of riverine restoration programmes globally.

Channelization and floodplain forests: impacts of accelerated sedimentation and valley plug formation on floodplain forests of the Middle Fork Forked Deer River, Tennessee, USA

Treesearch

Sonja N. Oswalt; Sammy L. King

2005-01-01

We evaluated the severe degradation of floodplain habitats resulting from channelization and concomitant excessive coarse sedimentation on the Middle Fork Forked Deer River in west Tennessee from 2000 to 2003. Land use practices have resulted in excessive sediment in the tributaries and river system eventually resulting in sand deposition on the floodplain, increased...

2014 Reassessment of Floodplain Wetland Connections in the Middle Green River, Utah

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

LaGory, K. E.; Walston, L. J.; Weber, C. C.

This report presents the results of floodplain wetland connection surveys conducted in 2014 at six priority floodplain wetland sites along the middle Green River between Jensen and Ouray, Utah. Surveys were conducted at levee breaches and within channels leading from the breaches to the wetlands (referred to here as connection channels) to characterize the flows needed to connect the river’s main channel with the floodplain wetlands.

2012 Reassessment of Floodplain Wetland Connections in the Middle Green River, Utah

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

LaGory, Kirk E.; Walston, Leroy J.; Weber, Cory C.

This report presents the results of floodplain wetland connection surveys conducted in 2012 at eight priority floodplain wetlands along the middle Green River between Jensen and Ouray, Utah. Surveys were conducted at levee breaches and within channels leading from the breaches to the wetlands (referred to here as connection channels) to characterize the flows needed to connect the river's main channel with the floodplain wetlands.

Feedbacks between Reservoir Operation and Floodplain Development

NASA Astrophysics Data System (ADS)

Wallington, K.; Cai, X.

2017-12-01

The increased connectedness of socioeconomic and natural systems warrants the study of them jointly as Coupled Natural-Human Systems (CNHS) (Liu et al., 2007). One such CNHS given significant attention in recent years has been the coupled sociological-hydrological system of floodplains. Di Baldassarre et al. (2015) developed a model coupling floodplain development and levee heightening, a flood control measure, which demonstrated the "levee effect" and "adaptation effect" seen in observations. Here, we adapt the concepts discussed by Di Baldassarre et al. (2015) and apply them to floodplains in which the primary flood control measure is reservoir storage, rather than levee construction, to study the role of feedbacks between reservoir operation and floodplain development. Specifically, we investigate the feedback between floodplain development and optimal management of trade-offs between flood water conservation and flood control. By coupling a socio-economic model based on that of Di Baldassarre et al. (2015) with a reservoir optimization model based on that discussed in Ding et al. (2017), we show that reservoir operation rules can co-evolve with floodplain development. Furthermore, we intend to demonstrate that the model results are consistent with real-world data for reservoir operating curves and floodplain development. This model will help explain why some reservoirs are currently operated for purposes which they were not originally intended and thus inform reservoir design and construction.

Relationships between environmental conditions and the morphological variability of planktonic testate amoeba in four neotropical floodplains.

PubMed

Arrieira, Rodrigo Leite; Schwind, Leilane Talita Fatoreto; Joko, Ciro Yoshio; Alves, Geziele Mucio; Velho, Luiz Felipe Machado; Lansac-Tôha, Fábio Amodêo

2016-10-01

Planktonic testate amoebae in floodplains exhibit a broad-range of morphological variability. The variation size is already known, but it is necessary to know how this is for morphological variables. This study aimed to identify the relationships between testate amoebae morphology and environmental factors in four neotropical floodplains. We conducted detailed morphometric analyses on 27 common species of planktonic testate amoebae from genera Arcella, Centropyxis, Cucurbitella, Suiadifflugia, Difflugia, Lesquereusia and Netzelia. We sampled subsurface water from each lake in 72 lakes in four Brazilian floodplain lakes. Our goals were to assess: (1) the range of their morphological variability (a) over space within each floodplain, and (b) among the four floodplains, and (c) over time, and (2) which environmental factors explained this variation. Mean shell height and breadth varied considerably among the different floodplain lakes, especially in the Pantanal and Amazonian floodplains. The morphological variability of testate amoeba was correlated to environmental conditions (ammonia, nitrate, phosphate, chlorophyll-a, turbidity, temperature, and depth). Thus, understanding the morphological variation of the testate amoeba species can elucidate many questions involving the ecology of these organisms. Furthermore, could help molecular studies, bioindicator role of these organisations, environmental reconstruction, among others. Copyright © 2016 Elsevier GmbH. All rights reserved.

Abandoned floodplain plant communities along a regulated dryland river

USGS Publications Warehouse

Reynolds, L. V.; Shafroth, Patrick B.; House, P. K.

2014-01-01

Rivers and their floodplains worldwide have changed dramatically over the last century because of regulation by dams, flow diversions and channel stabilization. Floodplains no longer inundated by river flows following dam-induced flood reduction comprise large areas of bottomland habitat, but the effects of abandonment on plant communities are not well understood. Using a hydraulic flow model, geomorphic mapping and field surveys, we addressed the following questions along the Bill Williams River, Arizona: (i) What per cent of the bottomland do abandoned floodplains comprise? and (ii) Are abandoned floodplains quantitatively different from adjacent xeric and riparian surfaces in terms of vegetation composition and surface sediment? We found that nearly 70% of active channel and floodplain area was abandoned following dam installation. Abandoned floodplains along the Bill Williams River tend to be similar to each other yet distinct from neighbouring habitats: they have been altered physically from their historic state, leading to distinct combinations of surface sediments, hydrology and plant communities. Abandoned floodplains may transition to xeric communities over time but are likely to retain some riparian qualities as long as there is access to relatively shallow ground water. With expected increases in water demand and drying climatic conditions in many regions, these surfaces and associated vegetation will continue to be extensive in riparian landscapes worldwide

Floodplain Assessment for the Upper Cañon de Valle Watershed Enhancement Project in Technical Area 16 at Los Alamos National Laboratory

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

Hathcock, Charles Dean; Keller, David Charles; Sartor, Karla A.

This floodplain assessment was prepared in accordance with 10 Code of Federal Regulations (CFR) 1022 Compliance with Floodplain and Wetland Environmental Review Requirements, which was promulgated to implement the U.S. Department of Energy (DOE) requirements under Executive Order 11988 Floodplain Management and Executive Order 11990 Wetlands Protection. According to 10 CFR 1022, a 100-year floodplain is defined as “the lowlands adjoining inland and coastal waters and relatively flat areas and flood prone areas of offshore islands.” In this action, DOE is proposing to control the run-on of storm water by slowing water velocity and managing sediments from the upper portionsmore » of the Cañon de Valle watershed on Los Alamos National Laboratory (LANL) property with a number of new watershed controls near and within the 100-year floodplain (hereafter floodplain). The proposed work will comply with requirements under the Settlement Agreement and Stipulated Final Compliance Order (Settlement Agreement) Number HWB-14-20.« less

Geospatial assessment of ecological functions and flood-related risks on floodplains along major rivers in the Puget Sound Basin, Washington

USGS Publications Warehouse

Konrad, Christopher P.

2015-01-01

Ecological functions and flood-related risks were assessed for floodplains along the 17 major rivers flowing into Puget Sound Basin, Washington. The assessment addresses five ecological functions, five components of flood-related risks at two spatial resolutions—fine and coarse. The fine-resolution assessment compiled spatial attributes of floodplains from existing, publically available sources and integrated the attributes into 10-meter rasters for each function, hazard, or exposure. The raster values generally represent different types of floodplains with regard to each function, hazard, or exposure rather than the degree of function, hazard, or exposure. The coarse-resolution assessment tabulates attributes from the fine-resolution assessment for larger floodplain units, which are floodplains associated with 0.1 to 21-kilometer long segments of major rivers. The coarse-resolution assessment also derives indices that can be used to compare function or risk among different floodplain units and to develop normative (based on observed distributions) standards. The products of the assessment are available online as geospatial datasets (Konrad, 2015; http://dx.doi.org/10.5066/F7DR2SJC).

Using Random Forests to Map Floodplains for the Conterminous USA

EPA Science Inventory

Floodplains perform several important ecosystem services, including storing water during precipitation events and reducing peak flows, thereby reducing flooding of adjacent communities. Understanding the relationship between flood inundation and floodplains is critical for ecosys...

Floodplain Assessment for the North Ancho Canyon Aggregate Area Cleanup in Technical Area 39 at Los Alamos National Laboratory

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

Hathcock, Charles Dean

This floodplain assessment was prepared in accordance with 10 Code of Federal Regulations (CFR) 1022 Compliance with Floodplain and Wetland Environmental Review Requirements, which was promulgated to implement the U.S. Department of Energy (DOE) requirements under Executive Order 11988 Floodplain Management and Executive Order 11990 Wetlands Protection. According to 10 CFR 1022, a 100-year floodplain is defined as “the lowlands adjoining inland and coastal waters and relatively flat areas and flood prone areas of offshore islands.” In this action, DOE is proposing to collect soil investigation samples and remove contaminated soil within and around selected solid waste management units (SWMUs)more » near and within the 100-year floodplain (hereafter “floodplain”) in north Ancho Canyon at Los Alamos National Laboratory (LANL). The work is being performed to comply with corrective action requirements under the 2016 Compliance Order on Consent.« less

Water table and overbank flow frequency changes due to suburbanization-induced channel incision, Virginia Coastal Plain, USA

NASA Astrophysics Data System (ADS)

Hancock, G.; Mattell, N.; Christianson, E.; Wacksman, J.

2004-12-01

Channel incision is a widely observed response to increased flow in urbanized watersheds, but the effects of channel lowering on riparian water tables is not well documented. In a rapidly incising suburban stream in the Virginia Coastal Plain, we hypothesize that incision has lowered floodplain water tables and decreased the overbank flow frequency, and suggest these changes impact vegetation distribution in a diverse, protected riparian habitat. The monitored stream is a tributary to the James River draining 1.3 km2, of which 15% is impervious cover. Incision has occurred largely through upstream migration of a one m high knickpoint at a rate of 1-2 m/yr, primarily during high flow events. We installed 33 wells in six floodplain transects to assess water table elevations beneath the floodplain adjacent to the incising stream. To document the impacts of incision, two transects are located 30 and 50 m upstream of the knickpoint in unincised floodplain, and the remainder are 5, 30, 70, and 100 m downstream of the knickpoint in incised floodplain. In one transect above and two below, pressure transducers attached to dataloggers provide a high-resolution record of water table response to storm events. Significant differences have been observed in the water table above and below the knickpoint. Above the knickpoint, the water table is relatively flat and is 0.2-0.4 m below the floodplain surface. Water table response to precipitation events is nearly immediate, with the water table rising to the floodplain surface in significant rainfall events. In the transect immediately downstream of the knickpoint, the water table possesses a steep gradient, rising from ~1 m below the floodplain at the stream to 0.3 m below the surface within 20 m. In the most downstream transects, the water table is relatively flat, but is one m below the floodplain surface, equivalent to the depth of incision generated by knickpoint passage. Upstream of the knickpoint, overbank flooding occurs frequently, while below the knickpoint the majority of storm flow is contained within the incised channel and occupation of the floodplain is rare. Plant diversity surveys reveal differences in the total density of herbaceous growth and species distribution between the floodplain above and below the knickpoint. Results from >100 plots show that there is more leaf litter, less exposed ground, and a decrease in floodplain species cover in the incised portion of the floodplain. The changes in flood frequency and water table elevation appear to have allowed one invasive species, Japanese stilt grass (Microstegium vimineum), to become dominant in the floodplain understory, displacing native wetland species.

Floods, floodplains, delta plains — A satellite imaging approach

NASA Astrophysics Data System (ADS)

Syvitski, James P. M.; Overeem, Irina; Brakenridge, G. Robert; Hannon, Mark

2012-08-01

Thirty-three lowland floodplains and their associated delta plains are characterized with data from three remote sensing systems (AMSR-E, SRTM and MODIS). These data provide new quantitative information to characterize Late Quaternary floodplain landscapes and their penchant for flooding over the last decade. Daily proxy records for discharge since 2002 and for each of the 33 river systems can be derived with novel Advanced Microwave Scanning Radiometer (AMSR-E) methods. A descriptive framework based on analysis of Shuttle Radar Topography Mission (SRTM) data is used to capture the major landscape-scale floodplain elements or zones: 1) container valleys with their long and narrow pathways of largely sediment transit and bypass, 2) floodplain depressions that act as loci for frequent flooding and sediment storage, 3) zones of nodal avulsions common to many continental scale rivers, and often located seaward of container valleys, and 4) coastal floodplains and delta plains that offer both sediment bypass and storage but under the influence of marine processes. The SRTM data allow mapping of smaller-scale architectural elements in unprecedented systematic manner. Floodplain depressions were found to play a major role, which may largely be overlooked in conceptual floodplain models. Lastly, MODIS data (independently and combined with AMSR-E) allows the tracking of flood hydrographs and pathways and sedimentation patterns on a near-daily timescale worldwide. These remote-sensing data show that 85% of the studied major river systems experienced extensive flooding in the last decade. A new quantitative paradigm of floodplain processes, honoring the frequency and extent of floods, can be develop by careful analysis of these new remotely sensed data.

Hydrodynamic modeling of hydrologic surface connectivity within a coastal river-floodplain system

NASA Astrophysics Data System (ADS)

Castillo, C. R.; Guneralp, I.

2017-12-01

Hydrologic surface connectivity (HSC) within river-floodplain environments is a useful indicator of the overall health of riparian habitats because it allows connections amongst components/landforms of the riverine landscape system to be quantified. Overbank flows have traditionally been the focus for analyses concerned with river-floodplain connectivity, but recent works have identified the large significance from sub-bankfull streamflows. Through the use of morphometric analysis and a digital elevation model that is relative to the river water surface, we previously determined that >50% of the floodplain for Mission River on the Coastal Bend of Texas becomes connected to the river at streamflows well-below bankfull conditions. Guided by streamflow records, field-based inundation data, and morphometric analysis; we develop a two-dimensional hydrodynamic model for lower portions of Mission River Floodplain system. This model not only allows us to analyze connections induced by surface water inundation, but also other aspects of the hydrologic connectivity concept such as exchanges of sediment and energy between the river and its floodplain. We also aggregate hydrodynamic model outputs to an object/landform level in order to analyze HSC and associated attributes using measures from graph/network theory. Combining physically-based hydrodynamic models with object-based and graph theoretical analyses allow river-floodplain connectivity to be quantified in a consistent manner with measures/indicators commonly used in landscape analysis. Analyzes similar to ours build towards the establishment of a formal framework for analyzing river-floodplain interaction that will ultimately serve to inform the management of riverine/floodplain environments.

Fully integrated physically-based numerical modelling of impacts of groundwater extraction on surface and irrigation-induced groundwater interactions: case study Lower River Murray, Australia

NASA Astrophysics Data System (ADS)

Alaghmand, S.; Beecham, S.; Hassanli, A.

2013-07-01

Combination of reduction in the frequency, duration and magnitude of natural floods, rising saline water-table in floodplains and excessive evapotranspiration have led to an irrigation-induced groundwater mound forced the naturally saline groundwater onto the floodplain in the Lower River Murray. It is during the attenuation phase of floods that these large salt accumulations are likely to be mobilised and will discharge into the river. The Independent Audit Group for Salinity highlighted this as the most significant risk in the Murray-Darling Basin. South Australian government and catchment management authorities have developed salt interception schemes (SIS). This is to pump the highly saline groundwater from the floodplain aquifer to evaporation basins in order to reduce the hydraulic gradient that drives the regional saline groundwater towards the River Murray. This paper investigates the interactions between a river (River Murray in South Australia) and a saline semi-arid floodplain (Clarks Floodplain) significantly influenced by groundwater lowering (Bookpurnong SIS). Results confirm that groundwater extraction maintain a lower water-table and more fresh river water flux to the saline floodplain aquifer. In term of salinity, this may lead to less amount of solute stored in the floodplain aquifer. This occurs through two mechanisms; extracting some of the solute mass from the system and changing the floodplain groundwater regime from a losing to gaining one. Finally, it is shown that groundwater extraction is able to remove some amount of solute stored in the unsaturated zone and mitigate the floodplain salinity risk.

Cambrian rivers and floodplains: the significance of microbial cementation, groundwater and aeolian sediment transport

NASA Astrophysics Data System (ADS)

Reesink, A. J. H.; Best, J.; Freiburg, J. T.; Nathan, W.

2016-12-01

Rivers that existed before land plants colonized the Earth are commonly considered to be unaffected by microbial activity on their floodplains, because the limited cementation produced by microbial activity is insufficient to stabilize the river banks. Although this assumption is likely correct, such emphasis on channel dynamics ignores the potential role of floodplain dynamics as an integral component of the river system. Detailed analysis of cores from the Cambrian Mount Simon Sandstone, Illinois, suggests that a significant proportion of the terrestrial sequence is composed of flat-bedded `crinkly' structures that provide evidence of cementation by soil crusts and microbial biofilms, and that promoted the adhesion of sediment to sticky surfaces. Wind ripples and local desert pavements were abundant. These findings highlight that sediment deposition on Cambrian floodplains was often dominated by wind in locations where the ground water table reached the surface, and was thus likely independent of sediment transport within the river channel. Erosion by wind would thus have been hindered by surface cementation and the formation of desert pavements. Such ground water control on deposition, and resistance to erosion by floodplain surface hardening, appear to have been the primary controls on Cambrian floodplain topography. Because floodplain topography poses a key control on channel and floodplain flow, these processes may have affected patterns of erosion and deposition, as well as reach-scale dynamics such as channel avulsions. The autonomous operation of wind-and-groundwater controlled floodplains makes pre-vegetated river systems more sensitive to climatic conditions such as precipitation and evaporation, and strikingly different from those that occurred after the development of land plants.

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 erosion was exceeding floodplain sedimentation. In particular, the three segments between the existing dam and the confluence with the Conestoga River (32% of the studied reach) account for 97% of the measured net sediment budget. Future research directed at understanding channel equilibria should facilitate efforts to reduce the sediment impacts of dam removal and legacy sediment. ?? 2009 American Water Resources Association.

The influence of floodplain geomorphology and hydrologic connectivity on alligator gar (Atractosteus spatula) habitat along the embanked floodplain of the Lower Mississippi River

NASA Astrophysics Data System (ADS)

van der Most, Merel; Hudson, Paul F.

2018-02-01

The floodplain geomorphology of large lowland rivers is intricately related to aquatic ecosystems dependent upon flood pulse dynamics. The alligator gar (Atractosteus spatula) is native to the Lower Mississippi River and dependent upon floodplain backwater areas for spawning. In this study we utilize a geospatial approach to develop a habitat suitability index for alligator gar that explicitly considers hydrologic connectivity and the floodplain geomorphology along a frequently inundated segment of the Lower Mississippi River. The data sets include Landsat imagery, a high-resolution LiDAR digital elevation model (DEM), National Hydrography Dataset (NHD), and hydrologic and geomorphic data. A habitat suitability index is created based on the extent and frequency of inundation, water depth, temperature, and vegetation. A comparison between the remote sensing approach and the NHD revealed substantial differences in the area and location of water bodies available for alligator gar spawning. The final habitat suitability index indicates that a modest proportion (19%) of the overall embanked floodplain is available for alligator gar spawning. Opportunities exist for management efforts to utilize engineered and natural geomorphic features to facilitate hydrologic connectivity at flow levels below flood stage that would expand the habitat of alligator gar across the floodplain. The study results have direct implications regarding environmental restoration of the Lower Mississippi, an iconic example of an embanked meandering river floodplain.

Substantial soil organic carbon retention along floodplains of mountain streams

NASA Astrophysics Data System (ADS)

Sutfin, Nicholas A.; Wohl, Ellen

2017-07-01

Small, snowmelt-dominated mountain streams have the potential to store substantial organic carbon in floodplain sediment because of high inputs of particulate organic matter, relatively lower temperatures compared with lowland regions, and potential for increased moisture conditions. This work (i) quantifies mean soil organic carbon (OC) content along 24 study reaches in the Colorado Rocky Mountains using 660 soil samples, (ii) identifies potential controls of OC content based on soil properties and spatial position with respect to the channel, and (iii) and examines soil properties and OC across various floodplain geomorphic features in the study area. Stepwise multiple linear regression (adjusted r2 = 0.48, p < 0.001) indicates that percentage of silt and clay, sample depth, percent sand, distance from the channel, and relative elevation from the channel are significant predictors of OC content in the study area. Principle component analysis indicates limited separation between geomorphic floodplain features based on predictors of OC content. A lack of significant differences among floodplain features suggests that the systematic random sampling employed in this study can capture the variability of OC across floodplains in the study area. Mean floodplain OC (6.3 ± 0.3%) is more variable but on average greater than values in uplands (1.5 ± 0.08% to 2.2 ± 0.14%) of the Colorado Front Range and higher than published values from floodplains in other regions, particularly those of larger rivers.

Multiple effects of hydrological connectivity on floodplain processes in human modified river systems

NASA Astrophysics Data System (ADS)

Hein, Thomas; Bondar-Kunze, Elisabeth; Preiner, Stefan; Reckendorfer, Walter; Tritthart, Michael; Weigelhofer, Gabriele; Welti, Nina

2014-05-01

Floodplain and riparian ecosystems provide multiple functions and services of importance for human well-being and are of strategic importance for different sectors at catchment scale. Especially floodplains in the vicinity of urban areas can be areas of conflicting interests ranging from different land use types, flood water retention, drinking water production and recreation to conservation of last remnants of former riverine landscape, as it is the case in floodplains in the Danube Nationalpark downstream Vienna. Many of these ecosystem functions and services are controlled by the exchange conditions between river main channel and floodplain systems, the hydrological connectivity. At the same time these systems have been highly altered and especially the connectivity has been severely impaired. Thus, far ranging effects of changes in hydrological connectivity at various levels can be expected in altered floodplain systems. The aim of this presentation is to explore the complex control of different ecosystem functions and associated services by different parameters of hydrological connectivity, ranging from nutrient, sediment and matter dynamics and biodiversity aspects. Increasing connectivity will be shown to impact microbial dynamics, sediment-water interactions, carbon dynamics and trophic conditions, thus affecting the fundamental functions of particular floodplain systems at various spatial and temporal scales. Based on these changes also the provision of ecosystem services of floodplains is affected. The results clearly show that hydrological connectivity needs to be considered in a sustainable management approach.

Oxidation and reduction rates for organic carbon in the Amazon mainstream tributary and floodplain, inferred from distributions of dissolved gases

NASA Technical Reports Server (NTRS)

Richey, Jeffrey E.; Devol, Allan H.; Wofsy, Steven C.; Victoria, Reynaldo; Riberio, Maria N. G.

1986-01-01

Concentrations of CO2, O2, CH4, and N2O in the Amazon River system reflect an oxidation-reduction sequence in combination with physical mixing between the floodplain and the mainstem. Concentrations of CO2 ranged from 150 microM in the Amazon mainstem to 200 to 300 microM in aerobic waters of the floodplain, and up to 1000 microM in oxygen-depleted environments. Apparent oxygen utilization (AOU) ranged from 80 to 250 microM. Methane was highly supersaturated, with concentrations ranging from 0.06 microM in the mainstem to 100 microM on the floodplain. Concentrations of N2O were slightly supersaturated in the mainstem, but were undersaturated on the floodplain. Fluxes calculated from these concentrations indicated decomposition of 1600 g C sq m y(-1) of organic carbon in Amazon floodplain waters. Analysis of relationships between CH4, O2, and CO2 concentrations indicated that approximately 50 percent of carbon mineralization on the floodplain is anaerobic, with 20 percent lost to the atmoshphere as CH4. The predominance of anaerobic metabolism leads to consumption of N2O on the flood plane. Elevated concentrations of CH4 in the mainstem probably reflect imput from the floodplain, while high levels of CO2 in the mainstem are derived from a combination of varzea drainage and in situ respiration.

Coupling MAST-1D, a sediment routing model for channel-floodplain complexes, with channel migration relationships to predict reach-averaged river morphodynamics. Preliminary results

NASA Astrophysics Data System (ADS)

Viparelli, E.; Eke, E. C.; Lauer, J. W.

2017-12-01

Sediment exchange between the channel and floodplain can occur via meander migration, overbank deposition or erosion, and changes in channel geometry. Depending on channel and floodplain history, floodplains can act either as sources or sinks of bed material and/or wash load. Here we present preliminary modeling results that explicitly account for the feedbacks between the changes in floodplain geometry and sediment size distribution and the changes in channel geometry and migration. These results are obtained by coupling the Morphodynamics And Sediment Tracers in 1D (MAST-1D) program with the results of meander migration studies linking the bankfull flow depth and mean velocity to channel migration, sinuosity and channel geometry. MAST-1D is a numerical model built to describe grain size specific transport of sediment and tracers and the long-term - i.e. decadal and longer - evolution of channel floodplain complexes. MAST-1D differs from other 1D numerical models because it allows for 1) uneven exchange of sediment and tracers between the river channel and the floodplain, 2) temporal changes in channel geometry, bed elevation and floodplain thickness, which result in changes in the channel hydraulic capacity, and 3) temporal changes of size distribution and tracer content in the floodplain, in the load and in the underlying substrate. Under conditions of constant base level, water and sediment supply, the system evolves toward a steady state wherein the amount of sediment deposited through point bar deposition and overbank sedimentation is balanced by the erosion of sediment from the floodplain through lateral migration. The current formulation couples MAST-1D with empirical channel migration relationships that link bankfull flow depth and mean velocity to channel migration, sinuosity and channel geometry. Future development of this preliminary work will involve a fully coupled MAST-1D model with a standard meander migration model that will allow for the building of floodplain stratigraphy and tracking of the position of the meandering channel in space and time.

7 CFR 624.10 - Floodplain easements.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 7 Agriculture 6 2011-01-01 2011-01-01 false Floodplain easements. 624.10 Section 624.10 Agriculture Regulations of the Department of Agriculture (Continued) NATURAL RESOURCES CONSERVATION SERVICE, DEPARTMENT OF AGRICULTURE WATER RESOURCES EMERGENCY WATERSHED PROTECTION § 624.10 Floodplain easements. (a...

7 CFR 624.10 - Floodplain easements.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 7 Agriculture 6 2014-01-01 2014-01-01 false Floodplain easements. 624.10 Section 624.10 Agriculture Regulations of the Department of Agriculture (Continued) NATURAL RESOURCES CONSERVATION SERVICE, DEPARTMENT OF AGRICULTURE WATER RESOURCES EMERGENCY WATERSHED PROTECTION § 624.10 Floodplain easements. (a...

7 CFR 624.10 - Floodplain easements.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 7 Agriculture 6 2012-01-01 2012-01-01 false Floodplain easements. 624.10 Section 624.10 Agriculture Regulations of the Department of Agriculture (Continued) NATURAL RESOURCES CONSERVATION SERVICE, DEPARTMENT OF AGRICULTURE WATER RESOURCES EMERGENCY WATERSHED PROTECTION § 624.10 Floodplain easements. (a...

7 CFR 624.10 - Floodplain easements.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 6 2013-01-01 2013-01-01 false Floodplain easements. 624.10 Section 624.10 Agriculture Regulations of the Department of Agriculture (Continued) NATURAL RESOURCES CONSERVATION SERVICE, DEPARTMENT OF AGRICULTURE WATER RESOURCES EMERGENCY WATERSHED PROTECTION § 624.10 Floodplain easements. (a...

Identifying spatially integrated floodplains/riparian areas and wetlands

EPA Science Inventory

Floodplain delineation may play an important role in managing wetlands and riparian areas at multiple scales - local, state, and federal. This poster demonstrates multiple GIS-based approaches to delimiting floodplains and contrasts these with observed flooding events from a majo...

18 CFR 725.2 - Policy.

Code of Federal Regulations, 2010 CFR

2010-04-01

... ORDERS 11988, FLOODPLAIN MANAGEMENT AND 11990, PROTECTION OF WETLANDS Introduction § 725.2 Policy. It is the policy of the Council to provide leadership in floodplain management and the protection of... wetlands; (i) Involve the public throughout the floodplain management and wetlands protection...

40 CFR 258.11 - Floodplains.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Floodplains. 258.11 Section 258.11 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR MUNICIPAL...: (1) Floodplain means the lowland and relatively flat areas adjoining inland and coastal waters...

40 CFR 258.11 - Floodplains.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Floodplains. 258.11 Section 258.11 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR MUNICIPAL...: (1) Floodplain means the lowland and relatively flat areas adjoining inland and coastal waters...

40 CFR 258.11 - Floodplains.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Floodplains. 258.11 Section 258.11 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR MUNICIPAL...: (1) Floodplain means the lowland and relatively flat areas adjoining inland and coastal waters...

40 CFR 258.11 - Floodplains.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Floodplains. 258.11 Section 258.11 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR MUNICIPAL...: (1) Floodplain means the lowland and relatively flat areas adjoining inland and coastal waters...

40 CFR 258.11 - Floodplains.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Floodplains. 258.11 Section 258.11 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR MUNICIPAL...: (1) Floodplain means the lowland and relatively flat areas adjoining inland and coastal waters...

18 CFR 725.2 - Policy.

Code of Federal Regulations, 2014 CFR

2014-04-01

... ORDERS 11988, FLOODPLAIN MANAGEMENT AND 11990, PROTECTION OF WETLANDS Introduction § 725.2 Policy. It is the policy of the Council to provide leadership in floodplain management and the protection of... wetlands; (i) Involve the public throughout the floodplain management and wetlands protection...

18 CFR 725.2 - Policy.

Code of Federal Regulations, 2013 CFR

2013-04-01

... ORDERS 11988, FLOODPLAIN MANAGEMENT AND 11990, PROTECTION OF WETLANDS Introduction § 725.2 Policy. It is the policy of the Council to provide leadership in floodplain management and the protection of... wetlands; (i) Involve the public throughout the floodplain management and wetlands protection...

The long oasis: understanding and managing saline floodplains in southeastern Australia

NASA Astrophysics Data System (ADS)

Woods, J.; Green, G.; Laattoe, T.; Purczel, C.; Riches, V.; Li, C.; Denny, M.

2017-12-01

In a semi-arid region of southeastern Australia, the River Murray is the predominant source of freshwater for town water supply, irrigation, and floodplain ecosystems. The river interacts with aquifers where the salinity routinely exceeds 18,000 mg/l. River regulation, extraction, land clearance, and irrigation have reduced the size and frequency of floods while moving more salt into the floodplain. Floodplain ecosystem health has declined. Management options to improve floodplain health under these modified conditions include environmental watering, weirpool manipulation, and groundwater pumping. To benefit long-lived tree species, floodplain management needs to increase soil moisture availability. A conceptual model was developed of floodplain processes impacting soil moisture availability. The implications and limitations of the conceptualization were investigated using a series of numerical models, each of which simulated a subset of the processes under current and managed conditions. The aim was to determine what range of behaviors the models predicted, and to identify which parameters were key to accurately predicting the success of management options. Soil moisture availability was found to depend strongly on the properties of the floodplain clay, which controls vertical recharge during inundation. Groundwater freshening near surface water features depended on the riverbed conductivity and the penetration of the river into the floodplain sediments. Evapotranspiration is another critical process, and simulations revealed the limitations of standard numerical codes in environments where both evaporation and transpiration depend on salinity. Finally, maintenance of viable populations of floodplain trees is conceptually understood to rely on the persistence of adequate soil moisture availability over time, but thresholds for duration of exposure to low moisture availability that lead to decline and irreversible decline in tree condition are a major knowledge gap. The work identified critical data gaps which will be addressed in monitoring guidelines to improve management. This includes: hydrogeochemical sampling; in situ soil monitoring combined with tree health observations; monitoring of actual evapotranspiration; and monitoring of bores close to surface water sources.

Effects of Large Wood on River-Floodplain Connectivity in a Headwater Appalachian Stream

NASA Astrophysics Data System (ADS)

Keys, T.; Govenor, H.; Jones, C. N.; Hession, W. C.; Scott, D.; Hester, E. T.

2017-12-01

Large wood (LW) plays an important, yet often undervalued role in stream ecosystems. Traditionally, LW has been removed from streams for aesthetic, navigational, and flood mitigation purposes. However, extensive research over the last three decades has directly linked LW to critical ecosystem functions including habitat provisioning, stream geomorphic stability, and water quality improvements; and as such, LW has increasingly been implemented in stream restoration activities. One of the proposed benefits to this restoration approach is that LW increases river-floodplain connectivity, potentially decreasing downstream flood peaks and improving water quality. Here, we conducted two experiential floods (i.e., one with and one without LW) in a headwater, agricultural stream to explore the effect of LW on river-floodplain connectivity and resulting hydrodynamic processes. During each flood, we released an equal amount of water to the stream channel, measured stream discharge at upstream and downstream boundaries, and measured inundation depth at multiple locations across the floodplain. We then utilized a 2-dimensional hydrodynamic model (HEC-RAS) to simulate floodplain hydrodynamics. We first calibrated the model using observations from the two experimental floods. Then, we utilized the calibrated model to evaluate differing LW placement strategies and effects under various flow conditions. Results show that the addition of LW to the channel decreased channel velocity and increased inundation extent, inundation depth, and floodplain velocity. Differential placement of LW along the stream impacted the levels of floodplain discharge, primarily due to the geomorphic characteristics of the stream. Finally, we examined the effects of LW on floodplain hydrodynamics across a synthetic flow record, and found that the magnitude of river-floodplain connectivity decreased as recurrence interval increased, with limited impacts on storm events with a recurrence interval of 25 years or greater. These findings suggest that LW plays a substantial role in river-floodplain connectivity of headwater streams and associated ecosystem services.

Floodplains as a source of fine sediment in grazed landscapes: Tracing the source of suspended sediment in the headwaters of an intensively managed agricultural landscape

NASA Astrophysics Data System (ADS)

Yu, Mingjing; Rhoads, Bruce L.

2018-05-01

The flux of fine sediment within agricultural watersheds is an important factor determining the environmental quality of streams and rivers. Despite this importance, the contributions of sediment sources to suspended sediment loads within intensively managed agricultural watersheds remain poorly understood. This study assesses the provenance of fine suspended sediment in the headwater portion of a river flowing through an agricultural landscape in Illinois. Sediment source samples were collected from five sources: croplands, forested floodplains, grasslands, upper grazed floodplains, and lower grazed floodplains. Event-based and aggregated suspended sediment samples were collected from the stream at the watershed outlet. Quantitative geochemical fingerprinting techniques and a mixing model were employed to estimate the relative contributions of sediment from the five sources to the suspended sediment loads. To account for possible effects of small sample sizes, the analysis was repeated with only two sources: grazed floodplains and croplands/grasslands/forested floodplains. Results based on mean values of tracers indicate that the vast majority of suspended sediment within the stream (>95%) is derived from erosion of channel banks and the soil surface within areas of grazed floodplains. Uncertainty analysis based on Monte Carlo simulations indicates that mean values of tracer properties, which do not account for sampling variability in these properties, probably overestimate contributions from the two major sources. Nevertheless, this analysis still supports the conclusion that floodplain erosion accounts for the largest percentage of instream sediment (≈55-75%). Although grazing occurs over only a small portion of the total watershed area, grazed floodplains, which lie in close proximity to the stream channel, are an important source of sediment in this headwater steam system. Efforts to reduce fluxes of fine sediment in this intensively managed landscape should focus on eroding floodplain surfaces and channel banks within heavily grazed reaches of the stream.

Testing the skill of numerical hydraulic modeling to simulate spatiotemporal flooding patterns in the Logone floodplain, Cameroon

NASA Astrophysics Data System (ADS)

Fernández, Alfonso; Najafi, Mohammad Reza; Durand, Michael; Mark, Bryan G.; Moritz, Mark; Jung, Hahn Chul; Neal, Jeffrey; Shastry, Apoorva; Laborde, Sarah; Phang, Sui Chian; Hamilton, Ian M.; Xiao, Ningchuan

2016-08-01

Recent innovations in hydraulic modeling have enabled global simulation of rivers, including simulation of their coupled wetlands and floodplains. Accurate simulations of floodplains using these approaches may imply tremendous advances in global hydrologic studies and in biogeochemical cycling. One such innovation is to explicitly treat sub-grid channels within two-dimensional models, given only remotely sensed data in areas with limited data availability. However, predicting inundated area in floodplains using a sub-grid model has not been rigorously validated. In this study, we applied the LISFLOOD-FP hydraulic model using a sub-grid channel parameterization to simulate inundation dynamics on the Logone River floodplain, in northern Cameroon, from 2001 to 2007. Our goal was to determine whether floodplain dynamics could be simulated with sufficient accuracy to understand human and natural contributions to current and future inundation patterns. Model inputs in this data-sparse region include in situ river discharge, satellite-derived rainfall, and the shuttle radar topography mission (SRTM) floodplain elevation. We found that the model accurately simulated total floodplain inundation, with a Pearson correlation coefficient greater than 0.9, and RMSE less than 700 km2, compared to peak inundation greater than 6000 km2. Predicted discharge downstream of the floodplain matched measurements (Nash-Sutcliffe efficiency of 0.81), and indicated that net flow from the channel to the floodplain was modeled accurately. However, the spatial pattern of inundation was not well simulated, apparently due to uncertainties in SRTM elevations. We evaluated model results at 250, 500 and 1000-m spatial resolutions, and found that results are insensitive to spatial resolution. We also compared the model output against results from a run of LISFLOOD-FP in which the sub-grid channel parameterization was disabled, finding that the sub-grid parameterization simulated more realistic dynamics. These results suggest that analysis of global inundation is feasible using a sub-grid model, but that spatial patterns at sub-kilometer resolutions still need to be adequately predicted.

Spatial patterns of aquatic habitat richness in the Upper Mississippi River floodplain, USA

USGS Publications Warehouse

De Jager, Nathan R.; Rohweder, Jason J.

2012-01-01

Interactions among hydrology and geomorphology create shifting mosaics of aquatic habitat patches in large river floodplains (e.g., main and side channels, floodplain lakes, and shallow backwater areas) and the connectivity among these habitat patches underpins high levels of biotic diversity and productivity. However, the diversity and connectivity among the habitats of most floodplain rivers have been negatively impacted by hydrologic and structural modifications that support commercial navigation and control flooding. We therefore tested the hypothesis that the rate of increase in patch richness (# of types) with increasing scale reflects anthropogenic modifications to habitat diversity and connectivity in a large floodplain river, the Upper Mississippi River (UMR). To do this, we calculated the number of aquatic habitat patch types within neighborhoods surrounding each of the ≈19 million 5-m aquatic pixels of the UMR for multiple neighborhood sizes (1–100 ha). For all of the 87 river-reach focal areas we examined, changes in habitat richness (R) with increasing neighborhood length (L, # pixels) were characterized by a fractal-like power function R = Lz (R2 > 0.92 (P z) measures the rate of increase in habitat richness with neighborhood size and is related to a fractal dimension. Variation in z reflected fundamental changes to spatial patterns of aquatic habitat richness in this river system. With only a few exceptions, z exceeded the river-wide average of 0.18 in focal areas where side channels, contiguous floodplain lakes, and contiguous shallow-water areas exceeded 5%, 5%, and 10% of the floodplain respectively. In contrast, z was always less than 0.18 for focal areas where impounded water exceeded 40% of floodplain area. Our results suggest that rehabilitation efforts that target areas with <5% of the floodplain in side channels, <5% in floodplain lakes, and/or <10% in shallow-water areas could improve habitat diversity across multiple scales in the UMR.

Water Storage Changes using Floodplain Bathymetry from InSAR and satellite altimetry in the Congo River Basin

NASA Astrophysics Data System (ADS)

Yuan, T.; Lee, H.; Jung, H. C.; Beighley, E.; Alsdorf, D. E.

2016-12-01

Extensive wetlands and swamps expand along the Congo River and its tributaries. These wetlands store water and attenuate flood wave during high water season. Substantial dissolved and solid substances are also transported with the water flux, influencing geochemical environment and biogeochemistry processes both in the wetlands and the river. To understand the role of the wetlands in partitioning the surface water and the accompanied material movement, water storage change is one of the most fundamental observations. The water flow through the wetlands is complex, affected by topography, vegetation resistance, and hydraulic variations. Interferometric Synthetic Aperture Radar (InSAR) has been successfully used to map relative water level changes in the vegetated wetlands with high spatial resolution. By examining interferograms generated from ALOS PALSAR along the middle reach of the Congo River floodplain, we found greater water level changes near the Congo mainstem. Integrated analysis of InSAR and Envisat altimetry data has shown that proximal floodplain with higher water level change has lower elevation during dry season. This indicates that the spatial variation of water level change in the Congo floodplain is mostly controlled by floodplain bathymetry. A method based on water level and bathymetry model is proposed to estimate water storage change. The bathymetry model is composed of (1) elevation at the intersection of the floodplain and the river and (2) floodplain bathymetry slope. We first constructed the floodplain bathymetry by selecting an Envisat altimetry profile during low water season to estimate elevation at the intersection of the floodplain and the river. Floodplain bathymetry slope was estimated using InSAR measurements. It is expected that our new method can estimate water storage change with higher temporal resolution corresponding to altimeter's repeat cycle. In addition, given the multi-decadal archive of satellite altimetry measurements, our method suggests a way to estimate interannual water storage change over a long time span in Congo.

Geomorphic controls on floodplain organic carbon storage in sediment along five rivers in interior Alaska

NASA Astrophysics Data System (ADS)

Lininger, K.; Wohl, E.; Rose, J. R.

2016-12-01

High latitude permafrost regions contain large amounts of organic carbon (OC) in the subsurface, but little work has quantified OC storage in floodplain sediment in the high latitudes. Floodplains influence the export of OC to the ocean by temporarily storing OC at timescales of 101 to 103 years. To fully understand terrestrial carbon cycling, the storage and residence time of OC in floodplains, and the geomorphic controls on OC storage, must be taken into account. Small-scale spatial variations in OC storage within floodplains likely reflect geomorphic processes of deposition and floodplain development. We present results of floodplain OC storage and residence time in sediment along 5 rivers in the Yukon Flats National Wildlife Refuge in interior Alaska, a region with discontinuous permafrost. We collected sediment samples within the active layer along tributaries to the Yukon River and the mainstem Yukon River and analyzed the sediment samples for OC content. We classified sample locations by geomorphic type (filled secondary channels, levees, point bars) and vegetation type (herbaceous, deciduous/shrub, white spruce, and black spruce wetlands), and found that both geomorphology and vegetation influence OC concentration and OC mass per area. Preliminary results suggest that filled secondary channels contain more OC per area compared to other geomorphic types. We present results of radiocarbon dates from river cutbanks associated with our sampling sites, which give a maximum age for residence times of OC in sediment before erosion and transport. The radiocarbon dates also provide estimates of long-term OC accretion within the Yukon Flats floodplains. Small-scale variations within floodplains as a result of floodplain depositional processes and vegetation communities shed light on the geomorphic controls on OC storage. This work will help constrain the spatial variation in OC storage and OC residence time across the landscape in a region experiencing rapid climate change and permafrost thaw.

Spatial relationships of levees and wetland systems within floodplains of the Wabash Basin, USA

NASA Astrophysics Data System (ADS)

Bray, E. N.; Morrison, R. R.; Nardi, F.; Annis, A.; Dong, Q.

2017-12-01

Given the unique biogeochemical, physical, and hydrologic services provided by floodplain wetlands, proper management of river systems should include an understanding of how floodplain modifications influences wetland ecosystems. The construction of levees can reduce river-floodplain connectivity, yet it is unclear how levees affect wetlands within a river system, let alone the cumulative impacts within an entire watershed. This paper explores spatial relationships between levee and floodplain wetland systems in the Wabash basin, United States. We used a hydrogeomorphic floodplain delineation technique to map floodplain extents and identify wetlands that may be hydrologically connected to river networks. We then spatially examined the relationship between levee presence, wetland area, and other river network attributes within discrete HUC-12 sub-basins. Our results show that cumulative wetland area is relatively constant in sub-basins that contain levees, regardless of maximum stream order within the sub-basin. In sub-basins that do not contain levees, cumulative wetland area increases with maximum stream order. However, we found that wetland distributions around levees can be complex, and further studies on the influence of levees on wetland habitat may need to be evaluated at finer-resolution spatial scales.

Floodplain Connectivity and implications for flooding and floodplain function

NASA Astrophysics Data System (ADS)

Barrow, E.

2017-12-01

Regime theory suggests that floodplains should be inundated on average once every two years to maintain form and function of both the river and the floodplain. Natural disconnection along non-alluvial reaches and where the river has moved to flow against terrace edges is to be expected, however, disconnectivity caused by river management is now affecting increasing lengths of watercourses. This study utilises aerial Lidar data to determine the relative height difference between the watercourse and adjacent valley bottoms to assess the degree of disconnectivity along main river systems across Cumbria in the UK. The results reveal that many rivers are now poorly connected to their floodplains which are now largely non-functional. Floodplain geomorphic units, although often present, are currently inactive and water table levels are reduced resulting in a loss of wetland in favour of ruderal species tolerant of drier conditions. The causes of such widespread disconnectivity may be attributed to historic dredging and straightening of these rivers and revetment and riparian tree planting has further exacerbated the problem restricting lateral activity and the subsequent development of new areas of connected floodplain. The high degree of disconnection has implications for future river management and river restoration and these are discussed.

28 CFR 63.2 - Policy.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Administration DEPARTMENT OF JUSTICE (CONTINUED) FLOODPLAIN MANAGEMENT AND WETLAND PROTECTION PROCEDURES § 63.2... term adverse impacts associated with the destruction or modification of wetlands and floodplains and to avoid direct or indirect support of new construction in floodplains and wetlands whenever there is a...

28 CFR 63.2 - Policy.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Administration DEPARTMENT OF JUSTICE (CONTINUED) FLOODPLAIN MANAGEMENT AND WETLAND PROTECTION PROCEDURES § 63.2... term adverse impacts associated with the destruction or modification of wetlands and floodplains and to avoid direct or indirect support of new construction in floodplains and wetlands whenever there is a...

28 CFR 63.2 - Policy.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Administration DEPARTMENT OF JUSTICE (CONTINUED) FLOODPLAIN MANAGEMENT AND WETLAND PROTECTION PROCEDURES § 63.2... term adverse impacts associated with the destruction or modification of wetlands and floodplains and to avoid direct or indirect support of new construction in floodplains and wetlands whenever there is a...

28 CFR 63.2 - Policy.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Administration DEPARTMENT OF JUSTICE (CONTINUED) FLOODPLAIN MANAGEMENT AND WETLAND PROTECTION PROCEDURES § 63.2... term adverse impacts associated with the destruction or modification of wetlands and floodplains and to avoid direct or indirect support of new construction in floodplains and wetlands whenever there is a...

18 CFR 725.7 - Regional or river basin planning.

Code of Federal Regulations, 2011 CFR

2011-04-01

... preservation and restoration of natural and beneficial floodplain values; (4) Where avoidance of wetlands... IMPLEMENTATION OF EXECUTIVE ORDERS 11988, FLOODPLAIN MANAGEMENT AND 11990, PROTECTION OF WETLANDS... whether proposed activities would be located in floodplains or wetlands, or, even if located outside of...

Low elevation inland habitats of the Willamette River floodplain support enhanced denitrification

EPA Science Inventory

Floodplain nitrate removal via denitrification in sediment provides an important ecosystem service that may be a valuable sink for nitrate pollution. At this time, much floodplain restoration is taking place with little consideration for in-situ nutrient processing, necessitating...

Low Elevation Old Channel Features of the Willamette River Floodplain Support High Subsurface Denitrification Rates

EPA Science Inventory

Background/Question/Methods: Large river floodplains are poor nitrate pollution buffers when polluted groundwater moves beneath biogeochemically retentive zones prior to entering the main channel. However, in floodplain regions with extensive backwaters and organic carbon acc...

Inventory of Rare or Endangered Non-Vascular Plants and Ferns Occurring in the Floodplain of the Mississippi River between Cairo, Illinois, and St. Paul, Minnesota, and in the Floodplain of the Illinois River between Grafton, Illinois, and Chicago,

DTIC Science & Technology

1975-02-03

3 Liverworts and Horworts ------------------ 4 Lichens -------------------------------- 4 Ferns ------------------------------- 5 Algae of the...Mississippi River and Illinois River Floodplains ----- 6 Mosses of the Mississippi River and Illinois River Floodplains--- 35 Liverworts and Hornworts...any alga, hornwort, liverwort , moss, or lichen in the study area. Missouri (1974) lists some mosses which are designated 0 rare or endangered, but

Interactions among hydrogeomorphology, vegetation, and nutrient biogeochemistry in floodplain ecosystems

USGS Publications Warehouse

Noe, G.B.; Shroder, John F.

2013-01-01

Hydrogeomorphic, vegetative, and biogeochemical processes interact in floodplains resulting in great complexity that provides opportunities to better understand linkages among physical and biological processes in ecosystems. Floodplains and their associated river systems are structured by four-dimensional gradients of hydrogeomorphology: longitudinal, lateral, vertical, and temporal components. These four dimensions create dynamic hydrologic and geomorphologic mosaics that have a large imprint on the vegetation and nutrient biogeochemistry of floodplains. Plant physiology, population dynamics, community structure, and productivity are all very responsive to floodplain hydrogeomorphology. The strength of this relationship between vegetation and hydrogeomorphology is evident in the use of vegetation as an indicator of hydrogeomorphic processes. However, vegetation also influences hydrogeomorphology by modifying hydraulics and sediment entrainment and deposition that typically stabilize geomorphic patterns. Nitrogen and phosphorus biogeochemistry commonly influence plant productivity and community composition, although productivity is not limited by nutrient availability in all floodplains. Conversely, vegetation influences nutrient biogeochemistry through direct uptake and storage as well as production of organic matter that regulates microbial biogeochemical processes. The biogeochemistries of nitrogen and phosphorus cycling are very sensitive to spatial and temporal variation in hydrogeomorphology, in particular floodplain wetness and sedimentation. The least-studied interaction is the direct effect of biogeochemistry on hydrogeomorphology, but the control of nutrient availability over organic matter decomposition and thus soil permeability and elevation is likely important. Biogeochemistry also has the more documented but indirect control of hydrogeomorphology through regulation of plant biomass. In summary, the defining characteristics of floodplain ecosystems are determined by the many interactions among physical and biological processes. Conservation and restoration of the valuable ecosystem services that floodplains provide depend on improved understanding and predictive models of interactive system controls and behavior.

A geomorphic approach to 100-year floodplain mapping for the Conterminous United States

NASA Astrophysics Data System (ADS)

Jafarzadegan, Keighobad; Merwade, Venkatesh; Saksena, Siddharth

2018-06-01

Floodplain mapping using hydrodynamic models is difficult in data scarce regions. Additionally, using hydrodynamic models to map floodplain over large stream network can be computationally challenging. Some of these limitations of floodplain mapping using hydrodynamic modeling can be overcome by developing computationally efficient statistical methods to identify floodplains in large and ungauged watersheds using publicly available data. This paper proposes a geomorphic model to generate probabilistic 100-year floodplain maps for the Conterminous United States (CONUS). The proposed model first categorizes the watersheds in the CONUS into three classes based on the height of the water surface corresponding to the 100-year flood from the streambed. Next, the probability that any watershed in the CONUS belongs to one of these three classes is computed through supervised classification using watershed characteristics related to topography, hydrography, land use and climate. The result of this classification is then fed into a probabilistic threshold binary classifier (PTBC) to generate the probabilistic 100-year floodplain maps. The supervised classification algorithm is trained by using the 100-year Flood Insurance Rated Maps (FIRM) from the U.S. Federal Emergency Management Agency (FEMA). FEMA FIRMs are also used to validate the performance of the proposed model in areas not included in the training. Additionally, HEC-RAS model generated flood inundation extents are used to validate the model performance at fifteen sites that lack FEMA maps. Validation results show that the probabilistic 100-year floodplain maps, generated by proposed model, match well with both FEMA and HEC-RAS generated maps. On average, the error of predicted flood extents is around 14% across the CONUS. The high accuracy of the validation results shows the reliability of the geomorphic model as an alternative approach for fast and cost effective delineation of 100-year floodplains for the CONUS.

Soil greenhouse gas emissions and carbon budgeting in a short-hydroperiod floodplain wetland

NASA Astrophysics Data System (ADS)

Batson, Jackie; Noe, Gregory B.; Hupp, Cliff R.; Krauss, Ken W.; Rybicki, Nancy B.; Schenk, Edward R.

2015-01-01

Understanding the controls on floodplain carbon (C) cycling is important for assessing greenhouse gas emissions and the potential for C sequestration in river-floodplain ecosystems. We hypothesized that greater hydrologic connectivity would increase C inputs to floodplains that would not only stimulate soil C gas emissions but also sequester more C in soils. In an urban Piedmont river (151 km2 watershed) with a floodplain that is dry most of the year, we quantified soil CO2, CH4, and N2O net emissions along gradients of floodplain hydrologic connectivity, identified controls on soil aerobic and anaerobic respiration, and developed a floodplain soil C budget. Sites were chosen along a longitudinal river gradient and across lateral floodplain geomorphic units (levee, backswamp, and toe slope). CO2 emissions decreased downstream in backswamps and toe slopes and were high on the levees. CH4 and N2O fluxes were near zero; however, CH4 emissions were highest in the backswamp. Annual CO2 emissions correlated negatively with soil water-filled pore space and positively with variables related to drier, coarser soil. Conversely, annual CH4 emissions had the opposite pattern of CO2. Spatial variation in aerobic and anaerobic respiration was thus controlled by oxygen availability but was not related to C inputs from sedimentation or vegetation. The annual mean soil CO2 emission rate was 1091 g C m-2 yr-1, the net sedimentation rate was 111 g C m-2 yr-1, and the vegetation production rate was 240 g C m-2 yr-1, with a soil C balance (loss) of -338 g C m-2 yr-1. This floodplain is losing C likely due to long-term drying from watershed urbanization.

Interactions among hydrogeomorphology, vegetation, and nutrient biogeochemistry in floodplain ecosystems

USGS Publications Warehouse

Noe, G.B.

2013-01-01

Hydrogeomorphic, vegetative, and biogeochemical processes interact in floodplains resulting in great complexity that provides opportunities to better understand linkages among physical and biological processes in ecosystems. Floodplains and their associated river systems are structured by four dimensional gradients of hydrogeomorphology: longitudinal, lateral, vertical, and temporal components. These four dimensions create dynamic hydrologic and geomorphologic mosaics that have a large imprint on the vegetation and nutrient biogeochemistry of floodplains. Plant physiology, population dynamics, community structure, and productivity are all very responsive to floodplain hydrogeomorphology. The strength of this relationship between vegetation and hydrogeomorphology is evident in the use of vegetation as an indicator of hydrogeomorphic processes. However, vegetation also influences hydrogeomorphology by modifying hydraulics and sediment entrainment and deposition that typically stabilize geomorphic patterns. Nitrogen and phosphorus biogeochemistry commonly influence plant productivity and community composition, although productivity is not limited by nutrient availability in all floodplains. Conversely, vegetation influences nutrient biogeochemistry through direct uptake and storage as well as production of organic matter that regulates microbial biogeochemical processes. The biogeochemistries of nitrogen and phosphorus cycling are very sensitive to spatial and temporal variation in hydrogeomorphology, in particular floodplain wetness and sedimentation. The least studied interaction is the direct effect of biogeochemistry on hydrogeomorphology, but the control of nutrient availability over organic matter decomposition and thus soil permeability and elevation is likely important. Biogeochemistry also has the more documented but indirect control of hydrogeomorphology through regulation of plant biomass. In summary, the defining characteristics of floodplain ecosystems are determined by the many interactions among physical and biological processes. Conservation and restoration of the valuable ecosystem services that floodplains provide depends on improved understanding and predictive models of interactive system controls and behavior.

Sediment Retention Dynamics and Vegetation Along Three Tributaries of the Chesapeake Bay

NASA Astrophysics Data System (ADS)

Ross, K.; Ross, K.; Hupp, C.; Alexander, L.; Alexander, L.

2001-12-01

Coastal Plain riparian wetlands in the Mid-Atlantic United States are the last place for sediment and contaminant storage before reaching critical estuarine and marine environments. The deteriorating health of the Chesapeake Bay has been attributed in part to elevated sediment loads. The purpose of this study is to investigate the effects of channelization and urbanization on sediment deposition and geomorphic processes along the Pocomoke and Chickahominy Rivers and Dragon Run, three Coastal Plain tributaries. Floodplain microtopography was surveyed in 100 x 100 m grids at three characteristic reaches along each river and woody vegetation analyses were conducted. Floodplain suspended sediment concentrations and short and long-term sedimentation rates were estimated at each reach using single stage sediment sampler arrays, clay pads and dendrogeomorphic techniques, respectively. Site hydroperiod and flow characteristics were determined from USGS gaging station records, floodplain water level recorders, and field observations. Channelized floodplain reaches along the Pocomoke River are flooded less frequently, have lower mineral sedimentation rates (2 mm/yr to 6 mm/yr) and woody species diversity than the unchannelized reaches. Along the Chickahominy River, floodplain wetlands close to urban centers are flooded more frequently, but have shorter hydroperiods (3.5 days/yr compared to more than 45 days/yr), lower sedimentation rates (1.8 mm/yr to 6.8 mm/yr), and lower woody species diversity (0.51 to 1.95 on the Shannon-Weiner diversity index) than floodplains further downstream. Suspended sediment delivery and deposition rates are significantly influenced by floodplain hydroperiod duration and channel-floodplain connectivity. These results suggest that understanding floodplain sediment dynamics and geomorphic processes with respect to dominant watershed landuse patterns is critical for effective water quality management and restoration efforts.

Connectivity of Secondary Channels in the Floodplain of a Low-Gradient Midwestern U.S. Agricultural River

NASA Astrophysics Data System (ADS)

Czuba, J. A.; David, S. R.; Edmonds, D. A.

2016-12-01

Floodplains of low-gradient Midwestern U.S. agricultural rivers are commonly dissected by a network of secondary channels that convey flow only during flood events. These networks of secondary channels have only recently been revealed by high resolution digital elevation models. Secondary channels, as referred to here, span multiple meander wavelengths and appear fundamentally different from chute channels. While secondary channels have been described to some extent in other river systems, our focus here is on those found in Indiana, which are revealed by state-wide LiDAR data acquired in 2011. In this work, we quantify how the network connectivity of the secondary channels in the floodplain develops as a function of flow stage. Secondary channels begin conveying water at stages just below bankfull, become an interconnected web of flow pathways above bankfull stage, and are completely inundated at higher stages. We construct a two-dimensional numerical model of the river/floodplain system from LiDAR data and from main-channel river bathymetry in order to obtain the extent of floodplain inundation at various flows. The inundated area within the secondary channels is then converted into a river/floodplain flow-channel network and quantified using various network metrics. Future work will explore the morphodynamics of this river/floodplain system extended to 100-1,000 year timescales. The goal is to develop a simple model to test hypotheses about how these floodplain channels evolve. Relevant research questions include: do secondary channels serve as preferential avulsion pathways? Or could secondary channels evolve to create a multi-channeled anabranching system? Furthermore, under what hydrologic and sedimentologic conditions would a river/floodplain system evolve to one state or another?

Hydrological, Physical, and Chemical Functions and Connectivity of Non‐Floodplain Wetlands to Downstream Waters: A Review

EPA Science Inventory

We reviewed the scientific literature on non‐floodplain wetlands (NFWs), freshwater wetlands typically located distal to riparian and floodplain systems, to determine hydrological, physical, and chemical functioning and stream and river network connectivity. We assayed the ...

10 CFR 1022.4 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-01-01

... ENERGY (GENERAL PROVISIONS) COMPLIANCE WITH FLOODPLAIN AND WETLAND ENVIRONMENTAL REVIEW REQUIREMENTS... DOE action in a wetland that is also within the floodplain, subject to the exclusions specified at § 1022.5(c) and (d) of this part. Floodplain and wetland values means the qualities of or functions...

Floodplain restoration increases hyporheic flow in the Yakima River Watershed, Washington

EPA Science Inventory

Hyporheic exchange between a river channel and its floodplain region assists in mediating processes such as nutrient removal and temperature regulation. Floodplain restoration in the form of levee setbacks are often carried out to improve the hyporheic exchange. In this study Lig...

24 CFR 55.27 - Documentation.

Code of Federal Regulations, 2010 CFR

2010-04-01

... FLOODPLAIN MANAGEMENT Procedures for Making Determinations on Floodplain Management § 55.27 Documentation. (a... outside the floodplain, but within the local housing market area, the local public utility service area..., documentation of compliance with this part must be included as a part of the record of decision (or...

How does floodplain width affect floodplain river ecology? A preliminary exploration using simulations

NASA Astrophysics Data System (ADS)

Power, Mary E.; Parker, Gary; Dietrich, William E.; Sun, Adrian

1995-09-01

Hydraulic food chain models allow us to explore the linkages of river discharge regimes and river-floodplain morphology to the structure and dynamics of modeled food webs. Physical conditions (e.g. depth, width, velocity) that vary with river discharge affect the performance (birth, growth, feeding, movement, or death rates) of organisms or trophic groups. Their performances in turn affect their impacts on food webs and ecosystems in channel and floodplain habitats. Here we explore the impact of floodplain width (modeled as 1 ×, 10× and 40× the channel width) on a food web with two energy sources (detritus and vegetation), invertebrates that consume these, a size structured fish population which consumes invertebrates and in which larger fish cannibalize small fish, and birds which feed on large fish. Hydraulic linkages to trophic dynamics are assumed to be mediated in three ways: birds feed efficiently only in shallow water; plant carrying capacity varies non-linearly with water velocity, and mobile and drifting organisms are diluted and concentrated with spillover of river discharge to the floodplain, and its reconfinement to the channel. Aspects of this model are based on field observations of Junk and Bailey from the Amazon, of Sparks from the Mississippi, and on our observations of the Fly River in Papua New Guinea. The model produced several counter-intuitive results. Biomass of invertebrates and fish increased with floodplain width, but much more rapidly from 1 × to 10 × floodplains than from 10 × to 40 × floodplains. For birds, maximum biomass occurred on the 10× floodplain. Initially high bird biomass on the 40 × floodplain declined to extinction over time, because although favorable fishing conditions (shallow water) were most prolonged on the widest floodplain, this advantage was more than offset by the greater dilution of prey after spillover. Bird predation on large fish sometimes increased their biomass, by reducing cannibalism and thereby increasing the abundance of small fish available to grow into the larger size class. Sensitivity analyses indicated that model results were relatively robust to variation in parameter values that we chose, but much more exploration and calibration with field data are needed before we know how specific our results are to the structure and other assumptions of this model. We share with others the opinion that progress towards understanding complex dynamic systems like floodplain river ecosystems requires frequent feedback between modeling and field observations and experimentation. This understanding is crucial for river management and restoration. Organisms in real rivers have adapted to track and quickly exploit favorable conditions, and to avoid or endure adverse conditions. It is when we engineer away this environmental variability that we threaten the long term persistence of river-adapted biota.

A numerical investigation of the impacts of river and floodplain restoration on the process of floodwave attenuation

NASA Astrophysics Data System (ADS)

Stone, M. C.; Byrne, C.; Morrison, R.

2015-12-01

It is widely recognized that past river engineering, flood control, and floodplain development activities have tended to work against nature rather than with it. The consequence in many cases has been severe degradation of our natural ecosystems. This, combined with an increased appreciation for the benefits of properly functioning ecosystems, has prompted efforts to restore rivers to a more natural state. However, most restoration projects currently focus on a narrow set of goals, such as endangered species recovery or channel stabilization. In order to shift the restoration community towards more holistic perspectives and approaches, it is necessary to improve understanding of river and floodplain hydrogeomorphic processes and their role in supporting healthy ecosystems. The goal of this research was to investigate the impacts of river engineering and restoration practices on the process of floodwave attenuation. This goal was addressed through numerical investigations that allowed us to: (1) quantify mass and momentum fluxes between river channels and floodplains; (2) investigate the influence of mass and momentum fluxes on floodwave attenuation processes; and (3) evaluate the impacts of river and floodplain restoration on floodwave attenuation. Two-dimensional hydrodynamic models were applied to the Rio Grande, San Joaquin, and Gila rivers in the Southwestern United States using novel modeling approaches to describe dynamic floodplain roughness, fluxes at channel/floodplain interfaces, and attenuation along river corridors. The results provide important insights into the role of floodplain characteristics on floodwave movement and the potential for enhancing floodwave attenuation through river restoration.

Flooding dynamics on the lower Amazon floodplain

NASA Astrophysics Data System (ADS)

Rudorff, C.; Melack, J. M.; Bates, P. D.

2013-05-01

We analyzed flooding dynamics of a large floodplain lake in the lower reach of the Amazon River for the period between 1995 through 2010. Floodplain inundation was simulated using the LISFLOOD-FP model, which combines one-dimensional river routing with two-dimensional overland flow, and a local hydrological model. Accurate representation of floodplain flows and inundation extent depends on the quality of the digital elevation model (DEM). We combined digital topography (derived from the Shuttle Radar Topography Mission) with extensive floodplain echo-sounding data to generate a hydraulically sound DEM. Analysis of daily water balances revealed that the dominant source of inflow alternated seasonally among direct rain and local runoff (October through January), Amazon River (March through August), and seepage (September). As inflows from the Amazon River increase during the rising limb of the hydrograph, regional floodwaters encounter the floodplain partially inundated from local hydrological inputs. At peak flow the floodplain routes, on average, 2.5% of the total discharge for this reach. The falling limb of the hydrograph coincides with the locally dry period, allowing seepage of water stored in sediments to become a dominant source. The average annual inflow from the Amazon River was 58.8 km3 (SD = 33.5), representing more than three thirds (80%) of inputs from all sources, with substantial inter-annual variability. The average annual net export of water from the floodplain to the Amazon River was 7.9 km3 (SD = 2.7).

Advancing towards functional environmental flows for temperate floodplain rivers.

PubMed

Hayes, Daniel S; Brändle, Julia M; Seliger, Carina; Zeiringer, Bernhard; Ferreira, Teresa; Schmutz, Stefan

2018-08-15

Abstraction, diversion, and storage of flow alter rivers worldwide. In this context, minimum flow regulations are applied to mitigate adverse impacts and to protect affected river reaches from environmental deterioration. Mostly, however, only selected instream criteria are considered, neglecting the floodplain as an indispensable part of the fluvial ecosystem. Based on essential functions and processes of unimpaired temperate floodplain rivers, we identify fundamental principles to which we must adhere to determine truly ecologically-relevant environmental flows. Literature reveals that the natural flow regime and its seasonal components are primary drivers for functions and processes of abiotic and biotic elements such as morphology, water quality, floodplain, groundwater, riparian vegetation, fish, macroinvertebrates, and amphibians, thus preserving the integrity of floodplain river ecosystems. Based on the relationship between key flow regime elements and associated environmental components within as well as adjacent to the river, we formulate a process-oriented functional floodplain flow (ff-flow) approach which offers a holistic conceptual framework for environmental flow assessment in temperate floodplain river systems. The ff-flow approach underlines the importance of emulating the natural flow regime with its seasonal variability, flow magnitude, frequency, event duration, and rise and fall of the hydrograph. We conclude that the ecological principles presented in the ff-flow approach ensure the protection of floodplain rivers impacted by flow regulation by establishing ecologically relevant environmental flows and guiding flow restoration measures. Copyright © 2018 The Authors. Published by Elsevier B.V. All rights reserved.

24 CFR 55.11 - Applicability of Subpart C decisionmaking process.

Code of Federal Regulations, 2014 CFR

2014-04-01

... Housing and Urban Development FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS Application of Executive Orders on Floodplain Management and Protection of Wetlands § 55.11 Applicability of Subpart C... amendment) 1 Type of proposed action Floodways Coastal high hazard areas Wetlands or 100-year floodplain...

75 FR 82041 - Notice of Proposed Information Collection: Comment Request; Floodplain Management and Protection...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-12-29

... Information Collection: Comment Request; Floodplain Management and Protection of Wetlands AGENCY: Office of... following information: Title of Proposal: Floodplain Management and Protection of Wetlands. OMB Control... Executive Order 11990, ``Protection of Wetlands.'' Each respondent that proposes to use HUD assistance to...

EXPLOITATION OF FLOODPLAIN RESOURCES BY ADULT LARGESCALE SUCKER OF THE WILLAMETTE RIVER, OREGON

EPA Science Inventory

We tested two predictions of the flood-pulse concept on a large, temperate alluvial river that historically flooded an extensive fringing floodplain. We predicted adult largescale sucker, Catostomus macrocheilus, would: (1) migrate onto the floodplain during high water; and (2) e...

7 CFR 624.10 - Floodplain easements.

Code of Federal Regulations, 2010 CFR

2010-01-01

...) General. NRCS may purchase floodplain easements as an emergency measure. NRCS will only purchase easements... of NRCS, of the floodplain's functions and values; or (iii) The purchase of an easement would not... the right not to purchase an easement if the easement compensation for a particular easement would be...

Sediment accumulation and net storage determined by field observation and numerical modelling for an extensive tropical floodplain: Beni River, Bolivian Llanos

NASA Astrophysics Data System (ADS)

Schwendel, Arved; Aalto, Rolf; Nicholas, Andrew

2014-05-01

Lowland floodplains in subsiding basins form major depocentres responsible for the storage and cycling of large quantities of fine sediment and associated nutrients and contaminants. Obtaining reliable estimates of sediment storage in such environments is problematic due to the high degree of spatial and temporal variability exhibited by overbank sediment accumulation rates, combined with the logistical difficulties inherent in sampling locations far away from the channel. Further complexity is added by the high channel mobility, which recycles sediment and reconfigures the relationships between channel and floodplain morphology, sediment transport and overbank sedimentation. Estimates of floodplain accretion can be derived using a range of numerical sedimentation models of varying complexity. However, data required for model calibration are rarely available for the vast floodplains associated with tropical rivers. We present results from a study of channel-floodplain sediment exchange fluxes on the Rio Beni, a highly dynamic, tropical sand-bed tributary of the Amazon in northern Bolivia. The Beni transports high concentrations of suspended sediment, generated in the river's Andean headwaters, and disperses this material across an extensive floodplain wetland that experiences annual inundation over an area of up to 40000 km2. We utilise estimates of overbank sedimentation rates over the past century derived from 210Pb analysis of floodplain sediment cores collected along a 375 km length of channel, including sampling a range of channel-floodplain configurations within the channel belt and on the distal floodplain (up to 60 km from the channel). These data are used to investigate spatial and temporal variations in rates of floodplain sediment accumulation for a range of grain sizes. Specifically, we examine relationships between sedimentation rate and distance from the channel, and characterise within channel belt variability in sedimentation linked to patterns of channel migration and associated levee reworking. Field data are used to inform a hydrodynamically-driven model of overbank sedimentation and to derive uncertainty-bounded estimates of total floodplain sediment accumulation. Sediment exchange due to planform channel mobility is quantified using a numerical model of meander migration, calibrated using analysis of remote sensing imagery to determine rates and geometry of channel migration. Our combined data and model analysis allows the construction of a mean annual sediment budget for the Beni, which suggests channel-sediment exchange fluxes in the order of 100 Mt a-1, equivalent to 10% of the sediment load of the mainstem Amazon.

76 FR 77162 - Floodplain Management and Protection of Wetlands

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-12

...] RIN 2501-AD51 Floodplain Management and Protection of Wetlands AGENCY: Office of the Secretary, HUD... the protection of wetlands and floodplains. With respect to wetlands, the proposed rule would codify existing procedures for Executive Order 11990 (E.O. 11990), Protection of Wetlands. HUD's current policy is...

76 FR 17427 - Notice of Submission of Proposed Information Collection to OMB; Floodplain Management and...

Federal Register 2010, 2011, 2012, 2013, 2014

2011-03-29

... Proposed Information Collection to OMB; Floodplain Management and Protection of Wetlands AGENCY: Office of... proposal. HUD grant recipients proposing to use HUD funds for projects within floodplains or wetlands... Building, Washington, DC 20503; e-mail [email protected] , fax: 202-395- 5806. FOR FURTHER...

44 CFR 9.9 - Analysis and reevaluation of practicable alternatives.

Code of Federal Regulations, 2014 CFR

2014-10-01

... AGENCY, DEPARTMENT OF HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.9... alternative, or the floodplain or wetland is itself not a practicable location, FEMA shall then act on that...' key requirements to avoid floodplains and wetlands unless there is no practicable alternative. (2...

44 CFR 9.6 - Decision-making process.

Code of Federal Regulations, 2012 CFR

2012-10-01

... HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.6 Decision-making process. (a) Purpose. The purpose of this section is to set out the floodplain management and wetlands... light of the information gained in Steps 4 and 5. FEMA shall not act in a floodplain or wetland unless...

44 CFR 9.6 - Decision-making process.

Code of Federal Regulations, 2011 CFR

2011-10-01

... HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.6 Decision-making process. (a) Purpose. The purpose of this section is to set out the floodplain management and wetlands... light of the information gained in Steps 4 and 5. FEMA shall not act in a floodplain or wetland unless...

44 CFR 9.9 - Analysis and reevaluation of practicable alternatives.

Code of Federal Regulations, 2012 CFR

2012-10-01

... AGENCY, DEPARTMENT OF HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.9... alternative, or the floodplain or wetland is itself not a practicable location, FEMA shall then act on that...' key requirements to avoid floodplains and wetlands unless there is no practicable alternative. (2...

44 CFR 9.6 - Decision-making process.

Code of Federal Regulations, 2013 CFR

2013-10-01

... HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.6 Decision-making process. (a) Purpose. The purpose of this section is to set out the floodplain management and wetlands... light of the information gained in Steps 4 and 5. FEMA shall not act in a floodplain or wetland unless...

44 CFR 9.6 - Decision-making process.

Code of Federal Regulations, 2014 CFR

2014-10-01

... HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.6 Decision-making process. (a) Purpose. The purpose of this section is to set out the floodplain management and wetlands... light of the information gained in Steps 4 and 5. FEMA shall not act in a floodplain or wetland unless...

44 CFR 9.9 - Analysis and reevaluation of practicable alternatives.

Code of Federal Regulations, 2013 CFR

2013-10-01

... AGENCY, DEPARTMENT OF HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.9... alternative, or the floodplain or wetland is itself not a practicable location, FEMA shall then act on that...' key requirements to avoid floodplains and wetlands unless there is no practicable alternative. (2...

10 CFR 1022.14 - Findings.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 4 2010-01-01 2010-01-01 false Findings. 1022.14 Section 1022.14 Energy DEPARTMENT OF... Procedures for Floodplain and Wetland Reviews § 1022.14 Findings. (a) If DOE finds that no practicable... that will be located in a floodplain, DOE shall issue a floodplain statement of findings, normally not...

78 FR 74009 - Floodplain Management and Protection of Wetlands; Correction

Federal Register 2010, 2011, 2012, 2013, 2014

2013-12-10

...] RIN 2501-AD51 Floodplain Management and Protection of Wetlands; Correction AGENCY: Office of the... governing the protection of wetlands and floodplains. Upon publication, HUD discovered that it inadvertently... by calling the Federal Relay Service at 800-877-8339 (this is a toll-free number). SUPPLEMENTARY...

A geologic approach to field methods in fluvial geomorphology

USGS Publications Warehouse

Fitzpatrick, Faith A.; Thornbush, Mary J; Allen, Casey D; Fitzpatrick, Faith A.

2014-01-01

A geologic approach to field methods in fluvial geomorphology is useful for understanding causes and consequences of past, present, and possible future perturbations in river behavior and floodplain dynamics. Field methods include characterizing river planform and morphology changes and floodplain sedimentary sequences over long periods of time along a longitudinal river continuum. Techniques include topographic and bathymetric surveying of fluvial landforms in valley bottoms and describing floodplain sedimentary sequences through coring, trenching, and examining pits and exposures. Historical sediment budgets that include floodplain sedimentary records can characterize past and present sources and sinks of sediment along a longitudinal river continuum. Describing paleochannels and floodplain vertical accretion deposits, estimating long-term sedimentation rates, and constructing historical sediment budgets can assist in management of aquatic resources, habitat, sedimentation, and flooding issues.

Ecology of bottomland hardwood swamps of the southeast: a community profile

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

Wharton, C.H.; Kitchens, W.M.; Pendleton, E.C.

1982-03-01

This report synthesizes extant literature detailing the ecology of bottomland hardwood swamps in the Southeast. The geographic scope focuses the report to the hardwoods occupying the floodplains of the rivers whose drainages originate in the Appalachian Mountains/Piedmont and Coastal Plain (NC, SC, GA, and FL). The origin and dynamics of the floodplains are described and related to hydrology and physiographic provinces. Further, the biogeochemistry and interactions between the riverine and floodplain environments are discussed in conjunction with floodplain biology. Plant and animal community structure and ecological processes (productivity) are detailed and organized by ecological zones. The final chapter discusses themore » ecological value of the floodplain ecosystems and the nature of their relationships to adjacent uplands, downstream coastal estuaries and the atmosphere.« less

Linking Domain-Specific Models to Describe the Complex Dynamics and Management Options of a Saline Floodplain

NASA Astrophysics Data System (ADS)

Woods, J.; Laattoe, T.

2016-12-01

Complex hydrological environments present management challenges where surface water-groundwater interactions involve interlinked processes at multiple scales. One example is Australia's River Murray, which flows through a semi-arid landscape with highly saline groundwater. In this region, the floodplain ecology depends on freshwater provided from the main river channel, anabranches, and floodwaters. However, in the past century access to freshwater has been further limited due to river regulation, land clearance, and irrigation. A programme to improve ecosystem health at Pike Floodplain, South Australia, is evaluating management options such as environmental watering and groundwater pumping. Due to the complicated interdependencies between processes moving water and salt within the floodplain, a series of inter-linked models were developed to assist with management decisions. The models differ by hydrological domain, scale, and dimensionality. Together they simulate surface water, the unsaturated zone, and groundwater on regional, floodplain, and local scales. Outputs from regional models provide boundary conditions for floodplain models, which in turn provide inputs for the local scale models. The results are interpreted based on (i) ecohydrological requirements for key species of tree and fish, and (ii) impacts on river salinity for downstream users. When combined, the models provide an integrated and interdiscplinary understanding of the hydrology and management of saline floodplains.

Hydrodynamic controls on the long-term construction of large river floodplains and alluvial ridges

NASA Astrophysics Data System (ADS)

Nicholas, Andrew; Aalto, Rolf; Sambrook Smith, Gregory; Schwendel, Arved

2017-04-01

Floodplain construction involves the interplay between channel belt sedimentation and avulsion, overbank deposition of fines, and sediment reworking by channel migration. Each of these processes is controlled, in part, by within-channel and/or overbank hydraulics. However, while spatially-distributed hydrodynamic models are used routinely to simulate floodplain inundation and overbank sedimentation during individual floods, most existing models of long-term floodplain construction and alluvial architecture do not account for flood hydraulics explicitly. Instead, floodplain sedimentation is typically modelled as an exponential function of distance from the river, and avulsion thresholds are defined using topographic indices that quantify alluvial ridge morphology (e.g., lateral:downstream slope ratios or metrics of channel belt super-elevation). Herein, we apply a hydraulically driven model of floodplain evolution, in order to quantify the controls on alluvial ridge construction and avulsion likelihood in large lowland rivers. We combine a simple model of meander migration and cutoff with a 2D grid-based model of flood hydrodynamics and overbank sedimentation. The latter involves a finite volume solution of the shallow water equations and an advection-diffusion model for suspended sediment transport. The model is used to carry out a series of numerical experiments to investigate floodplain construction for a range of flood regimes and sediment supply scenarios, and results are compared to field data from the Rio Beni system, northern Bolivia. Model results, supported by field data, illustrate that floodplain sedimentation is characterised by a high degree of intermittency that is driven by autogenic mechanisms (i.e. even in the absence of temporal variations in flood magnitude and sediment supply). Intermittency in overbank deposits occurs over a range of temporal and spatial scales, and is associated with the interaction between channel migration dynamics and crevasse splay formation. Moreover, alluvial ridge construction, by splay deposition, is controlled by the balance between in-channel and overbank sedimentation rates, and by ridge reworking linked to channel migration. The resulting relationship between sedimentation rates, ridge morphology and avulsion likelihood is more complex than that which is incorporated with existing models of long-term floodplain construction that neglect flood hydraulics. These results have implications for the interpretation of floodplain deposits as records of past flood regimes, and for the controls on the alluvial architecture of large river floodplains.

Anatomy and dynamics of a floodplain, Powder River, Montana, U.S.A.

USGS Publications Warehouse

Pizzuto, J.E.; Moody, J.A.; Meade, R.H.

2008-01-01

Centimeter-scale measurements on several Powder River floodplains provide insights into the nature of overbank depositional processes that created the floodplains; during a 20-year period after a major flood in 1978. Rising stages initially entered across a sill at the downriver end of the floodplains. Later, as stages continued to rise, water entered the floodplains through distinct low saddles along natural levees. The annual maximum depth of water over the levee crest averaged 0.19 in from 1983 through 1996, and the estimated flow velocities were approximately 0.15 m s-1. Water ponded in the floodplain trough, a topographic low between the natural levee and the pre-flood riverbank, and mud settled as thin layers of nearly constant thickness. Mud layers alternated with sand layers, which were relatively thick near the channel. Together, these beds created a distinctive natural levee. In some locations, individual flood deposits began as a thin mud layer that gradually coarsened upwards to medium-grained sand. Coarsening-upwards sequences form initially as mud because only the uppermost layers of water in the channel supply the first overbank flows, which are rich in mud but starved of sand. At successively higher stages, fine sands and then medium sands increase in concentration in the floodwater and are deposited as fine- and medium-sand layers overlying the initial mud layer. Theoretical predictions from mathematical models of sediment transport by advection and diffusion indicate that these processes acting alone are unlikely to create the observed sand layers of nearly uniform thickness that extend across much of the floodplain. We infer that other transport processes, notably bedload transport, must be important along Powder River. Even with the centimeter-scale measurements of floodplain deposits, daily hydraulic data, and precise annual surface topographic surveys, we were unable to determine any clear correspondence between the gauged flow record of overbank floods and the depositional layers mapped in the floodplain. These results provide a detailed example of floodplain deposits and depositional processes that should prove useful for interpreting natural levee deposits in a variety of geologic settings. Copyright ?? 2008, SEPM (Society for Sedimentary Geology).

Sediment size of surface floodplain sediments along a large lowland river

NASA Astrophysics Data System (ADS)

Swanson, K. M.; Day, G.; Dietrich, W. E.

2007-12-01

Data on size distribution of surface sediment across a floodplain should place important constraints of modeling of floodplain deposition. Diffusive or advective models would predict that, generally, grain size should decrease away from channel banks. Variations in grain size downstream along floodplains may depend on downstream fining of river bed material, exchange rate with river banks and net deposition onto the floodplain. Here we report detailed grain size analyses taken from 17 floodplain transects along 450 km (along channel distance) reach of the middle Fly River, Papua New Guinea. Field studies have documented a systematic change in floodplain characteristics downstream from forested, more topographically elevated and topography bounded by an actively shifting mainstem channel to a downstream swamp grass, low elevation topography along which the river meanders are currently stagnant. Frequency and duration of flooding increase downstream. Flooding occurs both by overbank flows and by injections of floodwaters up tributary and tie channels connected to the mainstem. Previous studies show that about 40% of the total discharge of water passes across the floodplain, and, correspondingly, about 40% of the total load is deposited on the plain - decreasing exponentially from channel bank. We find that floodplain sediment is most sandy at the channel bank. Grain size rapidly declines away from the bank, but surprisingly two trends were also observed. A relatively short distance from the bank the surface material is finest, but with further distance from the bank (out to greater than 1 km from the 250 m wide channel) clay content decreases and silt content increases. The changes are small but repeated at most of the transects. The second trend is that bank material fines downstream, corresponding to a downstream finding bed material, but once away from the bank, there is a weak tendency for a given distance away from the bank the floodplain surface deposits to slightly coarsen downstream. We also find that sand is present (about 4%) in these surface sediments out to 1 km from the channel bank. These trends are not consistent with simple lateral transport models, and other factors, including effects of flocculation, local flow patterns, and possibly dry season wind effects may matter.

The application of Caesium-137 and Plutonium-239+240 measurements to investigate floodplain deposition in a semi-arid, low-fallout environment

NASA Astrophysics Data System (ADS)

Amos, K. J.; Croke, J. C.; Timmers, H.; Owens, P. N.

2009-04-01

Floodplains comprise geomorphologically important sources and sinks for sediments and associated pollutants, yet the sedimentology of large dryland floodplains is not well understood. Processes occurring on such floodplains are often difficult to observe, and techniques used to investigate smaller perennial floodplains are often not practical in these environments. This study assesses the utility of Cs-137 inventory and depth-profile techniques for determining relative amounts of floodplain sedimentation in the Fitzroy River, north-eastern Australia; a 143 000 km2 semi-arid river system. Caesium-137 inventories were calculated for floodplain and reference location bulk soil cores collected from four sites. Depth profiles of Cs-137 concentration from each floodplain site and a reference location were recorded. The areal density of Cs-137 at reference locations ranged from 13-978 Bq m-2 (0-1367 Bq m-2 at the 95% confidence interval), and the mean value ± 2(standard error of the mean) was 436±264 Bq m-2, similar to published data from other southern hemisphere locations. Floodplain inventories ranged from 68-1142 Bq m-2 (0-1692 Bq m-2 at the 95% confidence interval), essentially falling within the range of reference inventory values, thus preventing calculation of erosion or deposition. Depth-profiles of Cs-137 concentration indicate erosion at one site and over 66 cm of deposition at another since 1954. Analysis of 239+240Pu concentrations in a depositional core substantiated the interpretation made from Cs-137 data, and depict a more tightly constrained peak in concentration. Average annual deposition rates range from 0-15 mm. The similarity between floodplain and reference bulk inventories does not necessarily indicate a lack of erosion or deposition, due to low Cs-137 fallout in the region and associated high measurement uncertainties, and a likely influence of gully and bank eroded sediments with no or limited adsorbed Cs-137. In this low-fallout environment, detailed depth-profile data are necessary for investigating sedimentation using Cs-137.

Hydrologic variability, water chemistry, and phytoplankton biomass in a large flood plain of the Sacramento River, CA, U.S.A.

USGS Publications Warehouse

Schemel, L.E.; Sommer, T.R.; Muller-Solger, A. B.; Harrell, W.C.

2004-01-01

The Yolo Bypass, a large, managed floodplain that discharges to the headwaters of the San Francisco Estuary, was studied before, during, and after a single, month-long inundation by the Sacramento River in winter and spring 2000. The primary objective was to identify hydrologic conditions and other factors that enhance production of phytoplankton biomass in the floodplain waters. Recent reductions in phytoplankton have limited secondary production in the river and estuary, and increased phytoplankton biomass is a restoration objective for this system. Chlorophyll a was used as a measure of phytoplankton biomass in this study. Chlorophyll a concentrations were low (<4 ??g l -1) during inundation by the river when flow through the floodplain was high, but concentrations rapidly increased as river inflow decreased and the floodplain drained. Therefore, hydrologic conditions in the weeks following inundation by river inflow appeared most important for producing phytoplankton biomass in the floodplain. Discharges from local streams were important sources of water to the floodplain before and after inundation by the river, and they supplied dissolved inorganic nutrients while chlorophyll a was increasing. Discharge from the floodplain was enriched in chlorophyll a relative to downstream locations in the river and estuary during the initial draining and later when local stream inflows produced brief discharge pulses. Based on the observation that phytoplankton biomass peaks during drainage events, we suggest that phytoplankton production in the floodplain and biomass transport to downstream locations would be higher in years with multiple inundation and draining sequences.

Algal extracellular release in river-floodplain dissolved organic matter: response of extracellular enzymatic activity during a post-flood period

PubMed Central

Sieczko, Anna; Maschek, Maria; Peduzzi, Peter

2015-01-01

River-floodplain systems are susceptible to rapid hydrological events. Changing hydrological connectivity of the floodplain generates a broad range of conditions, from lentic to lotic. This creates a mixture of allochthonously and autochthonously derived dissolved organic matter (DOM). Autochthonous DOM, including photosynthetic extracellular release (PER), is an important source supporting bacterial secondary production (BSP). Nonetheless, no details are available regarding microbial extracellular enzymatic activity (EEA) as a response to PER under variable hydrological settings in river-floodplain systems. To investigate the relationship between bacterial and phytoplankton components, we therefore used EEA as a tool to track the microbial response to non-chromophoric, but reactive and ecologically important DOM. The study was conducted in three floodplain subsystems with distinct hydrological regimes (Danube Floodplain National Park, Austria). The focus was on the post-flood period. Enhanced %PER (up to 48% of primary production) in a hydrologically isolated subsystem was strongly correlated with β-glucosidase, which was related to BSP. This shows that—in disconnected floodplain backwaters with high terrestrial input—BSP can also be driven by autochthonous carbon sources (PER). In a semi-isolated section, in the presence of fresh labile material from primary producers, enhanced activity of phenol oxidase was observed. In frequently flooded river-floodplain systems, BSP was mainly driven by enzymatic degradation of particulate primary production. Our research demonstrates that EEA measurements are an excellent tool to describe the coupling between bacteria and phytoplankton, which cannot be deciphered when focusing solely on chromophoric DOM. PMID:25741326

Geomorphic Controls on Floodplain Soil Organic Carbon in the Yukon Flats, Interior Alaska, From Reach to River Basin Scales

NASA Astrophysics Data System (ADS)

Lininger, K. B.; Wohl, E.; Rose, J. R.

2018-03-01

Floodplains accumulate and store organic carbon (OC) and release OC to rivers, but studies of floodplain soil OC come from small rivers or small spatial extents on larger rivers in temperate latitudes. Warming climate is causing substantial change in geomorphic process and OC fluxes in high latitude rivers. We investigate geomorphic controls on floodplain soil OC concentrations in active-layer mineral sediment in the Yukon Flats, interior Alaska. We characterize OC along the Yukon River and four tributaries in relation to geomorphic controls at the river basin, segment, and reach scales. Average OC concentration within floodplain soil is 2.8% (median = 2.2%). Statistical analyses indicate that OC varies among river basins, among planform types along a river depending on the geomorphic unit, and among geomorphic units. OC decreases with sample depth, suggesting that most OC accumulates via autochthonous inputs from floodplain vegetation. Floodplain and river characteristics, such as grain size, soil moisture, planform, migration rate, and riverine DOC concentrations, likely influence differences among rivers. Grain size, soil moisture, and age of surface likely influence differences among geomorphic units. Mean OC concentrations vary more among geomorphic units (wetlands = 5.1% versus bars = 2.0%) than among study rivers (Dall River = 3.8% versus Teedrinjik River = 2.3%), suggesting that reach-scale geomorphic processes more strongly control the spatial distribution of OC than basin-scale processes. Investigating differences at the basin and reach scale is necessary to accurately assess the amount and distribution of floodplain soil OC, as well as the geomorphic controls on OC.

Flood effects on an Alaskan stream restoration project: the value of long-term monitoring

USGS Publications Warehouse

Densmore, Roseann V.; Karle, Kenneth F.

2009-01-01

On a nationwide basis, few stream restoration projects have long-term programs in place to monitor the effects of floods on channel and floodplain configuration and floodplain vegetation, but long-term and event-based monitoring is required to measure the effects of these stochastic events and to use the knowledge for adaptive management and the design of future projects. This paper describes a long-term monitoring effort (15 years) on a stream restoration project in Glen Creek in Denali National Park and Preserve in Alaska. The stream channel and floodplain of Glen Creek had been severely degraded over a period of 80 years by placer mining for gold, which left many reaches with unstable and incised streambeds without functioning vegetated floodplains. The objectives of the original project, initiated in 1991, were to develop and test methods for the hydraulic design of channel and floodplain morphology and for floodplain stabilization and riparian habitat recovery, and to conduct research and monitoring to provide information for future projects in similar degraded watersheds. Monitoring methods included surveyed stream cross-sections, vegetation plots, and aerial, ground, and satellite photos. In this paper we address the immediate and outlying effects of a 25-year flood on the stream and floodplain geometry and riparian vegetation. The long-term monitoring revealed that significant channel widening occurred following the flood, likely caused by excessive upstream sediment loading and the fairly slow development of floodplain vegetation in this climate. Our results illustrated design flaws, particularly in regard to identification and analysis of sediment sources and the dominant processes of channel adjustment.

76 FR 79145 - Floodplain Management and Protection of Wetlands

Federal Register 2010, 2011, 2012, 2013, 2014

2011-12-21

...] RIN 2501-AD51 Floodplain Management and Protection of Wetlands Correction In proposed rule document... action or an year floodplain outside of the amendment) \\1\\ Floodways Coastal high hazard outside coastal... existing structure; (2) is designed for a Coastal High Hazard Area under Sec. 55.1(c)(3); and (3) is...

Survival results of a biomass planting in the Missouri River floodplain

Treesearch

W. D. ' Dusty' Walter; John P. Dwyer

2003-01-01

A factor essential to successful tree planting in unprotected floodplain environments is survival. Two-year survival results from tree planting in an unprotected floodplain adjacent to the Missouri River are presented. Species planted included silver maple, locally collected cottonwood, and a superior cottonwood selection from Westvaco Corporation. Two spacings, 4 x 4...

44 CFR 9.14 - Disposal of Agency property.

Code of Federal Regulations, 2010 CFR

2010-10-01

..., DEPARTMENT OF HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.14 Disposal of... provisions of § 9.7 to determine if it affects or is affected by a floodplain or wetland; (2) The public... alternative use that is more consistent with the floodplain management and wetland protection policies set out...

Monitoring height and greenness of non-woody floodplain vegetation with UAV time series

NASA Astrophysics Data System (ADS)

van Iersel, Wimala; Straatsma, Menno; Addink, Elisabeth; Middelkoop, Hans

2018-07-01

Vegetation in river floodplains has important functions for biodiversity, but can also have a negative influence on flood safety. Floodplain vegetation is becoming increasingly heterogeneous in space and time as a result of river restoration projects. To document the spatio-temporal patterns of the floodplain vegetation, the need arises for efficient monitoring techniques. Monitoring is commonly performed by mapping floodplains based on single-epoch remote sensing data, thereby not considering seasonal dynamics of vegetation. The rising availability of unmanned airborne vehicles (UAV) increases monitoring frequency potential. Therefore, we aimed to evaluate the performance of multi-temporal high-spatial-resolution imagery, collected with a UAV, to record the dynamics in floodplain vegetation height and greenness over a growing season. Since the classification accuracy of current airborne surveys remains insufficient for low vegetation types, we focussed on seasonal variation of herbaceous and grassy vegetation with a height up to 3 m. Field reference data on vegetation height were collected six times during one year in 28 field plots within a single floodplain along the Waal River, the main distributary of the Rhine River in the Netherlands. Simultaneously with each field survey, we recorded UAV true-colour and false-colour imagery from which normalized digital surface models (nDSMs) and a consumer-grade camera vegetation index (CGCVI) were calculated. We observed that: (1) the accuracy of a UAV-derived digital terrain model (DTM) varies over the growing season and is most accurate during winter when the vegetation is dormant, (2) vegetation height can be determined from the nDSMs in leaf-on conditions via linear regression (RSME = 0.17-0.33 m), (3) the multitemporal nDSMs yielded meaningful temporal profiles of greenness and vegetation height and (4) herbaceous vegetation shows hysteresis for greenness and vegetation height, but no clear hysteresis was observed for grassland vegetation. These results show the high potential of using UAV-borne sensors for increasing the classification accuracy of low floodplain vegetation within the framework of floodplain monitoring.

Contribution of geophysical methods in the study of the floodplain structure (the Litavka River, the Czech Republic)

NASA Astrophysics Data System (ADS)

Kotková, Kristýna; Matys Grygar, Tomáš; Tůmová, Štěpánka; Elznicová, Jitka

2017-04-01

Mining and processing of polymetallic ores near the city of Příbram (the Czech Republic) have strongly impacted the fluvial system of the Litavka River. Beside of polymetallic mining during several hundred years with a peak between 1850 and 1950, the Litavka River was also influenced by uranium ore mining between 1948 and 1989. Severe contamination of the Litavka River system is known, but the alluvial architecture and specific distribution of contamination has not yet been satisfactorily described. However, such pieces of information are necessary for the predictions of the future behaviour of contaminants in the river system. We used geophysical methods for visualisation of subsurface layers of sediments and we have proved them very useful for the survey of the floodplain structure. It is especially advantageous when the surface topography of the floodplain does not reveal its internal structure, e.g. due to floodplain levelling by aggradation. Specifically, dipole electromagnetic profiling, also denoted electromagnetic induction sensing (DEMP) was used for quick detection of major heterogeneities in the floodplain structure. In addition, electrical resistivity tomography (ERT) was used for the exploration of lines across the heterogeneities shown by DEMP. This approach allows to choose the appropriate plan for the subsequent sampling in the floodplain to include all its structural (lithogenetic) units. Such rational strategy allows for reducing total amount of sampled sites without the risk of losing important information and production of false images. Both used geophysical tools and manual drill coring and the elemental analysis by handheld X-ray fluorescence spectrometry produced clear images of floodplain architecture and pollutant distribution. The internal structure of the Litavka River floodplain shows that lateral deposition and reworking of sediments played the main roles in the floodplain building. In the next centuries the lateral channel movement will rework contamination which is maximal in the current channel belt.

Predominant floodplain over mountain weathering of Himalayan sediments (Ganga basin)

NASA Astrophysics Data System (ADS)

Lupker, Maarten; France-Lanord, Christian; Galy, Valier; Lavé, Jérôme; Gaillardet, Jérôme; Gajurel, Ananta Prasad; Guilmette, Caroline; Rahman, Mustafizur; Singh, Sunil Kumar; Sinha, Rajiv

2012-05-01

We present an extensive river sediment dataset covering the Ganga basin from the Himalayan front downstream to the Ganga mainstream in Bangladesh. These sediments were mainly collected over several monsoon seasons and include depth profiles of suspended particles in the river water column. Mineral sorting is the first order control on the chemical composition of river sediments. Taking into account this variability we show that sediments become significantly depleted in mobile elements during their transit through the floodplain. By comparing sediments sampled at the Himalayan front with sediments from the Ganga mainstream in Bangladesh it is possible to budget weathering in the floodplain. Assuming a steady state weathering regime in the floodplain, the weathering of Himalayan sediments in the Gangetic floodplain releases ca. (189 ± 92) × 109 and (69 ± 22) × 109 mol/yr of carbonate bound Ca and Mg to the dissolved load, respectively. Silicate weathering releases (53 ± 18) × 109 and (42 ± 13) × 109 mol/yr of Na and K while the release of silicate Mg and Ca is substantially lower, between ca. 0 and 20 × 109 mol/yr. Additionally, we show that sediment hydration, [H2O+], is a sensitive tracer of silicate weathering that can be used in continental detrital environments, such as the Ganga basin. Both [H2O+] content and the D/H isotopic composition of sediments increases during floodplain transfer in response to mineral hydrolysis and neoformations associated to weathering reactions. By comparing the chemical composition of river sediments across the floodplain with the composition of the eroded Himalayan source rocks, we suggest that the floodplain is the dominant location of silicate weathering for Na, K and [H2O+]. Overall this work emphasizes the role of the Gangetic floodplain in weathering Himalayan sediments. It also demonstrates how detrital sediments can be used as weathering tracers if mineralogical and chemical sorting effects are properly taken into account.

Evaluating the role of river-floodplain connectivity in providing beneficial hydrologic services in mountain landscapes

NASA Astrophysics Data System (ADS)

Covino, T. P.; Wegener, P.; Weiss, T.; Wohl, E.; Rhoades, C.

2017-12-01

River networks of mountain landscapes tend to be dominated by steep, valley-confined channels that have limited floodplain area and low hydrologic buffering capacity. Interspersed between the narrow segments are wide, low-gradient segments where extensive floodplains, wetlands, and riparian areas can develop. Although they tend to be limited in their frequency relative to the narrow valley segments, the low-gradient, wide portions of mountain channel networks can be particularly important to hydrologic buffering and can be sites of high nutrient retention and ecosystem productivity. Hydrologic buffering along the wide valley segments is dependent on lateral hydrologic connectivity between the river and floodplain, however these connections have been increasingly severed as a result of various land and water management practices. We evaluated the role of river-floodplain connectivity in influencing water, dissolved organic carbon (DOC), and nutrient flux in river networks of the Colorado Rockies. We found that disconnected segments with limited floodplain/riparian area had limited buffering capacity, while connected segments exhibited variable source-sink dynamics as a function of flow. Specifically, connected segments were typically a sink for water, DOC, and nutrients during high flows, and subsequently became a source as flows decreased. Shifts in river-floodplain hydrologic connectivity across flows related to higher and more variable aquatic ecosystem metabolism rates along connected relative to disconnected segments. Our data suggest that lateral hydrologic connectivity in wide valleys can enhance hydrologic and biogeochemical buffering, and promote high rates of aquatic ecosystem metabolism. While hydrologic disconnection in one river-floodplain system is unlikely to influence water resources at larger scales, the cumulative effects of widespread disconnection may be substantial. Because intact river-floodplain (i.e., connected) systems provide numerous hydrologic and ecologic benefits, understanding the dynamics and cumulative effects of disconnection is an important step toward improved water resource and ecosystem management.

Soil greenhouse gas emissions and carbon budgeting in a short-hydroperiod floodplain wetland

USGS Publications Warehouse

Batson, Jackie; Noe, Gregory B.; Hupp, Cliff R.; Krauss, Ken W.; Rybicki, Nancy B.; Schenk, Edward R.

2015-01-01

Understanding the controls on floodplain carbon (C) cycling is important for assessing greenhouse gas emissions and the potential for C sequestration in river-floodplain ecosystems. We hypothesized that greater hydrologic connectivity would increase C inputs to floodplains that would not only stimulate soil C gas emissions but also sequester more C in soils. In an urban Piedmont river (151 km2 watershed) with a floodplain that is dry most of the year, we quantified soil CO2, CH4, and N2O net emissions along gradients of floodplain hydrologic connectivity, identified controls on soil aerobic and anaerobic respiration, and developed a floodplain soil C budget. Sites were chosen along a longitudinal river gradient and across lateral floodplain geomorphic units (levee, backswamp, and toe slope). CO2 emissions decreased downstream in backswamps and toe slopes and were high on the levees. CH4 and N2O fluxes were near zero; however, CH4emissions were highest in the backswamp. Annual CO2 emissions correlated negatively with soil water-filled pore space and positively with variables related to drier, coarser soil. Conversely, annual CH4 emissions had the opposite pattern of CO2. Spatial variation in aerobic and anaerobic respiration was thus controlled by oxygen availability but was not related to C inputs from sedimentation or vegetation. The annual mean soil CO2 emission rate was 1091 g C m−2 yr−1, the net sedimentation rate was 111 g C m−2 yr−1, and the vegetation production rate was 240 g C m−2 yr−1, with a soil C balance (loss) of −338 g C m−2 yr−1. This floodplain is losing C likely due to long-term drying from watershed urbanization.

On river-floodplain interaction and hydrograph skewness

NASA Astrophysics Data System (ADS)

Fleischmann, Ayan S.; Paiva, Rodrigo C. D.; Collischonn, Walter; Sorribas, Mino V.; Pontes, Paulo R. M.

2016-10-01

Understanding hydrological processes occurring within a basin by looking at its outlet hydrograph can improve and foster comprehension of ungauged regions. In this context, we present an extensive examination of the roles that floodplains play on driving hydrograph shapes. Observations of many river hydrographs with large floodplain influence are carried out and indicate that a negative skewness of the hydrographs is present among many of them. Through a series of numerical experiments and analytical reasoning, we show how the relationship between flood wave celerity and discharge in such systems is responsible for determining the hydrograph shapes. The more water inundates the floodplains upstream of the observed point, the more negatively skewed is the observed hydrograph. A case study is performed in the Amazon River Basin, where major rivers with large floodplain attenuation (e.g., Purus, Madeira, and Juruá) are identified with higher negative skewness in the respective hydrographs. Finally, different wetland types could be distinguished by using this feature, e.g., wetlands maintained by endogenous processes, from wetlands governed by overbank flow (along river floodplains). A metric of hydrograph skewness was developed to quantify this effect, based on the time derivative of discharge. Together with the skewness concept, it may be used in other studies concerning the relevance of floodplain attenuation in large, ungauged rivers, where remote sensing data (e.g., satellite altimetry) can be very useful.

Influence of dams on river-floodplain dynamics in the Elwha River, Washington

USGS Publications Warehouse

Kloehn, K.K.; Beechie, T.J.; Morley, S.A.; Coe, H.J.; Duda, J.J.

2008-01-01

The Elwha dam removal project presents an ideal opportunity to study how historic reduction and subsequent restoration of sediment supply alter river-floodplain dynamics in a large, forested river floodplain. We used remote sensing and onsite data collection to establish a historical record of floodplain dynamics and a baseline of current conditions. Analysis was based on four river reaches, three from the Elwha River and the fourth from the East Fork of the Quinault River. We found that the percentage of floodplain surfaces between 25 and 75 years old decreased and the percentage of surfaces >75 years increased in reaches below the Elwha dams. We also found that particle size decreased as downstream distance from dams increased. This trend was evident in both mainstem and side channels. Previous studies have found that removal of the two Elwha dams will initially release fine sediment stored in the reservoirs, then in subsequent decades gravel bed load supply will increase and gradually return to natural levels, aggrading river beds up to 1 m in some areas. We predict the release of fine sediments will initially create bi-modal grain size distributions in reaches downstream of the dams, and eventual recovery of natural sediment supply will significantly increase lateral channel migration and erosion of floodplain surfaces, gradually shifting floodplain age distributions towards younger age classes.

Complexity of Bacterial Communities in a River-Floodplain System (Danube, Austria)

PubMed Central

Besemer, Katharina; Moeseneder, Markus M.; Arrieta, Jesus M.; Herndl, Gerhard J.; Peduzzi, Peter

2005-01-01

Natural floodplains play an essential role in the processing and decomposition of organic matter and in the self-purification ability of rivers, largely due to the activity of bacteria. Knowledge about the composition of bacterial communities and its impact on organic-matter cycling is crucial for the understanding of ecological processes in river-floodplain systems. Particle-associated and free-living bacterial assemblages from the Danube River and various floodplain pools with different hydrological characteristics were investigated using terminal restriction fragment length polymorphism analysis. The particle-associated bacterial community exhibited a higher number of operational taxonomic units (OTUs) and was more heterogeneous in time and space than the free-living community. The temporal dynamics of the community structure were generally higher in isolated floodplain pools. The community structures of the river and the various floodplain pools, as well as those of the particle-associated and free-living bacteria, differed significantly. The compositional dynamics of the planktonic bacterial communities were related to changes in the algal biomass, temperature, and concentrations of organic and inorganic nutrients. The OTU richness of the free-living community was correlated with the concentration and origin of organic matter and the concentration of inorganic nutrients, while no correlation with the OTU richness of the particle-associated assemblage was found. Our results demonstrate the importance of the river-floodplain interactions and the influence of damming and regulation on the bacterial-community composition. PMID:15691909

Floodplain Mapping for the Continental United States Using Machine Learning Techniques and Watershed Characteristics

NASA Astrophysics Data System (ADS)

Jafarzadegan, K.; Merwade, V.; Saksena, S.

2017-12-01

Using conventional hydrodynamic methods for floodplain mapping in large-scale and data-scarce regions is problematic due to the high cost of these methods, lack of reliable data and uncertainty propagation. In this study a new framework is proposed to generate 100-year floodplains for any gauged or ungauged watershed across the United States (U.S.). This framework uses Flood Insurance Rate Maps (FIRMs), topographic, climatic and land use data which are freely available for entire U.S. for floodplain mapping. The framework consists of three components, including a Random Forest classifier for watershed classification, a Probabilistic Threshold Binary Classifier (PTBC) for generating the floodplains, and a lookup table for linking the Random Forest classifier to the PTBC. The effectiveness and reliability of the proposed framework is tested on 145 watersheds from various geographical locations in the U.S. The validation results show that around 80 percent of total watersheds are predicted well, 14 percent have acceptable fit and less than five percent are predicted poorly compared to FIRMs. Another advantage of this framework is its ability in generating floodplains for all small rivers and tributaries. Due to the high accuracy and efficiency of this framework, it can be used as a preliminary decision making tool to generate 100-year floodplain maps for data-scarce regions and all tributaries where hydrodynamic methods are difficult to use.

Floodplain inundation response to climate, valley form, and flow regulation on a gravel-bed river in a Mediterranean-climate region

NASA Astrophysics Data System (ADS)

Cienciala, P.; Pasternack, G. B.

2017-04-01

Floodplain inundation regime defines hydrological connectivity between river channel and floodplain and thus strongly controls structure and function of these highly diverse and productive ecosystems. We combined an extensive LiDAR data set on topography and vegetation, long-term hydrological records, as well as the outputs of hydrological and two-dimensional hydraulic models to examine how floodplain inundation regimes in a dynamic, regulated, gravel-cobble river in a Mediterranean-climate region are controlled by reach-scale valley morphology, hydroclimatic conditions, and flow regulation. Estimated relative differences in the extent, duration, and cumulative duration of inundation events were often as large as an order of magnitude and generally greatest for large and long duration events. The relative impact of flow regulation was greatest under dry hydroclimatic conditions. Although the effects of hydroclimate and flow impairment are larger than that of valley floor topography, the latter controls sensitivity of floodplain hydroperiod to flow regime changes and should not be ignored. These quantitative estimates of the relative importance of factors that control floodplain processes in Mediterranean, semiarid rivers contributes to better understanding of hydrology and geomorphology of this important class of channels. We also discuss implications of our findings for processes that shape floodplain habitat for riparian vegetation and salmonid fish, especially in the context of ecological restoration.

Floodplain soil organic carbon storage in the central Yukon River Basin

NASA Astrophysics Data System (ADS)

Lininger, K.; Wohl, E.

2017-12-01

As rivers transport sediment, organic matter, and large wood, they can deposit those materials in their floodplains, storing carbon. One aspect of the carbon cycle that isn't well understood is how much carbon is stored in rivers and floodplains. There may be more carbon in rivers and floodplains than previously thought. This is important for accounting for all aspects of the carbon cycle, which is the movement of carbon among the land, ocean, and atmosphere. We are quantifying that storage in high latitude floodplains through fieldwork along five rivers in the central Yukon River Basin within the Yukon Flats National Wildlife Refuge in interior Alaska. We find that the geomorphic environment and geomorphic characteristics of rivers influence the spatial distribution of carbon on the landscape, and that floodplains may be disproportionally important for carbon storage compared to other areas. Our study area contains discontinuous permafrost, which is soil that is perennially frozen, and is warming quickly due to climate change, as in other high latitude regions. The large amount of carbon stored in the subsurface and in permafrost in the high latitudes highlights the importance of understanding where carbon is stored within rivers and floodplains in these regions and how long that carbon remains in storage. Our research helps inform how river systems influence the carbon cycle in a region undergoing rapid change.

Hierarchy in factors affecting fish biodiversity in floodplain lakes of the Mississippi Alluvial Valley

USGS Publications Warehouse

Dembkowski, D.J.; Miranda, L.E.

2012-01-01

River-floodplain ecosystems offer some of the most diverse and dynamic environments in the world. Accordingly, floodplain habitats harbor diverse fish assemblages. Fish biodiversity in floodplain lakes may be influenced by multiple variables operating on disparate scales, and these variables may exhibit a hierarchical organization depending on whether one variable governs another. In this study, we examined the interaction between primary variables descriptive of floodplain lake large-scale features, suites of secondary variables descriptive of water quality and primary productivity, and a set of tertiary variables descriptive of fish biodiversity across a range of floodplain lakes in the Mississippi Alluvial Valley of Mississippi and Arkansas (USA). Lakes varied considerably in their representation of primary, secondary, and tertiary variables. Multivariate direct gradient analyses indicated that lake maximum depth and the percentage of agricultural land surrounding a lake were the most important factors controlling variation in suites of secondary and tertiary variables, followed to a lesser extent by lake surface area. Fish biodiversity was generally greatest in large, deep lakes with lower proportions of watershed agricultural land. Our results may help foster a holistic approach to floodplain lake management and suggest the framework for a feedback model wherein primary variables can be manipulated for conservation and restoration purposes and secondary and tertiary variables can be used to monitor the success of such efforts. ?? 2011 Springer Science+Business Media B.V.

Factors affecting fish biodiversity in floodplain lakes of the Mississippi Alluvial Valley

USGS Publications Warehouse

Miranda, Leandro E.; Dembkowski, Daniel J.

2012-01-01

River-floodplain ecosystems offer some of the most diverse and dynamic environments in the world. Accordingly, floodplain habitats harbor diverse fish assemblages. Fish biodiversity in floodplain lakes may be influenced by multiple variables operating on disparate scales, and these variables may exhibit a hierarchical organization depending on whether one variable governs another. In this study, we examined the interaction between primary variables descriptive of floodplain lake large-scale features, suites of secondary variables descriptive of water quality and primary productivity, and a set of tertiary variables descriptive of fish biodiversity across a range of floodplain lakes in the Mississippi Alluvial Valley of Mississippi and Arkansas (USA). Lakes varied considerably in their representation of primary, secondary, and tertiary variables. Multivariate direct gradient analyses indicated that lake maximum depth and the percentage of agricultural land surrounding a lake were the most important factors controlling variation in suites of secondary and tertiary variables, followed to a lesser extent by lake surface area. Fish biodiversity was generally greatest in large, deep lakes with lower proportions of watershed agricultural land. Our results may help foster a holistic approach to floodplain lake management and suggest the framework for a feedback model wherein primary variables can be manipulated for conservation and restoration purposes and secondary and tertiary variables can be used to monitor the success of such efforts.

Neotectonic effects on sinuosity and channel migration, Belle Fourche River, Western South Dakota

USGS Publications Warehouse

Gomez, Basil; Marron, Donna C.

1991-01-01

Short-term instability in the behaviour of a small, meandering alluvial channel is identified from the relation between sinuosity and either floodplain slope or channel slope within 17 reaches along an 81-kilometre section of the Belle Fourche River in western South Dakota. In reaches 1 to 4 and 11 to 17 the channel is relatively stable and sinuosity varies inversely with channel slope. In reaches 5 to 10, sinuosity is positively related to floodplain slope. Sinuosity increases markedly in reaches 5, 6, and 7 (which are immediately downstream from a discontinuity in the long profile of the floodplain) in association with an increase in floodplain slope. Immediately upstream from the discontinuity, bankfull channel depth and sinuosity decrease and the area of the floodplain reworked by meander migration between 1939 and 1981 increases, in association with a decrease in floodplain slope. Channel behaviour in reaches 5 to 10 is best explained as a consequence of neotectonic activity, as indicated by changes in elevation recorded along geodetic survey lines that cross lineaments that may delimit the eastern boundary of the Black Hills uplift. Sinuosity acts as a barometer of the effects of neotectonic activity on alluvial channels. Initial indications of channel and floodplain instability due to neotectonic activity may be derived from evidence of anomalously active channel migration, as documented from photographic or topographic sources.

Consistent negative temperature sensitivity and positive influence of precipitation on growth of floodplain Picea glauca in Interior Alaska

Treesearch

Glenn Patrick Juday; Claire. Alix

2012-01-01

This paper calibrates climate controls over radial growth of floodplain white spruce (Picea glauca (Moench) Voss) and examines whether growth in these populations responds similarly to climate as upland trees in Interior Alaska. Floodplain white spruce trees hold previously unrecognized potential for long-term climate reconstruction because they...

77 FR 75623 - Notice of Intent To Prepare an Environmental Impact Statement for the Plains and Eastern Clean...

Federal Register 2010, 2011, 2012, 2013, 2014

2012-12-21

... and Eastern Clean Line Transmission Project and Notice of Potential Floodplain and Wetland Involvement... and Notice of Potential Floodplain and Wetland Involvement. SUMMARY: The U.S. Department of Energy... of the proposed project may affect floodplains and/or wetlands. This NOI, therefore, also serves as a...

Soil organic matter formation and sequestration across a forested floodplain chronosequence

Treesearch

John D. Wigginton; B. Graeme Lockaby; Carl C. Trettin

2000-01-01

Successional changes in soil organic matter formation and carbon sequestration across a forested floodplain chronosequence were studied at the Savannah river site, National Environmental Research Park, SC, US. Four floodplain sites were selected for study, three of which are in various stages of recovery from impact due to thermal effluent discharge. The fourth is a...

Measuring spatial patterns in floodplains: A step towards understanding the complexity of floodplain ecosystems: Chapter 6

USGS Publications Warehouse

Scown, Murray W.; Thoms, Martin C.; DeJager, Nathan R.; Gilvear, David J.; Greenwood, Malcolm T.; Thoms, Martin C.; Wood, Paul J.

2016-01-01

Floodplains can be viewed as complex adaptive systems (Levin, 1998) because they are comprised of many different biophysical components, such as morphological features, soil groups and vegetation communities as well as being sites of key biogeochemical processing (Stanford et al., 2005). Interactions and feedbacks among the biophysical components often result in additional phenomena occuring over a range of scales, often in the absence of any controlling factors (sensu Hallet, 1990). This emergence of new biophysical features and rates of processing can lead to alternative stable states which feed back into floodplain adaptive cycles (cf. Hughes, 1997; Stanford et al., 2005). Interactions between different biophysical components, feedbacks, self emergence and scale are all key properties of complex adaptive systems (Levin, 1998; Phillips, 2003; Murray et al., 2014) and therefore will influence the manner in which we study and view spatial patterns. Measuring the spatial patterns of floodplain biophysical components is a prerequisite to examining and understanding these ecosystems as complex adaptive systems. Elucidating relationships between pattern and process, which are intrinsically linked within floodplains (Ward et al., 2002), is dependent upon an understanding of spatial pattern. This knowledge can help river scientists determine the major drivers, controllers and responses of floodplain structure and function, as well as the consequences of altering those drivers and controllers (Hughes and Cass, 1997; Whited et al., 2007). Interactions and feedbacks between physical, chemical and biological components of floodplain ecosystems create and maintain a structurally diverse and dynamic template (Stanford et al., 2005). This template influences subsequent interactions between components that consequently affect system trajectories within floodplains (sensu Bak et al., 1988). Constructing and evaluating models used to predict floodplain ecosystem responses to natural and anthropogenic disturbances therefore require quantification of spatial pattern (Asselman and Middelkoop, 1995; Walling and He, 1998). Quantifying these patterns also provides insights into the spatial and temporal domains of structuring processes as well as enabling the detection of self-emergent phenomena, environmental constraints or anthropogenic interference (Turner et al., 1990; Holling, 1992; De Jager and Rohweder, 2012). Thus, quantifying spatial pattern is an important building block on which to examine floodplains as complex adaptive systems (Levin, 1998). Approaches to measuring spatial pattern in floodplains must be cognisant of scale, self-emergent phenomena, spatial organisation, and location. Fundamental problems may arise when patterns observed at a site or transect scale are scaled-up to infer processes and patterns over entire floodplain surfaces (Wiens, 2002; Thorp et al., 2008). Likewise, patterns observed over the entire spatial extent of a landscape can mask important variation and detail at finer scales (Riitters et al., 2002). Indeed, different patterns often emerge at different scales (Turner et al., 1990) because of hierarchical structuring processes (O'Neill et al., 1991). Categorising data into discrete, homogeneous and predefined spatial units at a particular scale (e.g. polygons) creates issues and errors associated with scale and subjective classification (McGarigal et al., 2009; Cushman et al., 2010). These include, loss of information within classified ‘patches’, as well as the ability to detect the emergence of new features that do not fit the original classification scheme. Many of these issues arise because floodplains are highly heterogeneous and have complex spatial organizations (Carbonneau et al., 2012; Legleiter, 2013). As a result, the scale and location at which measurements are made can influence the observed spatial patterns; and patterns may not be scale independent or applicable in different geomorp

Geochemical mapping in polluted floodplains using handheld XRF, geophysical imaging, and geostatistics

NASA Astrophysics Data System (ADS)

Hošek, Michal; Matys Grygar, Tomáš; Popelka, Jan; Kiss, Timea; Elznicová, Jitka; Faměra, Martin

2017-04-01

In the recent years researchers have enjoyed noticeable improvements of portable analytical and geophysical methods, which allow studying floodplain architecture and deciphering pollutant distribution more easily than ever before. Our area of interest was floodplain of the Ploučnice River, particularly a pollution hotspot in Boreček, severely impacted by U mining between the 1970s and late 1980s, in particular a "radioactive flood" in 1981. In the area, we used hand drill coring and in situ (field) analysis of so acquired sediments by handheld X-ray fluorescence spectrometer (XRF), which gave us information about depth profiles of pollutants (Ba, U, Zn) and the Al/Si and Zr/Rb ratios, i.e., proxies for sediment lithology. We found that spatial distribution of pollutants (control by depth and position in the floodplain) is apparently complex and discontinuous. In some places, contamination is buried by a couple decimetres of less polluted sediments, while in other places the peak pollution is near surface, apparently without a straightforward connection with the surface topography and the distance to the river channel. We thus examined the floodplain architecture, the internal structure of the floodplain using two geophysical methods. First of them, dipole electromagnetic profiling (DEMP, also denoted EMP, MP, or Slingram) quickly acquires average electric resistivity in top strata in selected areas, which was actually top 3 m with our particular instrument. Second, electric resistivity tomography (ERT) produces much more detailed information on resistivity with depth resolution of ca 0.5 m to the depth of ca 5 m in selected lines. ERT thus allows identifying boundaries of electric resistivity domains (sediment bodies) and DEMP their spatial distribution. Based on the obtained data, we divided the floodplain to five segments with specific topography, pollution characteristics, and electric resistivity. We suppose that those segments are lithogenetic floodplain units. Those findings must, however, be checked by sediment examination and analysis in selected points. We processed the crucial characteristics obtained by geochemical mapping, namely depth of maximum pollution, amount of contamination, and lithology (Al/Si and Zr/Rb ratios), using geostatistics. Moreover, some parts of floodplain were dated by optically stimulated luminescence (OSL) which revealed, that recycling of top decimetres of floodplain fine fill (silts) in Boreček site has proceeded relatively recently (in decades and centuries) as compared to deeper lying coarser (sandy) strata (millennia). The results of geochemical mapping show complexity of pollution hotspots and need of their integrated interpretation. Key words: Dipole electromagneting profilling, electric resistivity tomography, floodplain contamination, geochemical mapping

The Characteristics of Turbulent Flows on Forested Floodplains

NASA Astrophysics Data System (ADS)

Darby, S. E.; Richardson, K.; Sear, D. A.

2008-12-01

Forested floodplain environments represent the undisturbed land cover of most river systems, but they are under threat from human activities. An understanding of forest floodplain processes therefore has relevance to ecosystem conservation and restoration, and the interpretation of pre-historic river and floodplain evolution. However, relatively little research has been undertaken within forested floodplain environments, a particular limitation being an absence of empirical data regarding the hydraulic characteristics of over bank flows, which inhibits the development of flow, sediment and solute transport models. Forest floodplain flows are strongly modified by floodplain topography and the presence of vegetation and organic debris on the woodland floor. In such instances flow blockage and diversions are common, and there is the possibility of intense turbulence generation, both by wakes and by shear. To address this gap we have undertaken a study based on a floodplain reach located in the Highland Water Research Catchment (southern England), a UK national reference site for lowland floodplain forest streams. Given the difficulties of acquiring spatially-distributed hydraulic data sets during floods, our methodological approach has been to attempt to replicate over bank flow observed at the study site within a laboratory flume. This is necessary to acquire flow velocity data at sufficiently high spatial resolution to evaluate the underlying flow mechanics and has been achieved using (i) a large (21m) flume to achieve 1:1 hydraulic scaling and (ii) a novel method of precisely replicating the floodplain topography within the flume. Specifically, accurate replication of a representative floodplain patch was achieved by creating a 1:1 scale Physical Terrain Model (PTM) from high-density polyurethane using a computer-controlled milling process based on Digital Terrain Model (DTM) data, the latter acquired via terrestrial laser scanning (TLS) survey. The PTM was deployed within the flume immediately downstream of a 8m long hydraulically smooth 'run-in' section with a steady discharge replicating an over bank flow observed in the field, thus achieving 1:1 hydraulic scaling. Above the PTM 3D flow velocity time-series were acquired at each node on a dense (5-10cm horizontal spatial resolution) sampling grid using Acoustic Doppler Velocimeters (ADVs). The data were analysed by visualising the 3D structure of flow velocity and derivative statistics (turbulent intensity, turbulent kinetic energy, Reynolds stresses, etc), combined with quadrant analysis to identify the spatial variation of each quadrant's contribution to the turbulence intensity. These analyses have been used to delineate flow regions dominated by different structures, and construct an empirical model that will be helpful in defining relevant modelling strategies in future research.

Meander morphodynamics over self-formed floodplains: can the migration history affect the future morphology of the river?

NASA Astrophysics Data System (ADS)

Bogoni, M.; Lanzoni, S.; Putti, M.

2017-12-01

Floodplains, and rivers therein, constitute complex systems whose simulation involves modeling of hydrodynamic, morphodynamic, chemical, and biological processes which act over a wide range of time scales (from days to centuries) and affect each other. Self-formed floodplains are produced by the sedimentary processes associated with the migration of river bends and the formation of abandoned oxbow lakes consequent to the cutoff of mature meanders. The erosion and deposition processes at the banks lead to heterogeneities in the surface composition, thus the river may experience faster or slower migration rates depending on the spatial distribution of the erosional resistance. As a consequence, the past spatial configurations of the river (i.e. the migration history) play a key role in shaping the successive river paths.We recently published a paper addressing the modeling of meander morphodynamics over self-formed heterogeneous floodplain. Results show that the heterogeneity in floodplain composition associated with the formation of geomorphic units (i.e., scroll bars and oxbow lakes) and the choice of a reliable flow field model to drive channel migration are two fundamental ingredients for reproducing correctly the long-term morphodynamics of alluvial meanders. We compare numerically generated planforms obtained for different scenarios of floodplain heterogeneity to natural meandering paths, through half meander metrics and spatial distribution of channel curvatures. Statistical and spectral tools disclose the complexity embedded in meandering geometry and the crucial differences between apparently similar configurations.Floodplain heterogeneity affects both the temporal and spatial distributions of meander geometry, and eventually leads to a closer statistical similarity between simulated and natural planform shapes when scroll bars and oxbow lakes left behind are harder to erode than the surrounding floodplain.

Delineating Floodplain in North Korea using Remote Sensing and Geographic Information System

NASA Astrophysics Data System (ADS)

Lim, J.; Lee, K. S.

2015-12-01

Korea has been divided into two countries after World War II. So environmental studies about North Korean are not easy and very limited. There were several flood damages every summer in North Korea since 1995, which induces lots of economic loss and agricultural production decrease. Delineating floodplain is indispensable to estimate the magnitude of flood damage and restore the flooded paddy field after unification. Remote Sensing (RS) can provide opportunity to study inaccessible area. In addition, flooding detection is possible. Several research groups study about flooding disaster using RS. Optical images and microwave images have been used in that field. Also, Digital topographic data have been used for flooding detection. Therefore, the purpose of this study is to investigate the land characteristics of floodplain by delineating floodplain in inaccessible North Korea using Landsat and digital topographic data. Landsat TM 5 images were used in this study. North Korea had severe flooding disaster since 1995. Among them 1995, 2007 and 2012 flooding are known for serious damages. Two Landsat images before and after flooding of each year were used to delineate floodplain. Study areas are Pyongyang City, Nampo City, North and South Hwanghae Province and South Pyongan Province. Floodplain are derived from overlaid classification image and flood-depth map. 1:25,000 scale digital topographic data were used to make flood-depth map. For land cover classification image enhancement and supervised classification with maximum likelihood classifier were used. Training areas were selected by visual interpretation using Daum-map which provides high resolution image of whole North Korea. The spatial characteristics of the floodplain were discussed based on floodplain map delineated in this study.

Agricultural conversion of floodplain ecosystems: implications for groundwater quality.

PubMed

Schilling, Keith E; Jacobson, Peter J; Vogelgesang, Jason A

2015-04-15

With current trends of converting grasslands to row crop agriculture in vulnerable areas, there is a critical need to evaluate the effects of land use on groundwater quality in large river floodplain systems. In this study, groundwater hydrology and nutrient dynamics associated with three land cover types (grassland, floodplain forest and cropland) were assessed at the Cedar River floodplain in southeastern Iowa. The cropland site consisted of newly-converted grassland, done specifically for our study. Our objectives were to evaluate spatial and temporal variations in groundwater hydrology and quality, and quantify changes in groundwater quality following land conversion from grassland to row crop in a floodplain. We installed five shallow and one deep monitoring wells in each of the three land cover types and recorded water levels and quality over a three year period. Crop rotations included soybeans in year 1, corn in year 2 and fallow with cover crops during year 3 due to river flooding. Water table levels behaved nearly identically among the sites but during the second and third years of our study, NO₃-N concentrations in shallow floodplain groundwater beneath the cropped site increased from 0.5 mg/l to more than 25 mg/l (maximum of 70 mg/l). The increase in concentration was primarily associated with application of liquid N during June of the second year (corn rotation), although site flooding may have exacerbated NO₃-N leaching. Geophysical investigation revealed differences in ground conductivity among the land cover sites that related significantly to variations in groundwater quality. Study results provide much-needed information on the effects of different land covers on floodplain groundwater and point to challenges ahead for meeting nutrient reduction goals if row crop land use expands into floodplains. Copyright © 2015 Elsevier Ltd. All rights reserved.

Stratigraphic, sedimentologic, and dendrogeomorphic analyses of rapid floodplain formation along the Rio Grande in Big Bend National Park, Texas

USGS Publications Warehouse

Dean, D.J.; Scott, M.L.; Shafroth, P.B.; Schmidt, J.C.

2011-01-01

The channel of the lower Rio Grande in the Big Bend region rapidly narrows during years of low mean and peak flow. We conducted stratigraphic, sedimentologic, and dendrogeomorphic analyses within two long floodplain trenches to precisely reconstruct the timing and processes of recent floodplain formation. We show that the channel of the Rio Grande narrowed through the oblique and vertical accretion of inset floodplains following channel-widening floods in 1978 and 1990-1991. Vertical accretion occurred at high rates, ranging from 16 to 35 cm/yr. Dendrogeomorphic analyses show that the onset of channel narrowing occurred during low-flow years when channel bars obliquely and vertically accreted fine sediment. This initial stage of accretion occurred by both bedload and suspended-load deposition within the active channel. Vegetation became established on top of these fine-grained deposits during years of low peak flow and stabilized these developing surfaces. Subsequent deposition by moderate floods (between 1.5 and 7 yr recurrence intervals) caused additional accretion at rapid rates. Suspended-sediment deposition was dominant in the upper deposits, resulting in the formation of natural levees at the channel margins and the deposition of horizontally bedded, fining-upward deposits in the floodplain trough. Overall, channel narrowing and floodplain formation occurred through an evolution from active-channel to floodplain depositional processes. High-resolution dendrogeomorphic analyses provide the ability to specifically correlate the flow record to the onset of narrowing, the establishment of riparian vegetation, the formation of natural levees, and ultimately, the conversion of portions of the active channel to floodplains. ?? 2011 Geological Society of America.

Exploring applications of GPR methodology and uses in determining floodplain function of restored streams in the Gulf Coastal Plain, Alabama

NASA Astrophysics Data System (ADS)

Eckes, S. W.; Shepherd, S. L.

2017-12-01

Accurately characterizing subsurface structure and function of remediated floodplains is indispensable in understanding the success of stream restoration projects. Although many of these projects are designed to address increased storm water runoff due to urbanization, long term monitoring and assessment are often limited in scope and methodology. Common monitoring practices include geomorphic surveys, stream discharge, and suspended sediment loads. These data are comprehensive for stream monitoring but they do not address floodplain function in terms of infiltration and through flow. Developing noninvasive methods for monitoring floodplain moisture transfer and distribution will aid in current and future stream restoration endeavors. Ground penetrating radar (GPR) has been successfully used in other physiographic regions for noninvasive and continuous monitoring of (1) natural geomorphic environments including subsurface structure and landform change and (2) soil and turf management to monitor subsurface moisture content. We are testing the viability of these existing methods to expand upon the broad capabilities of GPR. Determining suitability will be done in three parts using GPR to (1) find known buried objects of typical materials used in remediation at measured depths, (2) understand GPR functionality in varying soil moisture content thresholds on turf plots, and (3) model reference, remediated, and impacted floodplains in a case study in the D'Olive Creek watershed located in Baldwin County, Alabama. We hypothesize that these methods will allow us to characterize moisture transfer from precipitation and runoff to the floodplain which is a direct function of floodplain health. The need for a methodology to monitor floodplains is widespread and with increased resolution and mobility, expanding GPR applications may help streamline remediation and monitoring practices.

Modeling small-scale and large-scale flood wave processes as indicators of channel-floodplain connectivity

NASA Astrophysics Data System (ADS)

Byrne, C. F.; Stone, M. C.

2016-12-01

Anthropogenic alterations to rivers and floodplains, either in the context of river engineering or river restoration efforts, have no doubt impacted channel-floodplain connectivity in the majority of developed river systems. River management strategies now often strive to retain or improve ecological integrity of floodplains. Therefore, there is a need to quantify the hydrodynamic processes that have implications for river geomorphology and ecology within the channel-floodplain interface. Because field quantification of these processes is extremely difficult, new methods in hydrodynamic modeling can help to inform river science. This research focused on the assessment of channel-floodplain flow dynamics using two-dimensional hydrodynamic modeling and presents various methods of hydrodynamic process quantification in unsteady flow scenarios. The objectives of this research were to: (1) quantify the small-scale processes of mass and momentum transfer from the main channel to the floodplain; and (2) assess how these processes accrue to meaningful levels to affect the large-scale process of flood wave attenuation. This was achieved by modeling the heavily manipulated Albuquerque Reach of the Rio Grande in New Mexico. Results are presented as mass and momentum fluxes along the channel-floodplain boundaries with a focus on the application of these methods to unsteady flood wave modeling. In addition, quantification of downstream flood wave attenuation is presented as attenuation ratios of discharge and stage, as well as wave celerity. Mass and momentum fluxes during flood waves are shown to be highly variable over spatial and temporal scales and demonstrate the implications of lateral surface connectivity. Results from this research and further application of the methods presented here can help river scientists better understand the dynamics of flood processes especially in the context of process-based river restoration.

Selecting reconnaissance strategies for floodplain surveys

NASA Technical Reports Server (NTRS)

Sollers, S. C.; Rango, A.; Henninger, D. L.

1977-01-01

Multispectral aircraft and satellite data over the West Branch of the Susquehanna River were analyzed to evaluate potential contributions of remote sensing to flood-plain surveys. Multispectral digital classifications of land cover features indicative of floodplain areas were used by interpreters to locate various floodprone area boundaries. The digital approach permitted LANDSAT results to be displayed at 1:24,000 scale and aircraft results at even larger scales. Results indicate that remote sensing techniques can delineate floodprone areas more easily in agricultural and limited development areas as opposed to areas covered by a heavy forest canopy. At this time it appears that the remote sensing data would be best used as a form of preliminary planning information or as an internal check on previous or ongoing floodplain studies. In addition, the remote sensing techniques can assist in effectively monitoring floodplain activities after a community enters into the National Flood Insurance Program.

[Diversity of soil mesofauna in Northern Taiga biogeocenosises of the Kamennaya river basin (Karelia)].

PubMed

Rybalov, L B; Kamaev, I O

2011-01-01

The population of soil mesofauna in the basin of the small river subzone of the northern taiga (Karelia) has been investigated. It was shown that indexes of the number and mass of soil mesofauna in the landscape-ecological row ofbiogeocenosises are maximal in floodplain soils. The taxonomic composition and structure of domination of the soil mesofauna population depends on the location of biogeocenosis in the landscape: earthworms are dominants in riverine floodplain biogeocenosises, and larvae of elaterids and spiders prevail in the places outside of floodplains. The abundance of saprophytic invertebrates in floodplain biogeocenosises results in formation of humus of the mull type. A group of animals with mixed type of nutrition dominates in the places outside of floodplain soils that are related with humus of the moder-mor type. The population of rove beetles (Staphylinidae) allows the division of biogeocenosises into two groups according to their position in the landscape.

Habitat conservation and creation: Invoking the flood-pulse concept to enhance fisheries in the lower Mississippi River

USGS Publications Warehouse

Schramm, H.L.; Eggleton, M.A.; Mayo, R.M.

2000-01-01

Analysis of four years of growth data failed to identify a single temperature or hydrologic variable that consistently accounted for variation in annual growth of catfishes (Ictaluridae). Instead, a composite variable that measured duration of floodplain inundation when water temperature exceeded minima for active feeding was directly related to growth. Results indicated that floodplain inundation have provided little direct energetic benefit to fishes when water temperatures were sub-optimal for active feeding, but floodplain resources were exploited when thermal conditions were sufficient for active feeding and growth. Thus, the flood-pulse concept applies to the lower Mississippi River (LMR) when modified to consider temperature. Managing the existing leveed floodplain to prolong inundation, increase water temperatures during spring flooding, and maintain connectivity of floodplain habitats with the main river channel should benefit fish production in the LMR.

Floodplain biogeochemical processing of floodwaters in the Atchafalaya River Basin during the Mississippi River flood of 2011

USGS Publications Warehouse

Scott, Durelle T.; Keim, Richard F.; Edwards, Brandon L.; Jones, C. Nathan; Kroes, Daniel E.

2014-01-01

The 2011 flood in the Lower Mississippi resulted in the second highest recorded river flow diverted into the Atchafalaya River Basin (ARB). The higher water levels during the flood peak resulted in high hydrologic connectivity between the Atchafalaya River and floodplain, with up to 50% of the Atchafalaya River water moving off channel. Water quality samples were collected throughout the ARB over the course of the flood event. Significant nitrate (NO3-) reduction (75%) occurred within the floodplain, resulting in a total NO3- reduction of 16.6% over the flood. The floodplain was a small but measurable source of dissolved reactive phosphorus (SRP) and ammonium (NH4+). Collectively, these results from this large flood event suggest that enhancing river-floodplain connectivity through freshwater diversions will reduce NO3- loads to the Gulf of Mexico during large annual floods.

The role of floods in particulate organic matter dynamics of a southern Appalachian river-floodplain ecosystem

Treesearch

Mattew A. Neatrour; Jackson R. Webster; Ernest F. Benfield

2004-01-01

We investigated the etfect of a flood on particulate organic matter (POM) dynamics in the floodplain and active channel of the Little Tennessee River In western North Carolina We measured litterfall, leaf breakdown, and floodplain litter (before and after the flood) at 12 sites Annual litterfall (256-562 g m-2 y-1 ) was...

7 CFR Exhibit C to Subpart G of... - Implementation Procedures for the Farmland Protection Policy Act; Executive Order 11988...

Code of Federal Regulations, 2010 CFR

2010-01-01

... designated by a unit of State or local government to be of statewide or local importance and such designation... floodplain whenever either (a) the action or its related activities would be located within a floodplain, or... floodplains and wetlands. Such methods may be either physical or managerial in character. Nonstructural flood...

Using Landsat Thematic Mapper and SPOT Satellite Imagery to inventory wetland plants of the Coeur d'Alene Floodplain

Treesearch

F. M. Roberts; P. E. Gessler

2000-01-01

Landsat Thematic Mapper (TM) and SPOT Satellite Imagery were used to map wetland plant species in thc Coeur d'Alene floodplain in northern Idaho. This paper discusses the methodology used to create a wetland plant species map for the floodplain. Species mapped included common cattail (Typha latifolia); water horse-tail (Equisetum...

Simulation of Rio Grande floodplain inundation Using FLO-2D

Treesearch

J. S. O' Brien; W. T. Fullerton

1999-01-01

Spring floodplain inundation is important to the natural functions of the Rio Grande bosque biological community including cottonwood tree germination and recruitment. To predict floodplain inundation, a two-dimensional flood routing model FLO-2D will be applied to various reaches of the Rio Grande. FLO-2D will assess overbank flooding in terms of the area of...

Risk-based zoning for urbanizing floodplains.

PubMed

Porse, Erik

2014-01-01

Urban floodplain development brings economic benefits and enhanced flood risks. Rapidly growing cities must often balance the economic benefits and increased risks of floodplain settlement. Planning can provide multiple flood mitigation and environmental benefits by combining traditional structural measures such as levees, increasingly popular landscape and design features (green infrastructure), and non-structural measures such as zoning. Flexibility in both structural and non-structural options, including zoning procedures, can reduce flood risks. This paper presents a linear programming formulation to assess cost-effective urban floodplain development decisions that consider benefits and costs of development along with expected flood damages. It uses a probabilistic approach to identify combinations of land-use allocations (residential and commercial development, flood channels, distributed runoff management) and zoning regulations (development zones in channel) to maximize benefits. The model is applied to a floodplain planning analysis for an urbanizing region in the Baja Sur peninsula of Mexico. The analysis demonstrates how (1) economic benefits drive floodplain development, (2) flexible zoning can improve economic returns, and (3) cities can use landscapes, enhanced by technology and design, to manage floods. The framework can incorporate additional green infrastructure benefits, and bridges typical disciplinary gaps for planning and engineering.

California's Yolo Bypass: Evidence that flood control can be compatible with fisheries, wetlands, wildlife, and agriculture

USGS Publications Warehouse

Sommer, T.; Harrell, B.; Nobriga, M.; Brown, R.; Moyle, P.B.; Kimmerer, W.; Schemel, Laurence E.

2001-01-01

Unlike conventional flood control systems that frequently isolate rivers from ecologically-essential floodplain habitat, California's Yolo Bypass has been engineered to allow Sacramento Valley floodwaters to inundate a broad floodplain. From a flood control standpoint, the 24,000 ha leveed floodplain has been exceptionally successful based on its ability to convey up to 80% of the flow of the Sacramento River basin during high water events. Agricultural lands and seasonal and permanent wetlands within the bypass provide key habitat for waterfowl migrating through the Pacific Flyway. Our field studies demonstrate that the bypass seasonally supports 42 fish species, 15 of which are native. The floodplain appears to be particularly valuable spawning and rearing habitat for the splittail (Pogonichthys macrolepidotus), a federally-listed cyprinid, and for young chinook salmon (Oncorhynchus tshawytscha), which use the Yolo Bypass as a nursery area. The system may also be an important source to the downstream food web of the San Francisco Estuary as a result of enhanced production of phytoplankton and detrital material. These results suggest that alternative flood control systems can be designed without eliminating floodplain function and processes, key goals of the 1996 Draft AFS Floodplain Management Position Statement.

The ecology, restoration, and management of southeastern floodplain ecosystems: a synthesis

USGS Publications Warehouse

King, Sammy L.; Sharitz, Rebecca R.; Groninger, John W.; Battaglia, Loretta L.

2009-01-01

Floodplain ecosystems of the southeastern United States provide numerous services to society, but hydrologic and geomorphic alterations, agricultural practices, water quality and availability, and urban development continue to challenge restorationists and managers at multiple spatial and temporal scales. These challenges are further exacerbated by tremendous uncertainty regarding climate and land use patterns and natural variability in these systems. The symposium from which the papers in 2009 ensued was organized to provide a critical evaluation of current natural resource restoration and management practices to support the sustainability of floodplain ecosystem functions in the southeastern United States. In this paper we synthesize these concepts and evaluate restoration and conservation techniques in light of our understanding of these ecosystems. We also discuss current and future challenges and attempt to identify new approaches that may facilitate the long-term sustainability of southeastern floodplain systems. We conclude thatintegration of disciplines and approaches is necessary to meet the floodplain conservation challenges of the coming century. Integration will not only include purposeful dialogue between interdisciplinary natural resource professionals, but it also is necessary to sincerely engage the public about goals, objectives, and desirable outcomes of floodplain ecosystem restoration.

The ecology, restoration, and management of southeastern floodplain ecosystems: A synthesis

USGS Publications Warehouse

King, S.L.; Sharitz, R.R.; Groninger, John W.; Battaglia, Loretta L.

2009-01-01

Floodplain ecosystems of the southeastern United States provide numerous services to society, but hydrologic and geomorphic alterations, agricultural practices, water quality and availability, and urban development continue to challenge restorationists and managers at multiple spatial and temporal scales. These challenges are further exacerbated by tremendous uncertainty regarding climate and land use patterns and natural variability in these systems. The symposium from which the papers in 2009 ensued was organized to provide a critical evaluation of current natural resource restoration and management practices to support the sustainability of floodplain ecosystem functions in the southeastern United States. In this paper we synthesize these concepts and evaluate restoration and conservation techniques in light of our understanding of these ecosystems. We also discuss current and future challenges and attempt to identify new approaches that may facilitate the long-term sustainability of southeastern floodplain systems. We conclude that integration of disciplines and approaches is necessary to meet the floodplain conservation challenges of the coming century. Integration will not only include purposeful dialogue between interdisciplinary natural resource professionals, but it also is necessary to sincerely engage the public about goals, objectives, and desirable outcomes of floodplain ecosystem restoration. ?? 2009, The Society of Wetland Scientists.

Stream and floodplain restoration in a riparian ecosystem disturbed by placer mining

USGS Publications Warehouse

Karle, Kenneth F.; Densmore, Roseann V.

1994-01-01

Techniques for the hydrologic restoration of placer-mined streams and floodplains were developed in Denali National Park and Preserve Alaska, USA. The hydrologic study focused on a design of stream and floodplain geometry using hydraulic capacity and shear stress equations. Slope and sinuosity values were based on regional relationships. Design requirements include a channel capacity for a 1.5-year (bankfull) discharge and a floodplain capacity for a 1.5- to 100-year discharge. Concern for potential damage to the project from annual flooding before natural revegetation occurs led to development of alder (Alnus crispa) brush bars to dissipate floodwater energy and encourage sediment deposition. The brush bars, constructed of alder bundles tied together and anchored laterally adjacent to the channel, were installed on the floodplain in several configurations to test their effectiveness. A moderate flood near the end of the two-year construction phase of the project provided data on channel design, stability, floodplain erosion, and brush bar effectiveness. The brush bars provided substantial protection, but unconsolidated bank material and a lack of bed armour for a new channel segment led to some bank erosion, slope changes and an increase in sinuosity in several reaches of the study area.

The influence of the Amazonian floodplain ecosystems on the trace element dynamics of the Amazon River mainstem (Brazil).

PubMed

Viers, Jérôme; Barroux, Guénaël; Pinelli, Marcello; Seyler, Patrick; Oliva, Priscia; Dupré, Bernard; Boaventura, Geraldo Resende

2005-03-01

The purpose of this paper is to forecast the role of riverine wetlands in the transfer of trace elements. One of the largest riverine wetlands in the world is the floodplain (várzea) of the Amazon River and its tributaries (Junk and Piedade, 1997). The central Amazon wetlands are constituted by a complex network of lakes and floodplains, named várzeas, that extend over more than 300,000 km2 (Junk, W.J., The Amazon floodplain--a sink or source for organic carbon? In Transport of Carbon and Minerals in Major World Rivers, edited by E.T. Degens, S. Kempe, R. Herrera, SCOPE/UNEP; 267-283, 1985.) and are among the most productive ecosystems in the world due to the regular enrichment in nutrients by river waters In order to understand if the adjacent floodplain of Amazon River have a significant influence on the trace element concentrations and fluxes of the mainstem, the concentrations of selected elements (i.e., Al, Mn, Fe, Co, Cu, Mo, Rb, Sr, Ba, and U) have been measured in the Amazon River water (Manacapuru Station, Amazonas State, Brazil) and in lake waters and plants (leaves) from a várzea(Ilha de Marchantaria, Amazonas State, Brazil) during different periods of the hydrological cycle. Four plant species (two perennial species: Pseudobombax munguba and Salix humboldtiana, and two annual herbaceous plants: Echinochloa polystachya and Eichhornia crassipes) were selected to represent the ecological functioning of the site. Time series obtained for dissolved Mn and Cu (<0.20 microm) in Amazon River water could not be explained by tributary mixing or instream processes only. Therefore, the contribution of the waters transiting the floodplains should be considered. These results suggest that the chemical composition of the waters draining these floodplains is controlled by reactions occurring at sediment-water and plant-water interfaces. Trace elements concentrations in the plants (leaves) vary strongly with hydrological seasonality. Based on the concentration data and the biological productivity of floodplain ecosystems, a first order approximation of trace element storage (permanent or temporary) in the vegetation of these floodplains was made. It was found that floodplain-mainstem elemental fluxes make a significant contribution to the dissolved flux of the Amazon River. This study is part of the Brazilian_French joint research program Hybam (Hydrology and Geochemistry of the Amazonian Basin).

Floodplain Condition and Water Framework Directive River Classification in England: Evidence of a Disconnect.

NASA Astrophysics Data System (ADS)

Bentley, S.

2017-12-01

The European Union Water Framework Directive came into force in October 2000 committing European Union member states to achieve Good Ecological Status for all water bodies. By 2015 29% of rivers across England had achieved this level suggesting that these watercourse units are now functioning well. This study utilises recently published land cover data for England clipped to the floodplain boundary as defined by the 100 year return period discharge to examine the state of valley bottom vegetation and function for these Good Status rivers. Agricultural use of floodplain areas is high with cereal and horticulture covering an average of 24% and pasture accounting for some 37% of the area. Maximum values increase to 77% and 92% respectively. In all cases wetland accounts for less than 2% of the floodplain and rough grassland averages 7%. Such significant and widespread alteration to floodplain vegetation character suggests that the ecological functioning of this component of the fluvial system has been severely negatively impacted calling into question the Water Framework Directive status level. This is a fault of the Water Framework Directive process which only explicitly evaluates the hydromorphological component of the fluvial system for high status rivers preferring to infer functioning from biological indicators that are focused on in-channel assessments. The fundamental omission of floodplain condition in the Water Framework Directive process will result in only partial achievement of the original goals of the Directive with the majority of Europe's floodplains remaining in a highly degraded, non-functional state.

Urban Infrastructure, Channel-Floodplain Morphology and Flood Flow Patterns

NASA Astrophysics Data System (ADS)

Miller, A. J.; Smith, J. A.; Nelson, C. B.

2006-12-01

The relationship between the channel and the floodplain in urban settings is heavily influenced by (1) altered watershed hydrologic response and frequency distribution of flows, (2) channel enlargement resulting from altered hydrology under conditions of limited sediment supply, (3) direct modification of channels and floodplains for purposes of erosion mitigation, flood protection, commercial development and creation of public amenities, (4) valley constrictions and flow obstructions associated with bridges, culverts, road embankments and other types of floodplain encroachment causing fragmentation or longitudinal segmentation of the riparian corridor. Field observation of inundation patterns associated with recurring floods in the Baltimore metropolitan area is used in combination with 2-dimensional hydraulic modeling to simulate patterns of floodplain inundation and to explore the relationships between magnitude and shape of the flood hydrograph, morphology of the urban channel-floodplain system, and the frequency and extent of floodplain inundation. Case studies include a July 2004 flood associated with a 300-year 2-hour rainfall in a small (14.2 km2) urban watershed, as well as several other events caused by summer thunderstorms with shorter recurrence intervals that generated an extraordinary flood response. The influence of urban infrastructure on flood inundation and flow patterns is expressed in terms of altered (and hysteretic) stage-discharge relationships, stepped flood profiles, rapid longitudinal attenuation of flood waves, and transient flow reversals at confluences and constrictions. Given the current level of interest in restoration measures these patterns merit consideration in planning future development and mitigation efforts.

Effects of moisture limitation on tree growth in upland and floodplain forest ecosystems in interior Alaska

Treesearch

John. Yarie

2008-01-01

The objective of this study was to examine the impact of summer throughfall on the growth of trees, at upland and floodplain locations, in the vicinity of Fairbanks, Alaska. Corrugated clear plastic covers were installed under the canopy of floodplain balsam poplar/white spruce stands and upland hardwood/white spruce stands to control soil moisture recharge as a result...

Present status and approaches for the sustainable development of community based fish culture in seasonal floodplains of Bangladesh.

PubMed

Rahman, M F; Jalal, K C A; Jahan, Nasrin; Kamaruzzaman, B Y; Ara, R; Arshad, A

2012-06-15

Coordination among the different stakeholders at policy planning, implementation and target beneficiary level, particularly among the agencies responsible for development and management of water resources, agriculture and fisheries, is essential for overall sustainable development. Stocking of larger fingerlings at suitable stocking densities of endemic (rohu, catla, mrigal) and exotic (silver carp, bighead carp, common carp/mirror carp) species should be stocked at varying proportion. Floodplain fish production depends only on the natural fertility of the water bodies. Technological interventions should include the installation of low cost bamboo fencing at water inlet and outlet points and setting of ring culverts for maintaining suitable levels of water for fish culture without hampering the production of rice and other crops in the intervention areas, selective stocking with native and exotic carps, restricted fishing for certain period of time and guarding. It is expected to exert positive influences in enhancing the standing crop and biodiversity of non-stocked species of fishes in the intervention seasonal floodplain. Entry of fish larvae, hatchlings and young fry of wild non-stocked fishes into the seasonal floodplains because of large fence spacing (approximately 1.0 cm), could restrict fishing for certain period, undisturbed habitat and guarding could contribute to higher productivity and enhancement of fish biodiversity in the seasonal floodplains. Proper motivation and effective cooperation of the beneficiaries are extremely important to culture fish in the seasonal floodplains under community based management system. Institutional support and constant vigilance from the Department of Fisheries (DoF) and local administrations are indispensable to ensure the sustainability of fish culture initiatives in the seasonal floodplains. Active participation and involvement of the local community people in all stages of fish culture operation beginning from selection of floodplains, formation of floodplain management committee, planning of fish culture activities, exercise of technical intervention, selective stocking with large fingerlings, guarding, monitoring and supervision, adopting harvesting strategies, marketing and distribution of benefits are extremely essential to ensure sustainability of the program. Mutual trust, sense of respect and good working relationship among the committee members are the basic social elements required for the success of community based fish culture initiatives.

Interactive Mapping of Inundation Metrics Using Cloud Computing for Improved Floodplain Conservation and Management

NASA Astrophysics Data System (ADS)

Bulliner, E. A., IV; Lindner, G. A.; Bouska, K.; Paukert, C.; Jacobson, R. B.

2017-12-01

Within large-river ecosystems, floodplains serve a variety of important ecological functions. A recent survey of 80 managers of floodplain conservation lands along the Upper and Middle Mississippi and Lower Missouri Rivers in the central United States found that the most critical information needed to improve floodplain management centered on metrics for characterizing depth, extent, frequency, duration, and timing of inundation. These metrics can be delivered to managers efficiently through cloud-based interactive maps. To calculate these metrics, we interpolated an existing one-dimensional hydraulic model for the Lower Missouri River, which simulated water surface elevations at cross sections spaced (<1 km) to sufficiently characterize water surface profiles along an approximately 800 km stretch upstream from the confluence with the Mississippi River over an 80-year record at a daily time step. To translate these water surface elevations to inundation depths, we subtracted a merged terrain model consisting of floodplain LIDAR and bathymetric surveys of the river channel. This approach resulted in a 29000+ day time series of inundation depths across the floodplain using grid cells with 30 m spatial resolution. Initially, we used these data on a local workstation to calculate a suite of nine spatially distributed inundation metrics for the entire model domain. These metrics are calculated on a per pixel basis and encompass a variety of temporal criteria generally relevant to flora and fauna of interest to floodplain managers, including, for example, the average number of days inundated per year within a growing season. Using a local workstation, calculating these metrics for the entire model domain requires several hours. However, for the needs of individual floodplain managers working at site scales, these metrics may be too general and inflexible. Instead of creating a priori a suite of inundation metrics able to satisfy all user needs, we present the usage of Google's cloud-based Earth Engine API to allow users to define and query their own inundation metrics from our dataset and produce maps nearly instantaneously. This approach allows users to select the time periods and inundation depths germane to managing local species, potentially facilitating conservation of floodplain ecosystems.

Hydrologic conditions, habitat characteristics, and occurrence of fishes in the Apalachicola River floodplain, Florida; second annual report of progress, October 1993-September 1994

USGS Publications Warehouse

Light, Helen M.; Darst, Melanie R.; Grubbs, J.W.

1995-01-01

This report describes progress and interim results of the second year of a 4-year study. The purpose of the 4-year study is to describe aquatic habitat types in the Apalachicola River floodplain and quantify the amount of habitat inundated by the river at various stages. Final results will be used to determine possible effects of altered flows on floodplain habitats and their associated fish communities. The study is being conducted by the U.S. Geological Survey in cooperation with the Northwest Florida Water Management District as part of a comprehensive study of water needs throughout two large river basins in Florida, Georgia, and Alabama. By the end of the second year, approxi- mately 80 to 90 percent of field data collection was completed. Water levels at 56 floodplain and main channel locations at study sites were read numerous times during low water and once or twice during high water. Rating curves estimating the relationship between stage at a floodplain site and flow of the Apalachicola River at Chattahoochee are presented for 3 sites in the upper river. Elevation, substrate type, and amount of vegetative structure were described at 27 cross sections representing eight different floodplain tributary types at upper, middle, and lower river study sites. A summary of substrate and structure information from all cross sections is presented. Substrate and structure characteristics of floodplain habitats inundated when river flow was at record low flow, mean annual low flow, and mean flow are described for 3 cross sections in the upper river. Digital coverage of high-altitude infra-red aerial photography was processed for use in a Geographic Information System which will be used to map aquatic habitats in the third year of the study. A summary of the literature on fish utilization of floodplain habitats is described. Eighty-one percent of the species collected in the main channel of the Apalachicola River are known to occur in floodplain habitats of eastern rivers.

Floodplain construction of the Rio Grande at El Paso, Texas, USA: response to Holocene climate change

NASA Astrophysics Data System (ADS)

Hall, Stephen A.; Peterson, John A.

2013-04-01

The Rio Grande is one of the larger rivers in North America, and the development of its floodplain is related to Holocene climate and climate change. The late Pleistocene through early Holocene channel is characterized by a meander or braided system with lateral cutting and backfilling, resulting in the valley-wide deposition of massive to cross-bedded, fine-to-medium textured sand. The late Pleistocene-early Holocene floodplain is also the sand source for the adjacent Bolson sand sheet. The sand sheet stopped accumulating new sand 5000 yrs ago, an event directly related to the shutting off of the sand supply caused by the deposition of overbank muds that covered and sealed the floodplain surface. During the middle Holocene, the river may have dried intermittently with the floodplain becoming deflated and local sand dunes forming on the floodplain. After 5000 yrs the climate was less arid and the river shifted to a regime of increased flooding and overbank deposition of silt and clay. By 2500 yrs, a late Holocene period of wet climate resulted in further overbank deposition and the formation of a cumulic Mollisol across the floodplain, the Socorro paleosol. The period of wet climate corresponds to the Audubon Neoglacial and active rock glaciers in the southern Rocky Mountains, speleothem growth in nearby caves, and other evidence for wet-cool conditions in the region. After 1000 yrs, the climate became drier, and the deposition and accumulation of overbank muds by the flooding Rio Grande came to a halt. Even though the river has flooded often in historic times, and presumably during late prehistoric times as well, there is little evidence for deposition of overbank sediments on the floodplain since A.D. 1000. Accordingly, the present-day surface of the Lower Valley is ten centuries old. Three channels occur on the US side of the Lower Valley floodplain, and during the past 2500 yrs stream flow has shifted from one to the other by the avulsion process of channel reoccupation, although most flow has been in the Rio Grande channel, the largest of the three.

Records of transient avulsion-related river patterns in ancient deposits: evidence for different styles of channel-floodplain coupling

NASA Astrophysics Data System (ADS)

Hajek, E. A.; Edmonds, D.; Millard, C.; Toms, L.; Fogaren, C.

2012-12-01

River mobility and avulsion are important controls on how course and fine sediment are distributed across alluvial basins. In some systems, broad distributary channel networks that form during channel avulsions contribute significantly to overbank aggradation within the basin and help transport relatively coarse sediment from the channel out onto the floodplain. In contrast, avulsion-related deposits are virtually absent in other systems, which primarily avulse either through incision or with no significant aggradational phase preceding channel relocation; in these systems, overbank sedimentation primarily comprises relatively fine floodplain deposits. In order to constrain the conditions under which distributary-channel networks develop during avulsions, we evaluate channel, avulsion, and floodplain deposits in several ancient units including the Ferris (Maastrichtian/Paleocene, Wyoming), Fort Union (Paleocene, Wyoming), Wasatch (Paleocene/Eocene, Colorado), and Willwood (Paleocene/Eocene, Wyoming) formations. Ancient deposits afford the opportunity to observe multiple (tens to hundreds) channel-avulsion realizations and evaluate characteristic spatial and temporal variability in channel, avulsion, and floodplain deposits within a basin. In each formation, spatial relationships and grain-size distributions of channel, proximal-overbank, distal-overbank, and, where present, avulsion deposits are compared. The thickness, width, and stratigraphic frequency of crevasse-splay and avulsion deposits are characterized in each formation, and paleosol development is documented in order to provide information about relative differences in floodplain conditions (particularly sedimentation rate and floodplain drainage) throughout each unit. We compare these results to modern systems and numerical models. Several formations contain abundant and distinctive evidence of prograding sediment wedges preceding avulsed channels (Willwood Formation and some members of the Wasatch formation), while others contain virtually no avulsion-associated deposits (Ferris Formation). The Fort Union Formation and one member of the Wasatch Formation show a mix of both. These results largely reflect depositional processes and not preservation bias within ancient deposits. Evidence from ancient deposits also suggests sediment partitioning between channels and floodplains was mediated by crevasse-splay production and avulsion, where some systems were "tuned" to produce large splay deposits and other systems produced only infrequent, small splays. Systems that readily produced splay deposits are associated with more prominent avulsion deposits, and splay production seems to be influenced by the particle-size distribution of sediment carried in the channel and floodplain drainage conditions (where abundant fine-sand and coarse-silt sediment and relatively well-drained floodplain conditions promote crevasse-splay production). Avulsion deposits reflect a transient distributary phase associated with a marked increase in local overbank sedimentation rates, but this phase is not ubiquitous to all avulsive systems. The persistence of conditions that promote or inhibit crevasse-splay and avulsion-deposit production may strongly influence channel-floodplain coupling in aggrading fluvial systems.

A project optimization for small watercourses restoration in the northern part of the Volga-Akhtuba floodplain by the geoinformation and hydrodynamic modeling

NASA Astrophysics Data System (ADS)

Voronin, Alexander; Vasilchenko, Ann; Khoperskov, Alexander

2018-03-01

The project of small watercourses restoration in the northern part of the Volga-Akhtuba floodplain is considered together with the aim of increasing the watering of the territory during small and medium floods. The topography irregularity, the complex structure of the floodplain valley consisting of large number of small watercourses, the presence of urbanized and agricultural areas require careful preliminary analysis of the hydrological safety and efficiency of geographically distributed project activities. Using the digital terrain and watercourses structure models of the floodplain, the hydrodynamic flood model, the analysis of the hydrological safety and efficiency of several project implementation strategies has been conducted. The objective function values have been obtained from the hydrodynamic calculations of the floodplain territory flooding for virtual digital terrain models simulating alternatives for the geographically distributed project activities. The comparative efficiency of several empirical strategies for the geographically distributed project activities, as well as a two-stage exact solution method for the optimization problem has been studied.

Impacts of Hurricane Katrina on floodplain forests of the Pearl River: Chapter 6A in Science and the storms-the USGS response to the hurricanes of 2005

USGS Publications Warehouse

Faulkner, Stephen; Barrow, Wylie; Couvillion, Brady R.; Conner, William; Randall, Lori; Baldwin, Michael

2007-01-01

Floodplain forests are an important habitat for Neotropical migratory birds. Hurricane Katrina passed through the Pearl River flood plain shortly after making landfall. Field measurements on historical plots and remotely sensed data were used to assess the impact of Hurricane Katrina on the structure of floodplain forests of the Pearl River.

Impact of Dike Structures on Sediment Transport in the Alluvial Rivers

DTIC Science & Technology

2012-09-05

recognize their accomplishments. • Arizona Floodplain Management Scholarship —One graduate student (Mary Yeager) working on the project received the...Arizona Floodplain Management Scholarship ($2000), which is to award outstanding graduate students in the area of water resource and floodplain... scholarships or fellowships for further studies in science, mathematics, engineering or technology fields: 3.00 1.00 2.00 0.00 3.00 1.00

Freshwater recharge into a shallow saline groundwater system, Cooper Creek floodplain, Queensland, Australia

NASA Astrophysics Data System (ADS)

Cendón, Dioni I.; Larsen, Joshua R.; Jones, Brian G.; Nanson, Gerald C.; Rickleman, Daniel; Hankin, Stuart I.; Pueyo, Juan J.; Maroulis, Jerry

2010-10-01

SummaryFreshwater lenses have been identified as having penetrated the shallow regional saline groundwater beneath the Cooper Creek floodplain near Ballera (south-west Queensland). Piezometers were installed to evaluate the major-element chemistry along a floodplain transect from a major waterhole (Goonbabinna) to a smaller waterhole (Chookoo) associated with a sand dune complex. The floodplain consists of 2-7 m of impermeable mud underlain by unconsolidated fluvial sands with a saline watertable. Waterholes have in places scoured into the floodplain. The transect reveals that groundwater recharge takes place through the base of the waterholes at times of flood scour, but not through the floodplain mud. Total dissolved solids rise with distance from the waterhole and independently of the presence of sand dunes. Stable water isotopes (δ 2H and δ 18O) confirm that recharge is consistent with, and dependant on, monsoonal flooding events. Following floods, the waterholes self-seal and retain water for extended periods, with sulfate-δ 34S and δ 18O isotopes suggesting bacterial reduction processes within the hyporheic zone, and limited interaction between the surface water and groundwater during no-flow conditions. The area occupied by the freshwater lenses (TDS < 5000 mg/L) is locally asymmetrical with respect to the channel flow direction, extending down gradient along distances of ˜300 m.

Floodplain forest loss and changes in forest community composition and structure in the upper Mississippi River: a wildlife habitat at risk

USGS Publications Warehouse

Knutson, M.G.; Klaas, E.E.

1998-01-01

Large floodplain forests represent a threatened and endangered type of ecosystem in the United States. Estimates of cumulative losses of floodplain forest range from 57% to 95% at different locations within the continental United Stales. Floodplain forests of the Upper Mississippi River (UMR) have significantly declined in extent due to agriculture, lock and dam construction, and urban development since European settlement. We collected data on shrubs, herbs, and trees from 56 floodplain forest plots in 1992 and compared our results with a previous analysis of historical tree data from the same area recorded by the General Land Office Survey in the 1840s. Acer saccharinum strongly dominates among mature trees and its relative dominance has increased over time. Salix spp. And Betula nigra have declined in relative dominance. Tree sizes are similar to those of presettlement forests, but present forests have fewer trees. The lack of early successional tree species and a trend toward an increasing monoculture of A. Saccharinum in the mature stages indicate problems with regeneration. Because floodplain forests represent a rare habitat type, losses and changes in habitat quality could pose serious problems for wildlife that depend upon these habitats, especially birds.

Wetland tree transpiration modified by river-floodplain connectivity

USGS Publications Warehouse

Allen, Scott T.; Krauss, Ken W.; Cochran, J. Wesley; King, Sammy L.; Keim, Richard F.

2016-01-01

Hydrologic connectivity provisions water and nutrient subsidies to floodplain wetlands and may be particularly important in floodplains with seasonal water deficits through its effects on soil moisture. In this study, we measured sapflow in 26 trees of two dominant floodplain forest species (Celtis laevigata and Quercus lyrata) at two hydrologically distinct sites in the lower White River floodplain in Arkansas, USA. Our objective was to investigate how connectivity-driven water table variations affected water use, an indicator of tree function. Meteorological variables (photosynthetically active radiation and vapor pressure deficit) were the dominant controls over water use at both sites; however, water table variations explained some site differences. At the wetter site, highest sapflow rates were during a late-season overbank flooding event, and no flood stress was apparent. At the drier site, sapflow decreased as the water table receded. The late-season flood pulse that resulted in flooding at the wetter site did not affect the water table at the drier site; accordingly, higher water use was not observed at the drier site. The species generally associated with wetter conditions (Q. lyrata) was more positively responsive to the flood pulse. Flood water subsidy lengthened the effective growing season, demonstrating ecological implications of hydrologic connectivity for alleviating water deficits that otherwise reduce function in this humid floodplain wetland.

Modelling highly variable environmental factors to assess potential microbial respiration in complex floodplain landscapes

PubMed Central

Tritthart, Michael; Welti, Nina; Bondar-Kunze, Elisabeth; Pinay, Gilles; Hein, Thomas; Habersack, Helmut

2011-01-01

The hydrological exchange conditions strongly determine the biogeochemical dynamics in river systems. More specifically, the connectivity of surface waters between main channels and floodplains is directly controlling the delivery of organic matter and nutrients into the floodplains, where biogeochemical processes recycle them with high rates of activity. Hence, an in-depth understanding of the connectivity patterns between main channel and floodplains is important for the modelling of potential gas emissions in floodplain landscapes. A modelling framework that combines steady-state hydrodynamic simulations with long-term discharge hydrographs was developed to calculate water depths as well as statistical probabilities and event durations for every node of a computation mesh being connected to the main river. The modelling framework was applied to two study sites in the floodplains of the Austrian Danube River, East of Vienna. Validation of modelled flood events showed good agreement with gauge readings. Together with measured sediment properties, results of the validated connectivity model were used as basis for a predictive model yielding patterns of potential microbial respiration based on the best fit between characteristics of a number of sampling sites and the corresponding modelled parameters. Hot spots of potential microbial respiration were found in areas of lower connectivity if connected during higher discharges and areas of high water depths. PMID:27667961

Deriving Flood-Mediated Connectivity between River Channels and Floodplains: Data-Driven Approaches

NASA Astrophysics Data System (ADS)

Zhao, Tongtiegang; Shao, Quanxi; Zhang, Yongyong

2017-03-01

The flood-mediated connectivity between river channels and floodplains plays a fundamental role in flood hazard mapping and exerts profound ecological effects. The classic nearest neighbor search (NNS) fails to derive this connectivity because of spatial heterogeneity and continuity. We develop two novel data-driven connectivity-deriving approaches, namely, progressive nearest neighbor search (PNNS) and progressive iterative nearest neighbor search (PiNNS). These approaches are illustrated through a case study in Northern Australia. First, PNNS and PiNNS are employed to identify flood pathways on floodplains through forward tracking. That is, progressive search is performed to associate newly inundated cells in each time step to previously inundated cells. In particular, iterations in PiNNS ensure that the connectivity is continuous - the connection between any two cells along the pathway is built through intermediate inundated cells. Second, inundated floodplain cells are collectively connected to river channel cells through backward tracing. Certain river channel sections are identified to connect to a large number of inundated floodplain cells. That is, the floodwater from these sections causes widespread floodplain inundation. Our proposed approaches take advantage of spatial-temporal data. They can be applied to achieve connectivity from hydro-dynamic and remote sensing data and assist in river basin planning and management.

Zoogeography, taxonomy, and conservation of West Virginia’s Ohio River floodplain crayfishes (Decapoda, Cambaridae)

PubMed Central

Loughman, Zachary J.; Simon, Thomas P.

2011-01-01

Abstract The crayfish fauna of West Virginia consists of 23 species and several undescribed taxa. Most survey efforts documenting this fauna have been conducted in lotic waterways throughout the Appalachian plateau, Allegheny Mountains, and Ridge and Valley physiographic provinces. Bottomland forests, swamps, and marshes associated with large river floodplain such as the Ohio River floodplain historically have been under-surveyed in the state. These habitats harbor the richest primary burrowing crayfish fauna in West Virginia, and are worthy of survey efforts. In an effort to fill this void, the crayfish fauna of West Virginia’s Ohio River floodplain was surveyed from 2004 through 2009. From this survey, nine species from four genera were documented inhabiting the floodplain. Zoogeography, biology, and conservation status is provided for all nine crayfishes. The dominant genus along the floodplain is Cambarus, which includes Cambarus (Cambarus) carinirostris, Cambarus (Cambarus) bartonii cavatus, Cambarus (Procambarus) robustus and Cambarus (Tubericambarus) thomai. Cambarus (Tubericambarus) thomai is the most prevalent burrowing species occurring along the floodplain. The genus Orconectes consists of two native species, Orconectes (Cambarus) obscurus and Orconectes (Cambarus) sanbornii; and two invasive taxa, Orconectes (Gremicambarus) virilis and Orconectes (Procambarus) rusticus. Orconectes (Cambarus) obscurus has experienced a range extension to the south and occupies streams formerly occupied by Orconectes (Cambarus) sanbornii. Both invasive taxa were allied with anthropogenic habitats and disturbance gradients. The genera Fallicambarus and Procambarus are represented by a single species. Both Fallicambarus (Cambarus) fodiens and Procambarus (Orconectes) acutus are limited to the historic preglacial Marietta River Valley. PMID:21594135

Predicting the fate of sediment and pollutants in river floodplains.

PubMed

Malmon, Daniel V; Dunne, Thomas; Reneau, Steven L

2002-05-01

Geological processes such as erosion and sedimentation redistribute toxic pollutants introduced to the landscape by mining, agriculture, weapons development, and other human activities. A significant portion of these contaminants is insoluble, adsorbing to soils and sediments after being released. Geologists have long understood that much of this sediment is stored in river floodplains, which are increasingly recognized as important nonpoint sources of pollution in rivers. However, the fate of contaminated sediment has generally been analyzed using hydrodynamic models of in-channel processes, ignoring particle exchange with the floodplain. Here, we present a stochastic theory of sediment redistribution in alluvial valley floors that tracks particle-bound pollutants and explicitly considers sediment storage within floodplains. We use the theory to model the future redistribution and radioactive decay of 137Cs currently stored on sediment in floodplains at the Los Alamos National Laboratory (LANL) in New Mexico. Model results indicate that floodplain storage significantly reduces the rate of sediment delivery from upper Los Alamos Canyon, allowing 50% of the 137Cs currently residing in the valley floor to decay radioactively before leaving LANL. A sensitivity analysis shows that the rate of sediment overturn in the valley (and hence, the total amount of radioactive 137Cs predicted to leave LANL) is significantly controlled by the rate of sediment exchange with the floodplain. Our results emphasize that flood plain sedimentation and erosion processes can strongly influence the redistribution of anthropogenic pollutants in fluvial environments. We introduce a new theoretical framework for examining this interaction, which can provide a scientific basis for decision-making in a wide range of river basin management scenarios.

Earth Observations taken by Expedition 30 crewmember

NASA Image and Video Library

2012-02-05

ISS030-E-090012 (5 Feb. 2012) --- The Parana River floodplain along the Mato Grosso–Sao Paulo border, Brazil is featured in this image photographed by an Expedition 30 crew member on the International Space Station. The Parana River appears as a wide, blue strip across this photograph, with muddy brown water of the smaller Verde River entering from the northwest (top left). An extensive wetland (dark green) occupies most of the left half of the image, where the floodplain of the river reaches a width of 11 kilometers. The thin line of a road crossing the floodplain also gives a sense of scale. Above the Parana–Verde confluence (center) the floodplain is much narrower. The floodplain is generated by sediments delivered by both rivers. Evidence for this is that the entire surface of the floodplain is crisscrossed by the wider traces of former Parana R. channels as well as numerous narrower traces of the Verde R. The floodplains along both rivers are bordered by numerous rectangular agricultural fields. Dominant crops along this part of the Parana River are coffee, corn and cotton. Turbid water, such as that in the Verde River, is common in most rivers that drain plowed agricultural land as some topsoil is washed into local rivers after rains. A long tendril of brown water extends from the Verde R. into the main channel of the Parana River where it hugs the west bank, remaining unmixed for many kilometers. This effectively shows the direction of river flow from orbit (right to left for the Parana, upper left to center for the Verde).

Trace metal dynamics in floodplain soils of the river Elbe: a review.

PubMed

Schulz-Zunkel, Christiane; Krueger, Frank

2009-01-01

This paper reviews trace metal dynamics in floodplain soils using the Elbe floodplains in Germany as an example of extraordinary importance because of the pollution level of its sediments and soils. Trace metal dynamics are determined by processes of retention and release, which are influenced by a number of soil properties including pH value, redox potential, organic matter, type and amount of clay minerals, iron-, manganese- and aluminum-oxides. Today floodplains act as important sinks for contaminants but under changing hydraulic and geochemical conditions they may also act as sources for pollutants. In floodplains such changes may be extremes in flooding or dry periods that particularly lead to altered redox potentials and that in turn influence the pH value, the mineralization of organic matter as well as the charge of the pedogenic oxides. Such reactions may affect the bioavailability of trace metals in soils and it can be clearly seen that the bioavailability of metals is an important factor for estimating trace metal remobilization in floodplain soils. However as bioavailability is not a constant factor, there is still a lack of quantification of metal mobilization particularly on the basis of changing geochemical conditions. Moreover, mobile amounts of metals in the soil solution do not indicate to which extent remobilized metals will be transported to water bodies or plants and therefore potentially have toxicological effects. Consequently, floodplain areas still need to be taken into consideration when studying the role and behavior of sediments and soils for transporting pollutants within river systems, particularly concerning the Water Framework Directive.

Past and predicted future changes in the land cover of the Upper Mississippi River floodplain, USA

USGS Publications Warehouse

De Jager, N. R.; Rohweder, J.J.; Nelson, J.C.

2013-01-01

This study provides one historical and two alternative future contexts for evaluating land cover modifications within the Upper Mississippi River (UMR) floodplain. Given previously documented changes in land use, river engineering, restoration efforts and hydro-climatic changes within the UMR basin and floodplain, we wanted to know which of these changes are the most important determinants of current and projected future floodplain land cover. We used Geographic Information System data covering approximately 37% of the UMR floodplain (3232 km2) for ca 1890 (pre-lock and dam) and three contemporary periods (1975, 1989 and 2000) across which river restoration actions have increased and hydro-climatic changes have occurred. We further developed two 50-year future scenarios from the spatially dependent land cover transitions that occurred from 1975 to 1989 (scenario A) and from 1989 to 2000 (scenario B) using Markov models.Land cover composition of the UMR did not change significantly from 1975 to 2000, indicating that current land cover continues to reflect historical modifications that support agricultural production and commercial navigation despite some floodplain restoration efforts and variation in river discharge. Projected future land cover composition based on scenario A was not significantly different from the land cover for 1975, 1989 or 2000 but was different from the land cover of scenario B, which was also different from all other periods. Scenario B forecasts transition of some forest and marsh habitat to open water by the year 2050 for some portions of the northern river and projects that some agricultural lands will transition to open water in the southern portion of the river. Future floodplain management and restoration planning efforts in the UMR should consider the potential consequences of continued shifts in hydro-climatic conditions that may occur as a result of climate change and the potential effects on floodplain land cover.

Solid-Phase Fe Speciation along the Vertical Redox Gradients in Floodplains using XAS and Mössbauer Spectroscopies.

PubMed

Chen, Chunmei; Kukkadapu, Ravi K; Lazareva, Olesya; Sparks, Donald L

2017-07-18

Properties of Fe minerals are poorly understood in natural soils and sediments with variable redox conditions. In this study, we combined 57 Fe Mössbauer and Fe K-edge X-ray absorption spectroscopic (XAS) techniques to assess solid-phase Fe speciation along the vertical redox gradients of floodplains, which exhibited a succession of oxic, anoxic, and suboxic-oxic zones with increasing depth along the vertical profiles. The incised stream channel is bounded on the east by a narrow floodplain and a steep hillslope, and on the west by a broad floodplain. In the eastern floodplain, the anoxic conditions at the intermediate horizon (55-80 cm) coincided with lower Fe(III)-oxides (particularly ferrihydrite), in concurrence with a greater reduction of phyllosilicates(PS)-Fe(III) to PS-Fe(II), relative to the oxic near-surface and sandy gravel layers. In addition, the anoxic conditions in the eastern floodplain coincided with increased crystallinity of goethite, relative to the oxic layers. In the most reduced intermediate sediments at 80-120 cm of the western floodplain, no Fe(III)-oxides were detected, concurrent with the greatest PS-Fe(III) reduction (PS-Fe(II)/Fe(III) ratio ≈ 1.2 (Mössbauer) or 0.8 (XAS)). In both oxic near-surface horizon and oxic-suboxic gravel aquifers beneath the soil horizons, Fe(III)-oxides were mainly present as ferrihydrite with a much less amount of goethite, which preferentially occurred as nanogoethite or Al/Si-substituted goethite. Ferrihydrite with varying crystallinity or impurities such as organic matter, Al or Si, persisted under suboxic-oxic conditions in the floodplain. This study indicates that vertical redox gradients exert a major control on the quantity and speciation of Fe(III) oxides as well as the oxidation state of structural Fe in PS, which could significantly affect nutrient cycling and carbon (de)stabilization.

Stakeholder-led science: engaging resource managers to identify science needs for long-term management of floodplain conservation lands

USGS Publications Warehouse

Bouska, Kristin L.; Lindner, Garth; Paukert, Craig P.; Jacobson, Robert B.

2016-01-01

Floodplains pose challenges to managers of conservation lands because of constantly changing interactions with their rivers. Although scientific knowledge and understanding of the dynamics and drivers of river-floodplain systems can provide guidance to floodplain managers, the scientific process often occurs in isolation from management. Further, communication barriers between scientists and managers can be obstacles to appropriate application of scientific knowledge. With the coproduction of science in mind, our objectives were the following: (1) to document management priorities of floodplain conservation lands, and (2) identify science needs required to better manage the identified management priorities under nonstationary conditions, i.e., climate change, through stakeholder queries and interactions. We conducted an online survey with 80 resource managers of floodplain conservation lands along the Upper and Middle Mississippi River and Lower Missouri River, USA, to evaluate management priority, management intensity, and available scientific information for management objectives and conservation targets. Management objectives with the least information available relative to priority included controlling invasive species, maintaining respectful relationships with neighbors, and managing native, nongame species. Conservation targets with the least information available to manage relative to management priority included pollinators, marsh birds, reptiles, and shore birds. A follow-up workshop and survey focused on clarifying science needs to achieve management objectives under nonstationary conditions. Managers agreed that metrics of inundation, including depth and extent of inundation, and frequency, duration, and timing of inundation would be the most useful metrics for management of floodplain conservation lands with multiple objectives. This assessment provides guidance for developing relevant and accessible science products to inform management of highly dynamic floodplain environments. Although the problems facing managers of these lands are complex, products focused on a small suite of inundation metrics were determined to be the most useful to guide the decision making process.

Organic carbon and nitrogen export from a tropical dam-impacted floodplain system

NASA Astrophysics Data System (ADS)

Zurbrügg, R.; Suter, S.; Lehmann, M. F.; Wehrli, B.; Senn, D. B.

2012-06-01

Tropical floodplains play an important role in organic matter transport, storage, and transformation between headwaters and oceans. However, the fluxes and quality of organic carbon (OC) and organic nitrogen (ON) in tropical river-floodplain systems are not well constrained. We explored the quantity and characteristics of dissolved and particulate organic matter (DOM and POM) in the Kafue River flowing through the Kafue Flats (Zambia). The Kafue Flats are a tropical dam-impacted river-floodplain system in the Zambezi River basin. During the flooding season, >80% of the Kafue River water passed through the floodplain, mobilizing large quantities of OC and ON, which resulted in a net export of 75 kg OC km-2 d-1 and 2.9 kg ON km-2 d-1, 80% of which was in the dissolved form. Mass budget estimates showed that ON export, denitrification, and burial caused an annual deficit of ~21 000 t N yr-1 in the Kafue Flats. A N isotope balance and the δ15N of DON and PON suggest that N-fixation must level out the large N losses. The elemental C:N ratio of ~20, the δ13C values of higher than -24‰, and spectroscopic properties (excitation-emission matrices) showed that DOM in the river was mainly of terrestrial origin. Despite a threefold increase in OC loads due to inputs from the floodplain, the river DOM characteristics remained relatively constant along the sampled 400-km river reach. This suggested that floodplain DOM had similar properties than DOM from the upstream reservoir. In contrast, based on its low δ13C of -29‰ and the C:N ratio of ~8, POM originated from phytoplankton production in the upstream reservoir and in the floodplain. While the reservoir had little impact on DOM properties, terrestrial POM was efficiently trapped and, instead, phytoplankton-derived POM was discharged to the downstream Kafue Flats.

Understanding the value of local ecological knowledge and practices for habitat restoration in human-altered floodplain systems: a case from Bangladesh.

PubMed

Mamun, Abdullah-Al

2010-05-01

Worldwide there is a declining trend in natural fish catch (FAO, The state of world fisheries and aquaculture. http://www.fao.org/documents/show_cdr.asp?url_file=/docrep/007/y5600e/y5600e00.htm , 2002) and Bangladesh is no exception. The vast inland fisheries of Bangladesh have been declining over the years, largely a result of human alteration of the aquatic habitats arising from human interventions in the floodplain systems such as the establishment of water control structures which favor agricultural production but reduce fish habitats. It can be assumed that conventional management measures are not adequate to conserve natural fisheries and exploring alternative knowledge systems to complement existing management is warranted. This paper focuses on local ecological knowledge and several other local practices held by fishers engaging directly with floodplain ecosystems. These knowledge systems and practices may be valuable tools for understanding ecosystems processes and related changes and developing local level responses to avert negative consequences of such changes. This may help in devising alternatives to ecosystem management and the conservation of floodplain fish habitats of Bangladesh and elsewhere in the world. This study was conducted in a natural depression (locally called beel) and its surrounding floodplain system located in north central Bangladesh which has become highly degraded. The results of the study indicate that the fishers and local users of the floodplain ecosystems are rich in local ecological knowledge concerning the hydrology of the floodplains and small lakes, the habitat preferences of fish, the role of agricultural crops on fish habitats, and the impact of habitat human interventions in aquatic ecosystems. Given the apparent inadequacy of the present management regime, this article argues for an inclusion of local knowledge and practices into habitat management as a more holistic approach to floodplain habitat restoration and conservation that encourages multi-level cooperation and which builds on diversified knowledge systems.

Sedimentation patterns in floodplains of the Mekong Delta - Vietnam

NASA Astrophysics Data System (ADS)

Van Manh, Nguyen; Merz, Bruno; Viet Dung, Nguyen; Apel, Heiko

2013-04-01

Quantification of floodplain sedimentation during the flood season in the Mekong Delta (MD) plays a very important role in the assessment of flood deposits for a sustainable agro-economic development. Recent studies on floodplain sedimentation in the region are restricted to small pilot sites because of the large extend of the Delta, and the complex channel. This research aims at a quantification of the sediment deposition in floodplains of the whole Mekong Delta, and to access the impacts of the upstream basin development on the sedimentation in the Delta quantitatively. To achieve this, a suspended sediment transport model is developed based on the quasi-2D hydrodynamic model of the whole Mekong Delta developed by Dung et al. (2011). The model is calibrated and validated using observed data derived from several sediment measurement campaigns in channel networks and floodplains. Measured sediment data and hydrodynamic model quantify the spatio-temporal variability of sediment depositions in different spatial units: individual dyke compartments, and the sub-regions Plain of Reeds, Long Xuyen Quadrangle and the area between Tien River and Hau River. It is shown that the distribution of sediment deposition over the delta is highly depended on the flood magnitude, that in turn drives the operation policy of flood control systems in floodplains of the Mekong Delta. Thus, the sedimentation distribution is influenced by the protection level of the dyke systems in place and the distance to the Tien River and Hau River, the main branches of the Mekong in the Delta. This corroborates the main findings derived from data analysis obtained from a small scale test site by Hung et al, (2011, 2012a). Moreover, the results obtained here underlines the importance of the main channels for the sediment transport into the floodplains, and the deposition rate in floodplains is strongly driven by the intake locations and the distance from these to the main channels as well.

Tipping points in Anthropocene fluvial dynamics

NASA Astrophysics Data System (ADS)

Notebaert, Bastiaan; Broothaerts, Nils; Verstraeten, Gert; Berger, Jean-François; Houbrechts, Geoffrey

2016-04-01

Many rivers have undergone dramatic changes over the last millennia due to anthropogenic on- and offsite impacts. These changes have important implications for the geomorphic and hydrological functioning of the river. In this study we compare the influence of large-scaled off-site anthropogenic impact on three European river systems. We do this using traditional geomorphological methods, combined with palynological and archaeological data; for each catchment a Holocene sediment budget was constructed. The Dijle catchment is located in the central Belgian loess belt, and has undergone intense agriculture for at least the last 2000 year. Pre-Anthropocene floodplain are big marshes lacking a well-established river channel. Anthropogenic deforestation in the headwaters resulted in a sediment pulse from the Bronze Age on. In the main floodplain sediments gradually covered the peat layer, starting near a newly formed river channel and expanding over time towards the floodplain edges. In contrast, this transition is abrupt in the smaller tributary floodplains. Comparison with palynological data shows that this abrupt transition occurs when human impact reaches a certain threshold. The Valdaine region is located in the French Pre-Alps. Floodplain deposition increased over time since the Neolithic time period due to human induced and fire related soil erosion. This general aggradation trend is however interrupted by three major river incision phases which are caused by human land abandonment and dry periods. A second major change in floodplain geomorphology occurs during the High Roman Period and the last 800 year: the fine-grained meandering river changes to a gravel loaded braided river. During this period the upstream mountain reaches became a major sediment source due to deforestation, possibly combined with climate change. During the last century reforestation and land abandonment has led to a new incision phases, and floodplain are now a major source of gravel while the river partially maintains its braided pattern. The Amblève River in the Belgian Ardennes uplands underwent less dramatic changes. Large parts of the catchment are deforested during the last 700 years, leading to an increase in floodplain sedimentation. Despite this major sediment pulse, change in floodplain morphology remained limited to an increase in bank height. We argue that a combination of floodplain and channel morphology, the fine texture of supplied sediment and the high stream power of channel forming events result is a system that is less sensitive to change. Also the relative short time of impact may play a role. These three examples demonstrate the varying impact of human deforestation on floodplain geomorphology. For the Dijle and Valdaine region this lead to dramatic changes once a certain tipping point is reached. In contrast the Amblève river is more resilient to human impact due to its specific morphological setting. The morphology of the catchments and the nature of supplied sediments plays a major role in the sensitivity of fluvial systems to environmental impact. Once the tipping points are reached, it is difficult for the river to revert to its original state and floodplains remain highly impacted.

Organic matter compositions and loadings in soils and sediments along the Fly River, Papua New Guinea

NASA Astrophysics Data System (ADS)

Goñi, Miguel A.; Moore, Eric; Kurtz, Andrew; Portier, Evan; Alleau, Yvan; Merrell, David

2014-09-01

The compositions and loadings of organic matter in soils and sediments from a diverse range of environments along the Fly River system were determined to investigate carbon transport and sequestration in this region. Soil horizons from highland sites representative of upland sources have organic carbon contents (%OC) that range from 0.3 to 25 wt%, carbon:nitrogen ratios (OC/N) that range from 7 to 25 mol/mol, highly negative stable carbon isotopic compositions (δ13Corg < -26‰) and variable concentrations of lignin phenols (1 < LP < 5 mg/100 mg OC). These compositions reflect inputs from local vegetation, with contributions from bedrock carbon in the deeper mineral horizons. Soils developed on the levees of active floodplains receive inputs of allochthonous materials by overbank deposition as well as autochthonous inputs from local vegetation. In the forested upper floodplain reaches, %OC contents are lower than upland soils (0.8-1.5 wt%) as are OC/N ratios (9-15 mol/mol) while δ13Corg (-25 to -28‰) and LP (2-6 mg/100 mg OC) values are comparable to upland soils. These results indicate that organic matter present in these active floodplain soils reflect local (primarily C3) vegetation inputs mixed with allochthonous organic matter derived from eroded bedrock. In the lower reaches of the floodplain, which are dominated by swamp grass vegetation, isotopic compositions were less negative (δ13Corg > -25‰) and non-woody vegetation biomarkers (cinnamyl phenols and cutin acids) more abundant relative to upper floodplain sites. Soils developed on relict Pleistocene floodplain terraces, which are typically not flooded and receive little sediment from the river, were characterized by low %OC contents (<0.6 wt%), low OC/N ratios (<9 mol/mol), more positive δ13Corg signatures (>-21‰) and low LP concentrations (∼3 mg/100 mg OC). These relict floodplain soils contain modern carbon that reflects primarily local (C3 or C4) vegetation sources. Total suspended solids collected along the river varied widely in overall concentrations (1 < TSS < 9000 mg/L), %OC contents (0.1-60 wt%), OC/N ratios (7-17 mol/mol) and δ13Corg signatures (-26 to -32‰). These compositions reflect a mixture of C3 vascular plants and freshwater algae. However, little of this algal production appears to be preserved in floodplain soils. A comparison of organic carbon loadings of active floodplain soils (0.2 and 0.5 mg C/m2) with previous studies of actively depositing sediments in the adjacent delta-clinoform system (0.4-0.7 mg C/m2) indicates that Fly River floodplain sediments are less effective at sequestering organic carbon than deltaic sediments. Furthermore, relict Pleistocene floodplain sites with low or negligible modern sediment accumulation rates display significantly lower loadings (0.1-0.2 mg C/m2). This deficit in organic carbon likely reflects mineralization of sedimentary organic carbon during long term oxidative weathering, further reducing floodplain carbon storage.

Geomorphic and vegetation processes of the Willamette River floodplain, Oregon: current understanding and unanswered science questions

USGS Publications Warehouse

Wallick, J. Rose; Jones, Krista L.; O'Connor, Jim E.; Keith, Mackenzie K.; Hulse, David; Gregory, Stanley V.

2013-01-01

4. How is the succession of native floodplain vegetation shaped by present-day flow and sediment conditions? Answering these questions will produce baseline data on the current distributions of landforms and habitats (question 1), the extent of the functional floodplain (question 2), and the effects of modern flow and sediment regimes on future floodplain landforms, habitats, and vegetation succession (questions 3 and 4). Addressing questions 1 and 2 is a logical next step because they underlie questions 3 and 4. Addressing these four questions would better characterize the modern Willamette Basin and help in implementing and setting realistic targets for ongoing management strategies, demonstrating their effectiveness at the site and basin scales, and anticipating future trends and conditions.

Relations among floodplain water levels, instream dissolved-oxygen conditions, and streamflow in the lower Roanoke River, North Carolina, 1997-2001

USGS Publications Warehouse

Bales, Jerad D.; Walters, Douglas A.

2004-01-01

The lower Roanoke River corridor in North Carolina contains a floodplain of national significance. Data from a network of 1 streamflow-measurement site, 13 river-stage sites, 13 floodplain water-level sites located along 4 transects, and 5 in situ water-quality monitoring sites were used to characterize temporal and spatial variations of floodplain and river water levels during 1997-2000 and to describe dissolved-oxygen conditions in the lower Roanoke River for the period 1998-2001. Major differences in the relation of floodplain inundation to flow occurred both among sites at a given transect and among transects. Several floodplain sites were inundated for the full range of flow conditions measured during the study. These included one site on the Big Swash transect (at about river kilometer 119); one site on the Broadneck Swamp transect (river kilometer 97), which was inundated 91 percent of the time during the study; one site on the Devils Gut transect (river kilometer 44), which was inundated throughout the study; and three sites on the Cow Swamp transect (near river kilometer 10). The relation of floodplain inundation depth to Roanoke River flow was highly variable among sites. There was no relation between flow and inundation depth at one of the Big Swash sites or at any of the four Cow Swamp sites. At two of the Big Swash transect sites, there was some relation between inundation depth and 10-day mean flow for flows greater than 700 cubic meters per second. A relatively strong relation between inundation depth and 10-day mean flow occurred at two of the Broadneck Swamp sites and, to a lesser degree, at two of the Devils Gut transect sites. There was much greater interannual variability in floodplain water levels, as represented by the difference between the maximum and minimum daily water level for a given calendar date during January-May and September-October than during the summer and late fall months. If data from this study are representative of long-term conditions, then this means that there is less uncertainty about what future floodplain water levels will be during June-August and November-December than during other months. Rates of ground-water decline, primarily due to evapotranspiration, were fairly similar at all sites, ranging from about 3 to 4 centimeters per day. For a 10-day mean flow of 300 cubic meters per second, an evaporative loss of 2 centimeters per day is equal to about 56 cubic meters per second. Evapotranspiration rates are much lower during the fall and winter months, so losses of river flow to floodplain processes likely are much lower during those months. The ground-water gradient at most sites was from the floodplain to the river, indicating a potential for ground-water movement into the river from the floodplain. At two of the Devils Gut sites, however, the water level often was higher in the river than in the floodplain when floodplain sites were not inundated. This indicates that there is a potential for river water to move as ground water from the river into the floodplain. It seems likely that this feature observed at the Devils Gut transect occurs elsewhere in the lower Roanoke River corridor. Dissolved-oxygen concentrations typically decrease with increasing distance from Roanoke Rapids Dam. During the 1998-2001 study period, the median dissolved-oxygen concentration at Halifax (river kilometer 187), the upstream-most station, was 8.4 milligrams per liter, and the median concentration at the downstream-most station (NC-45, bottom sensor; river kilometer 2.6) was 6.6 milligrams per liter. Several synoptic measurements of dissolved-oxygen concentration down the river identified the presence of a dissolved-oxygen sag in the vicinity of Halifax, with some recovery of concentrations between Halifax and about Scotland Neck at river kilometer 156. Data from the synoptic measurements also indicated that the greatest rate of dissolved-oxygen change with distance along the riv

Prediction and uncertainty analysis of surface and groundwater exchange in a Rhine floodplain in south-west Germany

NASA Astrophysics Data System (ADS)

Maier, Nadine; Breuer, Lutz; Kraft, Philipp

2017-04-01

Inundations and the resulting exchange between surface water and groundwater are of importance for all floodplain ecosystems. Because of the high groundwater level in floodplains and the groundwater dependence of floodplain vegetation habitat models of floodplains should include detailed information of groundwater and surface water dynamics. Such models can, for example, serve as a basis for restoration measures, focusing on the re-establishment of rare species. To capture these groundwater and surface water dynamics we use a distributed model approach to simulate the groundwater levels in a floodplain stream section of the Rhine in Hesse, Germany (14.8 km2). This area is part of the large nature reserve "Kühkopf-Knoblochsaue" and hosts rare and endangered flora and fauna. We developed a physical-deterministic model of a floodplain to simulate the groundwater situation and the flooding events in the floodplain. The model is built with the Catchment Modeling Framework (CMF) and includes the interaction of groundwater and surface water flow. To reduce the computation time of the model, we used a simple flood distribution scheme instead of solving the St. Venant equation for surface water fluxes. The floodplain is split into two sub-regions, according to the two nature reserve regions with the same model setup. Each model divides the study area laterally into irregular polygonal cells (270 - 400) with different sizes (114 - 480'000 m2), based on similar elevation and land use. For each sub-region the water level of the Rhine and the groundwater levels of three monitoring wells at the boundary of the model area are used as driving factors. As predictor variables we use observation data from four to six different groundwater monitoring wells in the sub-regions. For each model we run 5,000 simulations following a Latin Hypercube sampling procedure to investigate parameter uncertainty and derive behavioral model runs. We received RMSEs between 0.18 and 0.28 m for the different groundwater wells for the calibration period of 2.5 years and RMSEs between 0.16 and 0.23 m for the validation period of 9.5 years. Finally, we derived hydrological predictors (e.g. longest flooding period, amount of flooding days during the vegetation period, etc) from the model runs for following habitat models.

Evaluation of CAESAR-Lisflood as a tool for modelling river channel change and floodplain sediment residence times.

NASA Astrophysics Data System (ADS)

Feeney, Christopher; Smith, Hugh; Chiverrell, Richard; Hooke, Janet; Cooper, James

2017-04-01

Sediment residence time represents the duration of particle storage, from initial deposition to remobilisation, within reservoirs such as floodplains. Residence time influences rates of downstream redistribution of sediment and associated contaminants and is a useful indicator of landform stability and hence, preservation potential of alluvial archives of environmental change. River channel change controls residence times, reworking sediments via lateral migration, avulsion and incision through floodplain deposits. As reworking progresses, the floodplain age distribution is 'updated', reflecting the time since 'older' sediments were removed and replaced with 'younger' ones. The relationship between ages and the spatial extents they occupy can be used to estimate the average floodplain sediment residence times. While dating techniques, historic maps and remote sensing can reconstruct age distributions from historic reworking, modelling provides advantages, including: i) capturing detailed river channel changes and resulting floodplain ages over longer timescales and higher resolutions than from historic mapping, and ii) control over inputs to simulate hypothetical scenarios to investigate the effects of different environmental drivers on residence times. CAESAR-Lisflood is a landform evolution model capable of simulating variable channel width, divergent flow, and both braided and meandering planforms. However, the model's ability to accurately simulate channel changes requires evaluation if it is to be useful for quantitative evaluation of floodplain sediment residence times. This study aims to simulate recent historic river channel changes along ten 1 km reaches in northern England. Simulation periods were defined by available overlapping historic map and mean daily flow datasets, ranging 27-39 years. LiDAR-derived 2 m DEMs were modified to smooth out present-day channels and burn in historic channel locations. To reduce run times, DEMs were resampled to coarser resolutions based on the size of the channel and historic rate of lateral channel migration. Separate pre-defined coarse and finer channel bed and floodplain grain size distributions were used, respectively, in combination with constructed reach DEMs for model simulations. Calibration was performed by modifying selected parameters to obtain best fits between observed and modelled channel planforms. Initial simulations suggest the model can broadly reproduce observed planform change and is comparable in terms of channel sinuosities and the mean radius of curvature. As such, CAESAR-Lisflood may provide a useful tool for evaluating floodplain sediment residence times under environmental change scenarios.

The Role of Conjoining (Tie) Channels in Lowland Floodplain Development and Lake Infilling

NASA Astrophysics Data System (ADS)

Rowland, J. C.; Dietrich, W. E.; Day, G.; Lepper, K.; Wilson, C. J.

2003-12-01

In simple models of lowland river systems, water and sediment enter the main stem via tributary and secondary channels and are only redistributed to the floodplain during overbank and crevasse splay events. Along numerous river systems across the globe, however, water and sediment are regularly exchanged between the river and off river water bodies via stable, narrow channels. These channels, known as tie channels on the Fly River in Papua New Guinea and batture channels along the lower Mississippi, are largely overlooked but important components of floodplain sediment dispersal where they exist. These channels become pathways of sediment dispersal to the floodplain system when elevated river stages force sediment-laden flows into the off-river water bodies. On the Fly River, it is estimated that about 50% of the sediment delivery to the floodplain is via these channels, and along low gradient tributary channels during flood driven flow reversals. During low flow, tie channels serve to drain the floodplain. With the outgoing flows, large amounts sediment can be carried and lost to the floodplain; floodplain lakes progressively infill with sediment as the mouth of these channels steadily prograde lakeward. These lake deposits not only become significant stratigraphic components of floodplains (traditionally referred to as clay plugs), but are important local sinks recording hundreds to thousands of years of river history. As with all sinks, the proper interpretation of these stratigraphic records requires understanding the processes by which sediment is delivered to the sink and how these processes alter the paleohydraulic and climatic signals of interest. We have conducted field investigations of conjoining channels in Papua New Guinea (the Fly and Strickland Rivers), Louisiana (Raccourci Old River ~ 65 km upriver of Baton Rouge) and Alaska (Birch Creek). These field investigations include extensive surveys of both cross and along channel morphological trends, grain size characteristics, water levels and geochronological sampling using optically stimulated luminescence (OSL). Across all systems channel morphology is similar and exhibit scale independence, however, channel size and rates of progradation are directly related to the size of the main stem river. Through these studies and ongoing scaled modeling we are examining the morphodynamics that lead to the formation, advancement and stability of these unique self formed channels.

Preferential flow paths in paraglacial catchments: first order controls on the long-term stability of 'biodiversity hotspots' in a changing climate

NASA Astrophysics Data System (ADS)

Grocott, Michael; Kettridge, Nick; Bradley, Chris; Milner, Alexander

2016-04-01

Groundwater (GW) -fed streams within paraglacial floodplains are considered 'biodiversity hotspots', given their importance as an aquatic ecosystem and role in supporting valuable riverine habitat patches within paraglacial environments. However, it is anticipated that throughout the 21st Century hydrologic regimes of paraglacial systems in arctic, sub-arctic, and alpine regions globally will experience substantial changes, as a consequence of anthropogenic climate change. Declining glacial coverage, shrinking winter snowpack, earlier spring melt, rising permafrost melt and increasing relative importance of groundwater will all cause major changes in the water balance of paraglacial catchments. This research explored the importance of preferential flow pathways (PFPs) as conduits of subsurface flow across paraglacial floodplains, and their role in sustaining 'biodiversity hotspots'. Furthermore, it considered the role of PFPs in hillslope-floodplain connectivity within paraglacial systems and the significance of colluvial deposits as a key water source to GW-fed streams on paraglacial floodplains. An intra-catchment scale field study within ungauged catchments was conducted in Denali National Park & Preserve, Alaska, during 2013 and 2014. The research utilised hydrogeomorphic and hydrochemical field techniques to address the aims outlined above. Surface infiltration and slug tests identified significant spatial heterogeneity in hydraulic conductivity (K) across the surface and subsurface of paraglacial floodplains, indicating the presence of PFPs. Furthermore, spatiotemporal variation in geochemical tracers (major ions) within surface and subsurface flow paths established the role of multiple, discrete flow paths (PFPs) in sustaining GW-fed streamflow on floodplains. Finally, hydrograph separations confirmed the significant contribution made by colluvial deposits (e.g. talus slopes) to sustaining GW-fed streamflow on paraglacial research. This research suggests PFPs are a fundamental first order control upon the occurrence of 'biodiversity hotspots' within paraglacial floodplains, and highlights their role as an important conduit for hillslope-floodplain connectivity. Given the expected changes in the hydrological dynamics of paraglacial catchments this research raises questions about the long-term stability of GW-fed streams, and whether the increasing relative importance of groundwater sources (e.g. from colluvium) can sustain flow of GW-fed streams. In addition glacial retreat and associated long-term declines in sediment yields could have negative implications for the development and renewal of PFPs across paraglacial floodplains, which would be detrimental to the persistence of 'biodiversity hotspots'.

Organic carbon and nitrogen export from a tropical dam-impacted floodplain system

NASA Astrophysics Data System (ADS)

Zurbrügg, R.; Suter, S.; Lehmann, M. F.; Wehrli, B.; Senn, D. B.

2013-01-01

Tropical floodplains play an important role in organic matter transport, storage, and transformation between headwaters and oceans. However, the fluxes and quality of organic carbon (OC) and organic nitrogen (ON) in tropical river-floodplain systems are not well constrained. We explored the quantity and characteristics of dissolved and particulate organic matter (DOM and POM, respectively) in the Kafue River flowing through the Kafue Flats (Zambia), a tropical river-floodplain system in the Zambezi River basin. During the flooding season, > 80% of the Kafue River water passed through the floodplain, mobilizing large quantities of OC and ON, which resulted in a net export of 69-119 kg OC km-2 d-1 and 3.8-4.7 kg ON km-2 d-1, 80% of which was in the dissolved form. The elemental C : N ratio of ~ 20, the comparatively high δ13C values of -25‰ to -21‰, and its spectroscopic properties (excitation-emission matrices) showed that DOM in the river was mainly of terrestrial origin. Despite a threefold increase in OC loads due to inputs from the floodplain, the characteristics of the riverine DOM remained relatively constant along the sampled 410-km river reach. This suggests that floodplain DOM displayed properties similar to those of DOM leaving the upstream reservoir and implied that the DOM produced in the reservoir was relatively short-lived. In contrast, the particulate fraction was 13C-depleted (-29‰) and had a C : N ratio of ~ 8, which indicated that POM originated from phytoplankton production in the reservoir and in the floodplain, rather than from plant debris or resuspended sediments. While the upstream dam had little effect on the DOM pool, terrestrial particles were retained, and POM from algal and microbial sources was released to the river. A nitrogen mass balance over the 2200 km2 flooded area revealed an annual deficit of 15 500-22 100 t N in the Kafue Flats. The N isotope budget suggests that these N losses are balanced by intense N-fixation. Our study shows that the Kafue Flats are a significant local source of OC and ON to downstream ecosystems and illustrates how the composition of riverine OM can be altered by dams and floodplains in tropical catchments.

Mimicking floodplain reconnection and disconnection using 15N mesocosm incubations

NASA Astrophysics Data System (ADS)

Welti, N.; Bondar-Kunze, E.; Mair, M.; Bonin, P.; Wanek, W.; Pinay, G.; Hein, T.

2012-11-01

Floodplain restoration changes the nitrate delivery pattern and dissolved organic matter pool in backwaters, though the effects these changes have are not yet well known. We performed two mesocosm experiments on floodplain sediments to quantify the nitrate metabolism in two types of floodplains. Rates of denitrification, dissimilatory nitrate reduction to ammonium (DNRA) and anammox were measured using 15N-NO3 tracer additions in mesocosms of undisturbed floodplain sediments originating from (1) restored and (2) disconnected sites in the Alluvial Zone National Park on the Danube River downstream of Vienna, Austria. DNRA rates were an order of magnitude lower than denitrification and neither rate was affected by changes in nitrate delivery pattern or organic matter quality. Anammox was not detected at any of the sites. Denitrification was out-competed by assimilation, which was estimated to use up to 70% of the available nitrate. Overall, denitrification was higher in the restored sites, with mean rates of 5.7 ± 2.8 mmol N m-2 h-1 compared to the disconnected site (0.6 ± 0.5 mmol N m-2 h-1). In addition, ratios of N2O : N2 were lower in the restored site indicating a more complete denitrification. Nitrate addition had neither an effect on denitrification, nor on the N2O : N2 ratio. However, DOM (dissolved organic matter) quality significantly changed the N2O : N2 ratio in both sites. Addition of riverine-derived organic matter lowered the N2O : N2 ratio in the disconnected site, whereas addition of floodplain-derived organic matter increased the N2O : N2 ratio in the restored site. These results demonstrate that increasing floodplains hydrological connection to the main river channel increases nitrogen retention and decreases nitrous oxide emissions.

Linking river, floodplain, and vadose zone hydrology to improve restoration of a coastal river affected by saltwater intrusion.

PubMed

Kaplan, D; Muñoz-Carpena, R; Wan, Y; Hedgepeth, M; Zheng, F; Roberts, R; Rossmanith, R

2010-01-01

Floodplain forests provide unique ecological structure and function, which are often degraded or lost when watershed hydrology is modified. Restoration of damaged ecosystems requires an understanding of surface water, groundwater, and vadose (unsaturated) zone hydrology in the floodplain. Soil moisture and porewater salinity are of particular importance for seed germination and seedling survival in systems affected by saltwater intrusion but are difficult to monitor and often overlooked. This study contributes to the understanding of floodplain hydrology in one of the last bald cypress [Taxodium distichum (L.) Rich.] floodplain swamps in southeast Florida. We investigated soil moisture and porewater salinity dynamics in the floodplain of the Loxahatchee River, where reduced freshwater flow has led to saltwater intrusion and a transition to salt-tolerant, mangrove-dominated communities. Twenty-four dielectric probes measuring soil moisture and porewater salinity every 30 min were installed along two transects-one in an upstream, freshwater location and one in a downstream tidal area. Complemented by surface water, groundwater, and meteorological data, these unique 4-yr datasets quantified the spatial variability and temporal dynamics of vadose zone hydrology. Results showed that soil moisture can be closely predicted based on river stage and topographic elevation (overall Nash-Sutcliffe coefficient of efficiency = 0.83). Porewater salinity rarely exceeded tolerance thresholds (0.3125 S m(-1)) for bald cypress upstream but did so in some downstream areas. This provided an explanation for observed vegetation changes that both surface water and groundwater salinity failed to explain. The results offer a methodological and analytical framework for floodplain monitoring in locations where restoration success depends on vadose zone hydrology and provide relationships for evaluating proposed restoration and management scenarios for the Loxahatchee River.

Digital floodplain mapping and an analysis of errors involved

USGS Publications Warehouse

Hamblen, C.S.; Soong, D.T.; Cai, X.

2007-01-01

Mapping floodplain boundaries using geographical information system (GIS) and digital elevation models (DEMs) was completed in a recent study. However convenient this method may appear at first, the resulting maps potentially can have unaccounted errors. Mapping the floodplain using GIS is faster than mapping manually, and digital mapping is expected to be more common in the future. When mapping is done manually, the experience and judgment of the engineer or geographer completing the mapping and the contour resolution of the surface topography are critical in determining the flood-plain and floodway boundaries between cross sections. When mapping is done digitally, discrepancies can result from the use of the computing algorithm and digital topographic datasets. Understanding the possible sources of error and how the error accumulates through these processes is necessary for the validation of automated digital mapping. This study will evaluate the procedure of floodplain mapping using GIS and a 3 m by 3 m resolution DEM with a focus on the accumulated errors involved in the process. Within the GIS environment of this mapping method, the procedural steps of most interest, initially, include: (1) the accurate spatial representation of the stream centerline and cross sections, (2) properly using a triangulated irregular network (TIN) model for the flood elevations of the studied cross sections, the interpolated elevations between them and the extrapolated flood elevations beyond the cross sections, and (3) the comparison of the flood elevation TIN with the ground elevation DEM, from which the appropriate inundation boundaries are delineated. The study area involved is of relatively low topographic relief; thereby, making it representative of common suburban development and a prime setting for the need of accurately mapped floodplains. This paper emphasizes the impacts of integrating supplemental digital terrain data between cross sections on floodplain delineation. ?? 2007 ASCE.

Hydrogeomorphology influences soil nitrogen and phosphorus mineralization in floodplain wetlands

USGS Publications Warehouse

Noe, Gregory B.; Hupp, Cliff R.; Rybicki, Nancy B.

2013-01-01

Conceptual models of river–floodplain systems and biogeochemical theory predict that floodplain soil nitrogen (N) and phosphorus (P) mineralization should increase with hydrologic connectivity to the river and thus increase with distance downstream (longitudinal dimension) and in lower geomorphic units within the floodplain (lateral dimension). We measured rates of in situ soil net ammonification, nitrification, N, and P mineralization using monthly incubations of modified resin cores for a year in the forested floodplain wetlands of Difficult Run, a fifth order urban Piedmont river in Virginia, USA. Mineralization rates were then related to potentially controlling ecosystem attributes associated with hydrologic connectivity, soil characteristics, and vegetative inputs. Ammonification and P mineralization were greatest in the wet backswamps, nitrification was greatest in the dry levees, and net N mineralization was greatest in the intermediately wet toe-slopes. Nitrification also was greater in the headwater sites than downstream sites, whereas ammonification was greater in downstream sites. Annual net N mineralization increased with spatial gradients of greater ammonium loading to the soil surface associated with flooding, soil organic and nutrient content, and herbaceous nutrient inputs. Annual net P mineralization was associated negatively with soil pH and coarser soil texture, and positively with ammonium and phosphate loading to the soil surface associated with flooding. Within an intensively sampled low elevation flowpath at one site, sediment deposition during individual incubations stimulated mineralization of N and P. However, the amount of N and P mineralized in soil was substantially less than the amount deposited with sedimentation. In summary, greater inputs of nutrients and water and storage of soil nutrients along gradients of river–floodplain hydrologic connectivity increased floodplain soil nutrient mineralization rates.

Use of ALS data for digital terrain extraction and roughness parametrization in floodplain areas

NASA Astrophysics Data System (ADS)

Idda, B.; Nardinocchi, C.; Marsella, M.

2009-04-01

In order to undertake structural and land planning actions aimed at improving risk thresholds and vulnerability associated to floodplain inundation, the evaluation of the area concerning the channel overflowing from his natural embankments it is of essential importance. Floodplain models requires the analysis of historical floodplains extensions, ground's morphological structure and hydraulic measurements. Within this set of information, a more detailed characterization about the hydraulic roughness, which controls the velocity to the hydraulic flow, is a interesting challenge to achieve a 2D spatial distribution into the model. Remote sensing optical and radar sensors techniques can be applied to generate 2D and 3D map products useful to perimeter floodplains extension during the main event and extrapolate river cross-sections. Among these techniques, it is unquestionable the enhancement that the Airborne Laser Scanner (ALS) have brought for its capability to extract high resolution and accurate Digital Terrain Models. In hydraulic applications, a number of studies investigated the use of ALS for DTM generation and approached the quantitative estimations of the hydraulic roughness. The aim of this work is the generation of a digital terrain model and the estimation of hydraulic parameters useful for floodplains models from Airborne Laser Scanner data collected in a test area, which encloses a portion of a drainage basin of the Mela river (Sicily, Italy). From the Airborne Laser Scanner dataset, a high resolution Digital Elevation Model was first created, then after applying filtering and classification processes, a dedicated procedure was implemented to assess automatically a value for the hydraulic roughness coefficient (in Manning's formulation) per each point interested in the floodplain. The obtained results allowed to generate maps of equal roughness, hydraulic level depending, based on the application of empirical formulas for specific-type vegetation at each classified ALS point.

Struggle in the flood: tree responses to flooding stress in four tropical floodplain systems

PubMed Central

Parolin, Pia; Wittmann, Florian

2010-01-01

Background and aims In the context of the 200th anniversary of Charles Darwin's birth in 1809, this study discusses the variation in structure and adaptation associated with survival and reproductive success in the face of environmental stresses in the trees of tropical floodplains. Scope We provide a comparative review on the responses to flooding stress in the trees of freshwater wetlands in tropical environments. The four large wetlands we evaluate are: (i) Central Amazonian floodplains in South America, (ii) the Okavango Delta in Africa, (iii) the Mekong floodplains of Asia and (iv) the floodplains of Northern Australia. They each have a predictable ‘flood pulse’. Although flooding height varies between the ecosystems, the annual pulse is a major driving force influencing all living organisms and a source of stress for which specialized adaptations for survival are required. Main points The need for trees to survive an annual flood pulse has given rise to a large variety of adaptations. However, phenological responses to the flood are similar in the four ecosystems. Deciduous and evergreen species respond with leaf shedding, although sap flow remains active for most of the year. Growth depends on adequate carbohydrate supply. Physiological adaptations (anaerobic metabolism, starch accumulation) are also required. Conclusions Data concerning the ecophysiology and adaptations of trees in floodplain forests worldwide are extremely scarce. For successful floodplain conservation, more information is needed, ideally through a globally co-ordinated study using reproducible comparative methods. In the light of climatic change, with increasing drought, decreased groundwater availability and flooding periodicities, this knowledge is needed ever more urgently to facilitate fast and appropriate management responses to large-scale environmental change. PMID:22476061

The Two Edged Sword; Illinois' Risk Reduction Success Through Managed Retreat And Strong Regulations

NASA Astrophysics Data System (ADS)

Osman, P.

2017-12-01

Illinois has the nation's largest inland system of rivers, lakes, and streams. Two thirds of the continental US and two Canadian provinces drain thru Illinois. Although a blessing, these waterways also result in frequent flooding. Historically, Illinois ranked among the top five states in the nation for flood losses. However, using a combination of strong floodplain regulations and proactive flood mitigation programs, Illinois now ranks near the bottom of flood loss states. Following the 1993 flood, the State of Illinois began an aggressive program to remove flood prone structures from the floodplain. Using a combination of state, federal, and local funds, towns like Valmeyer and Grafton have largely been relocated outside of the floodplain. Likewise, in dozens of communities across the state, thousands of structures have been have purchased to create open space in the floodplain. In addition, new structures in the floodplain must meet strict state and local floodplain construction standards. Major floods now routinely pass Illinois unnoticed. Many communities once ravaged by flooding now pass large floods unscathed. Due largely to climate change, flood losses in many areas are evolving. The majority of flood losses in Illinois now occur outside of the mapped floodplain. The State of Illinois has recently completed a detailed analysis of the state's urban flood exposure. Flood risk is changing and methods to address that risk must evolve accordingly. Accurate climate change data on major inland waterways and urban areas remain elusive. This presentation will highlight simple steps any state or community can take to reduce existing flood losses and be better prepared to address changing impacts due to climate change.

Modeling multidecadal surface water inundation dynamics and key drivers on large river basin scale using multiple time series of Earth-observation and river flow data

NASA Astrophysics Data System (ADS)

Heimhuber, V.; Tulbure, M. G.; Broich, M.

2017-02-01

Periodically inundated floodplain areas are hot spots of biodiversity and provide a broad range of ecosystem services but have suffered alarming declines in recent history. Despite their importance, their long-term surface water (SW) dynamics and hydroclimatic drivers remain poorly quantified on continental scales. In this study, we used a 26 year time series of Landsat-derived SW maps in combination with river flow data from 68 gauges and spatial time series of rainfall, evapotranspiration and soil moisture to statistically model SW dynamics as a function of key drivers across Australia's Murray-Darling Basin (˜1 million km2). We fitted generalized additive models for 18,521 individual modeling units made up of 10 × 10 km grid cells, each split into floodplain, floodplain-lake, and nonfloodplain area. Average goodness of fit of models was high across floodplains and floodplain-lakes (r2 > 0.65), which were primarily driven by river flow, and was lower for nonfloodplain areas (r2 > 0.24), which were primarily driven by rainfall. Local climate conditions were more relevant for SW dynamics in the northern compared to the southern basin and had the highest influence in the least regulated and most extended floodplains. We further applied the models of two contrasting floodplain areas to predict SW extents of cloud-affected time steps in the Landsat series during the large 2010 floods with high validated accuracy (r2 > 0.97). Our framework is applicable to other complex river basins across the world and enables a more detailed quantification of large floods and drivers of SW dynamics compared to existing methods.

Provisioning of bioavailable carbon between the wet and dry phases in a semi-arid floodplain.

PubMed

Baldwin, Darren S; Rees, Gavin N; Wilson, Jessica S; Colloff, Matthew J; Whitworth, Kerry L; Pitman, Tara L; Wallace, Todd A

2013-06-01

Ecosystem functioning on arid and semi-arid floodplains may be described by two alternate traditional paradigms. The pulse-reserve model suggests that rainfall is the main driver of plant growth and subsequent carbon and energy reserve formation in the soil of arid and semi-arid regions. The flood pulse concept suggests that periodic flooding facilitates the two-way transfer of materials between a river and its adjacent floodplain, but focuses mainly on the period when the floodplain is inundated. We compared the effects of both rainfall and flooding on soil moisture and carbon in a semi-arid floodplain to determine the relative importance of each for soil moisture recharge and the generation of a bioavailable organic carbon reserve that can potentially be utilised during the dry phase. Flooding, not rainfall, made a substantial contribution to moisture in the soil profile. Furthermore, the growth of aquatic macrophytes during the wet phase produced at least an order of magnitude more organic material than rainfall-induced pulse-reserve responses during the dry phase, and remained as recognizable soil carbon for years following flood recession. These observations have led us to extend existing paradigms to encompass the reciprocal provisioning of carbon between the wet and dry phases on the floodplain, whereby, in addition to carbon fixed during the dry phase being important for driving biogeochemical transformations upon return of the next wet phase, aquatic macrophyte carbon fixed during the wet phase is recognized as an important source of energy for the dry phase. Reciprocal provisioning presents a conceptual framework on which to formulate questions about the resistance and ecosystem resilience of arid and semi-arid floodplains in the face of threats like climate change and alterations to flood regimes.

Floodplains as a source of fine sediment in grazed landscapes: tracing the source of suspended sediment in the headwaters of an intensively managed agricultural landscape

NASA Astrophysics Data System (ADS)

Yu, M.; Rhoads, B. L.; Stumpf, A.

2017-12-01

The flux of fine sediment within agricultural watersheds is an important factor determining the environmental quality of streams and rivers. Despite this importance, the contributions of sediment sources to suspended sediment loads within intensively managed agricultural watersheds remain poorly understood. This study assesses the provenance of fine suspended sediment in the headwater portion of a river flowing through an agricultural landscape in Illinois. Sediment source samples were collected from five potential sources: streambanks, forested floodplain, grassland, and grazed floodplains. Event-based and aggregated suspended sediment samples were collected from the stream at the watershed outlet. Quantitative geochemical fingerprinting techniques and a mixing model were employed to estimate the relative contributions of sediment from five potential sources to the suspended sediment loads. Organic matter content, trace elements, and fallout radionuclides were used as potential tracers. Principal Component analysis was employed to complement the results and Monte Carlo random sampling routine was used to test the uncertainty in estimated contributions of sources to in-stream sediment loads. Results indicate that the majority of suspended sediment is derived from streambanks and grazed floodplains. Erosion of the floodplain both by surface runoff and by streambank erosion from lateral channel migration contributes to the production of fine sediment within the stream system. These results suggest that human activities, in this case grazing, have converted portions of floodplains, normally net depositional environments, into sources of fine sediments. Efforts to reduce fluxes of fine sediment in this intensively managed landscape should focus on degraded floodplain surfaces and eroding channel banks within heavily grazed reaches of the stream.

Floodplain dynamics control the age distribution of organic carbon in large rivers

NASA Astrophysics Data System (ADS)

Torres, M. A.; Limaye, A. B. S.; Ganti, V.; West, A. J.; Fischer, W. W.; Lamb, M. P.

2016-12-01

As sediments transit through river systems, they are temporarily stored within floodplains. This storage is important for geochemical cycles because it imparts a certain cadence to weathering processes and organic carbon cycling. However, the time and length scales over which these processes operate are poorly known. To address this, we developed a model for the distribution of storage times in floodplains and used it to make predictions of the age distribution of riverine particulate organic carbon (POC) that can be compared with data from a range of rivers.Using statistics generated from a numerical model of river meandering that accounts for the rates of lateral channel migration and the lengths of channel needed to exchange the sediment flux with the floodplain, we estimated the distribution of sediment storage times. Importantly, this approach consistently yields a heavy-tailed distribution of storage times. This finding, based on comprehensive simulations of a wide range of river conditions, arises because of geometrical constraints that lead to the preferential erosion and reworking of young deposits. To benchmark our model, we compared our results with meteoric 10Be data (a storage time proxy) from Amazonian rivers. Our model correctly predicts observed 10Be concentrations, and consequently appears to capture the correct characteristic timescales associated with floodplain storage. By coupling a simple model of carbon cycling with our floodplain storage model, we are able to make predictions about the radiocarbon content of riverine POC. We observe that floodplains with greater storage times tend to have biospheric POC with a lower radiocarbon content (after correcting bulk ages for contribution from radiocarbon-dead petrogenic carbon). This result confirms that storage plays a key role in setting the age of POC transported by rivers with important implications for the dynamics of the global carbon cycle.

Spectrometric analyses in comparison to the physiological condition of heavy metal stressed floodplain vegetation in a standardised experiment

NASA Astrophysics Data System (ADS)

Götze, Christian; Jung, András; Merbach, Ines; Wennrich, Rainer; Gläßer, Cornelia

2010-06-01

Floodplain ecosystems are affected by flood dynamics, nutrient supply as well as anthropogenic activities. Heavy metal pollution poses a serious environmental challenge. Pollution transfer from the soil to vegetation is still present at the central location of Elbe River, Germany. The goal of this study was to assess and separate the current heavy metal contamination of the floodplain ecosystem, using spectrometric field and laboratory measurements. A standardized pot experiment with floodplain vegetation in differently contaminated soils provided the basis for the measurements. The dominant plant types of the floodplains are: Urtica dioica, Phalaris arundinacea and Alopecurus pratensis, these were also chemically analysed. Various vegetation indices and methods were used to estimate the red edge position, to normalise the spectral curve of the vegetation and to investigate the potential of different methods for separating plant stress in floodplain vegetation. The main task was to compare spectral bands during phenological phases to find a method to detect heavy metal stress in plants. A multi-level algorithm for the curve parameterisation was developed. Chemo-analytical and ecophysiological parameters of plants were considered in the results and correlated with spectral data. The results of this study show the influence of heavy metals on the spectral characteristics of the focal plants. The developed method (depth CR1730) showed significant relationship between the plants and the contamination.

Assessment of flood-induced changes of phytoplankton along a river-floodplain system using the morpho-functional approach.

PubMed

Mihaljević, Melita; Spoljarić, Dubravka; Stević, Filip; Zuna Pfeiffer, Tanja

2013-10-01

In this research, we aimed to find out how the differences in hydrological connectivity between the main river channel and adjacent floodplain influence the changes in phytoplankton community structure along a river-floodplain system. The research was performed in the River Danube floodplain (Croatian river section) in the period 2008-2009 characterised by different flooding pattern on an annual time scale. By utilising the morpho-functional approach and multivariate analyses, the flood-derived structural changes of phytoplankton were analysed. The lake stability during the isolation phase triggered the specific pattern of morpho-functional groups (MFG) which were characterised by cyanobacterial species achieving very high biomass. Adversely, the high water turbulence in the lake during the frequent and extreme flooding led to evident similarity between lake and river assemblages. Besides different diatom species (groups of small and large centrics and pennates), which are the most abundant representatives in the river phytoplankton, many other groups such as cryptophytes and colonial phytomonads appeared to indicate altered conditions in the floodplain driven by flooding. Having different functional properties, small centric diatom taxa sorted to only one MFG cannot clearly reflect environmental changes that are shown by the species-level pattern. Disadvantages in using the MFG approach highlight that it is still necessary to combine it with taxonomical approach in monitoring of phytoplankton in the river-floodplain ecosystems.

Floodplain farm fields provide novel rearing habitat for Chinook salmon

PubMed Central

Jeffres, Carson; Conrad, J. Louise; Sommer, Ted R.; Martinez, Joshua; Brumbaugh, Steve; Corline, Nicholas; Moyle, Peter B.

2017-01-01

When inundated by floodwaters, river floodplains provide critical habitat for many species of fish and wildlife, but many river valleys have been extensively leveed and floodplain wetlands drained for flood control and agriculture. In the Central Valley of California, USA, where less than 5% of floodplain wetland habitats remain, a critical conservation question is how can farmland occupying the historical floodplains be better managed to improve benefits for native fish and wildlife. In this study fields on the Sacramento River floodplain were intentionally flooded after the autumn rice harvest to determine if they could provide shallow-water rearing habitat for Sacramento River fall-run Chinook salmon (Oncorhynchus tshawytscha). Approximately 10,000 juvenile fish (ca. 48 mm, 1.1 g) were reared on two hectares for six weeks (Feb-March) between the fall harvest and spring planting. A subsample of the fish were uniquely tagged to allow tracking of individual growth rates (average 0.76 mm/day) which were among the highest recorded in fresh water in California. Zooplankton sampled from the water column of the fields were compared to fish stomach contents. The primary prey was zooplankton in the order Cladocera, commonly called water fleas. The compatibility, on the same farm fields, of summer crop production and native fish habitat during winter demonstrates that land management combining agriculture with conservation ecology may benefit recovery of native fish species, such as endangered Chinook salmon. PMID:28591141

Reoccupation of floodplains by rivers and its relation to the age structure of floodplain vegetation

USGS Publications Warehouse

Konrad, Christopher P.

2012-01-01

River channel dynamics over many decades provide a physical control on the age structure of floodplain vegetation as a river occupies and abandons locations. Floodplain reoccupation by a river, in particular, determines the interval of time during which vegetation can establish and mature. A general framework for analyzing floodplain reoccupation and a time series model are developed and applied to five alluvial rivers in the United States. Channel dynamics in these rivers demonstrate time-scale dependence with short-term oscillation in active channel area in response to floods and subsequent vegetation growth and progressive lateral movement that accounts for much of the cumulative area occupied by the rivers over decades. Rivers preferentially reoccupy locations recently abandoned causing a decreasing probability of reoccupation with time since abandonment. For a typical case, a river is 10 times more likely to reoccupy an area it abandoned in the past decade than it is to reoccupy an area it abandoned 30 yrs ago. The decreasing probability of reoccupation over time is consistent with observations of persistent stands of late seral stage floodplain forest. A power function provides a robust approach for estimating the cumulative area occupied by a river and the age structure of riparian forests resulting from a specific historical sequence of streamflow in comparison to either linear or exponential alternatives.

Flood inundation mapping in the Logone floodplain from multi temporal Landsat ETM+ imagery

NASA Astrophysics Data System (ADS)

Jung, H.; Alsdorf, D. E.; Moritz, M.; Lee, H.; Vassolo, S.

2011-12-01

Yearly flooding in the Logone floodplain makes an impact on agricultural, pastoral, and fishery systems in the Lake Chad Basin. Since the flooding extent and depth are highly variable, flood inundation mapping helps us make better use of water resources and prevent flood hazards in the Logone floodplain. The flood maps are generated from 33 multi temporal Landsat Enhanced Thematic Mapper Plus (ETM+) during three years 2006 to 2008. Flooded area is classified using a short-wave infrared band whereas open water is classified by Iterative Self-organizing Data Analysis (ISODATA) clustering. The maximum flooding extent in the study area increases up to ~5.8K km2 in late October 2008. The study also provides strong correlation of the flooding extents with water height variations in both the floodplain and the river based on a second polynomial regression model. The water heights are from ENIVSAT altimetry in the floodplain and gauge measurements in the river. Coefficients of determination between flooding extents and water height variations are greater than 0.91 with 4 to 36 days in phase lag. Floodwater drains back to the river and to the northeast during the recession period in December and January. The study supports understanding of the Logone floodplain dynamics in detail of spatial pattern and size of the flooding extent and assists the flood monitoring and prediction systems in the catchment.

Flood Inundation Mapping in the Logone Floodplain from Multi Temporal Landsat ETM+Imagery

NASA Technical Reports Server (NTRS)

Jung, Hahn Chul; Alsdorf, Douglas E.; Moritz, Mark; Lee, Hyongki; Vassolo, Sara

2011-01-01

Yearly flooding in the Logone floodplain makes an impact on agricultural, pastoral, and fishery systems in the Lake Chad Basin. Since the flooding extent and depth are highly variable, flood inundation mapping helps us make better use of water resources and prevent flood hazards in the Logone floodplain. The flood maps are generated from 33 multi temporal Landsat Enhanced Thematic Mapper Plus (ETM+) during three years 2006 to 2008. Flooded area is classified using a short-wave infrared band whereas open water is classified by Iterative Self-organizing Data Analysis (ISODATA) clustering. The maximum flooding extent in the study area increases up to approximately 5.8K km2 in late October 2008. The study also provides strong correlation of the flooding extents with water height variations in both the floodplain and the river based on a second polynomial regression model. The water heights are from ENIVSAT altimetry in the floodplain and gauge measurements in the river. Coefficients of determination between flooding extents and water height variations are greater than 0.91 with 4 to 36 days in phase lag. Floodwater drains back to the river and to the northeast during the recession period in December and January. The study supports understanding of the Logone floodplain dynamics in detail of spatial pattern and size of the flooding extent and assists the flood monitoring and prediction systems in the catchment.

Perirheic mixing and biogeochemical processing in flow-through and backwater floodplain wetlands

NASA Astrophysics Data System (ADS)

Jones, C. Nathan; Scott, Durelle T.; Edwards, Brandon L.; Keim, Richard F.

2014-09-01

Inundation hydrology and associated processes control biogeochemical processing in floodplains. To better understand how hydrologic connectivity, residence time, and intrafloodplain mixing vary in floodplain wetlands, we examined how water quality of two contrasting areas in the floodplain of the Atchafalaya River—a flow-through and a backwater wetland—responded to an annual flood pulse. Large, synoptic sampling campaigns occurred in both wetlands during the rising limb, peak, and falling limb of the hydrograph. Using a combination of conservative and reactive tracers, we inferred three dominant processes that occurred over the course of the flood pulse: flushing (rising limb), advective transport (peak), and organic matter accumulation (falling limb). Biogeochemistry of the two wetlands was similar during the peak while the river overflowed into both. However, during the rising and falling limbs, flow in the backwater wetland experienced much greater residence time. This led to the accumulation of dissolved organic matter and dissolved phosphorus. There were also elevated ratios of dissolved organic carbon to nitrate in the backwater wetland, suggesting nitrogen removal was limited by nitrate transported into the floodplain there. Collectively, our results suggest inclusion of a temporal component into the perirheic concept more fully describes inundation hydrology and biogeochemistry in large river floodplain. This article was corrected on 6 OCT 2014. See the end of the full text for details

24 CFR 55.24 - Aggregation.

Code of Federal Regulations, 2010 CFR

2010-04-01

... approval under this section is subject to compliance with the decision making process in § 55.20. ... FLOODPLAIN MANAGEMENT Procedures for Making Determinations on Floodplain Management § 55.24 Aggregation...

Can market-based policies accomplish the optimal floodplain management? A gap between static and dynamic models.

PubMed

Mori, Koichiro

2009-02-01

The purpose of this short article is to set static and dynamic models for optimal floodplain management and to compare policy implications from the models. River floodplains are important multiple resources in that they provide various ecosystem services. It is fundamentally significant to consider environmental externalities that accrue from ecosystem services of natural floodplains. There is an interesting gap between static and dynamic models about policy implications for floodplain management, although they are based on the same assumptions. Essentially, we can derive the same optimal conditions, which imply that the marginal benefits must equal the sum of the marginal costs and the social external costs related to ecosystem services. Thus, we have to internalise the external costs by market-based policies. In this respect, market-based policies seem to be effective in a static model. However, they are not sufficient in the context of a dynamic model because the optimal steady state turns out to be unstable. Based on a dynamic model, we need more coercive regulation policies.

10 CFR 1022.11 - Floodplain or wetland determination.

Code of Federal Regulations, 2010 CFR

2010-01-01

... within a base or critical action floodplain consistent with the most authoritative information available... consistent with the most authoritative information available relative to site conditions from the following...

Spatial relations between floodplain environments and land use - land cover of a large lowland tropical river valley: Pánuco basin, México.

PubMed

Hudson, Paul F; Colditz, René R; Aguilar-Robledo, Miguel

2006-09-01

Large lowland river valleys include a variety of floodplain environments that represent opportunities and constraints for human activities. This study integrates extensive field observations and geomorphic data with analysis of satellite remote sensing data to examine spatial relations between land use/land cover (LULC) and floodplain environments in the lower Pánuco basin of eastern Mexico. The floodplain of the lower Pánuco basin was delineated by combining a digital elevation model with a satellite image of a large flood event. The LULC was classified by combining a hybrid classification strategy with image stratification, applied to 15-m-resolution ASTER data. A geomorphic classification of floodplain environments was performed using a dry-stage image (ASTER data) and a 1993 Landsat image acquired during a large flood event. Accuracy assessment was based on aerial photographs (1:38,000), global positioning satellite ground-truthing, and a Landsat 7ETM(+) image from 2000, which resulted in an overall accuracy of 82.9% and a KHAT of 79.8% for the LULC classification. The geomorphic classification yielded 83.5% overall accuracy, whereas the KHAT was 81.5%. LULC analysis was performed for the entire floodplain and individually within four valley segments. The analysis indicates that the study area is primarily utilized for grazing and farming. Agriculture is primarily associated with coarse-grained (sandy/silty) natural levee and point bar units close to the river channel, whereas cattle grazing occurs in distal and lower-lying reaches dominated by cohesive fine-grained (clayey) deposits, such as backswamps. In the Pánuco valley, wetlands and lakes occur within backswamp environments, whereas in the Moctezuma segments, wetlands and lakes are associated with relict channels. This study reveals considerable variation in LULC related to spatial differences in floodplain environments and illustrates the importance of considering older anthropogenic influences on the landscape. The research design should be applicable for other large lowland coastal plain river valleys where agriculture is a major component of the floodplain landscape.

Spatial dynamics of overbank sedimentation in floodplain systems

USGS Publications Warehouse

Pierce, Aaron R.; King, S.L.

2008-01-01

Floodplains provide valuable social and ecological functions, and understanding the rates and patterns of overbank sedimentation is critical for river basin management and rehabilitation. Channelization of alluvial systems throughout the world has altered hydrological and sedimentation processes within floodplain ecosystems. In the loess belt region of the Lower Mississippi Alluvial Valley of the United States, channelization, the geology of the region, and past land-use practices have resulted in the formation of dozens of valley plugs in stream channels and the formation of shoals at the confluence of stream systems. Valley plugs completely block stream channels with sediment and debris and can result in greater deposition rates on floodplain surfaces. Presently, however, information is lacking on the rates and variability of overbank sedimentation associated with valley plugs and shoals. We quantified deposition rates and textures in floodplains along channelized streams that contained valley plugs and shoals, in addition to floodplains occurring along an unchannelized stream, to improve our understanding of overbank sedimentation associated with channelized streams. Feldspar clay marker horizons and marker poles were used to measure floodplain deposition from 2002 to 2005 and data were analyzed with geospatial statistics to determine the spatial dynamics of sedimentation within the floodplains. Mean sediment deposition rates ranged from 0.09 to 0.67??cm/y at unchannelized sites, 0.16 to 2.27??cm/y at shoal sites, and 3.44 to 6.20??cm/y at valley plug sites. Valley plug sites had greater rates of deposition, and the deposited sediments contained more coarse sand material than either shoal or unchannelized sites. A total of 59 of 183 valley plug study plots had mean deposition rates > 5??cm/y. The geospatial analyses showed that the spatial dynamics of sedimentation can be influenced by the formation of valley plugs and shoals on channelized streams; however, responses can vary. Restoration efforts in the region need to have basinwide collaboration with landowners and address catchment-scale processes, including the geomorphic instability of the region, to be successful. ?? 2008 Elsevier B.V. All rights reserved.

Floodplain and Wetland Assessment for the Mortandad Wetland Enhancement and the DP Dissipater Projects at Los Alamos National Laboratory

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

Hathcock, Charles Dean

This floodplain and wetland assessment was prepared in accordance with 10 Code of Federal Regulations (CFR) 1022 Compliance with Floodplain and Wetland Environmental Review Requirements, which was promulgated to implement the U.S. Department of Energy (DOE) requirements under Executive Order 11988 Floodplain Management and Executive Order 11990 Wetlands Protection. According to 10 CFR 1022, a 100-year floodplain is defined as “the lowlands adjoining inland and coastal waters and relatively flat areas and flood prone areas of offshore islands” and a wetland is defined as “an area that is inundated or saturated by surface or groundwater at a frequency and durationmore » sufficient to support, and that under normal circumstances does support, a prevalence of vegetation typically adapted for life in saturated soil conditions, including swamps, marshes, bogs, and similar areas.” In this action, DOE is proposing two projects to improve wetland and floodplain function at Los Alamos National Laboratory (LANL). The proposed work will comply with corrective action requirements under the Settlement Agreement and Stipulated Final Compliance Order (Settlement Agreement)1 Number HWB-14-20. The first project is located in Technical Areas (TA)-03 in upper Mortandad Canyon. The upper Mortandad wetlands have existing stormwater controls that need to be rehabilitated. Head-cut formation is occurring at the downstream portion of the wetland. This project will repair damages to the wetland and reduce the future erosion potential. The second project is located in TA-21 in Delta Prime (DP) Canyon. The intent of the DP Dissipater Project in DP Canyon is to install stormwater control structures in DP Canyon to retain low channel flows and reduce downstream sediment transport as well as peak flows during low and moderate storm events. Due to increased erosion, the stream bank in this area has unstable vertical walls within the stream channel. The DOE prepared this floodplain and wetland assessment to evaluate the potential impacts of implementing the proposed actions within the wetland and floodplain, as required by 10 CFR 1022.« less

Soil Biogeochemical and Microbial Feedbacks along a Snowmelt-Dominated Hillslope-to-Floodplain Transect in Colorado.

NASA Astrophysics Data System (ADS)

Sorensen, P.; Beller, H. R.; Bill, M.; Bouskill, N.; Brodie, E.; Chakraborty, R.; Conrad, M. E.; Karaoz, U.; Polussa, A.; Steltzer, H.; Wang, S.; Williams, K. H.; Wilmer, C.; Wu, Y.

2017-12-01

Nitrogen export from mountainous watersheds is a product of multiple interactions among hydrological processes and soil-microbial-plant feedbacks along the continuum from terrestrial to aquatic environments. In snow-dominated systems, like the East River Watershed (CO), seasonal processes such as snowmelt exert significant influence on the annual hydrologic cycle and may also link spatially distinct catchment subsystems, such as hillslope and adjoining riparian floodplains. Further, snowmelt is occurring earlier each year and this is predicted to result in a temporal asynchrony between historically coupled microbial nutrient release and plant nutrient demand in spring, with the potential to increase N export from the East River Watershed. Here we summarize biogeochemical data collected along a hillslope-to-riparian floodplain transect at the East River site. Starting in Fall 2016, we sampled soils at 3 depths and measured dissolved pools of soil nutrients (e.g., NH4+, NO3-, DOC, P), microbial biomass CN, and microbial community composition over a seasonal time course, through periods of snow accumulation, snowmelt, and plant senescence. Soil moisture content in the top 5 cm of floodplain soils was nearly 4X greater across sampling dates, coinciding with 2X greater microbial biomass C, larger extractable pools of NH4+, and smaller pools of NO3- in floodplain vs. hillslope soils. These results suggest that microbially mediated redox processes played an important role in N cycling along the transect. Hillslope vs. floodplain location also appeared to be a key factor that differentiated soil microbial communities (e.g., a more important factor than seasonality or soil depth or type). Snow accumulation and snowmelt exerted substantial influence on soil biogeochemistry. For example, microbial biomass accumulation increased about 2X beneath the winter snowpack. Snowmelt resulted in a precipitous crash in the microbial population, with 2.5X reductions in floodplain and 2X reductions in hillslope soils. Immediately following snowmelt, NO3- concentrations in soil porewater and soil extracts increased dramatically. Overall, these results suggest that N export is strongly influenced by distinct soil biogeochemical and microbiological patterns along hillslope-to-floodplain transects at East River.

Methane emissions from floodplains in the Amazon Basin: challenges in developing a process-based model for global applications

NASA Astrophysics Data System (ADS)

Ringeval, B.; Houweling, S.; van Bodegom, P. M.; Spahni, R.; van Beek, R.; Joos, F.; Röckmann, T.

2014-03-01

Tropical wetlands are estimated to represent about 50% of the natural wetland methane (CH4) emissions and explain a large fraction of the observed CH4 variability on timescales ranging from glacial-interglacial cycles to the currently observed year-to-year variability. Despite their importance, however, tropical wetlands are poorly represented in global models aiming to predict global CH4 emissions. This publication documents a first step in the development of a process-based model of CH4 emissions from tropical floodplains for global applications. For this purpose, the LPX-Bern Dynamic Global Vegetation Model (LPX hereafter) was slightly modified to represent floodplain hydrology, vegetation and associated CH4 emissions. The extent of tropical floodplains was prescribed using output from the spatially explicit hydrology model PCR-GLOBWB. We introduced new plant functional types (PFTs) that explicitly represent floodplain vegetation. The PFT parameterizations were evaluated against available remote-sensing data sets (GLC2000 land cover and MODIS Net Primary Productivity). Simulated CH4 flux densities were evaluated against field observations and regional flux inventories. Simulated CH4 emissions at Amazon Basin scale were compared to model simulations performed in the WETCHIMP intercomparison project. We found that LPX reproduces the average magnitude of observed net CH4 flux densities for the Amazon Basin. However, the model does not reproduce the variability between sites or between years within a site. Unfortunately, site information is too limited to attest or disprove some model features. At the Amazon Basin scale, our results underline the large uncertainty in the magnitude of wetland CH4 emissions. Sensitivity analyses gave insights into the main drivers of floodplain CH4 emission and their associated uncertainties. In particular, uncertainties in floodplain extent (i.e., difference between GLC2000 and PCR-GLOBWB output) modulate the simulated emissions by a factor of about 2. Our best estimates, using PCR-GLOBWB in combination with GLC2000, lead to simulated Amazon-integrated emissions of 44.4 ± 4.8 Tg yr-1. Additionally, the LPX emissions are highly sensitive to vegetation distribution. Two simulations with the same mean PFT cover, but different spatial distributions of grasslands within the basin, modulated emissions by about 20%. Correcting the LPX-simulated NPP using MODIS reduces the Amazon emissions by 11.3%. Finally, due to an intrinsic limitation of LPX to account for seasonality in floodplain extent, the model failed to reproduce the full dynamics in CH4 emissions but we proposed solutions to this issue. The interannual variability (IAV) of the emissions increases by 90% if the IAV in floodplain extent is accounted for, but still remains lower than in most of the WETCHIMP models. While our model includes more mechanisms specific to tropical floodplains, we were unable to reduce the uncertainty in the magnitude of wetland CH4 emissions of the Amazon Basin. Our results helped identify and prioritize directions towards more accurate estimates of tropical CH4 emissions, and they stress the need for more research to constrain floodplain CH4 emissions and their temporal variability, even before including other fundamental mechanisms such as floating macrophytes or lateral water fluxes.

Numerical simulation of streamflow distribution, sediment transport, and sediment deposition along Long Beach Creek in Northeast Missouri

USGS Publications Warehouse

Heimann, David C.

2001-01-01

This report presents the results of a study conducted by the U.S. Geological Survey in cooperation with the Missouri Department of Conservation to describe the hydrology, sediment transport, and sediment deposition along a selected reach of Long Branch Creek in Macon County, Missouri. The study was designed to investigate spatial and temporal characteristics of sediment deposition in a remnant forested riparian area and compare these factors by magnitude of discharge events both within and outside the measured range of flood magnitudes. The two-dimensional finite-element numerical models RMA2-WES and SED2D-WES were used in conjunction with measured data to simulate streamflow and sediment transport/deposition characteristics during 2-, 5-, 10-, and 25-year recurrence interval floods. Spatial analysis of simulated sediment deposition results indicated that mean deposition in oxbows and secondary channels exceeded that of the remaining floodplain areas during the 2-, 5-, 10-, and 25-year recurrence interval floods. The simulatedmass deposition per area for oxbows and secondary channels was 1.1 to 1.4 centimeters per square meter compared with 0.1 to 0.60 centimeters per square meter for the remaining floodplain. The temporal variability of total incremental floodplain deposition during a flood was found to be strongly tied to sediment inflowconcentrations. Most floodplain deposition, therefore, occurred at the beginning of the streamflow events and corresponded to peaks in sediment discharge. Simulated total sediment deposition in oxbows and secondary channels increased in the 2-year through 10-year floods and decreased in the 25- year flood while remaining floodplain deposition was highest for the 25-year flood. Despite increases in sediment inflows from the 2-year through 25-year floods, the retention ratio of sediments (the ratio of floodplain deposition to inflow load) was greatest for the 5-year flood and least for the 25-year flood. The decrease in retention ratio at greater flows is likely the result of higher velocities on the floodplain, resulting in higher bed shear stress, greater suspension time of deposited material, and greater sediment transport through the system. Simulated sediment deposition was most sensitive to sediment inflow concentrations and modification of floodplain roughness?factors that can be controlled through management practices. The increase in floodplain sediment deposition resulting from a simulated increase in vegetation density (increase in floodplain roughness from a Manning?s n of 0.11 to 0.12) was 142,000 kilograms, or 6.5 percent for a 10-year recurrence interval flood. This increase was comparable to total oxbow and secondary channel depositionmass in the simulations, but would result in amean increase in floodplain deposition thickness of only 0.025 centimeter. The hydrodynamic model results show the importance of the secondary channels and meander cutoff channels in this system because these areas quickly bring floodwaters and sediment to areas not close to the main channel. The meander cutoff channels in the simulation also effectively decrease flow and velocities in somemain channel sections thereby affecting sediment deposition in the vicinity of these features.

24 CFR 55.21 - Notification of floodplain hazard.

Code of Federal Regulations, 2010 CFR

2010-04-01

... § 55.21 Notification of floodplain hazard. For HUD programs under which a financial transaction for a..., regulated or insured, any private party participating in the transaction and any current or prospective...

Modern Pearl River Delta and Permian Huainan coalfield, China: A comparative sedimentary facies study

USGS Publications Warehouse

Suping, P.; Flores, R.M.

1996-01-01

Sedimentary facies types of the Pleistocene deposits of the Modern Pearl River Delta in Guangdong Province, China and Permian Member D deposits in Huainan coalfield in Anhui Province are exemplified by depositional facies of anastomosing fluvial systems. In both study areas, sand/sandstone and mud/mudstone-dominated facies types formed in diverging and converging, coeval fluvial channels laterally juxtaposed with floodplains containing ponds, lakes, and topogenous mires. The mires accumulated thin to thick peat/coal deposits that vary in vertical and lateral distribution between the two study areas. This difference is probably due to attendant sedimentary processes that affected the floodplain environments. The ancestral floodplains of the Modern Pearl River Delta were reworked by combined fluvial and tidal and estuarine processes. In contrast, the floodplains of the Permian Member D were mainly influenced by freshwater fluvial processes. In addition, the thick, laterally extensive coal zones of the Permian Member D may have formed in topogenous mires that developed on abandoned courses of anastomosing fluvial systems. This is typified by Seam 13-1, which is a blanket-like body that thickens to as much as 8 in but also splits into thinner beds. This seam overlies deposits of diverging and converging, coeval fluvial channels of the Sandstone D, and associated overbank-floodplain deposits. The limited areal extent of lenticular Pleistocene peat deposits of the Modern Pearl River Delta is due to their primary accumulation in topogenous mires in the central floodplains that were restricted by contemporaneous anastomosing channels.

Hot Spots and Hot Moments of Nitrogen in a Riparian Corridor

NASA Astrophysics Data System (ADS)

Dwivedi, Dipankar; Arora, Bhavna; Steefel, Carl I.; Dafflon, Baptiste; Versteeg, Roelof

2018-01-01

We use 3-D high-resolution reactive transport modeling to investigate whether the spatial distribution of organic-carbon-rich and chemically reduced sediments located in the riparian zone and temporal variability in groundwater flow direction impact the formation and distribution of nitrogen hot spots (regions that exhibit higher reaction rates when compared to other locations nearby) and hot moments (times that exhibit high reaction rates as compared to longer intervening time periods) within the Rifle floodplain in Colorado. Groundwater flows primarily toward the Colorado River from the floodplain but changes direction at times of high river stage. The result is that oxic river water infiltrates the Rifle floodplain during these relatively short-term events. Simulation results indicate that episodic rainfall in the summer season leads to the formation of nitrogen hot moments associated with Colorado River rise and resulting river infiltration into the floodplain. The results further demonstrate that the naturally reduced zones (NRZs) present in sediments of the Rifle floodplain have a higher potential for nitrate removal, approximately 70% greater than non-NRZs for typical hydrological conditions. During river water infiltration, nitrate reduction capacity remains the same within the NRZs, however, these conditions impact non-NRZs to a greater extent (approximately 95% less nitrate removal). Model simulations indicate chemolithoautotrophs are primarily responsible for the removal of nitrate in the Rifle floodplain. These nitrogen hot spots and hot moments are sustained by microbial respiration and the chemolithoautotrophic oxidation of reduced minerals in the riparian zone.

Dynamics of Murray-Darling floodplain forests under multiple stressors: The past, present, and future of an Australian icon

NASA Astrophysics Data System (ADS)

Mac Nally, Ralph; Cunningham, Shaun C.; Baker, Patrick J.; Horner, Gillis J.; Thomson, James R.

2011-12-01

We review the human actions, proximal stressors and ecological responses for floodplain forests Australia's largest river system—the Murray-Darling Basin. A conceptual model for the floodplain forests was built from extensive published information and some unpublished results for the system, which should provide a basis for understanding, studying and managing the ecology of floodplains that face similar environmental stresses. Since European settlement, lowlands areas of the basin have been extensively cleared for agriculture and remnant forests heavily harvested for timber. The most significant human intervention is modification of river flows, and the reduction in frequency, duration and timing of flooding, which are compounded by climate change (higher temperatures and reduced rainfall) and deteriorating groundwater conditions (depth and salinity). This has created unfavorable conditions for all life-history stages of the dominant floodplain tree (Eucalyptus camaldulensis Dehnh.). Lack of extensive flooding has led to widespread dieback across the Murray River floodplain (currently 79% by area). Management for timber resources has altered the structure of these forests from one dominated by large, widely spreading trees to mixed-aged stands of smaller pole trees. Reductions in numbers of birds and other vertebrates followed the decline in habitat quality (hollow-bearing trees, fallen timber). Restoration of these forests is dependent on substantial increases in the frequency and extent of flooding, improvements in groundwater conditions, re-establishing a diversity of forest structures, removal of grazing and consideration of these interacting stressors.

Effects of flood inundation and invasion by Phalaris arundinacea on nitrogen cycling in an Upper Mississippi River floodplain forest

USGS Publications Warehouse

Swanson, Whitney; DeJager, Nathan R.; Strauss, Eric A.; Thomsen, Meredith

2017-01-01

Although floodplains are thought to serve as important buffers against nitrogen (N) transport to aquatic systems, frequent flooding and high levels of nutrient availability also make these systems prone to invasion by exotic plant species. Invasive plants could modify the cycling and availability of nutrients within floodplains, with effects that could feedback to promote the persistence of the invasive species and impact N export to riverine and coastal areas. We examined the effect of flooding on soil properties and N cycling at a floodplain site in Pool 8 of the Upper Mississippi River with 2 plant communities: mature native forest (Acer saccharinum) and patches of an invasive grass (Phalaris arundinacea). Plots were established within each vegetation type along an elevation gradient and sampled throughout the summers of 2013 and 2014. Spatial trends in flooding resulted in higher soil organic matter, porosity, and total nitrogen and carbon in low elevations. Nutrient processes and NH4+ and NO3− availability, however, were best explained by vegetation type and time after flooding. Phalaris plots maintained higher rates of nitrification and higher concentrations of available NH4+ and NO3−. These results suggest that invasion by Phalarismay make nitrogen more readily available and could help to reinforce this species' persistence in floodplain wetlands. They also raise the possibility that Phalaris may decrease floodplain N storage capacity and influence downstream transport of N to coastal zones.

The Rhine Delta - a record of sediment trapping over time scales from millennia to decades

NASA Astrophysics Data System (ADS)

Middelkoop, Hans; Erkens, Gilles; van der Perk, Marcel

2010-05-01

At the land-ocean interface, large river deltas are major sinks of sediments and associated matter. Over the past decennia, many studies have been conducted on the palaeogeographic, historic and sub-recent overbank deposition on the Rhine floodplains. In this study these research results are synthesises with special focus on the amounts and changes of overbank fines trapped in the Rhine delta at different time scales in the past, present, and future. This contribution forms an update of the results presented at the EGU 2009 in session HS11.3 (Sediment response to catchment disturbances). Sediment trapping in the Rhine delta throughout the Holocene was quantified using a detailed database of the Holocene delta architecture. Additional historic data allowed the reconstruction of the development of the river floodplains during the period of direct human interference on the river. Using heavy metals as tracers, overbank deposition rates over the past century were determined. Measurements of overbank deposition and channel bed sediment transport in recent years, together with modelling studies of sediment transport and deposition have provided detailed insight in the present-day sediment deposition on the floodplains, as well as their controls. Estimated annual suspended sediment delivery rates were about 1.4 Mton (million tons) yr-1 between 6000-3000 yr BP and increased to about 2.1 Mton yr-1 between 3000-1000 yr BP. After embankment between 1100 and 1350 AD the amount of sediment trapped in the floodplains reduced to about 0.92 Mton yr-1. However, when accounting for sediment reworking, the actual sediment trapping of the embanked floodplains was about 1.6 Mton yr-1. Downstream of the lower Waal branch an inland delta developed that trapped another 0.4 Mton yr-1 of overbank fines. Since channel normalisation around 1850, the average deposition amounts on the embanked floodplains have been 1.15 Mton yr-1. Scenario studies show that the future sediment trapping in the lower Rhine floodplains might double. The variations in sediment deposited in the Rhine delta during the Holocene are largely attributed to changes in land use in the upstream basin. At present, the sediment trapping is low and heavily influenced by river regulation and engineering works. Upstream changes in climate and land use, and particularly direct measures for flood reduction in the lower floodplains may again change the amounts of sediments trapped by the lower floodplains in the forthcoming decennia.

Hydrological responses to channelization and the formation of valley plugs and shoals

USGS Publications Warehouse

Pierce, Aaron R.; King, Sammy L.

2017-01-01

Rehabilitation of floodplain systems focuses on restoring interactions between the fluvial system and floodplain, however, there is a paucity of information on the effects of valley plugs and shoals on floodplain hydrological processes. We investigated hydrologic regimes in floodplains at three valley plug sites, two shoal sites, and three unchannelized sites. Valley plug sites had altered surface and sub-surface hydrology relative to unchannelized sites, while only sub-surface hydrology was affected at shoal sites. Some of the changes were unexpected, such as reduced flood duration and flood depth in floodplains associated with valley plugs. Our results emphasize the variability associated with hydrologic processes around valley plugs and our rudimentary understanding of the effects associated with these geomorphic features. Water table levels were lower at valley plug sites compared to unchannelized sites, however, valley plug sites had a greater proportion of days when water table inundation was above mean root collar depth than both shoal and unchannelized sites as a result of lower root collar depths and higher deposition rates. This study has provided evidence that valley plugs can affect both surface and sub-surface hydrology in different ways than previously thought and illustrates the variability in hydrological responses to valley plug formation.

Floodplains as an Achilles’ heel of Amazonian forest resilience

PubMed Central

Flores, Bernardo M.; Holmgren, Milena; van Nes, Egbert H.; Jakovac, Catarina C.; Mesquita, Rita C. G.; Scheffer, Marten

2017-01-01

The massive forests of central Amazonia are often considered relatively resilient against climatic variation, but this view is challenged by the wildfires invoked by recent droughts. The impact of such fires that spread from pervasive sources of ignition may reveal where forests are less likely to persist in a drier future. Here we combine field observations with remotely sensed information for the whole Amazon to show that the annually inundated lowland forests that run through the heart of the system may be trapped relatively easily into a fire-dominated savanna state. This lower forest resilience on floodplains is suggested by patterns of tree cover distribution across the basin, and supported by our field and remote sensing studies showing that floodplain fires have a stronger and longer-lasting impact on forest structure as well as soil fertility. Although floodplains cover only 14% of the Amazon basin, their fires can have substantial cascading effects because forests and peatlands may release large amounts of carbon, and wildfires can spread to adjacent uplands. Floodplains are thus an Achilles’ heel of the Amazon system when it comes to the risk of large-scale climate-driven transitions. PMID:28396440

Modification of suburban carbon and nitrogen fluxes by a coupled channel/floodplain system assessed using in situ sensors

NASA Astrophysics Data System (ADS)

Wollheim, W. M.; Pellerin, B. A.; Saraceno, J.; Hopkinson, C.; Hope, A.; Morse, N.

2010-12-01

Biogeochemical fluxes in human dominated streams and rivers are highly impacted, but effects can be attenuated downstream through natural ecosystem processes. We deployed in situ nitrate, fdom, and chlorophyll sensors to characterize biogeochemical fluxes draining a suburban catchment, and modifications by a channel-floodplain system located immediately downstream. The upstream site reflects the suburban signal; the downstream site reflects the influence of the channel/floodplain on the suburban signal. FDOM showed a diurnal signal at both sites, but was stronger downstream, likely indicating new DOC production within the channel-floodplain system, which contained a small pond. In situ chlorophyll concentrations were also highly correlated with FDOM. FDOM showed a stronger storm response upstream than downstream, indicating terrestrial sources are mobilized by storms and subsequent dampening of the pulse by the floodplain. Nitrate concentrations consistently dropped from 0.6 to 0.7 mg/l upstream to less than 0.4 mg/l downstream, indicating likely nitrogen retention or removal over a relatively short distance (~500m). Use of in situ sensors is likely to greatly advance our understanding of biogeochemical processes in aquatic systems.

Living with floods in the Jamuna floodplain (Bangladesh): fight or flight? Technological and societal responses

NASA Astrophysics Data System (ADS)

Ruknul Ferdous, Md; Wesselink, Anna; Brandimarte, Luigia; Slager, Kymo; Mynett, Arthur; Zwarteveen, Margreet

2017-04-01

Building onto the general theory introduced by Di Baldassarre, this paper uses a socio-hydrological approach to describe human-flood interactions in the Jamuna floodplain, Bangladesh. In this vast space (a braided river bed of 6-16 km; floodplains up to 50 km wide) the differences between land and water are temporary and shifting. Government flood defence structures were constructed on the west bank only, while community initiatives exist on the east bank. As a result, there are several kinds of socio-hydrological spaces along, but also in the river, with different livelihoods and flood characteristics. This variety gives rise to co-existence of 'living with floods' and 'fighting floods' approaches. The analysis is based on recent fieldwork, in which information on historical and current livelihoods, migration and the floodplain system was collected at household level. Our analysis enables us to tentatively confirm the levee effect described by Di Baldassarre et al. (2013); however, his hypothesis that people move away from unprotected floodplains is only true to some extent. Adaptation in Bangladesh means first of all literally 'living with floods': being flooded with greater or lesser frequency. Key words: Bangladesh; Jamuna River; river flooding; socio-hydrological dynamics

A comparison of small-mammal communities in a desert riparian floodplain

USGS Publications Warehouse

Ellison, Laura E.; van Riper, Charles

1998-01-01

We compared small-mammal communities between inactive floodplain and actively flooded terraces of riparian habitat in the Verde Valley of central Arizona. We used species diversity, abundance, weight of adult males, number of juveniles, number of reproductively active individuals, longevity, residency status, and patterns of microhabitat use to compare the two communities. Although abundances of small mammals tended to be higher in the active floodplain, species diversity was greater in the inactive floodplain. Results were inconsistent with our initial prediction that actively flooded riparian habitat acts as a species source, whereas inactive floodplain acts as a sink or dispersal site for small mammals. Within each habitat type, we found evidence of significant microhabitat separation among the three most abundant small-mammal species (Peromyscus boylii, P. eremicus, and Neotoma albigula). Percent cover by annual and perennial grasses and shrubs, substrate, and frequency of shrubs, trees, and debris were significant determinants of small-mammal distribution within a habitat type. We found that the three most abundant species selected a nonrandom subset of available habitat. Nonrandom use of habitat and microhabitat separation were the two most important mechanisms structuring small-mammal communities in riparian habitat of central Arizona.

Results From a Channel Restoration Project: Hydraulic Design Considerations

USGS Publications Warehouse

Karle, K.F.; Densmore, R.V.; ,

2001-01-01

Techniques for the hydraulic restoration of placer-mined streams and floodplains were developed in Denali National Park and Preserve, Alaska. The two-year study at Glen Creek focused on a design of stream and floodplain geometry using hydraulic capacity and shear stress equations. Slope and sinuosity values were based on regional relationships. Design requirements included a channel capacity for a bankfull discharge and a floodplain capacity for a 1.5- to 100-year discharge. Several bio-engineering techniques using alder and willow, including anchored brush bars, streambank hedge layering, seedlings, and cuttings, were tested to dissipate floodwater energy and encourage sediment deposition until natural revegetation stabilized the new floodplains. Permanently monumented cross-sections installed throughout the project site were surveyed every one to three years. Nine years after the project began, a summer flood caused substantial damage to the channel form, including a change in width/depth ratio, slope, and thalweg location. Many of the alder brush bars were heavily damaged or destroyed, resulting in significant bank erosion. This paper reviews the original hydraulic design process, and describes changes to the channel and floodplain geometry over time, based on nine years of cross-section surveys.

[The role of the floodplain gradient in structuring of testate amoebae communities in the Ilych River].

PubMed

Mazeĭ, Iu A; Malysheva, E A; Lapteva, E M; Komarov, A A; Taskaeva, A A

2012-01-01

Forty-two testate amoebae taxa were identified in alluvial soils of floodplain islands in the Ilych River. Among the pedo- and eurybionts, there were aquatic rhizopods. Along the floodplain transect (willow --> meadow --> deciduous forest --> coniferous forest), the testate amoebae community changed directly. There are spatially homogeneous (low beta-diversity) testacean communities but species rich on the local level (high alpha-diversity) within forests. Within willows and meadows, communities are characterized by low alpha-diversity and high heterogeneity that leads to high gamma-diversity.

Methane emissions from floodplains in the Amazon Basin: towards a process-based model for global applications

NASA Astrophysics Data System (ADS)

Ringeval, B.; Houweling, S.; van Bodegom, P. M.; Spahni, R.; van Beek, R.; Joos, F.; Röckmann, T.

2013-10-01

Tropical wetlands are estimated to represent about 50% of the natural wetland emissions and explain a large fraction of the observed CH4 variability on time scales ranging from glacial-interglacial cycles to the currently observed year-to-year variability. Despite their importance, however, tropical wetlands are poorly represented in global models aiming to predict global CH4 emissions. This study documents the first regional-scale, process-based model of CH4 emissions from tropical floodplains. The LPX-Bern Dynamic Global Vegetation Model (LPX hereafter) was modified to represent floodplain hydrology, vegetation and associated CH4 emissions. The extent of tropical floodplains was prescribed using output from the spatially-explicit hydrology model PCR-GLOBWB. We introduced new Plant Functional Types (PFTs) that explicitly represent floodplain vegetation. The PFT parameterizations were evaluated against available remote sensing datasets (GLC2000 land cover and MODIS Net Primary Productivity). Simulated CH4 flux densities were evaluated against field observations and regional flux inventories. Simulated CH4 emissions at Amazon Basin scale were compared to model simulations performed in the WETCHIMP intercomparison project. We found that LPX simulated CH4 flux densities are in reasonable agreement with observations at the field scale but with a~tendency to overestimate the flux observed at specific sites. In addition, the model did not reproduce between-site variations or between-year variations within a site. Unfortunately, site informations are too limited to attest or disprove some model features. At the Amazon Basin scale, our results underline the large uncertainty in the magnitude of wetland CH4 emissions. In particular, uncertainties in floodplain extent (i.e., difference between GLC2000 and PCR-GLOBWB output) modulate the simulated emissions by a factor of about 2. Our best estimates, using PCR-GLOBWB in combination with GLC2000, lead to simulated Amazon-integrated emissions of 44.4 ± 4.8 Tg yr-1. Additionally, the LPX emissions are highly sensitive to vegetation distribution. Two simulations with the same mean PFT cover, but different spatial distributions of grasslands within the basin modulated emissions by about 20%. Correcting the LPX simulated NPP using MODIS reduces the Amazon emissions by 11.3%. Finally, due to an intrinsic limitation of LPX to account for seasonality in floodplain extent, the model failed to reproduce the seasonality in CH4 emissions. The Inter Annual Variability (IAV) of the emissions increases by 90% if the IAV in floodplain extent is account for, but still remains lower than in most of WETCHIMP models. While our model includes more mechanisms specific to tropical floodplains, we were unable to reduce the uncertainty in the magnitude of wetland CH4 emissions of the Amazon Basin. Our results stress the need for more research to constrain floodplain CH4 emissions and their temporal variability.

Assessing floodplain restoration success using soil morphology indicators

NASA Astrophysics Data System (ADS)

Guenat, Claire; Fournier, Bertrand; Bullinger-Weber, Géraldine; Grin, Karin; Pfund, Simona; Mitchell, Edward

2010-05-01

Floodplains are complex ecological systems that fulfil different ecological, economic and social functions related to physical, chemical, and biological processes. The fluvial dynamics of most rivers in industrialized countries have been altered to such an extent that floodplains are now one of the most threatened ecosystems worldwide. This adverse impact has been widely recognized and, nowadays, extensive attempts are underway to return rivers to more natural conditions and restore their ecological quality and essential ecosystem functions. As a consequence, the number of restoration projects worldwide is rapidly increasing. However, despite an estimated global cost of more than 1 billion dollars annually, there is a crucial lack of monitoring and quantitative evaluations. Indeed, most projects are never monitored post-restoration (NRC 1992). In Switzerland, only 35% of the projects include a monitoring program mainly based on flora and fauna (BAFU). The design, selection and optimization of indicators for project monitoring are of major importance for sustainable management of riverine ecosystems. However, despite the growing body of literature on potential indicators and criteria for assessing the success of restoration projects no standardised or generally applicable method exists. Furthermore, soils are rarely considered among the possible indicators despite their crucial roles in ecosystems such as decomposition, supplying resources (habitats, gene pool, biomass, and raw materials), and environmental interactions (storage, filtering, transformation). We therefore hypothesized that soils may constitute an appropriate synthetic and functional indicator for the evaluation of river restoration success, especially in the framework of river widening aiming to increase the terrestrial biodiversity. In agreement with the current concepts of river restoration, we propose an assessment tool for floodplain restoration based on three soil morphology criteria (soil diversity, soil typicality, and soil dynamism) and their associated indicators (for example soil Shannon indexes, frequency of soils with specific characteristics, elevation variations due to the fluvial dynamic). The success of floodplain restoration is assessed through comparisons of these criteria between the restored river sector and a reference that could be a near natural floodplain or an embanked floodplain. As a test case, we used a near natural floodplain along the Rhine River as reference site. We then assessed the performance of the method by assessing how well the selected indicators explained a data set of soil physico-chemical characteristics in a principal component analysis. We applied this pedological tool to assess the efficiency of two rivers widening: the Thur (River Thur, CCES project RECORD: http://www.swiss-experiment.ch/index.php/Record:Home), and the Emme River restorations (http://www.bve.be.ch/site/bve_tba_dok_down_wasserbau_emme.pdf). In agreement with other studies, our results confirmed that these restoration projects were partial success. This study demonstrated that soil morphology presents multiple advantages as an indicator of floodplain restoration: ease of use, spatial delimitation of the floodplain, information on past events and fluvial dynamic, and different spatial levels of observation (topsoil horizons, deep horizons, and complete soil profiles).

Sprague River geomorphology studies, Klamath Basin, Oregon

NASA Astrophysics Data System (ADS)

McDowell, P. F.; O'Connor, J. E.; Lind, P.

2005-12-01

The Sprague River drains 4050 square kilometers with a mean annual discharge of 16.3 m3/s before emptying into the Williamson River and then upper Klamath Lake in southcentral Oregon. The alternating wide alluvial segments and narrow canyon reaches of this 135-km-long westward flowing river provide for a variety of valued ecologic conditions and human uses along the river corridor, notably fisheries (including two endangered species of suckers, and formerly salmon), timber harvest, agriculture, and livestock grazing. The complex history of land ownership and landuse, water control and diversion structures, and fishery alterations, provides several targets for attributing historic changes to channel and floodplain conditions. Recently, evolving societal values (as well as much outside money) are inspiring efforts by many entities to 'restore' the Sprague River watershed. In cooperation with the U.S. Fish and Wildlife Service, the Klamath Tribes, and many local landowners, we are launching an analysis of Sprague River channel and floodplain processes. The overall objective is to guide restoration activities by providing sound understanding of local geomorphic processes and conditions. To do this we are identifying key floodplain and channel processes, and investigating how they have been affected by historic floodplain activites and changes to the watershed. This is being accomplished by analysis of historic aerial photographs and maps, stratigraphic analysis of floodplain soils and geologic units, mapping of riparian vegetation conditions and changes, and quantitative analysis of high resolution LiDAR topography acquired for the entire river course in December 2004. Preliminary results indicate (1) much of the coarser (and more erodible) floodplain soils are largely composed of pumice deposited in the basin by the 7700 year BP eruption of Mount Mazama; and (2) the LiDAR digital elevation models provide a ready means of subdividing the river into segments with quantifiably different characteristics of channel width, sinuosity, slope, and incision (relative to adjacent floodplain elevations).

Long-term dynamics of a floodplain shallow lake in the Pantanal wetland: Is it all about climate?

PubMed

Silio-Calzada, Ana; Barquín, José; Huszar, Vera L M; Mazzeo, Nestor; Méndez, Fernando; Álvarez-Martínez, Jose Manuel

2017-12-15

Hydrological variability over seasonal and multi-annual timescales strongly shapes the ecological structure and functioning of floodplain ecosystems. The current IPCC climate scenario foresees an increase in the frequency of extreme events. This, in conjunction with other anthropogenic disturbances (e.g., river regulation or land-use changes) poses a serious threat to the natural functioning of these ecosystems. In this study we aimed to i) evaluate the long-term variability of the flooded area of the third largest floodplain lake in the Brazilian Pantanal using remote sensing techniques, and ii) analyze the possible factors influencing this variability. Changes in open-water and riparian floodplain-wetland vegetation areas were mapped by applying an ad hoc-developed remote-sensing method (including a newly developed normalized water index, NWI) to 221 Landsat-Thematic Mapper (TM)/Enhanced Thematic Mapper Plus (ETM+) images, acquired between 1984 and 2011. Added to the lake's natural swing between riparian floodplain-wetland vegetation expansion and retraction, our analyses revealed large interannual changes, grouped into three main periods within the studied time interval. Moreover, our results indicate that this floodplain-lake system is losing open-water area, paired with an increase in riparian floodplain-wetland vegetation. The system's long-term dynamics are not all climate related, but are the result of a combination of drivers. The start of the Manso dam's operation upstream of the studied system, and the subsequent river regulation because of the dam operation, coupled with climatic oscillation appear to be responsible for the observed changes. However, other factors which were not considered in this study might also be important in this process and contributing to the reduction of the system's resilience to droughts (e.g., land-use changes). This study illustrates the serious conservation risks that the Pantanal faces in the near future, given the current climate-change scenario and the accumulation of dam building projects in this region. Copyright © 2017 Elsevier B.V. All rights reserved.

Quantifying the Influence of Urbanization on a Coastal Floodplain

NASA Astrophysics Data System (ADS)

Sebastian, A.; Juan, A.; Bedient, P. B.

2016-12-01

The U.S. Gulf Coast is the fastest growing region in the United States; between 1960 and 2010, the number of housing units along the Gulf of Mexico increased by 246%, vastly outpacing growth in other parts of the country (NOAA 2013). Numerous studies have shown that increases in impervious surface associated with urbanization reduce infiltration and increase surface runoff. While empirical evidence suggests that changes in land use are leading to increased flood damage in overland areas, earlier studies have largely focused on the impacts of urbanization on surface runoff and watershed hydrology, rather than quantifying its influence on the spatial extent of flooding. In this study, we conduct a longitudinal assessment of the evolution of flood risk since 1970 in an urbanizing coastal watershed. Utilizing the distributed hydrologic model, Vflo®, in combination with the hydraulic model, HEC-RAS, we quantify the impact of localized land use/land cover (LULC) change on the spatial extent of flooding in the watershed and the underlying flood hazard structure. The results demonstrate that increases in impervious cover between 1970 and 2010 (34%) and 2010 and 2040 (18%) increase the size of the floodplain by 26 and 17%, respectively. Furthermore, the results indicate that the depth and frequency of flooding in neighborhoods within the 1% floodplain have increased substantially (see attached figure). Finally, this analysis provides evidence that outdated FEMA floodplain maps could be underestimating the extent of the floodplain by upwards of 25%, depending on the rate of urbanization in the watershed; and, that by incorporating physics-based distributed hydrologic models into floodplain studies, floodplain maps can be easily updated to reflect the most recent LULC information available. The methods presented in this study have important implications for the development of mitigation strategies in coastal areas, such as deterring future development in flood prone areas and directing flood mitigation efforts in already flood prone communities. ReferencesNational Oceanic and Atmospheric Administration (NOAA). (2013). National Coastal Population Report: Population Trends from 1970 to 2020.

Varying effects of geomorphic change on floodplain inundation and forest communities

NASA Astrophysics Data System (ADS)

Keim, R.; Johnson, E. L.; Edwards, B. L.; King, S. L.; Hupp, C. R.

2015-12-01

Overbank flooding in floodplains is an important control on vegetation, but effects of changing flooding are difficult to predict because sensitivities of plant communities to multidimensional flooding (frequency, depth, duration, and timing) are not well understood. We used HEC-RAS to model the changing flooding regime in the lower White River floodplain, Arkansas, in response to rapid incision of the Mississippi River in the 1930s, and quantified flood frequency, depth, and duration by forest community type. Incision has decreased flooding especially in terms of frequency, which is one of the most important variables for ecological processes. Modeled depth-duration curves varied more among floodplain reaches than among forest communities within the same reach, but forest communities are now arranged in accordance with new flood regimes in place after river incision. Forest responses to subtle geomorphic change are slower than other vegetation communities, so detection of the full ramifications of ecohydrologic change may require decades.

Changes in aquatic vegetation and floodplain land cover in the Upper Mississippi and Illinois rivers (1989–2000–2010)

USGS Publications Warehouse

DeJager, Nathan R.; Rohweder, Jason J.

2017-01-01

Quantifying changes in the cover of river-floodplain systems can provide important insights into the processes that structure these landscapes as well as the potential consequences to the ecosystem services they provide. We examined net changes in 13 different aquatic and floodplain land cover classes using photo interpreted maps of the navigable portions of the Upper Mississippi River (UMR, above the confluence with the Ohio River) and Illinois River from 1989 to 2000 and from 2000 to 2010. We detected net decreases in vegetated aquatic area in nearly all river reaches from 1989 to 2000. The only river reaches that experienced a subsequent recovery of vegetated aquatic area from 2000 to 2010 were located in the northern portion of the UMR (above navigation pool 14) and two reaches in the Illinois River. Changes on the floodplain were dominated by urban development, which increased in nearly every river reach studied from 1989 to 2000. Agricultural lands declined in most river reaches from 2000 to 2010. The loss of agricultural land cover in the northern UMR was accompanied by increases in forest cover, whereas in the lower UMR and Illinois River, declines in agriculture were accompanied by increases in forest and shallow marsh communities. The changes in aquatic vegetation occupied between 5 and 20% of the total aquatic area and are likely associated with previously reported regional improvements in water clarity, while smaller (1–15% of the total floodplain area) changes in anthropogenic land cover types on the floodplain are likely driven by broad-scale socio-economic conditions.

Mining-Related Sediment and Soil Contamination in a Large Superfund Site: Characterization, Habitat Implications, and Remediation.

PubMed

Juracek, K E; Drake, K D

2016-10-01

Historical mining activity (1850-1970) in the now inactive Tri-State Mining District provided an ongoing source of lead and zinc to the environment including the US Environmental Protection Agency Superfund site located in Cherokee County, southeast Kansas, USA. The resultant contamination adversely affected biota and caused human health problems and risks. Remediation in the Superfund site requires an understanding of the magnitude and extent of contamination. To provide some of the required information, a series of sediment and soil investigations were conducted in and near the Superfund site to characterize lead and zinc contamination in the aquatic and floodplain environments along the main-stem Spring River and its major tributaries. In the Superfund site, the most pronounced lead and zinc contamination, with concentrations that far exceed sediment quality guidelines associated with potential adverse biological effects, was measured for streambed sediments and floodplain soils located within or downstream from the most intensive mining-affected areas. Tributary streambeds and floodplains in affected areas are heavily contaminated with some sites having lead and zinc concentrations that are an order of magnitude (or more) greater than the sediment quality guidelines. For the main-stem Spring River, the streambed is contaminated but the floodplain is mostly uncontaminated. Measured lead and zinc concentrations in streambed sediments, lakebed sediments, and floodplain soils documented a persistence of the post-mining contamination on a decadal timescale. These results provide a basis for the prioritization, development, and implementation of plans to remediate contamination in the affected aquatic and floodplain environments within the Superfund site.

The storage time, age, and erosion hazard of laterally accreted sediment on the floodplain of a simulated meandering river

USGS Publications Warehouse

Bradley, D. Nathan; Tucker, Gregory E.

2013-01-01

A sediment particle traversing the fluvial system may spend the majority of the total transit time at rest, stored in various sedimentary deposits. Floodplains are among the most important of these deposits, with the potential to store large amounts of sediment for long periods of time. The virtual velocity of a sediment grain depends strongly on the amount of time spent in storage, but little is known about sediment storage times. Measurements of floodplain vegetation age have suggested that storage times are exponentially distributed, a case that arises when all the sediment on a floodplain is equally vulnerable to erosion in a given interval. This assumption has been incorporated into sediment routing models, despite some evidence that younger sediment is more likely to be eroded from floodplains than older sediment. We investigate the relationship between sediment age and erosion, which we term the “erosion hazard,” with a model of a meandering river that constructs its floodplain by lateral accretion. We find that the erosion hazard decreases with sediment age, leading to a storage time distribution that is not exponential. We propose an alternate model that requires that channel motion is approximately diffusive and results in a heavy tailed distribution of storage time. The model applies to timescales over which the direction of channel motion is uncorrelated. We speculate that the lower end of this range of time is set by the meander cutoff timescale and the upper end is set by processes that limit the width of the meander belt.

Characteristics and causal factors of hysteresis in the hydrodynamics of a large floodplain system: Poyang Lake (China)

NASA Astrophysics Data System (ADS)

Zhang, X. L.; Zhang, Q.; Werner, A. D.; Tan, Z. Q.

2017-10-01

A previous modeling study of the lake-floodplain system of Poyang Lake (China) revealed complex hysteretic relationships between stage, storage volume and surface area. However, only hypothetical causal factors were presented, and the reasons for the occurrence of both clockwise and counterclockwise hysteretic functions were unclear. The current study aims to address this by exploring further Poyang Lake's hysteretic behavior, including consideration of stage-flow relationships. Remotely sensed imagery is used to validate the water surface areas produced by hydrodynamic modeling. Stage-area relationships obtained using the two methods are in strong agreement. The new results reveal a three-phase hydrological regime in stage-flow relationships, which assists in developing improved physical interpretation of hysteretic stage-area relationships for the lake-floodplain system. For stage-area relationships, clockwise hysteresis is the result of classic floodplain hysteretic processes (e.g., restricted drainage of the floodplain during recession), whereas counterclockwise hysteresis derives from the river hysteresis effect (i.e., caused by backwater effects). The river hysteresis effect is enhanced by the time lag between the peaks of catchment inflow and Yangtze discharge (i.e., the so-called Yangtze River blocking effect). The time lag also leads to clockwise hysteresis in the relationship between Yangtze River discharge and lake stage. Thus, factors leading to hysteresis in other rivers, lakes and floodplains act in combination within Poyang Lake to create spatial variability in hydrological hysteresis. These effects dominate at different times, in different parts of the lake, and during different phases of the lake's water level fluctuations, creating the unique hysteretic hydrological behavior of Poyang Lake.

Evaluating the 100 year floodplain as an indicator of flood risk in low-lying coastal watersheds

NASA Astrophysics Data System (ADS)

Sebastian, A.; Brody, S.; Bedient, P. B.

2013-12-01

The Gulf of Mexico is the fastest growing region in the United States. Since 1960, the number of housing units built in the low-lying coastal counties has increased by 246%. The region experiences some of the most intense rainfall events in the country and coastal watersheds are prone to severe flooding characterized by wide floodplains and ponding. This flooding is further exacerbated as urban development encroaches on existing streams and waterways. While the 100 year floodplain should play an important role in our ability to develop disaster resilient communities, recent research has indicated that existing floodplain delineations are a poor indicator of actual flood losses in low-lying coastal regions. Between 2001 and 2005, more than 30% of insurance claims made to FEMA in the Gulf Coast region were outside of the 100 year floodplain and residential losses amounted to more than $19.3 billion. As population density and investments in this region continue to increase, addressing flood risk in coastal communities should become a priority for engineers, urban planners, and decision makers. This study compares the effectiveness of 1-D and a 2-D modeling approaches to spatially capture flood claims from historical events. Initial results indicate that 2-D models perform much better in coastal environments and may serve better for floodplain modeling helping to prevent unintended losses. The results of this study encourage a shift towards better engineering practices using existing 2-D models in order to protect resources and provide guidance for urban development in low-lying coastal regions.

Water balance of a lake with floodplain buffering: Lake Tana, Blue Nile Basin, Ethiopia

NASA Astrophysics Data System (ADS)

Dessie, Mekete; Verhoest, Niko E. C.; Pauwels, Valentijn R. N.; Adgo, Enyew; Deckers, Jozef; Poesen, Jean; Nyssen, Jan

2015-03-01

Lakes are very important components of the earth's hydrological cycle, providing a variety of services for humans and ecosystem functioning. For a sustainable use of lakes, a substantial body of knowledge on their water balance is vital. We present here a detailed daily water balance analysis for Lake Tana, the largest lake in Ethiopia and the source of the Blue Nile. Rainfall on the lake is determined by Thiessen polygon procedure, open water evaporation is estimated by the Penman-combination equation and observed inflows for the gauged catchments as well as outflow data at the two lake outlets are directly used. Runoff from ungauged catchments is estimated using a simple rainfall-runoff model and runoff coefficients. Hillslope catchments and floodplains are treated separately, which makes this study unique compared to previous water balance studies. Impact of the floodplain on the lake water balance is analyzed by conducting scenario-based studies. We found an average yearly abstraction of 420 × 106 m3 or 6% of river inflows to the lake by the floodplain in 2012 and 2013. Nearly 60% of the inflow to the lake is from the Gilgel Abay River. Simulated lake levels compare well with the observed lake levels (R2 = 0.95) and the water balance can be closed with a closure error of 82 mm/year (3.5% of the total lake inflow). This study demonstrates the importance of floodplains and their influence on the water balance of the lake and the need of incorporating the effects of floodplains and water abstraction for irrigation to improve predictions.

Contribution of local knowledge to understand socio-hydrological dynamics. Examples from a study in Senegal river valley

NASA Astrophysics Data System (ADS)

Bruckmann, Laurent

2017-04-01

In developing countries many watersheds are low monitored. However, rivers and its floodplains provides ecosystem services to societies, especially for agriculture, grazing and fishing. This uses of rivers and floodplains offer to communities an important local knowledge about hydrological dynamics. This knowledge can be useful to researchers studying ecological or hydrological processes. This presentation aims to discuss and present the interest of using qualitative data from surveys and interviews to understand relations between society and hydrology in floodplain from developing countries, but also to understand changes in hydrological dynamics. This communication is based on a PhD thesis held on from 2012 and 2016, that analyzes socio-ecological changes in the floodplain of the Senegal river floodplain following thirty years of transboundary water management. The results of this work along Senegal river valley suggest that the use of social data and qualitative study are beneficial in understanding the hydrological dynamics in two dimensions. First, it established the importance of perception of hydrological dynamics, particularly floods, on local water management and socio-agricultural trajectories. This perception of people is strictly derived from ecosystems services provided by river and its floodplain. Second, surveys have enlightened new questions concerning the hydrology of the river that are often cited by people, like a decrease of flood water fertility. This type of socio-hydrological study, combining hydrological and qualitative data, has great potential for guiding water management policies. Using local knowledge in their analyzes, researchers also legitimize river users, who are for the most part forgotten by water policies.

Mining-Related Sediment and Soil Contamination in a Large Superfund Site: Characterization, Habitat Implications, and Remediation

NASA Astrophysics Data System (ADS)

Juracek, K. E.; Drake, K. D.

2016-10-01

Historical mining activity (1850-1970) in the now inactive Tri-State Mining District provided an ongoing source of lead and zinc to the environment including the US Environmental Protection Agency Superfund site located in Cherokee County, southeast Kansas, USA. The resultant contamination adversely affected biota and caused human health problems and risks. Remediation in the Superfund site requires an understanding of the magnitude and extent of contamination. To provide some of the required information, a series of sediment and soil investigations were conducted in and near the Superfund site to characterize lead and zinc contamination in the aquatic and floodplain environments along the main-stem Spring River and its major tributaries. In the Superfund site, the most pronounced lead and zinc contamination, with concentrations that far exceed sediment quality guidelines associated with potential adverse biological effects, was measured for streambed sediments and floodplain soils located within or downstream from the most intensive mining-affected areas. Tributary streambeds and floodplains in affected areas are heavily contaminated with some sites having lead and zinc concentrations that are an order of magnitude (or more) greater than the sediment quality guidelines. For the main-stem Spring River, the streambed is contaminated but the floodplain is mostly uncontaminated. Measured lead and zinc concentrations in streambed sediments, lakebed sediments, and floodplain soils documented a persistence of the post-mining contamination on a decadal timescale. These results provide a basis for the prioritization, development, and implementation of plans to remediate contamination in the affected aquatic and floodplain environments within the Superfund site.

Large-scale controls on potential respiration and denitrification in riverine floodplains

PubMed Central

Welti, Nina; Bondar-Kunze, Elisabeth; Singer, Gabriel; Tritthart, Michael; Zechmeister-Boltenstern, Sophie; Hein, Thomas; Pinay, Gilles

2012-01-01

Restoration measures of deteriorated river ecosystems generally aim at increasing the spatial heterogeneity and connectivity of these systems in order to increase biodiversity and ecosystem stability. While this is believed to benefit overall ecological integrity, consequences of such restoration projects on biogeochemical processes per se (i.e. ecosystem functioning) in fluvial systems are rarely considered. We address these issues by evaluating the characteristics of surface water connection between side arms and the main river channel in a former braided river section and the role and degree of connectivity (i.e. duration of surface water connection) on the sediment biogeochemistry. We hypothesized that potential respiration and denitrification would be controlled by the degree of hydrological connectivity, which was increased after floodplain restoration. We measured potential microbial respiration (SIR) and denitrification (DEA) and compared a degraded floodplain section of the Danube River with a reconnected and restored floodplain in the same river section. Re-establishing surface water connection altered the controls on sediment microbial respiration and denitrification ultimately impacting potential microbial activities. Meta-variables were created to characterize the effects of hydrology, morphology, and the available carbon and nutrient pools on potential microbial processing. Mantel statistics and path analysis were performed and demonstrate a hierarchy where the effects of hydrology on the available substrates and microbial processing are mediated by the morphology of the floodplain. In addition, these processes are highest in the least connected sites. Surface water connection, mediated by morphology regulates the potential denitrification rate and the ratio of N2O to N2 emissions, demonstrating the effects of restoration in floodplain systems. PMID:23565037

Present-day African analogue of a pre-European Amazonian floodplain fishery shows convergence in cultural niche construction.

PubMed

McKey, Doyle B; Durécu, Mélisse; Pouilly, Marc; Béarez, Philippe; Ovando, Alex; Kalebe, Mashuta; Huchzermeyer, Carl F

2016-12-27

Erickson [Erickson CL (2000) Nature 408 (6809):190-193] interpreted features in seasonal floodplains in Bolivia's Beni savannas as vestiges of pre-European earthen fish weirs, postulating that they supported a productive, sustainable fishery that warranted cooperation in the construction and maintenance of perennial structures. His inferences were bold, because no close ethnographic analogues were known. A similar present-day Zambian fishery, documented here, appears strikingly convergent. The Zambian fishery supports Erickson's key inferences about the pre-European fishery: It allows sustained high harvest levels; weir construction and operation require cooperation; and weirs are inherited across generations. However, our comparison suggests that the pre-European system may not have entailed intensive management, as Erickson postulated. The Zambian fishery's sustainability is based on exploiting an assemblage dominated by species with life histories combining high fecundity, multiple reproductive cycles, and seasonal use of floodplains. As water rises, adults migrate from permanent watercourses into floodplains, through gaps in weirs, to feed and spawn. Juveniles grow and then migrate back to dry-season refuges as water falls. At that moment fishermen set traps in the gaps, harvesting large numbers of fish, mostly juveniles. In nature, most juveniles die during the first dry season, so that their harvest just before migration has limited impact on future populations, facilitating sustainability and the adoption of a fishery based on inherited perennial structures. South American floodplain fishes with similar life histories were the likely targets of the pre-European fishery. Convergence in floodplain fish strategies in these two regions in turn drove convergence in cultural niche construction.

Flood pattern and weather determine Populus leaf litter breakdown and nitrogen dynamics on a cold desert floodplain

USGS Publications Warehouse

Andersen, D.C.; Nelson, S.M.

2006-01-01

Patterns and processes involved in litter breakdown on desert river floodplains are not well understood. We used leafpacks containing Fremont cottonwood (Populus deltoides subsp. wislizenii) leaf litter to investigate the roles of weather and microclimate, flooding (immersion), and macroinvertebrates on litter organic matter (OM) and nitrogen (N) loss on a floodplain in a cool-temperate semi-arid environment (Yampa River, northwestern Colorado, USA). Total mass of N in fresh autumn litter fell by ∼20% over winter and spring, but in most cases there was no further N loss prior to termination of the study after 653 days exposure, including up to 20 days immersion during the spring flood pulse. Final OM mass was 10–40% of initial values. The pattern of OM and N losses suggested most N would be released outside the flood season, when retention within the floodplain would be likely. The exclusion of macroinvertebrates modestly reduced the rate of OM loss (by about 10%) but had no effect on N dynamics over nine months. Immersion in floodwater accelerated OM loss, but modest variation in litter quality did not affect the breakdown rate. These results are consistent with the concept that decomposition on desert floodplains progresses much as does litter processing in desert uplands, but with periodic bouts of processing typical of aquatic environments when litter is inundated by floodwaters. The strong dependence of litter breakdown rate on weather and floods means that climate change or river flow management can easily disrupt floodplain nutrient dynamics.

Mining-related sediment and soil contamination in a large Superfund site: Characterization, habitat implications, and remediation

USGS Publications Warehouse

Juracek, Kyle E.; Drake, K. D.

2016-01-01

Historical mining activity (1850–1970) in the now inactive Tri-State Mining District provided an ongoing source of lead and zinc to the environment including the US Environmental Protection Agency Superfund site located in Cherokee County, southeast Kansas, USA. The resultant contamination adversely affected biota and caused human health problems and risks. Remediation in the Superfund site requires an understanding of the magnitude and extent of contamination. To provide some of the required information, a series of sediment and soil investigations were conducted in and near the Superfund site to characterize lead and zinc contamination in the aquatic and floodplain environments along the main-stem Spring River and its major tributaries. In the Superfund site, the most pronounced lead and zinc contamination, with concentrations that far exceed sediment quality guidelines associated with potential adverse biological effects, was measured for streambed sediments and floodplain soils located within or downstream from the most intensive mining-affected areas. Tributary streambeds and floodplains in affected areas are heavily contaminated with some sites having lead and zinc concentrations that are an order of magnitude (or more) greater than the sediment quality guidelines. For the main-stem Spring River, the streambed is contaminated but the floodplain is mostly uncontaminated. Measured lead and zinc concentrations in streambed sediments, lakebed sediments, and floodplain soils documented a persistence of the post-mining contamination on a decadal timescale. These results provide a basis for the prioritization, development, and implementation of plans to remediate contamination in the affected aquatic and floodplain environments within the Superfund site.

Carbon Transport, Transformation and Retention in Tropical Systems: The Lower Tana River Corridor as a Natural Laboratory

NASA Astrophysics Data System (ADS)

Govers, G.; Omengo, F.; Geeraert, N.; Bouillon, S.; Neyens, G.

2016-12-01

The lower Tana river in Kenya is an active river carrying high sediment and carbon loads, while lateral influxes from tributaries are very limited. We used this river as a natural laboratory to study the dynamics of carbon in the river-floodplain system. We measured carbon fluxes in the river as well as rates of carbon processing. Furthermore, we assessed carbon deposition in the floodplain and carbon mobilisation by river migration. We show that both within-river carbon dynamics as well as river-floodplain interaction can only be understood by accounting for autogenic river processes: the amounts of sediment (5-6 Mt yr-1) and particulate organic carbon (120-180 Mg yr-1) that are re-mobilised within the river reach (300 km) are similar to the amounts the reach receives from upstream. Carbon and sediment mobilisation are compensated for by deposition, both in the floodplain and within the river (point bars). This intensive exchange explains why the suspended sediment in the Tana river becomes finer (and more enriched in carbon) in the downstream direction, despite the deposition of fine, carbon-rich sediments in the floodplain. Contrary to what is found in temperate floodplains, overall carbon burial appears not to be very effective: most buried carbon is mineralised within decades after burial. However, burial efficiency is much higher for allochthonous organic carbon (deposited by the river) than for autochthonous organic carbon (sourced from local primary production). The Tana river does not only exchange carbon with its floodplain through deposition and remobilisation of POC. When floods occur, the floodplain acts as an important source of dissolved organic and inorganic carbon which is not only produced by organic carbon decomposition but also by weathering. Finally, there is significant CO2 outgassing from the Tana river, releasing 3-5 Mg C yr-1 to the atmosphere. Our study highlights the role of tropical river corridors as highly dynamic environments, which may be strongly affected by human management and/or climatic change. The planned construction of a major dam in the upper Tana is likely to steady the river's discharge and will limit lateral river migration and flooding, which may transform the lower Tana from a net sediment (and to a lesser extent, carbon) sink to a source.

Spatial hydrological flow processes, water quality, sediment and vegetation community distributions in a natural floodplain fen - implication for the Flood Pulse Concept

NASA Astrophysics Data System (ADS)

Keizer, Floris; Schot, Paul; Wassen, Martin; Kardel, Ignacy; Okruszko, Tomasz

2017-04-01

We studied spatial patterns in inundation water quality, sediment and vegetation distribution in a floodplain fen in Poland to map interacting peatland hydrological processes. Using PCA and K-means cluster analysis, we identified four water types, related to river water inundation, discharge of clean and polluted groundwater, and precipitation and snowmelt dilution. Spatially, these hydrochemical water types are related to known water sources in the floodplain and occupy distinctive zones. River water is found along the river, clean and polluted groundwater at the valley margins and groundwater diluted with precipitation and snowmelt water in the central part of the floodplain. This implies that, despite the floodplain being completely inundated, nutrient input from river flooding occurs only in a relatively narrow zone next to the river. Our findings question the relevance of the edge of inundation, as presented in the Flood Pulse Concept, as delineating the zone of input and turnover of nutrients. Secondly, we studied rich-fen and freshwater vegetation community distributions in relation to the presented inundation water quality types. We successfully determined inundation water quality preference for 14 out of 17 studied rich-fen and freshwater communities in the floodplain. Spatial patterns in preference show vegetation with attributed river water preference to occur close to the river channel, with increasing distance to the river followed by communities with no preference, diluted groundwater preference in the central part, and clean and polluted groundwater preference at the valley margins. In inundation water, nutrients are known to be transported mainly as attached to sediment, besides in dissolved state. This means that in the zone where sediment deposition occurs, nutrient input can be a relevant contribution to the nutrient input of the floodplain. We found a significant decrease in sediment-attached nutrient deposition with distance from the river. Sediment-attached nutrients correlated better to aboveground standing biomass than dissolved nutrients. These findings further reduce the spatial zone where significant nutrient input is influenced by transport from the river, compared to the zone influenced by dissolved nutrients. Our findings indicate the need for a revision of the Flood Pulse Concept for temperate river with multiple water sources, as peatland hydrological processes significantly influence spatial floodplain vegetation distribution.

Hydrodynamic Modeling to Assess the Impact of Man-Made Fishing Canals on Floodplain Dynamics: A Case Study in the Logone Floodplain

NASA Astrophysics Data System (ADS)

Shastry, A. R.; Durand, M. T.; Fernandez, A.; Phang, S. C.; Hamilton, I.; Laborde, S.; Mark, B. G.; Moritz, M.; Neal, J. C.

2017-12-01

The Logone floodplain in northern Cameroon, also known as Yaayre, is an excellent example of coupled human-natural systems because of strong couplings between social, ecological and hydrologic systems. Overbank flow from the Logone River inundates the floodplain ( 8000 km2) annually and the flood is essential for fish populations and the fishers that depend on them for their livelihood. However, a recent trend of construction of fishing canals threatens to change flood dynamics like duration and timing of onset and may reduce fish productivity. Fishers dig canals during dry season, which are used to catch fish by collecting and channeling water during the flood recession. By connecting the floodplain to the river, these fishing canals act an extension of the river drainage network. The goal of this study is to characterize the relationship between the observed exponential increase in numbers of fishing canals and flood dynamics. We modelled the Logone floodplain as a two-dimensional hydrodynamic model with sub-grid parameterizations of channels using LISFLOOD-FP. We use a simplified version of the hydraulic system at a grid-cell size of 1-km, upscaled using a new high accuracy map of global terrain elevations from Shuttle Radar Topography Mission (SRTM). Using data from a field-collected survey performed in 2014, 1120 fishing canal were collated and parameterized as 111 sub-grid channels and the fishnet structure was represented as a combination of weir and mesh screens. 49 mapped floodplain depressions were also represented as sub-grid channels. In situ discharge observations available at Katoa between 2001 and 2007 were used as input for the model. Preliminary results show that presence of canals resulted in a 24% quicker recession of water in the natural depressions showing increasing canal numbers lead to quicker flood recession. We also investigate the rate of effect increasing number of fishing canals has on flood recession by simulating varying numbers of canals. This model will be integrated within a larger modelling effort to quantify the floodplain's hydraulic, biological and human couplings. This larger integrated model will link inputs and outputs across three different models (flood, fish and fisher) for a holistic insight into the drivers and dynamics of this coupled human and natural system.

Basin-scale impacts of hydropower development on the Mompós Depression wetlands, Colombia

NASA Astrophysics Data System (ADS)

Angarita, Héctor; Wickel, Albertus J.; Sieber, Jack; Chavarro, John; Maldonado-Ocampo, Javier A.; Herrera-R., Guido A.; Delgado, Juliana; Purkey, David

2018-05-01

A number of large hydropower dams are currently under development or in an advanced stage of planning in the Magdalena River basin, Colombia, spelling uncertainty for the Mompós Depression wetlands, one of the largest wetland systems in South America at 3400 km2. Annual large-scale inundation of floodplains and their associated wetlands regulates water, nutrient, and sediment cycles, which in turn sustain a wealth of ecological processes and ecosystem services, including critical food supplies. In this study, we implemented an integrated approach focused on key attributes of ecologically functional floodplains: (1) hydrologic connectivity between the river and the floodplain, and between upstream and downstream sections; (2) hydrologic variability patterns and their links to local and regional processes; and (3) the spatial scale required to sustain floodplain-associated processes and benefits, like migratory fish biodiversity. The implemented framework provides an explicit quantification of the nonlinear or direct response relationship of those considerations with hydropower development. The proposed framework was used to develop a comparative analysis of the potential effects of the hydropower expansion necessary to meet projected 2050 electricity requirements. As part of this study, we developed an enhancement of the Water Evaluation and Planning system (WEAP) that allows resolution of the floodplains water balance at a medium scale (˜ 1000 to 10 000 km2) and evaluation of the potential impacts of upstream water management practices. In the case of the Mompós Depression wetlands, our results indicate that the potential additional impacts of new hydropower infrastructure with respect to baseline conditions can range up to one order of magnitude between scenarios that are comparable in terms of energy capacity. Fragmentation of connectivity corridors between lowland floodplains and upstream spawning habitats and reduction of sediment loads show the greatest impacts, with potential reductions of up to 97.6 and 80 %, respectively, from pre-dam conditions. In some development scenarios, the amount of water regulated and withheld by upstream infrastructure is of similar magnitude to existing fluxes involved in the episodic inundation of the floodplain during dry years and, thus, can also induce substantial changes in floodplain seasonal dynamics of average-to-dry years in some areas of the Mompós Depression.

40 CFR 257.8 - Floodplains.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Floodplains. 257.8 Section 257.8 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... relatively flat areas adjoining inland and coastal waters, including flood-prone areas of offshore islands...

40 CFR 257.8 - Floodplains.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Floodplains. 257.8 Section 257.8 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... relatively flat areas adjoining inland and coastal waters, including flood-prone areas of offshore islands...

40 CFR 257.8 - Floodplains.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Floodplains. 257.8 Section 257.8 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... relatively flat areas adjoining inland and coastal waters, including flood-prone areas of offshore islands...

40 CFR 257.8 - Floodplains.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Floodplains. 257.8 Section 257.8 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... relatively flat areas adjoining inland and coastal waters, including flood-prone areas of offshore islands...

40 CFR 257.8 - Floodplains.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Floodplains. 257.8 Section 257.8 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... relatively flat areas adjoining inland and coastal waters, including flood-prone areas of offshore islands...

18 CFR 725.4 - Definitions.

Code of Federal Regulations, 2010 CFR

2010-04-01

... EXECUTIVE ORDERS 11988, FLOODPLAIN MANAGEMENT AND 11990, PROTECTION OF WETLANDS Introduction § 725.4... definitions listed in the Glossary of the Council's Floodplain Management Guidelines for Implementing E.O... Council's Principles, Standards and Procedures (P,S,&P), provision of financial assistance for State...

10 CFR 1022.5 - Applicability.

Code of Federal Regulations, 2010 CFR

2010-01-01

... ENERGY (GENERAL PROVISIONS) COMPLIANCE WITH FLOODPLAIN AND WETLAND ENVIRONMENTAL REVIEW REQUIREMENTS... Commission. (b) This part applies to all proposed floodplain or wetland actions, including those sponsored... allocations to private parties for activities involving a wetland that are located on non-Federal property. (d...

IMPACTS ON FLOODPLAINS BY AN INVASIVE SHRUB, BUDDLEJA DAVIDII

EPA Science Inventory

Despite its popularity, the ornamental, Buddleja davidii, a woody shrub of Asian origin, is considered problematic because of its ability to rapidly colonize and dominate floodplain and riparian ecosystems. Dominance during early succession may influence community dynamics and ec...

Flooding tolerance of four floodplain meadow species depends on age.

PubMed

Gattringer, Johannes P; Donath, Tobias W; Eckstein, R Lutz; Ludewig, Kristin; Otte, Annette; Harvolk-Schöning, Sarah

2017-01-01

Numerous restoration campaigns focused on re-establishing species-rich floodplain meadows of Central Europe, whose species composition is essentially controlled by regular flooding. Climate change predictions expect strong alterations on the discharge regime of Europe's large rivers with little-known consequences on floodplain meadow plants. In this study, we aim to determine the effects of flooding on seedlings of different ages of four typical flood meadow species. To this end, we flooded seedlings of two familial pairs of flood meadow species of wetter and dryer microhabitats for 2 weeks each, starting 2, 4, 6, and 8 weeks after seedling germination, respectively. We show that a 2-week-flooding treatment had a negative effect on performance of seedlings younger than 6 weeks. Summer floods with high floodwater temperatures may have especially detrimental effects on seedlings, which is corroborated by previous findings. As expected, the plants from wet floodplain meadow microhabitats coped better with the flooding treatment than those from dryer microhabitats. In conclusion, our results suggest that restoration measures may perform more successfully if seedlings of restored species are older than the critical age of about 6 weeks before a spring flooding begins. Seasonal flow patterns may influence vegetation dynamics of floodplain meadows and should, therefore, be taken into account when timing future restoration campaigns.

Flooding tolerance of four floodplain meadow species depends on age

PubMed Central

Donath, Tobias W.; Eckstein, R. Lutz; Ludewig, Kristin; Otte, Annette; Harvolk-Schöning, Sarah

2017-01-01

Numerous restoration campaigns focused on re-establishing species-rich floodplain meadows of Central Europe, whose species composition is essentially controlled by regular flooding. Climate change predictions expect strong alterations on the discharge regime of Europe’s large rivers with little-known consequences on floodplain meadow plants. In this study, we aim to determine the effects of flooding on seedlings of different ages of four typical flood meadow species. To this end, we flooded seedlings of two familial pairs of flood meadow species of wetter and dryer microhabitats for 2 weeks each, starting 2, 4, 6, and 8 weeks after seedling germination, respectively. We show that a 2-week-flooding treatment had a negative effect on performance of seedlings younger than 6 weeks. Summer floods with high floodwater temperatures may have especially detrimental effects on seedlings, which is corroborated by previous findings. As expected, the plants from wet floodplain meadow microhabitats coped better with the flooding treatment than those from dryer microhabitats. In conclusion, our results suggest that restoration measures may perform more successfully if seedlings of restored species are older than the critical age of about 6 weeks before a spring flooding begins. Seasonal flow patterns may influence vegetation dynamics of floodplain meadows and should, therefore, be taken into account when timing future restoration campaigns. PMID:28467463

A data driven approach using Takagi-Sugeno models for computationally efficient lumped floodplain modelling

NASA Astrophysics Data System (ADS)

Wolfs, Vincent; Willems, Patrick

2013-10-01

Many applications in support of water management decisions require hydrodynamic models with limited calculation time, including real time control of river flooding, uncertainty and sensitivity analyses by Monte-Carlo simulations, and long term simulations in support of the statistical analysis of the model simulation results (e.g. flood frequency analysis). Several computationally efficient hydrodynamic models exist, but little attention is given to the modelling of floodplains. This paper presents a methodology that can emulate output from a full hydrodynamic model by predicting one or several levels in a floodplain, together with the flow rate between river and floodplain. The overtopping of the embankment is modelled as an overflow at a weir. Adaptive neuro fuzzy inference systems (ANFIS) are exploited to cope with the varying factors affecting the flow. Different input sets and identification methods are considered in model construction. Because of the dual use of simplified physically based equations and data-driven techniques, the ANFIS consist of very few rules with a low number of input variables. A second calculation scheme can be followed for exceptionally large floods. The obtained nominal emulation model was tested for four floodplains along the river Dender in Belgium. Results show that the obtained models are accurate with low computational cost.

Nutrient dynamics in the lower Mississippi river floodplain: Comparing present and historic hydrologic conditions

USGS Publications Warehouse

Schramm, H.L.; Cox, M.S.; Tietjen, T.E.; Ezell, A.W.

2009-01-01

Alterations to the lower Mississippi River-floodplain ecosystem to facilitate commercial navigation and to reduce flooding of agricultural lands and communities in the historic floodplain have changed the hydrologic regime. As a result, the flood pulse usually has a lower water level, is of shorter duration, has colder water temperatures, and a smaller area of floodplain is inundated. Using average hydrologic conditions and water temperatures, we used established nitrogen and phosphorus processes in soils, an aquatic ecosystem model, and fish bioenergetic models to provide approximations of nitrogen and phosphorus flux in Mississippi River flood waters for the present conditions of a 2-month (mid-March to mid-May) flood pulse and for a 3-month (mid-March to mid-June), historic flood pulse. We estimated that the soils and aquatic biota can remove or sequester 542 and 976 kg nitrogen ha-1 during the present and historic hydrologic conditions, respectively. Phosphorus, on the other hand, will be added to the water largely as a result of anaerobic soil conditions but moderated by biological uptake by aquatic biota during both present and historic hydrologic conditions. The floodplain and associated water bodies may provide an important management opportunity for reducing downstream transport of nitrogen in Mississippi River waters. ?? 2009, The Society of Wetland Scientists.

High genetic diversity among and within bitter manioc varieties cultivated in different soil types in Central Amazonia.

PubMed

Alves-Pereira, Alessandro; Peroni, Nivaldo; Cavallari, Marcelo Mattos; Lemes, Maristerra R; Zucchi, Maria Imaculada; Clement, Charles R

2017-01-01

Although manioc is well adapted to nutrient-poor Oxisols of Amazonia, ethnobotanical observations show that bitter manioc is also frequently cultivated in the highly fertile soils of the floodplains and Amazonian dark earths (ADE) along the middle Madeira River. Because different sets of varieties are grown in each soil type, and there are agronomic similarities between ADE and floodplain varieties, it was hypothesized that varieties grown in ADE and floodplain were more closely related to each other than either is to varieties grown in Oxisols. We tested this hypothesis evaluating the intra-varietal genetic diversity and the genetic relationships among manioc varieties commonly cultivated in Oxisols, ADE and floodplain soils. Genetic results did not agree with ethnobotanical expectation, since the relationships between varieties were variable and most individuals of varieties with the same vernacular name, but grown in ADE and floodplain, were distinct. Although the same vernacular name could not always be associated with genetic similarities, there is still a great amount of variation among the varieties. Many ecological and genetic processes may explain the high genetic diversity and differentiation found for bitter manioc varieties, but all contribute to the maintenance and amplification of genetic diversity within the manioc in Central Amazonia.

Floodplain Assessment for the Middle Los Alamos Canyon Aggregate Area Investigations in Technical Area 02 at Los Alamos National Laboratory

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

Hathcock, Charles Dean

The proposed action being assessed in this document occurs in TA-02 in the bottom of Los Alamos Canyon. The DOE proposes to conduct soil sampling at AOC 02-011 (d), AOC 02- 011(a)(ii), and SWMU 02-005, and excavate soils in AOC 02-011(a)(ii) as part of a corrective actions effort. Additional shallow surface soil samples (soil grab samples) will be collected throughout the TA-02 area, including within the floodplain, to perform ecotoxicology studies (Figures 1 and 2). The excavation boundaries in AOC 02-011(a)(ii) are slightly within the delineated 100-year floodplain. The project will use a variety of techniques for soil sampling andmore » remediation efforts to include hand/digging, standard hand auger/sampling, excavation using machinery such as backhoe and front end loader and small drill rig. Heavy equipment will traverse the floodplain and spoils piles will be staged in the floodplain within developed or previously disturbed areas (e.g., existing paved roads and parking areas). The project will utilize and maintain appropriate best management practices (BMPs) to contain excavated materials, and all pollutants, including oil from machinery/vehicles. The project will stabilize disturbed areas as appropriate at the end of the project.« less

High genetic diversity among and within bitter manioc varieties cultivated in different soil types in Central Amazonia

PubMed Central

Alves-Pereira, Alessandro; Peroni, Nivaldo; Cavallari, Marcelo Mattos; Lemes, Maristerra R.; Zucchi, Maria Imaculada; Clement, Charles R.

2017-01-01

Abstract Although manioc is well adapted to nutrient-poor Oxisols of Amazonia, ethnobotanical observations show that bitter manioc is also frequently cultivated in the highly fertile soils of the floodplains and Amazonian dark earths (ADE) along the middle Madeira River. Because different sets of varieties are grown in each soil type, and there are agronomic similarities between ADE and floodplain varieties, it was hypothesized that varieties grown in ADE and floodplain were more closely related to each other than either is to varieties grown in Oxisols. We tested this hypothesis evaluating the intra-varietal genetic diversity and the genetic relationships among manioc varieties commonly cultivated in Oxisols, ADE and floodplain soils. Genetic results did not agree with ethnobotanical expectation, since the relationships between varieties were variable and most individuals of varieties with the same vernacular name, but grown in ADE and floodplain, were distinct. Although the same vernacular name could not always be associated with genetic similarities, there is still a great amount of variation among the varieties. Many ecological and genetic processes may explain the high genetic diversity and differentiation found for bitter manioc varieties, but all contribute to the maintenance and amplification of genetic diversity within the manioc in Central Amazonia. PMID:28399193

Preliminary paleohydrological interpretation of an Amazon floodplain system based on seismic stratigraphy: Varzea do Lago Grande do Curuai, Pará, Brazil.

NASA Astrophysics Data System (ADS)

Amorim, M. A.; Moreira-Turcq, P.; Turcq, B.

2009-04-01

The aquatic lacustrine ecosystems are depositional environments that register in yours sediments the process that occurs on the own site and in the all drainage basin. The Amazonas River and its tributaries are followed along your upward and downward course by several floodplains that cover a large area of environs 300.000 km2. These sites are dynamic and complexes systems. Floodplains affect the erosion the transport and the sedimentation flux in the system and it has a special importance for carbon cycle due yours high productivity. In the floodplains systems the sediment deposition occurs in a different scale of time period. In these work, we study the "Varzea Grande do Curuai" which size varies from 1340km2 during the dry season, to 3600 km2 during the wet season, according to the level of the river. This floodplain is located on the southern margin of the Amazonas River, close to the city of Óbidos, Pará-Brazil, in the Lower Amazonas. The floodplain contains several white water lakes such as Grande, Poção, Santa Ninha and Salé Lakes, and black water lakes such as the Curumucuri and Açaí Lakes. These lakes are connected to each other and to the Amazonas River by small channels, some of which are permanently connected to the river and others not, depending on the variations of the water level. The purpose of this work is to reconstruct past sedimentary processes using seismic stratigraphy profiles realized all along the floodplain lakes and sediment cores collected at strategic sites. The sedimentary patterns observed in the seismic profiles are horizontal layers, highly reflective unpenetrated levels and paleochannels that could have been formed during the Holocene. The larger quantity of paleochannels along the lakes has been observed in the Grande and Salé lakes. The paleochannels in the Grande Lake would indicate a migration of actual depositional ridge that separates the floodplain from the river. In the Salé Lake, the paleochannels indicate that the region has suffered hydrological alterations. A comparison between the images of the floodplain in two different seasons (flooded and dry) with the stratigraphy profile, indicate that at sites that are emerged in the dry season there is no penetration of acoustic waves, the bottom of the lakes forming then a strong reflector.These sediments are hard due to a lower water content. The typical layers found in almost all the lakes were planar strata, characteristic of lacustrine sedimentation. These strata are covering the paleochannel structures and a second lower horizontal strong reflector. It should indicate a past environment where the water level was lower; the sediment surface was exposed during low water periods and eroded by channels draining the water to a lowered river during the lowering water season. This lower river and floodplain levels must be related to a lower sea level and/or to a dryer or more contrasted climate during the Holocene.

Quantifying Spatially Integrated Floodplain and Wetland Systems for the Conterminous US

EPA Science Inventory

Wetlands interact with other waters across a variable connectivity continuum, from permanent to transient, from fast to slow, and from primarily surface water to exclusively groundwater flows. Floodplain wetlands typically experience fast and frequent surface and near-surface gro...

GIS For Floodplain Mapping in Design of Highway Drainage Facilities

DOT National Transportation Integrated Search

1998-08-01

Since the 1960s,civil engineers have employed a variety of computer models for stream floodplain analysis. HEC-2 and its Windows counterpart, HEC-RAS, have been the principal models used for such analyses. A significant deficiency of these programs i...

7 CFR 1942.310 - Other considerations.

Code of Federal Regulations, 2011 CFR

2011-01-01

...) Floodplains and wetlands. All projects must comply with Executive Order 11988 “Floodplain Management” and... grant program established by this subpart is to improve business, industry and employment in rural areas... projects that minimize the potential to adversely impact the environment. (2) Technical assistance. The...

43 CFR 10010.62 - Exceptions to categorical exclusions.

Code of Federal Regulations, 2014 CFR

2014-10-01

... 12988 (Floodplain Management), Executive Order 11990 (Protection of Wetlands), or the Fish and Wildlife... ENVIRONMENTAL POLICY ACT Actions Requiring an EIS and Actions Subject to Categorical Exclusion § 10010.62..., sole or principal drinking water aquifers, prime farmlands, wetlands, floodplains, or ecologically...

43 CFR 10010.62 - Exceptions to categorical exclusions.

Code of Federal Regulations, 2011 CFR

2011-10-01

... 12988 (Floodplain Management), Executive Order 11990 (Protection of Wetlands), or the Fish and Wildlife... ENVIRONMENTAL POLICY ACT Actions Requiring an EIS and Actions Subject to Categorical Exclusion § 10010.62..., sole or principal drinking water aquifers, prime farmlands, wetlands, floodplains, or ecologically...

43 CFR 10010.62 - Exceptions to categorical exclusions.

Code of Federal Regulations, 2013 CFR

2013-10-01

... 12988 (Floodplain Management), Executive Order 11990 (Protection of Wetlands), or the Fish and Wildlife... ENVIRONMENTAL POLICY ACT Actions Requiring an EIS and Actions Subject to Categorical Exclusion § 10010.62..., sole or principal drinking water aquifers, prime farmlands, wetlands, floodplains, or ecologically...

43 CFR 10010.62 - Exceptions to categorical exclusions.

Code of Federal Regulations, 2012 CFR

2012-10-01

... 12988 (Floodplain Management), Executive Order 11990 (Protection of Wetlands), or the Fish and Wildlife... ENVIRONMENTAL POLICY ACT Actions Requiring an EIS and Actions Subject to Categorical Exclusion § 10010.62..., sole or principal drinking water aquifers, prime farmlands, wetlands, floodplains, or ecologically...

Ordination of breeding birds in relation to environmental gradients in three southeastern United States floodplain forests

Treesearch

James S. Wakeley; Michael P. Guilfoyle; Terry J. Antrobus; Richard A. Fischer; Wylie C. Jr. Barrow; Paul B. Hamel

2007-01-01

We used an ordination approach to identify factors important to the organization of breeding bird communities in three floodplains: Cache River, Arkansas (AR), Iatt Creek, Louisiana '(LA), and the Coosawhatchie River, South Carolina (SC), USA.

Delineating floodplain and upload areas for hydrologic models: A comparison of methods

USDA-ARS?s Scientific Manuscript database

A spatially distributed representation of basin hydrology and transport processes in eco-hydrological models facilitates the identification of critical source areas and the placement of management and conservation measures. Floodplains are critical landscape features that differ from neighboring up...

Nutrient Retention in Restored Streams and Floodplains: A Review and Synthesis

EPA Science Inventory

Abstract: Excess nitrogen (N) and phosphorus (P) from human activities have contributed to degradation of coastal waters globally. A growing body of work suggests that hydrologically restoring streams and floodplains in agricultural and urban watersheds has potential to increase...

Establishing oaks in Big River floodplains

Treesearch

Dan Dey; John Kabrick; Michael Gold

2003-01-01

Successful tree establishment is fundamental to implementing agroforestry practices, reforesting bottomland cropfields or regenerating green-tree reservoirs. Planting trees can be problematic in floodplains and riparian areas because of intense competition from herbaceous and woody plants, animal herbivory and browsing, and flooding and saturated soils.

Floodplain ecohydrology: Climatic, anthropogenic, and local physical controls on partitioning of water sources to riparian trees.

PubMed

Singer, Michael Bliss; Sargeant, Christopher I; Piégay, Hervé; Riquier, Jérémie; Wilson, Rob J S; Evans, Cristina M

2014-05-01

Seasonal and annual partitioning of water within river floodplains has important implications for ecohydrologic links between the water cycle and tree growth. Climatic and hydrologic shifts alter water distribution between floodplain storage reservoirs (e.g., vadose, phreatic), affecting water availability to tree roots. Water partitioning is also dependent on the physical conditions that control tree rooting depth (e.g., gravel layers that impede root growth), the sources of contributing water, the rate of water drainage, and water residence times within particular storage reservoirs. We employ instrumental climate records alongside oxygen isotopes within tree rings and regional source waters, as well as topographic data and soil depth measurements, to infer the water sources used over several decades by two co-occurring tree species within a riparian floodplain along the Rhône River in France. We find that water partitioning to riparian trees is influenced by annual (wet versus dry years) and seasonal (spring snowmelt versus spring rainfall) fluctuations in climate. This influence depends strongly on local (tree level) conditions including floodplain surface elevation and subsurface gravel layer elevation. The latter represents the upper limit of the phreatic zone and therefore controls access to shallow groundwater. The difference between them, the thickness of the vadose zone, controls total soil moisture retention capacity. These factors thus modulate the climatic influence on tree ring isotopes. Additionally, we identified growth signatures and tree ring isotope changes associated with recent restoration of minimum streamflows in the Rhône, which made new phreatic water sources available to some trees in otherwise dry years. Water shifts due to climatic fluctuations between floodplain storage reservoirsAnthropogenic changes to hydrology directly impact water available to treesEcohydrologic approaches to integration of hydrology afford new possibilities.

Origin, enzymatic response and fate of dissolved organic matter during flood and non-flood conditions in a river-floodplain system of the Danube (Austria).

PubMed

Sieczko, Anna; Peduzzi, Peter

2014-01-01

Spectroscopic techniques and extracellular enzyme activity measurements were combined with assessments of bacterial secondary production (BSP) to elucidate flood-pulse-linked differences in carbon (C) sources and related microbial processes in a river-floodplain system near Vienna (Austria). Surface connection with the main channel significantly influenced the quantity and quality of dissolved organic matter (DOM) in floodplain backwaters. The highest values of dissolved organic carbon (DOC) and chromophoric DOM (CDOM) were observed during the peak of the flood, when DOC increased from 1.36 to 4.37 mg l -1 and CDOM from 2.94 to 14.32 m -1 . The flood introduced DOC which consisted of more allochthonously-derived, aromatic compounds. Bacterial enzymatic activity, as a proxy to track the response to changes in DOM, indicated elevated utilization of imported allochthonous material. Based on the enzyme measurements, new parameters were calculated: metabolic effort and enzymatic indices (EEA 1 and EEA 2). During connection, bacterial glucosidase and protease activity were dominant, whereas during disconnected phases a switch to lignin degradation (phenol oxidase) occurred. The enzymatic activity analysis revealed that flooding mobilized reactive DOM, which then supported bacterial metabolism. No significant differences in overall BSP between the two phases were detected, indicating that heterogeneous sources of C sufficiently support BSP. The study demonstrates that floods are important for delivering DOM, which, despite its allochthonous origin, is reactive and can be effectively utilized by aquatic bacteria in this river-floodplain systems. The presence of active floodplains, characterized by hydrological connectivity with the main channel, creates the opportunity to process allochthonous DOC. This has potential consequences for carbon flux, enhancing C sequestration and mineralization processes in this river-floodplain system.

Spatial and temporal variability in sedimentation rates associated with cutoff channel infill deposits: Ain River, France

USGS Publications Warehouse

Piégay, H.; Hupp, C.R.; Citterio, A.; Dufour, S.; Moulin, B.; Walling, D.E.

2008-01-01

Floodplain development is associated with lateral accretion along stable channel geometry. Along shifting rivers, the floodplain sedimentation is more complex because of changes in channel position but also cutoff channel presence, which exhibit specific overflow patterns. In this contribution, the spatial and temporal variability of sedimentation rates in cutoff channel infill deposits is related to channel changes of a shifting gravel bed river (Ain River, France). The sedimentation rates estimated from dendrogeomorphic analysis are compared between and within 14 cutoff channel infills. Detailed analyses along a single channel infill are performed to assess changes in the sedimentation rates through time by analyzing activity profiles of the fallout radionuclides 137Cs and unsupported 210Pb. Sedimentation rates are also compared within the channel infills with rates in other plots located in the adjacent floodplain. Sedimentation rates range between 0.65 and 2.4 cm a−1 over a period of 10 to 40 years. The data provide additional information on the role of distance from the bank, overbank flow frequency, and channel geometry in controlling the sedimentation rate. Channel infills, lower than adjacent floodplains, exhibit higher sedimentation rates and convey overbank sediment farther away within the floodplain. Additionally, channel degradation, aggradation, and bank erosion, which reduce or increase the distance between the main channel and the cutoff channel aquatic zone, affect local overbank flow magnitude and frequency and therefore sedimentation rates, thereby creating a complex mosaic of sedimentation zones within the floodplain and along the cutoff channel infills. Last, the dendrogeomorphic and 137Cs approaches are cross validated for estimating the sedimentation rate within a channel infill.

Vegetation, soil, and flooding relationships in a blackwater floodplain forest

USGS Publications Warehouse

Burke, M.K.; King, S.L.; Gartner, D.; Eisenbies, M.H.

2003-01-01

Hydroperiod is considered the primary determinant of plant species distribution in temperate floodplain forests, but most studies have focused on alluvial (sediment-laden) river systems. Few studies have evaluated plant community relationships in blackwater river systems of the South Atlantic Coastal Plain of North America. In this study, we characterized the soils, hydroperiod, and vegetation communities and evaluated relationships between the physical and chemical environment and plant community structure on the floodplain of the Coosawhatchie River, a blackwater river in South Carolina, USA. The soils were similar to previous descriptions of blackwater floodplain soils but had greater soil N and P availability, substantially greater clay content, and lower soil silt content than was previously reported for other blackwater river floodplains. Results of a cluster analysis showed there were five forest communities on the site, and both short-term (4 years) and long-term (50 years) flooding records documented a flooding gradient: water tupelo community > swamp tupelo > laurel oak = overcup oak > mixed oak. The long-term hydrologic record showed that the floodplain has flooded less frequently from 1994 to present than in previous decades. Detrended correspondence analysis of environmental and relative basal area values showed that 27% of the variation in overstory community structure could be explained by the first two axes; however, fitting the species distributions to the DCA axes using Gaussian regression explained 67% of the variation. Axes were correlated with elevation (flooding intensity) and soil characteristics related to rooting volume and cation nutrient availability. Our study suggests that flooding is the major factor affecting community structure, but soil characteristics also may be factors in community structure in blackwater systems. ?? 2003, The Society of Wetland Scientists.

Present-day African analogue of a pre-European Amazonian floodplain fishery shows convergence in cultural niche construction

PubMed Central

McKey, Doyle B.; Durécu, Mélisse; Pouilly, Marc; Béarez, Philippe; Ovando, Alex; Kalebe, Mashuta; Huchzermeyer, Carl F.

2016-01-01

Erickson [Erickson CL (2000) Nature 408 (6809):190–193] interpreted features in seasonal floodplains in Bolivia’s Beni savannas as vestiges of pre-European earthen fish weirs, postulating that they supported a productive, sustainable fishery that warranted cooperation in the construction and maintenance of perennial structures. His inferences were bold, because no close ethnographic analogues were known. A similar present-day Zambian fishery, documented here, appears strikingly convergent. The Zambian fishery supports Erickson’s key inferences about the pre-European fishery: It allows sustained high harvest levels; weir construction and operation require cooperation; and weirs are inherited across generations. However, our comparison suggests that the pre-European system may not have entailed intensive management, as Erickson postulated. The Zambian fishery’s sustainability is based on exploiting an assemblage dominated by species with life histories combining high fecundity, multiple reproductive cycles, and seasonal use of floodplains. As water rises, adults migrate from permanent watercourses into floodplains, through gaps in weirs, to feed and spawn. Juveniles grow and then migrate back to dry-season refuges as water falls. At that moment fishermen set traps in the gaps, harvesting large numbers of fish, mostly juveniles. In nature, most juveniles die during the first dry season, so that their harvest just before migration has limited impact on future populations, facilitating sustainability and the adoption of a fishery based on inherited perennial structures. South American floodplain fishes with similar life histories were the likely targets of the pre-European fishery. Convergence in floodplain fish strategies in these two regions in turn drove convergence in cultural niche construction. PMID:27980030

Complementary effects of surface water and groundwater on soil moisture dynamics in a degraded coastal floodplain forest

NASA Astrophysics Data System (ADS)

Kaplan, D.; Muñoz-Carpena, R.

2011-02-01

SummaryRestoration of degraded floodplain forests requires a robust understanding of surface water, groundwater, and vadose zone hydrology. Soil moisture is of particular importance for seed germination and seedling survival, but is difficult to monitor and often overlooked in wetland restoration studies. This research hypothesizes that the complex effects of surface water and shallow groundwater on the soil moisture dynamics of floodplain wetlands are spatially complementary. To test this hypothesis, 31 long-term (4-year) hydrological time series were collected in the floodplain of the Loxahatchee River (Florida, USA), where watershed modifications have led to reduced freshwater flow, altered hydroperiod and salinity, and a degraded ecosystem. Dynamic factor analysis (DFA), a time series dimension reduction technique, was applied to model temporal and spatial variation in 12 soil moisture time series as linear combinations of common trends (representing shared, but unexplained, variability) and explanatory variables (selected from 19 additional candidate hydrological time series). The resulting dynamic factor models yielded good predictions of observed soil moisture series (overall coefficient of efficiency = 0.90) by identifying surface water elevation, groundwater elevation, and net recharge (cumulative rainfall-cumulative evapotranspiration) as important explanatory variables. Strong and complementary linear relationships were found between floodplain elevation and surface water effects (slope = 0.72, R2 = 0.86, p < 0.001), and between elevation and groundwater effects (slope = -0.71, R2 = 0.71, p = 0.001), while the effect of net recharge was homogenous across the experimental transect (slope = 0.03, R2 = 0.05, p = 0.242). This study provides a quantitative insight into the spatial structure of groundwater and surface water effects on soil moisture that will be useful for refining monitoring plans and developing ecosystem restoration and management scenarios in degraded coastal floodplains.

A Three-Year Study of Ichyoplankton in Coastal Plains Reaches of the Savannah River Site and its Tributaries

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

Martin, D.

2007-03-05

Altering flow regimes of rivers has large effects on native floras and faunas because native species are adapted to the natural flow regime, many species require lateral connectivity with floodplain habitat for feeding or spawning, and the change in regime often makes it possible for invasive species to replace natives (Bunn & Arthington 2002). Floodplain backwaters, both permanent and temporary, are nursery areas for age 0+ fish and stable isotope studies indicate that much of the productivity that supports fish larvae is autochthonous to these habitats (Herwig et al. 2004). Limiting access by fish to floodplain habitat for feeding, spawningmore » and nursery habitat is one of the problems noted with dams that regulate flow in rivers and is considered to be important as an argument to remove dams and other flow regulating structures from rivers (Shuman 1995; Bednarek 2001). While there have been a number of studies in the literature about the use of floodplain habitat for fish reproduction (Copp 1989; Killgore & Baker 1996; Humphries, et al. 1999; Humphries and Lake 2000; Crain et al. 2004; King 2004) there have been only a few studies that examined this aspect of stream ecology in more than a cursory way. The study reported here was originally designed to determine whether the Department of Energy's (DOE) Savannah River Site was having a negative effect on fish reproduction in the Savannah River but its experimental design allowed examination of the interactions between the river, the floodplain and the tributaries entering the Savannah River across this floodplain. This study is larger in length of river covered than most in the literature and because of its landscape scale may be in important indicator of areas where further study is required.« less

Living with floods - Household perception and satellite observations in the Barotse floodplain, Zambia

NASA Astrophysics Data System (ADS)

Cai, Xueliang; Haile, Alemseged Tamiru; Magidi, James; Mapedza, Everisto; Nhamo, Luxon

2017-08-01

The Barotse Floodplain, a designated Ramsar site, is home to thousands of indigenous people along with an extensive wetland ecosystem and food production system. Increasingly it is also a popular tourist destination with its annual Kuomboka festival which celebrates the relocation of the king and the Lozi people to higher ground before the onset of the flood season. This paper presents an integrated approach which cross validates and combines the floodplain residents' perceptions about recent floods with information on flood inundation levels derived from satellite observations. Local residents' surveys were conducted to assess farmers' perception on the flooding patterns and the impact on their livelihoods. Further, a series of flood inundation maps from 1989 to 2014 generated from remotely sensed Landsat imagery were used to assess the recent patterns of floods. Results show that the floodplain has a population of 33 thousand living in 10,849 small permeant or temporary buildings with a total cropland area of 4976 ha. The floodplain hydrology and flooding patterns have changed, confirmed by both surveys and satellite image analysis, due to catchment development and changing climate. The average annual inundated areas have increased from about 316 thousand ha in 1989-1998 to 488 thousand ha in 2005-2014. As a result the inundated cropland and houses increased from 9% to 6% in 1989 to 73% and 47% in 2014, respectively. The timing of the floods has also changed with both delaying and early onset happening more frequently. These changes cause increasing difficulties in flood forecast and preparation using indigenous knowledge, therefore creating greater damages to crops, livestock, and houses. Current floodplain management system is inadequate and new interventions are needed to help manage the floods at a systematic manner.

Floodplain ecohydrology: Climatic, anthropogenic, and local physical controls on partitioning of water sources to riparian trees

PubMed Central

Singer, Michael Bliss; Sargeant, Christopher I; Piégay, Hervé; Riquier, Jérémie; Wilson, Rob J S; Evans, Cristina M

2014-01-01

Seasonal and annual partitioning of water within river floodplains has important implications for ecohydrologic links between the water cycle and tree growth. Climatic and hydrologic shifts alter water distribution between floodplain storage reservoirs (e.g., vadose, phreatic), affecting water availability to tree roots. Water partitioning is also dependent on the physical conditions that control tree rooting depth (e.g., gravel layers that impede root growth), the sources of contributing water, the rate of water drainage, and water residence times within particular storage reservoirs. We employ instrumental climate records alongside oxygen isotopes within tree rings and regional source waters, as well as topographic data and soil depth measurements, to infer the water sources used over several decades by two co-occurring tree species within a riparian floodplain along the Rhône River in France. We find that water partitioning to riparian trees is influenced by annual (wet versus dry years) and seasonal (spring snowmelt versus spring rainfall) fluctuations in climate. This influence depends strongly on local (tree level) conditions including floodplain surface elevation and subsurface gravel layer elevation. The latter represents the upper limit of the phreatic zone and therefore controls access to shallow groundwater. The difference between them, the thickness of the vadose zone, controls total soil moisture retention capacity. These factors thus modulate the climatic influence on tree ring isotopes. Additionally, we identified growth signatures and tree ring isotope changes associated with recent restoration of minimum streamflows in the Rhône, which made new phreatic water sources available to some trees in otherwise dry years. Key Points Water shifts due to climatic fluctuations between floodplain storage reservoirs Anthropogenic changes to hydrology directly impact water available to trees Ecohydrologic approaches to integration of hydrology afford new possibilities PMID:25506099

Topsoil structure stability in a restored floodplain: Impacts of fluctuating water levels, soil parameters and ecosystem engineers.

PubMed

Schomburg, A; Schilling, O S; Guenat, C; Schirmer, M; Le Bayon, R C; Brunner, P

2018-10-15

Ecosystem services provided by floodplains are strongly controlled by the structural stability of soils. The development of a stable structure in floodplain soils is affected by a complex and poorly understood interplay of hydrological, physico-chemical and biological processes. This paper aims at analysing relations between fluctuating groundwater levels, soil physico-chemical and biological parameters on soil structure stability in a restored floodplain. Water level fluctuations in the soil are modelled using a numerical surface-water-groundwater flow model and correlated to soil physico-chemical parameters and abundances of plants and earthworms. Causal relations and multiple interactions between the investigated parameters are tested through structural equation modelling (SEM). Fluctuating water levels in the soil did not directly affect the topsoil structure stability, but indirectly through affecting plant roots and soil parameters that in turn determine topsoil structure stability. These relations remain significant for mean annual days of complete and partial (>25%) water saturation. Ecosystem functioning of a restored floodplain might already be affected by the fluctuation of groundwater levels alone, and not only through complete flooding by surface water during a flood period. Surprisingly, abundances of earthworms did not show any relation to other variables in the SEM. These findings emphasise that earthworms have efficiently adapted to periodic stress and harsh environmental conditions. Variability of the topsoil structure stability is thus stronger driven by the influence of fluctuating water levels on plants than by the abundance of earthworms. This knowledge about the functional network of soil engineering organisms, soil parameters and fluctuating water levels and how they affect soil structural stability is of fundamental importance to define management strategies of near-natural or restored floodplains in the future. Copyright © 2018 Elsevier B.V. All rights reserved.

Changes in soil organic carbon fractions following remediation of a degraded coastal floodplain wetland

NASA Astrophysics Data System (ADS)

Wong, Vanessa; McNaughton, Caitlyn; Pearson, Amy

2017-04-01

Coastal floodplain soils and wetland sediments can store large amounts of soil organic carbon (SOC). These environments are also commonly underlain by sulfidic sediments which can oxidise, largely due to drainage of floodplains to decrease water levels, to form coastal acid sulfate soils (CASS). Following oxidation, pH of both soil and water decrease, and acidity and mobilisation of trace metals increases to adversely affect vegetation and adjacent aquatic ecosystems. In extreme cases, vegetation death occurs resulting in the formation of scalds, which are large bare patches. Remediation of these degraded coastal soils generally involves neutralisation of acidity via application of lime and the re-introduction of anoxic conditions by raising water levels. Our understanding of the geochemical changes which occur as a result of remediation is relatively well established. However, SOC stocks and fractions have not been quantified in these coastal floodplain environments. We studied the changes in soil geochemistry and SOC stocks and fractions three years after remediation of a degraded and scalded coastal floodplain. Remediation treatments included raising water levels, and addition of either lime (LO) or lime and mulch (LM) relative to a control (C) site. We found SOC concentrations in the remediated sites (LO and LM) were more than double than that found at site C, reflected in the higher SOC stocks to a depth of 1.6 m. The particulate organic C fraction was higher at sites LO and LM due to increased vegetation and biomass inputs, compared to site C. Therefore, coastal floodplains and wetlands are a large store of SOC and can potentially increase SOC following remediation due to i) reduced decomposition rates with higher water levels and waterlogging, and ii) high C inputs due to rapid revegetation of scalded areas and high rates of biomass production.

Long-term changes in river-floodplain dynamics: implications for salmonid habitat in the Interior Columbia Basin, USA.

PubMed

Tomlinson, Matthew J; Gergel, Sarah E; Beechie, Timothy J; McClure, Michelle M

2011-07-01

Rivers and their associated floodplains are among the world's most highly altered ecosystems, resulting in billions of dollars in restoration expenditures. Successful restoration of these systems requires information at multiple spatial scales (from localized reaches to broader-scale watersheds), as well as information spanning long time frames. Here, we develop a suite of historical landscape indicators of riverine status, primarily from the perspective of salmonid management, using a case study in the Interior Columbia Basin, Washington, USA. We use a combination of historical and modern aerial photography to quantify changes in land cover and reach type, as well as potential fish habitat within channel and off-channel floodplain areas. As of 1949, 55% of the Wenatchee River floodplain had been converted to agriculture. By 2006, 62% had been modified by anthropogenic development, of which 20% was due to urban expansion. The historical percentage of agricultural land in the watershed and the contemporary percentage of urban area surpass thresholds in land cover associated with deleterious impacts on river systems. In addition, the abundance of reach types associated with the highest quality salmonid habitat (island braided and meandering reaches) has declined due to conversion to straight reach types. The area occupied by fish habitats associated with channel migration (slow/stagnant channels and dry channels) has declined approximately 25-30%. Along highly modified rivers, these habitats have also become increasingly fragmented. Caveats related to visual quality and seasonal timing of historical photographs were important considerations in the interpretation of changes witnessed for headwater island braided systems, as well as for floodplain ponds. Development of rigorous, long-term, multi-scale monitoring techniques is necessary to guide the management and restoration of river-floodplain systems for the diversity of ecosystem services they provide.

Channelization and floodplain forests: Impacts of accelerated sedimentation and valley plug formation on floodplain forests of the Middle Fork Forked Deer River, Tennessee, USA

USGS Publications Warehouse

Oswalt, S.N.; King, S.L.

2005-01-01

We evaluated the severe degradation of floodplain habitats resulting from channelization and concomitant excessive coarse sedimentation on the Middle Fork Forked Deer River in west Tennessee from 2000 to 2003. Land use practices have resulted in excessive sediment in the tributaries and river system eventually resulting in sand deposition on the floodplain, increased overbank flooding, a rise in the groundwater table, and ponding of upstream timber. Our objectives were to: (1) determine the composition of floodplain vegetation communities along the degraded river reach, (2) to isolate relationships among these communities, geomorphic features, and environmental variables and (3) evaluate successional changes based on current stand conditions. Vegetation communities were not specifically associated with predefined geomorphic features; nevertheless, hydrologic and geomorphic processes as a result of channelization have clearly affected vegetation communities. The presence of valley plugs and continued degradation of upstream reaches and tributaries on the impacted study reach has arrested recovery of floodplain plant communities. Historically common species like Liquidambar styraciflua L. and Quercus spp. L. were not important, with importance values (IV) less than 1, and occurred in less than 20% of forested plots, while Acer rubrum L., a disturbance-tolerant species, was the most important species on the site (IV = 78.1) and occurred in 87% of forested plots. The results of this study also indicate that channelization impacts on the Middle Fork Forked Deer River are more temporally and spatially complex than previously described for other river systems. Rehabilitation of this system necessitates a long-term, landscape-scale solution that addresses watershed rehabilitation in a spatially and temporally hierarchical manner. ?? 2005 Elsevier B.V. All rights reserved.

Towards understanding the dynamic behaviour of floodplains as human-water systems

NASA Astrophysics Data System (ADS)

Di Baldassarre, G.; Kooy, M.; Kemerink, J. S.; Brandimarte, L.

2013-03-01

This paper offers a conceptual approach to explore the complex dynamics of floodplains as fully coupled human-water systems. A number of hydrologists have recently investigated the impact of human activities (such as flood control measures, land-use changes, and settlement patterns) on the frequency and severity of floods. Meanwhile, social scientists have shown how interactions between society and waters in floodplain areas, including the frequency and severity of floods, have an impact on the ways in which social relations unfold (in terms of governance processes, policies, and institutions) and societies are organised (spatially, politically, and socially). However, we argue that the interactions and associated feedback mechanisms between hydrological and social processes remain largely unexplored and poorly understood. Thus, there is a need to better understand how the institutions and governance processes interact with hydrological processes in floodplains to influence the frequency and severity of floods, while (in turn) hydrological processes co-constitute the social realm and make a difference for how social relations unfold to shape governance processes and institutions. Our research goal, therefore, is not in identifying one or the other side of the cycle (hydrological or social), but in explaining the relationship between them: how, when, where, and why they interact, and to what result for both social relations and hydrological processes? We argue that long time series of hydrological and social data, along with remote sensing data, can be used to observe floodplain dynamics from unconventional approaches, and understand the complex interactions between water and human systems taking place in floodplain areas, across scales and levels of human impacts, and within different hydro-climatic conditions, socio-cultural settings, and modes of governance.

Towards understanding the dynamic behaviour of floodplains as human-water systems

NASA Astrophysics Data System (ADS)

Di Baldassarre, G.; Kooy, M.; Kemerink, J. S.; Brandimarte, L.

2013-08-01

This paper offers a conceptual approach to explore the complex dynamics of floodplains as fully coupled human-water systems. A number of hydrologists have recently investigated the impact of human activities (such as flood control measures, land-use changes, and settlement patterns) on the frequency and severity of floods. Meanwhile, social scientists have shown how interactions between society and waters in deltas and floodplain areas, including the frequency and severity of floods, have an impact on the ways in which social relations unfold (in terms of governance processes, policies, and institutions) and societies are organised (spatially, politically, and socially). However, we argue that the interactions and associated feedback mechanisms between hydrological and social processes remain largely unexplored and poorly understood. Thus, there is a need to better understand how the institutions and governance processes interact with hydrological processes in deltas and floodplains to influence the frequency and severity of floods, while (in turn) hydrological processes co-constitute the social realm and make a difference for how social relations unfold to shape governance processes and institutions. Our research goal, therefore, is not in identifying one or the other side of the cycle (hydrological or social), but in explaining the relationship between them: how, when, where, and why they interact, and to what result for both social relations and hydrological processes? We argue that long time series of hydrological and social data, along with remote sensing data, can be used to observe floodplain dynamics from unconventional approaches, and understand the complex interactions between water and human systems taking place in floodplain areas, across scales and levels of human impacts, and within different hydro-climatic conditions, socio-cultural settings, and modes of governance.

Riparian forest communities of the lower Kaskaskia River bottoms

Treesearch

Susan P. Romano; James J. Zaczek; Karl W. J. Williard; Sara Baer; Andrew D. Carver; Jean C. Mangun

2003-01-01

Hydrologic alterations due to dam construction may have altered the floodplain ecology of the Lower Kaskaskia River. Seven forest communities within the study site were identified. Floodplain communities include Acer negundo-Celtis occidentalis-Acer saccharinum, Acer saccharinum-Acer negundo, and Celtis occidentalis-Ulmus americana...

10 CFR 1022.3 - Policy.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 4 2010-01-01 2010-01-01 false Policy. 1022.3 Section 1022.3 Energy DEPARTMENT OF ENERGY (GENERAL PROVISIONS) COMPLIANCE WITH FLOODPLAIN AND WETLAND ENVIRONMENTAL REVIEW REQUIREMENTS General § 1022.3 Policy. DOE shall exercise leadership and take action to: (a) Incorporate floodplain management...

10 CFR 1022.21 - Property management.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 10 Energy 4 2012-01-01 2012-01-01 false Property management. 1022.21 Section 1022.21 Energy DEPARTMENT OF ENERGY (GENERAL PROVISIONS) COMPLIANCE WITH FLOODPLAIN AND WETLAND ENVIRONMENTAL REVIEW REQUIREMENTS Other Requirements § 1022.21 Property management. (a) If property in a floodplain or wetland is...

10 CFR 1022.21 - Property management.

Code of Federal Regulations, 2014 CFR

2014-01-01

... 10 Energy 4 2014-01-01 2014-01-01 false Property management. 1022.21 Section 1022.21 Energy DEPARTMENT OF ENERGY (GENERAL PROVISIONS) COMPLIANCE WITH FLOODPLAIN AND WETLAND ENVIRONMENTAL REVIEW REQUIREMENTS Other Requirements § 1022.21 Property management. (a) If property in a floodplain or wetland is...

10 CFR 1022.21 - Property management.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 10 Energy 4 2013-01-01 2013-01-01 false Property management. 1022.21 Section 1022.21 Energy DEPARTMENT OF ENERGY (GENERAL PROVISIONS) COMPLIANCE WITH FLOODPLAIN AND WETLAND ENVIRONMENTAL REVIEW REQUIREMENTS Other Requirements § 1022.21 Property management. (a) If property in a floodplain or wetland is...

10 CFR 1022.21 - Property management.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 4 2011-01-01 2011-01-01 false Property management. 1022.21 Section 1022.21 Energy DEPARTMENT OF ENERGY (GENERAL PROVISIONS) COMPLIANCE WITH FLOODPLAIN AND WETLAND ENVIRONMENTAL REVIEW REQUIREMENTS Other Requirements § 1022.21 Property management. (a) If property in a floodplain or wetland is...

Insights from depth-averaged numerical simulation of flow at bridge abutments in compound channels.

DOT National Transportation Integrated Search

2011-07-01

Two-dimensional, depth-averaged flow models are used to study the distribution of flow around spill-through abutments situated on floodplains in compound channels and rectangular channels (flow on very wide floodplains may be treated as rectangular c...

39 CFR 776.4 - Scope.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 39 Postal Service 1 2010-07-01 2010-07-01 false Scope. 776.4 Section 776.4 Postal Service UNITED STATES POSTAL SERVICE ENVIRONMENTAL REGULATIONS FLOODPLAIN AND WETLAND PROCEDURES Floodplain Management § 776.4 Scope. (a) The regulations in this subpart are applicable to the following proposed postal...

10 CFR 1022.3 - Policy.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 10 Energy 4 2011-01-01 2011-01-01 false Policy. 1022.3 Section 1022.3 Energy DEPARTMENT OF ENERGY (GENERAL PROVISIONS) COMPLIANCE WITH FLOODPLAIN AND WETLAND ENVIRONMENTAL REVIEW REQUIREMENTS General § 1022.3 Policy. DOE shall exercise leadership and take action to: (a) Incorporate floodplain management...

Tree establishment in floodplain agroforestry practices

Treesearch

Daniel C. Dey; John M. Kabrick; Michael A. Gold

2004-01-01

The benefits of soil mounding, a cover crop, and various nursery stock types were evaluated for establishing pin and swamp white oaks in floodplain crop fields. The two stock types were 1-0 bareroot and large (3- and 5-gallon) container seedlings grown by the RPMTM method.

39 CFR 776.1 - Purpose and policy.

Code of Federal Regulations, 2011 CFR

2011-07-01

... Orders 11990, Protection of Wetlands, and 11988, Floodplain Management, and are adopted pursuant to the Postal Reorganization Act, as the Postal Service does not meet the definition of the term “agency” used... Service UNITED STATES POSTAL SERVICE ENVIRONMENTAL REGULATIONS FLOODPLAIN AND WETLAND PROCEDURES General...

39 CFR 776.1 - Purpose and policy.

Code of Federal Regulations, 2014 CFR

2014-07-01

... Orders 11990, Protection of Wetlands, and 11988, Floodplain Management, and are adopted pursuant to the Postal Reorganization Act, as the Postal Service does not meet the definition of the term “agency” used... Service UNITED STATES POSTAL SERVICE ENVIRONMENTAL REGULATIONS FLOODPLAIN AND WETLAND PROCEDURES General...

39 CFR 776.1 - Purpose and policy.

Code of Federal Regulations, 2013 CFR

2013-07-01

... Orders 11990, Protection of Wetlands, and 11988, Floodplain Management, and are adopted pursuant to the Postal Reorganization Act, as the Postal Service does not meet the definition of the term “agency” used... Service UNITED STATES POSTAL SERVICE ENVIRONMENTAL REGULATIONS FLOODPLAIN AND WETLAND PROCEDURES General...

39 CFR 776.1 - Purpose and policy.

Code of Federal Regulations, 2012 CFR

2012-07-01

... Orders 11990, Protection of Wetlands, and 11988, Floodplain Management, and are adopted pursuant to the Postal Reorganization Act, as the Postal Service does not meet the definition of the term “agency” used... Service UNITED STATES POSTAL SERVICE ENVIRONMENTAL REGULATIONS FLOODPLAIN AND WETLAND PROCEDURES General...

Hyporheic flow patterns in relation to large river floodplain attributes

EPA Science Inventory

Field-calibrated models of hyporheic flow have emphasized low-order headwater systems. In many cases, however, hyporheic flow in large lowland river floodplains may be an important contributor to ecosystem services such as maintenance of water quality and habitat. In this study, ...

39 CFR 776.6 - Design requirements for construction.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 39 Postal Service 1 2010-07-01 2010-07-01 false Design requirements for construction. 776.6 Section 776.6 Postal Service UNITED STATES POSTAL SERVICE ENVIRONMENTAL REGULATIONS FLOODPLAIN AND WETLAND PROCEDURES Floodplain Management § 776.6 Design requirements for construction. If structures impact, are...

CLASSIFICATION, PROTECTION, AND MONITORING OF NONTIDAL FLOODPLAIN FOREST COMMUNITIES

EPA Science Inventory

New Jersey,s floodplain forests (FFs) contain 57 rare plant species, 25 of which are State Endangered. The acreage of FF has been substantially reduced over the past 200 years, and upland buffers have also been diminished. Threats to FF communities include stream degradation, ...

10 CFR 1022.21 - Property management.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 10 Energy 4 2010-01-01 2010-01-01 false Property management. 1022.21 Section 1022.21 Energy DEPARTMENT OF ENERGY (GENERAL PROVISIONS) COMPLIANCE WITH FLOODPLAIN AND WETLAND ENVIRONMENTAL REVIEW REQUIREMENTS Other Requirements § 1022.21 Property management. (a) If property in a floodplain or wetland is...

Cooling Along Hyporheic Pathlines in a Large River Riparian Zone

EPA Science Inventory

Floodplains can contribute to hyporheic cooling and moderation of temperature for rivers, but extent and magnitude are dependent on ground water hydrology. Here we illustrate the controls and dynamics of hyporheic cooling in the ground water of a large river floodplain with field...

Hyporheic flow patterns in relation to large river floodplain attributes Journal

EPA Science Inventory

Field-calibrated models of hyporheic flow have emphasized low-order headwater systems. In many cases, however, hyporheic flow in large lowland river floodplains may be an important contributor to ecosystem services such as maintenance of water quality and habitat. In this study, ...

44 CFR 9.15 - Planning programs affecting land use.

Code of Federal Regulations, 2010 CFR

2010-10-01

... 44 Emergency Management and Assistance 1 2010-10-01 2010-10-01 false Planning programs affecting..., DEPARTMENT OF HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.15 Planning... flood hazards and floodplain management and wetlands protection; and (b) Prescribes planning procedures...

Process-based principles for restoring river ecosystems

Treesearch

Timothy J. Beechie; David A. Sear; Julian D. Olden; George R. Pess; John M. Buffington; Hamish Moir; Philip Roni; Michael M. Pollock

2010-01-01

Process-based restoration aims to reestablish normative rates and magnitudes of physical, chemical, and biological processes that sustain river and floodplain ecosystems. Ecosystem conditions at any site are governed by hierarchical regional, watershed, and reach-scale processes controlling hydrologic and sediment regimes; floodplain and aquatic habitat...

Vertical distribution of 137Cs in alluvial soils of the Lokna River floodplain (Tula oblast) long after the Chernobyl accident and its simulation

NASA Astrophysics Data System (ADS)

Mamikhin, S. V.; Golosov, V. N.; Paramonova, T. A.; Shamshurina, E. N.; Ivanov, M. M.

2016-12-01

Profiles of vertical 137Cs distribution in alluvial meadow soils on the low and medium levels of the Lokna River floodplain (central part of the Plavsk radioactive spot in Tula oblast) 28 years after the Chernobyl fallout have been studied. A significant increase in the 137Cs pool is revealed on the low floodplain areas compared to the soils of interfluves due to the accumulation of alluvium, which hampers the reduction of the total radionuclide pool in alluvial soils because of radioactive decay. The rate of alluvium accumulation in the soil on the medium floodplain level is lower by three times on average. An imitation prognostic model has been developed, which considers the flooding and climatic conditions in the region under study. Numerical experiments have quantitatively confirmed the deciding role of low-mobile forms in the migration of maximum 137Cs content along the soil profile in the absence of manifested erosion-accumulation processes.

Characterizing the impacts of the 2006 New Year's flood in the Laguna de Santa Rosa floodplain, Sonoma County, CA

NASA Astrophysics Data System (ADS)

Flint, L. E.; Curtis, J. A.; Flint, A. L.

2006-12-01

The Laguna de Santa Rosa (Laguna), the largest tributary to the Russian River located in Sonoma County, California, occupies a relatively flat low-lying area west of the Santa Rosa Plain. From December 12, 2005 to January 6, 2006 the Laguna experienced heavy flooding, with peak flows on New Year's Day of over 185 m3/s, at a location that experiences median flows of less than 14 m3/s. The objectives of this study were to (1) analyze precipitation intensities and amounts for the region to establish the conditions under which flooding occurred, (2) measure and map inundation areas and floodplain sediment deposition, and (3) compare field data with a GIS sediment deposition potential map. Spatial variations in intensities and total volumes of precipitation correlate well with evidence of local flooding throughout the region, particularly in the mountains to the east and southeast of Santa Rosa. Total precipitation for the month of December was 200 percent of normal, and maximum hourly intensities reached 20 mm/hour during the storm. High water marks and floodplain deposition sites were mapped using kinematic GPS surveying with post-processed differential correction, and sediment deposition was measured. The surveyed data were superimposed on an available two-foot-interval contour map to create an inundation map and a GIS point coverage of sediment deposition. Landscape attributes relevant to floodplain sedimentation were assessed and a sediment deposition potential map was created at the 30-m scale using a matrix of landscape characteristics that included: land use; roughness (influenced by vegetation type and density); channel and hillslope sediment sources (influenced by soils, geology, and cutbank erosion); slope and topography; and geomorphic terrain type. A calculation of sediment deposition potential was developed within a GIS that accounts for all contributing factors and illustrates that floodplain deposition is dominated by localized sedimentation, reflecting the importance of sediment point sources, rather than extensive sedimentation throughout the floodplain. The data collected in this study will be used to constrain model simulations of recurrence-interval floods and provide information on patterns of hydrology and sedimentation for extreme events that will help refine conceptual models of floodplain processes.

Strategic Floodplain Reconnection Along the Lower Tisza and Lower Illinois Rivers: Identifying Opportunities, Tradeoffs, and Limitations

NASA Astrophysics Data System (ADS)

Guida, R.; Remo, J. W.; Secchi, S.; Swanson, T.; Kiss, T.

2015-12-01

During the late 19th and into the 20th Centuries, the Tisza and Illinois Rivers were highly altered through the construction of levees and dams to reclaim their floodplain-wetland systems for agriculture and to facilitate navigation. In recent decades, flood levels have continued to rise due to aggradation on the confined floodplains reducing flood-conveyance capacity. As a result, "Room for the River" proposals have gained more prominence. Our overarching hypothesis is that strategically reconnecting these rivers to their floodplains will reduce flood levels and increase ecological habitat while limiting socioeconomic impacts. In this study, we assessed several reconnection scenarios, including levee setbacks and removals, for the Lower Tisza River (LTR; Hungary) and the Lower Illinois River (LIR; Illinois, USA). To model water-surface elevations (WSELs) for the 5- through 500-year flood events, we employed HEC-RAS (1D) and SOBEK (1D/2D) hydraulic models. To determine socioeconomic tradeoffs using these modeled WSELs, we developed a corresponding suite of expected annual damages (EADs) using FEMA's Hazus-MH flood-loss modeling software for buildings and integrated geospatial and soil productivity indices to estimate agricultural losses. To assess ecosystem benefits of reconnection along the LTR, we used historic wetland extent as a proxy for increasing needed floodplain habitats. For the LIR, we performed habitat screening using Land Capability Potential Index and other assessment tools to estimate potential ecosystem benefits. Results indicate that levee removal and/or setbacks may reduce flood heights up to 1.6 m along the LTR and over 1.0 m along the LIR. While urban areas have the highest EADs, several lower-production agricultural areas show potential for reducing flood heights while minimizing damages. Strategic-floodplain reconnection benefits along the LTR and LIR include over half of historically-significant wetlands being reconnected and the creation of new habitat patches for threatened species within existing levee districts. While there are multiple benefits that may outweigh the costs of strategic floodplain reconnection, there are also limits to its effectiveness which are constrained by both the political and physical conditions in each basin.

Floodplain influence on carbon speciation and fluxes from the lower Pearl River, Mississippi

NASA Astrophysics Data System (ADS)

Cai, Yihua; Shim, Moo-Joon; Guo, Laodong; Shiller, Alan

2016-08-01

To investigate the floodplain influence on carbon speciation and export to the northern Gulf of Mexico, water samples were collected monthly from two sites in the East Pearl River (EPR) basin during 2006-2008. Additionally, four spatial surveys in the river basin between those two sites were also conducted. Compared with the upstream sampling site at Bogalusa, MS, dissolved inorganic carbon (DIC) and particulate organic carbon (POC) concentrations were 36% and 55% lower, respectively, and dissolved organic carbon (DOC) concentration was 49% higher at the downstream Stennis Space Center (SSC) site. In addition, the bulk DOC pool at SSC had a higher colloidal fraction than at Bogalusa (75% vs. 68%). Detailed spatial surveys revealed the differences between the upstream and downstream stations resulted both from input from Hobolochitto Creek, a tributary of the EPR, and from influence of the swamp-rich floodplain. The contributions from Hobolochitto Creek to the carbon pool in the EPR basin were lowest during a high flow event and reached a maximum during the dry season. Meanwhile, the floodplain in the EPR basin acted as a significant sink for DOC, POC and particulate nitrogen during summer and for suspended sediment during a high flow event. However, the floodplain was converted into a source of suspended sediment, DOC, and POC to the EPR during winter, revealing a dynamic nature and seasonality in the floodplain influence. Consistent with its dominant forest coverage, abundant wetlands along the river corridor, and mild anthropogenic disturbance, the Pearl River basin above Bogalusa generally had higher yields of DOC and POC (1903 and 1386 kg-C km-2 yr-1, respectively), but a lower yield of DIC (2126 kg-C km-2 yr-1) compared to other North American rivers. An estimation based on a mass balance approach suggests the interactions between floodplain and the main river stem could reduce the annual DIC and POC export fluxes from downstream of the EPR by 24% and 40%, respectively, but enhance the annual riverine DOC export by 25%. Similar scenarios likely occur in other wetland-rich coastal rivers and are capable of significantly altering the current estimation of riverine carbon export.

Modeling stream-groundwater interactions and associated groundwater salinization in an urban floodplain

NASA Astrophysics Data System (ADS)

Ledford, S. H.; Lautz, L.

2014-12-01

The salinization of freshwater in the Northeastern United States from road salt application is well documented by the observed long-term increases in chloride concentrations in groundwater over the last fifty years. However, the processes controlling exchange of chloride between surface water and groundwater have not been fully investigated, particularly in urban streams where stream-groundwater interactions can be reduced due to bank armoring and channelization. Our research builds on previous findings that showed the potential for an urban riparian floodplain to buffer seasonal changes in chloride concentrations in an urban stream, resulting in smaller annual ranges of chloride in areas with intact riparian floodplains. A reach of Meadowbrook Creek, in Syracuse, New York, that is disconnected from the groundwater had large seasonal shifts in chloride concentration, varying from 2173 mg/L Cl- in the winter to 161.2 mg/L Cl- in the summer. This is in contrast to a downstream reach of the stream that receives groundwater discharge from a riparian floodplain, where chloride concentrations ranged from 657.0 mg/L in the winter to 252.0 mg/L in the summer. We originally hypothesized that winter snowmelt events caused overbank flooding of saline surface water, which recharged the floodplain groundwater, causing salinization. This saline water was then slowly discharged as baseflow throughout the year and was replaced with freshwater overbank events in the summer. However, a three dimensional model of the floodplain created using Visual MODFLOW indicates that surface water-groundwater interactions, such as hyporheic exchange, may have a greater control on winter salt input than overbank events, while summer flooding recharges the aquifer with freshwater. The model was compared to riparian aquifer samples collected from May 2013 until June 2014 to qualitatively study the impact of different types of surface water-groundwater interactions (e.g. groundwater recharge and discharge, hyporheic interaction) on salt storage and to identify the mechanisms by which urban riparian floodplains buffer seasonal variability of stream chloride concentrations in urban systems impacted by road salt.

Reduced Complexity Modelling of Urban Floodplain Inundation

NASA Astrophysics Data System (ADS)

McMillan, H. K.; Brasington, J.; Mihir, M.

2004-12-01

Significant recent advances in floodplain inundation modelling have been achieved by directly coupling 1d channel hydraulic models with a raster storage cell approximation for floodplain flows. The strengths of this reduced-complexity model structure derive from its explicit dependence on a digital elevation model (DEM) to parameterize flows through riparian areas, providing a computationally efficient algorithm to model heterogeneous floodplains. Previous applications of this framework have generally used mid-range grid scales (101-102 m), showing the capacity of the models to simulate long reaches (103-104 m). However, the increasing availability of precision DEMs derived from airborne laser altimetry (LIDAR) enables their use at very high spatial resolutions (100-101 m). This spatial scale offers the opportunity to incorporate the complexity of the built environment directly within the floodplain DEM and simulate urban flooding. This poster describes a series of experiments designed to explore model functionality at these reduced scales. Important questions are considered, raised by this new approach, about the reliability and representation of the floodplain topography and built environment, and the resultant sensitivity of inundation forecasts. The experiments apply a raster floodplain model to reconstruct a 1:100 year flood event on the River Granta in eastern England, which flooded 72 properties in the town of Linton in October 2001. The simulations use a nested-scale model to maintain efficiency. A 2km by 4km urban zone is represented by a high-resolution DEM derived from single-pulse LIDAR data supplied by the UK Environment Agency, together with surveyed data and aerial photography. Novel methods of processing the raw data to provide the individual structure detail required are investigated and compared. This is then embedded within a lower-resolution model application at the reach scale which provides boundary conditions based on recorded flood stage. The high resolution predictions on a scale commensurate with urban structures make possible a multi-criteria validation which combines verification of reach-scale characteristics such as downstream flow and inundation extent with internal validation of flood depth at individual sites.

Fluvial wood function downstream of beaver versus man-made dams in headwater streams in Massachusetts, USA

NASA Astrophysics Data System (ADS)

David, G. C.; DeVito, L. F.; Munz, K. T.; Lisius, G.

2014-12-01

Fluvial wood is an essential component of stream ecosystems by providing habitat, increasing accumulation of organic matter, and increasing the processing of nutrients and other materials. However, years of channel alterations in Massachusetts have resulted in low wood loads despite the afforestation that has occurred since the early 1900s. Streams have also been impacted by a large density of dams, built during industrialization, and reduction of the beaver population. Beavers were reintroduced to Massachusetts in the 1940s and they have since migrated throughout the state. Beaver dams impound water, which traps sediment and results in the development of complex channel patterns and more ecologically productive and diverse habitats than those found adjacent to man-made dams. To develop better management practices for dam removal it is essential that we understand the geomorphic and ecologic function of wood in these channels and the interconnections with floodplain dynamics and stream water chemistry. We investigate the connections among fluvial wood, channel morphology, floodplain soil moisture dynamics, and stream water chemistry in six watersheds in Massachusetts that have been impacted by either beaver or man-made dams. We hypothesize that wood load will be significantly higher below beaver dams, subsequently altering channel morphology, water chemistry, and floodplain soil moisture. Reaches are surveyed up- and downstream of each type of dam to better understand the impact dams have on the fluvial system. Surveys include a longitudinal profile, paired with dissolved oxygen and ammonium measurements, cross-section and fluvial wood surveys, hydraulic measurements, and floodplain soil moisture mapping. We found that dissolved oxygen mirrored the channel morphology, but did not vary significantly between reaches. Wood loads were significantly larger downstream of beaver dams, which resulted in significant changes to the ammonium levels. Floodplain soil moisture dynamics revealed that wood loads increased the channel complexity and strengthened connections between the stream channel and floodplain. Future work will continue to explore the complex interconnections between beaver dams, channel morphology, hydraulics, floodplain dynamics and water chemistry.

Threshold effects of flood duration on the vegetation and soils of the Upper Mississippi River floodplain, USA

USGS Publications Warehouse

De Jager, Nathan R.; Thomsen, Meredith; Yin, Yao

2012-01-01

Our results suggest that there is a threshold along the elevation gradient of this floodplain, corresponding with flood durations lasting ~40% of the growing season. At lower elevation sites, flooding exerts primary control over forest soils and vegetation, restricting the former to silt plus clay with higher organic matter and the latter to a few highly flood tolerant species. The existence of such thresholds have implications for management of floodplain soil nutrient dynamics and plant diversity under existing hydrologic regimes, more natural hydrologic regimes and more extreme hydrologic regimes that may result from climate change.

40 CFR 257.3-1 - Floodplains.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 24 2010-07-01 2010-07-01 false Floodplains. 257.3-1 Section 257.3-1 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... coastal waters, including flood-prone areas of offshore islands, which are inundated by the base flood. (3...

40 CFR 257.3-1 - Floodplains.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 40 Protection of Environment 25 2011-07-01 2011-07-01 false Floodplains. 257.3-1 Section 257.3-1 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... coastal waters, including flood-prone areas of offshore islands, which are inundated by the base flood. (3...

40 CFR 257.3-1 - Floodplains.

Code of Federal Regulations, 2013 CFR

2013-07-01

... 40 Protection of Environment 26 2013-07-01 2013-07-01 false Floodplains. 257.3-1 Section 257.3-1 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... coastal waters, including flood-prone areas of offshore islands, which are inundated by the base flood. (3...

40 CFR 257.3-1 - Floodplains.

Code of Federal Regulations, 2012 CFR

2012-07-01

... 40 Protection of Environment 26 2012-07-01 2011-07-01 true Floodplains. 257.3-1 Section 257.3-1 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... coastal waters, including flood-prone areas of offshore islands, which are inundated by the base flood. (3...

40 CFR 257.3-1 - Floodplains.

Code of Federal Regulations, 2014 CFR

2014-07-01

... 40 Protection of Environment 25 2014-07-01 2014-07-01 false Floodplains. 257.3-1 Section 257.3-1 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) SOLID WASTES CRITERIA FOR... coastal waters, including flood-prone areas of offshore islands, which are inundated by the base flood. (3...

A PROBABILITY SURVEY OF SUCCESSIONAL FOREST COMPOSITION AND CONDITION IN A GREAT RIVER FLOODPLAIN LANDSCAPE

EPA Science Inventory

Floodplains within the Great River Ecosystems (GREs) of the central U.S. are composed of dynamic mosaics of successional habitat that (when unmodified) are typically dominated by cottonwood forest (Populus ssp.). GRE riparian habitat condition and successional dynamics are linked...

Floodplain restoration enhances denitrification and reach-scale nitrogen removal in an agricultural stream

EPA Science Inventory

Streams of the agricultural Midwest export large quantities of nitrogen, which impairs downstream water quality, most notably in the Gulf of Mexico. The two-stage ditch is a novel restoration practice, in which floodplains are constructed alongside channelized ditches. During hi...

24 CFR 585.307 - Environmental procedures and standards.

Code of Federal Regulations, 2010 CFR

2010-04-01

... CFR 50.4 as follows: (1) For minor rehabilitation of a building and any property acquisition... materials; (iii) Located within a floodplain; (iv) A building for which flood insurance protection is... building and also for substantial improvement in floodplains, in addition to paragraphs (b)(1)(i) through...

SEASONAL FORAGING BY CHANNEL CATFISH ON TERRESTRIALLY BURROWING CRAYFISH IN A FLOODPLAIN-RIVER ECOSYSTEM

EPA Science Inventory

The seasonal use of terrestrially burrowing crayfish as a food item by channel catfish Ictalurus punctatus was studied in channelized and non-channelized sections of the Yockanookany River (Mississippi, USA). During seasonal inundation of the floodplains, the crayfish occupied o...

10 CFR 1022.4 - Definitions.

Code of Federal Regulations, 2011 CFR

2011-01-01

..., that is, a floodplain with a 1.0 percent chance of flooding in any given year. Critical action means..., but are not limited to, the storage of highly volatile, toxic, or water reactive materials. Critical..., technology, and implementation time. Preserve means to prevent modification to the natural floodplain or...

39 CFR 776.5 - Review procedures.

Code of Federal Regulations, 2010 CFR

2010-07-01

... Floodplain Management § 776.5 Review procedures. Officials shall follow the decision-making process outlined in paragraphs (a) through (f) of this section, when a facility action may involve floodplain issues... Emergency Management Agency (FEMA) maps, or more detailed maps if available. If such maps are not available...

Patterns of Ground Water Movement in a Portion of the Willamette River Floodplain, Oregon

EPA Science Inventory

In reaches unconstrained by revetments, the Willamette River and its floodplain along its lowland mainstem is a continually evolving system. Several channel reconstruction and restoration projects have been implemented or planned in order to obtain beneficial services along the r...

A New Hydrogeological Research Site in the Willamette River Floodplain

EPA Science Inventory

The Willamette River is a ninth-order tributary of the Columbia which passes through a productive and populous region in northwest Oregon. Where unconstrained by shoreline revetments, the floodplain of this river is a high-energy, dynamic system which supports a variety of ripari...

Recent and historic sediment dynamics along Difficult Run, a suburban Virginia Piedmont stream

NASA Astrophysics Data System (ADS)

Hupp, Cliff R.; Noe, Gregory B.; Schenk, Edward R.; Benthem, Adam J.

2013-01-01

Suspended sediment is one of the major concerns regarding the quality of water entering the Chesapeake Bay. Some of the highest suspended-sediment concentrations occur on Piedmont streams, including Difficult Run, a tributary of the Potomac River draining urban and suburban parts of northern Virginia. Accurate information on catchment level sediment budgets is rare and difficult to determine. Further, the sediment trapping portion of sediment budget represents an important ecosystem service that profoundly affects downstream water quality. Our objectives, with special reference to human alterations to the landscape, include the documentation and estimation of floodplain sediment trapping (present and historic) and bank erosion along an urbanized Piedmont stream, the construction of a preliminary sediment balance, and the estimation of legacy sediment and recent development impacts. We used white feldspar markers to measure floodplain sedimentation rates and steel pins to measure erosion rates on floodplains and banks, respectively. Additional data were collected for/from legacy sediment thickness and characteristics, mill pond impacts, stream gaging station records, topographic surveying, and sediment density, texture, and organic content. Data were analyzed using GIS and various statistical programs. Results are interpreted relative to stream equilibrium affected by both post-colonial bottomland sedimentation (legacy) and modern watershed hardening associated with urbanization. Six floodplain/channel sites, from high to low in the watershed, were selected for intensive study. Bank erosion ranges from 0 to 470 kg/m/y and floodplain sedimentation ranges from 18 to 1369 kg/m/y (m refers to meters of stream reach). Upstream reaches are net erosional, while downstream reaches have a distinctly net depositional flux providing a watershed sediment balance of 2184 kg/m/y trapped within the system. The amounts of both deposition and erosion are large and suggest nonequilibrium channel conditions. Both peak discharge and number of peaks above base have substantially increased since the mid-1960s when urbanization of the watershed began. Deposition patterns are most closely correlated with channel gradient, sinuosity, and channel width/floodplain width for recent and historic periods. The substantial amounts of fine grained sediment deposited on the floodplain over the past two centuries or so do not appear to be closely related to historic mill pond presence or location. The floodplain continues to provide the critical ecosystem service of sediment trapping in the face of multiple human alterations. Trends in sediment deposition/erosion may react rapidly to land use practices within the watershed and offer a valuable barometer of the effects of management actions.

Recent and historic sediment dynamics along Difficult Run, a suburban Virginia Piedmont stream

USGS Publications Warehouse

Hupp, Cliff R.; Noe, Gregory B.; Schenk, Edward R.; Bentham, Adam J.

2012-01-01

Suspended sediment is one of the major concerns regarding the quality of water entering the Chesapeake Bay. Some of the highest suspended-sediment concentrations occur on Piedmont streams, including Difficult Run, a tributary of the Potomac River draining urban and suburban parts of northern Virginia. Accurate information on catchment level sediment budgets is rare and difficult to determine. Further, the sediment trapping portion of sediment budget represents an important ecosystem service that profoundly affects downstream water quality. Our objectives, with special reference to human alterations to the landscape, include the documentation and estimation of floodplain sediment trapping (present and historic) and bank erosion along an urbanized Piedmont stream, the construction of a preliminary sediment balance, and the estimation of legacy sediment and recent development impacts. We used white feldspar markers to measure floodplain sedimentation rates and steel pins to measure erosion rates on floodplains and banks, respectively. Additional data were collected for/from legacy sediment thickness and characteristics, mill pond impacts, stream gaging station records, topographic surveying, and sediment density, texture, and organic content. Data were analyzed using GIS and various statistical programs. Results are interpreted relative to stream equilibrium affected by both post-colonial bottomland sedimentation (legacy) and modern watershed hardening associated with urbanization. Six floodplain/channel sites, from high to low in the watershed, were selected for intensive study. Bank erosion ranges from 0 to 470 kg/m/y and floodplain sedimentation ranges from 18 to 1369 kg/m/y (m refers to meters of stream reach). Upstream reaches are net erosional, while downstream reaches have a distinctly net depositional flux providing a watershed sediment balance of 2184 kg/m/y trapped within the system. The amounts of both deposition and erosion are large and suggest nonequilibrium channel conditions. Both peak discharge and number of peaks above base have substantially increased since the mid-1960s when urbanization of the watershed began. Deposition patterns are most closely correlated with channel gradient, sinuosity, and channel width/floodplain width for recent and historic periods. The substantial amounts of fine grained sediment deposited on the floodplain over the past two centuries or so do not appear to be closely related to historic mill pond presence or location. The floodplain continues to provide the critical ecosystem service of sediment trapping in the face of multiple human alterations. Trends in sediment deposition/erosion may react rapidly to land use practices within the watershed and offer a valuable barometer of the effects of management actions.

Using ²¹⁰Pb measurements to estimate sedimentation rates on river floodplains.

PubMed

Du, P; Walling, D E

2012-01-01

Growing interest in the dynamics of floodplain evolution and the important role of overbank sedimentation on river floodplains as a sediment sink has focused attention on the need to document contemporary and recent rates of overbank sedimentation. The potential for using the fallout radionuclides ¹³⁷Cs and excess ²¹⁰Pb to estimate medium-term (10-10² years) sedimentation rates on river floodplains has attracted increasing attention. Most studies that have successfully used fallout radionuclides for this purpose have focused on the use of ¹³⁷Cs. However, the use of excess ²¹⁰Pb potentially offers a number of advantages over ¹³⁷Cs measurements. Most existing investigations that have used excess ²¹⁰Pb measurements to document sedimentation rates have, however, focused on lakes rather than floodplains and the transfer of the approach, and particularly the models used to estimate the sedimentation rate, to river floodplains involves a number of uncertainties, which require further attention. This contribution reports the results of an investigation of overbank sedimentation rates on the floodplains of several UK rivers. Sediment cores were collected from seven floodplain sites representative of different environmental conditions and located in different areas of England and Wales. Measurements of excess ²¹⁰Pb and ¹³⁷Cs were made on these cores. The ²¹⁰Pb measurements have been used to estimate sedimentation rates and the results obtained by using different models have been compared. The ¹³⁷Cs measurements have also been used to provide an essentially independent time marker for validation purposes. In using the ²¹⁰Pb measurements, particular attention was directed to the problem of obtaining reliable estimates of the supported and excess or unsupported components of the total ²¹⁰Pb activity of sediment samples. Although there was a reasonable degree of consistency between the estimates of sedimentation rate provided by the ¹³⁷Cs and excess ²¹⁰Pb measurements, some differences existed and the various models used to interpret excess ²¹⁰Pb measurements could produce different results. By using the ¹³⁷Cs measurements to provide independent validation of the estimates of sedimentation rate provided by the different models used with the excess ²¹⁰Pb measurement it was shown that the CICCS and Composite CRS models appeared to generally provide the best results. Copyright © 2011 Elsevier Ltd. All rights reserved.

Floodplain lakes and alluviation cycles of the lower Colorado River

NASA Astrophysics Data System (ADS)

Malmon, D.; Felger, T. J.; Howard, K. A.

2007-05-01

The broad valleys along the lower Colorado River contain numerous bodies of still water that provide critical habitat for bird, fish, and other species. This chain of floodplain lakes is an important part of the Pacific Flyway - the major north-south route of travel for migratory birds in the western Hemisphere - and is also used by many resident bird species. In addition, isolated floodplain lakes may provide the only viable habitat for endangered native fish such as the razorback sucker, vulnerable to predation by introduced species in the main stem of the Colorado River. Floodplain lakes typically occupy former channel courses of the river and formed as a result of river meandering or avulsion. Persistent fluvial sediment deposition (aggradation) creates conditions that favor rapid formation and destruction of floodplain lakes, while long term river downcutting (degradation) inhibits their formation and evolution. New radiocarbon dates from wood recovered from drill cores near Topock, AZ indicate that the river aggraded an average of 3 mm/yr in the middle and late Holocene. Aggradational conditions before Hoover Dam was built were associated with rapid channel shifting and frequent lake formation. Lakes had short life spans due to rapid infilling with fine-grained sediment during turbid floods on the unregulated Colorado River. The building of dams and of armored banks had a major impact on floodplain lakes, not only by drowning large portions of the valley beneath reservoirs, but by preventing new lake formation in some areas and accelerating it in others. GIS analyses of three sets of historical maps show that both the number and total area of isolated (i.e., not linked to the main channel by a surface water connection) lakes in the lower Colorado River valley increased between 1902 and the 1950s, and then decreased though the 1970s. River bed degradation below dams inhibits channel shifting and floodplain lake formation, and the capture of fines behind the dams has prevented sediment infilling of the lakes. Bed lowering below dams and in artificially confined reaches could potentially dewater floodplain lakes, a process occurring at Beal Lake, a natural lake used for native fish restoration in the Havasu National Wildlife Refuge. Sedimentation near the upstream ends of reservoirs has created large areas of still water. One of the largest, Topock Marsh, is connected to the main channel, restricting its usefulness as a native fish nursery; other backwater areas are confined by bars that isolate standing water at tributaries.

Hydrological and sedimentary controls over fluvial thermal erosion, the Lena River, central Yakutia

NASA Astrophysics Data System (ADS)

Tananaev, Nikita I.

2016-01-01

Water regime and sedimentary features of the middle Lena River reach near Yakutsk, central Yakutia, were studied to assess their control over fluvial thermal erosion. The Lena River floodplain in the studied reach has complex structure and embodies multiple levels varying in height and origin. Two key sites, corresponding to high and medium floodplain levels, were surveyed in 2008 to describe major sedimentary units and properties of bank material. Three units are present in both profiles, corresponding to topsoil, overbank (cohesive), and channel fill (noncohesive) deposits. Thermoerosional activity is mostly confined to a basal layer of frozen channel fill deposits and in general occurs within a certain water level interval. Magnitude-frequency analysis of water level data from Tabaga gauging station shows that a single interval can be deemed responsible for the initiation of thermal action and development of thermoerosional notches. This interval corresponds to the discharges between 21,000 and 31,000 m3 s- 1, observed normally during spring meltwater peak and summer floods. Competence of fluvial thermal erosion depends on the height of floodplain level being eroded, as it acts preferentially in high floodplain banks. In medium floodplain banks, thermal erosion during spring flood is constrained by insufficient bank height, and erosion is essentially mechanical during summer flood season. Bank retreat rate is argued to be positively linked with bank height under periglacial conditions.

Limnology in the Upper Paraná River floodplain: large-scale spatial and temporal patterns, and the influence of reservoirs.

PubMed

Roberto, M C; Santana, N N; Thomaz, S M

2009-06-01

Knowledge of abiotic limnological factors is important to monitor changes caused by humans, and to explain the structure and dynamics of populations and communities in a variety of inland water ecosystems. In this study, we used a long term data-set (eight years) collected in 10 habitats with different features (river channels, and connected and isolated lakes) to describe the spatial and temporal patterns of some of the principal limnological factors. In general, the degree of connectivity of the lakes, together with the rivers to which the lakes are connected, were important determinants of their limnological characteristics. These differences are expected, because rivers entering the floodplain come from different geological regions and are subject to different human impacts. At large spatial scales, these differences contribute to the increased habitat diversity of the floodplain and thus to its high biodiversity. With regard to temporal variation, Secchi-disk transparency increased, and total phosphorus decreased in the Paraná River main channel during the last 20 years. Although these changes are directly attributed to the several reservoir cascades located upstream, the closing of the Porto Primavera dam in 1998 enhanced this effect. The increase in water transparency explains biotic changes within the floodplain. The lower-phosphorus Paraná River water probably dilutes concentrations of this element in the floodplain waterbodies during major floods, with future consequences for their productivity.

Geomorphic adjustment to hydrologic modifications along a meandering river: Implications for surface flooding on a floodplain

NASA Astrophysics Data System (ADS)

Edwards, Brandon L.; Keim, Richard F.; Johnson, Erin L.; Hupp, Cliff R.; Marre, Saraline; King, Sammy L.

2016-09-01

Responses of large regulated rivers to contemporary changes in base level are not well understood. We used field measurements and historical analysis of air photos and topographic maps to identify geomorphic trends of the lower White River, Arkansas, USA, in the 70 years following base-level lowering at its confluence with the Mississippi River and concurrent with flood control by dams. Incision was identified below a knickpoint area upstream of St. Charles, AR, and increases over the lowermost 90 km of the study site to 2 m near the confluence with the Mississippi River. Mean bankfull width increased by 30 m (21%) from 1930 to 2010. Bank widening appears to be the result of flow regulation above the incision knickpoint and concomitant with incision below the knickpoint. Hydraulic modeling indicated that geomorphic adjustments likely reduced flooding by 58% during frequent floods in the incised, lowermost floodplain affected by backwater flooding from the Mississippi River and by 22% above the knickpoint area. Dominance of backwater flooding in the incised reach indicates that incision is more important than flood control on the lower White River in altering flooding and also suggests that the Mississippi River may be the dominant control in shaping the lower floodplain. Overall, results highlight the complex geomorphic adjustment in large river-floodplain systems in response to anthropogenic modifications and their implications, including reduced river-floodplain connectivity.

Numerical modeling techniques for flood analysis

NASA Astrophysics Data System (ADS)

Anees, Mohd Talha; Abdullah, K.; Nawawi, M. N. M.; Ab Rahman, Nik Norulaini Nik; Piah, Abd. Rahni Mt.; Zakaria, Nor Azazi; Syakir, M. I.; Mohd. Omar, A. K.

2016-12-01

Topographic and climatic changes are the main causes of abrupt flooding in tropical areas. It is the need to find out exact causes and effects of these changes. Numerical modeling techniques plays a vital role for such studies due to their use of hydrological parameters which are strongly linked with topographic changes. In this review, some of the widely used models utilizing hydrological and river modeling parameters and their estimation in data sparse region are discussed. Shortcomings of 1D and 2D numerical models and the possible improvements over these models through 3D modeling are also discussed. It is found that the HEC-RAS and FLO 2D model are best in terms of economical and accurate flood analysis for river and floodplain modeling respectively. Limitations of FLO 2D in floodplain modeling mainly such as floodplain elevation differences and its vertical roughness in grids were found which can be improve through 3D model. Therefore, 3D model was found to be more suitable than 1D and 2D models in terms of vertical accuracy in grid cells. It was also found that 3D models for open channel flows already developed recently but not for floodplain. Hence, it was suggested that a 3D model for floodplain should be developed by considering all hydrological and high resolution topographic parameter's models, discussed in this review, to enhance the findings of causes and effects of flooding.

An ecological economics approach to estimate the value of a fragmented wetland in Brazil (Mato Grosso do Sul state).

PubMed

Carvalho, A R

2007-11-01

The Upper Paraná River floodplain is the last lotic stretch of an ecosystem seriously threatened given that circa 50% of the original ecosystem has been converted into reservoirs. To assess the recreational value of the Upper Paraná River floodplain, 174 tourists were interviewed using the Willingness to Pay--WTP and Travel Cost--TC methods. The annual aggregated WTP attributed by tourists was US$ 122.50 million and the variables which determine the decision in willingness to pay for the Floodplain are: 'consider oneself as a Floodplain natural resources consumer' and 'marital state'. If the single person considers her/himself as a consumer of floodplain natural resources, the WTP increases by a multiplicative factor of 38.8. The value aggregated by the TC method was US$ 234 millions and decreased by zone as the distance increases. Higher income and traveling farther increases the travel cost, which is inversely related to annual trip frequency. The total recreational value (356.5 millions per year) is high and representative since it refers to an environment fragmented by dams and with many anthropogenic effects. Therefore, the progressive changes on the landscape are a threat to local tourism, since half of the visitors are attracted solely by the scenic beauty, thereby overtaking those factors considered more important by public decision makers and managers, such as recreational fishery or boating.

Floodplain restoration enhances denitrification and reach-scale nitrogen removal in an agricultural stream.

PubMed

Roley, Sarah S; Tank, Jennifer L; Stephen, Mia L; Johnson, Laura T; Beaulieu, Jake J; Witter, Jonathan D

2012-01-01

Streams of the agricultural Midwest, USA, export large quantities of nitrogen, which impairs downstream water quality, most notably in the Gulf of Mexico. The two-stage ditch is a novel restoration practice, in which floodplains are constructed alongside channelized ditches. During high flows, water flows across the floodplains, increasing benthic surface area and stream water residence time, as well as the potential for nitrogen removal via denitrification. To determine two-stage ditch nitrogen removal efficacy, we measured denitrification rates in the channel and on the floodplains of a two-stage ditch in north-central Indiana for one year before and two years after restoration. We found that instream rates were similar before and after the restoration, and they were influenced by surface water NO3- concentration and sediment organic matter content. Denitrification rates were lower on the constructed floodplains and were predicted by soil exchangeable NO3- concentration. Using storm flow simulations, we found that two-stage ditch restoration contributed significantly to NO3- removal during storm events, but because of the high NO3- loads at our study site, < 10% of the NO3- load was removed under all storm flow scenarios. The highest percentage of NO3- removal occurred at the lowest loads; therefore, the two-stage ditch's effectiveness at reducing downstream N loading will be maximized when the practice is coupled with efforts to reduce N inputs from adjacent fields.

Assessment of groundwater input and water quality changes impacting natural vegetation in the Loxahatchee River and floodplain ecosystem, Florida

USGS Publications Warehouse

Orem, William H.; Swarzenski, Peter W.; McPherson, Benjamin F.; Hedgepath, Marion; Lerch, Harry E.; Reich, Christopher; Torres, Arturo E.; Corum, Margo D.; Roberts, Richard E.

2007-01-01

The Loxahatchee River and Estuary are small, shallow, water bodies located in southeastern Florida. Historically, the Northwest Branch (Fork) of the Loxahatchee River was primarily a freshwater system. In 1947, the river inlet at Jupiter was dredged for navigation and has remained permanently open since that time. Drainage patterns within the basin have also been altered significantly due to land development, road construction (e.g., Florida Turnpike), and construction of the C-18 and other canals. These anthropogenic activities along with sea level rise have resulted in significant adverse impacts on the ecosystem over the last several decades, including increased saltwater encroachment and undesired vegetation changes in the floodplain. The problem of saltwater intrusion and vegetation degradation in the Loxahatchee River may be partly induced by diminished freshwater input, from both surface water and ground water into the River system. The overall objective of this project was to assess the seasonal surface water and groundwater interaction and the influence of the biogeochemical characteristics of shallow groundwater and porewater on vegetation health in the Loxahatchee floodplain. The hypothesis tested are: (1) groundwater influx constitutes a significant component of the overall flow of water into the Loxahatchee River; (2) salinity and other chemical constituents in shallow groundwater and porewater of the river floodplain may affect the distribution and health of the floodplain vegetation.

Channel Incision Driven by Suburbanization: Impacts to Riparian Groundwater Flow and Overbank Flow Frequency

NASA Astrophysics Data System (ADS)

Bowles, C. J.; Lawrence, R. L.; Noll, C.; Hancock, G. S.

2005-12-01

Channel incision is a widely observed response to increased flow in urbanized watersheds, but the effects of channel lowering on riparian water tables is not well documented. In a rapidly incising suburban stream in the Virginia Coastal Plain, we hypothesize that stream incision has lowered floodplain water tables and decreased the overbank flow frequency. The monitored stream is a tributary to the James River draining 1.3 km2 of which 15% is impervious cover. Incision has occurred largely through upstream migration of a one meter high knickpoint at a rate of ~1.5 m/yr, primarily during high flow events. We installed 63 wells in six stream-perpendicular transects as well as a cluster of wells around the knickpoint to assess water table elevations beneath the floodplain adjacent to the incising stream. Two transects are located 30 and 50 m upstream of the knickpoint in the unincised floodplain, and the remainder are 5, 30, 70, and 100 m downstream in the incised floodplain. In one transect above and two below, pressure transducers attached to dataloggers provide a high-resolution record of water table changes. Erosion pins were installed and channel cross-sections surveyed to determine streambed stability. Significant differences are observed in bank morphology and groundwater flow above vs. below the knickpoint. Above the knickpoint, the banks are stable, ~3 m wide, and ~0.3 m deep, and widen and deepen slightly toward the knickpoint. The water table is relatively flat and is 0.2-0.4 m below the floodplain surface, and groundwater contours suggest flow is parallel to the stream direction. The water table responds immediately to precipitation events, and rises to the floodplain surface in significant rainfall events. Immediately downstream of the knickpoint, channel width increases by about a meter, and stream depth increases to ~1.5 meters. The water table immediately below the knickpoint possesses a steep gradient, and is up to one meter below the floodplain surface. Groundwater flow is redirected toward the stream. Moving downstream banks continue to widen, and the channel is up to 8 m wide and ~1.3 m deep ~100 m below the current knickpoint position. In the most downstream transects, the water table slopes gently toward the stream and remains ~1 m below the floodplain surface, equivalent to the depth of incision generated by knickpoint passage. Upstream of the knickpoint, overbank flooding occurs frequently, while below the knickpoint the majority of storm flow is contained within the incised channel and occupation of the floodplain is rare. The impact of incision to the riparian water table is dramatic, with a lowered water table and redirection of groundwater flow toward the stream. The incision is driven by suburbanization upstream of this riparian corridor, and has likely reduced the ability of this protected riparian system to improve the water quality of the suburban runoff that passes through it.

10 CFR 1022.13 - Floodplain or wetland assessment.

Code of Federal Regulations, 2010 CFR

2010-01-01

... negative, direct and indirect, and long- and short-term effects of the proposed action on the floodplain... wetland values (§ 1022.4) appropriate to the location under evaluation. In addition, the effects of a..., the effects on the survival, quality, and function of the wetland shall be evaluated. (3) Alternatives...

Channel, Floodplain, And Wetland Responses To Floods And Overbank Sedimentation, 1846-2006, Halfway Creek Marsh, Upper Mississippi Valley, Wisconsin

EPA Science Inventory

Conversion of upland forest and prairie vegetation to agricultural land uses, following Euro-American settlement in the Upper Mississippi River System, led to accelerated runoff and soil erosion that subsequently transformed channels, floodplains, and wetlands on bottomlands. Ha...

Harvest Influences on Floodwater Properties in a Forested Floodplain

Treesearch

R.G. Clawson; B.G Lockaby; R.B. Rummer

1999-01-01

Abstract: Floodplain forests directly influence water quality by serving as sinks, sources, or transformers of nutrients. Increases in the demand for timber raise the question of how silvicultural disturbance may affect this function. The objective of this research was to compare biogeochemical relationships between undisturbed vs. disturbed...

The increasing sacrcity of red oaks in Mississippi river floodplain forestS: Influence of the residual overstory

Treesearch

Chadwick Dearing Oliver; E.C. Burkhardt; Daniel A. Skojac

2005-01-01

Red oaks - cherrybark oak (Quercus pagoda Raf.) willow oak (Quercus phellos L.), water oak (Quercus nigra L.), and Nuttall oak (Quercus texana Buckley; aka: Quercus nuttallii Palmer) - are not regrowing in Mississippi Delta river floodplain forests in the southeastern United...

Floodplain restoration with flood control: fish habitat value of levee borrow pits

USDA-ARS?s Scientific Manuscript database

Earthen flood control levees are often built using soil excavated from borrow pits lying parallel to and riverward of the finished levee. After construction, these pits can provide valuable floodplain habitats, and their value is well established along corridors of larger rivers. However, levee bo...

Hydrologic controls on nitrogen availability in a high-latitude, semi-arid floodplain.

Treesearch

Nicholas J. Lisuzzo; Knut Kielland; Jeremy B. Jones

2008-01-01

Past research shows a discrepancy between apparent nitrogen supply and the annual growth requirements for early successional plant communities along the Tanana River floodplain in interior Alaska. Because previous measurements of nitrogen fixation, mineralization, and deposition can only account for approximately 26% of these communities' nitrogen requirements,...

Final report from VFL Technologies for the pilot-scale thermal treatment of lower East Fork Poplar Creek floodplain soils. LEFPC appendices, Volume 4, Appendix V-C

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

NONE

1994-09-01

This is the the final verification run data package for pilot scale thermal treatment of lower East Fork Poplar Creek floodplain soils. Included are data on volatiles, semivolatiles, and TCLP volatiles.

7 CFR 650.25 - Flood-plain management.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 7 Agriculture 6 2013-01-01 2013-01-01 false Flood-plain management. 650.25 Section 650.25 Agriculture Regulations of the Department of Agriculture (Continued) NATURAL RESOURCES CONSERVATION SERVICE... management will be provided by the NRCS technical service centers (§ 600.3 of this part). (2) NRCS state...

Using Dutch elm disease-tolerant elm to restore floodplains impacted by emerald ash borer

Treesearch

Kathleen S. Knight; James M. Slavicek; Rachel Kappler; Elizabeth Pisarczyk; Bernadette Wiggin; Karen. Menard

2012-01-01

American elm (Ulmus Americana L.) was a dominant species in floodplains and swamps of the Midwest before Dutch elm disease (DED) (Ophiostoma ulmi and O.novo-ulmi) reduced its populations. In many areas, ash (Fraxinus spp.) became dominant in these ecosystems. Emerald ash borer (EAB) (...

Climate sensitivity of thinleaf alder growth on an interior Alaska floodplain

Treesearch

Dana R. Nossov; Roger W. Ruess; Teresa N. Hollingsworth

2010-01-01

This study examined the climate sensitivity of the growth of riparian Alnus incana ssp. tenuifolia (thinleaf alder), a keystone nitrogen-fixer, on the Tanana River floodplain of interior Alaska. We investigated correlations between alder radial growth and inter-annual variation in monthly meteorology and hydrology, spatial...

44 CFR 9.14 - Disposal of Agency property.

Code of Federal Regulations, 2011 CFR

2011-10-01

..., DEPARTMENT OF HOMELAND SECURITY GENERAL FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS § 9.14 Disposal of... alternative use that is more consistent with the floodplain management and wetland protection policies set out... coastal high hazard area. (8) The Agency shall prepare and provide the public with a finding and public...

Hydrology, geomorphology, and vegetation of Coastal Plain rivers in the southeastern United States

Treesearch

Cliff R. Hupp

2000-01-01

Rivers of the Coastal Plain of the southeastern United States are characteristically low-gradient meandering systems that develop broad floodplains subjected to frequent and prolonged flooding. These floodplains support a relatively unique forested wetland (Bottomland Hardwoods), which have received considerable ecological study, but distinctly less hydrogeomorphic...

A new method for quantifying and modeling large scale surface water inundation dynamics and key drivers using multiple time series of Earth observation and river flow data. A case study for Australia's Murray-Darling Basin

NASA Astrophysics Data System (ADS)

Heimhuber, Valentin; Tulbure, Mirela G.; Broich, Mark

2017-04-01

Periodically inundated surface water (SW) areas such as floodplains are hotspots of biodiversity and provide a broad range of ecosystem services but have suffered alarming declines in recent history. Large scale flooding events govern the dynamics of these areas and are a critical component of the terrestrial water cycle, but their propagation through river systems and the corresponding long term SW dynamics remain poorly quantified on continental or global scales. In this research, we used an unprecedented Landsat-based time series of SW maps (1986-2011), to develop statistical inundation models and quantify the role of driver variables across the Murray-Darling Basin (MDB) (1 million square-km), which is Australia's bread basket and subject to competing demands over limited water resources. We fitted generalized additive models (GAM) between SW extent as the dependent variable and river flow data from 68 gauges, spatial time series of rainfall (P; interpolated gauge data), evapotranspiration (ET; AWRA-L land surface model) and soil moisture (SM; active passive microwave satellite remote sensing) as predictor variables. We used a fully directed and connected river network (Australian Geofabric) in combination with ancillary data, to develop a spatial modeling framework consisting of 18,521 individual modeling units. We then fitted individual models for all modeling units, which were made up of 10x10 km grid cells split into floodplain, floodplain-lake and non-floodplain areas, depending on the type of water body and its hydrologic connectivity to a gauged river. We applied the framework to quantify flood propagation times for all major river and floodplain systems across the MDB, which were in good accordance with observed travel times. After incorporating these flow lag times into the models, average goodness of fit was high across floodplains and floodplain-lake modeling units (r-squared > 0.65), which were primarily driven by river flow, and lower for non-floodplain areas (r-squared > 0.24), which were primarily driven by local rainfall. Our results indicate that local climate conditions (i.e. P, ET, SM) had more influence on SW dynamics in the northern compared to the southern MDB and were the most influential in the least regulated and most extended floodplains in the north-west. We also applied the statistical models of two floodplain areas with contrasting flooding regimes to predict SW extents of cloud-affected time steps in the Landsat time series during the large 2010 floods with high validated accuracy (r-squared > 0.97). Our findings illustrate that integrating multi-decadal time series of Earth observation data and in situ measurements with statistical modeling techniques can provide cost-effective tools for improving the management of limited SW resources and floods. The data-driven method is applicable to other large river basins and provides statistical models that can predict SW extent for cloud-affected Landsat observations or during the peak of floods and hence, allows a more detailed quantification of the dynamics of large floods compared to existing approaches. Future research will investigate the potential of image fusion techniques (i.e. ESTARFM) for improving the quantification of rapid changes in SW distribution by combining MODIS and Landsat imagery.

Forest Types in the Lower Suwannee River Floodplain, Florida?-A Report and Interactive Map

USGS Publications Warehouse

Darst, M.R.; Light, H.M.; Lewis, L.J.; Sepulveda, A.A.

2003-01-01

A map of forest types in the lower Suwannee River floodplain, Florida, was created during a study conducted from 1996 to 2000 by the U.S. Geological Survey in cooperation with the Suwannee River Water Management District. The map is presented with this report on a compact disc with interactive viewing software. The forest map can be used by scientists for ecological studies in the floodplain based on land cover types and by landowners and management personnel making land use decisions. The study area is the 10-year floodplain of the lower Suwannee River from its confluence with the Santa Fe River to the lower limit of forests near the Gulf of Mexico. The floodplain is divided into three reaches: riverine (non-tidal), upper tidal, and lower tidal, due to changes in hydrology, vegetation, and soils with proximity to the coast. The 10-year floodplain covers about 21,170 hectares; nearly 88 percent of this area (18,580 hectares) is mapped as 14 major forest types. Approximately 29 percent (5,319 hectares) of these forests have been altered by agriculture or development. About 75 percent of the area of major forest types (13,994 hectares) is wetland forests and about 25 percent (4,586 hectares) is upland forests. Tidal wetland forests (8,955 hectares) cover a much greater area than riverine wetland forests (5,039 hectares). Oak/pine upland forests are present in the riverine and upper tidal reaches of the floodplain on elevations that are inundated only briefly during the highest floods. High bottomland hardwoods are present on the higher levees, ridges, and flats of the riverine reach where soils are usually sandy. Low bottomland hardwood forests are present in the riverine reach on swamp margins and low levees and flats that are flooded continuously for several weeks or longer every 1 to 3 years. Riverine swamps are present in the lowest and wettest areas of the non-tidal floodplain that are either inundated or saturated most of the time. Upper tidal bottomland hardwood forests are present on sandy soils on high flats and in transitional areas between upland forests and swamps. Upper tidal mixed forests are found on low levees or between swamps and higher forest types. Upper tidal swamps are present at elevations below median monthly high stage and usually have surface soils that are permanently saturated mucks. Lower tidal hammocks are found on higher elevations that do not receive regular tidal inundation but have a high water table and are briefly inundated by storm surges several times a decade. Lower tidal mixed forests include swamps with numerous small hummocks or less common larger hummocks. Lower tidal swamps are found on deep muck soils that are below the elevation of the median daily or monthly high stage. Seven additional land cover types (2,590 hectares) are mapped. Water in the main channel of the lower Suwannee River (1,767 hectares) was mapped separately from open water in the floodplain (239 hectares). Other land cover types are: seepage slopes (70 hectares), isolated forested wetlands (19 hectares), marshes upstream of the tree line (505 hectares), beds of emergent aquatic vegetation (21 hectares), and floodplain glades (46 hectares)

Drying of Floodplain Forests Associated with Water-Level Decline in the Apalachicola River, Florida - Interim Results, 2006

USGS Publications Warehouse

Darst, Melanie R.; Light, Helen M.

2007-01-01

Floodplain forests of the Apalachicola River, Florida, are drier in composition today (2006) than they were before 1954, and drying is expected to continue for at least the next 50 years. Drier forest composition is probably caused by water-level declines that occurred as a result of physical changes in the main channel after 1954 and decreased flows in spring and summer months since the 1970s. Forest plots sampled from 2004 to 2006 were compared to forests sampled in the late 1970s (1976-79) using a Floodplain Index (FI) based on species dominance weighted by the Floodplain Species Category, a value that represents the tolerance of tree species to inundation and saturation in the floodplain and consequently, the typical historic floodplain habitat for that species. Two types of analyses were used to determine forest changes over time: replicate plot analysis comparing present (2004-06) canopy composition to late 1970s canopy composition at the same locations, and analyses comparing the composition of size classes of trees on plots in late 1970s and in present forests. An example of a size class analysis would be a comparison of the composition of the entire canopy (all trees greater than 7.5 cm (centimeter) diameter at breast height (dbh)) to the composition of the large canopy tree size class (greater than or equal to 25 cm dbh) at one location. The entire canopy, which has a mixture of both young and old trees, is probably indicative of more recent hydrologic conditions than the large canopy, which is assumed to have fewer young trees. Change in forest composition from the pre-1954 period to approximately 2050 was estimated by combining results from three analyses. The composition of pre-1954 forests was represented by the large canopy size class sampled in the late 1970s. The average FI for canopy trees was 3.0 percent drier than the average FI for the large canopy tree size class, indicating that the late 1970s forests were 3.0 percent drier than pre-1954 forests. The change from the late 1970s to the present was based on replicate plot analysis. The composition of 71 replicate plots sampled from 2004 to 2006 averaged 4.4 percent drier than forests sampled in the late 1970s. The potential composition of future forests (2050 or later) was estimated from the composition of the present subcanopy tree size class (less than 7.5 cm and greater than or equal to 2.5 cm dbh), which contains the greatest percentage of young trees and is indicative of recent hydrologic conditions. Subcanopy trees are the driest size class in present forests, with FIs averaging 31.0 percent drier than FIs for all canopy trees. Based on results from all three sets of data, present floodplain forests average 7.4 percent drier in composition than pre-1954 forests and have the potential to become at least 31.0 percent drier in the future. An overall total change in floodplain forests to an average composition 38.4 percent drier than pre-1954 forests is expected within approximately 50 years. The greatest effects of water-level decline have occurred in tupelo-cypress swamps where forest composition has become at least 8.8 percent drier in 2004-06 than in pre-1954 years. This change indicates that a net loss of swamps has already occurred in the Apalachicola River floodplain, and further losses are expected to continue over the next 50 years. Drying of floodplain forests will result in some low bottomland hardwood forests changing in composition to high bottomland hardwood forests. The composition of high bottomland hardwoods will also change, although periodic flooding is still occurring and will continue to limit most of the floodplain to bottomland hardwood species that are adapted to at least short periods of inundation and saturation.

A Limnological Examination of the Southwestern Amazon, Madre de Dios, Peru

NASA Astrophysics Data System (ADS)

Belcon, Alana Urnesha

This dissertation investigates the limnology of the southwestern Peruvian Amazon centered on the Madre de Dios department by examining first the geomorphology and then the ecology and biogeochemistry of the region's fluvial systems. Madre de Dios, Peru is world renowned for its prolific biodiversity and its location within the Andes biodiversity hotspot. It is also a site of study regarding the development of the Fitzcarrald Arch and that feature's geomorphological importance as the drainage center for the headwaters of the Madeira River---the Amazon's largest tributary and as well as its role as a physical divider of genetic evolution in the Amazon. Though each of these has been studied by a variety of prominent researchers, the ability to investigate all the aspects of this unique region is hampered by the lack of a regional geomorphological map. This study aims to fill that gap by using remote sensing techniques on digital elevation models, satellite imagery and soil, geology and geoecological maps already in publication to create a geomorphological map. The resulting map contains ten distinct landform types that exemplify the dominance of fluvial processes in shaping this landscape. The river terraces of the Madre de Dios River are delineated in their entirety as well as the various dissected relief units and previously undefined units. The demarcation of the boundaries of these geomorphic units will provide invaluable assistance to the selection of field sites by future researchers as well as insights into the origin of the high biodiversity indices of this region and aid in planning for biodiversity conservation. Secondly this study examines 25 tropical floodplain lakes along 300 km of the Manu River within the Manu National Park in the Madre de Dios department. Alternative stable state and regime shifts in shallow lakes typically have been examined in lakes in temperate and boreal regions and within anthropogenically disturbed basins but have rarely been studied in tropical or in undisturbed regions. In contrast this study focuses on a tropical region of virtually no human disturbance and evaluates the effects of hydrological variability on ecosystem structure and dynamics. Using satellite imagery a 23 yr timeline of ecological regime shifts in Amazon oxbow lakes or "cochas" is reconstructed. The study shows that almost 25% of the river's floodplain lakes experience periodic abrupt vegetative changes with an average 3.4% existing in an alternative stable state in any given year. State changes typically occur from a stable phytoplankton-dominated state to a short lived, <3 yr, floating macrophytic state and often occur independent of regional flooding. We theorize that multiple dynamics, both internal and external, drive vegetative regime shifts in the Manu but insufficient data yet exists in this remote region to identify the key processes. To complete the investigation of tropical limnology the third study compares and contrasts the nutrient-productivity ration of floodplain and non-floodplain lakes globally and regionally. For over 70 years a strong positive relationship between sestonic chlorophyll-a (Chl-a) and total phosphorus (TP) has been established with phosphorus generally viewed as the most limiting factor to productivity. Most of these studies, however, have focused on northern, temperate regions where the lakes are typically postglacial, isolated and fed by small streams. Relatively little work has been done on floodplain lakes which are semi or permanently connected to the river. This study examines the relationship between nutrients and productivity in floodplain lakes globally through an extensive literature synthesis. Values for total phosphorus, total nitrogen and chlorophyll-a were collected for 523 floodplain lakes, represented by 288 data points while 551 data points were collected for 5444 non-floodplain lakes. Analysis revealed that globally, floodplain lakes do not show any significant difference in the total phosphorus/chlorophyll-a relationship from that found in non-floodplain lakes but significant differences are seen between tropical and temperate lakes. We propose that the term 'floodplain' lake should serve as purely a geographical descriptor and that it is lacking as an ecological indicator. Instead factors such as precipitation seasonality, hydrological connectivity and regional flooding regimes are better indicators of high or low productivity in floodplain lakes.

Strategies for detection of floodplain inundation with multi-frequency polarimetric SAR

NASA Technical Reports Server (NTRS)

Hess, Laura L.; Melack, John M.

1992-01-01

Mapping of floodplain inundation patterns is a key element in developing hydrological and biogeochemical models for large tropical river basins such as the Amazon. Knowledge of the time sequence of inundation is necessary to determine both water routing and biogenic gas fluxes. Synthetic Aperture Radar (SAR) is uniquely suited for this application because of its ability to penetrate cloud cover and, in many cases, to detect flooding beneath a forest or herbaceous canopy. A procedure for discriminating flooded forest, flooded herbaceous vegetation, and open water from other cover types for a coastal wetland site on the lower Altamaha floodplain, Georgia, emphasizing robust classifiers that are not site-specific is currently being developed.

Geomorphology and flood-plain vegetation of the Sprague and lower Sycan Rivers, Klamath Basin, Oregon

USGS Publications Warehouse

O'Connor, James E.; McDowell, Patricia F.; Lind, Pollyanna; Rasmussen, Christine G.; Keith, Mackenzie K.

2015-01-01

Despite these effects of human disturbances, many of the fundamental physical processes forming the Sprague River fluvial systems over the last several thousand years still function. In particular, flows are unregulated, sediment transport processes are active, and overbank flooding allows for floodplain deposition and erosion. Therefore, restoration of many of the native physical conditions and processes is possible without substantial physical manipulation of current conditions for much of the Sprague River study area. An exception is the South Fork Sprague River, where historical trends are not likely to reverse until it attains a more natural channel and flood-plain geometry and the channel aggrades to the extent that overbank flow becomes common.

Vegetation, Soil, and Flooding Relationships in a Blackwater Floodplain Forest

Treesearch

Sammy L. King; David Gartner; Mark H. Eisenbies

2003-01-01

Hydroperiod is considered the primary determinant of plant species distribution in temperate floodplain forests, but most studies have focused on alluvial (sediment-laden) river systems. Few studies have evaluated plant community relationships in blackwater river systems of the South Atlantic Coastal Plain of North America. In this study. we characterized the soils....

Differential recovery of a deepwater swamp forest across a gradient of disturbance intensity

Treesearch

Diane De Steven; Rebecca R. Sharitz

1997-01-01

On the Savannah River Site, South Carolina, USA, large areas of floodplain swamp forest of baldcypress (Taxodium distichum) and water tupelo (Nyssa aquatica) were destroyed by the cumulative impacts of cooling-water discharges over a 35-year period of nuclear reactor operations. In one floodplain area, four years after thermal...

Invasive sweetclover (Melilotus alba) impacts native seeding recruitment along floodplains of interior Alaska

Treesearch

Blaine T. Spellman; Tricia L. Wurtz

2011-01-01

Sweetclover (Melilotus alba) is a nonnative legume that has formed dense and extensive patches along several rivers in Alaska. Our research objective was to determine if sweetclover impacts recruitment of native seedlings in floodplain habitats. To determine if sweetclover impacted recruitment, we conducted a removal experiment along two rivers in...

CHANGES IN LOWLAND FLOODPLAIN SEDIMENTATION PROCESSES: PRE-DISTURBANCE TO POST-REHABILITATION, COSUMNES RIVER, CA. (R825433)

EPA Science Inventory

During the late Holocene, sediment deposition on the lowland Cosumnes River floodplain, CA has depended on factors that varied temporally and spatially, such as basin subsidence, sea level rise, flow, and sediment supply from both the Sacramento River system and from the Cosum...

Exoenzyme activities as indicators of dissolved organic matter composition in the hyporheic zone of a floodplain river

Treesearch

Sandra M. Clinton; Rick T. Edwards; Stuart E.G. Findlay

2010-01-01

We measured the hyporheic microbial exoenzyme activities in a floodplain river to determine whether dissolved organic matter (DOM) bioavailability varied with overlying riparian vegetation patch structure or position along flowpaths. Particulate organic matter (POM), dissolved organic carbon (DOC), dissolved oxygen (DO), electrical conductivity and temperature were...

24 CFR 55.22 - Conveyance restrictions for the disposition of multifamily real property.

Code of Federal Regulations, 2014 CFR

2014-04-01

... disposition of multifamily real property. 55.22 Section 55.22 Housing and Urban Development Office of the... restrictions for the disposition of multifamily real property. (a) In the disposition (including leasing) of multifamily properties acquired by HUD that are located in a floodplain (a 500-year floodplain for a Critical...

13 CFR 120.172 - Flood-plain and wetlands management.

Code of Federal Regulations, 2010 CFR

2010-01-01

... 8-step decision making process with respect to: (1) Construction or acquisition of anything, other than a building; (2) Repair and restoration equal to more than 50% of the market value of a building... base floodplain; (2) Repairs, other than to buildings, that are less than 50% of the market value; (3...

13 CFR 120.172 - Flood-plain and wetlands management.

Code of Federal Regulations, 2011 CFR

2011-01-01

... 8-step decision making process with respect to: (1) Construction or acquisition of anything, other than a building; (2) Repair and restoration equal to more than 50% of the market value of a building... base floodplain; (2) Repairs, other than to buildings, that are less than 50% of the market value; (3...

13 CFR 120.172 - Flood-plain and wetlands management.

Code of Federal Regulations, 2013 CFR

2013-01-01

... 8-step decision making process with respect to: (1) Construction or acquisition of anything, other than a building; (2) Repair and restoration equal to more than 50% of the market value of a building... base floodplain; (2) Repairs, other than to buildings, that are less than 50% of the market value; (3...

13 CFR 120.172 - Flood-plain and wetlands management.

Code of Federal Regulations, 2012 CFR

2012-01-01

... 8-step decision making process with respect to: (1) Construction or acquisition of anything, other than a building; (2) Repair and restoration equal to more than 50% of the market value of a building... base floodplain; (2) Repairs, other than to buildings, that are less than 50% of the market value; (3...

Changes in Production and Nutrient Cycling across a Wetness Gradient within a Floodplain Forest

Treesearch

Robin G. Clawson; B. Graeme Lockaby; Bob Rummer

2001-01-01

Floodplain forest ecosystems are highly valuable to society because of their potential for water quality improvement and vegetation productivity, among many other functions. Previous studies have indicated that hydrology influences productivity but that the relationship between hydroperiod and productivity is a complex one. Consequently, we compared multiple indexes of...

The Bottomland Hardwoods of the Hatchie River, The Only Unchannelized Mississippi Tributary

Treesearch

Roger Steed; Edward Buckner

2002-01-01

Documenting the natural condition of the floodplain forests of Mississippi River tributaries becomes ever more elusive as cultural alterations continue to obscure their "original" character. The 4,532 hectare Hatchie National Wildlife Refuge (HNWR) in West Tennessee provides the best-available opportunity to document the floodplain forests that once...

39 CFR 776.6 - Design requirements for construction.

Code of Federal Regulations, 2011 CFR

2011-07-01

... 39 Postal Service 1 2011-07-01 2011-07-01 false Design requirements for construction. 776.6 Section 776.6 Postal Service UNITED STATES POSTAL SERVICE ENVIRONMENTAL REGULATIONS FLOODPLAIN AND WETLAND PROCEDURES Floodplain Management § 776.6 Design requirements for construction. If structures impact, are located in, or support development in a...

Quantifying flooding regime in floodplain forests to guide river restoration

Treesearch

Christian O. Marks; Keith H. Nislow; Francis J. Magilligan

2014-01-01

Determining the flooding regime needed to support distinctive floodplain forests is essential for effective river conservation under the ubiquitous human alteration of river flows characteristic of the Anthropocene Era. At over 100 sites throughout the Connecticut River basin, the largest river system in New England, we characterized species composition, valley and...

EFFECTS OF FLOOD PULSES ON NITRIFICATION RATES IN UPPER MISSISSIPPI RIVER FORESTED FLOODPLAINS, 2ND PRESENTATION IN 2007

EPA Science Inventory

Presentation is designed to enlighten the interested masses about potentials in nutrient trading and ecosystem services in our great river floodplain ecosystems. It is not intended for policy, rather to stimulate thought on the importance of natural flooding regimes and how to b...

Red River of the North Reconnaissance Report: Red Lake River.

DTIC Science & Technology

1980-12-01

cuckoo flower, Jack-in-the-pulpit, dwarf bladderwort, smallwood orchid, and northern bur-reed. The rare plants growing in the dry plains and hills area... Norman , OK. I99 .4 j 99 Appendix A FLOODPLAIN DELINEATION i / * _ Appendix A FLOODPLAIN DELINEATION Prior to this study, no attempt was made to

The Influence of an Invasive Shrub, Buddleja Davidii on a Native Shrub, Griselinia Littoralis Transplanted into a New Zealand Floodplain Chronosequence

EPA Science Inventory

Griselinia littoralis, a native New Zealand shrub, was planted into a chronosequence (0 to 8 yrs since flooding) dominated by the non-indigenous shrub, Buddleja davidii in three New Zealand floodplains to determine to what extent facilitation and competitive inhibition may influe...

Evaluation of RPM™ oak seedlings in afforesting floodplain crop fields along the Missouri River

Treesearch

Daniel C. Dey; John M. Kabrick; Michael A. Gold

2005-01-01

Regenerating oaks in agricultural floodplains is problematic because of their slow juvenile shoot growth, intense plant competition, seasonal flooding, and browsing by wildlife. Planting large nursery stock has been recommended to increase the competitiveness of oak seedlings. The Forrest Keeling Nursery in Missouri developed the Root Production Method (RPM™)...

Fine Root Productivity and Dynamics on a Forested Floodplain in South Carolina

Treesearch

Terrell T. Baker; William Conner; H. B. Graeme Lockaby; John A. Stanturf

2001-01-01

The highly dynamic, fine root component of forested wetland ecosystems fine root dynamics is a challenging endeavor in any system, but the difficulties are particularly evident in forested floodplains where frequent hydrologic fluctuations directly influence fine root dynamics. Fine root (53 mm) biomass, production, and turnover were estimated for three soils...

Vegetation responses to helicopter and ground based logging in blackwater floodplain forests

Treesearch

R.H. Jones; S.L. Stokes; B.G. Lockaby; John.A. Stanturf

2000-01-01

Logging in floodplains of low order, blackwater streams may damage cxisting seedlings and rootstocks, and create soil conditions that inhibit establishment and growth of regeneration after harvest. Removal of logs via helicopters has been advocated to minimize soil damage and facilitate rapid revegetation. We tested impacts of helicopter versus conventional skidder...

Modeling meander morphodynamics over self-formed heterogeneous floodplains

NASA Astrophysics Data System (ADS)

Bogoni, Manuel; Putti, Mario; Lanzoni, Stefano

2017-06-01

This work addresses the signatures embedded in the planform geometry of meandering rivers consequent to the formation of floodplain heterogeneities as the river bends migrate. Two geomorphic features are specifically considered: scroll bars produced by lateral accretion of point bars at convex banks and oxbow lake fills consequent to neck cutoffs. The sedimentary architecture of these geomorphic units depends on the type and amount of sediment, and controls bank erodibility as the river impinges on them, favoring or contrasting the river migration. The geometry of numerically generated planforms obtained for different scenarios of floodplain heterogeneity is compared to that of natural meandering paths. Half meander metrics and spatial distribution of channel curvatures are used to disclose the complexity embedded in meandering geometry. Fourier Analysis, Principal Component Analysis, Singular Spectrum Analysis and Multivariate Singular Spectrum Analysis are used to emphasize the subtle but crucial differences which may emerge between apparently similar configurations. A closer similarity between observed and simulated planforms is attained when fully coupling flow and sediment dynamics (fully-coupled models) and when considering self-formed heterogeneities that are less erodible than the surrounding floodplain.

Estimating sedimentation rates and sources in a partially urbanized catchment using caesium-137

NASA Astrophysics Data System (ADS)

Ormerod, L. M.

1998-06-01

While there has been increased interest in determining sedimentation rates and sources in agricultural and forested catchments in recent years, there have been few studies dealing with urbanized catchments. A study of sedimentation rates and sources within channel and floodplain deposits of a partially urbanized catchment has been undertaken using the 137Cs technique. Results for sedimentation rates showed no particular downstream pattern. This may be partially explained by underestimation of sedimentation rates at some sites by failure to sample the full 137Cs profile, floodplain erosion and deliberate removal of sediment. Evidence of lateral increases in net sedimentation rates with distance from the channel may be explained by increased floodplain erosion at sites closer to the channel and floodplain formation by lateral deposition. Potential sediment sources for the catchment were considered to be forest topsoil, subsurface material and sediments derived from urban areas, which were found to be predominantly subsurface material. Tracing techniques showed an increase in subsurface material for downstream sites, confirming expectations that subsurface material would increase in the downstream direction in response to the direct and indirect effects of urbanization.

Abundance and biomass responses of microbial food web components to hydrology and environmental gradients within a floodplain of the River Danube.

PubMed

Palijan, Goran

2012-07-01

This study investigated the relationships of time-dependent hydrological variability and selected microbial food web components. Samples were collected monthly from the Kopački Rit floodplain in Croatia, over a period of 19 months, for analysis of bacterioplankton abundance, cell size and biomass; abundance of heterotrophic nanoflagellates and nanophytoplankton; and concentration of chlorophyll a. Similar hydrological variability at different times of the year enabled partition of seasonal effects from hydrological changes on microbial community properties. The results suggested that, unlike some other studies investigating sites with different connectivity, bacterioplankton abundance, and phytoplankton abundance and biomass increased during lentic conditions. At increasing water level, nanophytoplankton showed lower sensitivity to disturbance in comparison with total phytoplankton biomass: this could prolong autotrophic conditions within the floodplain. Bacterioplankton biomass, unlike phytoplankton, was not impacted by hydrology. The bacterial biomass less affected by hydrological changes can be an important additional food component for the floodplain food web. The results also suggested a mechanism controlling bacterial cell size independent of hydrology, as bacterial cell size was significantly decreased as nanoflagellate abundance increased. Hydrology, regardless of seasonal sucession, has the potential to structure microbial food webs, supporting microbial development during lentic conditions. Conversely, other components appear unaffected by hydrology or may be more strongly controlled by biotic interactions. This research, therefore, adds to understanding on microbial food web interactions in the context of flood and flow pulses in river-floodplain ecosystems.

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

Wainwright, Haruko M.; Flores Orozco, Adrian; Bucker, Matthias

In floodplain environments, a naturally reduced zone (NRZ) is considered to be a common biogeochemical hot spot, having distinct microbial and geochemical characteristics. Although important for understanding their role in mediating floodplain biogeochemical processes, mapping the subsurface distribution of NRZs over the dimensions of a floodplain is challenging, as conventional wellbore data are typically spatially limited and the distribution of NRZs is heterogeneous. In this work, we present an innovative methodology for the probabilistic mapping of NRZs within a three-dimensional (3-D) subsurface domain using induced polarization imaging, which is a noninvasive geophysical technique. Measurements consist of surface geophysical surveys andmore » drilling-recovered sediments at the U.S. Department of Energy field site near Rifle, CO (USA). Inversion of surface time domain-induced polarization (TDIP) data yielded 3-D images of the complex electrical resistivity, in terms of magnitude and phase, which are associated with mineral precipitation and other lithological properties. By extracting the TDIP data values colocated with wellbore lithological logs, we found that the NRZs have a different distribution of resistivity and polarization from the other aquifer sediments. To estimate the spatial distribution of NRZs, we developed a Bayesian hierarchical model to integrate the geophysical and wellbore data. In addition, the resistivity images were used to estimate hydrostratigraphic interfaces under the floodplain. Validation results showed that the integration of electrical imaging and wellbore data using a Bayesian hierarchical model was capable of mapping spatially heterogeneous interfaces and NRZ distributions thereby providing a minimally invasive means to parameterize a hydrobiogeochemical model of the floodplain.« less

Adaptations and Predispositions of Different Middle European Arthropod Taxa (Collembola, Araneae, Chilopoda, Diplopoda) to Flooding and Drought Conditions

PubMed Central

Marx, Michael Thomas; Guhmann, Patrick; Decker, Peter

2012-01-01

Simple Summary This review summarizes adaptations and predispositions of different arthropod taxa (springtails, web spiders, millipedes and centipedes) to flood and drought conditions. The main focus sis directed to arthropod species, which are living in Middle European floodplain forests and wetlands, because of the fast change of flood and drought conditions in these habitats. Furthermore the effects of the predicted regional climate change like increasing aperiodic summer flooding and decreasing winter and spring floods are also discussed. Abstract Floodplain forests and wetlands are amongst the most diverse and species rich habitats on earth. Arthropods are a key group for the high diversity pattern of these landscapes, due to the fact that the change between flooding and drought causes in different life cycles and in a variety of adaptations in the different taxa. The floodplain forests and wetlands of Central Amazonia are well investigated and over the last 50 years many adaptations of several hexapod, myriapod and arachnid orders were described. In contrast to Amazonia the Middle European floodplains were less investigated concerning the adaptations of arthropods to flood and drought conditions. This review summarizes the adaptations and predispositions of springtails, web spiders, millipedes and centipedes to the changeable flood and drought conditions of Middle European floodplain forests and wetlands. Furthermore the impact of regional climate change predictions like increasing aperiodic summer floods and the decrease of typical winter and spring floods are discussed in this article. PMID:26487164

Estimating continuous floodplain and major river bed topography mixing ordinal coutour lines and topographic points

NASA Astrophysics Data System (ADS)

Bailly, J. S.; Dartevelle, M.; Delenne, C.; Rousseau, A.

2017-12-01

Floodplain and major river bed topography govern many river biophysical processes during floods. Despite the grow of direct topographic measurements from LiDARS on riverine systems, it still room to develop methods for large (e.g. deltas) or very local (e.g. ponds) riverine systems that take advantage of information coming from simple SAR or optical image processing on floodplain, resulting from waterbodies delineation during flood up or down, and producing ordered coutour lines. The next challenge is thus to exploit such data in order to estimate continuous topography on the floodplain combining heterogeneous data: a topographic points dataset and a located but unknown and ordered contourline dataset. This article is comparing two methods designed to estimate continuous topography on the floodplain mixing ordinal coutour lines and continuous topographic points. For both methods a first estimation step is to value each contourline with elevation and a second step is next to estimate the continuous field from both topographic points and valued contourlines. The first proposed method is a stochastic method starting from multigaussian random-fields and conditional simualtion. The second is a deterministic method based on radial spline fonction for thin layers used for approximated bivariate surface construction. Results are first shown and discussed from a set of synoptic case studies presenting various topographic points density and topographic smoothness. Next, results are shown and discuss on an actual case study in the Montagua laguna, located in the north of Valparaiso, Chile.

Adaptive Management of Return Flows: Lessons from a Case Study in Environmental Water Delivery to a Floodplain River

NASA Astrophysics Data System (ADS)

Wolfenden, Benjamin J.; Wassens, Skye M.; Jenkins, Kim M.; Baldwin, Darren S.; Kobayashi, Tsuyoshi; Maguire, James

2018-03-01

For many floodplain rivers, reinstating wetland connectivity is necessary for ecosystems to recover from decades of regulation. Environmental return flows (the managed delivery of wetland water to an adjacent river) can be used strategically to facilitate natural ecosystem connectivity, enabling the transfer of nutrients, energy, and biota from wetland habitats to the river. Using an informal adaptive management framework, we delivered return flows from a forested wetland complex into a large lowland river in south-eastern Australia. We hypothesized that return flows would (a) increase river nutrient concentrations; (b) reduce wetland nutrient concentrations; (c) increase rates of ecosystem metabolism through the addition of potentially limiting nutrients, causing related increases in the concentration of water column chlorophyll-a; and (d) increase the density and species richness of microinvertebrates in riverine benthic habitats. Our monitoring results demonstrated a small increase in the concentrations of several key nutrients but no evidence for significant ecological responses was found. Although return flows can be delivered from forested floodplain areas without risking hypoxic blackwater events, returning nutrient and carbon-rich water to increase riverine productivity is limited by the achievable scale of return flows. Nevertheless, using return flows to flush carbon from floodplains may be a useful management tool to reduce carbon loads, preparing floodplains for subsequent releases (e.g., mitigating the risk of hypoxic blackwater events). In this example, adaptive management benefited from a semi-formal collaboration between science and management that allowed for prompt decision-making.

Sediment Flux and Storage in a Rural Southeastern Piedmont River System

NASA Astrophysics Data System (ADS)

Jackson, C. R.; Martin, J. K.

2001-12-01

A sediment budget was developed for a representative rural southeastern Piedmont watershed to provide information on the relative importance of sediment sources. Sediment issues in the southeastern Piedmont are complicated by the so-called legacy sediment produced by poor farming practices during the cotton-farming era, approximately 1810-1930. The Murder Creek basin near Monticello, GA was chosen because: it featured forestry and agriculture as the principal land uses; a USGS gage provided a flow record; and the creek deposited in a reservoir built in 1948. Suspended load export was calculated using a sediment rating curve and the USGS flow time series. Bed load export was determined by estimating the volume of sediment deposited in the reservoir since construction. Unpaved road erosion was estimated using the WEPP model, and other surface erosion was estimated using USLE and delivery ratios. Historical floodplain storage was determined by coring floodplain deposits, measuring the depth to the pre-historic/historic sediment interface, and multiplying by the area of the floodplain. Recent accretion rates were estimated using dendrogeomorphology. Results showed that the practices of the cotton farming era deposited an average of 1.6 meters of sediment on the floodplains. This depth was relatively uniform across the watershed. The cotton-farming sediment in storage exceeds the current annual export by a factor of about 5000. Approximately half of the current export comes from current inputs, and half comes from remobilized floodplain sediments.

Estimating continuous floodplain and major river bed topography mixing ordinal coutour lines and topographic points

NASA Astrophysics Data System (ADS)

Brown, T. G.; Lespez, L.; Sear, D. A.; Houben, P.; Klimek, K.

2016-12-01

Floodplain and major river bed topography govern many river biophysical processes during floods. Despite the grow of direct topographic measurements from LiDARS on riverine systems, it still room to develop methods for large (e.g. deltas) or very local (e.g. ponds) riverine systems that take advantage of information coming from simple SAR or optical image processing on floodplain, resulting from waterbodies delineation during flood up or down, and producing ordered coutour lines. The next challenge is thus to exploit such data in order to estimate continuous topography on the floodplain combining heterogeneous data: a topographic points dataset and a located but unknown and ordered contourline dataset. This article is comparing two methods designed to estimate continuous topography on the floodplain mixing ordinal coutour lines and continuous topographic points. For both methods a first estimation step is to value each contourline with elevation and a second step is next to estimate the continuous field from both topographic points and valued contourlines. The first proposed method is a stochastic method starting from multigaussian random-fields and conditional simualtion. The second is a deterministic method based on radial spline fonction for thin layers used for approximated bivariate surface construction. Results are first shown and discussed from a set of synoptic case studies presenting various topographic points density and topographic smoothness. Next, results are shown and discuss on an actual case study in the Montagua laguna, located in the north of Valparaiso, Chile.

Effects of loss of lateral hydrological connectivity on fish functional diversity.

PubMed

Liu, Xueqin; Wang, Hongzhu

2018-05-26

Loss of lateral hydrological connectivity (LHC) is a major cause of biodiversity decline in river floodplains, yet little is known about its effects on aquatic functional diversity in these ecosystems. We quantified functional alpha and beta diversity of fish assemblages in Yangtze River floodplain lakes, and explored their responses to loss of LHC using generalized linear mixed models. Functional richness was much lower in river disconnected lakes where functional evenness and divergence were higher. LHC was the most important factor shaping fish diversity patterns in this region. The predicted reduction due to loss of LHC was higher in functional richness (0.47-0.82) than in taxonomic richness (0.32) of all species assemblages in contrast to non-migratory species assemblages. It seemed that functional strategies were highly unevenly distributed between migratory and non-migratory fishes in the floodplain. Taxonomic beta diversity was much higher than functional beta diversity. The former was contributed mainly by spatial turnover component (73.6-83.8%) suggesting that dissimilarity among fish assemblages was largely induced by species replacement, while the latter was induced by nestedness-resultant component (70.7-86.0%) indicating a stronger role of function loss without replacement. Both taxonomic and functional beta diversity were higher in disconnected lakes, where they were significantly correlated with fishing activity and water quality. Our study determined for the first time the effects of loss of LHC on fish functional diversity in large river floodplains. We highlight the serious decline of fish functional richness in a large floodplain, and functional diversity remained highly vulnerable to loss of LHC even in such a species rich ecosystem. Our results provide important implications regarding biodiversity conservation and LHC restoration in large river floodplains. This article is protected by copyright. All rights reserved. This article is protected by copyright. All rights reserved.

Understanding controls on redox processes in floodplain sediments of the Upper Colorado River Basin

DOE PAGES

Noël, Vincent; Boye, Kristin; Kukkadapu, Ravi K.; ...

2017-12-15

Floodplains, heavily used for water supplies, housing, agriculture, mining, and industry, are important repositories of organic carbon, nutrients, and metal contaminants. The accumulation and release of these species is often mediated by redox processes. By understanding the physicochemical, hydrological, and biogeochemical controls on the distribution and variability of sediment redox conditions we can develop conceptual and numerical models of contaminant transport within floodplains. The Upper Colorado River Basin (UCRB) is impacted by former uranium and vanadium ore processing, resulting in contamination by V, Cr, Mn, As, Se, Mo and U. Previous authors have suggested that sediment redox activity occurring withinmore » organic carbon-enriched bodies located below the groundwater level may be regionally important to the maintenance and release of contaminant inventories, particularly uranium. To help assess this hypothesis, vertical distributions of Fe and S redox states and sulfide mineralogy were assessed in sediment cores from three floodplain sites spanning a 250 km transect of the central UCRB. Our results support the hypothesis that organic-enriched reduced sediments are important zones of biogeochemical activity within UCRB floodplains. Furthermore, we found that the presence of organic carbon, together with pore saturation, are the key requirements for maintaining reducing conditions, which were dominated by sulfate-reduction products. Sediment texture was found to be of secondary importance and to moderate the response of the system to external forcing, such as oxidant diffusion. Consequently, fine-grain sediments are relatively resistant to oxidation in comparison to coarser-grained sediments. Exposure to oxidants consumes precipitated sulfides, with a disproportionate loss of mackinawite (FeS) as compared to the more stable pyrite. The accompanying loss of redox buffering capacity creates the potential for release of sequestered radionuclides and metals. Because of their redox reactivity and stores of metals, C, and N, organic-enriched sediments are likely to be important to nutrient and contaminant mobility within UCRB floodplain aquifers.« less

Probabilistic Evaluation of Anthropogenic Regulations In a Vegetated River Channel Using a Vegetation Dynamics Modeling

NASA Astrophysics Data System (ADS)

Miyamoto, Hitoshi

2015-04-01

Vegetation overgrowth in fluvial floodplains, gravel beds, and sand bars has been a serious engineering problem for riparian management in Japan. From the viewpoints of flood control and ecological conservation, it would be necessary to predict the vegetation dynamics accurately for long-term duration. In this research, we have developed a stochastic model for predicting the vegetation dynamics in fluvial floodplains with emphasis on the interaction with flood impacts. The model consists of the following four components: (i) long-term stochastic behavior of flow discharge, (ii) hydrodynamics in a channel with floodplain vegetation, (iii) variation of riverbed topography, and (iv) vegetation dynamics on floodplains. In the vegetation dynamics model, the flood discharge (i) is stochastically simulated using a filtered Poisson process, one of the conventional approaches in hydrological time-series generation. The component for vegetation dynamics (iv) includes the effects of tree growth, mortality by floods, and infant tree recruitment. Vegetation condition has been observed mainly before and after floods since 2008 at a field site located between 23-24 km from the river mouth in Kako River, Japan. The Kako River has the catchment area of 1,730 km2 and the main channel length of 96 km. This site is one of the vegetation overgrowth sites in the Kako River floodplains. The predominant tree species are willows and bamboos. In the field survey, the position, trunk diameter and height of each tree as well as the riverbed materials were measured after several flood events to investigate their impacts on the floodplain vegetation community. This presentation tries to examine effects of anthropogenic river regulations, i.e., thinning and cutting-down, in the vegetated channel in Kako River by using the vegetation dynamics model. Sensitivity of both the flood water level and the vegetation status in the channel is statistically evaluated in terms of the different cutting-down levels, timings and scales of the thinning, etc., by the Monte Carlo simulation of the model.

Spatial Variability in Decomposition of Organic Carbon Along a Meandering River Floodplain

NASA Astrophysics Data System (ADS)

Sutfin, N. A.; Rowland, J. C.; Tfaily, M. M.; Bingol, A. K.; Washton, N.

2017-12-01

Rivers are an important component of the terrestrial carbon cycle and floodplains can provide significant storage of organic carbon. Quantification of long-term storage, however, requires determination of the residence time of sediment and the decomposition rate of organic carbon in floodplains. We use fourier transform ion cyclotron resonance (FTICR) mass spectrometry to examine the organic carbon compounds present in sediment within three floodplain settings: point bars, cutbanks, and abandoned channels. We define decomposition of organic carbon in floodplain sediment as the ratio between the number of protein versus lignin, which serve as proxies for microbial-derived and terrestrial-derived organic carbon, respectively. Samples were collected at 0-5 cm, 5-15cm, and 15-30 cm depth along four transects that span a longitudinal valley distance of 8 km on the East River near Crested Butte, CO. Although no significant trends in decomposition ratio exist longitudinally between the fours transects, floodplain settings exhibit significant differences. At shallow depths (0-5 cm), there are no significant differences among settings, with the exception of gravel portions of point bars below bankfull flow, where the highest decomposition is present. Conversely, cutbanks contain significantly lower decomposition ratios compared with point bars, gravel bars, and abandoned channels when considering all depth intervals. Pointbars exhibit significantly greater protein vs. lignin at the surface compared to greater depth. Higher decomposition ratios along abandoned channels and point bars suggest that frequent wetting and drying periods, abundant oxygen, and continuous downstream movement and decomposition of organic matter occurs within the channel. Lower decomposition ratios and consistent trends with depth along cutbanks, suggest that these stable surfaces serve as organic carbon reservoirs that could become an increased source of carbon to the channel with increasing bank erosion. Detailed differences of organic carbon compounds in sediments of cutbanks, point bars, and abandoned channel will be examined in September 2017 using nuclear magnetic resonance (NMR).

A global review on the influence of beavers (Castor fiber, Castor canadensis) on river and floodplain dynamics

NASA Astrophysics Data System (ADS)

Larsen, Annegret; Lane, Stuart; Larsen, Joshua

2017-04-01

Beavers (Castor fiber, Castor canadensis) have the ability to actively engineer their habitat, which they can do most effectively in lower order streams and their floodplains. Hence, this engineering has the potential to alter the hydrology, geomorphology, biogeochemistry, and ecology of river systems and the feedbacks between them. Thus, the beaver is often referred to as an 'ecosystem engineer' and is reflected in their recognition as a key species when restoring ecosystems. This capacity to engineer low order streams also shapes a range of positive and negative perceptions on their influence. On the one hand they may be perceived as capable of undermining existing river engineering schemes and the land use of associated floodplains, and on the other hand beavers may provide an alternative to traditional 'hard' engineering, potentially improving river restoration success. The aim of this review is to summarize research to date on the impacts of beavers on stream and floodplain hydrology, geomorphology, water-quality and ecology, and the feedbacks between them. Our review shows that: (1) research has been focused heavily on North American streams, with far less research outside this North American context; (2) there is a tendency to investigate beaver impacts from the perspective of individual disciplines, to the detriment of considering broader process feedbacks, notably at the interface of hydro-geomorphology and riparian ecology; (3) it remains unclear to which extent beavers genuinely engineered streams prior to human impact, pointing to the need for longer term (millennium scale) studies on how beavers have changed river-floodplain systems. Crucially, we conclude that the investigation of the effects of beavers on streams and floodplains, especially in a longer-term, and their use for river restoration can only be understood through the thorough investigation of antecedent hydro-geomorphic conditions which takes account of the ways in which beavers and humans have interacted together over many centuries.

Wintering waterbirds in a large river floodplain: Hydrological connectivity is the key for reconciling development and conservation.

PubMed

Xia, Shaoxia; Liu, Yu; Wang, Yuyu; Chen, Bin; Jia, Yifei; Liu, Guanhua; Yu, Xiubo; Wen, Li

2016-12-15

An alteration in the hydrological connectivity reduces the synergistic processes and interactions between rivers and their floodplains, and changes the distribution of waterbirds that rely on floodplains as foraging grounds. Recent river and wetland conservation and restoration efforts have been partially focused on reinstating the natural river-floodplain connectivity to ameliorate the ecological effects of regulation in river systems. However, in regions where human well-being is tightly linked with the cultivation of the floodplain (such as fisheries), management options are constrained and trade-offs among competing social, economic and ecological goals may be necessary for the wise use of wetlands. Poyang Lake in east central China includes numerous sub-lakes with different types of hydrological regulation; therefore, this lake may provide a useful context for exploring the likelihood of such trade-offs. In this study, we used multiyear simultaneous waterbird survey data together with habitat maps derived from satellite imagery for Poyang Lake to examine the variations in waterbird community structure and abundance within sub-lakes with different types of hydrological regulation. Using a Bayesian Markov chain Monte Carlo approach, we built generalized linear mixed models to explore the differences in wetland composition and waterbird abundance/diversity among three lake types (i.e. isolated, freely connected, and controlled) at community, guild and species levels. The results showed hydrological connectivity alteration clearly affects wintering waterbirds; in addition, the ecological benefits of a natural flow regime were most unambiguous at the community level. Nevertheless, little evidence exists to indicate that the lakes' ecological values as waterbird foraging grounds were compromised by partial regulation. That is, species richness and population size were comparable in naturally connected and controlled lakes. Our results suggest that, with carefully designed management plans, a delicate balance between waterbird conservation and development can be accomplished in large river floodplains. Crown Copyright © 2016. Published by Elsevier B.V. All rights reserved.

Understanding controls on redox processes in floodplain sediments of the Upper Colorado River Basin

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

Noël, Vincent; Boye, Kristin; Kukkadapu, Ravi K.

Floodplains, heavily used for water supplies, housing, agriculture, mining, and industry, are important repositories of organic carbon, nutrients, and metal contaminants. The accumulation and release of these species is often mediated by redox processes. By understanding the physicochemical, hydrological, and biogeochemical controls on the distribution and variability of sediment redox conditions we can develop conceptual and numerical models of contaminant transport within floodplains. The Upper Colorado River Basin (UCRB) is impacted by former uranium and vanadium ore processing, resulting in contamination by V, Cr, Mn, As, Se, Mo and U. Previous authors have suggested that sediment redox activity occurring withinmore » organic carbon-enriched bodies located below the groundwater level may be regionally important to the maintenance and release of contaminant inventories, particularly uranium. To help assess this hypothesis, vertical distributions of Fe and S redox states and sulfide mineralogy were assessed in sediment cores from three floodplain sites spanning a 250 km transect of the central UCRB. Our results support the hypothesis that organic-enriched reduced sediments are important zones of biogeochemical activity within UCRB floodplains. Furthermore, we found that the presence of organic carbon, together with pore saturation, are the key requirements for maintaining reducing conditions, which were dominated by sulfate-reduction products. Sediment texture was found to be of secondary importance and to moderate the response of the system to external forcing, such as oxidant diffusion. Consequently, fine-grain sediments are relatively resistant to oxidation in comparison to coarser-grained sediments. Exposure to oxidants consumes precipitated sulfides, with a disproportionate loss of mackinawite (FeS) as compared to the more stable pyrite. The accompanying loss of redox buffering capacity creates the potential for release of sequestered radionuclides and metals. Because of their redox reactivity and stores of metals, C, and N, organic-enriched sediments are likely to be important to nutrient and contaminant mobility within UCRB floodplain aquifers.« less

Supplemental water releases for fisheries restoration in a Brazilian floodplain River: A conceptual model

USGS Publications Warehouse

Godinho, Alexandre L.; Kynard, B.; Martinez, C.B.

2007-01-01

Highly productive floodplain rivers in Brazil and elsewhere provide livelihood and recreational fishing for millions of people around the world, but damming and controlled water discharge are a threat to these valuable ecosystems. Supplemental water releases (SWRs) at a dam are increasingly used for restoring fisheries productivity in many floodplain rivers. We proposed a conceptual model for a hypothetical water release to enhance fisheries using Tre??s Marias Reservoir (TMR) on the Sa??o Francisco River (SFR), Brazil. The information needed by the model follows: (i) Biologically, what is the best release date? (ii) How much water will be released? (iii) What is the pattern of impoundment and how much impounded water will be released? (iv) What is the lost revenue to the power plant associated with SWR? (v) What is the relationship between river discharge and the area of floodplain that is flooded? (vi) What is the relationship between SWR and fisheries value? Ichthyoplankton studies in the SFR showed a clear positive relationship between fish density and water level (WL). While the relationship between WL and floodplain area flooded and recruitment is not known, we concluded the best date for release is when there is a natural flood, which naturally triggers fish spawning and the SWR will add to the natural flood and cover a greater floodplain area. The released volume will range from 0.302km3 to 2.192 km3, depending on SWR duration. In most years from 1976 to 2003, TMR impounded enough water for SWR only in the second half of the fish-spawning season (January-March). Lost revenue at TMR depended on release volume and ranged from US$ 0.493 million to US$ 3.452 million for the actual power rate. However, SWR could increase commercial fisheries income an estimated US$ 4.468 million. We forecast that SWR can bring fisheries benefits that surpass the lost revenue.

Effects of hydrologic connectivity and land use on floodplain sediment accumulation at the Savannah River Site, South Carolina.

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

Eddy, Jeremy Edward

Floodplains, and the sediment accumulating naturally on them,are important to maintain stream water quality and serve as sinks for organic and inorganic carbon. Newer theories contend that land use and hydrologic connectivity (water-mediated transport of matter, energy, and/or organisms within or between elements of the hydrologic cycle) play important roles in determining sediment accumulation on floodplains. This study hypothesizes that changes in hydrologic connectivity have a greater impact on floodplain sediment accumulation than changes in land use. Nine sediment cores from seven sub-basins were collected from the Savannah River Site (SRS), South Carolina, and processed for grain-size, radionuclide dating (7Be,more » 137Cs, 210Pb), particulate organic carbon (POC), and microscopy. Historical records, including aerial and satellite imagery,were used to identify anthropogenic disturbances in the sub-basins, as well as to calculate the percentages of natural vegetation land cover at the SRS in 1951, and 2014. LiDAR and field survey data identified 251 flow impediments, measured elevation, and recorded standard stream characteristics (e.g., bank height) that canaffect hydrologic connectivity. Radionuclide dating was used to calculate sediment mass accumulation rates (MARs) and linear accumulation rates (LARs) for each core. Results indicate that sedimentation rates have increased across all SRS sub-basins over the past 40-50 years, shortly after site restoration and recovery efforts began.Findings show that hydrologic connectivity proxies (i.e., stream characteristics and impediments) have stronger relationships to MARs and LARs than the land use proxy (i.e., vegetation cover), confirming the hypothesis. Asstream channel depth and the number of impediments increase,floodplain sedimentation rates also increase. This knowledge can help future stream restoration efforts by focusing resources to more efficiently attain stated goals, particularly in terms of floodplain sediment retention.« less

Nitrogen sources, transport and processing in peri-urban floodplains.

PubMed

Gooddy, D C; Macdonald, D M J; Lapworth, D J; Bennett, S A; Griffiths, K J

2014-10-01

Peri-urban floodplains are an important interface between developed land and the aquatic environment and may act as a source or sink for contaminants moving from urban areas towards surface water courses. With increasing pressure from urban development the functioning of floodplains is coming under greater scrutiny. A number of peri-urban sites have been found to be populated with legacy landfills which could potentially cause pollution of adjacent river bodies. Here, a peri-urban floodplain adjoining the city of Oxford, UK, with the River Thames has been investigated over a period of three years through repeated sampling of groundwaters from existing and specially constructed piezometers. A nearby landfill has been found to have imprinted a strong signal on the groundwater with particularly high concentrations of ammonium and generally low concentrations of nitrate and dissolved oxygen. An intensive study of nitrogen dynamics through the use of N-species chemistry, nitrogen isotopes and dissolved nitrous oxide reveals that there is little or no denitrification in the majority of the main landfill plume, and neither is the ammonium significantly retarded by sorption to the aquifer sediments. A simple model has determined the flux of total nitrogen and ammonium from the landfill, through the floodplain and into the river. Over an 8 km reach of the river, which has a number of other legacy landfills, it is estimated that 27.5 tonnes of ammonium may be delivered to the river annually. Although this is a relatively small contribution to the total river nitrogen, it may represent up to 15% of the ammonium loading at the study site and over the length of the reach could increase in-stream concentrations by nearly 40%. Catchment management plans that encompass floodplains in the peri-urban environment need to take into account the likely risk to groundwater and surface water quality that these environments pose. Crown Copyright © 2014. Published by Elsevier B.V. All rights reserved.

Identifying sources of acidity and spatial distribution of acid sulfate soils in the Anglesea River catchment, southern Australia

NASA Astrophysics Data System (ADS)

Wong, Vanessa; Yau, Chin; Kennedy, David

2015-04-01

Globally, coastal and estuarine floodplains are frequently underlain by sulfidic sediments. When exposed to oxygen, sulfidic sediments oxidise to form acid sulfate soils, adversely impacting on floodplain health and adjacent aquatic ecoystems. In eastern Australia, our understanding of the formation of these coastal and estuarine floodplains, and hence, spatial distribution of acid sulfate soils, is relatively well established. These soils have largely formed as a result of sedimentation of coastal river valleys approximately 6000 years BP when sea levels were one to two metres higher. However, our understanding of the evolution of estuarine systems and acid sulfate soil formation, and hence, distribution, in southern Australia remains limited. The Anglesea River, in southern Australia, is subjected to frequent episodes of poor water quality and low pH resulting in closure of the river and, in extreme cases, large fish kill events. This region is heavily reliant on tourism and host to a number of iconic features, including the Great Ocean Road and Twelve Apostles. Poor water quality has been linked to acid leakage from mining activities and Tertiary-aged coal seams, peat swamps and acid sulfate soils in the region. However, our understanding of the sources of acidity and distribution of acid sulfate soils in this region remains poor. In this study, four sites on the Anglesea River floodplain were sampled, representative of the main vegetation communities. Peat swamps and intertidal marshes were both significant sources of acidity on the floodplain in the lower catchment. However, acid neutralising capacity provided by carbonate sands suggests that there are additional sources of acidity higher in the catchment. This pilot study has highlighted the complexity in the links between the floodplain, upper catchment and waterways with further research required to understand these links for targeted acid management strategies.

Patterns of floodplain sediment deposition along the regulated lower Roanoke River, North Carolina: annual, decadal, centennial scales

USGS Publications Warehouse

Hupp, Cliff R.; Schenk, Edward R.; Kroes, Daniel; Willard, Debra A.; Townsend, Phil A.; Peet, Robert K.

2015-01-01

The lower Roanoke River on the Coastal Plain of North Carolina is not embayed and maintains a floodplain that is among the largest on the mid-Atlantic Coast. This floodplain has been impacted by substantial aggradation in response to upstream colonial and post-colonial agriculture between the mid-eighteenth and mid-nineteenth centuries. Additionally, since the mid-twentieth century stream flow has been regulated by a series of high dams. We used artificial markers (clay pads), tree-ring (dendrogeomorphic) techniques, and pollen analyses to document sedimentation rates/amounts over short-, intermediate-, and long-term temporal scales, respectively. These analyses occurred along 58 transects at 378 stations throughout the lower river floodplain from near the Fall Line to the Albemarle Sound. Present sediment deposition rates ranged from 0.5 to 3.4 mm/y and 0.3 to 5.9 mm/y from clay pad and dendrogeomorphic analyses, respectively. Deposition rates systematically increased from upstream (high banks and floodplain) to downstream (low banks) reaches, except the lowest reaches. Conversely, legacy sediment deposition (A.D. 1725 to 1850) ranged from 5 to about 40 mm/y, downstream to upstream, respectively, and is apparently responsible for high banks upstream and large/wide levees along some of the middle stream reaches. Dam operations have selectively reduced levee deposition while facilitating continued backswamp deposition. A GIS-based model predicts 453,000 Mg of sediment is trapped annually on the floodplain and that little watershed-derived sediment reaches the Albemarle Sound. Nearly all sediment in transport and deposited is derived from the channel bed and banks. Legacy deposits (sources) and regulated discharges affect most aspects of present fluvial sedimentation dynamics. The lower river reflects complex relaxation conditions following both major human alterations, yet continues to provide the ecosystem service of sediment trapping.

Human alterations, dynamic equilibrium, and riparian ecosystem responses along selected rivers in Tuscany, Italy (Invited)

NASA Astrophysics Data System (ADS)

Hupp, C. R.; Rinaldi, M.

2010-12-01

Many, if not most, streams have been mildly to severely affected by human disturbance, which complicates efforts to understand riparian ecosystems. Mediterranean regions have a long history of human influences including: dams, stream channelization, mining of sediment, and levee /canal construction. Typically these alterations reduce the ecosystem services that functioning floodplains provide and may negatively impact the natural ecology of floodplains through reductions in suitable habitats, biodiversity, and nutrient cycling. Additionally, human alterations typically shift affected streams away from a state of natural dynamic equilibrium, where net sediment deposition is approximately in balance with net erosion. Lack of equilibrium typically affects the degree to which floodplain ecosystems are connected to streamflow regime. Low connectivity, usually from human- or climate-induced incision, may result in reduced flow on floodplains and lowered water tables. High connectivity may result in severe sediment deposition. Connectivity has a direct impact on vegetation communities. Riparian vegetation distribution patterns and diversity relative to various fluvial geomorphic channel patterns, landforms, and processes are described and interpreted for selected rivers of Tuscany, Central Italy; with emphasis on channel evolution following human impacts. Multivariate analysis reveals distinct quantitative vegetation patterns related to six fluvial geomorphic surfaces. Analysis of vegetation data also shows distinct associations of plants with adjustment processes related to the stage of channel evolution. Plant distribution patterns coincide with disturbance/landform/soil moisture gradients. Species richness increases from channel bed to terrace and on heterogeneous riparian areas, while species richness decreases from moderate to intense incision and from low to intense narrowing. As a feedback mechanism, woody vegetation in particular may facilitate geomorphic recovery of floodplains by affecting sedimentation dynamics. Identification and understanding of critical fluvial parameters related to floodplain connectivity (e.g. stream gradient, grain-size, and hydrography) and spatial and temporal sediment deposition/erosion process trajectories should facilitate management efforts to retain and/or regain important ecosystem services.

Insights into organic carbon oxidation potential during fluvial transport from laboratory and field experiments

NASA Astrophysics Data System (ADS)

Scheingross, J. S.; Dellinger, M.; Eglinton, T. I.; Fuchs, M. C.; Golombek, N.; Hilton, R. G.; Hovius, N.; Lupker, M.; Repasch, M. N.; Sachse, D.; Turowski, J. M.; Vieth-Hillebrand, A.; Wittmann, H.

2017-12-01

Over geologic timescales, the exchange of organic carbon (OC) between the atmosphere, hydropshere, biosphere and geosphere can be a major control on atmospheric carbon dioxide concentrations. The carbon fluxes from the oxidation of rock-derived OC (a CO2 source) and erosion, transport, and burial of biospheric OC (a potential CO2 sink) during fluvial transit are approximately the same order of magnitude or larger than those from silicate weathering. Despite field data showing increasing oxidation of OC moving downstream in lowland rivers, it is unclear if losses occur primarily during active fluvial transport, where OC is in continual motion within an aerated river, or during periods of temporary storage in river floodplains which may be anoxic. The unknown location of OC oxidation (i.e., river vs. floodplain) limits our ability to mechanistically link geochemical and geomorphic processes which are required to develop models capable of predicting OC losses, constrain carbon budgets, and unravel links between climate, tectonics, and erosion. To fill this knowledge gap, we investigated OC oxidation in controlled laboratory experiments and a simplified field setting. We performed experiments in annular flumes that simulate fluvial transport without floodplain storage, allowing mixtures of OC-rich and siliciclastic sediment to be transported for distances of 1000 km. Preliminary experiments exploring both rock-derived and biospheric OC sources show minimal OC oxidation during active river transport, consistent with the idea that the majority of OC loss occurs during transient floodplain storage. These results are also consistent with new field data collected in the Rio Bermejo, Argentina, a lowland river traversing 800 km with no tributary inputs, where aged floodplain deposits have 3 to 10 times lower OC concentrations compared to modern river sediments. Together our field data and experiments support the hypothesis that oxidation of OC occurs primarily during floodplain storage rather than fluvial transport.

Effects of dam construction and increasing pollutants on the ecohydrological evolution of a shallow freshwater lake in the Yangtze floodplain.

PubMed

Zeng, Linghan; McGowan, Suzanne; Cao, Yanmin; Chen, Xu

2018-04-15

Large river-floodplain systems which provide a variety of societal, economic and biological benefits are undergoing extensive and intensive human disturbance. However, floodplain lakes responses to multiple stressors are poorly understood. The Yangtze River and its floodplain which provide water and food resources for more than 300 million people are an important region in China. Hydrological regulation as well as socio-economic development have brought profound negative influence on this ecologically important area. To improve understanding of decadal-scale responses of floodplain lakes to multiple stressors, lake sediment proxies including particle size, geochemical elements, diatoms and chironomids were analysed in a lead-210 dated core from Futou Lake. The analyses show that dams constructed in 1935 and the early 1970s stabilized hydrological conditions in Futou Lake and impeded the interaction with the Yangtze River, resulting in a decrease in major elements (e.g., Mg, Al, Fe) transported into the lake and an increase of macrophyte-related chironomids (C. sylvestris-type, P. penicillatus-type and Paratanytarsus sp.). After the late 1990s, further decreases in major elements and increases in median grain size are attributed to the erosion of the Yangtze riverbed and declining supply of major elements-enriched sediments from the upper Yangtze caused by the impoundment of the Three Gorges Dam. Chironomid and diatom assemblages indicate that hydrological stabilization caused by dam constructions stimulated the growth of macrophytes, which may be important in buffering against an ecosystem state change towards a phytoplankton-dominated and turbid state with ongoing eutrophication. However, a recent increase in Zn, TP and the emergence of eutrophic diatom and chironomid species indicate initial signs of water quality deterioration which may be related to the combined effects of hydrological stabilization and aquaculture. Over all, the sediment record from Futou Lake emphasizes the importance of interactions between hydrological change and pollutant loads in determining floodplain lake ecosystem state. Copyright © 2017 Elsevier B.V. All rights reserved.

Hydrological Controls of Riverine Ecosystems of the Napo River (Amazon Basin): Implications for the Management and Conservation of Biodiversity

NASA Astrophysics Data System (ADS)

Celi, J. E.; Hamilton, S. K.

2013-12-01

Scientific understanding of neotropical floodplains comes mainly from work on large rivers with predictable seasonal flooding regimes. Less studied rivers and floodplains on the Andean-Amazon interface are distinct in their hydrology, with more erratic flow regimes, and thus ecological roles of floodplain inundation differ in those ecosystems. Multiple and unpredictable flooding events control inundation of floodplains, with important implications for fish and wildlife, plant communities, and human activities. Wetlands along the river corridor exist across a continuum from strong river control to influence only by local waters, with the latter often lying on floodplain paleoterraces. The goal of this study was to understand the hydrological interactions and habitat diversity of the Napo River, a major Amazon tributary that originates in the Andes and drains exceptionally biodiverse Andean foreland plains. This river system is envisioned by developers as an industrial waterway that would require hydrological alterations and affect floodplain ecosystems. Water level regimes of the Napo River and its associated environments were assessed using networks of data loggers that recorded time under water across transects extending inland from the river across more than 100 sites and for up to 5 years. These networks also included rising stage samplers that collected flood water samples for determination of their origin (i.e., Andean rivers vs. local waters) based on hydrochemical composition. In addition, this work entails a classification of aquatic environments of the Napo Basin using an object-oriented remote sensing approach to simultaneously analyze optical and radar satellite imagery and digital elevation models to better assess the extent and diversity of flooded environments. We found out a continuum of hydrological regimes and aquatic habitats along the Napo River floodplains that are linked to the river hydrology in different degrees. Overall, environments that are proximal or that have high hydrological connectivity are riverine controlled versus systems that are distal or that have less or no connectivity that rely on rainwater or local runoff as a source of flooding. Outcomes of this research gave us insight on the extent and diversity of aquatic habitats of the Napo River, the role that the river has on their ecohydrology, the potential effects of different hydrologic scenarios on these ecosystems, and the management measures that need to be considered to support conservation in the region.

Agriculture and the promotion of insect pests: rice cultivation in river floodplains and malaria vectors in The Gambia.

PubMed

Jarju, Lamin B S; Fillinger, Ulrike; Green, Clare; Louca, Vasilis; Majambere, Silas; Lindsay, Steven W

2009-07-27

Anthropogenic modification of natural habitats can create conditions in which pest species associated with humans can thrive. In order to mitigate for these changes, it is necessary to determine which aspects of human management are associated with the promotion of those pests. Anopheles gambiae, the main Africa malaria vector, often breeds in rice fields. Here the impact of the ancient practice of 'swamp rice' cultivation, on the floodplains of the Gambia River, on the production of anopheline mosquitoes was investigated. Routine surveys were carried out along 500 m transects crossing rice fields from the landward edge of the floodplains to the river during the 2006 rainy season. Aquatic invertebrates were sampled using area samplers and emergence traps and fish sampled using nets. Semi-field experiments were used to investigate whether nutrients used for swamp rice cultivation affected mosquito larval abundance. At the beginning of the rainy season rice is grown on the landward edge of the floodplain; the first area to flood with fresh water and one rich in cattle dung. Later, rice plants are transplanted close to the river, the last area to dry out on the floodplain. Nearly all larval and adult stages of malaria vectors were collected 0-100 m from the landward edge of the floodplains, where immature rice plants were grown. These paddies contained stagnant freshwater with high quantities of cattle faeces. Semi-field studies demonstrated that cattle faeces nearly doubled the number of anopheline larvae compared with untreated water. Swamp rice cultivation creates ideal breeding sites for malaria vectors. However, only those close to the landward edge harboured vectors. These sites were productive since they were large areas of standing freshwater, rich in nutrients, protected from fish, and situated close to human habitation, where egg-laying mosquitoes from the villages had short distances to fly. The traditional practice of 'swamp rice' cultivation uses different bodies of water on the floodplains to cultivate rice during the rainy season. A consequence of this cultivation is the provizion of ideal conditions for malaria vectors to thrive. As the demand for locally-produced rice grows, increased rice farming will generate great numbers of vectors; emphasizing the need to protect local communities against malaria.

Release of Mercury Mine Tailings from Mine Impacted Watersheds by Extreme Events Resulting from Climate Change

NASA Astrophysics Data System (ADS)

Rytuba, J. J.

2015-12-01

An increase in intensity and frequency of extreme events resulting from climate change is expected to result in extreme precipitation events on both regional and local scales. Extreme precipitation events have the potential to mobilize large volumes of mercury (Hg) mine tailings in watersheds where tailings reside in the floodplain downstream from historic Hg mines. The California Hg mineral belt produced one third of the worlds Hg from over 100 mines from the 1850's to 1972. In the absence of environmental regulations, tailings were disposed of into streams adjacent to the mines in order to have them transported from the mine site during storm events. Thus most of the tailings no longer reside at the mine site. Addition of tailings to the streams resulted in stream aggradation, increased over-bank flow, and deposition of tailings in the floodplain for up to 25 kms downstream from the mines. After cessation of mining, the decrease in tailings entering the streams resulted in degradation, incision of the streams into the floodplain, and inability of the streams to access the floodplain. Thus Hg tailings have remained stored in the floodplain since cessation of mining. Hg phases in these tailings consist of cinnabar, metacinnabar and montroydite based on EXAFS analysis. Size analysis indicates that Hg phases are fine grained, less than 1 um. The last regional scale extreme precipitation events to effect the entire area of the California Hg mineral belt were the ARkStorm events of 1861-1862 that occurred prior to large scale Hg mining. Extreme regional ARkStorm precipitation events as well as local summer storms, such as the July 2006 flood in the Clear Creek Hg mining district, are expected to increase in frequency and have the potential to remobilize the large volume of tailings stored in floodplain deposits. Although Hg mine remediation has decreased Hg release from mine sites in a period of benign climate, no remediation efforts have addressed the large source of Hg residing in floodplain deposits. This Hg source in a period of climate change poses a significant environmental risk to aquatic systems downstream from Hg mine-impacted watersheds. An extreme ARkStorm event is estimated to potentially remobilize an amount of Hg equivalent to that released in the past during the peak period of unregulated Hg mining in California.

Sensitivity analysis of a soil-vegetation-atmosphere transfer (SVAT) model parameterised for a British floodplain meadow

NASA Astrophysics Data System (ADS)

Morris, P. J.; Verhoef, A.; Van der Tol, C.; Macdonald, D.

2011-12-01

Rationale: Floodplain meadows are highly species-rich grassland ecosystems, unique in that their vegetation and soil structures have been shaped and maintained by ~1,000 yrs of traditional, low-intensity agricultural management. Widespread development on floodplains over the last two centuries has left few remaining examples of these once commonplace ecosystems and they are afforded high conservation value by British and European agencies. Increased incidences and severity of summer drought and winter flooding in Britain in recent years have placed floodplain plant communities under stress through altered soil moisture regimes. There is a clear need for improved management strategies if the last remaining British floodplain meadows are to be conserved under changing climates. Aim: As part of the Floodplain Underground Sensors Experiment (FUSE, a 3-year project funded by the Natural Environment Research Council) we aim to understand the environmental controls over soil-vegetation-atmosphere transfers (SVAT) of water, CO2 and energy at Yarnton Mead, a floodplain meadow in southern England. An existing model, SCOPE (Soil Canopy Observation, Photochemistry and Energy fluxes; van der Tol et al., 2009), uses remotely-sensed infrared radiance spectra to predict heat and water transfers between a vegetation canopy and the atmosphere. We intend to expand SCOPE by developing a more realistic, physically-based representation of water, gas and energy transfers between soil and vegetation. This improved understanding will eventually take the form of a new submodel within SCOPE, allowing more rigorous estimation of soil-canopy-atmosphere exchanges for the site using predominantly remotely-sensed data. In this context a number of existing SVAT models will be tested and compared to ensure that only reliable and robust underground model components will be coupled to SCOPE. Approach: For this study, we parameterised an existing and widely-used SVAT model (CoupModel; Jansson, 2011) for our study site and analysed the model's sensitivity to a comprehensive set of soil/plant biophysical processes and parameter values. Findings: The sensitivity analysis indicates those processes and parameters most important to soil-vegetation-atmosphere transfers at the site. We use the outcomes of the sensitivity analysis to indicate directly the desired structure of the new SCOPE submodel. In addition, existing soil-moisture, soil matric-potential and meteorological data for the site indicate that evapotranspiration is heavily water-limited during summer months, although soil moisture and soil matric-potential data alone provide very little explanation of the ratio of potential to actual evapotranspiration. A mechanistic representation of stomatal resistance and its response to short-term changes in meteorological conditions - independent of soil moisture status - will also likely improve SCOPE's predictions of heat and water transfers. Ultimately our work will contribute to improved understanding and management of floodplain meadows in Britain and elsewhere.

The use of portable instruments for mapping contaminants in the floodplain of the Ploucnice River (Czech Republic)

NASA Astrophysics Data System (ADS)

Elznicova, Jitka; Sikora, Martin; Slaba, Eva; Popelka, Jan; Hosek, Michal; Matys Grygar, Tomas

2015-04-01

The Ploucnice River (the Czech Republic) was contaminated by uranium mining in the areas of Hamr na Jezere and Straz pod Ralskem mainly in 1971-1987. The pollutants are now deposited all over the floodplain of the river. In 2005 the aerial mapping of radioactive pollution in the floodplain of the Ploucnice River was performed at a height of 80 m above the ground in grid 250 x 250 m. That survey showed uneven, highly localised deposition of gamma-emitting nuclides along nearly the entire reach of the Ploucnice River. We studied several of those radioactivity hotspots 10-25 km downstream from the uranium mining area in aim to understand the reasons for that heterogeneity. The contamination of the floodplain was analysed mainly by two portable (handheld) instruments. The gamma-spectrometer DISA 400A was used for measuring the total surface gamma activity (main target nuclide was Ra-226). Very effective was also the use of portable X-ray fluorescence spectrometer (XRF) Olympus Innov-X (DELTA Premium), which provides fast analysis of more than 30 elements, such as pollutants (Ba, Ni, Pb, U and Zn) and grain-size sensitive lithogenic elements (Al, Si, Zr, Rb). Besides pollution mapping, XRF also allows for mapping sediment lithology using Al/Si or Rb/Zr element ratios (both proportional to the percentage of fine fraction). The field gamma spectrometry and XRF was performed with points 2-30 meters spaced, which revealed that hotspots according to low resolution (250 m) aerial mapping is composed of one or several strongly polluted areas with sizes up to several tens of metres. Similarly heterogeneous was also the distribution of sediment lithology in the floodplain. In some cases, micromorphology of the floodplain, formed mainly by the past meander abandonments and channel shifts was responsible for the heterogeneity of the pollution. To understand the floodplain development we used old maps and aerial photographs. The Czech Republic has an extensive archive of historical aerial photos from 1938 and then from 1953 to the present with 5 or 10 years intervals. The maximal contamination was found in places where there was a meander cuts shortly after a flood (>Q50) in1981. Additionally we used digital elevation model (DEM), created from a laser scanning (LIDAR) dataset DMR 5G obtained in 2010 with nominal altitudinal precision of 0.18 m in open terrain and 0.3 in forested terrain. Our study demonstrated that very detailed, high-resolution analysis of pollution distribution in the floodplain, achievable by portable analytical instruments and interpreted on the base of micro-geomorphology analysis, help to better understand the sedimentation patterns and sediment reworking in fluvial systems.

Influences of harvesting on functions of floodplain forests associated with low-order, blackwater streams

Treesearch

B.G. Lockaby; R.H. Jones; R.G. Clawson; J.S. Meadows; John A. Stanturf; F.C. Thornton

1997-01-01

The influence of both aerial and ground-based harvesting on functions of forested floodplains of low-order streams was studied during a two-year period. The study sites were associated with low-order, blackwater streams with infertile and primarily organic soils. Responses to harvesting were assessed in relation to water quality, denitrification, hydrology,...

Understory vegetation as an indicator for floodplain forest restoration in the Mississippi River Alluvial Valley, U.S.A

Treesearch

Diane De Steven; Stephen P. Faulkner; Bobby D. Keeland; Michael J. Baldwin; John W. McCoy; Steven C. Hughes

2015-01-01

In the Mississippi River Alluvial Valley (MAV), complete alteration of river-floodplain hydrology allowed for widespread conversion of forested bottomlands to intensive agriculture, resulting in nearly 80% forest loss. Governmental programs have attempted to restore forest habitat and functions within this altered landscape by the methods of tree planting (...

Effect of vegetation structure on breeding territory selection by red-winged blackbirds in a floodplain forest restoration project

Treesearch

Maria A. Furey; Dirk E. Burhans; Hong He; Michael A. Gold; Bruce E. Cutter

2003-01-01

Our research investigates the role of vegetation structure in the selection of breeding territories by red-winged blackbirds (Agelaius phoeniceus) in two floodplain oak-restoration sites. Perches are used extensively by red-winged blackbirds in territorial display during the spring (Yasukawa and Searcy 1995). We hypothesized that breeding territory...

Ecology of bottomland oaks in the southeastern United states

Treesearch

Emile S. Gardiner

2001-01-01

0aks (Querczrs spp.) are among the most ecologically and economically valued trees of the floodplain forests which occupy the river valleys that dissect the Gulf and Atlantic coastal plains of the southeastem United States. In these floodplain forests, several species from the sections Quercus and Lobarae are commonly found distributed along a gradient of sites ranging...

39 CFR 776.7 - Lease, easement, right-of-way, or disposal of property to non-federal parties.

Code of Federal Regulations, 2010 CFR

2010-07-01

... 39 Postal Service 1 2010-07-01 2010-07-01 false Lease, easement, right-of-way, or disposal of property to non-federal parties. 776.7 Section 776.7 Postal Service UNITED STATES POSTAL SERVICE ENVIRONMENTAL REGULATIONS FLOODPLAIN AND WETLAND PROCEDURES Floodplain Management § 776.7 Lease, easement, right...

Effects of land use practices on neotropical migratory birds in bottomland hardwood forests

Treesearch

David N. Pashley; Wylie C. Barrow

1993-01-01

Description of the system: Bottomland hardwood forests (including bald cypress and tupelo swamp forests) are historically the dominant natural community of riverine floodplains of the southeastern United States. Their greatest single expanse was in the 21 million acre floodplain of the lower Mississippi River Valley from southern Illinois to coastal marshes along the...

24 CFR 55.10 - Environmental review procedures under 24 CFR parts 50 and 58.

Code of Federal Regulations, 2014 CFR

2014-04-01

..., Department of Housing and Urban Development FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS Application of Executive Orders on Floodplain Management and Protection of Wetlands § 55.10 Environmental review procedures... Environmental Policy Act of 1969 (NEPA) (42 U.S.C. 4321 et seq.), and 24 CFR part 50 or part 58, compliance with...

24 CFR 55.28 - Use of individual permits under section 404 of the Clean Water Act for HUD Executive Order 11990...

Code of Federal Regulations, 2014 CFR

2014-04-01

... section 404 of the Clean Water Act for HUD Executive Order 11990 processing where all wetlands are covered... of Housing and Urban Development FLOODPLAIN MANAGEMENT AND PROTECTION OF WETLANDS Procedures for Making Determinations on Floodplain Management and Protection of Wetlands § 55.28 Use of individual...

Tree Seedlings Establishment Across a Hydrologic Gradient in a Bottomland Restoration

Treesearch

Randall K. Kolka; Carl C. Trettin; E.A. Nelson; W.H. Conner

1998-01-01

Seedling establishment and survival on the Savannah River Site in South Carolina is being monitored as part of the Pen Branch Bottomland Restoration Project. Bottomland tree species were planted from 1993-1995 across a hydrologic gradient which encompasses the drier upper floodplain corridor, the lower floodplain corridor and the continuously inundated delta. Twelve...

Invertabrates Associated with Woody Debris in a Southeastern U.S. Forested Floodplain Wetland

Treesearch

Amy Braccia; Darold P. Batzer

2001-01-01

Woody debris is an ecologically important resource in upland forests and stream ecosystems. Although much is known about invertebrate-woody debris interactions in forests and streams, little information exists for forested wetlands. In this study, invertebrates associated with woody debris in a Southeastern U. S. forested floodplain are described and factors that shape...

Belowground Nutrient Dynamics Following Three Harvest Intensities on the Pearl River Floodplain, Mississippi

Treesearch

E.B. Schilling; B.G. Lockaby; Robert Rummer

1999-01-01

Abstract: The influence of clear and partial cut harvests on belowground nutrient cycling processes was examined on the Pearl River floodplain, Mississippi. Foci examined by this study included fine root biomass and detritus, fine root production, fine root nutrient contents, soil respiration rates, and microbial biomass C, N, and P during the first...

Spatial and Temporal Patterns of Nitrification Rates in Forested Floodplain Wetland Soils of Upper Mississippi River Pool 8, Journal Article

EPA Science Inventory

Overbank flooding is thought to be a critical process controlling nitrogen retention and cycling. In this study we investigated the effects of season and flood frequency on soil nitrification rates at ten sites in forested floodplains of Upper Mississippi River, Pool 8...A rough ...

Riparian valley oak (Quercus lobata) forest restoration on the middle Sacramento River, California

Treesearch

F. Thomas Griggs; Gregory H. Golet

2002-01-01

In 1989 The Nature Conservancy initiated a riparian horticultural restoration program on the floodplain of the middle Sacramento River, California. At nearly all restoration sites Valley oak (Quercus lobata Nee) comprised a major component of the planting design. Valley oaks are a keystone tree species of lowland floodplain habitats in California...

The temporal distribution and carbon storage of large oak wood in streams and floodplain deposits

Treesearch

Richard P. Guyette; Daniel C. Dey; Michael C. Stambaugh

2008-01-01

We used tree-ring dating and 14C dating to document the temporal distribution and carbon storage of oak (Quercus spp.) wood in trees recruited and buried by streams and floodplains in northern Missouri, USA. Frequency distributions indicated that oak wood has been accumulating in Midwest streams continually since at least the...

75 FR 34720 - Notice of Intent To Prepare an Environmental Impact Statement and To Conduct Public Scoping...

Federal Register 2010, 2011, 2012, 2013, 2014

2010-06-18

.... Requests to speak at any one or more public scoping meeting(s) should be received by Dr. Jerry Pell at the... Statement and To Conduct Public Scoping Meetings, and Notice of Floodplains and Wetlands Involvement... an Environmental Impact Statement (EIS) and to conduct Public Scoping Meetings; Notice of Floodplains...

Litterfall in the hardwood forest of a minor alluvial-floodplain

Treesearch

Calvin E. Meier; John A. Stanturf; Emile S. Gardiner

2006-01-01

within mature deciduous forests, annual development of foliar biomass is a major component of aboveground net primary production and nutrient demand. As litterfall, this same foliage becomes a dominant annual transfer of biomass and nutrients to the detritus pathway. We report litterfall transfers of a mature bottomland hardwood forest in a minor alluvial-floodplain...

Restoring Oaks in the Missouri River Floodplain

Treesearch

Dan Dey; John Kabrick; Jennifer Grabner; Mike Gold

2001-01-01

Restoration of native vegetation and hydrologic regimes in the Mississippi and Missouri River floodplains is problematic because they are among the most altered ecosystems in North America (Noss et al. 1995), and because of the competing demands placed on these river ecosystems by commercial, private and social interests. Since the 1780s, more than half (53 percent) of...

Is the community of fish gill parasites structured in a Neotropical floodplain?

PubMed

Bellay, Sybelle; Takemoto, Ricardo Massato; Oliveira, Edson Fontes

2012-03-01

Sixty-one specimens of the piranha Serrasalmus marginatus Valenciennes, 1837 were analyzed, aiming at assessing the community structure of their gill parasites. The samples were collected in lagoons of the Paraná, Ivinheima and Baia Subsystems within the Upper Paraná River Floodplain (Brazil). Host size and sex had little or no influence on the abundance and prevalence of parasites. The organization of the gill parasite infracommunities of S. marginatus was significantly non-random according to null models and ordination analyses. In general, parasite infrapopulations were not affected by interspecific associations or host characteristics (e.g. size, sex), what highlights the importance of local habitat characteristics to community organization of gill parasites of S. marginatus in the Upper Paraná River Floodplain.

A meeting of the waters: interdisciplinary challenges and opportunities in tidal rivers

USGS Publications Warehouse

Ensign, Scott H.; Noe, Gregory B.; Hupp, Cliff R.; Fagherazzi, Sergio

2012-01-01

At the interface of estuarine tides and freshwater rivers lie wetland and aquatic ecosystems, which experience dramatic effects of sea level rise. There, nontidal channels and riparian floodplains are transforming into tidal ecosystems, and tidal freshwater ecosystems are receiving increasing salinity. These river-floodplain systems have both fluvial characteristics, including meandering channels and expansive floodplain forests, and estuarine characteristics, including tides and intertidal wetlands [see Barendregt et al., 2009; Conner et al., 2007, and references therein]. Because tidal rivers lie at the disciplinary divide between fluvial and estuarine science, a knowledge gap has developed in scientists' understanding of the geomorphic and biogeochemical response of these environments to sea level rise, climate change, and anthropogenically driven variations in watershed exports.

Using remote sensing data to assess salmon habitat status in rivers and floodplains of Puget Sound, USA

NASA Astrophysics Data System (ADS)

Beechie, T. J.; Pess, G. R.; Hall, J.; Timpane-Padgham, B.; Stefankiv, O.; Liermann, M. C.; Fresh, K.; Rowse, M.

2015-12-01

Natural processes create dynamic habitat features in large rivers and floodplains, and past land uses that restrict fluvial processes have altered habitat conditions in those environments in Puget Sound, USA. As a result, Chinook salmon and steelhead are listed as threatened species under the US Endangered Species Act (ESA). To help restore these salmon populations, restoration actions often focus on removing constraints on natural processes to restore fluvial dynamics and ultimately restore critical salmon habitats on floodplains. An important aspect of this restoration effort is monitoring whether habitat conditions are improving as anticipated, yet there are currently few protocols available for monitoring trends in large river and floodplain habitats. We identified several remote-sensing metrics that are indicators of salmon habitat condition, and developed repeatable protocols for measuring those metrics. We then tested their sensitivity to land use change by comparing habitat conditions among land cover classes (developed, agriculture, forested, and mixed). As expected, metrics of habitat complexity or condition such as side-channel length, node density, wood jam area, or riparian buffer widths were highest in forested sites and lowest in agriculture and urban sites. By contrast, percent disconnected floodplain and percent armored banks were highest in developed sites and lowest in forested sites. Our results indicate that remote sensing metrics are sensitive enough to detect differences in habitat status among land cover classes, and therefore help us understand the impact of various land uses on habitat conditions. However, detecting trends in habitat condition through time may be difficult because magnitudes of change through time are very small.

Hierarchical Bayesian method for mapping biogeochemical hot spots using induced polarization imaging

DOE PAGES

Wainwright, Haruko M.; Flores Orozco, Adrian; Bucker, Matthias; ...

2016-01-29

In floodplain environments, a naturally reduced zone (NRZ) is considered to be a common biogeochemical hot spot, having distinct microbial and geochemical characteristics. Although important for understanding their role in mediating floodplain biogeochemical processes, mapping the subsurface distribution of NRZs over the dimensions of a floodplain is challenging, as conventional wellbore data are typically spatially limited and the distribution of NRZs is heterogeneous. In this work, we present an innovative methodology for the probabilistic mapping of NRZs within a three-dimensional (3-D) subsurface domain using induced polarization imaging, which is a noninvasive geophysical technique. Measurements consist of surface geophysical surveys andmore » drilling-recovered sediments at the U.S. Department of Energy field site near Rifle, CO (USA). Inversion of surface time domain-induced polarization (TDIP) data yielded 3-D images of the complex electrical resistivity, in terms of magnitude and phase, which are associated with mineral precipitation and other lithological properties. By extracting the TDIP data values colocated with wellbore lithological logs, we found that the NRZs have a different distribution of resistivity and polarization from the other aquifer sediments. To estimate the spatial distribution of NRZs, we developed a Bayesian hierarchical model to integrate the geophysical and wellbore data. In addition, the resistivity images were used to estimate hydrostratigraphic interfaces under the floodplain. Validation results showed that the integration of electrical imaging and wellbore data using a Bayesian hierarchical model was capable of mapping spatially heterogeneous interfaces and NRZ distributions thereby providing a minimally invasive means to parameterize a hydrobiogeochemical model of the floodplain.« less

Quantifying suspended sediment dynamics in mega deltas using remote sensing data: A case study of the Mekong floodplains

NASA Astrophysics Data System (ADS)

Dang, Thanh Duc; Cochrane, Thomas A.; Arias, Mauricio E.

2018-06-01

Temporal and spatial concentrations of suspended sediment in floodplains are difficult to quantify because in situ measurements can be logistically complex, time consuming and costly. In this research, satellite imagery with long temporal and large spatial coverage (Landsat TM/ETM+) was used to complement in situ suspended sediment measurements to reflect sediment dynamics in a large (70,000 km2) floodplain. Instead of using a single spectral band from Landsat, a Principal Component Analysis was applied to obtain uncorrelated reflectance values for five bands of Landsat TM/ETM+. Significant correlations between the scores of the 1st principal component and the values of continuously gauged suspended sediment concentration, shown via high coefficients of determination of sediment rating curves (R2 ranging from 0.66 to 0.92), permit the application of satellite images to quantify spatial and temporal sediment variation in the Mekong floodplains. Estimated suspended sediment maps show that hydraulic regimes at Chaktomuk (Cambodia), where the Mekong, Bassac, and Tonle Sap rivers diverge, determine the amount of seasonal sediment supplies to the Mekong Delta. The development of flood prevention systems to allow for three rice crops a year in the Vietnam Mekong Delta significantly reduces localized flooding, but also prevents sediment (source of nutrients) from entering fields. A direct consequence of this is the need to apply more artificial fertilizers to boost agricultural productivity, which may trigger environmental problems. Overall, remote sensing is shown to be an effective tool to understand temporal and spatial sediment dynamics in large floodplains.

Variations in trace element geochemistry in the Seine River Basin based on floodplain deposits and bed sediments

USGS Publications Warehouse

Horowitz, A.J.; Meybeck, Michel; Idlafkih, Z.; Biger, E.

1999-01-01

Between 1990 and 1995 a series of bed sediment, suspended sediment and fresh floodplain samples were collected within the Seine River Basin, in France, to evaluate variations in trace element geochemistry. Average background trace element levels for the basin were determined from the collection and subsequent analyses of bed sediment samples from small rural watersheds and from a prehistoric (5000 BP) site in Paris. Concentrations are relatively low, and similar to those observed for fine-grained bed sediments from unaffected areas in the United States and Canada. However, the concentrations are somewhat higher than the reference levels presently adopted by French water authorities for areas north of the Seine Basin, which have similar bedrock lithologies. Downstream trace element variations were monitored in 1994 and 1995 using fresh surficial floodplain samples that were collected either as dried deposits a few days after peak discharge, or immediately after peak discharge (under ??? 30 cm of water). Chemical comparisons between fresh floodplain deposits, and actual suspended sediments collected during flood events, indicate that, with some caveats, the former can be used as surrogates for the latter. The floodplain sediment chemical data indicate that within the Seine Basin, from the relatively unaffected headwaters through heavily affected urban streams, trace element concentrations vary by as much as three orders of magnitude. These trace element changes appear to be the result of both increases in population as well as concomitant increases in industrial activity. This article is a US government work and is in the public domain in the United States.

Downstream reduction of rural channel size with contrasting urban effects in small coastal streams of southeastern Australia

NASA Astrophysics Data System (ADS)

Nanson, G. C.; Young, R. W.

1981-07-01

Although most streams show a downstream increase in channel size corresponding to a downstream increase in flood discharges, those flowing off the Illawarra escarpment of New South Wales show a marked reduction of channel size, accompanied by a down-stream increase in flood frequency in their lower reaches. Within the confined and steeply sloping valleys of the escarpment foothills, bed and bank sediments are relatively coarse and uncohesive, and channels increase in size, corresponding to increasing discharge downstream. However, once these streams emerge into more open rural valleys at lower slopes and are accompanied by extensive floodplains formed of fine cohesive sediment, there is a dramatic reduction in channel size. This decrease in channel size apparently results from a sudden decline in channel slope and associated stream power, the cohesive nature of downstream alluvium, its retention on the channel banks by a dense cover of pasture grasses, and the availability of an extensive floodplain to carry displaced floodwater. Under these conditions floodwaters very frequently spill out over the floodplain and the downstream channel-flow becomes a relatively unimportant component of the total peak discharge. This emphasizes the importance of these floodplains as a part of the total channel system. In situations where urban development has increased peak runoff and reduced the available area of effective floodplain, stream channels formed in this fine alluvium rapidly entrench and increase in cross-sectional area by 2-3 times. Minor man-induced channel alteration and maintenance appears to trigger this enlargement.

Patterns of forest succession and impacts of flood in the Upper Mississippi River floodplain ecosystem

USGS Publications Warehouse

Yin, Y.; Wu, Y.; Bartell, S.M.; Cosgriff, R.

2009-01-01

The widespread loss of oak-hickory forests and the impacts of flood have been major issues of ecological interest concerning forest succession in the Upper Mississippi River (UMR) floodplain. The data analysis from two comprehensive field surveys indicated that Quercus was one of the dominant genera in the UMR floodplain ecosystem prior to the 1993 flood and constituted 14% of the total number of trees and 28% of the total basal area. During the post-flood recovery period through 2006, Quercus demonstrated slower recovery rates in both the number of trees (4%) and basal area (17%). In the same period, Carya recovered greatly from the 1993 flood in terms of the number of trees (11%) and basal area (2%), compared to its minor status before the flood. Further analyses suggested that different species responded to the 1993 flood with varying tolerance and different succession strategies. In this study, the relation of flood-caused mortality rates and DBH, fm(d), can be expressed in negative exponential functions for each species. The results of this research also indicate that the growth functions are different for each species and might also be different between pre- and post-flood time periods. These functions indicate different survival strategies and emergent properties in responding to flood impacts. This research enhances our understanding of forest succession patterns in space and time in the UPR floodplain. And such understanding might be used to predict long-term impacts of floods on UMR floodplain forest dynamics in support of management and restoration. ?? 2009 Elsevier B.V.

Association between wetland disturbance and biological attributes in floodplain wetlands

USGS Publications Warehouse

Chipps, S.R.; Hubbard, D.E.; Werlin, K.B.; Haugerud, N.J.; Powell, K.A.; Thompson, John; Johnson, T.

2006-01-01

We quantified the influence of agricultural activities on environmental and biological conditions of floodplain wetlands in the upper Missouri River basin. Seasonally-flooded wetlands were characterized as low impact (non-disturbed) or high impact (disturbed) based on local land use. Biological data collected from these wetlands were used to develop a wetland condition index (WCI). Fourteen additional wetlands were sampled to evaluate the general condition of seasonally-flooded floodplain wetlands. Structural and functional attributes of macrophyte, algae, and macroinvertebrate communities were tested as candidate metrics for assessing biotic responses. The WCI we developed used six biological metrics to discriminate between disturbed and non-disturbed wetlands: 1) biomass of Culicidae larvae, 2) abundance of Chironomidae larvae, 3) macroinvertebrate diversity, 4) total number of plant species, 5) the proportion of exotic plant species, and 6) total number of sensitive diatom species. Disturbed wetlands had less taxa richness and species diversity and more exotic and nuisance (e.g., mosquitoes) species. Environmental differences between low and high impact wetlands included measures of total potassium, total phosphorus, total nitrogen, alkalinity, conductance, and sediment phosphorus concentration. Canonical analyses showed that WCI scores were weakly correlated (P = 0.057) with environmental variables in randomly selected wetlands. In addition, mean WCI score for random wetlands was higher than that for high impact wetlands, implying that floodplain wetlands were less impacted by the types of agricultural activities affecting high impact sites. Inter-year sampling of some wetlands revealed that WCI metrics were correlated in 2000 and 2001, implying that biological metrics provided useful indicators of disturbance in floodplain wetlands. ?? 2006, The Society of Wetland Scientists.

Groundwater salinity in a floodplain forest impacted by saltwater intrusion

NASA Astrophysics Data System (ADS)

Kaplan, David A.; Muñoz-Carpena, Rafael

2014-11-01

Coastal wetlands occupy a delicate position at the intersection of fresh and saline waters. Changing climate and watershed hydrology can lead to saltwater intrusion into historically freshwater systems, causing plant mortality and loss of freshwater habitat. Understanding the hydrological functioning of tidally influenced floodplain forests is essential for advancing ecosystem protection and restoration goals, however finding direct relationships between hydrological inputs and floodplain hydrology is complicated by interactions between surface water, groundwater, and atmospheric fluxes in variably saturated soils with heterogeneous vegetation and topography. Thus, an alternative method for identifying common trends and causal factors is required. Dynamic factor analysis (DFA), a time series dimension reduction technique, models temporal variation in observed data as linear combinations of common trends, which represent unexplained common variability, and explanatory variables. DFA was applied to model shallow groundwater salinity in the forested floodplain wetlands of the Loxahatchee River (Florida, USA), where altered watershed hydrology has led to changing hydroperiod and salinity regimes and undesired vegetative changes. Long-term, high-resolution groundwater salinity datasets revealed dynamics over seasonal and yearly time periods as well as over tidal cycles and storm events. DFA identified shared trends among salinity time series and a full dynamic factor model simulated observed series well (overall coefficient of efficiency, Ceff = 0.85; 0.52 ≤ Ceff ≤ 0.99). A reduced multilinear model based solely on explanatory variables identified in the DFA had fair to good results (Ceff = 0.58; 0.38 ≤ Ceff ≤ 0.75) and may be used to assess the effects of restoration and management scenarios on shallow groundwater salinity in the Loxahatchee River floodplain.

Conserving large-river fishes: Is the highway analogy an appropriate paradigm

USGS Publications Warehouse

Galat, D.L.; Zweimuller, I.

2001-01-01

A tenet of the flood pulse concept, the highway analogy, states that the mare channel of large floodplain rivers is used by fishes mainly as a route for gaining access to floodplain habitats. We examined this proposition by analyzing habitat use for freshwater fishes in 4 large rivers in the United States (Colorado, Columbia, Mississippi, Missouri) and 4 in Europe (Danube, Rhine, Rho??ne, Volga). Fish species from floodplain segments of each river were classified as fluvial specialist, fluvial dependent, and macrohabitat generalist based on literature and expert opinion. We also summarized the proportion of imperiled and introduced fishes present in each of these categories. The high proportion (mean ?? 1 SD = 29 ?? 17.5%) of fluvial specialist fishes inhabiting north-temperate large rivers was inconsistent with the highway analogy. Most members of the families Petromyzontidae, Acidpenseridae, Hiodontidae, Osmeridae, Salmonidae, and Gobiidae require flowing water during some life stage. Between 29 and 100% of the native fish assemblage was of conservation concern, and from 50 to 85% of these fishes required riverine habitats to complete their life cycles. Macrohabitat generalists are adapted to capitalize on floodplain habitats and composed from 44 to 96% of introduced fishes in the rivers studied. Habitat diversity inherent in main-channel complexes of unaltered large rivers and reestablished in regulated large rivers is essential to meet life-history needs of native fluvial fishes while discouraging expansion of introduced species. Restoration of north-temperate large rivers and their native fish fauna should incorporate the dynamic interplay among main channel, floodplain, and tributary habitats and processes.

Constructed impoundments in the floodplain: A source or sink for native prairie fishes, in particular the endangered Topeka shiner (Notropis topeka)?

USGS Publications Warehouse

Thomson, S.K.; Berry, C.R.; Niehus, C.A.; Wall, S.S.; ,

2005-01-01

Livestock watering holes (i.e., dugouts) are typically constructed in floodplains, yet the influence of dugouts on native prairie fishes is unknown. Such information is necessary for the effective management of native fishes, especially species of concern such as the endangered Topeka shiner (Notropis topeka). The goal of our study was to suggest technical guidelines for constructing floodplain wetlands that are compatible with stream fish resources. Specific objectives were to: determine the flood frequencies of the connection between streams and dugouts; determine fish community characteristics in floodplain dugouts; and, associate dugout characteristics with fish assemblages. A total of 20 dugouts within Six Mile Creek watershed, South Dakota, were surveyed seasonally (excluding winter) from fall of 2003 to fall of 2004. Dugouts were categorized according to their lateral floodplain placement (connectivity with the stream and flood frequency of the stream-dugout connection) and longitudinal placement across the watershed. Fishes were sampled in dugouts and adjacent stream reaches with seines and traps. The 21 species making up the stream and dugout fish assemblages were similar. Fish inhabited 65% of the dugouts; 30% contained Topeka shiners. Most fish inhabitance, and all Topeka shiner occurrences, were in dugouts that were headwater sites and were either directly connected to the stream or disconnected and frequently flooded (average 1 in 2 year event). Two dugouts in this latter category contained the most abundant, self-sustaining Topeka shiner populations. Constructing dugouts separate from the stream within frequently inundated zones can provide off-channel habitat for fishes.

Ecological implications of floods on the parasite communities of two freshwater catfishes in a Neotropical floodplain.

PubMed

Yamada, Priscilla de Oliveira Fadel; Yamada, Fabio Hideki; da Silva, Reinaldo José; Anjos, Luciano Alves Dos

2017-06-01

The parasite communities of two freshwater catfishes (Auchenipterus osteomystax and Trachelyopterus galeatus) were analyzed during the dry and rainy seasons in a Neotropical floodplain. The nature of river-floodplain systems places specific demands on parasite community structure, due to changes in the host environment. It was therefore hypothesized that flood conditions lead to an increase in the richness and abundance of fish parasites in the rainy season at the mouth of Aguapeí River floodplain. The Auchenipterus osteomystax parasite community was richer (11 vs. eight) in species than T. galeatus, although the latter exhibited a greater parasite burden (F1,108 = 126.99, P<0.0001). During the rainy season both host species demonstrated high levels of parasitism (least squared means ± SE = 1.69 ± 0.05 vs. 1.34 ± 0.05; F1,108 = 21.45, P<0.0001). Differences were found in the composition of the parasite species and the proportion of parasites for each host species and between each seasonal period. Flood conditions during the rainy season caused a change in the composition and structure of the parasitic communities. The results corroborate the hypothesis that floods are one of the most significant influences on shaping the parasite communities of fish in floodplains. Our greatest concern is the reduction these dynamics and effects bring about on local biota and, consequently, in host-parasite interaction. We would therefore like to take this opportunity to warn environmental agencies and hydroelectric companies about the importance of the conservation of the diversity of this location.

Vegetation composition, nutrient, and sediment dynamics along a floodplain landscape

USGS Publications Warehouse

Rybicki, Nancy B.; Noe, Gregory; Hupp, Cliff R.; Robinson, Myles

2015-01-01

Forested floodplains are important landscape features for retaining river nutrients and sediment loads but there is uncertainty in how vegetation influences nutrient and sediment retention. In order to understand the role of vegetation in nutrient and sediment trapping, we quantified species composition and the uptake of nutrients in plant material relative to landscape position and ecosystem attributes in an urban, Piedmont watershed in Virginia, USA. We investigated in situ interactions among vegetative composition, abundance, carbon (C), nitrogen (N) and phosphorus (P) fluxes and ecosystem attributes such as water level, shading, soil nutrient mineralization, and sediment deposition. This study revealed strong associations between vegetation and nutrient and sediment cycling processes at the plot scale and in the longitudinal dimension, but there were few strong patterns between these aspects at the scale of geomorphic features (levee, backswamp, and toe-slope). Patterns reflected the nature of the valley setting rather than a simple downstream continuum. Plant nutrient uptake and sediment trapping were greatest at downstream sites with the widest floodplain and lowest gradient where the hydrologic connection between the floodplain and stream is greater. Sediment trapping increased in association with higher herbaceous plant coverage and lower tree canopy density that, in turn, was associated with a more water tolerant tree community found in the lower watershed but not at the most downstream site in the watershed. Despite urbanization effects on the hydrology, this floodplain functioned as an efficient nutrient trap. N and P flux rates of herbaceous biomass and total litterfall more than accounted for the N and P mineralization flux rate, indicating that vegetation incorporated nearly all mineralized nutrients into biomass.

River stabilisation due to changing climate and vegetation during the late Quaternary in western Tasmania, Australia

NASA Astrophysics Data System (ADS)

Nanson, Gerald C.; Barbetti, Mike; Taylor, Gillian

1995-09-01

The Stanley River in western Tasmania, Australia, contains sub-fossil rainforest logs within the channel and floodplain. Of the more than 85 radiocarbon dates obtained, all but 3 date from 17 ka to the present and permit an interpretation of fluvial and related environmental changes over this period. Particular attention is focused on the interactive relationship between the river and its riparian rainforest. Following the Last Glacial Maximum, the Stanley River was a laterally active gravel-load system reworking most of its valley floor in the upstream reaches. With ameliorating conditions at the end of the Pleistocene, climate became less seasonal and flow regimes less energetic. Huon pines already present in the catchment, re-asserted themselves in the form of dense tree cover along the river banks and floodplains with basal floodplain deposition shifting from gravels to coarse sands and granules. By about 3.5 ka, a further change in climate reduced stream discharges substantially. As a result the channel reduced in size, transported finer sediment, became laterally stable, and the floodplain accreted with overbank deposits of sand and silt. Huon pines falling into the channel formed obstructions of woody debris, some surviving for 2 ka. These have reduced stream power and boundary shear stress, further contributing to channel stability. Generational sequences of Huon pines on the river banks, some extending back 1-2 ka, are additional evidence of this stability. Since the Pleistocene, changing climate and the re-establishment of dense riparian rainforest appear to have stabilised the river channels and floodplains of western Tasmania.