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United States Department of Agriculture

Agricultural Research Service

Research Project: TECHNOLOGIES FOR ASSESSING SEDIMENT MOVEMENT & THE INTEGRITY OF FLOOD CONTROL STRUCTURES, STREAMBANKS, & EARTHEN POND-LEVEES & EMBANKMENTS

Location: Watershed Physical Processes Research Unit

Title: Using lake sedimentation rates to quantify the effectiveness of erosion control in watersheds

Authors
item Wren, Daniel
item Davidson, Gregg -

Submitted to: Journal of Soil and Water Conservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 15, 2011
Publication Date: September 1, 2011
Citation: Wren, D.G., Davidson, G.R. 2011. Using lake sedimentation rates to quantify the effectiveness of erosion control in watersheds. Journal of Soil and Water Conservation. 66(5):313-322. doi.10.1029/2010JF001859.2011.

Interpretive Summary: Sediments stored in lakes represent a valuable archive that can be used to reveal the erosion history of watersheds. A portion of the soil that is moved down gradient during runoff events is deposited in lakes, and the rate at which sediment accumulates should be proportional to the rate of erosion from the surrounding land. The ability to calculate the rate at which this sediment has accumulated over discrete time intervals in the past opens several opportunities for improved understanding and management of watershed processes. Examples include quantifying changes in erosion and deposition rates caused by anthropogenic or natural shifts in land use or by climate change. Future efforts to conserve soil resources can be better justified if post-clearing increases in erosion rates can be quantified rather than simply inferred. Knowing the amount by which management practices reduce erosion rates can also help to justify expenditures by quantifying the effectiveness of the practices in comparison to ancient erosion rates. In the present study, sediments from five natural oxbow cutoff lakes in the Mississippi River alluvial floodplain were dated using 210Pb decay rates and bomb-pulse derived 137Cs with the goal of relating trends in sedimentation rate to reductions in erosion due to management practices. It was found that the radioisotope dating methods were best used in concert with known dates for implementation of management practices. Changes in sedimentation rate over time frames as short as 12 years were detectable. Larger lakes showed smaller changes in sedimentation rate relative to smaller ones.

Technical Abstract: The effectiveness of erosion control methods is difficult to measure, hampering the development of management practices and preventing accurate assessment of the value of erosion control structures over time. Surface erosion can vary widely over an area, particularly if gully erosion is present, and the use of sediments transported in streams for quantifying erosion is hindered by the highly variable nature of fluvial sediment loads. When a watershed drains into a lake, accumulated sediments have the potential to yield information about historic rates of sedimentation that can be used to evaluate the effectiveness of previous erosion control measures. In the present study, sediments from five natural oxbow cutoff lakes in the Mississippi River alluvial floodplain were dated using 210Pb decay rates and bomb-pulse derived 137Cs with the goal of relating trends in sedimentation rate to reductions in erosion due to management practices. It was found that the radioisotope dating methods were best used in concert with known dates for implementation of management practices. Changes in sedimentation rate over time frames as short as 12 years were detectable. Larger lakes showed smaller changes in sedimentation rate relative to smaller ones.

Last Modified: 7/24/2014
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