Abstracts

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

Author(s): Wren, D.; Davidson, G.

The effectiveness of erosion control measures is difficult to quantify, 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 (Beasley, Washington, Wolf, Roundaway, Moon) 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 15 years were detectable. Larger lakes generally showed smaller changes in sedimentation rate as may be expected because of the expense and difficulty in applying management practices over larger areas.

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Session I Sedimentation
Session II Weather/Climate
Session III Coastal Resources
Session IV Surface Water Management
Session V Wetlands
Session VI Education
Session VII Management/Planning
Session VIII Wetlands
Session IX Delta Groundwater
Session X Nutrients
Session XI Delta Water Resources
Session XII Ports

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