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United States Department of Agriculture

Agricultural Research Service

Title: Reference and Impacted Sediment Transport for Use in Developing Clean Sediment Tmdl's: Mississippi and the Southeastern United States

Authors
item Simon, Andrew
item Kuhnle, Roger
item Dickeerson, Wendy - UNIVERSITY OF MISSISSIPPI

Submitted to: Laboratory Publication
Publication Type: Government Publication
Publication Acceptance Date: February 15, 2002
Publication Date: February 15, 2002
Citation: Simon, A., Kuhnle, R.A., Dickeerson, W. 2002. Reference and impacted sediment transport for use in developing clean-sediment tmdl's: mississippi and the southeastern united states. USDA-ARS National Sedimentation Laboratory Research Report No. 25. 77 pp.

Interpretive Summary: Sediment is the principal listed pollutant in surface waters of the United States and Mississippi has many streams listed as impaired due to sediment. To develop water-quality targets for sediment it is first necessary to determine "natural" or "background" rates of sediment transport. This will permit evaluation of existing sediment-transport rates relative to background levels so that impact due to sediment can be determined. To accomplish this flow and sediment-concentration data for 239 sites in the three ecoregions of the southeastern United States were acquired and analyzed to develop a methodology by which TMDL practitioners could develop water-quality targets for sediment. The three ecoregions are: Mississippi Alluvial Plain (MAP), Mississippi Valley Loess Plains (MVLP) and Southeastern Plains (SEP). The MAP ecoregion includes the Mississippi Delta. Particular attention was given to Mississippi where sediment-transport relations and associated field evaluations have been completed for all sites that have historical flow and sediment-transport data. Median values for stable, "reference" conditions were established for each ecoregion in Mississippi using suspended-sediment yield values for those sites that were identified as Stage I or Stage VI. Preliminary "reference/target" values for Mississippi sites in the MAP, MVLP, and SEP ecoregion are 1.4, 5.8, and 1.3 T/d/km**2, respectively. These values represent minimal reductions in sediment yield for the MAP or Delta region of Mississippi and substantial reductions in the Loess Hills area.

Technical Abstract: Flow and sediment-concentration data for 239 sites in the three ecoregions of the southeastern United States were acquired and analyzed to develop a methodology by which TMDL practitioners could develop water-quality targets for sediment. The three ecoregions are: Mississippi Alluvial Plain (MAP), Mississippi Valley Loess Plains (MVLP) and Southeastern Plains (SEP). The MAP ecoregion includes the Mississippi Delta. Particular attention was given to Mississippi where sediment-transport relations and associated field evaluations have been completed for all sites that have historical flow and sediment-transport data. Sediment-transport rates at the effective discharge (i.e., that discharge that transports the most sediment over the long term) were used as a measure of sediment production and delivery for the southeastern ecoregions. Sediment yields, expressed in tonnes/day/km**2 ranged from about 0.01 to more than 6,000. Median values for the MAP, MVLP, and SEP are 0.88, 89.0, and 0.50, respectively. Median values for stable, "reference" conditions were established for each ecoregion in Mississippi using suspended-sediment yield values for those sites that were identified as Stage I or Stage VI. Preliminary "reference/target" values for Mississippi sites in the MAP, MVLP, and SEP ecoregions are 1.4, 5.8, and 1.3 T/d/km**2, respectively. These values represent minimal reductions in sediment yield for the MAP or Delta region of Mississippi and substantial reductions in the Loess Hills area.

Last Modified: 11/21/2014
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