Combined Geomorphic and Numerical-Modeling Analyses of Sediment Loads for Developing Water-Quality Targets for Sediment
Proceedings of the Water Environment Federation
The principle objective of the study was to determine sediment loads for James Creek, Mississippi and for similar, but stable "reference" streams to develop water-quality targets for sediment. "Reference" sediment-transport loads were determined from stable streams with historical flow and sediment-transport data in the Southeastern Plains Ecoregion. Using the discharge that occurs, on average every 1.5 years (Q 1.5 ) as the "effective discharge," an initial "general reference" of 0.31 T/d/km 2
... e" of 0.31 T/d/km 2 was obtained. This value, however, is skewed towards streams with sand beds and does not accurately reflect conditions along James Creek. A refined "reference" condition was developed for stable silt/clay-bed streams in the Southeastern Plains resulting in a "reference" suspended-sediment yield of 3.23 T/d/km 2 at the Q 1.5 . A weighted-reference condition based on the percentage of the drainage area encompassed by the various bed-material types results in a reference yield at the Q 1.5 of 2.2 T/d/km 2 . Similarly, a weightedreference concentration of 160 mg/l was obtained. "Actual" sediment-transport loads were obtained by: simulations of flow and sediment transport using the MS 38655. crossings in 1999 loads decreased to about 39 T/D/km 2 . This value is more than an order of magnitude greater than the "reference" yield.