Sediment transport of streams in the Washita River Basin in Caddo and Grady Counties, Oklahoma

Sediment yields for nine experimental watersheds, whose drainage areas vary from 26.0 to 3290 square miles, were related to the geology in the watersheds. Yields from watersheds with mixed sandstone, siltstone, and shale geology were higher than for watersheds where the geology was predominantly sandstone. The highest yield rate was 29.7 inches per 1000 years for a mixed geology watershed, the lowest yield rate being 1.32 for a sandstone watershed. Stream channel shape was found to be related to the material in transport. Streams with large sand loads have wide, shallow channels, whereas streams with a predominantly silt load have narrow, deep channels. The correlation between the temperature of the flow and sediment concentration was +0.93. Several total load predictions made with the Colby and modified Einstein procedures were compared with those made with the Brooks total suspended load equation when field-determined sediment z values and velocity k values were used. Computations by the modified Einstein and Colby method compared favorably with those made by the Brooks method.