Evaluation of Sediment Transport Data

Excessive erosion, transport, and deposition of sediment in surface waters is a major problem in the United States. A national strategy is needed to develop scientifically defensible procedures to facilitate the development of TMDL's for clean sediment in streams and rivers of the United States. In the first part of this study data sets which contain sediment transport and flow data were identified from non-USGS sites. In the second part of this study, an existing method for evaluating impairment of streams by sediment (Rosgen-Troendle technique) was evaluated, problems were identified and a revised technique was developed. This revised technique will be useful in the identification of problems, water quality indicators, and target values for clean sediment TMDLs in streams and rivers (USEPA, 1999). A search of existing data sets yielded 108 sites in the United States with detailed sediment and flow data suitable for testing of procedures for the development of clean sediment TMDLs. The data from these streams was from 11 different states and nine different physiographic provinces of the country and would serve as a valuable resource for further development of procedures to detect impairment due to clean sediment. The Rosgen-Troendle technique (Troendle, 2000, written communication) assumes clean sediment can be identified as a problem for a given stream based on a relation between sediment transport and flow discharge for one of the 48 stream types of the Rosgen classification (Rosgen, 1996). The technique assumes that each of the stream types will have a unique dimensionless sediment transport rating that can be used to establish baseline or reference conditions for other streams of the same Rosgen stream type. As a method of conveying information on channel form, the Rosgen classification works well, however, problems were found with using the Rosgen classification to define baseline or reference types for sediment because some of the types are inherently unstable (types D, F and G, Table 4-1, Rosgen, 1996). Another problem encountered with the Rosgen classification is that the most important level-one criteria do not correlate well with sediment transport. The scaling method used in the Rosgen-Troendle technique does not allow valid comparisons of different sized streams, but in some cases obscures differences in sediment transport rates. In this study a revised methodology was developed. The methodology is as follows: 1) Classify the stream according to Rosgen (1996); 2) Determine the stage of channel evolution (Simon and Hupp, 1986; Simon, 1989b) …