Estimating fluvial sediment transport: The rating parameters

Correlations between suspended sediment load rating parameters, river basin morphology, and climate provide information about the physical controls on the sediment load in rivers and are used to create predictive equations fo r the sediment rating parameters. Long-term time-averaged values of dischar ge, suspended load, flow duration, flow peakedness, and temporally averaged values of precipitation, temperature, and range in temperature were couple d with the drainage area and basin relief to establish statistical relation ships with the sediment rating parameters for 59 gauging stations. Rating p arameters (a and b) are defined by a power law relating daily discharge val ues of a river (Q) and its sediment concentration C-s, where C-s = aQ(b). T he rating coefficient n (the mathematical concentration at Q = 1 m(3)/s) is inversely proportional to the long-term mean discharge and is secondarily related to the average air temperature and the basin's topographic relief. The rating exponent b (the log-log slope of the power law) correlates most strongly with the average air temperature and basin relief and has lesser c orrelations with the long-term load of the river (which is related to basin relief and drainage area). The rating equation describes the long-term cha racter of the suspended sediment load in a river. Each river undergoes high er-frequency variability (decadal, interannual, and storm event) around thi s characteristic response, controlled by weather patterns and channel recov ery from extreme precipitation events.