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ARS Home » Pacific West Area » Boise, Idaho » Northwest Watershed Research Center » Research » Publications at this Location » Publication #109212

Title: ESTIMATING FLUVIAL SEDIMENT TRANSPORT: THE RATING PARAMETERS

Author
item SYVITSHI, JAMES
item Morehead, Mark
item BAHN, DAVID
item MULDER, THIERRY

Submitted to: Water Resources Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/1/2000
Publication Date: N/A
Citation: N/A

Interpretive Summary: The sediment concentration in rivers throughout the world commonly has a power lower relationship with the discharge (Cs=aQ^b). The parameters (a and b) of the rating equation vary from river to river in a complex manner. We conducted a multiple regression analysis on the rating parameters and gross basin morphology characteristics (relief, area, etc) along with meteorological characteristics (mean annual temperature, total annual precipitation, etc). The regressions quantified the strength of correlation between the basin characteristics and the rating parameters and gave indications as to the factors controlling erosion from a basin and it's resultant sediment load. Rating coefficient (a, the mathematical concentration at Q=1m^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 correlation's with the long-term load of the river (which is related to basin relief and drainage area).

Technical Abstract: Correlation's between the suspended sediment load rating parameters and river basin morphological and climatological parameters are leading towards predictive equations for the rating parameters and a better understanding of the physical controls on the sediment load in rivers. Long-term time-averaged values of discharge, suspended load, flow duration, flow peakedness, and temporally-averaged values of precipitation, temperature and range in temperature were coupled with the drainage area and basin relief to establish statistical relationships with the sediment rating parameters for 59 gauging stations. Rating parameters (a and b) are defined by the power law relating daily discharge values of a river (Q) and its sediment concentration (Cs), where Cs=aQ^b. Rating coefficient (a, the mathematical concentration at Q=1m^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 correlation's with the long-term load of the river (which is related to basin relief and drainage area. Each river undergoes higher frequency variability (decadal, inter-annual, storm event) around this characteristic response, controlled by weather patterns and channel recovery from extreme precipitation events.