A Simple Total Sediment Load Formula

Abstract

Prediction of total sediment load has been a challenge to river engineers for decades. Two approaches are typically used: One is to directly calculate the total sediment load from measured flow and sediment properties, and the other is to separate total sediment load into bed load and suspended load and calculate them independently. Because the criteria that separate bed load and suspended load is still a debatable subject, practical engineers prefer to use the total load equation for estimating sediment load. However, there are more than 31 equations for calculating total sediment load, and the discrepancies of those equations are in the orders of magnitude. To obtain a general equation, this study analyzed more than 4,000 sets of laboratory experimental and 3,000 sets of field measurements of total sediment load. Based on the dimensional analysis, eight new dimensionless parameters are formulated to quantify total sediment load. Correlations of dimensionless total sediment load with those new and other conventional parameters are calculated using the observed data. The highest correlation, 0.94, was found between the dimensionless total sediment load and a new dimensionless parameter, τ* (u* - u*c) / ω , in which u* is shear velocity, ω is settling velocity, and τ* is dimensionless shear stress. A simplified power-law relation is formulated from fitting the measured data. This new relation is compared with the commonly used total sediment load relation, such as Engelund-Hansen (1967), Ackers-White (1972), Yang (1973, 1979). Results showed the new simplified equation yielded the best matches of this set of total sediment load data.