A method for improving predictions of bed‐load discharges to reservoirs

Abstract

AbstractEffective management options for mitigating the loss of reservoir water storage capacity to sedimentation depend on improved predictions of bed‐load discharges into the reservoirs. Most predictions of bed‐load discharges, however, are based on the assumption that the rates of bed‐load sediment availability equal the transport capacity of the flow, ignoring the spatio‐temporal variability of the sediment supply. This paper develops a semiquantitative method to characterize bed‐load sediment transport in alluvial channels, assuming a channel reach is non‐supply limited when the bed‐load discharge of a given sediment particle‐size class is functionally related to the energy that is available to transport that fraction of the total bed‐load. The method was applied to 22 alluvial stream channels in the USA to determine whether a channel reach had a supply‐limited or non‐supply‐limited bed‐load transport regime. The non‐supply‐limited transport regime was further subdivided into two groups on the basis of statistical tests. The results indicated the pattern of bed‐load sediment transport in alluvial channels depends on the complete spectrum of sediment particle sizes available for transport rather than individual particle‐size fractions represented by one characteristic particle size. The application of the method developed in this paper should assist reservoir managers in selecting bed‐load sediment transport equations to improve predictions of bed‐load discharge in alluvial streams, thereby significantly increasing the efficiency of management options for maintaining the storage capacity of waterbodies.