Sediment Transport in the Restoration of Gravel-Bed Rivers

Abstract

A successful stream restoration design must be able to transport the sediment supplied to it with the available flow. Although this guidance is widely cited, only water supply is routinely incorporated in a consistent manner in restoration design. A number of factors can alter both the caliber and rate of sediment supply to a stream. Exact forecasts of sediment supply are seldom available and it is often possible to reliably estimate only the sign of changes in sediment supply. Channel design methodology, including estimates of sediment transport, must account for large uncertainty in future sediment supply. This paper examines sediment transport in coarse-bedded streams with the goal of identifying robust methods that provide reliable estimates of present and future transport. The response of bed composition and elevation to changes in sediment supply rate and caliber is examined. The accuracy and cost of methods for estimating sediment flux are evaluated. Emphasis is placed on determining the transport of different grain sizes, including the number of size fractions needed to adequately address potential channel change.