Numerical Simulation of Sediment Yield, Storage, and Channel Bed Adjustments

Abstract

The response of alluvial channels to perturbations in the balance of water and sediment inflow is one of the fundamental issues facing geomorphologists and hydraulic engineers. As far back as the first half of the 20th century Ruby (1933) and Makin (1948) were developing concepts and quantitative expressions for the adjustments that occurred when a stream channel at grade was subjected to an change in the steady-state balance of the water and sediment loads it received. In the 1970s fluvial geomorphologists began focusing on the importance of thresholds in determining whether a particular reach of a stream channel would have a tendency to erode, aggrade, or remain stable over the short run (e.g., Schumm, 1973; Bull, 1979). In order to facilitate inferences to be made without recourse to excessive amounts of data and/or overly involved calculations, fairly simple conceptual models invoking channel slope, water discharge, sediment discharge, and derivatives of those basic variables such as boundary layer shear stress, and stream power were used to explain many aspects of how channels adjust to variations in water flow and the character of sediments in the channel.