Simulation of Missouri River Bed Degradation

Abstract

The future course of bed degradation in the middle Missouri River has been predicted using numerical simulation techniques. The simulation required development of the new Total Load Transport Model (TLTM), which incorporates the interdependence of friction factor and sediment transport through data‐based empirical relations. TLTM was implemented in a mathematical simulation model called IALLUVIAL, which computes quasi‐steady water and sediment flow in natural rivers having nonuniform bed sediments. IALLUVIAL also incorporates bed‐sediment sorting and armoring, which are processes of fundamental importance to the future course of Missouri River degradation. IALLUVIAL was first validated through simulation of the 1960–1980 severe degradation in the Missouri River between Sioux City, Iowa and Omaha, Nebraska. Subsequently IALLUVIAL was used to predict 1980–2000 degradation for several river‐management scenarios. The simulations suggest that the worst of the degradation is now over, and that it is the channelization, rather than upstream regulation, which is primarily responsible for the degradation. A companion paper describes the details of IALLUVIAL's armoring and sorting simulation procedures.