Hydrodynamics in the confluence of the Snake and Clearwater Rivers

摘要

Fluvial confluences are a basic component of all river networks. Confluences affect river biodiversity due to the complex flow patterns often associated with them. Previous studies investigated confluences flow hydrodynamics mainly at the laboratory scale or in small natural confluences. Previous studies, however, indicate that confluence size may affect flow patterns and confluence morphology. To investigate the role of scale on confluence hydrodynamics, a field study was conducted at the large confluence of the Snake and the Clearwater Rivers at the Washington-Idaho border. Velocity profiles were measured along cross sections using an acoustic Doppler current profiler, and the confluence bathymetry was surveyed with multi-beam sonar. The results illustrate the flow patterns and bed morphology during the measurement period. While typical confluence velocity patterns were identified, secondary circulation patterns differ to some extent from those typically seen in small confluences.