Influence of River Sinuosity on the Distribution of Conservative Pollutants

Abstract

The influence of river sinuosity on the distribution characteristics of pollutants in a wide river is investigated three-dimensionally with a numerical model. It is found that, for a meandering river, the hydrodynamic force strongly controls the distribution of a conservative pollutant in the river. Because of secondary flow at the channel bend, high sinuosity leads to a lighter-than-water pollutant concentrating more on the inner bend apex region at the surface, whereas at the deep near-bed region, it concentrates more on the outer bend apex. For a heavier-than-water pollutant gravity flows in sinuous channels, there are two unique features resulting from the super-elevation and multicell cross-sectional secondary flows with alternate circulation directions: (1) the pollutant is distributed at the bottom more on the inner bend apex region; and (2) more on the outer bend apex region at a depth corresponding to the mixing region of the bottom two secondary flow cells of opposite circulation direction. These findings may assist field investigations in locating the best sampling points and in determining cost-effective measures for accidental or planned river pollution events.