Flood Routing in Channels with Bank Seepage

Abstract

Bank seepage occurs along natural streams bounded by an alluvial material when the passage of a flood wave produces a rise and fall in the stream stage. Owing to the difficulties of measuring flow rates in a porous medium, the quantity of bank seepage and its effect on the attenuation of a flood wave have not been determined from experimental observations. As an alternative for the purposes of this study, the equations of motion were used to describe flood flows in an idealized rectangular channel bounded by banks of a homogeneous, isotropic, porous medium in which the Boussinesq equation governs flow. The channel and the banks were assumed to be underlain by an impervious layer. Numerical simulation of a sinusoidal flood wave in the channel showed that bank seepage causes significant attenuation of the wave in narrow channels bounded by a relatively pervious material. This attenuation is characterized by a reduction in the hydrograph peak and sustenance of the flow during recession. In wide channels and in channels bounded by a relatively impervious material, no significant attenuation of the flood wave occurs.