Abstract
River mouth sandbars produce bed slope gradients in longitudinal and lateral directions with a contracted channel between them. The bed topography around the sandbars changes vertical velocity distribution due to stream curvatures and flow accelerations and decelerations. It is important for flood flow and bed variation analysis to evaluate three dimensional flows around the sandbars. The objective of this paper is twohold. First, we derive the method to evaluate the variation in the vertical velocity distributions and discuss the appropriate calculation method for flows in the river mouth with sandbars using the computation result by the General Bottom Velocity Computation method. Second, we develop a calculation method of flows and bed variations around sandbars with the large bottom boundary gradients and investigate the effects on the computations results of flows.
