Nourishment Effect of Increase in Sediment Supply to Coast by Sand-bypassing through Dams in Upper Tenryu River

Abstract

The Enshu-nada coast has been severely eroded due to decrease in fluvial sediment supply from the Tenryu River because of the obstruction of the continuous sand supply from the river by constructing large dams. The effect of sandbypassing through these dams in the upper basin of the Tenryu River was investigated using the contour-line-change model. Sand supply considering grain sizes was assumed in several cases. In each case, bathymetric changes around the river mouth were predicted by the model. It is predicted that the supplied sand tends to be deposited around the river mouth, while recovering the river delta, and sand supply to coasts far from the river mouth is not so active.