Abstract
A retarding basin is one of the most effective countermeasures to mitigate existing downstream flooding problems. Effectiveness of the basin is strongly dependent on design of an overflow levee. Experimental works have been commonly employed for the overflow levee design. The primary objective of this study is to demonstrate that a numerical model, which are comprised of the distributed hydrological model, the 2D unsteady flow model based on flux-difference splitting scheme as well as unstructured finite-volume method, and operation of drainage system, is an effective tool to evaluate the stage-discharge relationship of the Ushidugawa retarding basin in the Rokkaku River under the given conditions of the shape of the overflow levee and rain-fall and tidal level of the Ariake Sea.
