IMPROVEMENT OF THE FLOOD CONTROL CAPABILITY BY THE SHIMOUKE DAM IN THE UPPER CHIKUGO RIVER BASIN

Abstract

 In this study, a new flood-control concept "Cascade" method was considered in which the upstream Shimouke dam can overflow from its emergency spillway while the downstream Matsubara dam is required only to use its normal spillway and never its emergency spillway in the upper reaches of the Chikugo river basin under the heavy rain in July 2020. As a result of this study, it is made clear that the flood control capability in the basin can strengthen by changing the design high water discharge of the Shimouke dam. In addition, the current design high water discharge of the Shimouke dam, 350 m³/s, is appropriate for cases under uniform precipitation condition in the basin. Moreover, flood control capability with Cascade method compared with a conventional method can be estimated in cases where there is an inflow from a tributary without a dam in the basin where two dams are constructed in series.