NUMERICAL SIMULATIONS USING WATER LEVELS OBSERVED AT A MAINSTREAM FOR FLOOD FLOW IN RIVER SYSTEM WITH SEVERAL LATERAL INFLOWS

Abstract

To discuss river management and maintenances against recent changes in various circumstances surrounding rivers, such as river environments, rainfall characteristics and social conditions, it is necessary to clarify the manner of floodwater storage in the channel. This paper presents an unsteady two dimensional numerical method using water levels measured in a mainstream to compute flood flows in river systems with several lateral inflows, such as tributaries and pump stations. The method is applied to the Asakawa River flood at August 2008, and installation methods of water level observation stations are discussed. And the method is applied to the Ushizu River flood at July 2009, and influence of inflows from pump stations in low-land area on flood flow is evaluated.