FLOOD RISK ANALYSIS IN SHIGA PREFECTURE USING THE INTEGRATED HYDRAULIC MODEL CONSIDERING WATER LEVEL OF LAKE BIWA

Abstract

 Shiga Prefecture is the only prefecture in Japan that maintains a "Site safety level" which is inundation estimation map considering both internal and external flood. “Site safety level” is the basic information fo r its watershed flood control policy. However, the current integrated hydrologic model does not address th e Lake Biwa floods. This is because the water level fluctuation of Lake Biwa itself due to the outflow fro m the inflow rivers of Lake Biwa and the Seta River weir operation has not been taken into account. In thi s paper, to solve the above problem, a one-level tank model consisting of inflow into and outflow from the lake was constructed and coupled with an inundation model to develop a model linked to the water level of Lake Biwa. The model was used to create a multi-hazard-level “site safety map". Comparison of the res ults with and without consideration showed a tendency for differences in maximum inundation depth and duration of inundation to be generated for the areas around the lakeshore, the inflow rivers and inland lake s that are directly affected by the water level of Lake Biwa.