Flood Inundation Analysis and Mitigation with a Coupled 1D-2D Hydraulic Model: A Case Study in Kochi, Japan

Abstract

Coupled one and two-dimensional (1D-2D) hydraulic models play a significant role in analyzing flooding problems to find possible solutions as they can reproduce the actual situations relatively accurately. This paper summarizes approaches to flood inundation analysis and mitigation with coupled 1D-2D hydraulic models of a small mountain watershed in Japan. A detailed flood inundation model including the effects of drainages, pumping, inflow from mountain sub-watersheds and flood gates is developed using coupled 1D-2D hydraulic models. The model is applied to the inundation in Kubokawa, a small town in Kochi Prefecture, Japan on August 9-10, 2014. Simulated and observed maximum water levels along the river and maximum inundations in the flood plain are compared and found to be consistent. Causes of the flooding and percentage of contribution are quantitatively identified, and countermeasures to reduce the effects of flooding are proposed.