Development of a distributed rainfall-run-off/flood-inundation simulation and economic risk assessment model

A distributed rainfall-run-off/flood-inundation (DRR/FI) simulation model is developed based on a one-dimensional dynamic wave equation for river routing and a two-dimensional shallow water equation for surface flow simulation. The DRR/FI model can be used in different ways with the prevailing 1D pathway kinematic wave-based distributed rainfall-run-off model. The DRR/FI model is designed to simulate rainfall-run-off processes and dike-break/inland water inundation processes in a catchment in an integrated manner. Additionally, a direct house/crop economic loss estimation model is integrated with the DRR/FI model. With the loss estimation model, the direct house/crop economic damage within the DRR/FI model domain can be estimated in currency all at once. The DRR/FI and economic risk estimation model are applied to the Sayogawa river catchment in Japan, which experienced a severe flood disaster on 910 August 2009. The simulated water level/discharge and inundation area values obtained using the DRR/FI model with radar-composite and radar-Automated Meteorological Data Acquisition System (AMeDAS) reanalysis data are in good agreement with the observations. The results also show the range of validity obtained using raw radar data for flood forecasting. Finally, estimation of the direct house/crop economic loss has been carried out. In the results, the economic loss for houses is estimated at 23.0 billion JPY and the crop loss at 0.67 billion JPY. These estimations are in fairly good agreement with the reported values of 18.5 billion and 0.245 billion JPY.