Improving rainfall-runoff-inundation model for realistic representations of main river with levees

Abstract

Growing flood severity demands numerical experiments on watershed-scale rainfall-runoff-inundation processes, to properly evaluate and develop effective practical measures. Hence, the Rainfall-Runoff-Inundation (RRI) model has been continuously developed to enhance simulation accuracy. Unfortunately, conventional RRI implementations often blur rivers and floodplains at the grid scale and do not distinguish left and right banks, limiting the spatial accuracy of inundated areas. Thus, we extend the RRI model to: (1) separate inundation calculations of the left and right banks, (2) allocate rainfall falling on river cells to the channel water balance, and (3) explicitly and spatially represent the river channel width exceeding the model resolution to improve the accuracy of estimating the spatial distribution and the depth of inundated areas as well as river discharge. The results show that explicitly representing the channel width improves the accuracy of simulated river discharge, inundation extent and relative spatial characteristics of depth. Consequently, our revised RRI model yields more realistic outputs than conventional flood control models.