IMPACT ANALYSIS OF CLIMATE CHANGE ON FLUVIAL INUNDATION USING D4PDF: A CASE STUDY IN THE CHOSHUI RIVER BASIN, TAIWAN

Abstract

 Fluvial floods have been considered a lower risk to society in Taiwan since the implementation of well-protection works. However, given the impact of climate change on water-related disasters, it is necessary to re-evaluate the capability of existing facilities in Taiwan to adapt to a changing climate. By utilizing the d4PDF dataset in the rainfall-runoff simulation, we estimated potential changes in peak discharge in the Choshui River basin in central Taiwan to identify the impact of future extremes on runoff characteristics. Comparing the results with the design discharge of downstream Choshui River (100-year return period), the d4PDF +4K ensemble experiments indicate a 9.9%-27.9% increase in peak discharge, highlighting a heightened risk of fluvial flooding. Impact assessments of overflow were conducted by a 1-D river flow and a 2-D inundation model to simulate the fluvial flood inundation. To solve the intrinsic limitation of the 1-D river channel routing with mesh size for large-scale rivers, this research proposes a new scheme to automatically build up the connection between the river, floodplain, and inland cells to consist of the simulation with the actual channel boundary. This procedure successfully progresses the model simulation to be flexible to fit different shapes of river channels. Applied to the model, we provide several case studies of fluvial inundation by incorporating discharge derived from d4PDF simulation input. The results of the inundation simulation show that coastal areas around the Choshui River basin expose to a high risk of fluvial floods under climate change, highlighting the insufficiency of existing flood prevention works. Also, we demonstrate the potential risk areas for future fluvial floods, alone the Choshui River.