A flood risk projection for Yongdam dam against future climate change

Abstract

A sensitivity analysis of the flood safety of Yongdam Dam using a regional climate change simulation is presented. Based on the output of the CCSM (Community Climate System Model) general circulation model, the SNURCM (Seoul National University Regional Climate Model) computes regional scale output with 60 km spatial resolution and 21 vertical layers. Using the SRES (Special Report Emission Scenario) B1 climate change scenario when applied to the Geum river basin, where Yongdam Dam is located, SNURCM reduces significantly the bias in Annual Maximum Event total Precipitation (AMEP) & Annual Maximum Daily Precipitation (AMDP) that CCSM shows. The streamflow change scenario is then simulated using SSARR (Streamflow Synthesis and Reservoir Regulation) model. A rainfall-runoff model was implemented using precipitation and temperature projected by CCSM and SNURCM. The model demonstrated that average streamflow would increase 38.7% and the variability would increase 14.3%. This remarkable increase in projected annual maximum flow for the next 20 years (2000-2019) should be a significant negative signal to water resources managers. This streamflow change scenario was then inputted into the G-RiBSS (Geum River Basin Systems Simulator) model to assess the sensitivity of the current river basin system to possible climate change. The result indicates that the number of floods remains almost the same, but that the magnitude of a single flood event and the recovery from it become worse.