Flood hazard assessment under climate change scenarios in the Yang River Basin, Thailand

Climate change is expected to increase both the magnitude and frequency of extreme precipitation events, which may lead to more intense and frequent river flooding. This study aims to assess the flood hazard potential under climate change scenarios in Yang River Basin of Thailand. A physically-based distributed hydrological model, Block-wise use of TOPMODEL using Muskingum-Cunge flow routing (BTOPMC) and hydraulic model, HEC-RAS was used to simulate the floods under future climate scenarios. Future climate scenarios were constructed from the bias corrected outputs of three General Circulation Models (GCMs) for 2020s, 2050s and 2080s. Results show that basin will get warmer and wetter in future. Both the minimum and maximum temperature of the basin is projected to increase in future. Similarly average annual rainfall is also projected to increase in future, higher in near future and lower in far future. The extreme runoff pattern and synthetic inflow hydrographs for 25, 50 and 100 year return flood were derived from an extreme flood of 2007 which were then fed into HEC-RAS model to generate the flood inundation maps in the basin. The intensity of annual floods is expected increase for both RCP 4.5 and 8.5 scenarios. Compared to the baseline period, an additional 60 km² area of basin is projected to be flooded with the return period of 100 years. The results of this study will be helpful to formulate adaptation strategies to offset the negative impacts of flooding on different land use activities in Yang River Basin.