Derivation of flood elasticity under climate and forest change for a tropical monsoon basin of Thailand.

• A statistical model of flood elasticity under changing conditions was derived. • The model was applied in a typical tropical monsoon basin of Thailand. • The flood peaks are expected to increase due to deforestation and climate change. • The absolute value of storm-flood elasticity is larger for shorter return periods. • Climate change tends to dominate future flood changes over deforestation. Storms and the resultant floods have caused considerable fatalities and have raised increasing global concerns in the context of climate change and socioeconomic development. The relationships between storms and floods have been explored as storm-flood elasticity, but the shifts of the storm and flood peak distributions under changing conditions have not been sufficiently considered. In this study, a novel statistical model that reflects the relationship between storm distribution and flood distribution under changing conditions has been developed. Due to its concise structure, the statistical model can be easily used to explicitly derive the storm-flood elasticity and quantify the future flood responses to changing climatic and land surface conditions. The statistical model is then applied in a typical tropical monsoon basin in Southeast Asia, the Upper Chao Phraya River Basin (UCPRB), which underwent significant climate change and deforestation. The shifts of the storm and flood frequency curves are modeled via GAMLSS with the aid of wet season dew point and forest cover ratio, and the curves derived from statistical models prove to be consistent with the results from the more computationally intensive process-based model. By examining flood elasticity including storm-flood elasticity and forest-flood elasticity under changing conditions, the response of flood peak to storm peak and forest cover change is expected to weaken as the return period increases. Future flood peaks are expected to change substantially under most emission scenarios, and the changes can be mostly attributed to climate change rather than deforestation. The dominance of climate change over deforestation strengthens in the long-term future and is more evident for shorter return periods, highlighting the indispensable role of climate change mitigation in reducing future flood risks in the UCPRB. The analytical framework developed by this study can also be applied in other climate regions besides tropical regions, which could help to provide insights for future changes in floods and their relationship with climatic and land surface characteristics under changing conditions. [ABSTRACT FROM AUTHOR]