Developing flood risk curves of agricultural economic damage under climate change in the Lower Chao Phraya River Basin, Thailand

Rice is a major agricultural crop in Thailand, while paddy fields near river lines are exposed to high flood risk. This study assesses rice exposure and economic flood risk under future climate in the Lower Chao Phraya River Basin, Thailand. To encompass various flood events, this study estimates the frequency of rice economic damage by employing a large ensemble climate projection dataset based on database for Policy Decision making for Future climate change (d4PDF). Results show that, in the 4-K warmer climate, the 100-year exposed cultivation area and duration will increase approximately by 1.2-1.4 and 1.1-1.2 times, respectively. Decreased rice production is evaluated as monetary damage through several fragility curves. The economic damage by the 2011 flooding is estimated as 11.25 billion Thai Baht, while the estimation varies from the fragility curves employed. In the 4 K warmer climate, regardless of the fragility curves, 100-year rice damage is projected to increase by 1.2-1.4 times. The 2011 flooding is larger than all 3000-year simulations in the past climate, whereas extreme events in the 4 K warmer climate showed higher damage than the 2011 flooding, indicating that agricultural damage corresponding to the 2011 flooding may occur more frequently in the future climate.