Assessment of Flood Dynamics in Lower Mekong Delta Using Modeling Approach

Abstract

The assessment of flood dynamics is essential in supporting the nation and all stakeholders for the better flood management and adaptation. Climate change and hydropower dam operation pose threat to water resources in the Lower Mekong Delta. Cambodia is vulnerable to the flood impact due to its low adaptive capacity. Historically, flood has big impact on Cambodian society, economics and environment. This research was conducted by using the 2D HEC-RAS Modeling Application to study the flood dynamics under the influence of climate change, hydropower operation and irrigation expansion. The analysis is based on the observed flow and water level of 5 years from 2015 to 2019 and digital elevation model (6 m x6 m). The indices indicated satisfactory performance for the simulation model with the value of NSE between 0.78 and 0.97 and R2 between 0.80 and 0.96. The impact of climate change, hydropower operation and irrigation expansion, on the Cambodian Mekong floodplain area in forms of the flood inundation characteristics using the above well-configured hydraulic model framework. The results show that the flood extent increases around 74% in dry season and decrease around 20% in rainy season. Comparing to the baseline, the results of the scenario study suggest that the study area is likely to experience larger floodplain area in dry season (October to April), and flood extent in rainy season is lesser (May to October). The simulated results will provide important hydraulic information to respond to the future change of flood extent. The increase of water level in the dry season will provide water availability in the water supply sector and agriculture.