Assessment of Flood Dynamics in Lower Mekong Delta Using Modeling Approach

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

Flood Mapping along the Lower Mekong River in Cambodia

Located in Southeast Asia, Cambodia is one of the most disaster prone countries, where flooding rank the top of the natural disaster. Flood affects and threatens not only humans’ and animal’s life, properties, infrastructures, but it is also an obstacle to the current development. Furthermore, without having the efficient modern technology to predict flood situation in Cambodia, the disaster in this country become more serious. The objective of this research study is to simulate flood inundation area by using software HEC-RAS. HEC-RAS is a hydraulic model software capable of calculating any hydraulic river study including flood. In this study, the Lower Mekong River with approximately 50 km length was selected to delineate flood map from 2000 until 2013 and also 10-year return period map. The available data are 11 years of the measured water level at the upstream and downstream stations, 18 surveyed cross-sections and DEM with grid cell size 30 m x 30 m were used to understand the recurrence of the floods in the study area. The output from the model was delineated into map including flood extent and flood depth from 2000 until 2013 (without 2009, 2010 and 2012). The results show that flooding varied from year to year; however, the greatest flood was during 2000 and again in 2011. The simulated flood maps were compared with observed data to figure out that the model was accurate for flood mapping. These results will be useful for river engineers, experts, and decision makers to manage river floods