Hazard Assessment for Extreme River Flood Events in the Downstream of Lam River Basin, Vietnam

This study investigates the impacts of rare flood events on the downstream area of the Lam River system, a densely populated economic and political area in North Central Vietnam. The floods from 2010 and 2013 were used to validate and calibrate the numerical model. The numerical results showed good agreement with observed data and satellite images. Three scenarios of water levels at the upstream Dua station were simulated to assess flood depth and areas downstream. Scenario 1, with a water level of 20.5 m, resulted in a flooded area of approximately 25,401.26 ha. In scenario 2, with a water level of 22.5 m, the flooded area increased to 35,476.77 ha. Scenario 3, with a water level of 24.5 m, showed the most significant impact, with a flooded area of 40,804.35 ha, 15% larger than scenario 2. Based on these simulations, flood maps were created to support evacuation plans during severe floods. The results provide a scientific basis for strategies to mitigate flood damage and propose socio-economic development plans for the Lam River basin.