An optimal scenario for the emergency solution to protect Hanoi Capital from the Red River floodwater using Van Coc Lake

The Red River dike system was built, and an emergency solution was implemented to protect Hanoi Capital city from flood disasters. In the solution, floodwater from the Red River is discharged through the Van Coc Gate, with an overflow point into Van Coc Lake, and is drained downstream through the Day Weir. However, an optimal scenario for the operating procedure of the emergency solution, based on a comprehensive evaluation of the flood risk level from the Red River to the residential areas located outside the protected areas of the dike system, has not been adequately addressed to date. In this study, we employed the latest digital elevation map in a high spatial resolution for the first time, and a two-dimensional depth-integrated hydrodynamic model was utilised to obtain the optimal operation for the emergency solution. The optimal scenario was determined to minimise the flood risk level to the residential areas and optimise the inflow discharge at the Van Coc Gate and the overflow point, and the outflow discharge at the Day Weir for ensuring the safety of the operating system. This study lays a promising foundation for designing risk-reduction strategies in Hanoi Capital.