Simulation of flood diversion for super standard flood in urban protection zones of the middle and lower reaches of the Dongjiang River Basin

On April 28, 2024, the first flood of 2024 occurred in the Dongjiang River Basin, marking the first numbered flood since 2013. The risk of city encountering super standard flood is increasing. To analyze the impact of super standard flood on the urban protection zones in the middle and lower reaches of Dongjiang River, taking the urban protection zones of Dongguan City and Huizhou City as examples, a one-dimensional and two-dimensional hydrodynamic coupling model is established to analyze the reduction effect of using flood detention embankments on the flood peak of the urban protection zones when facing super standard flood, and the impact on the inundation of land objects within the flood detention embankment range. The results show that under the condition of super standard flood, the use of flood detention embankments has a significant effect on reducing the peak discharge of control stations; When the flood return period is 200 years and the floodgates of the detention dike are opened to divert the flood from the temporary outlet, the peak flow rate of the control station is reduced from 13 066 m³/s to 12 140 m³/s, and the peak water level is reduced from 12.14 m to 11.64 m. The maximum submerged area within the detention dike is 93.66 km², and the average maximum submerged depth exceeds 3 m. The maximum flow velocity at the temporary outlet reaches 3.49 m/s. The research results are expected to provide support for flood control and disaster reduction work in the Dongjiang River Basin.