The influence of astronomical tide phases on urban flooding during rainstorms: Application to Macau

The study area is the western part of the Macau Peninsula in China, with an area of 4.06 km 2 . This study developed a coupled hydrological-hydraulic model that simulates the two-dimensional (2D) surface flow and one-dimensional (1D) drain pipe flow of compound inundation. The model was applied to Macau, China, as a study area, and the typhoon Mangkhut in 2018 was used as a case study to validate the model’s performance. Simulating compound inundation scenarios of extreme rainfall and astronomical tide and exploring the influence of astronomical tide on coastal urban inundation. Urban flood disasters are profoundly influenced by tidal levels, albeit the height of tides alone does not solely exacerbate the phenomenon. Rather, the phase of astronomical tides during rainfall also plays a crucial role in determining the severity of urban flooding. This research has revealed that when rainfall synchronizes with the recession phase of the spring tide, urban flooding conditions become acute, 17.66 % increase in total surface water volume for the scenario with the highest tidal level impact compared to the scenario with the lowest tidal level impact. This paper presents the response of coastal cities to the flooding process under different combined rainstorm-astronomical tide scenarios, to provide scientific guidance for disaster preparedness planning in coastal areas, and to improve the resilience of disasters. • Quantitative assessment of the effects of astronomical tides on urban inundation. • Impact of urban inundation effect under simulated combined scenarios. • Construction an integrated hydrological and hydrodynamics urban flood model. • Developing a 1D-2D model for urban flood simulation.