Impact of typhoon landfall time on seawall breach and flood evolution based on the case of typhoon Maria (1808)

This study presents a case study of Typhoon Maria (2018) affecting Yacheng Town, Xiapu County, Fujian Province, China, to investigate how typhoon landfall timing relative to the astronomical tide influences seawall breaching and flood evolution under storm surge conditions. The study employs the MIKE 21 model, SWAN model, and DLbreach model to simulate the breach process and flood inundation under different typhoon landfall timings. The findings indicate that the storm surge effect intensifies with earlier typhoon landfall, and the typhoon waves are positively correlated with the water level. Additionally, adjusting the typhoon landfall time by three hours earlier or later significantly reduces the flood inundation area, but adjusting it by one hour has little effect. The quantitative results are specific to this case study of Typhoon Maria at Yacheng Town. These findings provide a crucial scientific basis and reference for the formulation of disaster prevention and mitigation measures for seawalls and the design of coastal engineering projects. • The paper investigates the breaching process of seawalls under the influence of storm surges and typhoon waves, filling a gap in previous research. • By shifting astronomical tide levels, the study explored the disaster situations caused by typhoons landing at different times. • Typhoons landing at high tide cause faster and larger breach flow, while at low tide, the flow is slower and smaller.