A Study on Key Determinants in Enhancing Storm Surges Along the Coast: Interplay Between Tropical Cyclone Motion and Coastal Geometry

Generalizing the relationship between cyclonic features and storm surges remains challenging because previous studies have produced diverse results for different regions and historical events. We implemented Delft3D-FM simulations and examined the synthetic effects of translation speed Vt and landfall angle alpha on maximum surge height (MSH) along an open coast and bay. By simulating idealized cases with varying Vt and alpha, we found that fast translation of a tropical cyclone (TC) magnified the MSH, with the most extreme MSH occurring when the landfall angle was almost perpendicular to the coastline. In addition, the simultaneous presence of smaller alpha and slower Vt conditions for a TC can trigger coastally trapped waves arriving ahead of its landfall. The impacts of the Proudman and Greenspan resonances contribute substantially to the MSH, depending on the conditions of the TCs and their topographies. We quantitatively assessed the effect of coastline geometry, and the results revealed that the morphological ratio influenced the MSH. Our findings suggest that the synthetic effects of cyclonic and topographic factors are critical for generating resonance and trapped waves that can modify main surges. The application of our findings from idealized cases to realistic cases based on historical TC indicates their applicability to storm surge risk assessment. Finally, we conducted a factor-based diagnosis for the rapid evaluation of MSH, which can provide insightful references for future storm surge mitigation. Storm surges induced by tropical cyclones are influenced by the cyclone characteristics and local topography. Previous studies have commonly conducted case studies using certain regions while considering a limited number of factors. This study aimed to understand the combined effects of these factors by simulating hypothetical cyclones traveling over simplified and realistic seabeds. The results showed that fast-moving cyclones approaching the coastline perpendicularly resulted in higher storm surges. Certain cyclones with oblique trajectories could be equally essential, as they induced specific wave responses that were distinct from the main part of the storm surges. This study also provides new insights into the assessment of future storm surges by considering the interplay among cyclone movement, topography, and coastline shapes. As cyclonic characteristics may be altered by climate change, this study highlights the need for a comprehensive understanding of the physical factors affecting storm surges to better prepare for future hazards. The effect of tropical cyclone motion and coastal geometry on the development of storm surges is assessed using numerical simulations Developing the maximum surge height relies heavily on the coastal wave responses that arise from the cyclonic and topographic conditions We provide a holistic diagram of the general utility of storm surge hazard assessments under various cyclonic and topographic conditions