On the effect of tropical cyclones' translation speed and landfall trajectory on the storm surge dynamics

This study aims to generalize the synthetic effects of TS, LA, and coastal geometries on a maximum surge height (MSH) along the coast through the numerical simulations of a series of idealized scenarios as well as real-scale event. A two-dimensional model in Delft3D-FM was adopted in this study to simulate the MSHs. The model domain consists of multi-resolution grids ranging from 16 km to 1 km considering the cyclone’s landfall spot at the center of the coastline. All these simulations were implemented without tides and waves since this study aims to investigate the synthetic effects on main surge levels. The hypothetical cyclones were generated under various TSs and LAs conditions. The TSs were altered while LAs ranged varied from 0° to 180°. Additionally, the coastal layout and bathymetry were also controlled. For bathymetry, a constant bed, beds with different continental shelf widths, and a multi-sloped bed were also considered. For coastal layout, an open coast and bays characterized by the morphological ratio were considered. Totally, 763 idealized scenarios were simulated to obtain the MSHs distributions along the coast. The realistic scenarios based on historical typhoon Maemi in 2003 was additionally simulated with various TSs and LAs conditions to apply developed idea from idealized scenario cases. The effects of the TS, LA, and coastal geometries on MSH were analyzed by simulating idealized and realistic scenarios. The trends of MSHs along the open coast extracted from each scenario were found to be almost identical despite minor discrepancies. The results revealed that MSHs along the open coast were amplified by fast-moving TSs. For constant bed, the results exhibited a distinct characteristic that generated the Kelvin wave propagating in a down-coast direction, while certain types of sharp LAs with a slow-moving cyclone might generate other types of resonant waves. For the beds with different dimensions of continental shelves, trends of the MSHs were distinguishable between slow and faster-moving TSs. Nevertheless, the continental shelf with narrow width led to a peak at a sharp LA under all TSs, implying that the shelf geometry can limitedly affect the MSH. As for the multi-sloped bed, slope geometry strongly influenced the surge process in that it enhanced the MSH due to the Greenspan resonance. For bays, the trends of MSHs were essentially coincident with those of open coast, while an enhancement of MSHs was observed when L/E was close to 1. Additionally, the realistic scenarios based on a historical typhoon were simulated to validate outcomes from idealized scenarios, indicating that super typhoons like Maemi with a  LA, tend to slow down and generate an extreme surge in Masan Bay in the future sight.