Physical Drivers of Changes in Probabilistic Surge Hazard Under Sea Level Rise

Surge hazards induced by tropical cyclones have caused substantial economic losses and casualties for coastal communities worldwide. Under projected sea level rise (SLR), it is not well understood how the probabilistic surge hazard may change. Coastal planning and engineering usually adopt the “bathtub” method to evaluate the surge‐SLR response, where surge with SLR is considered to be the exact summation of the two. This method has been shown by previous studies to be unreliable. Studies on surge‐SLR response either use a low‐fidelity model setup or rely on individual storm's surge to represent the probabilistic surge due to the high computational burden. Herein, we use high‐fidelity numerical models in the Tampa region, West Florida, consider 188 synthetic storms and four SLR scenarios, and investigate the surge‐SLR response and its physical drivers. Compared to the direct summation of present‐day surge and SLR amount, results show that the probabilistic surge with SLR can be 1.0 m larger, while different individual storm's surge with the same magnitude can be 1.5 m larger or 0.1 m smaller, indicating the importance of not relying on a limited number of surge events to assess the probabilistic surge response to SLR. Investigation of the physical drivers shows that distinct topographic features of the study area and storm forward speed notably affect the surge‐SLR response. When considering 1.3 m or larger SLR in the study area, complex topography, and large surge events, the effects of SLR on the probabilistic surge are hard to predict and should be investigated more carefully.