Deterministic-probabilistic approach for probable maximum typhoon-induced storm surge evaluation over Wenchang in the South China sea

This study considered a probability-determinative method for evaluation of the probable maximum storm surge (PMSS) in the Wenchang area, Northeast Hainan Province, which focused on landfall location, selection of typhoon parameter combinations, and surge response exploration. Overall, 40 typhoon parameter combinations were derived based on analyses of historical records, including typhoon central pressure, approach speed, approach direction, radius of maximum wind speed (RMW), and ambient atmospheric pressure. We used the Finite-Volume Coastal Ocean Model driven by prototypical typhoon winds and atmospheric pressure fields to simulate astronomic tides and storm surges in sensitivity runs, for which typhoon cases were established for various landfall locations and typhoon parameter combinations. It was found that typhoons with intensity of 871 hPa and largest RMW of 60 km, moving at a fastest speed of 36 km/h with an approach direction of 285 degrees, and making landfall similar to Typhoons Rammasun or Kalmaegi, could induce a PMSS along the northern region of Wenchang. Conversely, similar typhoons moving westward with an approach direction of 270 degrees, and making landfall to the south of Wenchang, 60 km from the areas of interest, could induce PMSS along the middle and southern regions of Wenchang. The physical laws were verified based on comparison between the Rammasun and Kalmaegi storm surges. Total elevation and inundation simulations along coastal regions were performed through coupling of the PMSS and astronomic tides, where the astronomic tides were selected as the 90th percentile of the daily highest tide over 19 years. All conclusions stated in the paper were based on the characteristics of the coastlines and circumstances of the study region.