Characteristics of storm surge water level and empirical forecasting at the Pearl River Estuary

The Pearl River Estuary, located in the core area of the Guangdong-Hong Kong-Macao Greater Bay Area, is frequently affected by strong typhoons. As an economically developed region, it often suffers severe losses from storm surge disasters. Based on nearly 50 years of long-term tidal data from the Macau Inner Harbor station, a typical hydrological station in the Pearl River Estuary, this study analyzes that 45% of the annual extreme water levels at the Macau Inner Harbor station are caused by typhoon events. The probability of extreme water levels occurring within 1 hour before and after the astronomical high tide is approximately 82%. The extreme water level distribution shows a distinct non-uniform bimodal pattern, with the peak occurring in only 5% of the cases coinciding with the astronomical high tide. The path and landfall location of typhoons have significant impacts on the characteristics of storm surge, including its magnitude and duration. Typhoons with a northwestward or westward path cause larger storm surge and account for the majority of cases with over 30 cm of storm surge, approximately 90% of the total. When the Macau Inner Harbor station is located in the left semicircle of a typhoon, the storm surge is relatively small, while it is larger when the station is in the right semicircle. Moreover, a trend is observed where storm surge duration is longer and surge magnitude is smaller when the landfall point is closer to the west. Empirical formulas for extreme surge forecasting considering typhoon intensity, path, and landfall location are established and show a high degree of fitting with the observed values. This study provides valuable references for regional storm surge forecasting and disaster prevention and control.