4. Conclusions
In this work, we develop a combined hurricane-circulation-inundation model to quantify extreme coastal flooding induced by synthetic storms under current and future sea levels in Shanghai, China. The main conclusions are summarized as follows: 1) although the storm tide hazard is high, Shanghai’s flood protection system is sufficient for preventing majority of the city from severe flooding (> 100 years) from storm tide under the current climate; 2) extreme “worst-case” scenarios (> 5000 years) can generate unprecedented storm tides (8 - 9 m) in Yangtze River Estuary or Hangzhou Bay, even under the current climate; 3) future SLR will greatly increase Shanghai’s flooding risk compared to the current state, with inundation two times and 20 times more likely to occur by mid- and late-21stcentury, respectively, and inundation depth and area to greatly increases (e.g., 60-1360% increase in the inundation area for the “worst cases” by 2100).
The present study contributes to a better understanding of extreme coastal flooding from TC-induced storm tide and SLR in Shanghai and unlocks the potential for estimating flood hazard evolution due to SLR as well as storm change (e.g., Marsooli et al., 2019) in a changing climate. The methodology is applicable to any coastal city that is susceptible to TC surge flooding and rising sea level. However, since we neglect wave effects on the water level, major seawall failure mechanisms such as wave overtopping and breaching are not considered in the present storm flood modeling; the inundation risk estimated herein is likely a lower bound. Further work will include wave modeling and dike reliability analysis (e.g., Yin et al., 2020) in the climatological-hydrodynamic modeling to better quantify the flood risk under both the current and future climate conditions.