Compound effects in complex estuary-ocean interaction region under various combination patterns of storm surge and fluvial floods

Estuary-ocean interaction regions typically confront compound floods caused by multiple drivers. However, current researches on formation mechanism and compound effect of such disaster remain inadequately profound. Therefore, this study proposed a framework to evaluate the encountering rules and hazards of compound flood based on Copula theory and hydrodynamic model. Taking Pearl River Delta (PRD) in China as a case study, the compound flood hazards under different joint scenarios with various drivers were analyzed. The results indicated that concurrent fluvial floods and storm surge will result in higher flood hazards than single driver. The simulated water levels in most areas of the PRD demonstrated a pattern that water levels of Survival Kendall Return period are greater than that of Kendall Return period, and water levels of AND Return period are the lowest. Flood hazards induced by two drivers with moderate magnitude may be more serious than one extreme event in estuary-ocean interaction region. Neglecting the combination compound effects of storm surge and fluvial flood may underestimate the flood hazards in coastal areas. Our findings yield valuable insights to compound flood hazards and provide scientific guidance for prevention and adaption of compound flood disasters in estuary-ocean interaction region.