Assessing tropical cyclone compound flood risk using hydrodynamic modelling: a case study in Haikou City, China

Abstract

Abstract. The co-occurrence of storm tide and rainstorm during tropical cyclones (TCs) can lead to compound flooding in low-lying coastal regions. The assessment of TC compound flood risk can provide vital insight for research on coastal flooding prevention. This study investigates TC compound flooding by constructing a storm surge model and overland flooding model using Delft3D Flexible Mesh (DFM), illustrating the serious consequences from the perspective of storm tide. Based on the probability distribution of storm tide, this study regards TC1415 as the 100-year event, TC6311 as the 50-year event, TC8616 as the 25-year event, TC8007 as the 10-year event, and TC7109 as the 5-year event. The results indicate that the coastal area is a major floodplain, primarily due to storm tide, with the inundation severity positively correlated with the height of the storm tide. For 100-year TC event, the inundation area with a depth above 1.0 m increases by approximately 2.5 times when compared with 5-year TC event. Comparing single-driven flood (storm tide flooding and rainstorm inundation) and compound flood hazards shows that simply accumulating every single-driven flood hazard to define the compound flood hazard may cause underestimation.

Compound events and associated impacts in China

“…Compound flooding in coastal areas is commonly defined as the concurrences of anomalies of hydrometeorological variables (e.g., precipitation, surface runoff, river discharge, or streamflow) and oceanic variables (e.g., storm surge, tide, wave, and sea level) ( Bevacqua et al., 2019 ; Hao and Singh, 2020 ; Wahl et al., 2015 ) leading to flooding events. Coastal flooding risks may be underestimated if only the individual flood is considered ( Liu et al., 2022 ; Wahl et al., 2015 ). Early studies have evaluated the joint impact of rainfall and tidal level based on the copula model in several coastal cities of China ( Lu et al., 2022 ), such as Fuzhou ( Lian et al., 2013 ) and Haikou ( Liu et al., 2022 ; Xu et al., 2019 ).…”

“…Coastal flooding risks may be underestimated if only the individual flood is considered ( Liu et al., 2022 ; Wahl et al., 2015 ). Early studies have evaluated the joint impact of rainfall and tidal level based on the copula model in several coastal cities of China ( Lu et al., 2022 ), such as Fuzhou ( Lian et al., 2013 ) and Haikou ( Liu et al., 2022 ; Xu et al., 2019 ). Recently, a systematic analysis of the driving factors and impacts of compound flooding along the coast of China was assessed based on long records of precipitation and storm surge from 11 tide gauges (with overall positive dependence between the two contributing variables), in which a higher likelihood of compound flood events was found during the tropical cyclone seasons ( Fang et al., 2021 ).…”

Perspectives on Compound Flooding in Chinese Estuary Regions

“…In China, high storm surges and extreme rainfall during the typhoon season are the major driving factors of flooding along the coast (Wu et al 2021;Liu et al 2022). Typhoons may produce strong onshore winds and an inverse barometric effect, which result in extreme surges, while simultaneously produce large quantities of rainfall over land, generating surface runoff.…”

Characterization and process understanding of tropical cyclone-induced floods derived from observations in Shenzhen, China

“…Floods induced by tropical cyclones (TC) are of particular concern that the accompanying intense storms and storm surges always have catastrophic effects on the living and production of the urban. The combined impacts of sea level rise, land subsidence, and rapid urbanization would exacerbate these effects and lead to unprecedented socioeconomic loss (Liu et al 2022).…”