Abstract
Compound flooding is generated when two or more flood drivers occur simultaneously or in close succession. Multiple drivers can amplify each other and lead to greater impacts than when they occur in isolation. A better understanding of the interdependence between flood drivers will facilitate a more accurate assessment of compound flood risk in the coastal regions. This study employed the Delft3D-Flow Flexible Mesh model to simulate the peak coastal water level, consisting of storm surge, astronomical tide, and the relative sea level rise (RSLR) in Shanghai over 1961–2018. It then applies a copula-based methodology to calculate the joint probability of peak water level and rainfall during historical tropical cyclones (TCs) and to calculate the marginal contribution of each driver. The results indicate that the astronomic tide is the leading driver to peak water level, followed by the contribution of storm surge. In a longer term, the RSLR has significantly amplified the peak water level. This framework could be applied to other coastal cities which face the similar constraint of unavailable water level records.
Highlights
Compound flooding is generated when two or more flood drivers, e.g., water level, rainfall, and high river discharges, occur simultaneously or in close succession
We focused on the joint impact of peak water level and rainfall in Shanghai, a coastal 265 mega-city located in the Yangtze River Delta region
We showed that Shanghai is prone to compound flooding and this justifies the adoption of a probabilistic modelling framework to incorporate the interdependence of multiple flood-drivers
Summary
Compound flooding is generated when two or more flood drivers, e.g., water level, rainfall, and high river discharges, occur simultaneously or in close succession. Such flood drivers can amplify each other and lead to greater impacts than when they 30 occur in isolation (Leonard et al, 2014; Zscheischler et al, 2018; Visser-Quinn et al, 2019; Chao et al, 2021). Coastal cities like Shanghai are prone to compound flooding associated with tropical cyclones (TCs), which often bring heavy rainfall and storm surge. For a more accurate assessment of compound flood in the coastal regions, a thorough understanding of the interdependence between multiple flood-drivers is necessary.
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