Compound flood impact of water level and rainfall during tropical cyclone periods in a coastal city: the case of Shanghai

Abstract

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 would facilitate a more accurate assessment of compound flood risk in coastal regions. This study employed the D-Flow Flexible Mesh model to simulate the historical peak coastal water level, consisting of the storm surge, astronomical tide, and relative sea level rise (RSLR), in Shanghai over the period 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 astronomical tide is the leading driver of peak water level, followed by the contribution of the storm surge. In the longer term, the RSLR has significantly amplified the peak water level. This study investigates the dependency of compound flood events in Shanghai on multiple drivers, which helps us to better understand compound floods and provides scientific references for flood risk management and for further studies. The framework developed in this study could be applied to other coastal cities that face the same constraint of unavailable water level records.

Combining statistical and hydrodynamic models to assess compound flood hazards from rainfall and storm surge: a case study of Shanghai

“…Daily rainfall is collected from the China Meteorological Administration (CMA, http: //data.cma.cn/) Meteorological Data Center, covering the period from 1961 to 2018. More specifically, the reanalysis dataset of storm surge peaks from 1961 to 2018 located at the mouth of the Huangpu River (Figure 2) and associated rainfall used here is the same as the one described and used in Xu et al (2022) and the reader is referred to that paper for further details on data processing. To obtain hourly boundary conditions, a representative hourly storm surge pattern and hourly rainfall hyetograph are selected from the Shanghai Municipal Water Authority and CMA.…”

“…At the same time, hydrodynamic models have been widely used to simulate flood extent due to single or multiple flood drivers (Yin et al, 2016;Wang et al, 2018;Shi et al, 2020). Hydrodynamic models are effective in simulating the consequences of rainfall-runoff and storm surge during typhoon events (Kumbier et al, 2018;Bevacqua et al, 2019;Zellou and Rahali, 2019) and can improve our understanding of region-specific hydrodynamics and the genesis mechanisms of compound flooding scenarios (Xu et al, 2022). Such numerical models necessitate boundary conditions, which include hourly timeseries of sea water level and rainfall data, to ensure precise and effective simulations of inundation extent and depth.…”

Analysis of Compound Flooding in the Cakung Drain Area, DKI Jakarta Province

“…In this coastal area, there is the potential for compound flooding. Compound flooding occurs when multiple flood-inducing factors, such as elevated water levels, precipitation, and increased river discharge, coincide or closely follow each other [9]. Within the Cakung Drain area, the risk of compound flooding emerges when there is a substantial discharge from the upstream coinciding with a high tide downstream, leading to an elevated water level downstream compared to normal conditions.…”

Compound Impact of Storm Surge and Flood Characteristics in Coastal Area Based on Copula

“…Yet, hydrologic variables are interdependent and do not typically share the same marginal distribution. Mahmoudi et al and Xu et al [26,27] evaluated the compound effects of storm surges and precipitation on a coastal city's flood risk. Both studies highlighted that the combined impacts of surges and precipitation far exceed their individual effects; this is often overlooked in current flood defense designs.…”