An integrated framework of coastal flood modelling under the failures of sea dikes: a case study in Shanghai

Qian Ke,Nicholas Savage,Jiangshan Yin,Jeremy D Bricker,Zhan Tian,Shuai Wang,Erasmo Buonomo,Paul Visser,Ralf Toumi,Guangtao Dong,Qinghua Ye,Sebastiaan N Jonkman,Laixiang Sun

doi:10.1007/s11069-021-04853-z

Abstract

Climate change leads to sea level rise worldwide, as well as increases in the intensity and frequency of tropical cyclones (TCs). Storm surge induced by TC’s, together with spring tides, threatens to cause failure of flood defenses, resulting in massive flooding in low-lying coastal areas. However, limited research has been done on the combined effects of the increasing intensity of TCs and sea level rise on the characteristics of coastal flooding due to the failure of sea dikes. This paper investigates the spatial variation of coastal flooding due to the failure of sea dikes subject to past and future TC climatology and sea level rise, via a case study of a low-lying deltaic city- Shanghai, China. Using a hydrodynamic model and a spectral wave model, storm tide and wave parameters were calculated as input for an empirical model of overtopping discharge rate. The results show that the change of storm climatology together with relative sea level rise (RSLR) largely exacerbates the coastal hazard for Shanghai in the future, in which RSLR is likely to have a larger effect than the TC climatology change on future coastal flooding in Shanghai. In addition, the coastal flood hazard will increase to a large extent in terms of the flood water volume for each corresponding given return period. The approach developed in this paper can also be utilized to investigate future flood risk for other low-lying coastal regions.

Highlights

Climate change leads to sea level rise (SLR) and intensification of tropical cyclones (TC’s) worldwide (Bhatia et al 2019; Holland and Bruyère 2014; Knutson et al 2015)
Results from the 4 km simulations driven by the historical HadGEM2-ES projections have shown good frequency of events with respect to observed tracks and an improvement in the representation of TC intensities with respect to the coarser resolution models, while the results for the future simulation under the HadGEM2-ES show a strong increase in intensity, expected from the strong sea surface temperature (SST) warming (~ 3.5 K) in the Western Pacific projected from the HadGEM2-ES simulations
The surface wind and air-pressure fields were converted into spiderweb format (Deltares 2021), which is used as metrological forcing for the hydrodynamic and wave models

Summary

Introduction

Climate change leads to sea level rise (SLR) and intensification of tropical cyclones (TC’s) worldwide (Bhatia et al 2019; Holland and Bruyère 2014; Knutson et al 2015). Wind stress plays a dominant role (~ 90%) in generating surge over broad, shallow continental shelves; the increasing intensification of TC’s will lead to higher SS (Ali 1999). Typhoon-induced flooding has caused massive economic damage and posed great threats to residents in coastal areas (Acosta et al 2016; Pham et al 2018; Yin et al 2013a). Typhoon Hagibis (2019) caused at least 80 deaths, and affected 135,000 people (Tay et al 2020) and substantially damaged coastal infrastructure in Japan (Shimozono et al 2020). It’ is important to carry out quantitative assessment of the potential risk of TC‐ induced SS and flooding for densely populated cities and river deltas (Walsh et al 2016)

Results

Discussion

Conclusion