In order to study the defense capability of the sea dike in Shanghai under the condition of sea level rise, a two-dimensional storm surge flood model with integrated sea and land was established. Through model calculation, the following conclusions are given: Under the condition of sea level rise and extreme storm surge, the main sea dike in Pudong area and Changxing Island area have overflowed. The designed protection capability does not match the fortification criteria of its defense against 200-year high tide level and 12-level wind and waves. Shanghai needs to further strengthen the construction of sea dike projects and improve the tide-proof standards.
According to the forecast results of the 2020 China Sea Level Bulletin issued (Ministry of Natural Resources of the People's Republic of China, 2020), the sea level along the Shanghai coast will rise by 50-180 mm in the next 30 years. Based on the estimated results of global sea level changes and the water level data of more than 20 domestic tide gauge stations, domestic scholars have given a forecast that the coastal sea level of China will rise up to 20-60 cm by 2100 (Shen, 1998). Due to the severe land subsidence in the Yangtze River Estuary, the relative sea level rise rate in this region can be 5.44 mm/a, which is about three times the global sea level rise rate (Zhou, 2013). Based on the research of the variation trend of Relative Sea Level Rise (RSLR) in Shanghai in 2030, it is predicted that the RSLR in Pudong is about 8 mm/a, and the RSLR in Changxing and Hengsha Island is about 4-6 mm/a (Cheng, 2015). Fig.1 shows the location map of Yangtze River Estuary, Pudong New District, Changxing Island and Hengsha Island.
Due to the impact of sea level rise and land subsidence, the flood control capability of the sea dike along the coast of Shanghai during storm surge needs to be further investigated. Based on a combination of topographical changes and changes in land cover types, RSLR extends storm surge inland. On the basis of RSLR phenomenon, numerous scholars have carried out in-depth research on extreme storm surge, coastal floods and their effects (including tide level dynamics, submerged extent and seabed deposition, etc.) through numerical simulations (Ferreira, 2014, Chen, 2019, Zhao, 2014, Yi, 2017, Chen, 2015). Its series of achievements are of great significance for disaster prevention and mitigation (Kuang, 2015, Wang, 2018).
