Abstract
Shanghai, as a coastal city, is vulnerable to various types of flooding. The floodwalls along the Huangpu River provide protection against typhoon-induced flooding. However, there is limited insight into the actual safety level of the flood defences in Shanghai, and recent failures have highlighted their vulnerability. Therefore, the aims of this paper are to derive a series of new flood frequency curves for the Huangpu River, and to evaluate the level of protection of the floodwall system. This paper analysed over 100 years (1912–2013) of annual maximum water levels for three stations at near-sea, mid-stream and inland locations along the Huangpu River. Best-fit curves were determined for a number of selected probability distributions using statistical performance indicators. As a result, new flood frequency curves of the water levels for different storm surge return periods were produced. The results showed that generalised extreme value (GEV) was identified as the most suitable probability distribution for the datasets. Analysis showed that the current design water levels correspond to exceedance probabilities of 1/500 per year at the near-sea and mid-stream stations, and no more than 1/50 per year at the inland station of the Huangpu River, whereas the intended safety standard is 1/1000 per year. A comparison of the findings with a dataset of the crest heights of the floodwalls showed that the current protection level of the floodwalls along the Huangpu River is expected to be around 1/50 per year in terms of overtopping for the lowest sections. The results of this study can be utilized to provide future recommendations for flood risk management in Shanghai.
Highlights
In recent years, many cities worldwide have been severely affected by flooding
This paper analysed over 100 years (1912–2013) of annual maximum water levels for hydrological stations at Wusongkou, Huangpu Park, and Mishidu along the Huangpu River in Shanghai
The flood frequency analysis showed that the generalised extreme value (GEV) distribution provides the best characterization of flood frequencies for datasets at three hydrological locations of the Huangpu River
Summary
Many cities worldwide have been severely affected by flooding. Examples of major flood disasters are the river floods in Thailand (2011), Hurricane Sandy in New York and New Jersey (2012) and flooding along the Elbe in Germany (2013). A large and rapidly growing part of the world’s population lives in low-lying coastal zones [1]. These areas have been threatened by extreme events, and in the future risks are expected to increase due to economic and population growth and the effects of climate change. In Southeast Asia, cities such as Tokyo, Jakarta, Ho Chi Minh City, and Shanghai are located in coastal and delta areas and are threatened by potential flooding problems. Many of these cities have implemented flood defence systems to reduce flood risks. The safety standards in The Netherlands are regarded as the most stringent in the world, with safety standards varying between
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