2.1. Historical Events and Flood Protection of Shanghai
Shanghai has witnessed frequent extreme flooding induced by TCs. 148 TCs
affected the region from 1949 to 2015 (Wang et al., 2017), among which
19 and 72 TCs generated storm surges of higher than 1.2 and 0.8 m,
respectively. The annual maximum water levels (Fig. S1) were generally
caused by the high tides and storm surges. For example, the arrival of
Typhoon Winnie’s peak surge (2.35 m) coincided with the high
astronomical tide, resulting in the highest storm tide (5.99 m) on
record in Shanghai. In response to rising record levels, a flood defense
system (floodwall along Huangpu River and seawall along the coast) was
initiated in 1950s and has been reinforced since then (Fig. S1). Each
update of protection standard is triggered by an extreme TC flood event
(i.e., typhoons in 1962, 1974, 1981 and 1997), which heavily inundated
the city (Xian et al., 2018). At present, Shanghai is protected by
480-km high level (1000-years) floodwalls and 508-km high standard
seawalls which are designed to withstand a 100/200-year storm tides plus
waves induced by 11/12-force winds (Saffir-Simpson Hurricane Category
1). In addition, rainfalls and river discharges are regulated by storm
sewer drainage network and the dams/barriers/sluice gates, in order to
prevent the compounding effects of pluvial, fluvial and coastal flooding
(Yin et al, 2015; Xian et al, 2018).