However, high FPLs can cause “levee effect,” a false sense of security, that can lead to more rapid development in CFAs, further increasing the proportion of urban lands, population, and assets exposed to extreme floods ( Di Baldassarre et al., 2015 Ferdous et al., 2020). Flood protection level (FPL) represents how well a region is protected against flooding, which is generally expressed as the target level of flood return period in designing the flood protection system ( Scussolini et al., 2016 Wang et al., 2021). Improving flood protection, such as by building levees or dykes, can substantially reduce the probability of flood inundation in CFAs ( Ward et al., 2013 Di Baldassarre et al., 2018).
1626865711278.jpg "china flood 2013")
Therefore, flood risk management in CFAs is critical to achieve the sustainable development goals prompted by United Nations ( Reichstein et al., 2021). Unfortunately, they are also characterized by a high density of population and land use, which will probably see a further increase during the rapid urbanization process ( Jongman et al., 2012 Willner et al., 2018). The CFAs are vulnerable to changing climate, a combined result of sea-level rise, land subsidence, and a potential increase in the probability and intensity of storm surges ( Du et al., 2020 Muis et al., 2020). Flood adaptation strategies should be applied to include conserving the coastal ecosystem.Ĭoastal flood-prone areas (CFAs) are low-lying areas that are below extreme sea levels and hydrologically connected to the sea ( Bilskie et al., 2014 Muis et al., 2016). These findings suggest that special attention should be paid to coastal landscape changes in the areas of low flood protection levels to reduce flood risk and ensure sustainable cities and communities. Particularly in counties with low flood protection levels (<50 years), the urban lands expanded by 9.40% annually, 1.44 times that of the whole CFAs moreover, a large portion (39.58%) of the new urban lands were reclaimed from sea waters. The urban lands increased rapidly in the CFAs across all flood protection levels, with an average annual change rate of 6.51%, which was 2.17 times that of non-CFAs (3.00%) and 3.68 times that of the exposed population growth rate (1.77%). It was found that in 2020, the urban lands accounted for 16.35% of the CFAs, 1.81 times that of the non-CFAs (9.04%). To fill this research gap, this study investigated the spatio-temporal changes of urban land expansion in Chinese CFAs and explored their relationships with flood protection levels during 2000–2020. However, little is known about the potential divergences of coastal urbanization across different flood protection levels in the CFAs of China. Understanding the characteristics of urbanization under different flood protection levels is vital for sustainable development in coastal flood-prone areas (CFAs). School of Environmental and Geographical Sciences, Shanghai Normal University, Shanghai, China.
Yijing Wu, Jingwei Li*, Dan Wang, Ling Li, Wendi Shao and Shiqiang Du*
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