Natural climate change and social population ageing reconstruct the flood risk gap between inland and coastal cities in China

Our world is facing two important challenges, climate change and population aging. Extensive research provides insights into their impact on flood risk, while the extent to how inland and coastal cities are unequally affected remains unclear. This study uses the precipitation and population data across ten years with geographic and statistical methods to show the flood risk gap between inland and coastal cities has been narrowed in China. The results show that the change rate of average precipitation in inland cities is around 2.3% higher than in coastal cities from 2009 to 2021. Compared to 2010, inland cities in 2020 face over 1.5 times the flooding volume, and around 1.6 times the elderly percentage, causing increasing flooding risk to many small cities in the north. The change rates of these aspects are 31.55%, 4.65%, and 6.40% higher than in coastal cities. Therefore, even coastal cities still suffer close to twice as high flood risk as inland cities in 2020, this multiplier gap has been narrowed by 0.14 compared to a decade ago. This highlights the flood risk in inland cities cannot be ignored and there is an urgent need to improve their disaster management.