Spatial distribution patterns and potential exposure risks of urban floods in Chinese megacities

Serious urban floods are projected to occur more frequently in cities in the future due to continued global climate changes and accelerated urbanization. However, research dedicated to investigating the distribution patterns and exposure risks of urban floods among multiple cities is missing. The urban flood records of 8 Chinese megacities were used to explore the spatial distribution patterns and influencing factors of urban flooding and the potential exposure risks to population, housing value and traffic conditions. The results indicated that among the 8 megacities, Shanghai had the most flood events (264 points), and Wuhan had the highest heavy flood ratio (74.3%). The flood points in all cities were significantly clustered, but the mean distance between flood points in each city was quite different (443-1470 m). The main factors affecting urban flooding in these Chinese megacities were Patch Density of underlying surface, Green Space Ratio and Road Density based on the standardized coefficients of logistic regression. The most vulnerable cities in terms of the total flood exposure risk to the population, housing value, and traffic conditions were Tianjin, Shanghai and Shanghai, respectively. However, the flood points in Tianjin, Beijing and Beijing were the most vulnerable in terms of population, housing value and traffic condition, respectively. According to the exposure risk index results, the exposure risk of each flood point in Beijing was the highest (ERIpoint = 0.57), while the exposure risk of the whole city in Shanghai was the highest (ERIcity = 0.71). The comprehensive urban exposure risk index we proposed based on the potential exposure risks to population, housing value and traffic conditions makes it possible to evaluate socioeconomic vulnerability among different cities and may provide guidance for stormwater management in megacities.

Automated summary

This study analyzes urban flood records from 8 Chinese megacities to investigate the distribution patterns and influencing factors of urban flooding and assess the potential exposure risks to population, housing value, and traffic conditions. The results show significant clustering of flood points in all cities, with different mean distances between flood points. Patch Density of underlying surface, Green Space Ratio, and Road Density were identified as the main factors affecting urban flooding. The most vulnerable cities in terms of exposure risk were Tianjin, Shanghai, and Shanghai, while Beijing, Tianjin, and Beijing were the most vulnerable in terms of specific factors.