Urban flooding is a natural disastrous event which takes place when heavy rainfall exceeds the drainage capacity of a city. Urban floods frequently occur in megacities worldwide and cause major economic losses due to the rapid development of urbanization and the changes in global climatic conditions.

With the aim of investigating spatial patterns and driving factors of urban flooding in megacities in China, Dr. LI Chunlin, associate professor from the Landscape Ecology Research Group of the Institute of Applied Ecology (IAE) of the Chinese Academy of Sciences (CAS), together with his colleagues, analyzed flood records of eight megacities in China (Beijing, Guangzhou, Nanjing, Shanghai, Shenzhen, Tianjin, Wuhan and Xi'an) using landscape ecological approach and spatial statistics.  

The researchers found that the main factors driving urban flooding in the eight megacities were Green Space Ratio, Patch Density of underlying surface and Road Density, and that the spatial patterns of flood points in all cities were clustered, mainly in the central urban areas.

The urban flood exposure risk index, a new comprehensive index proposed by the researchers, established the link between urban flooding and socioeconomic conditions such as urban population, housing value and traffic conditions. By using this index, the researchers compared the risks of urban floods to socioeconomic conditions of the eight Chinese megacities.

The study showed that the Urban Exposure Risk Index has good performance and value in guiding urban flooding evaluation and management.

This study, funded by the National Natural Science Foundation of China and the Youth Innovation Promotion Association of CAS, has been published in Journal of Hydrology entitled "Spatial distribution patterns and potential exposure risks of urban floods in Chinese megacities."