Urban flood risk assessment under rapid urbanization in Zhengzhou City, China

With accelerated urbanization and climate change, urban flooding is becoming more and more serious. Flood risk assessment is an important task for flood management, so it is crucial to map the spatial and temporal distribution of flood risk. This paper proposed an urban flood risk assessment method that takes into account the influences of hazard, vulnerability, and exposure, by constructing a multi-index urban flood risk assessment framework based on Geographic Information System (GIS). To determine the weight values of urban flood risk index factors, we used the analytic hierarchy process (AHP). Also, we plotted the temporal and spatial distribution maps of flood risk in Zhengzhou City in 2000, 2005, 2010, 2015, and 2020. The analysis results showed that, the proportion of very high and high flood risk zone in Zhengzhou City was 1.362%, 5.270%, 4.936%, 12.151%, and 24.236% in 2000, 2005, 2010, 2015, and 2020, respectively. It is observed that the area of high flood risk zones in Zhengzhou City showed a trend of increasing and expanding, of which Dengfeng City, Xinzheng City, Xinmi City, and Zhongmu County had the fastest growth rate and the most obvious increase. The flood risk of Zhengzhou City has been expanding with the development of urbanization. The method is adapted to Zhengzhou City and will have good adaptability in other research areas, and its risk assessment results can provide a scientific reference for urban flood management personnel. In the future, the accuracy of flood risk assessment can be further improved by promoting the accuracy of basic data and reasonably determining the weight values of index factors. The risk zoning map can better reflect the risk distribution and provide a scientific basis for early warning of flood prevention and drainage.