Abstract: Flood disasters are characterized by high frequency of occurrence and strong destructiveness. Risk assessment can reveal high-risk hotspots and their driving factors, which will help to build a scientific and efficient flood control and disaster reduction system. This paper takes the Xunjiang Flood Control Protection Area in the Pearl River Basin as the research object. First, the HEC-RAS hydrodynamic model is constructed to extract the maximum flow velocity and water depth to evaluate the flood risk. Then, the exposure and vulnerability of the disaster-affected body are evaluated by using the AHP and the entropy weight method, considering factors such as population density, GDP, and land use; finally, the flood risk is calculated and the spatial-temporal dynamic changes of the flood risk are analyzed. The results show that: the average hit rate of the hydrodynamic model is more than 80%, and the false positive rate is less than 28%; in the Xunjiang flood protection area, the medium and high risk areas account for more than 5.20%; from 1997 to 2017, the flood risks of different levels were all the same. It is showing an intensifying trend, and it is worth noting that nearly 46.69% of the middle and high risk areas have a significant upward trend. The research results can provide decision support for scientific and efficient flood risk management.

Key words: flood inundation, hydrodynamic simulation, risk mapping, evolution law