Abstract: Taking Chongqing city as an example, a comprehensive evaluation index system of urban flood disaster risk is established, and the system dynamics model was used to simulate the risk and identify the stress effect of urban expansion. The results show that the risk of flood disaster in Chongqing city presents a nonlinear fluctuation trend with a five-year cycle. During the cycle, the risk rapidly rises to the peak and then decreases year by year. Urban expansion has no significant effect on the risk of flood disaster in Chongqing city, but the rapid expansion increases the vulnerability of urban disaster. The disaster prevention capacity is more sensitive to the response of urban expansion, and can neutralize the stress effect of urban expansion on flood risk. It is suggested that cities should find a balance between expanding size and ensuring safety, and achieve smart, regulated expansion. It should strengthen the construction of disaster prevention infrastructure for new land use, and improve the drainage and emergency planning in the peripheral areas of the city.

Key words: flood, risk, urban expansion, system dynamics, Chongqing city