Analysis of Changes in Rainfall-Runoff Process of Dakeng River in Guangzhou Before and After Urbanization

As the level of urbanization in China gradually increases, the effects of urbanization on rainfall-runoff processes have received increasingly widespread attention. Studying the effects of urbanization on rainfall-runoff processes is of significant importance for the prevention and control of urban rainstorm flood disasters. Based on multi-year hourly rainfall-runoff data before and after urbanization in the Dakeng River Basin in Guangzhou, this study analyzes the characteristics of changes in rainfall-runoff processes before and after urbanization using digital filtering and the Boussinesq equation to separate base flow. The results indicate: ① Land use has changed under the increased urbanization rate of the Dakeng River Basin, with natural soil being transformed into impermeable surfaces such as roads, buildings, and other artificial facilities. The increase in impermeable surface area and hardening of underlying surface result in increased surface runoff, peak flow and runoff coefficient, and decreased basin lag time. ② The increase in surface runoff coefficient and peak flow after urbanization is directly proportional to the total precipitation. A possible reason is that the reducing capacity of urban rainwater pipe networks on runoff and the weakening effect of urbanization on infiltration both affect the rainfall-runoff process differently depending on the total precipitation. These changes will pose new challenges for water resources management and flood control in the Dakeng River Basin.