Effect of land cover types evolution in megacities on flood regulation capacity: the case of Zhengzhou since 1990

In recent years, extreme weather accidents happen from time to time in China, especially the occurrence of the extremely heavy rainstorm in Zhengzhou on 7·20 in 2021 once again raised a warning to people. In this paper, we firstly analyze the surface cover state change through the land use transfer matrix method, secondly, we assess the urban soil surface flow production and flood regulation capacity under different precipitation scenarios, and finally, we explore the impact of urban surface cover change on urban flood mitigation by using the global Moran’s I analytical method and the cold hot spot analysis method.. The results show that (1) from 1990 to 2020, the construction land in Zhengzhou City expanded rapidly, the impervious surface area in the study area increased from 8.8 to 65.4%, and the proportion of green space decreased from 63.8 to 32.4%. (2) With the increase of impervious water surface area and rainfall intensity, the urban waterlogging regulation ability decreased, and showed a significant spatial agglomeration characteristic. (3) there is a significant correlation between change degree of land cover and changes in urban flood regulation capabilities. Changes in vegetation, water and impervious surfaces have a greater impact on urban flood regulation capabilities.