Abstract:

Extreme climate events caused by global warming and their impact on human lives have been comprehensively explored. One of these events is flooding, which has a very complex occurrence mechanism. Rainfall and underlying surface factors, including vegetation, landform, and soil, are closely related with the occurrence of flood. Among them, rainfall is the consequential external force factor that causes floods. In the fifth-grade river basins in Shaanxi Province in the hinterland of mainland China, numerous short-duration, strong-intensity local rainstorms are observed in summer. Therefore, the main flooding type in this province is induced by rainstorms. In this study, Shaanxi Province, which has obvious zonality, was considered as the research object. The spatial differentiation of rainfall-induced flooding and carrier exposure characteristics of the five-level basins in the region was explored through hydrology, meteorology, POP, GDP, basic geographic information data analysis, statistical analysis, three-parameter power function method, K-S test, spatial analysis, and other methods combined with “Shaanxi Province Rainstorm and Flood Disaster Risk Analysis System”. The distribution of flood-induced return periods was analyzed in each five-level basin under different precipitation scenarios. ArcGIS spatial analysis method was used to examine the spatial differentiation patterns of flooding caused by a decrease in water levels under different scenarios in the fifth-grade watersheds of Shaanxi Province. Based on this, the spatial and temporal characteristics of flooding induced by precipitation in this region were evaluated, and the exposure of the disaster-bearing body in the study area was discussed. The prediction and early warning and disaster prediction assessment of precipitation-induced flooding were conducted in the study area to create a layout of human social, economic, and agricultural activities and provide scientific basis for disaster prevention and mitigation. The results show that (1) the distribution of floods in Shaanxi Province under heavy rain scenarios is low in the south and high in the north. The distribution of floods in central and southwestern regions is lower. (2) The regional distribution of the critical surface rainfall during the return period is close to contour distribution, and the extreme value of the contour increases. (3) Upward and downward trends of carrier exposures in different return periods are observed in low- and medium-risk areas and high-risk and extremely high-risk areas, respectively. The once-in-a-ten-year return period exposure first increases rapidly and subsequently increases gradually. The upward trend ten during the once-in-a-hundred-year return period occurs slowly at first and rapidly thereafter.

Key words: five-level basin, spatial difference, critical surface rainfall, flooding