Spatiotemporal variation of flash floods in the Hengduan Mountains region affected by rainfall properties and land use

Understanding the spatiotemporal characteristics of flash floods is important for reasonable and accurate identification of high-risk regions and for prediction of future hydrological regimes. Therefore, using time series datasets (1979-2015) of historical flash flood events, rainfall, and land use in the Hengduan Mountains region (HMR) of China, this study analyzed the effects of changes in precipitation and land use on spatiotemporal variation of flash floods. Analysis of the linear trend revealed that flash floods increased by 12 events/10 years and that 82% of events occurred in the flood season (June-August). The increase in flash flood events was found closely correlated with the increased frequency (rainstorm days increased by 3.5 d/10 years) and magnitude (rainstorm amount increased by 10.2 mm/10 years) of heavy rainfall as well as the expansion of the area of artificial surfaces (increase of 999 km(2)). Morlet wavelet analysis revealed significant periodic variation in the occurrence of flash floods on scales of 3-7, 8-15, and 21-31 years. On the basis of the standard elliptical difference, we identified displacement of the center of gravity of flash flooding from the northwest toward the southeast. Generally, more disasters were recorded in southern parts of the HMR owing to the frequent occurrence of rainstorms and the increase in area of both cultivated land and artificial surfaces with higher runoff potential. These findings improve understanding regarding the spatiotemporal dynamics of flash floods in the HMR and could support policymakers in identifying high-risk areas in mountainous watershed.

Automated summary

This study analyzed the effects of changes in precipitation and land use on spatiotemporal variation of flash floods in the Hengduan Mountains region of China. It found that the increase in flash flood events was closely correlated with the increased frequency and magnitude of heavy rainfall as well as the expansion of artificial surfaces. The study also revealed significant periodic variation in the occurrence of flash floods on various scales and identified a displacement of the center of gravity of flash flooding in the region.