Abstract
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 km2). 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.
Highlights
Flash floods, one of the deadliest natural hazards worldwide (Špitalar et al, 2014), generally result in loss of life and substantial economic damage (Kumar et al, 2018; Saharia et al, 2017; Yu et al, 2018b)
There were two particular large flash flood events exceptions in 1991 (138 events) and 1998 (230 events) when the catastrophic floods were triggered by the monsoon rainfalls in the Yangtze River Basin, resulting in 4 150 people died and directed economic losses of
It can be seen that the potential periodicities with 3-7a, 8-15a, and 21-31a of the time-series flash floods from 1979 to 2015 (Fig. 3a) were obtained, and significant periodicity with the local higher energy density appeared in the periods of 3-7a and 8-15a
Summary
One of the deadliest natural hazards worldwide (Špitalar et al, 2014), generally result in loss of life and substantial economic damage (Kumar et al, 2018; Saharia et al, 2017; Yu et al, 2018b). Asia and the Pacific are most afflicted compared to any other area of the world, account for over 90% of global disasters and upward trends of flash flood occurrences and impacts (Atif et al, 2021; Kimuli et al, 2021; Singh and Kumar, 2013). A mountainous country covering 2/3 of its area, is most threatened by flash floods with more than 60 000 events during 1949-2015(Yuan et al, 2017). The frequency and mortality of flash floods are the largest in Asia (Hu et al, 2018), and present a significant spatiotemporal disparity due to the complex monsoon climate and diverse geomorphological types (He et al, 2017; Liu et al, 2018; Liu et al, 2017).
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