Spatiotemporal analysis of flash flooding events in mountainous area of China during 1950–2015

Abstract. Flash flooding is one of the most destructive natural disasters that occur in mountainous areas. Understanding the spatiotemporal characteristics of flash flooding across China is important for enabling better disaster estimation and prevention on the national scale. To bridge the gap in the research of the spatiotemporal characteristics of flash flooding events (FFEs), based on the longest time series of FFEs in China, this paper used Mann-Kendall (MK) test, wavelet analysis, monthly frequency and index of dispersion (D) to detect the temporal variation, temporal periodic and temporal clustering of FFEs in China. The results indicated that: (1) A marked rising in the number of FFEs in China was detected, with a growth rate of 23.62 per year since 1950; (2) On the large scale, the main periodicity characteristics was approximately 12–25 a, with three oscillation periods, and tended to be stable since 1980; On the small scale, the 2–8 a time scale was prominent, with two oscillation periods, and tended to be stable since 2006; (3) The intra-annual frequency distribution of FFEs can be divided into three types, right-skew, left-skew and symmetry; (4) The inter-annual clustering played the dominant role in FFEs occurrence across China, while the under-dispersions were only detected in six (5 %) watersheds. Precipitation anomalies and soil moisture were detected to have a close correlation with FFEs, however, the interplay of climatic variations and anthropogenic activities may impose greatly impacts on the occurrence and evolution of the flash flooding disasters on a large extent. This study provided a preliminary reference for revealing the driving factors of flash flooding disasters in the context of climate change.