Abstract:

In this paper, the rainstorm flood damage index was used to evaluate a rainstorm flood disaster in Xinjiang, China from 1961 to 2019, and the temporal and spatial variation characteristics of different grades of rainstorm flood disasters were analyzed. Accordingly, the main disaster factors of rainstorm flood disasters in Xinjiang were determined. Based on 3220 rainstorm flood events in 86 counties (cities) of Xinjiang from 1961 to 2019, a disaster loss index for rainstorm flood disaster events was constructed on the basis of the number of deaths caused by each rainstorm flood disaster, the number of collapsed houses, the number of collapsed sheds, the number of livestock deaths, and the affected area, as disaster factors. According to different threshold ranges of the disaster loss index, each rainstorm flood disaster event was divided into four grades—general, heavy, serious, or severe-and used to evaluate rainstorm flood disasters of varying intensity in Xinjiang from 1961 to 2019. The areas with the most frequent rainstorms and flood disasters were found to be the Ili River Valley, the Aksu Prefecture, and the Kashi Prefecture, and these three areas also experienced the most severe rainstorm and flood disasters. Most of the areas with more frequent occurrence of less harmful (general, heavy) events were concentrated in northern Xinjiang. With the increase in hazard levels, the number of and serious rainstorm flood disasters in most areas of northern Xinjiang decreased rapidly. The average number of events in areas in southern Xinjiang, such as the Aksu Prefecture and Kashi Prefecture, was obviously more than that in other regions of Xinjiang. The number of events of each hazard grade in the Ili River Valley has been moderate to high to other regions, although the number of heavy-grade events has sharply risen. The Ili River Valley has the greatest annual precipitation of any region in Xinjiang. The frequency of short-term heavy precipitation in the Aksu and Kashi regions is also high, providing a material basis for rainstorm flood disasters. The heavy rain and flood disasters in Xinjiang mostly occur in summer, with the most common months being June and July. The pattern is the same regarding the precipitation, the number of days above the heavy rain threshold, and the maximum number of days above the heavy rain threshold. In the mid-1980s, there was a sudden change in the occurrence of rainstorm flood disasters in Xinjiang. Since then, precipitation in Xinjiang from March-October has increased, and extreme precipitation events have also increased. There have also been increases of 3.8-5.6 times in the number of occurrences, annual occurrences, and the annual disaster loss index of rainstorm and flood disasters at each dangerous grade. Precipitation and precipitation days above the heavy rain threshold are the main disaster factors in Xinjiang rainstorm flood disasters. These research results can provide a technical basis for the risk assessment of rainstorm and flood disaster factors and for natural disaster risk regionalization in Xinjiang. At the same time, this study of extreme precipitation events also provides direction for future research on the mechanism of rainstorms and flood disasters in Xinjiang.

Key words: heavy rain flood, disaster loss index, classification, space-time differences