Risk assessment of flash flood under climate and land use and land cover change in Tianshan Mountains, China

Abstract

Tianshan Mountains in China (CTM) is one of the flash flood-prone areas worldwide, constraining economic development and threatening human safety. We assessed the short-term and long-term future flash flood risk in CTM using a multi-criteria model combined with future climate and Land use and land cover (LULC). The short-term risk assessment results indicated that moderate, high, and extremely high risk areas were mainly located in the northern foothills of the Tianshan Mountain, the southern Junggar Basin, and the northern Tarim Basin, accounting for about 10 % of the total area. The areas classified as high and extremely high risk were distributed in Ili (10,100 km²), Changji (4838 km²), Bortala (1783 km²), and Urumqi (1505 km²). The spatial distributions of future long-term and short-term flash flood risk are similar. There will be an increase in the flash flood risk from 2020 to 2030, mainly in Ili, Changji, and Hami. The flash flood risk in the CTM will decrease under different scenarios from 2030 to 2070. Historical flash flood data from the 1940s to the 2010s indicated that the results of the risk assessment are reasonable. Abundant precipitation from the westerly circulation and the trumpet-shaped topography drove the flash floods in Bortala-shuanghe(BS), Ili, Changji (west), and Urumqi-wujiaqv(UW). Snowmelt flash floods are another important flash flood type in Changji (West) and UW. The dense water system and the undulating terrain led to rainstorm flash floods in high mountainous areas of Aksu and Kashgar, Hami, Kizilsu, and Changji (east). Cultivated land, population, and roads are important risk receptors. The oases, water resource constraints, and the urban scale discontinuity led to the spatial displacement between hazard and risk. The flash flood risk change in the future is more closely related to LUCC than climate change. This study provides support for flash flood risk assessment and management in CTM and other arid inland areas under changed climate and LULC.