极端降雨对晋西黄土区不同土地利用方式下的浅层滑坡形态特征和空间分布影响

Effects of extreme rainfall on the morphological characteristics and spatial distribution of shallow landslides under different land use patterns in the loess region of western Shanxi Province,northern China

【目的】探究极端降雨对不同土地利用方式下浅层滑坡形态特征和空间分布的影响。【方法】以山西吉县蔡家川农地、次生林、人工林3种土地利用方式的小流域为对象,在2021年10月3日至6日的极端暴雨后采用无人机摄影测量调查浅层滑坡的形态特征和空间分布。【结果】(1)极端降雨在3个小流域内共诱发425处浅层滑坡,总体积为82000 m^(3)。其中农地小流域179处,体积为43138 m^(3),人工林小流域196处,体积为33489 m^(3),次生林小流域50处,体积为5373 m^(3)。(2)核密度分析表明农地小流域浅层滑坡密集程度最高,核密度峰值达到714处/km^(2),且多位于侵蚀沟坡和农地间的斜坡上,次生林小流域的浅层滑坡多沿沟谷分布,人工林小流域浅层滑坡整体沿西北-东南走向的山脊线呈带状分布。(3)农地小流域浅层滑坡主要集中在20°~50°坡度范围和以正东、东南为主的阳坡;次生林小流域滑坡主要分布在40°~50°坡度范围,且受到坡向的影响较小;人工林小流域滑坡集中分布在50°~60°坡度和以正东、正西为主的坡向。【结论】本次调查发现在小流域尺度上植被能够有效减少极端暴雨造成的浅层滑坡,尤其次生林防治浅层滑坡的效果更佳。因此,在全球气候变化背景下,黄土高原大力营造仿拟自然植被,对提高植被的水土保持功能具有重要意义。

[Objective]This paper aims to explore the influence of extreme rainfall on the morphological characteristics and spatial distribution of shallow landslides under different land use patterns.[Method]In this paper,the morphological characteristics and spatial distribution of shallow landslides were investigated by UAV photogrammetry after the extreme rainfall from October 3 to 6,2021 in the Small Watershed of Caijiachuan Farmland,secondary forest and plantation in Jixian County,Shanxi Province of northern China.[Result](1)Extreme rainfall induced 425 shallow landslides in three small watersheds,with a total volume of 82000 m^(3).Among them,there were 179 landslides with a volume of 43138 m^(3)in the small watershed of farmland,196 landslides with a volume of 33489 m^(3)in the small watershed of planted forests,and 50 landslides with a volume of 5373 m^(3)in the small watershed of secondary forest.(2)The analysis of kernel density showed that the shallow landslides in the small watershed of farmland had the highest density,and the peak of kernel density reached 714 per km^(2),and most of them were located on the erosion slope and the slope between farmlands.Most of the shallow landslides in the small watershed of secondary forest were distributed along ravines,and the shallow landslides in the small watershed of plantation were distributed in strips along the northwest-southeast ridge line.(3)Shallow landslides in small watershed of farmland were mainly concentrated in the slope range of 20°−50°and the slope direction mainly due east and southeast.Landslides in small watersheds of secondary forests were mainly distributed in slopes of 40°−50°and were less affected by slope aspects.Landslides in the small watershed of plantation were concentrated in the slope of 50°−60°and the slope aspects mainly due east and west.[Conclusion]This survey shows that vegetation can effectively reduce the shallow landslides caused by extreme rainstorms in small watershed scale,especially the secondary forest has a better effect on preventing shallow landslides.Therefore,under the background of global climate change,it is of great significance to build imitation natural vegetation on the Loess Plateau to improve the function of soil and water conservation.