晋西黄土区极端降雨后浅层滑坡调查及影响因素分析

Investigation of Shallow Landslide After Extreme Rainfall and Analysis of Its Influencing Factors in the West Shanxi Loess Region

极端降雨引发的浅层滑坡,造成了严重的环境破坏与社会经济损失。为探究极端降雨条件下土地利用、植被类型和地形因素对浅层滑坡的影响,通过对山西省吉县蔡家川流域2021年10月3—6日极端降雨引发的浅层滑坡进行实地调查,分析了极端降雨的特征与过程,不同土地利用和植被状况条件下、不同地形条件下浅层滑坡的数量与破损面积。结果表明:(1)极端降雨降雨量为年平均降雨量的31.2%,达到了161.3 mm,降雨历时84 h,峰值降雨强度7 mm/h,平均降雨强度2.1 mm/h,发生该种程度降雨的频率为0.16%,为625年一遇的极端降雨。(2)蔡家川流域内的农地小流域、人工林小流域和次生林小流域共计发生浅层滑坡479处,破损面积达183881 m^(2),90%的浅层滑坡面积小于885 m^(2)。(3)单位面积上浅层滑坡的数量与破损面积均表现为农地小流域(214个/km^(2),109241 m^(2)/km^(2))>人工林小流域(163个/km^(2),48779 m^(2)/km^(2))>次生林小流域(42个/km^(2),17176 m^(2)/km^(2)),在小流域尺度上森林植被对浅层滑坡的防治作用显著高于农地,且次生林地预防浅层滑坡的作用优于人工林地。(4)浅层滑坡发生的坡面坡度为10°~80°,浅层滑坡数量与破损面积均随着坡度的增大而增大,在40°~50°达到峰值,坡度>50°后,浅层滑坡数量与破损面积随坡度增大而减少,坡度是影响浅层滑坡的主导因素。(5)浅层滑坡发生在坡向为22.5°~337.5°的坡面上,浅层滑坡数量和破损面积随坡向变化并未表现出明显的规律性,坡向对浅层滑坡的影响不大。

Shallow landslides caused by extreme rainfall have resulted in serious environmental damage and losses.In order to explore the effects of land use,vegetation types and topographic factors on shallow landslides under extreme rainfall conditions,this study conducted a field investigation on shallow landslides caused by extreme rainfall from October 3 to 6,2021 in Caijiachuan Watershed of Ji County,Shanxi Province,and analyzed the characteristics and process of extreme rainfall,the number and damaged area of shallow landslide under different land uses,vegetation and terrain conditions.The results showed that:(1)The extreme rainfall was 31.2%of the annual average rainfall,reaching 161.3 mm,the duration of rainfall was 84 hours,the peak rainfall intensity was 7 mm/h,the average rainfall intensity was 2.1 mm/h,and the frequency of rainfall of this degree was 0.16%.(2)A total of 479 shallow landslides occurred in the small watershed of farmland,plantation and secondary forest in Caijiachuan basin,with the damage area of 183881 m^(2),and 90%of the shallow landslide area was less than 885 m^(2).(3)The number and damage area of shallow landslides per unit area were as follows:small watershed of agricultural land(214/km^(2) and 109241 m^(2)/km^(2))>small watershed of plantation forest(163/km^(2) and 48779 m^(2)/km^(2))>small watershed of secondary forest(42/km^(2) and 17176 m^(2)/km^(2)).At the small watershed scale,the effect of forest vegetation on shallow landslide prevention was significantly higher than that of agricultural land,and the effect of secondary forest was better than that of artificial forest.(4)The slope of shallow landslide was 10°~80°,the number of shallow landslide and the damaged area increased with the increases of slopes,and reached the peak in the range of 40°~50°.When the slope was greater than 50°,the number of shallow landslide and the damaged area decreased with the increases of slopes.Slope was the dominant factor affecting shallow landslide.(5)Shallow landslides mainly occurred on the slope with slope aspect of 22.5°~337.5°.The number and damage area of shallow landslides did not show obvious regularity with slope aspect,and slope aspect had little influence on shallow landslides.