| Wudu District is one of the most severe landslide and debris flow disasters in Gansu and even the whole country.The ravines crisscross,high mountains and deep valleys,steep peaks and steep slopes,and heavy rains in wudu region provide favorable geological and meteorological conditions for the development of landslides and debris flows,and a large number of landslides in the basin provide abundant provenance conditions for debris flows.The material types of the main cover layers in the small watersheds in different parts of the area are different,and the types of debris flows that occur are different.This article selects distribution in the district representative coating is given priority to with phyllite weathering of gravel soil and loess and tertiary red colluvial deposit layer of gravel soil mud bay,two typical small watershed of horse and so on as the research object,using respectively in view of the deep and shallow landslide SCOOPS3D model and TRIGRS model,for different rainfall conditions of deep,shallow landslide risk quantitative evaluation.The main understanding obtained in this paper is as follows:(1)In the niwangou river basin,the areas of the high risk areas of shallow landslides were 0.70 km~2,0.89 km~2,1.21 km~2 and 1.41 km~2,respectively,when the maximum rainfall occurred once in ten years,once in twenty years,once in fifty years and once in one hundred years.The areas of deep landslides in the high-risk areas were 1.74 km~2,1.99 km~2,2.50km~2,and 2.65 km~2,respectively.The areas of deep landslides in the high-risk areas increased successively from 16.3%to 24.7%compared with the current conditions.(2)In the macougou river basin,when the maximum rainfall occurred once in ten years,once in twenty years,once in fifty years and once in one hundred years,the areas of the shallow landslide with high risk in non-loess areas were 0.33km~2,0.39km~2,0.52km~2 and 0.55km~2,respectively.The shallow landslide areas in the high-risk areas of loess region were0.45km~2,0.51 km~2,0.66 km~2 and 0.72 km~2,respectively.The shallow landslide areas in the high-risk areas of loess region and non-loess region increased from 2.4%to 4.1%,and the non-loess region increased from 3.3%to 5.4%.The areas of high risk of deep landslide in non-loess areas were0.42 km~2,0.52 km~2,0.73 km~2 and 0.79 km~2,respectively.The areas of deep landslides in the high-risk areas of loess areas were 0.63 km~2,0.69 km~2,0.77 km~2 and 0.83 km~2,respectively.The area of deep landslide in loess area and non-loess area with high risk increased from 3.1%to 5.9%,and that in non-loess area increased from 4.7%to 6.2%.(3)Under the same rainfall condition,the area of the deep landslide in the high risk area in niwangou basin is much larger than that of the shallow landslide,indicating that the sensitivity of the deep landslide to rainfall is greater than that of the shallow landslide.The area of the deep landslide is slightly larger than that of the shallow landslide,indicating that the sensitivity of the deep landslide to rainfall is slightly greater than that of the shallow landslide.The reason is that there are more loess in macougou valley,the permeability of loess is relatively low,the surface layer is more sensitive to rainfall,so it is easy to occur shallow landslides.The soil in niwangou basin is mainly gravel soil,with loose soil layer and strong permeability,which makes it easier for rainfall to penetrate into the slope.As a result,the increase of pore water pressure on the sliding surface of gravel soil is more obvious than that of loess,so deep landslides are prone to occur. |
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