| Loess Plateau,with the largest loess distribution area and the thickest loess accumulation thickness in the world,is not only the environmental fragile area of China's ecological system,but also the explosive and frequent area of geological disasters in China.Thousands of loess landslides are distributed in Loess Plateau,which aggravates soil erosion and seriously threaten to people's life,property and national economic construction.Therefore,it is particularly urgent to deeply explore the spatial pattern and distribution rules of loess landslides and reveal the impact of loess landslides on geomorphic evolution.Based on vast investigations and practices of loess landslide in Loess Plateau,the detailed loess landslide data was catalogued.On this basis,loess landslides were taken as the research object,and loess landslides and geomorphologic evolution were regarded as an entry point.Some theories and techniques of geography,geology,geomorphology,surveying,rock and soil mechanics,hydrology,numerical simulation,“3S”technology,UAV photogrammetry,3D modeling and landslide monitoring and warning were integrated to research the spatial pattern of loess landslide and its effect on landform,from a variety of spatial scales,such as the whole loess plateau region-typical watershed?typical topographic area?-typical single landslide.There are three main innovation points in this study:?1?The characteristics of loess landslide and its effect on geomorphology were studied by means of advanced measuring technique;?2?It is found that large-scale loess landslide plays an important role in the local geomorphic evolution of Loess Plateau and often accelerates the abrupt change of geomorphic evolution;?3?Typical models between landslide,soil erosion and geomorphic evolution in Loess Plateau are proposed.This study enriched the Loess Plateau's landform evolution research both in theory and in practice,at the same time laid the foundation of furtherly studying the interaction mechanism of soil erosion,loess landslides and geomorphological evolution in the Loess Plateau.Also,this study provided scientific support for the risk reduction of landslide hazards,and provided a scientific basis for the construction of ecological civilization.The main research results are shown below:?1?Up to now,the largest number of high-resolution loess landslide catalog?307 loess landslides in total?in Loess Plateau has been completed in this paper.Based on the results of high-resolution and high-precision landslide survey and landslide cataloging,the characteristics of loess landslides can be well studied,which provides data support for the study of the relationship between loess landslide and geomorphological evolution.Meanwhile they provided a data support to furtherly research the relationship between loess landslides and geomorphologic evolution.?2?Spatial autocorrelation is obvious in the spatial distribution of loess landslides,which is reflected by the clustering characteristics of thier scale grades,including five clustering modes:insignificant clustering,high clustering?HH?,high and low clustering?HL?,low and high clustering?LH?and low and low clustering?LL?.Positive-skewed distribution and normal distribution can be well used to severally describe the elevation frequency distribution and the main slope aspect frequency distribution of loess landslide.Landslide prone counties in Loess Plateau are dominated by low and middle prone areas,with low prone counties accounting for 59%,middle prone counties accounting for 18%,high prone counties accounting for 14%,and extremely high prone counties accounting for 8%.According to the density spatial distribution of loess landslides,regional tectonic conditions,topography,geology and physiognomy,Loess Plateau can be divided into eight landslide prone areas:?1?Xining-Lanzhou-Linxia-Dingxi prone area,?2?Baiyin-Dingxi-Tianshui prone area,?3?Guyuan-Pingliang-Xifeng-Tongchuan prone area,?4?Baotou-Hohhot prone area,?5?Loess Plateau of northern Shaanxi prone area,?6?Fen-Wei basin prone area,?7?Luliang mountains prone area,?8?Sanmenxia-Jincheng-Changzhi-Yangquan-Wutai mountains prone area.?3?Sensitive area of landslide in Loess Plateau is almost the same as non-sensitive area.Non-sensitive area of loess landslides in Loess Plateau is 298 069.00 km2,accounting for47.16%of the total Loess Plateau area.The area of the low-sensitive area is 62 926.20 km2,accounting for 9.96%of the total Loess Plateau area.The area of the moderately sensitive area is 93 217.70 km2,accounting for 14.75%of the total Loess Plateau area.The area of the highly sensitive area is 133 143.00 km2,accounting for 21.06%of the total Loess Plateau area.The extremely sensitive area is 44 703.20 km2,accounting for 7.07%of the total Loess Plateau area.?4?The theory and method of digital topographic analysis are applied to the study of loess landslides,which lays a foundation for the further study of the characteristics of loess landslide,such as morphological characteristics,topographic and geomorphic changes,stability and profile structure,and also provides theoretical and technical support for the in-depth study of the interaction between loess landslides and geomorphic evolution.The basic contents of high-resolution digital topographic analysis of loess landslides should include extraction and analysis of characteristic parameters,hydrological analysis,topographic change monitoring analysis,hypsometry and stability analysis,morphological analysis and structural analysis.?5?Although soil erosion plays an important role in the long process of geomorphic evolution,loess landslide,as a rapid soil erosion phenomenon and surface process,often accelerates the abrupt change of geomorphologic evolution process.The ability of loess landslide to shape the topography should not be underestimated.The large-scale loess landslides strongly affects the local geomorphologic evolution of Loess Plateau.Loess landslide are obviously controlled by topography and landform conditions,in particular,the relative height difference has a strong power law relationship in terms of the maximum sliding distance,perimeter and area of landslides.For example,the relative height difference?x?has a good power exponential relationship with the longest sliding distance?y?,and the fitting formula is as follows:y=0.3626x1.3906?R2=0.7448,whole the Loess Plateau?,y=0.1831x1.5226?R2=0.8346,loess hilly area?,y=3.9846x0.8835?R2=0.3,loess tableland area???6?Long time series and high precision of landslide monitoring in a typical loess tableland area-Southern Jingyang Tableland was executed,the study found that loess landslides could accelerate the reducing of tableland area.The decrease rate was about 3358.7 m2 per year,and the time interval?year?x and the degradation area?m2?y were in line with the linear decreasing trend,fitting formula is:y=-3358.7x+4543.3?R2=0.9589?.Loess tableland landslides not only changed the slope of the original tableland slope,but also have a strong path-dependence.Mechanism of mass occurrence has been found in this region.A complete online monitoring record of landslides showed that loess tableland landslides experienced a deformation and movement process of slow peristaltic movement in early stage-abrupt slipping in interim-local collapse in late stage.A single landslide can cause 16.1 m retreat of tableland edge.?7?Typical models between loess landslide,soil erosion and landform evolution are summarized,the loess hilly region can be roughly divided into four evolution stages??-slow evolutionary stages,?-local evolutionary stages,?accelerated evolutionary stages,?stable evolution stage?,the loess tableland region can be roughly divided into five stages??-slow evolutionary stages,?-local evolutionary stages,?-rapid evolutionary stages,?accelerated evolutionary stages,?stable evolution stage?... |
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