Abstract:

Oblique photograph technique can realize the modeling and texture acquisition of the top and side facades of the object simultaneously, and can generate a three-dimensional model more accurately than traditional orthophoto photography. Using the UAV oblique photograph technology, the previous, rear, left, right, and positive five flight routes were dynamically monitored in 13 sub-cavities in Qianqian Village, Deqing County, from 2016 to 2017. A total of 6 189 photographs were collected. Using Pix4Dmapper software for air triangulation, orthophoto images and DEM data were generated. TerraSolid software was used for filtering and classification of point cloud data to reduce the impact of vegetation on DEM accuracy. Using ArcGIS software for spatial analysis, quantitative parameters of the slope including slope direction, and different elevations of the collapse, were evaluated in order to determine the distribution of the collapse in time and space. The results show that: 1）Compared with 2016，the total area of collapse erosion in 2017 increased by 16 401.2 m2, with a change rate of 10.21%. This indicates that the collapse in the study area are still developing. 2) In the area with slope less than 40 degrees, the area of collapse in 2017 is larger than that in 2016, and the area of collapse in the range of 0-10 degrees increases the most. The area with the slope of 41 degrees to 80 degrees is just the opposite. 3) the area of collapse is the largest in SE-SW, and the slope of the collapse area in 2016-2017 is primarily located in S-SW, of which the slope area facing SSW is the most obvious, accounting for 21.98 % of the total reduction of the area of collapse. The slope with the most serious overall erosion was concentrated in the south; 4) the most strongly eroded parts are found at elevations of 51–60 m and 81–90 m; the reason for this is that the slope of this section is below 60°, indicating a strong runoff erosion ability Moreover, the slope is long and high, and is prone to collapse. At the elevation of 41-50 m, the volume of collapse in 2017 is larger than that in 2016, results from an increase in the thickness of the accumulation area; 5) The annual erosion volume amount of landslide material in the study area is 1 172.68×10³ m³ for the two years studied. The quality of Unmanned Aerial Vehicle(UAV) measurement data can meet the specification requirements of UAV photogrammetry. It can be seen that the UAV oblique photograph technology is more accurate, more convenient, and less expensive than the traditional investigation methods. It can be applied to a wide range of erosion monitoring studies, and has broad application prospects in geological surveys and soil and water conservation planning.