| China’s highway construction is developing rapidly,and in order to meet the demand of soil and water conservation monitoring work at this stage,the application of UAV lowaltitude remote sensing technology instead of traditional monitoring methods in soil and water conservation monitoring work of production construction projects not only saves human and material resources,but also can obtain key monitoring data of monitoring objects in a timely,comprehensive and accurate manner,which has strong research value and practical significance.In this study,the disposal site numbered 1# and 2# in the section from Jinyang to Pujiang of Chengdu Economic Zone Ring Highway was used as the research object.The DJI Genie 4 UAV was used to collect external data from the study area,and Agisoft Photoscan Professional software was used for internal processing to obtain key monitoring data of the disposal site--Orthophoto and DEM data.Based on this,the soil erosion classification and grading indexes in the "Soil Erosion Classification and Grading Standard"(SL190-96)issued by the Ministry of Water Resources of China were used to assess the degree of soil erosion in the study area,taking into account the implementation and operational efficiency of soil and water conservation measures.The main results obtained from the study are as follows:(1)Based on the data obtained from the UAV low-altitude remote sensing images,which contain only red,green and blue bands,several representative visible vegetation indices were compared and analyzed to select the vegetation indices applicable to this study.The results of each visible vegetation index were calculated and correlated with the normalized vegetation index(NDVI),which reflects the background influence of plant canopy,obtained after processing with the remote sensing image of HMS-2,and the accuracy was evaluated,and the accuracy of the visible vegetation difference index(VDVI)in estimating vegetation cover reached 88.859%,which proved that VDVI is applicable to this study and can extract vegetation cover situation with high accuracy.Based on VDVI as one of the features,support vector machine and random forest were used to classify the land cover types of the disposal site respectively,and the results showed that random forest was more suitable for this study.(2)After the initial effect of soil and water conservation measures,it is necessary to monitor and analyze for a period of time in combination with each soil erosion impact factor.When the area of grassland and the area of high vegetation cover class increase,the change of the proportion of the area of each slope class should be considered.If the area of high slope grade increases(high slope,steep slope),it only indicates the existence of plants adapted to the growth of high slope environment at the site,and it will still appear that the soil and vegetation will be carried away by rain water,increasing the risk of soil erosion.It indicates that if the natural restoration of soil and water conservation measures for the disposal site is not effective,the risk of soil erosion can be reduced by human intervention,such as changing the land cover type.(3)The soil erosion factor has little influence on the soil erosion grade of slight degree,and the area share of light and moderate soil erosion is mainly influenced by the land cover type and vegetation cover.In the flat area,the area of soil erosion grade is mainly influenced by land cover type and vegetation cover;when the topography is obviously undulating,the area of soil intensity erosion and above grade is influenced by the proportion of area of high slope grade area.When the area share of each slope grade and vegetation cover do not change much,the area share of soil erosion grade is basically unchanged.. |
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