A Study On The Red Line Division Of Soil And Water Conservation And Soil Erosion In County Level

This study used Hancheng,located in the transitional zone between the Guanzhong Plain and the Loess Plateau of northern Shaanxi,as a study area.This area has complex topography such as mountains,hills,gullies,and loess platform,which is a typical area for studying soil and water conservation or soil erosion.According to the “Technical Guidelines for Delineation of Ecological Protection Red lines” and related research,this paper considered the current status of the natural environment in study area,and used the single factor evaluation methods with high applicability and accuracy to evaluate the soil and water conservation and soil erosion.Based on these works,the scope of the red line area with the actual situation in study area were delineated,it can provide certain scientific basis for the delineation of soil conservation and erosion in area,and offer government's management work some references.Based on ArcGIS 10.3 and ENVI 5.1 software platform,this paper used RUSLE model to select single factors such as rainfall erosivity,soil erodibility,topographic factor and vegetation coverage,the single factor assessment results applicable to the study area were discussed through different calculation methods.The applicability of single factor assessment results for the study area were discussed through different calculation methods.Finally,the result of single factor evaluation is superimposed in different ways,and the spatial distribution map of soil and water conservation sensitivity and soil erosion sensitivity grade is obtained.Through the comparison and analysis of accuracy and applicability,the classification scheme of soil and water conservation and soil erosion red line is determined.This paper draws four conclusions.Firstly,by comparing the accuracy and applicability of different single factor superposition methods,the rainfall erosivity and soil erodibility were applied in the method provided in the “Technical Guidelines for the Delineation of Ecological Protection Red Lines”.Topographic factor is calculated by topographic fluctuation and slope length factor respectively,it is determined that the slope length factor is more suitable for topographic factor.Vegetation coverage factor was evaluated by three methods,the first way is a pixel dichotomy model based on land use type,the second way only used the pixel model,and the third way was based on the land use type and the pixel dichotomy model for hierarchical assignment of vegetation coverage,it is determined that the third way is more suitable for vegetation coverage factor.Secondly,from the perspective of the importance distribution grades of water and soil conservation functions,the proportion of unimportant areas and minor important areas of soil and water conservation in the study area accounted for a large proportion,which area is 1042.63km2,and accounts for 68.29% of total area,this raea mainly distributed in the west of the Yellow River,hills in the middle,coast of the Juhe River,loess platform in south,mountains and gullies in north and northeast,etc.The area above moderate importance is 483.98km2,accounting for 31.70%,it is mainly distributed in the mountainous regions of the northwest and southwest,with a small amount distributed on the banks of the Yellow River and the Juhe River,this area has high vegetation coverage,excellent hydrological conditions,and weak soil erosion,which has a positive effect on soil and water conservation functions.Then,from the perspective of the sensitivity distribution grade of soil erosion,the insensitivity area of Hancheng is 61.95km2,which accounts for 4.06% of the total area,this area is dominated by rivers and reservoirs,and the soil erosion is weak.The mildly and moderately sensitive areas is 1021.62km2,which accounts for 66.92%,such area mainly distributes urban living areas,agricultural planting areas,industrial areas,gentle slopes areas,and mountainous areas with high vegetation coverage.The area of highly sensitive is 326.91km2,accounting for 21.41%,mainly distributed mountainous areas with more gullies in northeast and along the upper reaches of the Yellow River,a small part of them are located hills in middle and deeper gullies of mountainous in the northwest.The area of extremely sensitive areas is 116.13km2,accounting for 7.61%.The common points in this area are concentrated in the gully areas of mountainous,mostly represented by strips,mainly in the northeastern mountainous region and a little in the central area.The last but not the least,the water and soil conservation red line area is 180.25km2,accounting for 11.81% of the Hancheng,the water and soil conservation red line area is mainly concentrated in the Crossoptilon mantchuricum Nature Reserve,a small amount distributed in the central hills,mountainous regions of the northeast and southwest,these areas have high vegetation coverage,relatively flat topography,abundant hydrological conditions,weak rainfall erosivity and soil erodibility.The red line area of soil erosion totaled 116.13km2,accounting for 7.61%,the red line area of soil erosion is mainly concentrated in the northeastern mountainous regions,a small amount distributed in the northwestern and central regions,such areas have steep terrain,dense ravines,high erosive erosivity or soil erodibility,and low vegetation coverage,all of these situations resulting in serious soil erosion,only by strengthening protection can the integrity of the ecological environment and socio-economic sustainable be maintained.