| The gully erosion in the arid river valleys in the southwest region is fierce,and it is a key area for soil erosion control.Gully are widely developed in the study area,but the pattern of topographic differentiation at the regional scale is unclear.Among them,the Hanyuan Dry Valleys in the south is one of the specific natural landscapes in the arid river valley in southwest China.The spatial distribution and accumulation of gullies cause fragmentation of the complete slope,which will not only restrict regional agricultural and economic development,but also pose a serious threat to the ecological security of the river basin.Therefore,in order to ascertain the spatial distribution pattern,measurement and influencing factors of gully,this paper takes the Hanyuan Dry Valleys as the research object,and evaluates and divides the accumulation distribution pattern of gully through remote sensing interpretation and spatial statistical analysis.To reveal the topographic differentiation of gully cluster distribution,and to clarify the influence mechanism of topographic factors on gully cluster distribution.This study not only provides an effective reference index for the study of the spatial distribution of gully,but also provides a scientific reference for soil and water conservation work such as soil erosion control by district.The main contents and conclusions are as follows:(1)The gully in Hanyuan area has the characteristics of cluster distribution and distribution in space.According to the statistical analysis results of spatial autocorrelation,Moran's I value is 0.98,which indicates that the kernel density distribution of erosion grooves on the regional scale has non-uniform characteristics and presents a cluster distribution pattern.Based on the evaluation results of kernel density,the degree of cluster distribution of gully is divided into 5 levels:extremely low concentration(0-1.55 km/km~2),low concentration(1.55.0-3.10 km/km~2),and intermediate concentration(3.10-4.65 km/km~2),high concentration(4.65-6.20km/km~2),extremely high concentration(6.20-7.75 km/km~2).Among them,the proportion of low and medium cluster distribution is the largest,accounting for38.78%and 28.82%of the entire research area,followed by the extremely low and high cluster distribution,accounting for 15.63%and 14.68%,respectively,and the proportion of extremely high cluster distribution is the smallest,Only 2.08%.On the whole,the degree of agglomeration distribution in the Hanyuan area is in a medium state.The erosion cluster distributions with extremely high,high cluster distribution and intermediate levels are mainly distributed around the county,and the cluster distribution gully with low cluster distribution and extremely low levels are concentrated in the central part.Regions,and the overall degree of cluster distribution from the middle to the surrounding law.(2)The superposition analysis of the concentration level of gully and the level of geomorphic factors is used to study the distribution of gully with different concentration on topographic factors.The results show that the development of gully has certain regularity on the terrain gradient.The average kernel density of gully increases with the increase of slope,decreases with the increase of surface roughness and the coefficient of variation of elevation,and increases with the increase of elevation,slope length,topographic relief,and surface cutting.At the same time,areas with sub-high altitudes,steep slopes,south slopes,convex surfaces,short slopes,low undulations,low roughness,shallow cutting,and low elevation coefficient of variation account for the largest proportions.And under different terrain conditions,the concentration of gully is different.(3)Gully is mainly affected by terrain conditions in space and presents a clustered distribution.The spatial distribution vector data of core density and topographical factors of eroded ditch are superimposed and correlated,and the results show that:(1)A single topographic factor and erosion are analyzed.The relationship of ditch cluster distribution,among which elevation has the highest correlation with the core density of eroded ditch(?=0.63),followed by topographic relief(?=0.38),surface cutting degree(?=0.38),and surface roughness(?=0.33),Slope(?=0.33),slope length(?=0.33),and coefficient of variation of elevation(?=0.02),but the correlation between profile curvature,plane curvature,slope direction and erosion channel core density is small,and there is no obvious correlation..(2)Analyze the relationship between the dominant terrain factors and the distribution of erosion gully clusters.Three types of analysis methods,such as multiple linear regression,random forest regression,and geographical weighted regression,can reflect the relationship between the distribution of erosion gullies cluster and terrain in Hanyuan area.The goodness-of-fit(R~2)of the multiple linear regression analysis model was 0.43.The established data model did not include the three items of plane curvature,section curvature,and aspect.The R~2 obtained by random forest regression analysis is 0.48,and the importance of the independent variables is ranked as follows:elevation>topographic relief>elevation variation coefficient>surface cutting degree>slope length>slope>profile curvature>surface roughness>plane curvature>slope to.Excluding the presence of multiple collinear elevations,surface roughness,and slopes for geographic weighted regression analysis,R~2 was 0.61.The results show that the fitting goodness of geographic weighted regression analysis is the best,which is greater than the other two regression analysis methods.(3)Analyze the relationship between the combined topographical factors and the distribution of erosion gully concentration,that is,use the topographic fluctuation and altitude as basic indicators to divide the landform types in the Hanyuan area,and calculate the correlation between the landform type and the erosion gully concentration level.The study area is divided into 9 types of landforms,among which the low-lying sub-alpine,medium-altitude hills,low-lying middle-mountain,and sub-high-altitude hilly areas are the main areas for the distribution of erosion grooves,and the concentration of erosion grooves is diverse.At the same time,the tau-y coefficient was calculated to be 0.13,indicating that there is a clear relationship between the types of landforms and the degree of erosion channel accumulation. |
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