Assessment Of Gully Cluster Pattern In Dry-hot Valley Based On GIS

The gully is the result of the depth development of soil erosion and the advanced stage of the ditch erosion sequence,which will seriously impede the coordinated development of regional resources,environment and social economy.In dry hot valley,gully erosion activities are intense,gullies are developing very well,and the accumulation and distribution of gullies in space cause surface fragmentation,which not only restricts the development of regional agriculture and economy,but also poses a serious threat to river basin ecological security.Therefore,the purpose of this article which based on the Arc GIS platform is to ascertain the distribution pattern of proven gullies in space,measurement methods of gully cluster research from gully system angle,and cluster distribution pattern of gully space evaluation,finally through the gully distribution data and topography(elevation,slope,slope,lithology and correlation analysis)the soil,analyzed the influence mechanism of gully cluster distribution in space.The main contents and conclusions are as follows:(1)There are three evaluation methods : Kernel density analysis,gully density analysis and hotspot analysis,in which the kernel density analysis is best.Based on the results of the analysis,the gully cluster is divided into five levels: extremely low cluster,lower cluster,medium cluster degree,higher cluster degree,and extremely high cluster.The proportion of medium cluster and low cluster is the largest,which accounts for 26.7% and 25.7% of the whole study area,respectively.The second is extremely low cluster degree(19.6%)and higher cluster degree(19.5%),and the proportion of extremely high cluster is the smallest,only 1.4%.As a whole,the distribution of gully in the dry hot valley is in the middle state,and the high cluster is only a small part.(2)Under the influence of topographic and geological conditions,the gully has different clusters in the spatial cluster distribution.From the main groove angle,according to the combination form of main trench and branch ditch,the gully morphology were classified into three types: linear type,“Y” type and fold line type,in which the gully clustering degree of “Y” type and polygonal line type are higher than straight line type.From the angle of the gully system,according to the method of river morphology classification,the cluster morphology of gully system were classified into four types: arborization,leaf,lattice,and parallelism,in which the dendrite cluster morphology is the most widely distributed,and its clustering degree is the highest.The distribution pattern of parallel cluster is the least and its clustering degree is the lowest.(3)The cluster degree of gully in the space can reflect the erosion degree of the soil in the region.It is applied to the treatment of gully in dry hot valley,based on the division result of gully cluster degree.In the region of extremely low cluster degree and lower cluster degree,the treatment of the gully focus on the prevention.In the region of medium cluster degree,the method of combination of vegetation measures and engineering measures is adopted in the treatment of gully.In the region of higher cluster degree and extremely high cluster degree,on the basis of the combination of vegetation measures and engineering measures,gully management can also develop the economy of gully slope.(4)The superposition analysis and correlation analysis of the spatial distribution vector data of the hedge ditch with the altitude,slope gradient,slope aspect and soil,the results show that the relationship between gully density and slope gradient is parabolic.The total length of gully increases with the increase of slope.When the slope exceeds a critical value(16.5 degrees),the total length of gully decreases with the increase of slope.The intensity of gully has a parabolic relationship with the altitude,and the density of the gully increases first and then decreases with the increase of altitude.Gully density in different slopes(shady slope,sunny slope,and flat)is bigger in the shady slope than that of in the sunny slope,and the flat is least.Take the dry-hot valley in Yuanmou as an example,under different soil types,the gully erosion in dryness red soil,purple soil and red soil are more serious,and which in saline soil and paddy soil are weak.The influence of the gully cluster in geological factors are mainly focus on the tectonic movement and lithology.The dry-hot valley is in the rising area of the neotectonic movement,and the soil erosion is serious.The strata of the dry-hot valley in Yuanmou have the characteristics of late deposition,poor cementation,and soft and hard interbedding,which are important factors in the development of gully.