Classsifcation Of Gullies In Yuanmou Dry-hot Valley

Soil is the material basis for human life and the most basic means of production and environmental conditions,also is the indispensable and nonrenewable natural resources and key components of human environment.Today,under the circumstances of world population growing sharply,food shortages caused by disaster-prone and a growing demand for food,humans accelerate the degree of exploitation and utilization to a variety of land resources,which are shrinking land resource areas used for agricultural production and accelerate the development of soil erosion in varying degrees.Soil erosion has become one of the major environmental issues concerned by all humanity.Gully formation is the formation process of modern landform.Gully erosion is permanent linear incised valley morphology formed on the ground that scoured by streams gathered by rainfall runoff.Modern gully valley system was evolved on the basis of ancient landforms,including entrenched gullies,gullies and channel waterway network.Gully erosion in hilly area of loess plateau is the most developed,and often accompanies or stimulates gravity erosion such as collapse,landslide and cave erosion,gully density can be up to 4-6km/km~2,forming the numerous gullies erosional landform landscape which is specific in the world.Dry-hot Valley is primordial ecological phenomena formed by synthetic action of multiple effects.Due to the dry and hot climate of distinct dry and wet seasons,resulting in soft soil layer,the development of soil vertical joints and cracks,vegetation degradation,and factors such as irrational use of land by human,which exacerbate soil erosion in this region,accelerate the headward erosion speed of gullies;the gullies are extremely developed,forming typical clay forest landscape,for example,the gully density at Shadi can be up to 7km/km~2.The permanent gully has the characteristics of wide distribution,vertical gully walls,fast headward erosion and multiple morphologies.International and domestic have conducted a series of researches for gullies in different areas,such as the morphology of gullies,the relationship between gully sediment yield and soil types and the development process of gullies.In order to better master the types of gullies in Yuanmou Dry-hot Valley and clarify the relationship between the morphology of different gully types and its formation mechanism,this article is studied from the following aspects:(1)Based on the France P satellite remote sensing image data with 0.5m resolution,ENVI 5.1 software was used to conduct steps such as calibration and correction,tessellation and registration,taking advantage of spatial feature extraction module to extract such natural elements as roads,bridges,rivers,lakes,forests and gullies and so on.We used corrective images many times to investigate in field and predicted the factors such as gully types,soil and vegetation and so on in the wild.(2)For this study,we selected 5 gully cluster sites(Tutuji,Julin,Shadi,Maoyi,Laoyatang)in the Yuanmou Dry-hot Valley as the study areas.We randomly selected152 typical gullies,cross-sections of each gully were measured at three locations:gully head(3-5m below gully head),gully body(the middle part of the gully),gully mouth(5m above the gully mouth).There were 456 cross-sections collected by us.(3)The topography of typical regions in study area was measured with the CTI M600GPS and WGS1984 coordinate system.Gully bottom line,watershed line and both sides of the gully were detail measured based on the distances of10cm-100cm,and a total station was used simultaneously to measure with increasing density in where there were obvious topographical changes.(4)Riegl VZ400 was used to scan the typical gullies and the data were spliced in Riegl Scan Pro software,then DEM graphics of the measured gullies were eventually generated.(5)Based on the development stage of the gully,the gully system in the Yuanmou Dry-hot Valley is classified into four types:microrills,rills,entrenched gullies and gullies;according to the continuity of the gully,the gully system in the study area can be divided into two types:non-continuous gullies and continuous gullies.Based on the formation location of the gully,the gully system in the Yuanmou Dry-hot Valley is classified into two types:slope gullies and bank gullies;according to the morphology of the gully cross-sections,the gully system is divided into two types:U-shaped and V-shaped.Combining with such influence factors as geology,landform,vegetation,soil and strata properties in the Yuanmou Dry-hot Valley,we comprehensively discuss the influence mechanism on the formation and distribution of the gully types,which provides some theoretical support for comprehensive treatment to gullies that are in different development stages and to different types of gullies,and also provides some scientific basis for rationally exploiting the land resources,protecting the local environment and creating a harmonious and prosperous agro-ecological system.