Loess Gully Profile Combination Analysis Based On DEM

Loess Plateau is one of the four major plateaus in China.Under the influence of East Asian monsoon,underlying topography and some other factors,the Loess Plateau has become one of the most typical gully erosion areas in the world.Gully is widely developed in this area.the Loess Plateau is also one of the most important study areas of related research.Gully is the most dynamic and changeable geomorphic unit in the Loess Plateau.While transmitting material and energy,different gullies are connected with each other through runoff nodes.These gullies composite a gully network within the basin,controlling the surface morphology of the basin.In recent years,with the development of remote sensing,geographic information science and other related science,scholars have proposed many methods for studying gully.DEM(digital elevation model)and digital terrain analysis method also provide many new research ideas for the study of gully.Among these methods,longitudinal profile of gully is the most essential method for study gully.However,most of the existing research on gully profile focuses on one or a very limited number of gullies in the basin,and on the individual characteristics of the gully profile.However,It is not enough to reflect the characteristics of a basin only through a few gully profile.The selection of gully profile will affect the results of the analysis,thus affecting the understanding of the overall morphology of the basin.More importantly,these methods ignore the difference between gullies of a basin.It also ignores the group characteristics of the whole gully network.Considering shortcomings of the existing gully researches,this paper proposes the concept of gully profile combination.The gully profile combination is the combination of all the gully longitudinal profiles in a basin.The Loess Gully profile combination refers to the combination of the gully profiles in the Loess Plateau,which reflects the characteristics of the gully network in different basins of the Loess Plateau.Considering the individual characteristics of each gully,The Loess Gully profile combination combines all different gullies in a basin.The group characteristics of the gully profiles can be detected.The proposal of gully profile combination can fill up the shortcomings of the existing gully research,so as to further deepen the understanding of the loess gully.The main research contents and structure of this paper are as follows:1.The concept of gully profile combination is proposed.The concept model of gully profile combination is defined.Based on this concept model,the extraction method of gully profile combination based on DEM is designed and implemented.Through a series of processes such as tracking and reverse tracking,the automatic extraction of gully profile combination can be effectively extracted based on DEM of a basin.On the basis of gully profile combination extraction and existing gully researches,several indicators are designed to reflect the group characteristics of the gully profile in the basin;considering that the threshold value of gully extraction will also affect the extraction of the gully profile combination,this study extracts the gully profile combination under different threshold values of gully extraction,and calculates the corresponding group indicators of the gully profile combination,discusses these group indicator values and the gully extraction threshold value The relationship between.2.On the basis of gully profile combination,two loess sample areas(Changwu and Suide)with different gully development degree are selected.Based on the DEM generated from point cloud data,the differences and unity of the two small watershed gullies are analyzed from two aspects of single level and multi-level gully profile combination.From the analysis of single level gully profile combination,it is found that there are differences in gullies within the two watersheds,and within the Changwu sample area The results of multi-level gully profile combination analysis show that although there are differences between the two sample areas at all levels,there are significant differences between level 1 and level 2 gullies and higher level gullies,and the high-level gully profile combination is more representative of the characteristics of the main gullies in the basin.3.The gully profile combination is extracted in the key loss area of the whole loess plateau,and the regional scale loess gully is studied based on the watershed.The gully gradient and the gully concavity are used as the indicators to reflect the gully shape,and the statistics are calculated as the group indicators.It is found that the distribution of population indicators has certain aggregation,and there are several high value areas and low value areas.Through the analysis,it is found that there are several high value areas and low value areas The formation of these areas is closely related to landform,river distribution and other factors.This study is an important complement to the existing research on gullies,which has a certain reference significance to explore the form,cause and distribution characteristics of loess gullies,and is also a useful exploration of digital terrain analysis method.