DEM-based Study On Orderly Evolution Mechanism Of Geomorphologic System In Small Watershed Of The Loess Plateau

With the development of geomorphology and system theory,geomorphologic system of small watershed in loess plateau has been lucubrated by many expert.Balance and evolution of geomorphology as the core of geomorphology theory have the computational basis after combining the geomorphologic entropy and dissipative structure theory.The existing geomorphology research of small watershed in loess plateau shows that if the geomorphology of small watershed is considered as a whole,the erosion evolution process of geomorphologic system in the basin is a process of decreasing geomorphologic entropy value,which means that the geomorphology development of small watershed is a process of gradual order,and indirectly indicates that one or more quantified geomorphology values in the watershed geomorphology are in an evolutionary process that tends to be ordered.But,for a small watershed geomorphology system,which system elements or system state variables within the system gradually become more orderly in the process of system evolution has not yet been effectively solved.In this paper,based on the nine-stage DEM data of geomorphology evolution obtained by artificial rainfall experiment on the loess plateau,the terrain factors are classified,and the orderly evolution process of some terrain factors and the relationship between the geomorphologic evolution stages are studied,so as to explore the evolution mechanism of the geomorphologic system in the small watershed of the loess plateau.Specific results are follows:(1)Based on different classification principles and considering the research object and scope of small watershed geomorphology system,terrain factors of small watershed geomorphology system are divided into two categories: system component elements and system state elements.(2)After the classification of terrain factors were screened,selected river network,elevation and aspect terrain factors as the research object of terrain factors orderly evolution,the research shows that:?.The rose map index of aspect factor gradually becomes symmetrical and orderly in the process of geomorphology evolution,showing an orderly evolution rule.In the early stage of geomorphology development,the dominant direction of rose map is not unique,and the distribution is scattered.In the mature period of geomorphology development,rose map index gradually began to distribute symmetrically and orderly along the dominant direction;?.The river network grade index of river network factor gradually becomes orderly in the process of geomorphology evolution,showing an orderly evolution rule.In the early stage of geomorphology development,the number of river series in river network is more,but the number of river network is gradually reduced.In the mature period of geomorphology development,the river network is stable and the grade distribution is more orderly;?.The research on the elevation band index of elevation factor shows that the elevation factor does not have the orderly evolution rule;?.Both aspect and river network topographic factors are important factors in small watershed geomorphology system.the orderly evolution process of aspect and river network factors shows that the evolution process of small watershed geomorphology system is a continuous orderly evolution process to some extent.