DEM Based Research On The Topographic Characteristics And Spatial Variation Of Fenglin And Fengcong Karst Landforms

Fenglin and Fengcong landform is one of the most typical landform in Karst.The morphology of Fenglin and Fengcong can map the unique evolution process and reflect the evolution environment of Karst.Therefore,the study on the morphologic and evolution mechanism of Fenglin and Fengcong landform has been a hot point in the current study of karst landforms.Scholars have conducted a lot of work on the extraction and analysis on Fenglin and Fengcong landform.However,since the limitation of data resolutions and analysis methods,the formal studies laid more emphasis on the qualitative description of the individual object.Therefore,with the help of GIS and the coupling of terrain-geomorphology,qualification-quantitation,microscopy-macroscopy and representation-mechanism,it becomes urgent to build a scientific characteristic system and raise analysis methods in terrain morphologic from individual-group-region scale.Based on digital elevation models(DEM)with high spatial and temporal resolution,this research for Fengling and Fengcong is aimed at quantitative description and automatic identification of their terrain morphology,proposing analytic methods for their spatial variation and exploring their developmental mechanism.The concept and connotation of Fenglin and Fengcong are analyzed systematically firstly.Based on the DEM and spatial analyze methods,the double layer topographic model and spatial relation model of Fenglin and Fengcong landform in Karst are constructed.Individual Fenglin,Fenglin chain,Fengcong,depression could be extracted automatically based on the model.It would improve the understanding of the formation and evolution mechanism of Fenglin and Fengcong landform on the basis of the analysis of individual morphological characteristics,combined morphological characteristics and spatial distribution.The main content and conclusion are showed as followed:(1)The basic concept,connotation,evolution process,characteristics,classification and expression methods of Fenglin and Fengcong are systematically expounded.Classification,which is on the basis of morphological characteristics,hydrological conditions,structural relationships,spatial scales,developmental patterns,etc.,is performed after deep analysis of Fenglin and Fengcong landform.(2)Based on the high-resolution DEM,a set of Fenglin and Fengcong extraction methods are designed,realizing the automatic extraction of topographical units such as Fenglin,Fengcong and depression in three typical karst areas(Guilin,Guangxi,Xingyi,Guizhou and Luoping,Yunnan).The methods not only solve the problem of blurring border of Fenglin,Fengcong and depression in the previous researches,but also improve the extraction effect of Fenglin,Fengcong and depression.(3)Based on the spatial relation of peaks,nadirs and saddles,a fine division method of Fenglin and Fengcong is designed to extract individual Fenglin,Fenglin chain and Fengcong.Based on the analysis results of the three study sample areas,it can be seen that Fenglin and Fengcong in Guilin area are distributed in a mixed pattern,while the Fenglin in Luoping and Xingyi area is mainly distributed outside the Fengcong area.This method solves the problem of the category cognition problem of topographic unit composed of stone peaks connected by the base,and provides an important reference for scientific research on karst Fenglin and Fengcong.(4)The quantitative evaluation indexes for morphological characteristics of Fenglin and Fengcong are proposed.The morphological characteristics of individual Fenglin,Fenglin chain;Fengcong,depression in the three study sample areas are analyzed and evaluated on the aspects of individual morphological characteristics and combination characteristics.The proposed indexes of plane features,profile features and structural features can reflect individual morphology,and the topographic roughness ratio,pitting index and Moran index,work well in quantitative description of the morphological characteristics of the Fenglin and Fengcong.Several indexes shows that significant differences exist in individual forms and combination characteristics among the three study areas.Fenglin and Fengcong in Xingyi and Luoping,are relatively similar with each other,while the Fenglin and Fengcong in Guilin are significantly different from them.(5)The spatial aggregation scale and spatial differentiation pattern of Fenglin and Fengcong in different study areas are explored.The results shows that Fenglin and Fengcong have significant regional differences.The later the development stage is,the more significant the spatial aggregation characteristics are,the larger the optimal clustering analysis scale is,and the more obvious the difference of geomorphic spatial distribution among Fenglin,Fengcong and depression area is.The integral values of Fenglin,Fengcong and depressions show that the evolution pattern of Fenglin and Fengcong are different.The Fenglin and Fengcong in Guilin develop at the same time,while the evolutionary rule from Fenglin to Fengcong exist in the evolution process of karst landform in Xingyi,Guizhou and Luoping,Yunnan.This research is also an important attempt to karst landform based on DEM data.The proposed new model and new methods of Fenglin and Fengcong are both innovation practices of digital terrain analysis and useful exploration for geomorphology.