| Geomorphology is one of the important components of the earth's surface.Its regional differentiation controls the spatial distribution of both light and moisture,which indirectly affects the spatial distribution and evolution of the other geographical environmental factors on the surface of the earth,thus it becomes one of the hotspots in geography research.Geomorphological classification is the key to the geomorphological research.A digital morphological classification system for karst mountainous areas was constructed by combining with the basic morphological types of the country and the division scheme of karst morphological.Selecting the Qianxinan state which is the typical Karst mountainous area as the research object,based on high-resolution remote sensing images,high-precision digital elevation models,historical geomorphological maps,lithology maps and other data,combined with hierarchical analysis technology,can achieve the refined extraction of morphological information in the study area.On the basis of obtaining geomorphic information,the overall geomorphic pattern of the study area and the characteristics of different geomorphic types are analyzed in detail.And using the geomorphological type as the background data can carry out the morphological zoning of the research area.The main findings are as follows:(1)The construction of digital geomorphological systemIn the digital geomorphological classification system of karst mountain area,the lithology is used as the first-level control factor,mainly because there is a large disparity in form or cause between the karst and non-karst regional morphological in the study area.The second-level control factor is the basic geomorphological type.Mountains and plains are the starting point of geomorphological classification.Elevation is one of the most important indicators to characterize the morphological features,and it is placed in the third level.The fourth level is the genetic types,and there are few genetic types in the research area.therefore,the secondary types are directly reflected in the genetic types.The fifth level is the typical karst micro-landform,which is divided according to its individual form and combined form.The main expression of individual form is dot-like,and the surface form is mainly combined form.The sixth level mainly expresses the secondary forms of basins(depressions),terraces and mountains.The seventh and eighth level reflect the surface relief and cutting depth,the slope characteristics of the basin and mountains in the terrain control factors.The last level is the total geomorphological type,which combines the attribute characteristics of the previous eight levels into a total name,which reflects both the overall attribute and the attribute characteristics of a certain level.(2)The remote sensing interpretation of digital geomorphologyAccording to the above classification system,large-scale digital geomorphic interpretation work is carried out in the study area.In the process of interpretation,it is mainly based on the principle from simplification to difficulty and from large area to small area,to draw the maps according to the different levels.After the eight levels of topographic maps are plotted and the corresponding attributes are assigned,all of their attribute features are combined into a total topographic type,and the quality of the extracted topographic information data is checked,all the extraction of the topographic information can be studied.(3)Overall landscape distribution patternFrom the karst distribution pattern,the karst,semi-karst,and non-karst distribution areas in the southern part of the study area are relatively concentrated,and the three types of lithology are interwoven in the northern area.The hills aren't only mainly distributed in the Xingyi-Anlong area,but also in the north of Zhenfeng,northeast of Xingren,and Pu'an areas,and they account for a large proportion.In hilly areas,especially in areas where karst is distributed,the valley plains are basically not developed,which also fully confirms the characteristics that the surface rivers in the karst area are almost undeveloped.The distribution of the mountainous areas is mainly in the Ceheng and Wangmo areas in the east of the study area,and the Pu'an and Qinglong areas in the north of the study area,the distribution area is wide and accounts for a relatively large propotion.The distribution of mountains basically overlaps with the distribution of valleys and plains,which indicates that the flow of water controls the development of mountains and valleys and plains.The geomorphological distribution such as basins,depressions,and terraces is mainly in hills,and there are few distributions among mountains.(4)The statistical analysis of geomorphological featuresIn this study,a total of 2782 geomorphological map patches were extracted,with a total area of 16895.86km2,and the area and number were statistically analyzed based on different geomorphological features.The result shows that the non-karst area in the study area has the largest area of 8078.31km2;the karst area has the second largest area of 7064.90km2,accounting for 41.81% of the total area.Among the basic geomorphological types,the mountainous area is the largest,accounting for more than 60%,and the number of patches is as high as 1,307.The sum of the area of mountains and hills accounts for 93.20% of the total area,which also fully reflects the "land is not flat with three miles" of Guizhou.At the same time,it also reflects the tense human-land relationship in the study area.Typical karst terrains are dominated by peak clusters,with an area of up to 1760.30km2,accounting for 71.91% of the total area of typical karst terrains;followed by dissolving basins,accounting for 20.19%;The total area of 6 types of karst lake is 193.48km2,accounting for only 7.90%.(5)The characteristics of different basic geomorphological typesThe research results of basic geomorphological types based on karst differentiation show that the development of hills and mountains is controlled by the distribution pattern of karst,that's to say,in karst areas,hills are mainly developed,while in non-karst areas,mountains are mainly developed.Analyzing the elevation characteristics of different basic geomorphological types,the study area is dominated by low-altitude valley plains,low-medium-altitude basins,low-medium-altitude depressions,low-medium-altitude mountains,and mid-altitude hills.From the perspective of genetic type,the basin landform mainly dissolves,with the largest distribution area of the basin.Among the hilly terrains,the hills dominated by dissolution account for 77.08%;the mountainous terrains are mainly eroded and denuded mountains.There is a total of 298 geomorphological types in the study area,of which there are up to 126 mountain types,accounting for 42.28% of the total.(6)The geomorphic zoningUsing the extracted geomorphic information as background data,the study area is divided into 19 geomorphic cells according to the principle of morphology and genetic similarity.Among them,Pu'an-Qinglong-Xingren eroded large undulating and steep Zhongshan residential area has a maximum area of 3125.52km2,accounting for 18.50%;followed by the eroded middle and undulating steep and low mountain valley community in the lower Beipan River,accounting for 15.47 %;While Xingyi-Anlong eroded deep-cut low-medium elevation peak cluster depressions,Fenglin Plain area is 2190.23 km2,accounting for 12.96%. |
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