Research On The Extraction And Fractal Of River Network And Water System Information Based On RS And GIS

The Longchuan River Basin in Yunnan Province,a complex lithology,dry clear,rainfall concentrated,domestic water distribution is extremely uneven,often encounter rainstorm floods,landslides,landslides and other g eological disasters,a region as Yunnan Province geological disaster prone,the Longchuan river basin hydrological and topographical features of research is particularly important.With the development of GIS(Geographic Information System),the use of DEM(Digital Elevation Model)for hydrological analysis has become a hot trend in the study of river network characteristics.In this paper,we use remote sensing technology to determine the drainage area threshold in combination with regional geological condi tions comparison to extract the river network in Longchuan River basin.The fractal theory and Horton's law are applied to study the fractal characteristics of river network in the study area.A variety of terrain factors on extracting topographic features of watershed,and the combination of vegetation index and rainfall analysis of the groundwater storage basin,and classification of sub basin,a comprehensive analysis of the topography and drainage characteristics of the basin,for soil and water conserv ation in the study area,provides data support for the ecological environment.The remote sensing images used in this study are: the images of the images of the Landsat8-OLI,the ASTER GDEM and the Sentinel-2A image.Based on the analysis of the geological structure,the rock formation and other information of the study,a mathematical method for the determination of the drainage area threshold is designed based on the analysis and research of the water system of the river network,which can be used to extract the river network water system of the river basin.Combined with the results of extraction were verified on the basis of Sentinel-2A image,divided into several sub basin and river basin classification of sub basin;at the same time extraction by using DEM data such as elevation,slope,terrain factor fluctuation;by using Landsat-8 OLI image to extract the vegetation index,with rainfall and topography making the thematic layers,eventually modeling theme groundwater potential zone layer.The main research contents and achievements of the thesis are as follows:1.On the basis of the former judgment on the drainage area threshold to extract the river network,a mathematical method of tangent a straight line to the fitting curve of the drainage area threshold and the density of the river network is made,and the threshold corresponding to the tangent point is taken as the optimal watershed water catchment area threshold.Eventually extracted river network system.At the same time,the subbasin was classified,and the flood disaster was mainly scattered in the middle,south and southeast of the study area.2.The river network was classified into five grades,and the average branching ratio was 4.37 based on Horton's law,which indicated that the tectonic a ctivity in the study area was relatively strong.Based on the fractal theorem,the comprehensive fractal dimension of the watershed is 1.2194,which is calculated by the box dimension method,and it is determined that the whole watershed geomorphology in t he study area is in the infancy stage of erosion and development.The traditional box dimension method is improved to study the hydrological characteristics of large-scale river basins.Several square grids are used to cover the study area,and the fractal dimensions of river networks under each square grid are calculated.Fractal characteristics of Water system in the study area on a small scale.It is found that the high value area of fractal dimension of river system is as long as it extends to the belt as NE and NS.3.Based on the extracted elevation,slope,topographic fluctuation,surface cutting depth,topographic factors.In the study of elevation distribution space,it is found that the geomorphologic types of the study area are mainly sub-middle mountains landform and middle mountains landform.In the spatial study of slope distribution,more than half of the watershed areas are represented as slopes and steep slopes,and the topographic slope spectrum is made,and the area of each slope range is studie d in detail.In the study of the spatial distribution of topographic undulation,it is found that the small undulating surface accounts for about 70% of the main body.According to the research on the surface cutting depth,it is found that the cutting degre e of the whole watershed is large,the maximum cutting depth is 617 m,and the main cutting depth is in the range of 5 ~ 20 m.4.Combined with Landsat-8 OLI,DEM data and regional rainfall data,the 6 types of thematic layers,such as drainage density,el evation,slope,aspect,vegetation cover and rainfall,are made.According to the weight of groundwater storage capacity,the model is established to generate the thematic map of groundwater potential area.That is easy to storage of groundwater in the stud y area in the NE-SW region to the distribution of groundwater potential is very good mainly in the southwest part of the basin and the middle Yao'an,Mouding dam,then good groundwater potential distribution in the west of Yuanmou.