Study On Quantitative Index System Of Nanliu River Basin Geomorphology Based On DEM

With the development of geomorphology and digital terrain model,the quantitative study of watershed geomorphology has gradually become one of the hot spots.However,in previous studies,most of the previous studies were based on one or more geomorphological indicators,describing the geomorphology of the watershed quantitatively from one or more aspects,or evaluating and analyzing it in combination with specific problems.It is also shown that there is a strong correlation between the index and the tectonic activity,and the systematic quantitative modeling of watershed landforms is still rare.Therefore,based on the driving force-pressure-state framework,this paper constructs 29 watershed geomorphological related indexes,constructs the quantitative index system of watershed geomorphology,and systematically identifies the typical features of watershed geomorphology.It provides reference for comprehensive planning and development of landscape forest and field lake in watershed.The main contents and analysis results of this paper are as follows:(1)to construct the quantitative index system of geomorphology in river basin.In this paper,based on the driving force-pressure-State framework,29 watershed geomorphology related indexes were constructed in a multidisciplinary way,and the quantitative index system of watershed geomorphology was built.The system is divided into four layers: the target layer,the first criterion layer,the second criterion layer,and the index layer.The target layer is the typical geomorphologic characteristics of the basin,and the first criterion layer is divided into three indexes: driving force,pressure and state.The second criterion layer includes internal force under driving force,water force,third geomorphological force,natural pressure and artificial pressure under pressure,basin appearance under state,developmental state and river appearance.The index layer is the quantitative index of river basin geomorphology.The analysis method uses the absolute deviation between the index value and the base line to analyze the typical geomorphologic characteristics of the watershed.(2)Analysis of geomorphological driving force in Nanliu River basinThe analysis of steep index and concave curvature shows that the basins of Yulin Basin,Bobai Basin,Qingwan River,Rendong River,Hejiang River and Hongchao River are likely to transition to plain state.Fumian-Bobai section,Zhanghuangjiang part of the river is a relatively short and steep section;Beiliu-Fumian section,Yashan River,Bobai section,Wulijiang River,Yumajiang part of the river section,mainly by the impact of the fault zone,the extreme concave degree.The coefficient of variation on the left side of the Nanliu River main stream is slightly larger than that on the right side.The degree of fit between the fluctuation degree and the DEMheight is the highest,and the fitting coefficient is 0.84,which indicates that the fluctuation of the landform can be characterized by the fluctuation degree.The annual rainfall of Qingwan River and other basins in the upper reaches of Nanliu River is lower than other basins in the middle and lower reaches.The population distribution of Zhanghuangjiang and other watersheds with high topography is sparse,and the population distribution in the river basin,such as the less undulating degree of topography,is more denser.(3)Analysis of geomorphologic pressure in Nanliu River basinThe rainfall erosivity of the Nanliu River increases gradually from the upper to the downstream of the Nanliu River.The density of road network,tillage ratio and spatial distribution of heavy humanistic factors have the same characteristics,that is,flat plain and wide distribution of platform.In the artificial waters of Nanliu River,the area ratio of artificial waters in 16 watersheds is larger than 1.The GDP per unit area of Wuli River and other watersheds with high terrain fluctuation is lower,and the GDP per unit area of Rendong River and other basins in plain area is higher than that of other watersheds in plain area.(4)Analysis of the geomorphologic status of Nanliu River basinQingwan River,Yashan River and Bobai reach belong to symmetric basin,while others have different degree of asymmetry.There are 17 basins with shape index greater than 2 and 20 basins with narrow and long shape in Nanliu River.The ratio of the width of valley bottom to the height of bone shoulder at the main stream of Nanliu River and the seaport is higher than that of both sides of the main river.The spatial pattern distribution of Nanliu River topography humidity index is good,and the difference of each watershed is low.In the flat basin,the cutting value of the estuary is lower,and the value of cutting around the ridge and river boundary is higher.The spatial distribution of surface roughness and cutting degree is similar.Comparative analysis of the indicators of the development of Nanliu River shows that all the basins are in old age.In the Nanliu River basin,the abnormal values of the higher SL values are located near the Cenxi-Bobai fault and the Rongxian-Hepu fault zones.The rock strata flowing through the main stream of the Nanliu River are complicated and varied,and the high value of SL is not located at the inlet of the tributary.(5)typical geomorphologic characteristics of Nanliu River basinAccording to absolute deviation and index system,the typical features of each basin's landform can be described in three aspects: driving force,pressure and state.In the 20 basins of Nanliu River,there are 10 basins,such as Shasheng River,Beiliu-Fumian Section,Yamajiang River and so on,which are mainly driven by the difference of uplift rate of geomorphologic structures,the driving forces of geological internal forces such as fault zone or topographicfluctuation,which make the unit area GDP,of this part of the basin.Road network,artificial water area,arable land and so on artificial pressure is more prominent.The three basins of Qingwan River,Shatian River and Rendong River are mainly driven by the forces of running water,which makes the rainfall erosivity and tillage ratio more prominent in the basin.Lijiang,Fumian-Bobai and Zhanghuangjiang are mainly driven by the third geomorphologic force of population density,which makes the pressure of network density and GDP per unit area more prominent.