| The water and soil loss is serious in the Loess Plateau in China,which seriously influence and restrict the ecology?economy and the social development of the middle and lower reaches of the Yellow River.Since the founding of new China,our country attaches great importance to the management of soil and water loss on the Loess Plateau,has invested a lot of manpower,material and financial resources in.At present,the degree of water and soil loss in the Loess Plateau has decreased slightly,but the situation is still not optimistic.The sediment in the middle and lower reaches of the Yellow River originates from the erosion areas of the Loess Plateau which are composed of a series of erosion drainage basins.Therefore,the characteristics of sediment yield in the Yellow River Basin has constructed the general pattern of erosion and sediment yield in the middle and lower reaches of the Yellow River.Based on this,it is necessary to study the characteristics of sediment yield in the Yellow River Basin.Based on the digital elevation model(DEM)as the data source,based on the extraction of watershed runoff erosion evaluation node reference point by using GIS technology,combining with the fractal theory,calculation of experimental watershed erosion datum point fractal dimension,the fractal erosion benchmark index and related watershed erosion and sediment yield correlation experiment analysis,this thesis has obtained the following research results:1.The extraction of runoff node.DEM data analyze based on GIS spatial analysis technology to extract watershed runoff node.The runoff node has multiple attributes in basin,this paper analyzes the elevation attribute,spatial pattern and water flow characteristics.(1)Analysis of runoff node elevation attribute,the runoff node elevation,elevation in the maximum value at 1100-2300 m,the maximum value appeared in the Zhu Jiachuan Valley,to reaches 2240 m.at the same time,Zhu Jiachuan is the biggest watershed on runoff node height,reached 1459 m,and Gu Shanchuan Valley became the smallest height difference of runoff node,reached 455 m,which indicates the potential of erosion,According to the work of the node height to take soil and water conservation.(2)The characteristics of runoff node spatial pattern in Moran index(Moran' s I)and the nearest neighbor index(NNI)metric,Moran 's I the calculation results shows that the sample area mainly located in 0-1,close to 1,showing strong correlation between the spatial distribution of runoff.The runoff node NNI calculation shows the main position in 0-0.1,has gathered distribution.(3)Statistics shows that the flow characteristics of catchment,Ku yehe basin has more than 1 million m3,reached 10340797m3.Through the comparative analysis of statistics,this paper found that the basin catchment flow and watershed area are positively connected.2.The judgment of erosion datum point and the characteristic analysis.This paper mainly discusses and explains the process of the extraction and discrimination of the reference point of the erosion.Based on the GIS technology and the related research regional geological and geomorphological map,the erosion datum point is synthetically judged.Using the box counting dimension and spatial correlation dimension calculated fractal dimension of erosion datum point.There is a basic trend of consistent base level of two methods to calculate the fractal dimension and the correlation dimension is greater than the box dimension.Some fractal dimension of erosion datum point of the box counting and spatial correlation dimension is obviously different,which is related to fractal dimension calculation principle.Erosion datum points distribute mainly focuses on the erosion bedrock exposed areas,the relative concentration of the distribution.The quantity of erosion datum points reduced obviously compared with runoff nodes.The number of erosion datum point in left basin of middle reaches of the Yellow is more than the left basin.3.The correlation analysis between erosion datum point and soil and sediment erosion of relatively basin.It mainly related to the fractal dimension of erosion datum point,the erosion development process of basin,the erosion modulus of sediment basin and comprehensive evaluation of erosion.(1)Based on the area elevation integral,the watershed erosion development process can be transformed into childhood,young and old ages.The experimental results show that the erosion stages of maturity in the basin were dominant,San Chuanhe basin,Xin Shui Basin accounted for a large proportion.Huang Puchuan,Gu Shanchuan,Ku Yehe Basin in different stages have a certain proportion.In addition,to some part of the watershed,maturity basin has an absolute advantage,infancy proportion is greater than the old age,just as Qu Chanhe and Zhu Jiachuan Basin,old age higher than young period are Qiu Shuihe and Yan He basin.(2)The correlation research between the fractal characteristics of the erosion datum point and erosion transmission characteristics shows that the first set of experiments in 0.01 correlation level,R2 reached 0.6836,the fitting formula is: y=-11118x+22309,the second groups,R2 reached 0.6868 significant level,y=-26697 x +17448.The experiment is selected erosion datum point,and the greater fractal value shows that points distributed intensive,centralized district,however,water gathering ground smaller,so the average sediment transport modulus show(shows)smaller values.On the contrary,the average transmission area of large modulus of sediment,the fractal dimension of erosion datum point is small,the erosion datum point distribution is more dispersed,and the area of water gathering ground is larger,conform to actual situation with the average transmission modulus larger.In summary,erosion numerical reference point fractal dimension and the average sediment transport modulus coupling experimental results show that the two negative correlation,in line with the actual situation.(3)Based on two fractal dimensions of erosion datum point evaluate watershed erosion situation.Cluster analysis experiment shows that the experimental basin can be divided into four categories,based on the status of sediment erosion and the fractal dimension of river basin,defined as severe erosion area,strong erosion,moderate erosion and mild erosion area.Selected typical area on behalf of remote sensing image:severe erosion area of Ku Yehe basin,strong erosion area in Huang Fuchuan basin,moderate erosion area for Xian Chuan basin,Jia Lu basin as mild erosion area. |
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