Loess Valley System Automatic Classification And Geological Hazard Effects

The automatic classification of the loess valley system has important scientific and practical significance for the history of the evolution of sedimentary erosion on the Loess Plateau,the development regularity and the occurrence mechanism of geological disasters.The study took the loess valley landform of the sheets of Ji Xian County as the research object,and carried out the research of loess valley system division and characteristics.The main achievements were as follows.(1)The surface water movement model was established based on the rainfall runoff model and the Strahler Channel Classification Principle.The study simulated the dynamic movement process of the actual water flow on the 1:50000 DEM grid data surface and realized the automatic classification of the loess valley system in the sheets of Ji Xian County.The cumulative threshold(X=10)of the best convergence accuracy of the channel classification and valley extraction was determined,which was consistent with the actual survey valley type.(2)On the basis of the valley characteristics research from the aspects of vally morphology,distribution patterns and geometric characteristics combined with literature survey and field investigation,the study summarized the features and developmental mechanism of V-shaped,sharp U-shaped and U-shaped valley section of slope erosion valley,alluvial valley,dry valley and river valley,and discussed the dynamic evolution regularity of different parts of the valley(valley head-slope surface-valley bottom)on the multistage forming stage and associated relations of the development of different geomorphic units and valleys in the loess plateau.(3)Based on the theory of basin erosion dynamics,the study discussed the evolution mechanism of the valley system and the erosion process and stability of the valleys at different times and in different locations,and revealed the erosion transport process and model of channel flow on the valley slope and the valley ground.Meanwhile,the physical and mechanical generalization model of the valley system development process and the simplified model for stability calculation were proposed,and the complete evolution process of the valley system was constructed.(4)The types of geological disasters at different levels of valley development are different based on the geological disasters effects study of the valley system development of Ji Xian County sheets.The slope erosion trenches are dominated by slope mudslides and small slumps.Geological disasters(collapsing flow)occur frequently at the alluvial valleys intersectionsd,characterized by clustering;Small and medium-sized landslides are prone to occur at dry valleys,while the river valleys are in a relatively stable period with less geological disasters.