The Relation Of Quantified Characteristic Of Soil Surface Roughness And Drainage Network Of Slope Farm Land

Being as the reflection resistant characteristic value of soil surface micro-relief, Soilroughness affect the process of soil water erosion overland flow, depression storage,Infiltration, Runoff path. Because of limits of tools and computing technologies, theresearches of soil roughness mainly focus on the qualitative study of mechanism for erosionand sediment yield in soil erosion model and lack of study for quantified characteristics. Theprevious researches of overland flow generation and confluence also mainly focus on themechanism of runoff generation and confluence in small watershed, the build ofrunoff-conflux model and so on and lack of the researches of overland flow generation andconfluence in small scale. In this paper, the combination of M-DEM based on GIS and Swathprofile methodology was applied to analyze special characteristics of micro-topography underdifferent tillage practices contour tillage, artificial dig and artificial hoe. Hydrologic analysttools based on the establishments of simulation for slope stream model by GIS was applied toanalyze the drainage networks characteristic slope runoff paths, drainage density and streamfrequency under different tillage practices and obtain the quantitative and qualitative analystof slope drainage networks characteristics. Slope drainage network changes properties andthe characteristics of slope runoff paths were explored under different tillage practices; theresult will provide the scientific basis for the correct understanding of micro-reliefcharacteristic and offered the theoretical basis for the research of erosion for micro-relief ofprocess of slope erosion. The results showed as follows:(1)Rainfall had a significant effect on the micro-relief, the descending order of changesof the micro-relief under different tillage practices is artificial dig, artificial hoe and contourtillage, and the descending order of changes of the micro-relief is contour tillage, artificial digand artificial hoe after simulate rainfall. Rainfall, slope and tillage practices was inconsistentwith micro-relief, slope was unconcerned with the characteristics of special distribution ofmicro-relief. Being as the decisive factor to influence the sloping farm land relief amplitude,soil roughness significantly raised the fluctuation of slope and reduced the surface erosion.Being as the impact factor to influence the sloping farm land relief amplitude, rainfall andslope indirectly leaded to the changes of micro-terrain elevation through the runoff generation and confluence. soil roughness under different rendered the changes of micro-relief law, theearth’s gully depth and variance coefficient in elevation of micro-topography under differenttillage practices was in consist with micro-relief order.(2)With the rainfall, the trends of soil roughness under different tillage practices overallfirstly was decreased and then increased. On the same condition, with the slope increasingsoil roughness increased. The trend of changes of depression storage capacity was similarwith roughness. Roughness was found highly linear related to depression storage capacity, R2were0.9921and0.9614. The depression storage capacity of artificial dig and artificial hoepresented exponential growth with the rainfall, R2were0.899and0.909. Comparing thespecial distribution of depression under artificial dig and artificial hoe, depression depthdecreased with the slope increasing. Both of the maximum of projection and superficial areaof depression increased, the total value reduced, little slope had been less affected thedepression storage capacity.(3)Drainage density and stream frequency under different tillage practice are verydifferent under same condition of rainfall. The ascending order of drainage density andstream frequency was artificial dig, artificial hoe and contour tillage due to the characteristicsof special distribution of micro-relief. Drainage density and stream frequency increased withthe rainfall, especially for the first rainfall. But the Micro-relief slope surface complexitycharacteristics of sloping farm land under different tillage practices was inconsistent to comewith the development of rill, as a result of it the ascending order of increases of drainagedensity and stream frequency was artificial dig, artificial hoe and contour tillage during thesecond and third rainfall. Soil roughness under different tillage practices was found to behighly related to drainage density and stream frequency. In total, drainage density and streamfrequency decreased with the increases of roughness. The development of runoff path duringthe rainfall under different tillage practices changed and tended to down slope, the sloperunoff paths average sinuosity and average gradient increased, average orientation decreased.The large range of increases of sinuosity was obvious during the first rainfall, the ascendingorder of the increase of average sinuosity and average orientation was contour tillage,artificial dig and artificial hoe, the ascending order of the decrease of average gradient wasartificial hoe, artificial dig and contour tillage. The correlation of roughness and rill pathwaycharacteristics was analyzed and the result showed that soil roughness under different tillagepractices was found to be highly related to sinuosity, gradient and orientation. Sinuosity andorientation represent logarithmic function relation with roughness, gradient represent powerfunction relationship with roughness.