Sloping Land Surface Roughness And Its Role In Research

Surface roughness of slope farmland is resulted in the action of artificial management and soil erosion.lt is undulated,concave and convex on the surface,and has great effect on overland runoff and erosion process.As research objects for slope farmland of Ansai county and Chunhua county in Loess Plateau,features and effect factors of roughness and its effect on runoff and erosion were studied by using the principles and methods of soil science,eroded science and hydraulics on the base of the experiments about indoor and field artificial rainfall.It's process and evolution theory were analysed.The description model of surface roughness was established by fractal theory. It would serve on ecological environment construction about soil erosion prediction and reclaiming forestry (grass)from farmland.l.The definition of surface roughness on slope farmland in Loess areas was put forward by the analysis of roughness features,that was,it was a condion about concave and convex surface due to effects on soil clod and aggregate size,crop planting and artificial management or raindrop impact,runoff scouring or the others on the slope farmland to some soil.The methods of determination and calculation about surface roughness was put forward in Loess areas, and the ranges to surface roughness was from 0.109 to 28.003 in theory by combating with the quantitative features of surface roughness.2.The effect factors of surface roughness were as following.(l)Artificial cultivation management. Surface roughness had an increasing trend with the increasing management intensity obviously. (2)Rainfall. The variation of roughness increased to random roughness and decreased to oriented roughness on the condition of rainfall. The variation was stable during the light rainfall density and the variation was obvious when rainfall density was over 0.99mm/min.There had the same law on the condition of different slope degree and the same rainfall density. The variation of random roughness and oriented roughness was different with the increasing combinatihg factor of rainfall(PI).Random roughness increased, while oriented roughness decreased in an exponent function gradually. (3 )Rainfall and runoff. The variation of random roughness had an increasing trend and the variation of oriented roughness had a drcreasing trend by the increasing runoff per meter, and the effect increased with the increasing runoff. The variation of surface roughness to many factors of effecting roughness was analysed through many experiments of indoor and field rainfall .The results were that the variation of random roughness had a negative relationship with soil early stage water content and soil bulk density and a positive relationship with slope degree, artificial management, rainfall composite factors and runoff per meter,and the variation of oriented roughness had a negative relationship with the early stage water content, soil bulk density, rainfall composite factors and runoff per meter and a positive relationship with slope degree and artificial management.3.Random roughness had an increasing trend and decreasing trend with the increasing rainfall density during the course of rainfall. The above variation increased with the increasing rainfall density. The variation of surface was divided into three stages from the angle of erosion evolution, that were the sealing process, the mutual process of concave and convex, the ocess of abrupt variation.4.Surface roughness had great effect on erosion and runoff.(l)Surface roughness had the effect on retarding the runoff time. There had an increasing trend with the increasing slope degree.(2)On the condition of the same rainfall density, the runoff had a decreasing trend with increasing roughness.The runoff amounts increased with the increasing rainfall density and slope degree, and overland runoff had the law varying from the increasing, decreasing to a stable condition. The runoff increased by the increasing rainfall density obviously when the rainfall density was over 1.08mm/min on the condition of the same slo...