摘要
本文分析了坡度在坡面侵蚀中的作用，包括不同坡度下被蚀体的特征差异，坡度对坡面溅蚀、坡面入渗、坡面径流及坡面侵蚀的影响，最后从理论上阐明了坡面侵蚀中的临界坡度。
The effects of slope gradient on slope erosion was through its impacting on slope soil stability,soil depth,soil infiltration,ad slope flow velocity.Field observation shows that with the increase of slope gradient,the stability of soil on slope surface decreases.Under long time erosion of slope flow,soil grains on slope surface become coarser and the depth of soil become thinner.Thus,during raining periods,the volume of infiltration decreases and the volume of runoff increases,which was confirmed by field experiments.Experiment in the suburb of Zhangjiakou City,Hebei Province showed that both the total infiltration and the final infiltration were inversely proportional to slope gradient under 15°.When slope Is great than 15°-18°,the infiltration does not vary with slope obviously.The amount of drop splash is related to rate of drop diameter and depth of surface sheet flow and slope degree.When the depth of sheet flow is less than drop diameters,the existence of sheet flow actually enforces the splash,until the depth of sheet is equal to the drop diameter,when the splash reaches its maximum.Then,the splash reduces as the sheet depth increase.Under certain amount of precipitation,the volume of runoff increases with slope,and so does the depth of sheet flow,until the slope gradient reaches 18.3°(Foster,R.L.and Martin,G.L,1969).h,the drop splash increases with slope gradient and reaches its maximum when slope gradient is 18.3°(Palmer,R.S.,1963).Experiments(Jin C X.,1996) tested that inspite of infiltration does not increase with slope when gradient is greater than 15°-18°,the amount of erosion increases greatly.The only reasonable explanation for the phenomena is the increase of flow speed with gradient.The flow velocity can be expressed as:In which,V represents flow velocity.h and k represent sheet depth and the grain diameter which is equal to or larger than 84% of grain particles,s represents slope gradient and a and b are parameters.The erosivity of slope flow is proportional to flow energy. When the energy of flow reaches its maximum,the erosivity of flow also reaches its maximum. the flow energy can be expressed as:In which,Ev represents flow energy,q represents unit width flow.and β represents slope angle.s=sinβ.ρ represents water density.From the above equation,it can be seen that when Ev reaches its maximum,i.e.when β=24.1°-29°.The conclusion is that when slope is between 24°and 29°.slope erosion reaches its maximum.
出处
《地理研究》
CSSCI
CSCD
北大核心
1996年第3期57-63,共7页
Geographical Research
基金
国家自然科学基金
