The Study On The Influence Of Typical Forests Surface Cover To Overland Flow Resistance In Jinyun Mountain Of Chongqing

Forestry can regulate hydrological cycle,especially has huge effects on regulating surface runoff. Ground roughness coefficient is an important parameter in researching slope surface runoff.The research choose Jinyun mountain as experiment zone which is in three gorge reservoir area,Chongqing province.By investigating basic condition of test plots,I selected undergrowth litter mass of three typical indigenous standing forests(mixed wood,evergreen broadleaf forest and nan bamboo forest), moss and two kinds of herbs as study object.Building runoff plots(30×40cm)of four study objects for water releasing test.Measuring ground roughness coefficient variation of different vegetation coverage under four designed discharges to analyse resistance mechanism of surface runoff of vegetation.The results can provide foundation for eco-environment construction in three gorge reservoir area.The results shows that(1) Undergrowth litter mass layer has obviously impact on roughness coefficient n.The more amount of litter mass,the less roughness coefficient is.Mixed wood test plot has the n value between 0.0356 and0.3023;Evergreen broadleaf forest test plot has the n value between 0.0259 and0.2182;n value in nan bamboo forest is 0.0238～0.1304.When at the same discharge,the sequencing of roughness coefficient is mixed wood＞evergreen broadleaf forest＞nan bamboo forest＞bear ground.(2) When at the same discharge,the sequencing of surface runoff velocity is:bear ground＞moss layer＞nan bamboo,the sequencing of roughness coefficient n is:nan bamboo forest.＞moss layer＞bear ground.(3) In different coverage degree of herb,the flow velocity increases when the discharge improved, decreases when the coverage degree raises.However,herbaceous vegetation is less than nan bamboo which effect on the surface flow velocity.Roughness coefficient n decreases when the discharge improved,increases when the coverage degree raises.The resistance of herb to flow is more than bear ground,less than moss layer.