Regional Impact Of Human Activities On Soil And Water Losses

Human activity is the most active factor that influences the environment widely andpersistently, and it changes the intension and process of soil and water losses. The impact ofhuman activities on soil and water losses can get further information on the degree anddirection of impact, the mechanism of how to adjust the flow and sediment, and the protectionand evaluation of construction environmental problems. The result of research is important onthe planning of soil and water conservation, the measurement of watershed and channel, anddecreasing of flood, and other relative issues. In the paper, the characters of impact of human activities are discussed, and a set ofdatabase is founded. Based on the survey on soil loss and the database, some regionalparameters, a set of evaluation indicators, and some models are put forward for evaluation ofseveral typical activities. The main results are showed as follows. 1. Based on the analysis of character of human activities, the mechanism and ways ofhuman impact on soil and water losses are discussed. The impact is so complex that it hasmany kinds, different directions and stages. It influences the process, forces, soil prosperitiesand other factors. 2. Based on the slope composition of land form in North area of Shanxi, and sandycoarse region in the middle reaches of Yellow River, a regional soil loss landform factor isformed. It can not only describe the regional landform character, but be used to evaluate soilloss with coverage of vegetation. The construction of damland and terrace can reduce the soilloss because it can reduce the erosion energy even it can enlarge the area of land surface. Thedamland and terrace can reduce 100 percentages, and more than 75 percentages of energy thatinduce soil loss in the same area respectively. In the sandy coarse region, the erosion energycan reduce 2.4 and 12.6 percentage by damland and terrace construction respectively, and thatcan reduce sediment more than 1.24 hundred million annually. 3 An indicator system is set up for soil erosion evaluation of highway construction.Based on the soil loss survey on site, general survey data of highway in 2000, the geologicalmap, land use and land cover data in North Area of Shanxi, the impact of road construction onsoil loss is evaluated. The disturbance of land surface during the high way construction is so intensive that thesoil loss is severe. In hilly and gully area, and soil loss modules during construction periodvaries form 280 to 375 thousand tons each square kilometer annually, and soil loss modules ofloess road amount to 42.4 thousand tons each square kilometer annually. 4 Based on the branches in Hekou and Longmen Region, and Wei River including of itsbranches, a data base is set up includes many items, such as the area of each soil and watercontrol practices, the volume and weight of flow and sediment detained by each practices, theprecipitation, flow and sediment, and the sediment particle in Yanhe River. Compared with characters before 1969, the flood modules induce by efficientprecipitation, the sediment delivery modules with flood induced by efficient precipitation, andsediment delivery modules decreased when the conservation practices increased in eachbranch in Hekou-Longmen Section of Yellow River. The particle of sediment turned finerwith the increasing of soil conservation practices in Yanhe River. Focused on the water problems in Yellow River Basin, A factor of "flow cost of sedimentcontrol" is put forward to evaluate how much flow reduced when the same weight ofsediment detained. The factor can discover the different effect on sediment and flow amongdifferent practices and different branches. The flow cost of sediment control of damland is smaller than that of terrace,re-vegetation, and grass-planting. The difference of flow cost of sediment control betweendifferent branches is clearly. The flow cost of sediment control practices decrease...