Study On Soil Erosion In Loess Hill And Gully Area On Usle Model

Wuqi County of Shannxi Province is one of the counties which suffer the most water andsoil loss in the Loess plateau in China.The county began to practice a voluntary program ofcomprehensive control and use of land in1998,The program has achieved great success inforestry ecological construction,soil and water conservation construction.This paper haschosen Wuqi county as the study region,utilized the3S technology,taken the remote sensingimages of Landsat in two periods(1986,2003) as the main information sources,together withthe rainfall data,the terrain data and the soil data to establish the equation of erosion ofsoil(USLE).Then caculated the soil erosion modulus of1986and2003. According to the soilerosion grading standards of the Ministry of Water Conservation,we reclassed the soil erosionintensity.This paper has researched the characteristics of the spatial distribution and variationof soil erosion,the relationship of the main environmental factors and soil erosion in1986and2003, in the last the study made the corresponding soil erosion control measures.Based on remote sensing imagines,material maps,rainfall and terrain data,taken USgeneral soil erosion equation USLE as the tool,with the support of ArcGIS and ERDASsoftware,main soil erosion factors were extracted and the spatial database was established.Thefactors included rainfall erosivity,soil erodibility,slope length and slope steepnessfactors,vegetation cover management factor and tillage measure factor.Based on standards for classification and gradation of soil erosion, the situation of soilerosion was evaluated,the chracteristics of variation of soil erosion was analyzed in the twoperiods of1986and2003. The results showed that the quantity of soil erosion in this regionassumed a declining trend from1986to2003,the soil erosion modulus from111.09t hm^-2 a^-1to89.79t hm^-2 a^-1.In1986the main type of soil erosion was severe grade,the proportionof slight grade was very low,with the decrease of erosion intensity the main type of soilerosion became very strong grade, the proportion of slight grade was increase. It showed thehigher intensity level erosion transform to the lower.Overlaid the map of soil erosion intensity and the main environmental factors,the paper finded the characteristics of the distribution of soil erosion in this basin vary in differentelevation, gradient, land use type and vegetation coverage. The largest intensity and amountof soil erosion mainly distributed in the elevation zone of1500^-1600m;slight erosion mainlydistributed in gentle and medium slope,extremely and severe erosion mainly distributed insteep slope,the distribution status of soil erosion intensity in the slope belt began to develop inthe direction of low soil erosion intensity from1986to2003;slight soil erosion mainlydistributed in the irrigated land,low intensity erosion occupied a dominant position inwoodland,from1986to2003with dry land area decrease and water and soil conservationmeasures improve,soil erosion intensity gradually alleviated;compared with1986thevegetation coverage has increased significantly in2003, the area of high vegetation coveragewas the advantage distribution region of slight soil ersion,accounted for above50%of totalslight erosion area in two periods.Potential soil erosion type was mainly occupied by severe erosion in1986and2003,thearea of severe erosion was large,slight soil erosin accounted for only a few.Contrasted thepotential and actual soil erosion,we could see that the status of actual soil erosion was betterthan potential soil erosion. This conclusion also proved that the vegetation factors and humanactivities played an important role on soil and water conservation work.