The Effects Of Vegetation Index On Watershed Sediment Yield Based On Remote And Rusle

Vegetation of soil erosion research was given priority to with slope runoff plots, and the reserch of vegetation at catchment scale using semi-quantitative analysis, rarely considered the the vegetation growing season and precipitation change at study area, rarely combined with landform background, the study lack of actual inspection, the study results lack of actual inspection.Combined with existing relatively analysis methods and model structures in hydrology and soil erosion subject at home and abroad, Study the seasonal variation of vegetation of different land use and basic law of sediment yield. Thus study the relationship between space-time distribution at watershed sediment and the changes of vegetation, to clear relationship between watershed sediment and seasonal variation of vegetation, to provide reliable data support of the soil erosion risk assessment or evaluation, and to provide theoretical basis for comprehensive planning and management of small watershed.On the basis datas of control station at hubei GuChengXian small watershed (The area is5.38km2)1987to1987, based on rainfall energy, soil erodibility, topographic factor in RUSLE and vegetation index(NDVI、 EVI、 Greenness fromTasseled cap transform,MSAVI) extracted from remote sensing image of Landsat5—TM, vegetation index transformed into a vegetation factors reflect the watershed sediment, role with RUSLE vegetation cover and management factor C at the same meaning; analysis the seasonal change of converted factor, explore the influence degree and the contribution of vegetation in different land use on the watershed sediment. This paper’s main conclusions and results are shown below:Conversion formula1and conversion formula2is priority, calculating the combined factor from vegetation index of NDVI and MSAVI are the priority in the perspective of conversion formula and combined factors of watershed average vegetation indexrReflect the watershed sediment,can be used to reflect the watershed vegetation overall level; according to the conversion formula2when calculating the combined factor with EVI index, according to the conversion formula1when calculating the combined factor with Greenness fromTasseled cap transform. VI—NDVI、 EVI、Greenness、 MSAVI; α、β—Initial parameters conversion formula Combined factors from vegetation index conservated by conversion formula1and conversion formula2are effective factors which can express seasonal variation of vegetation growth and small watershed sediment in the perspective of the relationship between changes of vegetation and small watershed sediment at different land use types, combined factors from NDVI at dry land and arboreal lands can explain more than50%of sediment modulus seasonal changes, combined factors from MSAVI at dry land and arboreal lands can explain more than40%of sediment modulus seasonal changes.Rainfall erosivity factor has contributed88.19%of watershed sediment, the contribution of vegetation and other factors on watershed sediment was only11.81%, combined factor of overall watershed has contributed of6.48%, under the premise of basically remain unchanged in the watershed underlying surface. With the R10increase of every unit standard deviation will promote watershed sediment modulus increased by3.44t/km, with the combined factor increase of every unit standard deviation will promote watershed sediment modulus increased by0.94t/km2, the impact strength on watershed sediment modulus of Rio is3.75times of Combined factor. In a word, the effect of vegetation on the influence of the sediment is far less than Rio.With the Combined factor of shrub land, arbor forest land, paddy field, dry land increase of every unit standard deviation will promote watershed sediment modulus increased by0.60t/km2,0.79t/km2,0.60t/km2,0.98t/km2, respectively.The impact of the dry land on watershed sediment is the largest, followed by arbor forest land, shrub land and paddy field is minimal.Due to Rio as external dynamic conditions of erosion and sediment yield, the different land use types as the source of the sediment in small watershed, viewed from the sediment source point, the contribution of shrub land, arbor forest land, paddy field, dry land for the watershed sediment accounting for19.08%、27.71%、17.00%、36.20%,respectively. Dry land and forest land had the greatest influence of watershed sediment, as a result of the protection of soil and water conservation function of the forest, in the dry land and arbor forest land located on the same hydrological response unit work together lead to the’ influences of arbor forest land to watershed sediment is second only to the dry land.