Application the geographic information system for the determination of topographic factor in a watershed

The topographical factor represents the influence of the length and steepness of the slope in the intensity of hydric erosion in the soil. The aim of this study is to test the use of the Geographic Information System (GIS) in the determination of the topographical factor (LS) of the universal equation of soil losses, USLE in the Corrego Tijuco watershed, Sao Paulo State, Brazil. The study area, which covers 8007.4 ha, has gently undulating relief and two classes of soil (Latossolo Vermelho e Argissolo Vermelho Amarelo). The work was carried out based on geographic information system for calculating the topographic factor. The results showed a predominance of areas with low to moderate values of topographic factor. Although the watershed relief is predominantly gently undulating to strong undulating, the factor (LS) exerted a major influence on erosion mainly to the amount of the watershed where the terrain has a gently relief. High values of slope length (L) and the highest values of the topographic factor were verified in downstream of the watershed.