Uso de geoprocessamento na estimativa da perda de solo em microbacia hidrográfica do semiárido brasileiro.= Applied geoprocessing for soil loss estimation in a Brazilian semiarid watershed.

Nowadays soil loss by erosion is one of the most serious environmental problems which has caused the degradation of various resources, especially soil and water. The aim of this study was to predict the soil loss due to erosion at a small watershed sited in Semiarid region of Ceara State, Brazil, through an arrangement of Geographic Information System tools with a quantitative model of soil loss, by the Universal Soil Loss Equation, USLE. The watershed delimitation was performed using the Digital Elevation Model. The density of drainage network was estimated using the extension ArcHydro/ArcMap 9.1. The soil loss in 74% of the studied small watershed presents a value smaller than 11 t ha-1 year-1 in more plain and vegetated areas. It was observe that more than 90% of the area presented a soil loss below 37 t ha-1 year-1, being this characteristic very influenced by the local geography, which is smooth and low sloped in more than 83% of the area of the small watershed. 66% of the area presents a low vulnerability to erosion (<10 t ha-1 year-1), being associated to this region cover vegetation and low values of slope factors. The integrated use of GIS and USLE has allowed a fast and dynamic analysis of the study area, beyond identifying most vulnerable areas to the soil loss process within the basin.