Análise dos processos erosivos e as relações com as perdas aceitáveis de solos na Bacia do Alto-Paraíba/PB

Abstract

The aim of this study was to determine if the soil losses by erosion in Alto Paraíba basin soils are below the maximum tolerance determined by the Soils Department and Rural Engineering of Paraíba Federal University, campus of Areia/PB. by the Soils Department and Rural Engineering of Paraíba Federal University, campus of Areia/PB. This analysis was based on the Universal Soil Loss Equation mathematic model. Operational procedures were carried out with satellite images and GIS/SPRING. The comparative map obtained between the Losses of Soil Map and Losses of Soil Tolerance Map, was the result of a vectorial combination between these maps. About 61% of the area is under acceptable conditions of soil losses, into the expected studies developed by UFPB/AREIA, and approximated 38% with override values of non acceptable soil losses. This tolerance depends essentially of the soil characteristics, of its depth and topography, and constitutes, this way, important information that allows to the land owner or planner, to know what the best way of soil usage is, and avoiding its degradation and exploitation it with high productivity level allowing the sustainable development of the land. The values of lower erosivity occurred in minor steepest area and open vegetal cover and dense caatinga (a xeric shrubland). It was obtained through data analyses, the tax of 76% representing open and sparse vegetal cover or exposed soil and little crops, that corroborates to erosive process. The largest values of erodibility are associated to planosols. Calculating the soil losses of that basin, with the usage of Universal Soil Loss Equation by laminar erosion, it was considered the intervals for theses losses as being: null or light, to values minor than 2 t ha-1 year-1 (76,13 %); moderate soil losses among 2 and 4 t ha-1 year-1 (9,77 %); high soil losses, among 4 and 6 t ha-1 year-1 (4,79 %) and very high soil losses, over 6 t ha-1 year-1 (9,31 %).