Modelagem da erosão laminar na bacia hidrográfica Lagos – São João no Estado do Rio de Janeiro

Abstract

The watershed Lagos – São João (Lakes – St. John) is located in the east of the State of Rio de Janeiro, comprising 13 municipalities. In this basin was developed studies of soils and geomorphology, however studies of erosion model had not yet been developed. Thus, the aim of this study was to conduct a model sheet erosion and a diagnosis of the current state of development of erosion. For this we used geoprocessing techniques and a methodology called AHP (Analytic Hierarchy Process). This methodology was untested yet for analysis of sheet erosion. Were prepared for the watershed cartographic databases of soil, erodibility, erosivity and geomorphology. After that , there was defining values 1-5 , according influence on laminar erosion. The erosion model was developed and validated, lying on the mapping scale of 1:100,000, with five classes of susceptibility to erosion, very high, high, moderate, low and very low. The areas most susceptible to sheet erosion are located mainly in the central part of the basin, and more occasionally in the high elevation areas. The major factor for susceptibility to erosion was the use of soil. The diagnosis of erosion in the wathersed Lagos – São João, was executed by watersheds of the study area. Thus, from the fieldwork, it was created a diagnostic report of erosion, with five possible values of erosion. The value 1, was given to watersheds where erosion was practically no exist, and the value 5, was given to watersheds where the laminar erosion were extremely severe. Around the 30 % of the study area showed severe and extreme severe erosion presence, focusing upstream and north of the dam Juturnaíba. The lowlands areas that make up much of the basin obtained susceptibility and diagnosis of erosion with minimum values, due to its steepness. The fastest-growing areas of erosion were the areas with slopes of 20 % to 30 %, where the land use was pasture, showing how this use might be affecting the soils of this watershed.