Mapeamento geomorfolÃgico e de processos erosivos da bacia hidrogrÃfica do rio Botafogo â PE utilizando tÃcnicas de geoprocessamento




This work presents the result of geomorphological and sedimentlogical studies and also erosion processes at the Botafogo Watershade, located 40 km north of Recife, Pernambuco State, Northeastern Brazil. In order to treat and analyse cartographic charts and remote sensing products , geoprocessing techniques were used. The data were validated and taken together with fieldworks. The final product of this research is a geomorphologic map with the erosive processes of the Botafogo Watershade, at the scale of 1:50.0000. This map was the result of the creation of a digital terrain model and photographie and satellite image interpretation. Eight geomorphological units were defined, gathered in degradation and accumulation models: Crystalline rock hills (2,6 Km2 = 1% of the Botafogo Watershade area); Slope (165,9 Km2 = 63%); Tableland overlying the Infra-Barreiras Unit (45,0 Km2 = 17%); Tableland overlying sediments of Barreiras Formation (11,8 Km2 = 4%); Bottom plain Valleys (23,2 Km2 = 9%); Incised valley (2,9 Km2 = 1% ); Fluvial plains (10,5 Km2 = 4%); Tidal plains (3,6 Km2 = 1%). Furthermore, active erosive processes were identified and located. In order to characterize the Infra-Barreiras Unit a more detailed study was taken. This concerned stratrigraphic profiles, which include chemical and sediments analysis. According to these results, it was observed that the granulometric fractions, silt-clay and medium sand are the parameters which lead to the Infra-Barreiras Unit differentiation. Applying this result as an argument for distinction of the analysed samples, it is proposed here that the mathematical ratio between the fractions silt-clay and medium sand results in the value that distinguishes both geological units. So, when the reason silt-clay/medium sand is larger than 1, it indicates typical sediment from the Infra-Barreiras Unit. Numbers inferior than 1 characterize sediments collected from Barreiras Formation. The Erosion Potential map showed three vulnerability potential classes to Botafogo Watershade: High â 11,8 Km2 , corresponding to 5% of the study area; Medium â 154,5 Km2 (= 60%); and Low â 90,5 Km2 (=35%)


processos erosivos bacia hidrogrÃfica do botafogo erosion processes geoprocessing geociencias botafogo watershade geomorphological mapping mapeamento geomorfolÃgico geoprocessamento

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