Análise integrada da paisagem para avaliação da vulnerabilidade à perda de solo das margens da Baía de Marajó, estado do Pará

Abstract

Marajó Bay is part of the Coastal Zone in the Amazon estuary, and it constitutes a form of "V" with intensive processes of erosion and progradation. The bay shores are the object of this study, from the west coast, represented by the west coast by Salvaterra and Soure municipalities, to the east coast of Mosqueiro Island. The purpose is to analyze the coastal environments adjacent to the Marajó Bay, with a systemic and integrated approach using thematic databases (geology, geomorphology, pedology, climatology and Use and Land Cover) and remote sensing images (Landsat TM 5 and MDE SRTM) to prepare maps syntheses of landscape units and vulnerability to loss of soil as a subsidy to coastal management. The main steps of this methodology are: i) atmospheric correction by dark-object subtraction, geometric correction by orthorectification, with supervised classification algorithm Spectral Angle Mapper (SAM) through training samples to map the Use and Land Cover; ii) compilation, adaptation and classification to improve data of morphology; iii) development of derivatives geomorphometric; and, iv) integration of the thematic basis for map algebra, with an overlap equation for synthesis of the landscape units maps and another equation for the preparation of the arithmetic average map of vulnerability to loss of soil. The Marajo Bay shores have mostly the unit of Fields with 17.61% of the study area (50,483.16 ha), maximum altimetry of 58 m, the topography is flat and smooth, the relief were overwhelmingly straight and planar. The integrated data indicate that the pedogenetic processes prevail in only 3.58% (10,231.38 ha) of the study area. The areas in balance between morphogenic and pedogenetic processes correspond to 3.75% (10,737.63 ha), while morphogenesis is prevalent in 42.40% (121,317.39 ha). The superiority of morphogenic units shows the hazard of coastal environments per surface mechanisms, how substrate desegregation and erosion by processes of runoff and mass displacement.