Erosion Susceptibility in the Macumiri River Watershed (Amazonas, Brazil) Based on Multicriteria Analysis and Map Algebra in a GIS Environment

Abstract

Soil erosion is a major environmental degradation process in tropical watersheds, strongly influenced by natural factors and land use dynamics. In this context, the present study aimed to identify areas susceptible to laminar erosion in the Macumiri Stream basin, located in Amazonas State – Brazil, through spatial modeling using a Geographic Information System. The methodology was structured in two main stages: environmental diagnosis of the watershed and application of a multicriteria decision analysis integrating soil properties, slope, and land use/land cover variables. Data processing was conducted in QGIS using map algebra and geoprocessing techniques, with weighted criteria assigned according to their relative influence on erosion processes. The results revealed a predominance of moderate erosion susceptibility, mainly associated with intermediate slope gradients and forested areas, while high-susceptibility zones were spatially limited and linked to specific natural conditions such as sandy soils and steeper terrain. The analysis highlighted the critical role of vegetation cover in mitigating soil loss, even in inherently fragile environments. It is concluded that the integration of multicriteria analysis and map algebra within a GIS framework is an effective approach for identifying erosion-prone areas, providing robust technical support for environmental planning and sustainable watershed management in Amazonian regions.