DETECÇÃO E DELIMITAÇÃO DE DEPRESSÕES CÁRSTICAS NA BACIA DO RIO SOBRADO – TO, A PARTIR DE VARIADOS MODELOS DIGITAIS DE ELEVAÇÃO

Detection and delimitation of karst depressions in the Sobrado River Watershed, Tocantins state, from various digital elevation models

Abstract

The Sobrado River watershed is mostly located in the southeast of the state of Tocantins. The largest hydrogel portion of the watershed belongs to the Bambuí Aquifer System in which the lithology is composed of carbonate rocks that provide a characteristic landscape of shallow depressions, becoming an important source of localized recharge. This study sought to detect, delimit and evaluate the potential depressions in the study area, using an association of Global Digital Elevation Models (DEM's), as well as a hybrid DEM that considered the lowest altitudes among the pixels of each DEM. To delimit the depressions, an DEM with 15 m horizontal resolution was used, coming from Sentinel-1 IW image pair interferometry. Morphometric thresholds were adopted to eliminate false depressions, associated with supervised analysis of historical images from Google Earth Pro software. A total of 299 depressions were quantified in the study area, 270 of these belonging to karst, covering an area of 803.42 ha. The use of different DEM's, including their fusion, made it possible to identify depressions that would go unnoticed when the analysis is done by only one model. The use of the DEM from Sentinel-1 images made it possible to make the delimitation smoother and closer to reality.