Proposta metodológica para mapeamento da vulnerabilidade à perda de solos: estudo de caso da bacia hidrográfica do Rio Marataoan, Piauí

Abstract

The general objective of this research is to present a methodology for mapping vulnerability to soil loss, improving the proposal by Crepani et. al (2001), by replacing the “dissection index” with the parameter “shape of the slopes” (overlap of horizontal and vertical curvatures) and the “altimetric amplitude” with the HAND model - Height Above the Nearest Drainage. As specific objectives, the work aims to characterize the geoenvironmental aspects of the Marataoan River watershed (geology, geomorphology, hydrography, land use and cover, climate and soil associations); discuss the theoreticalmethodological assumptions of Crepani et.'s methodology. al (2001); test and evaluate the proposed adaptations regarding geomorphological parameters. As main results, an analysis of the vertical dissection of the study area was carried out through the application of the HAND algorithm, observing that the class that stands out in the area is the moderate one, with 40.9%, followed by the low vulnerability class, with 36.3%. Regarding the use of Vertical and Horizontal Curvatures in the analysis of water flow and its relationship with the intensity of rain erosion, the area highlighted the low and high vulnerability classes, being 51.3% and 35.5% of the total surface, respectively. It was observed that the proposed analysis model, integrating new geoenvironmental variables, characterized in a more coherent way the possible areas of material loss by linear erosion, in convergent areas with flow concentration, and by laminar erosion, in divergent areas with dispersion of flow. Therefore, the parameters used to adapt the methodology of Crepani et al. (2001) proved to be of fundamental importance in the relationship between the environment and occurring erosion processes. Thus, the present research is relevant to support the analysis of the erosive vulnerability of the Marataoan river basin, in order to guide interventions by public authorities with a view to sustainable development both in the study area studied here and in other areas to apply the same method.