Soil Mapping of a Small Watershed in a Brazilian Savanna Biome: A Semi-Automatic Approach

Abstract

The objective of this work is to propose a semi-automatic methodology for the creation of a semidetailed to detailed watershed’s soil map. This methodological proposal is based on the traditional method (field work and photo interpretation) and on morphometric variables analysis, using data originated from the Digital Elevation Model (DEM) of the Shuttle Radar Topography Mission (SRTM) program. The steps taken through this methodological proposal were the identification of the hydromorphic areas boundaries through interpretation of aerial orthophotographs; the compartmentalization of the relief through color composition techniques using the morphometric variabl es — slop e, altimetry and horizontal curvature; the development of a pedological database based on data gathered in the field; the elaboration of a preliminary soil map based on the compartmentalized relief and on the dataset of the soils sampled in the field; the elaboration and adjustment of the final soil map according to the interpretation of aerial photographs and also the physical and chemical analyses of the soils. This semi-automatic methodology demonstrated improved efficiency in defining the soil units, reducing operation time and subjectivity of the process, thereby contributing to the systematization of soil mapping at watershed level in scale 1:50,000, as well as, promoting better knowledge between the relation of the geomorphic and soil variables in the Brazilian Savanna Cerrado.