Regional and local topography subdivision and landform mapping using SRTM-derived data: a case study in southeastern Brazil

Abstract

Topographic subdivisions and landforms are important relief characteristics that serve as a basis for several types of regional and local planning. This paper presents an assessment of the application of a global landform classification method on a regional scale using Sao Paulo State as the study area and on a local scale using the city of Sao Paulo as the study area. In addition, a new approach that includes elevation derivatives for local analysis is presented. The study hypothesizes that the automated object-based classification of topography from shuttle radar topography mission (SRTM) data method could also be used for local mapping when supported by elevation derivative data. SRTM data were used in the regional approach and post-processed elevation data derived from SRTM were used for the local analysis. The results were compared with the best available geomorphological maps and topographic surface descriptions of the region. The new method resulted in a regional-scale product in which the boundaries and features of the topography matched those in the geomorphological maps and in the literature. The method did not perform well when classifying the local topographic subdivisions of Sao Paulo, even when using the interpolated elevation data. However, the surface edges and shapes identified in the topographic maps were represented in the resulting map. To refine the results, a new approach was proposed using data derived from a digital elevation model, such as drainage densities, horizontal and vertical curvatures, and slope gradients. The use of these products in the image segmentation process and classification criteria was fundamental for obtaining the results. Theoretical thresholds were used to define the relief classes, and landform characteristics were taken into account in developing the landform map. The success of this new approach is attributed to the comprehensive database that supported the topographic subdivision analysis. In summary, this study indicates that a method developed for use on a global scale can be replicated for use on a regional scale but not on a local scale. The new approach produced reasonable results and can be used in other regions. Greater detail can be obtained using various thresholds of horizontal and vertical curvatures, for example, when delineating hazard areas. The products have potential applications in urban planning, ecological-economic zoning, urban drainage, hazard mitigation, environmental issues, erosional dynamics and transportation planning.