This study aims at the development and evaluation of a simple approach to map profile curvature from Digital Elevation Models (DEM) with basic resources of Geographical Information Systems (GIS). This method is based on local 3x3 pixel windows and designed to perform geometrically the second order derivative through the downslope profile. Contour-based kriged DEM of six watersheds from different terrain types and with varied data specifications were used for the tests. To program universally flexible procedures, the curvature calculation required the DEM spatial resolution as one of the inputs, so as to calculate a comparable absolute value, with slope difference (in percentage ratio) per horizontal distance (100 m) as unit. The classification of slope direction in octants was used to control the overlapping derivation results calculated towards the eight neighbor pixels of each window position. The placement of boundaries with guidance of visual analysis of known slope forms assisted the establishment of arbitrary curvature thresholds for the slope profile classes (concave, convex and rectilinear).
geoprocessing; DTM/DEM; watershed; relief
