Geomorphometric mapping of Zagros Ranges at regional scale

A method for regional-scale geomorphometric mapping that is useful for morp hotectonic studies is presented for the Zagros Ranges in Iran. The DEM-to-M ount transformation, a region-growing algorithm for terrain segmentation is implemented. To cope with the specific conditions in that compressional-mo rphotectonic context, the transformation was modified: region growing was n ot allowed for valley pixels: ridge pixels were used as seeds; and the grow ing criterion was based on gradient. The landscape was decomposed to two te rrain classes (mount and non-mount) and to isolated mountain objects that w ere numerically represented on the basis of appropriate attributes (mean an d maximum elevation. gradient, hypsometric integral, size). The domain of t he attributes was sliced to intervals on the basis of geomorphometric crite ria and their spatial occurrence. Finally, the landscape was characterized on the basis of mountain morphometry From the spatial distribution of the c lasses. The objects greatest in size were observed in the NW. Three distinc t regions with respect to the mean elevation were spatially distributed in increasing mean elevation from SE to NW, producing stair-step topography at a regional scale. In the NW, the degree of dissection was less and objects with the highest gradient were observed. These observations suggest that a t a regional scale the main NW topographic units have not been significantl y downcut towards sea level, for a pattern of small isolated objects with l ower mean elevation, gradient and hypsometric integral to be formed as thos e observed in the SE. (C) 2001 Elsevier Science Lid. All rights reserved.