Use of General Geomorphometry in the Characterization of Mountain Topography

Abstract

We characterized mountainous topography by a variety of landform measurements (geomorphometrics) taken across 10 digital elevation models (DEMs) that cover 10 7.5-minute topographic map quadrangles in Idaho and Montana. The eight metrics examined included elevation, slope, aspect, hypsometric integral, bumpiness, roughness, ruggedness, and skyward angle. Principal components analysis (PCA) indicated that roughness, skyward angle, and aspect collectively accounted for an average of 67 percent of the observed morphometric variance within each of the 10 study area quadrangles and, thus, conveyed the bulk of topographic information. Composite images made from the three principal metrics displayed map patterns closely resembling shaded relief (chiarascuro) renditions of the same terrain. The ability to numerically describe and map topographic geometry should help geographers and ecologists establish spatial correlations and other statistical relations between relief and various biophysical patterns and processes.