Topographic Data and Satellite Spectral Response in Subarctic High-Relief Terrain Analysis

Satellite images and digital evaluation models were analyzed to interpret and quantify vegetation communities and active geomorphic surfaces in a mountainous area in southwest Yukon, Canada. High levels of discrimination were determined for the digital satellite and terrain data when compared to field studies and aerial photo interpretation of basic biophysical units, specific vegetation cover types and geomorphic process categories. The agreement between field identification of a site and discriminant analysis of that site using the digital data as discriminating variables ranged from 60 to 85% and contained improvements of up to 20% when topographic data such as slope angle and incidence value or aspect were added to spectral discriminant functions. Active geomorphic surfaces were grouped successfully into process categories such as landslides, debris flows, solifluction and talus sorting. Visual interpretation of the changes in the landscape detected using Landsat Thematic Mapper imagery from 1985 and SPOT HRV MLA imagery in 1989 were attributed to (1) running water in the alluvial deposits and organic terrain, (2) different water levels in the river, delta and floodplain, and (3) a general trend of class change from wet to dry throughout the study area. This latter change may be a result of imaging the same class (e.g., alpine tundra) under more senescent (i.e., brown) conditions and may be explained with reference to a warming/drying trend in the intervening years.Key words: satellite imagery, digital elevation models, change detectionMots clés: images satellites, modèles d’élévation numériques, détection des changement