Spectral and geomorphometric discrimination of environmental units: application to the geomorphological processes of land degradation

The Guadalentin basin, located in SE of Spain, has a semiarid climate and presents the characteristics of Mediterranean landscape vulnerable to land degradation processes. This basin is one of the existing MEDALUS (MEditerranean Desertfication And Land USe) sites which has been chosen for continued intensive monitoring of land degradation and desertification in the Mediterranean region. This paper presents an approach to identification of its landscape units, based on the combined use of remotely sensed data and digital elevation model (DEM) variables. With the purpose of defining a set of indicators (spectral and topographic) for geomorphic processes and land degradation, the methodology adopted consists of radiometric corrections of topographically induced effects on satellite images and the extraction of the topographic derivatives in an attempt to classify the landscape units towards their susceptibility to land degradation. Thus, the Thematic Mapper (TM) images were used to discriminate different lithological units while the DEM was used to characterize landforms related to these lithological units. The combination of this information allows the authors to delineate boundaries of geomorphological and landscape units depending on their sensitivity to desertification processes.