GEOMORPHIC MAPPING USING DIGITAL TERRAIN ALGORITHMS ALONG THE SEMI-ARID RÍO SALADO WATERSHED, NEW MEXICO

Recent advances in digital terrain modeling and geographic information systems (GIS) have facilitated the analysis of geomorphic and hydrologic features within complex landscapes. Computer-based algorithms utilizing digital representation of topography may accurately extract landform features, including the delineation of major geological units and their internal variability. In this study we use two terrain analysis algorithms and digital elevation models (at 10-m and 30-m), coupled with field observations, to aid in feature extraction along the semi-arid Río Salado watershed in central New Mexico. We selected several regions where features, such as active channels, floodplains, valley bottoms, and dissected strath terraces, can be identified with field observations. Two GIS algorithms were utilized in the investigation for identifying valley bottoms (Gallant and Dowling, 2003) and delineating floodplains (Williams et al. 2000). Initial results for the basin demonstrate the algorithms correctly identify lower regions at various elevations, such as active channel deposits, as valley bottoms; while relatively flat, but higher, older terrace surfaces are mapped as ridge top features. Higher-order channels and fault-induced alluvial deposits are also correctly identified as valley bottoms. However, young, first order drainages are too small relative to the topographic resolution to accurately extract geomorphic features. Our results indicate that terrain algorithms can be used as a tool for improving the quality of mapped geomorphic, hydrologic, and soil-landscape features in semi-arid watersheds.