You may order additional copies of this publication by sending your mailing information in label form through one of the following media. Please specify the publication title and number. Publishing Services Telephone ( 970) 498-1392 FAX (970) 498-1122 Abstract Valley confinement is an important landscape characteristic linked to aquatic habitat, riparian diversity, and geomorphic processes. This report describes a GIS program called the Valley Confinement Algorithm (VCA), which identifies

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... ined valleys in montane landscapes. The algorithm uses nationally available digital elevation models (DEMs) at 10-30 m resolution to generate results at subbasin scales (8 digit hydrologic unit). User-defined parameters allow results to be tailored to specific applications and landscapes. Field data were sampled to verify geomorphic characteristics of valley types identified by the program, and a detailed accuracy assessment was conducted to quantify the reliability of the algorithm output. The Python Programming Language and Python are registered trademarks of the Python Software Foundation, http://www.python.org/psf/. material, with a median channel confinement of about 2 bankfull widths. In contrast, unconfined channels were primarily low-gradient pool-riffle and plane-bed streams composed of finer substrate, with a median channel confinement of about 10 bankfull widths. We further assessed the accuracy of the algorithm by generating a stratified random sample of points equally partitioned between confined and unconfined valleys as identified by the VCA. Predicted valley types were compared with those observed from digital photos and quadrangle maps. Results showed that the algorithm could differentiate between the two valley types with 89-91% accuracy.