Evaluation of methods for delineating riparian zones in a semi-arid montane watershed

Riparian zones in semi-arid, mountainous regions provide a disproportionate amount of the available wildlife habitat and ecosystem services. Despite their importance, there is little guidance on the best way to map riparian zones for broad spatial extents (e.g., large watersheds) when detailed maps from field data or high-resolution imagery and terrain data are not available. Using well-established accuracy metrics (e.g., kappa, precision, computational complexity), we evaluated eight methods commonly used to map riparian zones. Focusing on a semi-arid, mountainous watershed, we found that the most accurate and robust method for mapping riparian zones combines data on upstream drainage area and valley topography. That method performed best regardless of stream order, and was most effective when implemented with fine resolution topographic and stream line data. Other commonly used methods to model riparian zones, such as those based on fixed-width buffers, yielded inaccurate results. We recommend that until very-high resolution (<1 m) elevation data are available at broad extents, models of riparian zones for semi-arid mountainous regions should incorporate drainage area, valley topography, and quantify uncertainty.