Channel Classification across Arid West Landscapes in Support of OHW Delineation

Abstract : The Arid West region is dominated by watersheds that have a high frequency of intermittent and ephemeral channels. These channels are influenced by watershed characteristics and the local hydrologic regime, which dictate the amount of sediment deposited and eroded in the channel. Over time, this sediment movement causes the geometry of the channel and the surrounding floodplain to evolve. For this study, 14 mountain, 18 foothill, and 17 basin ephemeral and intermittent channels within multiple watersheds were evaluated for specific characteristics, including geology, slope, watershed design, and floodplain geomorphology. We used multivariate analyses to explore patterns of similarities and differences among the channel and watershed characteristics. Using these results and characteristics, a simple, artificial channel classification to evaluate OHW indicators was devised to better understand watershed and intermittent and ephemeral channels across the landscape in the Arid West region. A total of 18 channel types were classified: 4 in the mountains, 8 in the foothills, and 6 in the basins. Our findings demonstrate that watershed and channel characteristics vary considerably across the landscape in the Arid West, suggesting that channel classification is potentially useful for evaluating the variability of occurrence of OHW indicators at a larger scale.