Morphology of step-pools in a wilderness headwater stream: The importance of standardizing geomorphic measurements

The morphology of step-pools and cascades reflect the geological and climatic factors affecting channels in mountain watersheds. This study uses longitudinal and cross-section surveys to describe a headwater stream in the Boston Mountains of the Ozarks Plateau region in Arkansas and develop morphological relationships for comparisons with other regions. In the Bowers Hollow Creek watershed (3.5 km²), located within the boundaries of the Upper Buffalo Wilderness Area, step height and wavelength relationships are generally similar to those reported from other regions. Step-pool reaches were widely distributed in a discontinuous manner throughout the watershed. Average values of the sampled reaches are: reach slopes, 0.105 m/m; width, 6.10 m; crest particle sizes, 440 mm; step heights, 0.87 m; and step wavelengths, 6.62 m. The mean step steepness for the watershed was 0.13, whereas the mean length of a reach step to height ratio was 9:1. A comparison of morphological definitions found that the values of step height and steepness can vary by > 30% according to how step parameters are defined. Step height is particularly sensitive; thus, comparison of step height-based relationships from published data requires great care.