The Effects of Large Wood on Stream Channel Morphology on Three Low Garident Stream Reaches in the Coastal Redwood Region

Several studies have shown that large wood has a prominent role in habitat quality, however there is little research on the role of wood on pool characteristics and other habitat components in low gradient streams (channel slopes less than one percent). Longitudinal profiles are used to analyze general residual pool characteristics of three approximately 1000meter stream reaches with similar stream and watershed characteristics and vastly different large wood loadings (759 vs. 329 vs. 39 m/ha). This study devises a new classification methodology to subdivide long pools, due to different formation mechanisms and physical barriers within pools. Shallow long runs at the start or end of pools are also removed because the do not represent pool habitat. Higher large wood loading is associated with decreased individual pool lengths, maximum depths, and longitudinal residual pool areas. Greater wood loads however increase reach percent channel in pools and pool frequency. Cumulative reach longitudinal residual pool area per 100 meters and mean thalweg depths did not vary between the study reaches. Bedrock pools had greater pool lengths, maximum depths, and longitudinal residual pool areas than pools formed by large wood. Bedrock pools also had more complex bed topography than large wood pools, but had no difference in pool edge rugosity.