| Summary: | 2019 Summer. Includes bibliographical references. Much of the recent scientific literature in the field of fluvial geomorphology has documented the benefits of the presence of large wood in rivers. One of these benefits is enhanced hyporheic exchange flow (HEF). Enhanced HEF has numerous benefits and therefore plays an important role in stream health. While the science of hyporheic exchange has progressed over the past few decades, studies thus far have focused on single pieces of wood or single jams. There have not yet been studies that examine whether multiple consecutive jams have an additive or nonlinear effect on HEF. This study focuses on the impacts of increased wood loading on geomorphic complexity and HEF. We examined relations among wood load, geomorphic complexity, and HEF by studying four different reaches along Little Beaver Creek, a 3rd order tributary to the Cache la Poudre River in the Colorado Front Range within the Arapaho and Roosevelt National Forest: 1) a single channel with no logjams, 2) a single channel with limited logjams, 3) an anabranching channel with limited logjams, and 4) an anabranching channel with abundant logjams. Pearson correlations were used to analyze the relationship between HEF, wood loading, and geomorphic complexity. We found that increased wood loading increases the volume of both pools and accumulated fine sediment at the reach level. Additionally, HEF positively correlates with geomorphic complexity and wood loading. The metrics that most strongly correlated with enhanced HEF all represent factors expected to increase connectivity from the channel to the hyporheic zone. These preliminary results suggest that it is through this mechanism of increasing hyporheic zone connectivity that HEF is enhanced.
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