GEOMORPHIC IMPACTS OF HURRICANE HELENE ON THE WEST BRANCH ROCKY RIVER IN THE NORTH CAROLINA PIEDMONT

Catastrophic floods capable of creating geomorphic change are increasingly common and can produce flashy discharge in first order streams. Streams in the Piedmont of North Carolina are incised into deep channels as a result of anthropogenic impacts on the landscape and the impact of floods on these streams are not well understood. Using image comparison analysis and replicable geomorphic mapping, we studied gravel bar and debris dam migration to analyze the geomorphic impacts of high flow events in small headwater streams. Specifically, we completed high resolution geomorphic mapping of channel bottoms before and after Hurricane Helene. We found that mid-channel gravel bars tended to join with the bank or with point bars along the bank. Additionally, we found that debris dams have a cohesive nature that leads them to wash out all in one piece as opposed to pieces at a time. Debris from these dams can then form as the basis for new dams downstream. While channelized Piedmont streams may appear static, we conclude that they are geomorphically dynamic allowing for similarly dynamic and diverse habitats within the stream. These dynamic habitats have a critical role in the shape of the channel, flood dynamics, and aquatic insect populations.