Using SONAR to Investigate Relationships Between Fluvial Wood and Channel Bedform in a Low Gradient, Coastal Plain River

Coastal Plain rivers represent sites of extraordinary ecological and biogeochemical importance for many reasons. One such reason is that large wood (LW), which serves to regulate sediment and biogeochemical processes as well as enhance geomorphic complexity, is readily transported and deposited in such systems.  However, most research on LW dynamics has taken place in low order, montane river systems and thus little is known of LW dynamics and the interactions of LW and channel morphology in higher order, coastal plain river systems. One of the challenges to understanding wood dynamics in such systems is the ability to locate and quantify subaqueous wood. This research, funded by the National Science Foundation, presents a case study of the Lumber River, an Atlantic coastal plain blackwater river located in North Carolina, USA in which we investigate wood dynamics. Specifically, we use a SONAR-based approach to mapping subaqueous wood in association with channel bedform. Using a canoe/kayak mounted SONAR unit we develop high resolution images of bed morphology and sub-aqueous wood, and report on the results of remote sensing algorithms that aim to extract wood geometry/volume, which is then assessed within the context of the bed morphology. This will help us gain a better understanding of the relationships between channel morphology and wood transport/deposition in low-gradient, high order river channels, and provide more accurate inputs to wood/carbon transport models.