LARGE WOODY DEBRIS STRUCTURES IN STREAM CHANNELS
Watershed Physical Processes Research Unit
2006 Annual Report
This report serves to document research conducted under a Specific Cooperative Agreement between ARS and Oklahoma State University. Additional details of research can be found in the report for the inhouse project 6408-13000-017-00D, Integrated Assessment and Analysis of Physical Landscape Processes that Impact the Management of Agricultural Watersheds. Scientists and engineers have gained a greater appreciation of the importance of large wood in fluvial systems in recent years. Beginning in 2000, scientists at the National Sedimentation Laboratory tested 72 Large Woody Debris Structures (LWDS) in the Little Topashaw Creek, Mississippi. These man made structures have proven to be a cost-effective method for channel erosion control and habitat rehabilitation. However, after three years in operation 36 percent of the structures had failed. The loss of these structures created the need for a more durable design. Three large-scale LWDS designs were tested in the outdoor flume at the USDA-ARS Hydraulics Laboratory in Stillwater, OK, to examine failure modes and potential design improvements for these structures. The tests were focused on the forces exerted on the structures and their anchoring system, and in detailed velocity measurements around and in the structure. These measurements demonstrated the effectiveness of each design to reduce stream velocity, whereby sediment can drop out of flow and collect around the structure enhancing the stability of adjacent stream banks.