ABSTRACT
In stream restoration projects wooden debris is used to improve the ecological function; this measure obtains rising approval. Yet, uncertainty hinders many engineers to implement wooden debris. This study analyses the impact of an elevated stream spanning log on the development of underscour pools and its influence on sediment transport. In a 20 m long and 2.64 m wide flume, with a 13 m long and 10 cm high gravel bar (2 mm/8 mm) we placed a log with a 60° and 75° horizontal angle and a gap of 1 - 10 cm to the sediment. The analyses are based on photogrammetric-generated DEMs, which are processed further in ArcGIS. Additionally, the pre and post coordinates of marked sediment tracer is examined. We find that the orientation of the log influences the transport direction of the stones and that an angle towards 90° leads to stronger scourings.
