Cohesive Sediment Transport in Natural Streams: State of Knowledge

Fluvial geomorphologists and sedimentation engineers recognize that there are complexities involved in dealing with fine-grained material bed streams. There is also a consensus that there is no universal approach for the solution of problems of managing or "re-naturalizing" streams in a cohesive bed material environment. As a result, general practices point toward the need for in-situ data collection and site-specific assessments. To effectively carry out these tasks, it is imperative that practitioners have a thorough understanding of the different physical processes that occur within streams bounded by fine-grained sediments. Divided into three thematic sections, i.e. current knowledge of cohesive sediment transport, required research and improvements to current knowledge, and future research directions, the paper points out not only the simplifications embedded in available literature, but also issues and topics not thoroughly understood. The point is that our understanding of fluvial processes existing in cohesive bed streams is incomplete. Hence, there will always be a challenge for research scientists and stream restoration practitioners to expand and improve the current knowledge. Finally, an example of a research project related to cohesive sediment transport is included to demonstrate the point.