Geomorphic, Engineering, and Ecological Considerations When Using Wood in River Restoration
This chapter provides an overview of wood in rivers, focusing on wood stability in rivers and design considerations for the reintroduction of wood to larger alluvial channels.Wood debris is a common component of the particulate matter in streams and rivers and has been recognized throughout most forested portions of the globe as an important factor influencing stream geomorphology and ecology. The stability and preservation of wood in large channels is primarily a function of its embedment in the streambed. The ecological benefits of wood are evident at several scales ranging from the wood surface to the complex interstitial space of wood accumulations (logjams), to the role of wood on altering bed textures and bed forms, to the influence of wood on channel planform, particularly creating multichannel systems. A logjam can increase available surface area for invertebrates and cover for fish by more than four orders of magnitude. A logjam can split flow and increase edge habitat severalfold. Logjams create pools and bars and raise water elevations to increase floodplain connectivity and have been placed in rivers with basal shear stress values of 166 Pa. Regardless of whether wood is included in a restoration design, as long as riparian trees grow along a stream, wood will end up in the channel; hence, it is also important to understand how naturally recruited wood behaves in rivers. Reintroducing wood to rivers brings up many other issues, from flood conveyance to public safety, all of which should be considered in the design process.
Stream Restoration in Dynamic Fluvial Systems: Scientific Approaches, Analyses, and Tools
Geomorphology and Regolith and Landscape Evolution