Wood in Streams
There is no other structural component as important to salmonid habitat, in PNW streams, as LWD. LWD provides structure to the stream ecosystem and critical habitat for salmonids (Bisson et al, 1987; Maser et al. 1988; Stouder et al., 1997). LWD performs many critical functions in forested, lowland streams. This includes maintaining the hydraulic stability of key habitat features, especially pools (Bilby and Ward, 1991). LWD also dissipates flow energy during peak flow events providing high flow refuge, protecting streambanks from erosion and thus reducing sedimentparticles of clay, silt, sand, gravel, or cobble, transported by water, are called sediment. generation (Bisson et al, 1987), helps stabilize streambeds to minimize scour, and provides cover and habitat diversity (Maser et al. 1988). (From May 2003)
Human activities, such as timber harvesting and agriculture within the riparian forests of PNW streams have an adverse impact on LWD, instream habitat quality, and juvenile salmonid diversity (Bisson et al, 1987; Maser et al. 1988; Spence et al., 1996; Stouder et al., 1997). Urbanization has similar impacts, but may be even more long lasting, especially from a hydrological standpoint. In addition to the loss of hydraulic roughness (flow energy buffer) and channel stabilizing capacity, the reduction of in channel LWD has a major effect on instream habitat complexity and diversity (May et al., 1997). With the loss of inchannel structure, there is a morphological shift away from the characteristic pool-riffle habitat to a glide dominant channel form. There is a decrease in rearing (pool) habitat both from a quantitative and qualitative perspective. Coho in small streams have a very strong preference for structurally complex cover and low flow microhabitats associated with organic debris (Stouder et al., 1997). Communities of aquatic biota in general, and salmonids in particular, depend on instream habitat complexity provided by LWD (Stouder et al., 1997). There is no question that the complexity of LWD accumulations in small lowland streams are important to salmonid populations. (From May 2003)
- Carah et al 2014 low cost wood in streams proposes that pacement of un-anchored wood in stream may cost a quarter that of anchored wood.
- A significant reason for anchoring wood is liability. Restoration proponents are afraid of being held liable for damage caused by wood intentionally placed in a stream corridor.
- Wood stability is generally estimated by comparing wood specifications to channel descriptions.
- Wood can be specified by length, diameter breast height, and presence of a root wad.
- Channels are described by their width and slope. Discharge (flow) times slope describes "stream power", and discharge is related to stream width. It seems that depth to width ratio may also affect wood transport.
- File:Dupont 1935 how dynamite streamlines streams.pdf describes the historical modification of stream channels for flood conveyance.