Instream structures such as wood jams, living vegetation, beaver dams, certain geomorphic features and other obstacles that slow the downstream movement of water and sediment are essential to the restoration of streams. In particular, such ecologically functional dams or obstructions can accelerate the development of "stage zero" channels. The stage zero channel (sensu Cluer and Thorne 2013) is increasingly recognized as having intrinsic high value because of the multiple and synergistic ecosystem goods and services that such systems provide. Stage zero channels have well connected floodplains with elevated water tables, spatially variable hydrologic regimes and structurally complex aquatic and riparian habitat. As such, they provide incredibly valuable habitat for a suite of terrestrial and aquatic taxa, including several Pacific salmon species that are in decline. In this presentation, Dr. Pollock will provide an overview of how ecologically functional dams can be built to create zero order channels, the features and types of stage zero channels, where in the landscape they are likely to be found, and how they evolve under natural conditions. Dr. Pollock will compare the structure and function of stage zero channels to more traditional channel restoration targets. Dr. Pollock concludes that new approaches to stream restoration are needed that take into account society’s economic and ecological imperatives to create resilient, structurally complex and dynamic systems, and that the spatial scale of restorative actions should be expanded where possible to better recognize and integrate the interdependent nature of longitudinal, lateral and vertical linkages in stream systems.
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