Event Title

An Overview of Approaches to Stream Restoration Design

Presenter Information

Karen Williams

Location

Space Dynamics Laboratory

Event Website

http://water.usu.edu/

Start Date

3-26-2004 11:30 AM

End Date

3-26-2004 11:45 AM

Description

Stream and river restoration have become popular means of addressing concerns about aquatic habitat degradation and aquatic species recovery. Part of this popularity results from the immediacy of results: anyone can look at a “restored” channel created by heavy equipment and see that “something” has been changed. Reconstructed channels may differ in planform, gradient, cross-sectional shape, or bed material.

Multiple approaches can be used in restoration design. I was involved in the design of several recently completed restoration projects, and use that experience to compare and contrast the design approaches of these restoration projects. Each project had the common goal of creation of channel forms and, in some cases, channel stability. Common approaches are highly engineered, classification-based, or “jump starts”. Engineered approaches are amenable to large-scale, high risk, contract-specified projects. Classification-based and jump start approaches are amenable to wildland settings. Jump start approaches are those that construct channel forms at a coarse scale, leaving the final dimensions of the channel to be defined by the prevailing hydrologic and sediment regime.

Appropriate approaches are determined by the project setting, extent and type of disturbance, and restoration goals. Highly specified or deterministic restoration designs are at greatest risk of failure because the forms imposed are not sustained by the current discharge and sediment load carried by the channel. Similarly, the imposition of channel stability can be at odds with active channel migration which creates and sustains important riparian and aquatic habitats.

In contrast to these channel form-based approaches, a process-based approach is needed to identify and evaluate restoration alternatives that will be sustainable by ongoing watershed processes and promote measurable ecological benefits. A process-based approach discerns the evolutionary state of the channel segment (tens of kilometers) containing the project reach with respect to steady time (tens of years). The evolutionary state defines the current response of the segment to high magnitude, low frequency historical events and to the current hydrologic and sediment regime of low magnitude, high frequency events. The known evolutionary state, ongoing, upstream watershed processes and historical events can be used to predict channel form at the segment-scale. A process-based approach was proposed for a site in Milwaukee, Wisconsin, and the resulting channel design differed from a form-based design by its implementation scale (watershed rather than reach) and the coarse scale of channel forms created.

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Mar 26th, 11:30 AM Mar 26th, 11:45 AM

An Overview of Approaches to Stream Restoration Design

Space Dynamics Laboratory

Stream and river restoration have become popular means of addressing concerns about aquatic habitat degradation and aquatic species recovery. Part of this popularity results from the immediacy of results: anyone can look at a “restored” channel created by heavy equipment and see that “something” has been changed. Reconstructed channels may differ in planform, gradient, cross-sectional shape, or bed material.

Multiple approaches can be used in restoration design. I was involved in the design of several recently completed restoration projects, and use that experience to compare and contrast the design approaches of these restoration projects. Each project had the common goal of creation of channel forms and, in some cases, channel stability. Common approaches are highly engineered, classification-based, or “jump starts”. Engineered approaches are amenable to large-scale, high risk, contract-specified projects. Classification-based and jump start approaches are amenable to wildland settings. Jump start approaches are those that construct channel forms at a coarse scale, leaving the final dimensions of the channel to be defined by the prevailing hydrologic and sediment regime.

Appropriate approaches are determined by the project setting, extent and type of disturbance, and restoration goals. Highly specified or deterministic restoration designs are at greatest risk of failure because the forms imposed are not sustained by the current discharge and sediment load carried by the channel. Similarly, the imposition of channel stability can be at odds with active channel migration which creates and sustains important riparian and aquatic habitats.

In contrast to these channel form-based approaches, a process-based approach is needed to identify and evaluate restoration alternatives that will be sustainable by ongoing watershed processes and promote measurable ecological benefits. A process-based approach discerns the evolutionary state of the channel segment (tens of kilometers) containing the project reach with respect to steady time (tens of years). The evolutionary state defines the current response of the segment to high magnitude, low frequency historical events and to the current hydrologic and sediment regime of low magnitude, high frequency events. The known evolutionary state, ongoing, upstream watershed processes and historical events can be used to predict channel form at the segment-scale. A process-based approach was proposed for a site in Milwaukee, Wisconsin, and the resulting channel design differed from a form-based design by its implementation scale (watershed rather than reach) and the coarse scale of channel forms created.

https://digitalcommons.usu.edu/runoff/2004/AllAbstracts/22