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Stream restoration

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Robinson Creek in Boonville, California had highly eroded stream banks prior to initiation of a stream restoration project.

Stream restoration or river restoration, sometimes called river reclamation in the UK, describes a set of activities that help improve the environmental health of a river or stream. These activities aim to restore the natural state and functioning of the river system in support of biodiversity, recreation, flood management and landscape development.[1]

Improved health may be indicated by expanded habitat for diverse species (e.g. fish, aquatic insects, other wildlife) and reduced stream bank erosion.[2] Enhancements may also include improved water quality (i.e. reduction of pollutant levels and increased dissolved oxygen levels) and achieving a self-sustaining, functional flow regime in the stream system that does not require periodic human intervention, such as dredging or construction of flood control structures.[3][4] Stream restoration projects can also yield increased property values in adjacent areas.[5]

Stream restoration differs from:

  • river engineering, a term which typically refers to alteration of a water body for a non-environmental benefit such as navigation, flood control or water supply diversion;
  • waterway restoration, a term used in the United Kingdom describing alterations to a canal or river to improve navigability and related recreational amenities.

Restoration techniques

Robinson Creek restoration project (2005) included re-shaping of stream bank slopes, addition of live willow and large rock baffles, removal of invasive species and revegetation with indigenous species.[6]

Restoration activities may range from a simple removal of a disturbance which inhibits natural stream function (e.g. repairing a damaged culvert, or removing barriers to fish such as weirs), to stabilization of stream banks, to more active intervention such as installation of stormwater management facilities, such as riparian zone restoration and constructed wetlands.[7]

Successful restoration projects begin with careful study of the stream system, including the historical weather patterns, stream hydraulics, sediment transport patterns and related conditions. Researchers evaluating restoration projects have found that many of these projects subsequently fail (e.g., with flooding or excessive erosion) because the projects were not designed with a sufficient scientific basis; restoration techniques may have been selected for aesthetic reasons.[3][4]

The River Restoration Centre, based at Cranfield University, is responsible for the National River Restoration Inventory (NRRI) which is used to document best practice in river watercourse and floodplain restoration, enhancement and management efforts in the UK.[8] Other established sources for information on river and stream restoration include the National River Restoration Science Synthesis (NRRSS) in the United States of America, and the European Centre for River Restoration (ECRR) which holds details of projects across Europe, and in conjunction with the LIFE+ RESTORE project, is developing a ‘Wiki’-based inventory of river restoration case studies which is freely available to view online.[9]

In-stream techniques

The UK River Restoration Centre publishes a M anual of River Restoration Techniques.

Channel modification

Modifications to a stream channel may be appropriate to address degradation. Channel modifications may yield improved habitat for wildlife and plants in a stream corridor, but can result in flooding, excessive erosion or other damage if not carefully planned. Design of modifications involves a careful analysis of a complex fluvial processes.[10] Alterations may include channel shape (in terms of sinuosity and meander characteristics), cross-section and channel profile (slope along the channel bed). Alterations affect the dissipation of energy through the channel, which has an impact on stream velocity and turbulence, sediment volume and size distribution, scour, and water surface elevations, among other characteristics.[11]

A cross-vane is a "U"-shaped structure of boulders or logs, built across the channel to reduce velocity and energy near the stream banks. It reduces bank erosion, maintains channel capacity and provides other benefits such as improved habitat for aquatic species. Similar structures used to dissipate stream energy include the W-Weir and J-Hook Vane.[12] The private use of similar instream structures in the United States dates to the late 19th Century, while government involvement began in the 1930s.Cite error: A <ref> tag is missing the closing </ref> (see the help page). Reintroduction of large woody debris into a stream is a fairly recent method that is being experimented with in streams such as Thornton Creek, in Seattle, WA. Because of channelization and removal of woody debris, many streams now lack the hydraulic complexity that is necessary to maintain bank stabilization and a healthy plant/animal habitat. Engineered log jams are individually designed to meet the needs of specific restoration projects, but there are overarching design elements. One element is to anchor logs along the stream bank in order to create a physical blockade against erosion. A second element of engineered log jams is to improve fish habitat. Log jams add diversity to the water flow by creating riffles, pools, and temperature variations. This is vital to fish because it provides the right circumstances to spawn, rest, feed, hunt, and hide.[citation needed]

There are inherent dangers to engineered log dams. If not properly implemented, they cause erosion and sediment in unwanted areas leading to more damage than repair.[citation needed]

Off-line techniques

As part of a stream restoration project, stormwater management facilities may be installed in the immediate corridor or in upland areas. These facilities, which reduce the velocity and/or the volume of stormwater entering the stream channel, can also improve water quality, and include:

Monitoring of restoration projects

Sponsors of restoration projects may conduct monitoring of stream conditions after construction, to evaluate effectiveness. In some projects it may take considerable time before there is evidence of desired biological activity, such as fish spawning. Therefore monitoring efforts may be conducted for several years after a restoration project has completed.[13] Practical River Restoration Appraisal Guidance for Monitoring Options (PRAGMO) is a guidance document that aims to assist all practitioners in the process of setting monitoring protocols as part of a river restoration project.[14]

See also

References

  1. ^ What is river restoration, and how to do it?http://www.restorerivers.eu/RiverRestoration/Whatisriverrestoration/tabid/2614/Default.aspx
  2. ^ Montgomery County Department of Environmental Protection (MCDEP), Rockville, MD. "Benefits of Stream Restoration." 2010-04-13.
  3. ^ a b Gilman, Joshua B.; Karl, Jarrod (2009). "Challenges of Stream Restoration as a Stormwater Management Tool; Part 1: A designer's perspective". Stormwater. 10 (3). ISSN 1531-0574. May 2009.
  4. ^ a b Dean, Cornelia (2008-06-24). "Follow the Silt". New York Times.
  5. ^ Bailey, P., and Fischenich, J.C. (2003). "Landscaping Considerations for Urban Stream Restoration.” EMRRP Technical Notes Collection. Document no. ERDC TN-EMRRP-SR-42, U.S. Army Corps of Engineers, Ecosystem Management and Restoration Research Program. Vicksburg, MS. p. 4.
  6. ^ Mendocino County Resource Conservation District, Ukiah, CA (2008). "Robinson Creek Restoration Project." Project No. DWR P13-045.
  7. ^ Cronin, Amanda (2003). "Restoring Paradise in Moscow, Idaho". Land and Water. 47 (2): 18. ISSN 0192-9453. {{cite journal}}: Unknown parameter |month= ignored (help)
  8. ^ "National River Restoration Inventory".
  9. ^ "The RESTORE River Wiki Database Of River Restoration Projects".
  10. ^ Washington Department of Fish and Wildlife (WDFW) (2004). Stream Habitat Restoration Guidelines (PDF) (Report). {{cite report}}: Unknown parameter |coauthors= ignored (|author= suggested) (help) "Fluvial Geomorphology." Stream Habitat Restoration Guidelines.
  11. ^ WDFW et al. (2004) "Channel Modification."Stream Habitat Restoration Guidelines.
  12. ^ Rosgen, David L.(2006). "The Cross-Vane, W-Weir and J-Hook Vane Structures...Their Description, Design and Application for Stream Stabilization and River Restoration." Paper delivered at American Society of Civil Engineers Conference, Reno, NV, 2001; updated 2006.
  13. ^ MCDEP. "Stream Restoration Effectiveness Monitoring." 2010-08-26.
  14. ^ Practical River Restoration Appraisal Guidance for Monitoring Options (PRAGMO) http://www.therrc.co.uk/rrc_pragmo.php
  • Brookes, Andrew (1989). Channelized Rivers: Perspectives for Environmental Management. John Wiley. ISBN 978-0-471-91979-7. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
  • Brookes, Andrew (1996). Shields, F. Douglas (ed.). River Channel Restoration: Guiding Principles for Sustainable Projects. John Wiley. ISBN 978-0-471-96139-0. {{cite book}}: Cite has empty unknown parameter: |coauthors= (help)
  • Federal Interagency Stream Restoration Working Group (United States)(2001). Stream Corridor Restoration: Principles, Processes, and Practices. GPO Item No. 0120-A; SuDocs No. A 57.6/2:EN 3/PT.653. ISBN 0-934213-59-3.
  • Rosgen, Dave (1996). Applied River Morphology. 2nd ed. (Fort Collins, CO: Wildland Hydrology, publ.) ISBN 978-0-9653289-0-6.
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