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. Improved health may be indicated by expanded habitat for diverse species (e.g. fish, aquatic insects, other wildlife) and reduced stream bank erosion.[1] 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.[2][3] Stream restoration projects can also yield increased property values in adjacent areas.[4]
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.
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Restoration techniques [edit]
Restoration activities may range from a simple removal of a disturbance which inhibits natural stream function (e.g. repairing a damaged culvert), to stabilization of stream banks, to more active intervention such as installation of stormwater management facilities, such as riparian zone restoration and constructed wetlands.[6]
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.[2][3]
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.[7] 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.[8]
In-stream techniques [edit]
Channel modification [edit]
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.[9] 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.[10]
[edit]
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.[11]
Engineered log jams [edit]
An emerging stream restoration technique is the installation of engineered log jams.[12] 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 [edit]
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 [edit]
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]
See also [edit]
- Daylighting (streams)
- Environmental restoration
- Land rehabilitation
- Retrofit (environmental management)
- Restoration ecology
- Riparian zone restoration
References [edit]
- ^ Montgomery County Department of Environmental Protection (MCDEP), Rockville, MD. "Benefits of Stream Restoration." 2010-04-13.
- ^ 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.
- ^ a b Dean, Cornelia (2008-06-24). "Follow the Silt". New York Times.
- ^ 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.
- ^ Mendocino County Resource Conservation District, Ukiah, CA (2008). "Robinson Creek Restoration Project." Project No. DWR P13-045.
- ^ Cronin, Amanda (March–April 2003). "Restoring Paradise in Moscow, Idaho". Land and Water 47 (2): 18. ISSN 0192-9453.
- ^ http://www.therrc.co.uk/rrc_nrri.php
- ^ http://www.restorerivers.eu/CasestudiesWIKI/tabid/2604/Default.aspx
- ^ Washington Department of Fish and Wildlife (WDFW); U.S. Fish and Wildlife Service, Washington Department of Ecology (2004). Stream Habitat Restoration Guidelines (Report). http://wdfw.wa.gov/publications/00043/wdfw00043.pdf. "Fluvial Geomorphology." Stream Habitat Restoration Guidelines.
- ^ WDFW et al. (2004) "Channel Modification."Stream Habitat Restoration Guidelines.
- ^ 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.
- ^ WDFW et al. (2004) "Large Wood and Log Jams." Stream Habitat Restoration Guidelines.
- ^ MCDEP. "Stream Restoration Effectiveness Monitoring." 2010-08-26.
- Brookes, Andrew (1989). Channelized Rivers: Perspectives for Environmental Management. John Wiley. ISBN 978-0-471-91979-7.
- Brookes, Andrew (1996). Shields, F. Douglas, ed. River Channel Restoration: Guiding Principles for Sustainable Projects. John Wiley. ISBN 978-0-471-96139-0.
- 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.
External links [edit]
- River Corridor and Wetland Restoration - U.S. Environmental Protection Agency
- River Restoration Centre - Cranfield University, UK
- RESTORE - restoring Europe's rivers - RESTORE is a partnership for sharing knowledge and promoting best practice on river restoration in Europe.
- River Wiki - Wiki on river restoration schemes from around Europe.
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