Stream restoration
Encyclopedia
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. 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. Stream restoration projects can also yield increased property values in adjacent areas.
Stream restoration differs from:
), to stabilization of stream banks, to more active intervention such as installation of stormwater
management facilities, such as riparian zone restoration
and constructed wetland
s.
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.
processes. 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.
s 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.
s. 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 jam
s 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.
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.
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:
, therefore monitoring efforts may be conducted for several years after a restoration project has completed.
River
A river is a natural watercourse, usually freshwater, flowing towards an ocean, a lake, a sea, or another river. In a few cases, a river simply flows into the ground or dries up completely before reaching another body of water. Small rivers may also be called by several other names, including...
or stream
Stream
A stream is a body of water with a current, confined within a bed and stream banks. Depending on its locale or certain characteristics, a stream may be referred to as a branch, brook, beck, burn, creek, "crick", gill , kill, lick, rill, river, syke, bayou, rivulet, streamage, wash, run or...
. Improved health may be indicated by expanded habitat
Habitat
* Habitat , a place where a species lives and grows*Human habitat, a place where humans live, work or play** Space habitat, a space station intended as a permanent settlement...
for diverse species (e.g. fish, aquatic insects, other wildlife) and reduced stream bank erosion. Enhancements may also include improved water quality
Water quality
Water quality is the physical, chemical and biological characteristics of water. It is a measure of the condition of water relative to the requirements of one or more biotic species and or to any human need or purpose. It is most frequently used by reference to a set of standards against which...
(i.e. reduction of pollutant
Water pollution
Water pollution is the contamination of water bodies . Water pollution occurs when pollutants are discharged directly or indirectly into water bodies without adequate treatment to remove harmful compounds....
levels and increased dissolved oxygen levels) and achieving a self-sustaining, functional flow
Streamflow
Streamflow, or channel runoff, is the flow of water in streams, rivers, and other channels, and is a major element of the water cycle. It is one component of the runoff of water from the land to waterbodies, the other component being surface runoff...
regime in the stream system that does not require periodic human intervention, such as dredging or construction of flood
Flood
A flood is an overflow of an expanse of water that submerges land. The EU Floods directive defines a flood as a temporary covering by water of land not normally covered by water...
control structures. Stream restoration projects can also yield increased property values in adjacent areas.
Stream restoration differs from:
- river engineeringRiver engineeringRiver engineering is the process of planned human intervention in the course, characteristics or flow of a river with the intention of producing some defined benefit. People have intervened in the natural course and behaviour of rivers since before recorded history - to manage the water resources,...
, 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 restorationWaterway restorationWaterway restoration is the activity of restoring a canal or river, including special features such as warehouse buildings, locks, boat lifts, and boats. In the United Kingdom, Canada and the United States, the focus of waterway restoration is on improving navigability, while in Australia the term...
, a term used in the United KingdomUnited KingdomThe United Kingdom of Great Britain and Northern IrelandIn the United Kingdom and Dependencies, other languages have been officially recognised as legitimate autochthonous languages under the European Charter for Regional or Minority Languages...
describing alterations to a canal or river to improve navigability and related recreational amenities.
Restoration techniques
Restoration activities may range from a simple removal of a disturbance which inhibits natural stream function (e.g. repairing a damaged culvertCulvert
A culvert is a device used to channel water. It may be used to allow water to pass underneath a road, railway, or embankment. Culverts can be made of many different materials; steel, polyvinyl chloride and concrete are the most common...
), to stabilization of stream banks, to more active intervention such as installation of stormwater
Stormwater
Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...
management facilities, such as riparian zone restoration
Riparian zone restoration
Riparian zone restoration is the ecological restoration of riparian zone habitats of streams, rivers, springs, lakes, floodplains, and other hydrologic ecologies.Riparian zones have been degraded throughout much of the world...
and constructed wetland
Constructed wetland
A constructed wetland or wetpark is an artificial wetland, marsh or swamp created as a new or restored habitat for native and migratory wildlife, for anthropogenic discharge such as wastewater, stormwater runoff, or sewage treatment, for land reclamation after mining, refineries, or other...
s.
Successful restoration projects begin with careful study of the stream system, including the historical weather patterns, stream hydraulics
Hydraulic engineering
This article is about civil engineering. For the mechanical engineering discipline see Hydraulic machineryHydraulic engineering as a sub-discipline of civil engineering is concerned with the flow and conveyance of fluids, principally water and sewage. One feature of these systems is the extensive...
, sediment transport
Sediment transport
Sediment transport is the movement of solid particles , typically due to a combination of the force of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained...
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.
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 fluvialFluvial
Fluvial is used in geography and Earth science to refer to the processes associated with rivers and streams and the deposits and landforms created by them...
processes. Alterations may include channel shape (in terms of sinuosity
Sinuosity
Sinuosity or sinuosity index is a measure of deviation of a path between two points from the shortest possible path...
and meander
Meander
A meander in general is a bend in a sinuous watercourse. A meander is formed when the moving water in a stream erodes the outer banks and widens its valley. A stream of any volume may assume a meandering course, alternately eroding sediments from the outside of a bend and depositing them on the...
characteristics), cross-section and channel profile (slope along the channel bed). Alterations affect the dissipation
Dissipation
In physics, dissipation embodies the concept of a dynamical system where important mechanical models, such as waves or oscillations, lose energy over time, typically from friction or turbulence. The lost energy converts into heat, which raises the temperature of the system. Such systems are called...
of energy through the channel, which has an impact on stream velocity and turbulence
Turbulence
In fluid dynamics, turbulence or turbulent flow is a flow regime characterized by chaotic and stochastic property changes. This includes low momentum diffusion, high momentum convection, and rapid variation of pressure and velocity in space and time...
, sediment
Sediment transport
Sediment transport is the movement of solid particles , typically due to a combination of the force of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained...
volume and size distribution, scour, and water surface elevations, among other characteristics.
Cross-vanes and related structures
A cross-vane is a "U"-shaped structure of boulderBoulder
In geology, a boulder is a rock with grain size of usually no less than 256 mm diameter. While a boulder may be small enough to move or roll manually, others are extremely massive....
s 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.
Engineered log jams
An emerging stream restoration technique is the installation of engineered log jamLog jam
A log jam is an accumulation of Large Woody Debris that can span an entire stream or river channel.-Effects on stream/river geomorphology:...
s. Reintroduction of large woody debris
Large Woody Debris
Large woody debris are the logs, sticks, branches, and other wood that falls into streams and rivers. This debris can influence the flow and the shape of the stream channel...
into a stream is a fairly recent method that is being experimented with in streams such as Thornton Creek
Thornton Creek
Thornton Creek is 18 miles of urban creeks and tributaries from southeast Shoreline through northeast Seattle to Lake Washington. The creek is the largest watershed in Seattle, draining a region of relatively dense biodiversity for an urban setting, home to frogs, newts, ducks, other birds, and...
, 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
Erosion
Erosion is when materials are removed from the surface and changed into something else. It only works by hydraulic actions and transport of solids in the natural environment, and leads to the deposition of these materials elsewhere...
. A second element of engineered log jam
Log jam
A log jam is an accumulation of Large Woody Debris that can span an entire stream or river channel.-Effects on stream/river geomorphology:...
s 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.
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.
Off-line techniques
As part of a stream restoration project, stormwaterStormwater
Stormwater is water that originates during precipitation events. It may also be used to apply to water that originates with snowmelt that enters the stormwater system...
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:
- BioretentionBioretentionBioretention is the process in which contaminants and sedimentation are removed from stormwater runoff. Stormwater is collected into the treatment area which consists of a grass buffer strip, sand bed, ponding area, organic layer or mulch layer, planting soil, and plants...
systems and rain gardenRain gardenA rain garden is a planted depression that allows rainwater runoff from impervious urban areas like roofs, driveways, walkways, parking lots, and compacted lawn areas the opportunity to be absorbed...
s - Constructed wetlandConstructed wetlandA constructed wetland or wetpark is an artificial wetland, marsh or swamp created as a new or restored habitat for native and migratory wildlife, for anthropogenic discharge such as wastewater, stormwater runoff, or sewage treatment, for land reclamation after mining, refineries, or other...
s - Infiltration basinInfiltration basinAn infiltration basin , is a type of best management practice that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay...
s - Retention basinRetention basinA retention basin is used to manage stormwater runoff to prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. Sometimes called a wet pond or wet detention basin, it is an artificial lake with vegetation around the perimeter, and includes a...
s.
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 spawningSpawn (biology)
Spawn refers to the eggs and sperm released or deposited, usually into water, by aquatic animals. As a verb, spawn refers to the process of releasing the eggs and sperm, also called spawning...
, therefore monitoring efforts may be conducted for several years after a restoration project has completed.
See also
- Daylighting (streams)Daylighting (streams)In urban design and urban planning, daylighting is the redirection of a stream into an above-ground channel. Typically, the goal is to restore a stream of water to a more natural state...
- Environmental restorationEnvironmental restorationEnvironmental restoration is a term common in the citizens’ environmental movement. Environmental restoration is closely allied with ecological restoration or environmental remediation...
- Land rehabilitationLand rehabilitationLand rehabilitation is the process of returning the land in a given area to some degree of its former state, after some process has resulted in its damage...
- Retrofit (environmental management)
- Riparian zone restorationRiparian zone restorationRiparian zone restoration is the ecological restoration of riparian zone habitats of streams, rivers, springs, lakes, floodplains, and other hydrologic ecologies.Riparian zones have been degraded throughout much of the world...
External links
- National River Restoration Science Synthesis (NRRSS) Project U.S.-based research compendium
- Restoring Rivers American Rivers (non-profit organization)
- River Corridor and Wetland Restoration - U.S. EPA
- River Restoration Centre - UK