![Robinson Creek before](https://upload.wikimedia.org/wikipedia/commons/2/2e/Robinson_Creek_before.jpg)
Stream restoration or river restoration, also sometimes referred to as river reclamation, is work conducted to improve the environmental health of a
river
A river is a natural flowing watercourse, usually freshwater, flowing towards an ocean, sea, lake or another river. In some cases, a river flows into the ground and becomes dry at the end of its course without reaching another body of wate ...
or
stream
A stream is a continuous body of water, body of surface water Current (stream), flowing within the stream bed, bed and bank (geography), banks of a channel (geography), channel. Depending on its location or certain characteristics, a stream ...
, in support of
biodiversity
Biodiversity or biological diversity is the variety and variability of life on Earth. Biodiversity is a measure of variation at the genetic (''genetic variability''), species (''species diversity''), and ecosystem (''ecosystem diversity'') l ...
, recreation,
flood
A flood is an overflow of water ( or rarely other fluids) that submerges land that is usually dry. In the sense of "flowing water", the word may also be applied to the inflow of the tide. Floods are an area of study of the discipline hydrol ...
management and/or landscape development.
[
]
Stream restoration approaches can be divided into two broad categories: form-based restoration, which relies on physical interventions in a stream to improve its conditions; and process-based restoration, which advocates the restoration of
hydrological
Hydrology () is the scientific study of the movement, distribution, and management of water on Earth and other planets, including the water cycle, water resources, and environmental watershed sustainability. A practitioner of hydrology is calle ...
and
geomorphological
Geomorphology (from Ancient Greek: , ', "earth"; , ', "form"; and , ', "study") is the scientific study of the origin and evolution of topographic and bathymetric features created by physical, chemical or biological processes operating at or n ...
processes (such as
sediment transport
Sediment transport is the movement of solid particles (sediment), typically due to a combination of gravity acting on the sediment, and/or the movement of the fluid in which the sediment is entrained. Sediment transport occurs in natural system ...
or connectivity between the
channel
Channel, channels, channeling, etc., may refer to:
Geography
* Channel (geography), in physical geography, a landform consisting of the outline (banks) of the path of a narrow body of water.
Australia
* Channel Country, region of outback Austral ...
and the
floodplain
A floodplain or flood plain or bottomlands is an area of land adjacent to a river which stretches from the banks of its channel to the base of the enclosing valley walls, and which experiences flooding during periods of high discharge.Goudi ...
) to ensure a stream's
resilience and ecological health.
Form-based restoration techniques include deflectors; cross-vanes; weirs, step-pools and other grade-control structures; engineered log jams; bank stabilization methods and other channel-reconfiguration efforts. These induce immediate change in a stream, but sometimes fail to achieve the desired effects if degradation originates at a wider scale. Process-based restoration includes restoring lateral or longitudinal connectivity of water and sediment fluxes and limiting interventions within a corridor defined based on the stream's hydrology and geomorphology. The beneficial effects of process-based restoration projects may sometimes take time to be felt since changes in the stream will occur at a pace that depends on the stream dynamics.
Despite the significant number of stream-restoration projects worldwide, the effectiveness of stream restoration remains poorly quantified, partly due to insufficient
monitoring
Monitoring may refer to:
Science and technology Biology and healthcare
* Monitoring (medicine), the observation of a disease, condition or one or several medical parameters over time
* Baby monitoring
* Biomonitoring, of toxic chemical compounds, ...
.
However, in response to growing environmental awareness, stream-restoration requirements are increasingly adopted in legislation in different parts of the world.
Definition, objectives and popularity
Stream restoration or river restoration, sometimes called river reclamation in the United Kingdom, is a set of activities that aim to improve the environmental health of a river or stream. These activities aim to restore rivers and streams to their original states or to a reference state, in support of biodiversity, recreation, flood management, landscape development, or a combination of these phenomena.
Stream restoration is generally associated with
environmental restoration
Environmental restoration is closely allied with (or perhaps sometimes used interchangeably with) ecological restoration or environmental remediation. In the U.S., remediation is the term used more in the realms of industry, public policy, and c ...
and
ecological restoration
Restoration ecology is the scientific study supporting the practice of ecological restoration, which is the practice of renewing and restoring degraded, damaged, or destroyed ecosystems and habitats in the environment by active human interrupt ...
. In that sense, stream restoration differs from:
*
river engineering
River engineering is a discipline of civil engineering which studies 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 b ...
, a term which typically refers to physical alterations of a water body, for purposes that include navigation, flood control or water supply diversion and are not necessarily related to ecological restoration;
*
waterway restoration
Waterway 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 o ...
, a term used in the United Kingdom describing alterations to a canal or river to improve navigability and related recreational amenities.
Improved stream health may be indicated by expanded
habitat
In ecology, the term habitat summarises the array of resources, physical and biotic factors that are present in an area, such as to support the survival and reproduction of a particular species. A species habitat can be seen as the physical ...
for diverse species (e.g. fish,
aquatic insects, other wildlife) and reduced stream bank
erosion
Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...
, although bank erosion is increasingly generally recognized as contributing to the ecological health of streams.
Enhancements may also include improved
water quality
Water quality refers to the chemical, physical, and biological characteristics of water based on the standards of its usage. It is most frequently used by reference to a set of standards against which compliance, generally achieved through tr ...
(i.e., reduction of
pollutant
A pollutant or novel entity is a substance or energy introduced into the environment that has undesired effects, or adversely affects the usefulness of a resource. These can be both naturally forming (i.e. minerals or extracted compounds like oi ...
levels and increase of
dissolved oxygen
Oxygen saturation (symbol SO2) is a relative measure of the concentration of oxygen that is dissolved or carried in a given medium as a proportion of the maximal concentration that can be dissolved in that medium at the given temperature. It ca ...
levels) and achieving a self-sustaining, resilient stream system that does not require periodic human intervention, such as
dredging
Dredging is the excavation of material from a water environment. Possible reasons for dredging include improving existing water features; reshaping land and water features to alter drainage, navigability, and commercial use; constructing da ...
or construction of flood or
erosion control
Erosion control is the practice of preventing or controlling wind or water erosion in agriculture, land development, coastal areas, river banks and construction. Effective erosion controls handle surface runoff and are important techniques in ...
structures.
Stream restoration projects can also yield increased property values in adjacent areas.
In the past decades, stream restoration has emerged as a significant discipline in the field of water-resources management, due to the degradation of many aquatic and
riparian ecosystems related to human activities.
In the
U.S.A.
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country primarily located in North America. It consists of 50 states, a federal district, five major unincorporated territorie ...
alone, it was estimated in the early 2000s that more than one billion U.S. dollars were spent each year to restore rivers and that close to 40,000 restoration projects had been conducted in the continental part of the country.
Restoration approaches and techniques
![Robinson Creek after](https://upload.wikimedia.org/wikipedia/commons/a/af/Robinson_Creek_after.jpg)
Stream restoration activities may range from the simple improvement or removal of a structure that inhibits natural stream functions (e.g. repairing or replacing a
culvert
A culvert is a structure that channels water past an obstacle or to a subterranean waterway. Typically embedded so as to be surrounded by soil, a culvert may be made from a pipe, reinforced concrete or other material. In the United Kingdom ...
, or removing barriers to fish passage such as
weirs
A weir or low head dam is a barrier across the width of a river that alters the flow characteristics of water and usually results in a change in the height of the river level. Weirs are also used to control the flow of water for outlets of l ...
), to the stabilization of
stream banks, or other interventions such as
riparian zone restoration
Riparian-zone restoration is the ecological restoration of riparian-zone habitats of streams, rivers, springs, lakes, floodplains, and other hydrologic ecologies. A riparian zone or riparian area is the interface between land and a river or stre ...
or the installation of
stormwater
Stormwater, also spelled storm water, is water that originates from precipitation (storm), including heavy rain and meltwater from hail and snow. Stormwater can soak into the soil ( infiltrate) and become groundwater, be stored on depressed la ...
-management facilities like
constructed wetlands
A constructed wetland is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. ...
. The use of
recycled water
Water reclamation (also called wastewater reuse, water reuse or water recycling) is the process of converting municipal wastewater (sewage) or industrial wastewater into water that can be reused for a variety of purposes. Types of reuse include: ...
to augment stream flows that have been depleted as a result of human activities can also be considered a form of stream restoration. When present,
navigation locks have a potential to be operated as vertical slot
fishways to restore fish passage to some extent for a wide range of fish, including poor swimmers.
Stream-restoration projects normally begin with an assessment of a focal stream system, including
climatic
Climate is the long-term weather pattern in an area, typically averaged over 30 years. More rigorously, it is the mean and variability of meteorological variables over a time spanning from months to millions of years. Some of the meteorologic ...
data,
geology
Geology () is a branch of natural science concerned with Earth and other astronomical objects, the features or rocks of which it is composed, and the processes by which they change over time. Modern geology significantly overlaps all other Ear ...
,
watershed hydrology, stream
hydraulics
Hydraulics (from Greek: Υδραυλική) is a technology and applied science using engineering, chemistry, and other sciences involving the mechanical properties and use of liquids. At a very basic level, hydraulics is the liquid counter ...
, sediment transport patterns, channel geometry, historical channel mobility, and flood records.
Numerous systems exist to classify streams according to their geomorphology.
This preliminary assessment helps to understand the stream dynamics and determining the cause of the observed degradation to be addressed; it can also be used to determine the target state for the intended restoration work, especially since the "natural" or undisturbed state is sometimes no longer achievable due to various constraints.
Two broad approaches to stream restoration have been defined in the past decades: form-based restoration and process-based restoration. Whereas the former focuses on the restoration of structural features and/or patterns considered to be characteristic of the target stream system, the latter is based on the restoration of hydrological and geomorphological processes (such as sediment transport or connectivity between the channel and the floodplain) to ensure a stream's resilience and ecological health.
Form-based restoration
Form-based stream restoration promotes the modification of a stream channel to improve stream conditions.
Targeted outcomes can include improved water quality, enhanced
fish habitat Essential Fish Habitat (EFH) was defined by the U.S. Congress in the 1996 amendments to the Magnuson-Stevens Fishery Conservation and Management Act, or Magnuson-Stevens Act, as "those waters and substrate necessary to fish for spawning, breeding, ...
and abundance, as well as increased bank and channel stability.
This approach is widely used worldwide, and is supported by various government agencies, including the
United States Environmental Protection Agency
The Environmental Protection Agency (EPA) is an independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon proposed the establishment of EPA on July 9, 1970; it be ...
(U.S. EPA).
Form-based restoration projects can be carried out at various scales, including the
reach scale. They can include measures such as the installation of in-stream structures, bank stabilization and more significant channel reconfiguration efforts. Reconfiguration work may focus on channel shape (in terms of
sinuosity
Sinuosity, sinuosity index, or sinuosity coefficient of a continuously differentiable curve having at least one inflection point is the ratio of the curvilinear length (along the curve) and the Euclidean distance (straight line) between the e ...
and
meander
A meander is one of a series of regular sinuous curves in the channel of a river or other watercourse. It is produced as a watercourse erodes the sediments of an outer, concave bank ( cut bank) and deposits sediments on an inner, convex bank ...
characteristics), cross-section or channel profile (slope along the channel bed). These alterations affect the
dissipation
In thermodynamics, dissipation is the result of an irreversible process that takes place in homogeneous thermodynamic systems. In a dissipative process, energy (internal, bulk flow kinetic, or system potential) transforms from an initial form to a ...
of energy through a channel, which impacts flow velocity and
turbulence
In fluid dynamics, turbulence or turbulent flow is fluid motion characterized by chaotic changes in pressure and flow velocity. It is in contrast to a laminar flow, which occurs when a fluid flows in parallel layers, with no disruption between ...
, water-surface elevations, sediment transport, and scour, among other characteristics.
Installation of in-stream structures
= Deflectors
=
Deflectors are generally wooden or rock structures installed at a bank toe and extending towards the center of a stream, in order to concentrate stream flow away from its banks. They can limit bank erosion and generate varying flow conditions in terms of depth and velocity, which can positively impact fish habitat.
= Cross-vanes and related structures
=
![Double Cross-Vane Structure (8079839399)](https://upload.wikimedia.org/wikipedia/commons/1/19/Double_Cross-Vane_Structure_%288079839399%29.jpg)
Cross-vanes are "U"-shaped structures made of
boulders
In geology, a boulder (or rarely bowlder) is a rock fragment with size greater than in diameter. Smaller pieces are called cobbles and pebbles. While a boulder may be small enough to move or roll manually, others are extremely massive.
In co ...
or
logs, built across the channel to concentrate stream flow in the center of the channel and thereby reduce bank erosion. They do not impact channel capacity and provides other benefits such as improved habitat for aquatic species. Similar structures used to dissipate stream energy include the W-weirs and J-Hook vanes.
= Weirs, step pools and grade-control structures
=
![Rock Creek - step pool 2013a](https://upload.wikimedia.org/wikipedia/commons/f/f9/Rock_Creek_-_step_pool_2013a.jpg)
These structures, which can be built with rocks or wood (logs or woody debris), gradually lower the elevation of the stream and dissipate flow energy, thereby reducing flow velocity.
They can help limit bed degradation. They generate water accumulation upstream from them and fast flowing conditions downstream from them, which can improve fish habitat. However, they can limit fish passage if they are too high.
=Engineered log jams
=
An emerging stream restoration technique is the installation of engineered
log jams''.'' Because of
channelization and removal of beaver dams and woody debris, many streams lack the hydraulic complexity that is necessary to maintain bank stabilization and healthy aquatic habitats. Reintroduction of
large woody debris
Large woody debris (LWD) 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. Large woody debris, grains, and the shape of the bed of the strea ...
into streams is a method that is being experimented in streams such as
Lagunitas Creek
Lagunitas Creek is a -longU.S. Geological Survey. National Hydrography Dataset high-resolution flowline dataThe National Map, accessed December 27, 2017 northward-flowing stream in Marin County, California. It is critically important to the large ...
in Marin County, California
and
Thornton Creek
Thornton Creek is of urban creeks and tributaries from southeast Shoreline through northeast Seattle to Lake Washington. Its watershed, the largest in Seattle, exhibits relatively dense biodiversity for an urban setting;Brokaw it is home to f ...
, in Seattle, Washington. Log jams add diversity to the water flow by creating riffles, pools, and temperature variations. Large wood pieces, both living
and dead,
play an important role in the long-term stability of engineered log jams. However, individual pieces of wood in log jams are rarely stable over long periods and are naturally transported downstream, where they can get trapped in further log jams, other stream features or human infrastructures, which can generate nuisances for human use.
Bank stabilization
Bank stabilization is a common objective for stream-restoration projects, although bank erosion is generally viewed as favorable for the sustainability and diversity of aquatic and riparian habitats.
This technique may be employed where a stream reach is highly confined, or where
infrastructure
Infrastructure is the set of facilities and systems that serve a country, city, or other area, and encompasses the services and facilities necessary for its economy, households and firms to function. Infrastructure is composed of public and priv ...
is threatened.
Bank stabilization is achieved through the installation of
riprap
Riprap (in North American English), also known as rip rap, rip-rap, shot rock, rock armour (in British English) or rubble, is human-placed rock or other material used to protect shoreline structures against scour and water, wave, or ice erosion. ...
,
gabions
A gabion (from Italian ''gabbione'' meaning "big cage"; from Italian ''gabbia'' and Latin ''cavea'' meaning "cage") is a cage, cylinder or box filled with rocks, concrete, or sometimes sand and soil for use in civil engineering, road building ...
or through the use of
revegetation
Revegetation is the process of replanting and rebuilding the soil of disturbed land. This may be a natural process produced by plant colonization and succession, manmade rewilding projects, accelerated process designed to repair damage to a lan ...
and/or bioengineering methods, which relies on the use of live plants to build bank stabilizing structures. As new plants sprout from the live branches, the roots anchor the soil and prevent erosion.
This makes bioengineering structures more natural and more adaptable to evolving conditions than "hard" engineering structures. Bioengineering structures include
fascines
A fascine is a rough bundle of brushwood or other material used for strengthening an earthen structure, or making a path across uneven or wet terrain. Typical uses are protecting the banks of streams from erosion, covering marshy ground and so ...
, brush mattresses, brush layer, and vegetated geogrids.
Other channel-reconfiguration techniques
Channel reconfiguration involves the physical modification of the stream. Depending on the scale of a project, a channel's cross-section can be modified, and meanders can be constructed through earthworks to achieve the target stream morphology. In the U.S.A., such work is frequently based on the Natural Channel Design (NCD), a method developed in the 1990s. This method involves a classification of the stream to be restored based on parameters such as channel pattern and geometry, topography, slope, and bed material. This classification is followed by a design phase based on the NCD method, which includes 8 phases and 40 steps. The method relies on the construction of the desired morphology, and its stabilization with natural materials such as boulders and vegetation to limit erosion and channel mobility.
Criticisms to form-based restoration
Despite its popularity, form-based restoration has been criticized by the scientific community. Common criticisms are that the scale at which form-based restoration is often much smaller than the spatial and temporal scales of the processes that cause the observed problems and that the target state is frequently influenced by the social conception of what a stream should look like and does not necessarily take into account the stream's geomorphological context (e.g., meandering rivers tend to be viewed as more "natural" and more beautiful, whereas local conditions sometimes favour other patterns such as
braided rivers
A braided river, or braided channel, consists of a network of river channels separated by small, often temporary, islands called braid bars or, in English usage, ''aits'' or ''eyots''.
Braided streams tend to occur in rivers with high sediment lo ...
).
Numerous criticisms have also been directed at the NCD method by fluvial geomorphologists, who claim that the method is a "cookbook" approach sometimes used by practitioners that do not have sufficient knowledge of fluvial geomorphology, resulting in project failures. Another criticism is the importance given to channel stability in the NCD method (and with some other form-based restoration methods), which can limit the streams'
alluvial
Alluvium (from Latin ''alluvius'', from ''alluere'' 'to wash against') is loose clay, silt, sand, or gravel that has been deposited by running water in a stream bed, on a floodplain, in an alluvial fan or beach, or in similar settings. Alluv ...
dynamic and adaptability to evolving conditions.
The NCD method has been criticized for its improper application in the
Washington, D.C.
)
, image_skyline =
, image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...
area to
small-order, interior-forested,
upper-headwater streams and wetlands, leading to loss of natural forest ecosystems.
Process-based restoration
Contrary to form-based restoration, which consists of improving a stream's conditions by modifying its structure, process-based restoration focuses on restoring the hydrological and geomorphological processes (or functions) that contribute to the stream's alluvial and ecological dynamics.
This type of stream restoration has gained in popularity since the mid-1990s, as a more ecosystem-centered approach.
Process-based restoration includes restoring lateral connectivity (between the stream and its floodplain), longitudinal connectivity (along the stream) and water and/or sediment fluxes, which might be impacted by hydro-power dams, grade control structures, erosion control structures and flood protection structures.
Valley Floor Resetting epitomises process-based restoration by infilling the river channel and allowing the stream to carve its anatomised channel anew, matching
Stage Zero on the Stream Evolution Model. In general, process-based restoration aims to maximize the resilience of the system and minimize maintenance requirements.
In some instances, form-based restoration methods might be coupled with process-based restoration to restore key structures and achieve quicker results while waiting for restored processes to ensure adequate conditions in the long term.
Improving connectivity
The connectivity of streams to their adjacent floodplain along their entire length plays an important role in the equilibrium of the river system. Streams are shaped by the water and sediment fluxes from their watershed, and any alteration of these fluxes (either in quantity, intensity or timing) will result in changes in equilibrium planform and cross-sectional geometry, as well as modifications of the aquatic and riparian ecosystem. Removal or modification of levees can allow a better connection between streams and their floodplain.
Similarly, removing dams and grade control structures can restore water and sediment fluxes and result in more diversified habitats, although impacts on fish communities can be difficult to assess.
In streams where existing infrastructures cannot be removed or modified, it is also possible to optimize sediment and water management in order to maximize connectivity and achieve flow patterns that ensure minimum ecosystem requirements. This can include releases from dams, but also delaying and/or treating water from agricultural and urban sources.
Implementing a minimum stream corridor width
Another method of ensuring the ecological health of streams while limiting impacts on human infrastructures is to delineate a corridor within which the stream is expected to migrate over time.
This method is based on the concept of minimum intervention within this corridor, whose limits should be determined based on the stream's hydrology and geomorphology. Although this concept is often restricted to the lateral mobility of streams (related to bank erosion), some systems also integrate the space necessary for floods of various
return periods.
This concept has been developed and adapted in various countries around the world, resulting in the notion of "stream corridor" or "river corridor" in the U.S.A.,
"room for the river" in the Netherlands, "''espace de liberté''" ("freedom space") in France
(where the concept of "erodible corridor" is also used) and Québec (Canada),
"''espace réservé aux eaux''" ("space reserved for water(courses)") in Switzerland,
"''fascia di pertinenza fluviale''" in Italy, "fluvial territory" in Spain and "making space for water" in the United Kingdom.
A cost-benefit analysis has shown that this approach could be beneficial in the long term due to lower stream stabilization and maintenance costs, lower damages resulting from erosion and flooding, and ecological services rendered by the restored streams.
However, this approach cannot be implemented alone if watershed-scale stressors contribute to stream degradation.
Additional practices
![Rain garden overview](https://upload.wikimedia.org/wikipedia/commons/9/9a/Rain_garden_overview.jpg)
In addition to the aforementioned restoration approaches and methods, additional measures can be implemented if stream degradation factors occur at the watershed scale. First, high-quality areas should also be protected. Additional measures include revegetation
/reforestation
Reforestation (occasionally, reafforestation) is the natural or intentional restocking of existing forests and woodlands (forestation) that have been depleted, usually through deforestation, but also after clearcutting.
Management
A debate ...
efforts (ideally with native species); the adoption of agricultural
best management practices
Best or The Best may refer to:
People
* Best (surname), people with the surname Best
* Best (footballer, born 1968), retired Portuguese footballer
Companies and organizations
* Best & Co., an 1879–1971 clothing chain
* Best Lock Corporation, ...
that minimize erosion and
runoff
Runoff, run-off or RUNOFF may refer to:
* RUNOFF, the first computer text-formatting program
* Runoff or run-off, another name for bleed, printing that lies beyond the edges to which a printed sheet is trimmed
* Runoff or run-off, a stock market ...
; adequate treatment of sewage water and industrial discharge across the watershed; and improved stormwater management to delay/minimize the transport of water to the stream and minimize pollutant migration.
Alternative stormwater management facilities include the following options:
*
Bioretention
Bioretention is the process in which contaminants and sedimentation are removed from stormwater runoff. The main objective of the bioretention cell is to attenuate peak runoff as well as to remove stormwater runoff pollutants.
Construction of ...
systems and
rain garden
Rain gardens, also called bioretention facilities, are one of a variety of practices designed to increase rain runoff reabsorption by the soil. They can also be used to treat polluted stormwater runoff. Rain gardens are designed landscape sites t ...
s
*
Constructed wetland
A constructed wetland is an artificial wetland to treat sewage, greywater, stormwater runoff or industrial wastewater. It may also be designed for land reclamation after mining, or as a mitigation step for natural areas lost to land development. ...
s
*
Infiltration basin
An infiltration basin (or recharge basin) is a form of engineered sump or percolation pond that is used to manage stormwater runoff, prevent flooding and downstream erosion, and improve water quality in an adjacent river, stream, lake or bay. It is ...
s
*
Retention basin
A retention basin, sometimes called a wet pond, wet detention basin, or stormwater management pond (SWMP), is an artificial pond with vegetation around the perimeter and a permanent pool of water in its design. It is used to manage stormwater r ...
s
Effectiveness of stream restoration projects
In the 2000s, a study of stream restoration efforts in the U.S.A. led to the creation of the National River Restoration Science Synthesis (NRRSS) database, which included information on over 35,000 stream restoration projects carried out in the U.S.A.
Synthetizing efforts are also carried out in other parts of the world, such as Europe.
However, despite the large number of stream restoration projects carried out each year worldwide, the effectiveness of stream restoration projects remains poorly quantified.
This situation appears to result from limited data on the restored streams' biophysical and geochemical contexts, to insufficient post-monitoring work and to the varying metrics used to evaluate project effectiveness.
Depending on the objectives of the restoration project, the goals (restoration of fish populations, of alluvial dynamics, etc.) may take considerable time to be fully achieved. Therefore, whereas monitoring efforts should be proportional to the scale of the situation to be addressed, long-term is often necessary in order to fully evaluate a project's effectiveness.
In general, project effectiveness has been found to be dependent on selection of an appropriate restoration method considering the nature, cause and scale of the degradation problem. As such, reach-scale projects generally fail at restoring conditions whose root cause lies at the watershed scale, such as water quality issues.
Furthermore, project failures have sometimes been attributed to design based on insufficient scientific bases; in some cases, restoration techniques may have been selected mainly for aesthetic reasons.
Additional factors that can influence the effectiveness of river restoration projects include the selection of sites to be restored (for example, sites located near undisturbed reaches could be recolonized more effectively) and the amount of tree cutting and other destructive work necessary to carry out the restoration work (which can have long-lasting detrimental effects on the quality of the habitat). Although often viewed as a challenge, public involvement is generally considered to be a positive factor for the long-term success of stream restoration projects.
Introduction in legislation
Stream restoration is gradually being introduced in the legislative framework of various states. Examples include the European water framework's commitment to restoring surface water bodies, the adoption of the concept of freedom space in the French legislation,
the inclusion in the Swiss legislation of the notion of space reserved for watercourses and of the requirement to restore streams to a state close to their natural state,
and the inclusion of river corridors in land use planning in the American states of Vermont and Washington.
Although this evolution is generally viewed positively by the scientific community, a concern expressed by some is that it could lead to less flexibility and less room for innovation in a field that is still in development.
Informational resources
The River Restoration Centre, based at
Cranfield University
, mottoeng = After clouds light
, established = 1946 - College of Aeronautics 1969 - Cranfield Institute of Technology (gained university status by royal charter) 1993 - Cranfield University (adopted current name)
, type = Public research uni ...
, is responsible for the National River Restoration Inventory, which is used to document best practice in river watercourse and floodplain restoration, enhancement and management efforts in the United Kingdom. Other established sources for information on stream restoration include the NRRSS in the U.S.A. and the European Centre for River Restoration (ECRR), which holds details of projects across Europe.
ECRR and the LIFE+ RESTORE project have developed a wiki-based inventory of river restoration case studies.
See also
*
Daylighting (streams)
Daylighting can be defined as "opening up buried watercourses and restoring them to more natural conditions". An alternative definition refers to "the practice of removing streams from buried conditions and exposing them to the Earth's surface ...
*
Environmental restoration
Environmental restoration is closely allied with (or perhaps sometimes used interchangeably with) ecological restoration or environmental remediation. In the U.S., remediation is the term used more in the realms of industry, public policy, and c ...
*
Land rehabilitation
Land rehabilitation as a part of environmental remediation is the process of returning the land in a given area to some degree of its former state, after some process (industry, natural disasters, etc.) has resulted in its damage. Many projects ...
*
Retrofit (environmental management)
*
Restoration ecology
Restoration ecology is the scientific study supporting the practice of ecological restoration, which is the practice of renewing and restoring degraded, damaged, or destroyed ecosystems and habitats in the environment by active human interrupt ...
*
Riparian zone restoration
Riparian-zone restoration is the ecological restoration of riparian-zone habitats of streams, rivers, springs, lakes, floodplains, and other hydrologic ecologies. A riparian zone or riparian area is the interface between land and a river or stre ...
*
Subterranean river
A subterranean river is a river that runs wholly or partly beneath the ground surface – one where the riverbed does not represent the surface of the Earth. It is distinct from an aquifer, which may flow like a river but is contained within a per ...
References
Notes
*
*
*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. .
{{Rivers, streams and springs
Water streams
Ecological restoration
Environmental engineering
Environmental terminology
Freshwater ecology
Hydraulic engineering
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Water and the environment