Riparian zone

A riparian zone or riparian area is the interface between land and a river or stream. Riparian is also the proper nomenclature for one of the terrestrial biomes of the Earth. Plant habitats and communities along the river margins and banks are called riparian vegetation, characterized by hydrophilic plants. Riparian zones are important in ecology, environmental resource management, and civil engineering because of their role in soil conservation, their habitat biodiversity, and the influence they have on fauna and aquatic ecosystems, including grasslands, woodlands, wetlands, or even non-vegetative areas. In some regions the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor and riparian strip are used to characterize a riparian zone. The word riparian is derived from Latin ripa, meaning river bank.

Riparian strip
A well-preserved natural riparian strip on a tributary to Lake Erie

Characteristics

Riparian zones may be natural or engineered for soil stabilization or restoration. These zones are important natural biofilters, protecting aquatic environments from excessive sedimentation, polluted surface runoff and erosion. They supply shelter and food for many aquatic animals and shade that limits stream temperature change. When riparian zones are damaged by construction, agriculture or silviculture, biological restoration can take place, usually by human intervention in erosion control and revegetation. If the area adjacent to a watercourse has standing water or saturated soil for as long as a season, it is normally termed a wetland because of its hydric soil characteristics. Because of their prominent role in supporting a diversity of species, riparian zones are often the subject of national protection in a biodiversity action plan. These are also known as a "Plant or Vegetation Waste Buffer".

Research shows that riparian zones are instrumental in water quality improvement for both surface runoff and water flowing into streams through subsurface or groundwater flow. Riparian zones can play a role in lowering nitrate contamination in surface runoff, such as manure and other fertilizers from agricultural fields, that would otherwise damage ecosystems and human health. Particularly, the attenuation of nitrate or denitrification of the nitrates from fertilizer in this buffer zone is important. The use of wetland riparian zones shows a particularly high rate of removal of nitrate entering a stream and thus has a place in agricultural management.

Roles and functions

Pisuerga2
Thick riparian vegetation along the Pisuerga River in Spain

Riparian zones dissipate stream energy. The meandering curves of a river, combined with vegetation and root systems, slow the flow of water, which reduces soil erosion and flood damage. Sediment is trapped, reducing suspended solids to create less turbid water, replenish soils, and build stream banks. Pollutants are filtered from surface runoff, enhancing water quality via biofiltration.

The riparian zones also provide wildlife habitat, increased biodiversity, and wildlife corridors, enabling aquatic and riparian organisms to move along river systems avoiding isolated communities. Riparian vegetation can also provide forage for wildlife and livestock.

Riparian zones are also important for the fish that live within rivers, such as brook and charr. Impacts to riparian zones can affect fish, and restoration is not always sufficient to recover fish populations.[1]

They provide native landscape irrigation by extending seasonal or perennial flows of water. Nutrients from terrestrial vegetation (e.g. plant litter and insect drop) are transferred to aquatic food webs. The vegetation surrounding the stream helps to shade the water, mitigating water temperature changes. The vegetation also contributes wood debris to streams, which is important to maintaining geomorphology.

From a social aspect, riparian zones contribute to nearby property values through amenity and views, and they improve enjoyment for footpaths and bikeways through supporting foreshoreway networks. Space is created for riparian sports such as fishing, swimming and launching for vessels and paddlecraft.

The riparian zone acts as a sacrificial erosion buffer to absorb impacts of factors including climate change, increased runoff from urbanization and increased boat wake without damaging structures located behind a setback zone.

Role in logging

The protection of riparian zones is often a consideration in logging operations. The undisturbed soil, soil cover, and vegetation provide shade, plant litter, and woody material, and reduce the delivery of soil eroded from the harvested area. Factors such as soil types and root structures, climatic conditions and vegetative cover determine the effectiveness of riparian buffering.

Vegetation

Willow Creek, Trout Creek Mountains, Oregon
Riparian zone along Trout Creek in the Trout Creek Mountains, part of the Burns Bureau of Land Management District in southeastern Oregon. The creek provides critical habitat for trout.

The assortment of riparian zone trees varies from those of wetlands and typically consists of plants that are either emergent aquatic plants, or herbs, trees and shrubs that thrive in proximity to water.

North America

Water's edge

Herbaceous Perennial:

Inundated riparian zone

Herbaceous Perennial:[2]

Western

In western North America and the Pacific coast, the riparian vegetation includes:

Riparian trees[3]

Riparian shrubs[3]

Other plants

Asia

In Asia there are different types of riparian vegetation, but the interactions between hydrology and ecology are similar as occurs in other geographic areas.[4]

Australia

Typical riparian vegetation in Temperate New South Wales, Australia include:

Central Europe

Typical riparian zone trees in Central Europe include:

Repair and restoration

Land clearing followed by floods can quickly erode a riverbank, taking valuable grasses and soils downstream, and later allowing the sun to bake the land dry. Natural Sequence Farming techniques have been used in the Upper Hunter Valley of New South Wales, Australia, in an attempt to rapidly restore eroded farms to optimum productivity.

The Natural Sequence Farming technique involves placing obstacles in the water's pathway to lessen the energy of a flood, and help the water to deposit soil and seep into the flood zone. Another technique is to quickly establish ecological succession by encouraging fast-growing plants such as "weeds" (pioneer species) to grow. These may spread along the watercourse and cause environmental degradation, but may stabilize the soil, place carbon into the ground, and protect the land from drying. The weeds will improve the streambeds so that trees and grasses can return, and later ideally replace the weeds. There are several other techniques used by government and non-government agencies to address riparian and streambed degradation, ranging from the installation of bed control structures such as log sills to the use of pin groynes or rock emplacement.

Cottonwood Creek, BLM, Oregon, 1988

Cottonwood Creek riparian area in southeastern Oregon before restoration, 1988

Cottonwood Creek, BLM, Oregon, 2000

Cottonwood Creek riparian area during recovery, 2000

Cottonwood Creek, BLM, Oregon, 2002

Cottonwood Creek riparian area after restoration, 2002

See also

References

  1. ^ Sievers, Michael; Hale, Robin; Morrongiello, John R. (March 2017). "Do trout respond to riparian change? A meta-analysis with implications for restoration and management". Freshwater Biology. 62 (3): 445–457. doi:10.1111/fwb.12888.
  2. ^ "List of trees and plants". Archived from the original (xls) on July 18, 2011. Retrieved 2010-09-29.
  3. ^ a b Cooke, Sarah Spear (1997). A Field Guide to the Common Wetland Plants of Western Washington and Northwestern Oregon. Seattle, Washington: Seattle Audubon Society. ISBN 978-0-914516-11-8.
  4. ^ "Riparian Vegetation Along the Middle and Lower Zones of the Chalakkudy River, Kerala, India" (PDF). Kerala Research Programme Centre for Development Studies. Archived from the original (PDF) on 2009-03-19. Retrieved 2009-10-02.

Further reading

  • Nakasone, H.; Kuroda, H.; Kato, T.; Tabuchi, T. (2003). "Nitrogen removal from water containing high nitrate nitrogen in a paddy field (wetland)". Water Science and Technology. 48 (10): 209–216. doi:10.2166/wst.2003.0576.
  • Mengis, M.; Schif, S. L.; Harris, M.; English, M. C.; Aravena, R.; Elgood, R. J.; MacLean, A. (1999). "Multiple Geochemical and Isotopic Approaches for Assessing Ground Water NO3 Elimination in a Riparian Zone". Ground Water. 37 (3): 448–457. doi:10.1111/j.1745-6584.1999.tb01124.x.
  • Parkyn, Stephanie. (2004). Review of Riparian Buffer Zone Effectiveness. Ministry of Agriculture and Forestry (New Zealand), www.maf.govt.nz/publications.
  • Tang, C.; Azuma, K.; Iwami, Y.; Ohji, B.; Sakura, Y. (2004). "Nitrate behaviour in the groundwater of a headwater wetland, Chiba, Japan". Hydrological Processes. 18 (16): 3159–3168. Bibcode:2004HyPr...18.3159T. doi:10.1002/hyp.5755.
  • Riparian Bibliography, National Agroforestry Center
  • Conservation Buffer Design Guidelines

External links

Backswamp

In geology a backswamp is a type of depositional environment commonly found in a floodplain. It is where deposits of fine silts and clays settle after a flood. Backswamps usually lie behind a stream's natural levees. During a flood, water levels will rise over the height of the levee, filling the floodplain with water and sediments. Once the flooding stops there is no place for the water to drain out, so the sediments it carried remain and settle. A backswamp usually lies where a bow river once flowed. A backswamp lies lower than the rest of the river valley.

Bank (geography)

In geography, the word bank generally refers to the land alongside a body of water. Different structures are referred to as banks in different fields of geography, as follows.

In limnology (the study of inland waters), a stream bank or river bank is the terrain alongside the bed of a river, creek, or stream. The bank consists of the sides of the channel, between which the flow is confined. Stream banks are of particular interest in fluvial geography, which studies the processes associated with rivers and streams and the deposits and landforms created by them. Bankfull discharge is a discharge great enough to fill the channel and overtop the banks.The descriptive terms left bank and right bank refer to the perspective of an observer looking downstream, a well-known example of this being the sections of Paris as defined by the river Seine. The shoreline of ponds, swamps, estuaries, reservoirs, or lakes are also of interest in limnology and are sometimes referred to as banks. The grade of all these banks or shorelines can vary from vertical to a shallow slope.

In freshwater ecology, banks are of interest as the location of riparian habitats. Riparian zones occur along upland and lowland river and stream beds. The ecology around and depending on a marsh, swamp, slough, or estuary, sometimes called a bank, is likewise studied in freshwater ecology.

Banks are also of interest in navigation, where the term can refer either to a barrier island or a submerged plateau, such as an ocean bank. A barrier island is a long narrow island composed of sand and forming a barrier between an island lagoon or sound and the ocean. A submerged plateau is a relatively flat topped elevation of the sea floor at shallow depth (generally less than 200 m), typically on the continental shelf or near an island.

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 preventing water pollution, soil loss, wildlife habitat loss and human property loss.

Flood-meadow

A flood-meadow (or floodmeadow) is an area of grassland or pasture beside a river, subject to seasonal flooding. Flood-meadows are distinct from water-meadows in that the latter are artificially created and maintained, with flooding controlled on a seasonal and even daily basis.

Floodplain

A floodplain or flood plain is an area of land adjacent to a stream or 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. The soils usually consist of levees, silts, and sands deposited during floods. Levees are the heaviest materials (usually pebble-size) and they are deposited first; silts and sands are finer materials.

Fluvial terrace

Fluvial terraces are elongated terraces that flank the sides of floodplains and fluvial valleys all over the world. They consist of a relatively level strip of land, called a “tread,” separated from either an adjacent floodplain, other fluvial terraces, or uplands by distinctly steeper strips of land called “risers.” These terraces lie parallel to and above the river channel and its floodplain. Because of the manner in which they form, fluvial terraces are underlain by fluvial sediments of highly variable thickness.Fluvial terraces are the remnants of earlier floodplains that existed at a time when either a stream or river was flowing at a higher elevation before its channel downcut to create a new floodplain at a lower elevation. Changes in elevation can be due to changes in the base level (elevation of the lowest point in the fluvial system, usually the drainage basin) of the fluvial system, which leads to headward erosion along the length of either a stream or river, gradually lowering its elevation. For example, downcutting by a river can lead to increased velocity of a tributary, causing that tributary to erode toward its headwaters. Terraces can also be left behind when the volume of the fluvial flow declines due to changes in climate, typical of areas which were covered by ice during periods of glaciation, and their adjacent drainage basins.

Gallery forest

Gallery forests are forests that form as corridors along rivers or wetlands and project into landscapes that are otherwise only sparsely treed such as savannas, grasslands, or deserts.

Gallery forests are able to exist where the surrounding landscape does not support forests for a number of reasons. The riparian zones in which they grow offer greater protection from fire which would kill tree seedlings. In addition, the alluvial soils of the gallery habitat are often of higher fertility and have better drainage than the soils of the surrounding landscape with a more reliable water supply at depth. As a result, the boundary between gallery forest and the surrounding woodland or grassland is usually abrupt, with the ecotone being only a few metres wide.Gallery forests have shrunk in extent worldwide as a result of human activities, including domestic livestock's preventing tree seedling establishment and the construction of dams and weirs causing flooding or interfering with natural stream flow. In addition to these disturbances, gallery forests are also threatened by many of the same processes that threaten savannas.

Hooghly River

The Hooghly River (Hugli; Anglicized alternatively spelled Hoogli or Hugli) or the Bhāgirathi-Hooghly, traditionally called 'Ganga', and also called Kati-Ganga, is an approximately 260-kilometre-long (160 mi) distributary of the Ganges River in West Bengal, India. The Ganges splits into the Padma and the Hooghly near Giria, Murshidabad. Today there is a further man-made bifurcation of the river upstream at Farakka. The Padma flows eastward into Bangladesh, whereas the Hooghly flows south through West Bengal. The river flows through the Rarh region, the lower deltaic districts of West Bengal, and eventually into the Bay of Bengal. The upper riparian zone of the river is called Bhagirathi while the lower riparian zone is called Hooghly. Major rivers that drain into the Bhagirathi-Hooghly include Mayurakshi, Jalangi, Ajay, Damodar, Rupnarayan and Haldi rivers other than the Ganges. Calcutta and Hugli-Chinsura, the headquarters of Hooghly (district), are located on the banks of this river.

Hydric soil

Hydric soil is soil which is permanently or seasonally saturated by water, resulting in anaerobic conditions, as found in wetlands.

Landscape limnology

Landscape limnology is the spatially explicit study of lakes, streams, and wetlands as they interact with freshwater, terrestrial, and human landscapes to determine the effects of pattern on ecosystem processes across temporal and spatial scales. Limnology is the study of inland water bodies inclusive of rivers, lakes, and wetlands; landscape limnology seeks to integrate all of these ecosystem types.

The terrestrial component represents spatial hierarchies of landscape features that influence which materials, whether solutes or organisms, are transported to aquatic systems; aquatic connections represent how these materials are transported; and human activities reflect features that influence how these materials are transported as well as their quantity and temporal dynamics.

Lilly Arbor Project

The Lilly Arbor Project is a part of an experimental riparian floodplain reforestation and ecological restoration program, located along the White River in Indiana, in the eastern United States.

Polder

A polder (Dutch pronunciation: [ˈpɔldər] (listen)) is a low-lying tract of land that forms an artificial hydrological entity, enclosed by embankments known as dikes. There are three types of polder:

Land reclaimed from a body of water, such as a lake or the sea bed

Flood plains separated from the sea or river by a dike

Marshes separated from the surrounding water by a dike and subsequently drained; these are also known as koogs especially in GermanyThe ground level in drained marshes subsides over time. All polders will eventually be below the surrounding water level some or all of the time. Water enters the low-lying polder through infiltration and water pressure of ground water, or rainfall, or transport of water by rivers and canals. This usually means that the polder has an excess of water, which is pumped out or drained by opening sluices at low tide. Care must be taken not to set the internal water level too low. Polder land made up of peat (former marshland) will sink in relation to its previous level, because of peat decomposing when exposed to oxygen from the air.

Polders are at risk from flooding at all times, and care must be taken to protect the surrounding dikes. Dikes are typically built with locally available materials, and each material has its own risks: sand is prone to collapse owing to saturation by water; dry peat is lighter than water and potentially unable to retain water in very dry seasons. Some animals dig tunnels in the barrier, allowing water to infiltrate the structure; the muskrat is known for this activity and hunted in certain European countries because of it. Polders are most commonly, though not exclusively, found in river deltas, former fenlands and coastal areas.

Flooding of polders has also been used as a military tactic in the past. One example is the flooding of the polders along the Yser river during World War I. Opening the sluices at high tide and closing them at low tide turned the polders into an inaccessible swamp which allowed the Allied armies to stop the German army.

Revetment

In stream restoration, river engineering or coastal engineering, revetments are sloping structures placed on banks or cliffs in such a way as to absorb the energy of incoming water. In military engineering they are structures, again sloped, formed to secure an area from artillery, bombing, or stored explosives. River or coastal revetments are usually built to preserve the existing uses of the shoreline and to protect the slope, as defense against erosion.

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 stream. Riparian is also the proper nomenclature for one of the fifteen terrestrial biomes of the earth; the habitats of plant and animal communities along the margins and river banks are called riparian vegetation, characterized by Aquatic plants and animals that favor them. Riparian zones are significant in ecology, environmental management, and civil engineering because of their role in soil conservation, their habitat biodiversity, and the influence they have on fauna and aquatic ecosystems, including grassland, woodland, wetland or sub-surface features such as water tables. In some regions the terms riparian woodland, riparian forest, riparian buffer zone, or riparian strip are used to characterize a riparian zone.

The perceived need for Riparian-zone restoration has come about because riparian zones have been altered and/or degraded throughout much of the world by the activities of mankind affecting natural geologic forces. The unique biodiversity of riparian ecosystems and the potential benefits that natural, vegetated riprarian have to offer in preventing erosion, maintaining water quality that ranges from being decent to completely healthy, providing habitat and wildlife corridors, and maintaining the health of in-stream biota (Aquatic organisms) has led to a surge of restoration activities aimed at riparian ecosystems in the last few decades. Restoration efforts are typically guided by an ecological understanding of riparian-zone processes and knowledge of the causes of degradation. They are often interdependent with stream restoration projects.

Riparian forest

A riparian forest or riparian woodland is a forested or wooded area of land adjacent to a body of water such as a river, stream, pond, lake, marshland, estuary, canal, sink or reservoir.

Riparian water rights

Riparian water rights (or simply riparian rights) is a system for allocating water among those who possess land along its path. It has its origins in English common law. Riparian water rights exist in many jurisdictions with a common law heritage, such as Canada, Australia, and states in the eastern United States.

Common land ownership can be organized into a partition unit, a corporation consisting of the landowners on the shore that formally owns the water area and determines its use.

Stream bed

A stream bed or streambed is the channel bottom of a stream or river, the physical confine of the normal water flow. The lateral confines or channel margins are known as the stream banks or river banks, during all but flood stage. Under certain conditions a river can branch from one stream bed to multiple stream beds. A flood occurs when a stream overflows its banks and flows onto its flood plain. As a general rule, the bed is the part of the channel up to the normal water line, and the banks are that part above the normal water line. However, because water flow varies, this differentiation is subject to local interpretation. Usually, the bed is kept clear of terrestrial vegetation, whereas the banks are subjected to water flow only during unusual or perhaps infrequent high water stages and therefore might support vegetation some or much of the time.

The nature of any stream bed is always a function of the flow dynamics and the local geologic materials, influenced by that flow. With small streams in mesophytic regions, the nature of the stream bed is strongly responsive to conditions of precipitation runoff. Where natural conditions of either grassland or forest ameliorate peak flows, stream beds are stable, possibly rich, with organic matter and exhibit minimal scour. These streams support a rich biota. Where conditions produce unnatural levels of runoff, such as occurs below roads, the stream beds will exhibit a greater amount of scour, often down to bedrock and banks may be undercut. This process greatly increases watershed erosion and results in thinner soils, upslope from the stream bed, as the channel adjusts to the increase in flow. The stream bed is very complex in terms of erosion. Sediment is transported, eroded and deposited on the stream bed. With global warming there is a fear that the size and shape of riverbeds will change due to increased flood magnitude and frequency. However, one study has shown that the majority of sediment washed out in floods is "near-threshold" sediment that has been deposited during normal flow and only needs a slightly higher flow to become mobile again. This shows that the stream bed is left mostly unchanged in size and shape.Beds are usually what would be left once a stream is no longer in existence; the beds are usually well preserved even if they get buried, because the walls and canyons made by the stream usually have hard walls, usually soft sand and debris fill the bed. Dry stream beds are also subject to becoming underground water pockets (buried stream beds only) and flooding by heavy rains and water rising from the ground and may sometimes be part of the rejuvenation of the stream.

Terrace (geology)

In geology, a terrace is a step-like landform. A terrace consists of a flat or gently sloping geomorphic surface, called a tread, that is typically bounded one side by a steeper ascending slope, which is called a "riser" or "scarp." The tread and the steeper descending slope (riser or scarp) together constitute the terrace. Terraces can also consist of a tread bounded on all sides by a descending riser or scarp. A narrow terrace is often called a bench.The sediments underlying the tread and riser of a terrace are also commonly, but incorrectly, called terraces, leading to confusion.

Terraces are formed in various ways.

Upland and lowland

Upland and lowland are conditional descriptions of a plain based on elevation above sea level.

In studies of the ecology of freshwater rivers, habitats are classified as upland or lowland.

Large-scale features
Alluvial rivers
Bedrock river
Bedforms
Regional processes
Mechanics
Aquatic ecosystems
Biomes
Biogeographic
realms
See also
Generally
Classification systems
Organizations

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