A well preserved Riparian strip on a tributary to Lake Erie.
- "Riparian" redirects here. For the legal doctrine, see "riparian water rights."
A riparian zone or riparian area is the interface between land and a stream. Plant communities along the river margins are called riparian vegetation, characterized by hydrophilic plants. Riparian zones are significant in ecology, environmental management, and civil engineering because of their role in soil conservation, their biodiversity, and the influence they have on aquatic ecosystems. Riparian zones occur in many forms including grassland, woodland, wetland or even non-vegetative. In some regions the terms riparian woodland, riparian forest, riparian buffer zone, or riparian strip are used to characterize a riparian zone. The word "riparian" is derived from Latin ripa, meaning river bank.
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 is an important part of stream temperature regulation. 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.
Research shows riparian zones are instrumental in water quality improvement for both surface runoff and water flowing into streams through subsurface or groundwater flow. Particularly the attenuation of nitrate or denitrification of the nitrates from fertilizer in this buffer zone is important. Riparian zones can play a role in lowering nitrate contamination in surface runoff from agricultural fields, which runoff would otherwise damage ecosystems and human health. 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
Riparian zones dissipate stream energy. The meandering curves of a river, combined with vegetation and root systems, dissipate stream energy, which results in less soil erosion and a reduction in 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 which enhances water quality via biofiltration.
The riparian zones also provide wildlife habitat, increase biodiversity, and provide wildlife corridors, enabling aquatic and riparian organisms to move along river systems avoiding isolated communities. They can provide forage for wildlife and livestock.
They provide native landscape irrigation by extending seasonal or perennial flows of water. Nutrients from terrestrial vegetation (e.g. leaf litter and insect drop) is 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 including 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 urbanisation and increased boatwake 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, leaf litter, woody material, and reduce the delivery of soil eroded from the harvested area. Factors such as soil types and root structures, climatic conditions and above ground vegetative cover impact the effectiveness of riparian buffering.
Vegetation
The assortment of riparian zone trees varies from those of wetlands and typically consists of plants that either are emergent aquatic plants, or herbs, trees and shrubs that thrive in proximity to water. Typical riparian zone trees in the eastern United States include:
- Cottonwood, Populus deltoides
- Silver maple, Acer saccharinum
- Boxelder, Acer negundo
- American elm, Ulmus americana
- American sycamore, Platanus occidentalis
- Butternut, Juglans cinerea
- Black walnut, Juglans nigra
- Black willow, Salix nigra
- River birch, Betula nigra
- Green ash, Fraxinus pensylvanica
- Honey locust, Gleditsia triacanthos
- Basswood, Tilia americana
In the western United States riparian vegetation may include red willow, Juncus, grasses, sedges and wingstem. In Asia there are different types of riparian vegetation, but the interactions between hydrology and ecology are similar1.
Typical riparian vegetation in New South Wales, Australia include:
- Blackwood, Acacia melanoxylon
- Ovens Wattle, Acacia pravissima
- Red Stem Wattle, Acacia rubida
- Blackthorn, Bursaria lasiophylla
- Crimson Bottlebrush, Callistemon citrinus
- River Bottlebrush, Callistemon sieberi syn. paludosa
- River She-Oak, Casuarina cunninghamiana
- Apple Box, Eucalyptus bridgesiana
- River Red Gum, Eucalyptus camaldulensis
- Yellow Box, Eucalyptus melliodora
- Ribbon/Manna Gum, Eucalyptus viminalis
- Burgan, Kunzea erocoides
- River Tea-Tree, Leptospernum obovatum
- Swamp Paperbark, Melaleuca ericifolia
Typical riparian zone trees in Central Europe include:
- Field Maple, Acer campestre
- Sycamore Maple, Acer pseudoplatanus
- Black Alder, Alnus glutinosa
- European Hornbeam, Carpinus betulus
- European Ash, Fraxinus excelsior
- Persian Walnut, Juglans regia
- European Wild Apple, Malus sylvestris
- White Poplar, Populus alba
- Black Poplar, Populus nigra
- Pedunculate Oak, Quercus robur
- White Willow, Salix alba
- Crack Willow, Salix fragilis
- Small-leaved Lime, Tilia cordata
- European White Elm, Ulmus laevis
- Field Elm, Ulmus minor
See also
References
- Nakasone, H., Kuroda, H., Kato, T. and Tabuchi, T. (2003). Nitrogen removal from water containing high nitrate nitrogen in a paddy field (wetland). Water Science and Technology, vol.48, no.10, pp.209-216.
- Mengis, M., Schiff, S.L., Harris, M., English, M.C., Aravena, R., Elgood, R.J., and MacLean, A. (1999). Multiple geochemical and isotopic approaches for assessing ground water NO3 elimination in a riparian zone. Ground Water, 37, 448-457.
- Parkyn, Stephanie. (2004). Review of Riparian Buffer Zone Effectiveness. Ministry of Agriculture and Forestry (New Zealand), www.maf.govt.nz/publications.
- Tang, Changyuan; Azuma, Kazuaki; Iwami, Yoshifumi; Ohji, Baku; Sakura, Yasuo. (2004). Nitrate behaviour in the groundwater of a headwater wetland, Chiba, Japan. Hydrological Processes, vol.18, no.16, pp.3159-3168.
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