Exposed riverine sediments, or ERS, are composed of

silt Silt is granular material of a size between sand and clay and composed mostly of broken grains of quartz. Silt may occur as a soil (often mixed with sand or clay) or as sediment mixed in suspension (chemistry), suspension with water. Silt usually ...

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is usually defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural ...

and

gravel Gravel () is a loose aggregation of rock fragments. Gravel occurs naturally on Earth as a result of sedimentation, sedimentary and erosion, erosive geological processes; it is also produced in large quantities commercially as crushed stone. Gr ...

deposited by streams but exposed as water level falls. Other terms for ERS include river shingle, point bars, berms and

shoal In oceanography, geomorphology, and Earth science, geoscience, a shoal is a natural submerged ridge, bank (geography), bank, or bar that consists of, or is covered by, sand or other unconsolidated material, and rises from the bed of a body ...

s and they are most common in actively

meander A meander is one of a series of regular sinuous curves in the Channel (geography), channel of a river or other watercourse. It is produced as a watercourse erosion, erodes the sediments of an outer, concave bank (cut bank, cut bank or river cl ...

ing and

braided river A braided river (also called braided channel or braided stream) consists of a network of river channel (geography), channels separated by small, often temporary, islands called ''braid bars'' or, in British English usage, ''aits'' or ''eyots''. ...

s. Adrian Fowles of the

Countryside Council for Wales The Countryside Council for Wales (CCW; ) was a Welsh Assembly sponsored body responsible for wildlife conservation, landscape and countryside access in Wales. It merged with Forestry Commission Wales, and Environment Agency Wales to form ...

and members of the UK

Environment Agency The Environment Agency (EA) is a non-departmental public body, established in 1996 and sponsored by the United Kingdom government's Department for Environment, Food and Rural Affairs, with responsibilities relating to the protection and enha ...

in 1993 coined ‘exposed riverine sediments’ as a term to describe the full scope of these related microhabitats. Their aim in-so-doing was to reduce confusion and pull together the conservation and scientific investigation of these

habitats In ecology, habitat refers to the array of resources, 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 manifestation of its ...

. Bates and Sadler (2005)Bates, A.J., and J.P. Sadler. 2005. ''The ecology and conservation of beetles associated with exposed riverine sediments''. CCW Contract Science Report No.688. have since further defined exposed riverine sediments as:

''Exposed, within channel,
fluvial A river is a natural stream of fresh water that flows on land or inside caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of its course if it ru ...
ly deposited sediments (gravels, sands and silts) that lack continuous
vegetation Vegetation is an assemblage of plants and the ground cover they provide. It is a general term, without specific reference to particular Taxon, taxa, life forms, structure, Spatial ecology, spatial extent, or any other specific Botany, botanic ...
cover, whose vertical distribution lies between the levels of bankfull and the typical baseflow of the
river A river is a natural stream of fresh water that flows on land or inside Subterranean river, caves towards another body of water at a lower elevation, such as an ocean, lake, or another river. A river may run dry before reaching the end of ...
.''

Therefore, eroding river banks are ERS because they are usually composed of fluvially deposited sediment. Whereas areas of the

stream bed A streambed or stream bed is the bottom of a stream or river and is confined within a Stream channel, channel or the Bank (geography), banks of the waterway. Usually, the bed does not contain terrestrial (land) vegetation and instead supports d ...

and over-bank deposits are not ERS because they are only exposed when water levels are unusually low and are more elevated than the bankfull level respectively. The term ERS is slowly becoming more common and has now been used in a large number of published papers, for example:
Petts et al. 2000Eyre et al. 2001
*Sadler et al. 2004
Looy et al. 2005Tockner et al. 2006Bates et al. 2006

ERS habitat

A casual glance at ERS would suggest a harsh, relatively un-inhabited habitat with little value. However, ERS habitats are of considerable conservation importance because of their high species diversity, high degree of species specialisation, and large number of rare and

endangered species An endangered species is a species that is very likely to become extinct in the near future, either worldwide or in a particular political jurisdiction. Endangered species may be at risk due to factors such as habitat loss, poaching, inv ...

. ERS are of substantial importance for a small number of vertebrate species, such as the rare little ringed plover, but for the most part their value lies in their invertebrate fauna. The

United Kingdom The United Kingdom of Great Britain and Northern Ireland, commonly known as the United Kingdom (UK) or Britain, is a country in Northwestern Europe, off the coast of European mainland, the continental mainland. It comprises England, Scotlan ...

Biodiversity Action Plan, for example, lists eight species of beetle:
''Bembidion testaceum''
''See also'' Bembidion ''in

Wikispecies Wikispecies is a wiki-based online project supported by the Wikimedia Foundation. Its aim is to create a comprehensive open content catalogue of all species; the project is directed at scientists, rather than at the general public. Jimmy Wales s ...

''.
''Lionychus quadrillum''''Perileptus areolatus''
''See also'' Perileptus ''in

''.
''Meotica anglica''
''See also'' Meotica ''in

''.
''Thinobius newberyi''
''See also'' Thinobius ''in

''.
''Hydrochus nitidicollis''
''See also'' Hydrochus ''in

''.
''Dyschirius angustatus''
''See also'' Dyschirius ''in

''.
''Bidessus minutisimus''
''See also'' Bidessus ''in

''. and two species of stilleto fly:
Southern silver stiletto-fly''Cliorismia rustica''

''Spiriverpa lunulata''
. that are associated with ERS.

ERS dynamics

ERS rely on a continued supply of sediment from upstream, and periodic disturbances from

flooding 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 of significant concern in agriculture, civi ...

to prevent

ecological succession Ecological succession is the process of how species compositions change in an Community (ecology), ecological community over time. The two main categories of ecological succession are primary succession and secondary succession. Primary successi ...

to more vegetated

riparian A riparian zone or riparian area is the interface between land and a river or stream. In some regions, the terms riparian woodland, riparian forest, riparian buffer zone, riparian corridor, and riparian strip are used to characterize a ripar ...

habitat.

Threats to ERS

Many of the threats to ERS act to: #reduce the supply of sediment by interrupting its downstream transfer: ##

dam A dam is a barrier that stops or restricts the flow of surface water or underground streams. Reservoirs created by dams not only suppress floods but also provide water for activities such as irrigation, human consumption, industrial use, aqua ...

construction ##

construction aggregate Construction aggregate, or simply aggregate, is a broad category of coarse- to medium-grained particulate material used in construction. Traditionally, it includes natural materials such as sand, gravel, crushed stone. As with other types of ag ...

extraction ##reducing river

erosion Erosion is the action of surface processes (such as Surface runoff, water flow or wind) that removes soil, Rock (geology), rock, or dissolved material from one location on the Earth's crust#Crust, Earth's crust and then sediment transport, tran ...

(

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 ...

and dam construction) #reduce the frequency and magnitude of floods (dam construction) (Plachter and Reich 1998, Sadler et al. 2005, Tockner et al. 2006). Other threats operate over smaller scales, such as livestock trampling.

References

Further general reference material

*Bates, A.J., J.P. Sadler, and A.P. Fowles. 2006. Condition-dependent dispersal of a patchily distributed riparian ground beetle in response to disturbance. ''Oecologia'' 150:50-60. *Eyre, M. D., M. L. Luff, and D. A. Phillips. 2001. The ground beetles (Coleoptera: Carabidae) of exposed riverine sediments in Scotland and northern England. ''Biodiversity & Conservation'' 10:403-426. *Looy, K. V., S. Vanacker, H. Jochems, G. de Blust, and Dufrêne. 2005. Ground beetle habitat templets and riverbank integrity. ''River Research & Applications'' 21:1133-1146. *Petts, G. E., A. M. Gurnell, A. J. Gerrard, D. M. Hannah, B. Hansford, I. Morrissey, P. J. Edwards, J. Kollmann, J. V. Ward, K. Tockner, and B. P. G. Smith. 2000. Longitudinal variations in exposed riverine sediments: a context for the ecology of the Fiume Tagliamento, Italy. ''Aquatic Conservation: Marine and Freshwater Ecosystems'' 10:249-266. {{DEFAULTSORT:Exposed Riverine Sediments Habitats