Exposed riverine sediments
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Exposed riverine sediments, or ERS, are composed of silt, sand and gravel deposited by streams but exposed as water level falls.
Other terms for ERS include river shingle, point bars, berms and shoals and they are most common in actively meandering and braided rivers.
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| An exposed shoal. | An intermittent braided water course showing fluvial deposits. | A sand bar and the opposite bank. |
| Unspecified river, Bangladesh | Medano Creek, Great Sand Dunes National Park and Preserve, Colorado, United States | Namoi River, New South Wales, Australia |
Adrian Fowles of the Countryside Council for Wales and members of the UK Environment Agency 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. Bates and Sadler (2005)[1] have since further defined exposed riverine sediments as:
Exposed, within channel, fluvially deposited sediments (gravels, sands and silts) that lack continuous vegetation cover, whose vertical distribution lies between the levels of bankfull and the typical baseflow of the river.
Therefore, eroding river banks are ERS because they are usually composed of fluvially deposited sediment. Whereas areas of the stream bed 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. 2000
- Eyre et al. 2001
- Sadler et al. 2004[2]
- Looy et al. 2005
- Tockner et al. 2006
- Bates et al. 2006