revetment
{{Short description|Structures designed to absorb energy}}{{about|structures used in erosion control and fortifications}}
File:Revetment 2.png filter]]
A revetment in stream restoration, river engineering or coastal engineering is a facing of impact-resistant material (such as stone, concrete, sandbags, or wooden piles) applied to a bank or wall in order to absorb the energy of incoming water and protect it from erosion. River or coastal revetments are usually built to preserve the existing uses of the shoreline and to protect the slope.
In architecture generally, it means a retaining wall. In military engineering it is a structure formed to secure an area from artillery, bombing, or stored explosives.
Freshwater revetments
Many revetments are used to line the banks of freshwater rivers, lakes, and man-made reservoirs, especially to prevent damage during periods of floods or heavy seasonal rains (see riprap). Many materials may be used: wooden piles, loose-piled bouldersLake Ontario Riparian Alliance. [http://www.loranet.org/faqrevet.htm "Stone Revetments...Frequently Asked Questions."] {{Webarchive|url=https://web.archive.org/web/20180930184829/http://www.loranet.org/faqrevet.htm |date=2018-09-30 }} Accessed 2009-05-25. or concrete shapes,[http://www.water-lines.co.uk/index.php?section=252&page=1877 Concrete shaped revetments] {{webarchive|url=https://web.archive.org/web/20090123212001/http://water-lines.co.uk/index.php?section=252&page=1877 |date=2009-01-23 }} or more solid banks.
Concrete revetments are the most common type of infrastructure used to control the Mississippi River.{{Cite news|url=https://www.washingtonpost.com/graphics/2018/national/mississippi-river-infrastructure/|title=The struggle to control the Mississippi can help us understand the U.S.|newspaper=Washington Post|language=en|access-date=2018-05-18}} More than {{Convert|1000|miles|km}} of concrete matting has been placed in river bends between Cairo, Illinois and the Gulf of Mexico to slow the natural erosion that would otherwise frequently change small parts of the river's course.
File:Rock armour revetment Hampton-on-Sea.JPG|Rock armour revetments
File:Liliw,Lagunajf5551 01.JPG|Revetment along Oples River (Liliw, Laguna)
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Revetments as coastal defence
File:Sturdy revetments - geograph.org.uk - 1119250.jpg
File:Cape Lookout dynamic revetment 2020.jpg
Revetments are used as a low-cost solution for coastal erosion defense in areas where crashing waves may otherwise deplete the coastline.
Wooden revetments are made of planks laid against wooden frames so that they disrupt the force of the water. Although once popular, the use of wooden revetments has largely been replaced by modern concrete-based defense structures such as tetrapods. In the 1730s, wooden revetments protecting dikes in the Netherlands were phased out due to the spread of shipworm infestations.{{Cite web|url=http://www.environmentandsociety.org/arcadia/molluscan-explosion-dutch-shipworm-epidemic-1730s|title = Molluscan Explosion: The Dutch Shipworm Epidemic of the 1730s|date = 16 August 2015}}
Dynamic revetments use gravel or cobble-sized rocks to mimic a natural cobble beach for the purpose of reducing wave energy and stopping or slowing coastal erosion.{{cite web |author= Dan Hammock |title=Dynamic revetment revealed as top choice for North Cove shoreline preservation |publisher=Daily World |date=April 20, 2019 |url=https://www.thedailyworld.com/news/dynamic-revetment-revealed-as-top-choice-for-north-cove-shoreline-preservation/}}
Unlike solid structures, dynamic revetments are designed to allow wave action to rearrange the stones into an equilibrium profile, disrupting wave action and dissipating wave energy as the cobbles move. This can reduce the wave reflection which often contributes to beach scouring. {{cite book |author1=John P. Ahrens |title=Coastal Engineering 1990 |chapter=Dynamic Revetments |publisher=22nd International Conference on Coastal Engineering |date=1990 |pages=1837–1850 |doi=10.1061/9780872627765.140 |isbn=9780872627765 |chapter-url=https://ascelibrary.org/doi/10.1061/9780872627765.140}}{{cite web |author1=Jonathan C. Allan |author2=Ron Geitgey |author3=Roger Hart |title=Dynamic Revetments for Coastal Erosion in Oregon Final Report SPR 620 |publisher=Oregon Department of Transportation Research Unit |date=August 2005 |url=https://www.oregon.gov/ODOT/Programs/ResearchDocuments/DynamicRevetments.pdf}}
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Tetrapods
File:MumbaiCaltroplikeSeashoreDefence.JPG]]
{{main|Tetrapod (structure)}}
In coastal engineering, a tetrapod is a four-legged concrete structure used as armour unit on breakwaters. The tetrapod's shape is designed to dissipate the force of incoming waves by allowing water to flow around rather than against it, and to reduce displacement by allowing a random distribution of tetrapods to mutually interlock.
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Fortifications
File:Trench construction diagram 1914.png: British diagram for the construction of revetted trenches - the revetment here is the part forward of the standing soldier.]]
According to the U.S. National Park Service, and referring mostly to their employment in the American Civil War, a revetment is defined as a "retaining wall constructed to support the interior slope of a parapet. Made of logs, wood planks, fence rails, fascines, gabions, hurdles, sods, or stones, the revetment provided additional protection from enemy fire, and, most importantly, kept the interior slope nearly vertical. Stone revetments commonly survive. A few log revetments have been preserved due to high resin pine or cypress and porous sandy soils. After an entrenchment was abandoned, many log or rail revetments were scavenged for other uses, causing the interior slope to slump more quickly. An interior slope will appear more vertical if the parapet eroded with the revetment still in place."{{cite web
|author=U.S. National Park Service
|title=Military Earthworks Terms
|url=http://www.cr.nps.gov/HPS/hli/currents/earthworks/glossaryQ_Z.htm
|access-date=2009-05-25
|archive-date=2012-10-20
|archive-url=https://web.archive.org/web/20121020231124/http://www.cr.nps.gov/HPS/hli/currents/earthworks/glossaryQ_Z.htm
|url-status=dead
}}
See also
- {{annotated link|Revetment (aircraft)}}
- {{annotated link|Riparian zone}}
- {{annotated link|Riparian-zone restoration}}
- {{annotated link|Seawall}}
- {{annotated link|Riprap}}
References
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External links
{{Commons category}}
=River and levee management=
- [http://www.epa.gov/owow/showcase/whiteriver/river_bend/riverbend.html EPA - River Bend Project]
- [https://web.archive.org/web/20021231051820/http://dnr.metrokc.gov/wlr/flood/maintenance.html Levee and Revetment Routine Maintenance]
- [https://www.fhwa.dot.gov/engineering/hydraulics/pubs/hec/hec11si.pdf US DOT - Design of Riprap Revetment]
{{coastal management|state=expanded}}
{{Rivers, streams and springs}}
Category:Architectural elements
Category:Environmental engineering
Category:Ecological restoration