River island
A river island is any exposed land surrounded by river water. Properly defined it excludes shoals between seasonally varying flows and may exclude semi-coastal islands such as in deltas.
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These islands result from changes in the course of a river such as interactions with a tributary or the opposing fluvial actions of deposition and/or erosion such as forming a natural cut and meander. Nascent vegetation-free shoals and mudflats may dissipate and shift or build up into such islands through deposition and which may be assisted through artificial reinforcement or natural factors such as, reeds, palms, evergreen trees or willows, to large examples covering many square kilometers, examples of which are given below.
Regional nomenclature
 |
Look up towhead in Wiktionary, the free dictionary. |
The term "towhead" implies an islet (small island) or shoal within a river (most often the Mississippi River) having a grouping or thicket of trees, and is often used in the Midwestern United States. Many rivers, if wide enough, can house considerably large islands. The term "towhead" was popularised by Mark Twain's Adventures of Huckleberry Finn.
In England, a river island in the Thames is referred to as an "ait" (or "eyot").
Largest and smallest
Majuli, in the Brahmaputra River in India, being non-coastal and being between two channels of one river, is recognised by the Guinness Book of World Records as world's largest example,[1] but Ilha do Bananal meets the same qualifications and is much larger.[2]
Umananda, at 0.02 square kilometres (0.0077 sq mi), is among contenders as the smallest permanently-inhabited river island, or islet, with fixed dwellings. Umananda also lies in the Brahmaputra River. Many as tiny as Umananda or smaller, inhabited, exist in the Amazon basin and Bangladesh. Another island of comparable size to Umananda, Hatfield Island in the Guyandotte River in the US state of West Virginia, has no permanent population, but contains several permanent buildings, namely the K–12 schools serving the city of Logan and its surrounding area plus the main branch of the Logan County public library.[3]
On canalised rivers such as the Thames and the Seine one-home islands of permanent-materials homes exist such as Monkey, Friday, Holm and D'Oyly Carte islands, as canalisation reduces the erosion of the islands and in particular limits the height of flash flooding by maintaining substantial "heads" of water through barrages.
Lists of river islands
- Note: Includes some river islands that also have an ocean coast.
Most populous river islands
This list ranks river islands with a population of at least 25,000.
See also
- Ait – Islands found on the River Thames and its tributaries in England
- Anabranch – A section of a river or stream that diverts from the main channel and rejoins it downstream.
- Archipelago – A group of islands
- Distributary – River branching off from main river
- Fluvial landforms – Processes associated with rivers and streams
- Island – Any piece of sub-continental land that is surrounded by water
- Lake island – Island located in a lake
- Point bar – A depositional feature of alluvium that accumulates on the inside bend of streams and rivers below the slip-off slope
- River bifurcation
- River delta – Silt deposition landform at the mouth of a river
Notes
- Due to redirecting of water from the Rangitata River, the river's southern distributary channel is now dry except after heavy rain or snow melt. As such, Rangitata Island is usually connected to the South Island mainland.
- The listed population is that of the New York City borough of Manhattan. Almost all of the borough's population lives on the island of Manhattan, but the borough also includes the following permanently populated areas:
- Marble Hill, a neighborhood with a population of roughly 10,000 that was originally part of Manhattan Island, but was physically separated from the rest of the island by the opening of a canal in 1894 and in turn physically connected to the US mainland by landfill in 1914.
- Randalls and Wards Islands, the collective name for three conjoined islands with about 1,600 residents, all either patients or staff of psychiatric hospitals, or occupants of homeless shelters.
- Roosevelt Island, located in the East River between Manhattan Island and Queens, with a population of nearly 12,000.
References
- Majuli, River Island. "Largest river island". Guinness World Records. Retrieved 6 September 2016.
- larger, Ilha do Bananal. "Bananal Island". Brittanica. Retrieved 5 August 2020.
- Spence, Robert Y. (February 21, 2012). "Hatfield Island". The West Virginia Encyclopedia. Retrieved June 12, 2020.
- "Río Grande de la Magdalena - Colección Ecológica del Banco". Retrieved 3 January 2015.
- "Žitný ostrov". Retrieved 3 January 2015.
- address, author,email. "崇明县". www.shanghai.gov.cn.
- "Largest Islands of Countries". Retrieved 3 January 2015.
- "Malebo Pool". Encyclopædia Britannica. Accessed June 2017.
- "SUMMARY REPORT ROBERTS ISLAND AND UNION ISLAND RIPARIAN WATER RIGHTS INVESTIGATION, SAN JOAQUIN COUNTY, CA, JUNE 2008" (PDF).
- W. Francis (1906). Gazetteer of South India. p. 199.
- Shivanasamudra
- Historical Dictionary of Pyongyang, by Justin Corfield, p.227
- "2016 Census Profile - Montréal, Territoire équivalent (Census division)". Statistics Canada. Retrieved 2017-03-23.
- "U.S. Census Bureau QuickFacts: New York County (Manhattan Borough), New York; United States". www.census.gov. Retrieved 2019-09-12.
- "2016 Census Profile - Laval, Territoire équivalent (Census division)". Statistics Canada. Retrieved 2019-09-11.
- "2016 Census Profile - Richmond (Census division)". Statistics Canada. Retrieved 2019-09-11.