River island

A small, inceptive, river island at Sihoť, Bratislava, Slovakia

Satellite picture of Csepel Island in Hungary which is south of Budapest city centre

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.

These islands result from changes in the course of a river. Such changes may be caused by interactions with a tributary, or by the opposing fluvial actions of deposition and/or erosion that form a natural cut and meander. Nascent vegetation-free shoals and mudflats may dissipate and shift or build up into such islands through deposition; the process may be assisted through artificial reinforcement or natural factors, such as reeds, palms, evergreen trees or willows, that act as obstacles or erosion barriers, so that water flows around them. Islands may be small or large, 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[]

Friday Island is an example of a very small island with a solid-foundations house

Majuli, in the Brahmaputra River in India, a non-coastal land mass between two channels of one river, is recognised by the Guinness Book of World Records as the world's largest river island, at 880 km (340 miles).^[1] Britannica cites another large land mass, Ilha do Bananal, in Tocantin, central Brazil, as an island that divides the Araguaia River into two branches over a 320 km (200-mile) length of water.^[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.^{[citation needed]} 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 exist, containing houses constructed of permanent materials. Canals reduce erosion of the islands and in particular limit the height of flash flooding by maintaining substantial "heads" of water through barrages.^{[citation needed]} One-home islands improved by river canals include Monkey, Friday, Holm and D'Oyly Carte islands.

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.

This list is incomplete; you can help by . (February 2011)

See also[]

Notes[]

References[]