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 sandbars 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.
|Look up towhead in Wiktionary, the free dictionary.|
The term "towhead" implies a little islet or sandbar 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.
Largest and smallest
Majuli 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., but Ilha do Bananal meets the same qualifications and is much larger. Umananda is among contenders as the smallest permanently-inhabited river island with fixed dwellings at 0.02 km². Majuli and Umananda lie in the Brahmaputra River. Many as tiny as Umananda or smaller, inhabited, exist in the Amazon basin and Bangladesh. 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
|Montreal||1,854,442||499||Canada||Montreal||St. Lawrence River|
|Manhattan Island||1,634,795 (2008)||59||United States||New York City||Hudson River/East River|
|Chongming Island||660,000 (2010)||1,267||China||Shanghai||Yangtze River|
|Ile Jesus||401,550||242||Canada||Laval||St. Lawrence River|
|Veľký Žitný ostrov||226,446 (2001)||1,885||Slovakia||several||Danube|
|Vasilievsky Island||202,650 (2002)||10.9||Russia||St. Petersburg||Bolshaya Neva/Malaya Neva|
|Csepel Island||166,953 (2012)||257||Hungary||diverse||Danube|
|Majuli||140,000||422||India||Vaishnavite Shrines||Brahmaputra River|
|Yeouido||30,988 (2006)||8.4||South Korea||Seoul||Han River|
- 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.
- Majuli, River Island. "Largest river island". Guinness World Records. Retrieved 6 September 2016.
- "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.
- Historical Dictionary of Pyongyang, by Justin Corfield, p.227