A levee ( or ), is an elevated ridge alongside the banks of a river, often intended to protect against flooding of the area adjoining the river. Alternatively, it is called a dike (American English), dyke (Commonwealth English), floodbank, or stop bank. It is a type of embankment. A levee, natural or artificial, is usually earthen and often runs parallel to the course of a river in its floodplain or along low-lying coastlines. Naturally occurring levees form on river floodplains following flooding. Sediment and alluvium are deposited on the banks and settle, forming a ridge that increases the river channel's capacity. The levee's shape is due to the coarser load of the river immediately depositing adjacent to the channel as the water loses velocity during flooding, with progressively finer sediments settling further on the floodplain on each side of the channel, creating a gentle slope on each side of the U-shaped channel. Alternatively, levees can be artificially constructed from fill, designed to regulate water levels. In some circumstances, artificial levees can be environmentally damaging. Ancient civilizations in the Indus Valley, ancient Egypt, Mesopotamia and China all built levees. Today, levees can be found around the world, and failures of levees due to erosion or other causes can be major disasters, such as the catastrophic 2005 levee failures in Greater New Orleans that occurred as a result of Hurricane Katrina.
Etymology The word levee, favoured by speakers of American English, comes from the French word levée (from the feminine past participle of the French verb lever, 'to raise'). It is attested in New Orleans a few years after the city's founding in 1718 and was later adopted by English speakers. The Latin levata (feminine past participle of levare) is first used in the sense of levee in a document of 954 referring to a millpond near Bagnolo di Po created by a levee which had a road running over it. The verb levare was used in the sense of diverting water for a mill as early as 778, when Duke Hildeprand of Spoleto granted a canal to Bishop Guicpert of Rieti for the construction of a mill. The name derives from the trait of the levee's ridges being raised higher than both the channel and the surrounding floodplains. The modern word dike or dyke most likely derives from the Dutch word dijk, with the construction of dikes well attested as early as the 11th century. The 126-kilometer-long (78 mi) Westfriese Omringdijk, completed by 1250, was formed by connecting existing older dikes. The Roman chronicler Tacitus mentions that the rebellious Batavi pierced dikes to flood their land and to protect their retreat (70 CE). The word dijk originally indicated both the trench and the bank. It closely parallels the English verb to dig. In Anglo-Saxon, the word dic already existed and was pronounced as dick in northern England and as ditch in the south. Similar to Dutch, the English origins of the word lie in digging a trench and forming the upcast soil into a bank alongside it. This practice has meant that the name may be given to either the excavation or to the bank. Thus Offa's Dyke is a combined structure and Car Dyke is a trench – though it once had raised banks as well. In the English Midlands and East Anglia, a dike is what a ditch is in the south of England, a property-boundary marker or drainage channel. Where it carries a stream, it may be called a running dike as in Rippingale Running Dike, which leads water from the catchwater drain, Car Dyke, to the South Forty Foot Drain in Lincolnshire (TF1427). The Weir Dike is a soak dike in Bourne North Fen, near Twenty and alongside the River Glen, Lincolnshire. In the Norfolk and Suffolk Broads, a dyke may be a drainage ditch or a narrow artificial channel off a river or broad for access or mooring, some longer dykes being named, e.g., Candle Dyke. In parts of Britain, particularly Scotland and Northern England, a dyke may be a field wall, generally made with dry stone.
Uses
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