![]() Levees can be permanent earthworks or emergency constructions (often of sandbags) built hastily in a flood emergency. More on this type of levee can be found in the article on dry-stone walls. Levees have also been built as field boundaries and as military defences. The latter can be a controlled inundation by the military or a measure to prevent inundation of a larger area surrounded by levees. Furthermore, levees have been built for the purpose of empoldering, or as a boundary for an inundation area. Levees can be mainly found along the sea, where dunes are not strong enough, along rivers for protection against high-floods, along lakes or along polders. The main purpose of artificial levees is to prevent flooding of the adjoining countryside and to slow natural course changes in a waterway to provide reliable shipping lanes for maritime commerce over time they also confine the flow of the river, resulting in higher and faster water flow. In parts of Britain, particularly Scotland and Northern England, a dyke may be a field wall, generally made with dry stone. 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. The Weir Dike is a soak dike in Bourne North Fen, near Twenty and alongside the River Glen, Lincolnshire. 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). In the English Midlands and East Anglia, and in the United States, a dike is what a ditch is in the south of England, a property-boundary marker or drainage channel. Thus Offa's Dyke is a combined structure and Car Dyke is a trench – though it once had raised banks as well. This practice has meant that the name may be given to either the excavation or to the bank. Similar to Dutch, the English origins of the word lie in digging a trench and forming the upcast soil into a bank alongside it. In Anglo-Saxon, the word dic already existed and was pronounced as dick in northern England and as ditch in the south. It closely parallels the English verb to dig. The word dijk originally indicated both the trench and the bank. The Roman chronicler Tacitus mentions that the rebellious Batavi pierced dikes to flood their land and to protect their retreat (70 CE). The 126-kilometre-long (78 mi) Westfriese Omringdijk, completed by 1250, was formed by connecting existing older dikes. The modern word dike or dyke most likely derives from the Dutch word dijk, with the construction of dikes in Frisia (now part of the Netherlands and Germany) well attested as early as the 11th century. The name derives from the trait of the levee's ridges being raised higher than both the channel and the surrounding floodplains. It originated in New Orleans a few years after the city's founding in 1718 and was later adopted by English speakers. Speakers of American English (notably in the Midwest and Deep South) use the word levee, from the French word levée (from the feminine past participle of the French verb lever, 'to raise'). ![]()
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