Science Fair Project Encyclopedia
A dyke (or dike) is a stone or earthen wall constructed as a defence or as a boundary. The best known form of dyke is a construction built along the edge of a body of water to prevent it from flooding onto an adjacent lowland. However dykes have also been built as field boundaries and as military defences. More on this type of dyke can be found in the article on dry-stone dykes.
Dykes can be permanent earthworks or emergency constructions (often of sandbags) built hastily in a flood emergency. Also dykes were built to reclaim land from the sea. For instance, the Zuiderzee Works (North Sea Reclamation Works) in the Netherlands are an immense series of dykes built primarily to shorten the coast line and make it safer. This dyke sytem goes further to the east and north via nearly the whole German coast up to Esbjerg in Denmark. The estuaries of the flatland rivers Rhine, Elbe, Ems, Weser and Eider are also protected from storm tides by dykes, which can be more than 9 m high.
The Netherlands also has some 13,000 km of boezem dykes, secondary dykes typically of 1.5 - 4 m high, and essential to the continued drainage of reclaimed land. The dykes are typically merely simple earth embankments, though 20% are constructed from peat; two collapses of boezem dykes in 2003 have prompted urgent investigation of the entire network.
The city of Richmond, British Columbia in Canada is an island of 129.666 km2 at the delta of the Fraser River protected by a system of dykes. The first dykes were created by individual farmers in 1861 to reclaim land. Pumps are still used to this day to keep water out, and there are still uncovered ditches throughout much of Richmond. Many of the ditches are being replaced with pipes with sidewalks on top.
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