In modern usage, a causeway is a road or railway elevated by a bank, usually across a broad
body of wateror wetland. A transport corridor that is carried instead on a series of arches, perhaps approaching a bridge, is a viaduct. In the U.S. a short stretch of viaduct is called an overpass. The distinction between the terms "causeway" and "viaduct" becomes blurred when flood-relief culverts are incorporated, though generally a causeway refers to a roadway supported mostly by earth or stone, while a bridge supports a roadway between piers (which may be embedded in embankments). Some low causeways across shore waters become inaccessible when covered at high tide.
When first used, the word appeared in a form such as “causey way” making clear its derivation from the earlier form “causey”. This word seems to have come from the same source by two different routes. It derives ultimately, from the Latin for heel, "calx" and as near certainly as may be, comes from the trampling technique for consolidating earthworks. In antiquity, the construction was trodden down, one layer at a time, often by slaves or a flock of
sheep. Today, a machine does the job. The same technique would have been used for road embankments, raised river banks, sea banks and fortificationearthworks. (The layers, though not the trampling action, can be seen in the Bayeux Tapestry: Building Hastings Castle.)
The second derivation route is simply the hard, trodden surface of a path. The name by this route came to be applied to a firmly-surfaced road. It is now little-used except in dialect and in the names of roads which were originally notable for their solidly-made surface. The word is comparable in both meanings with the French "chaussée", from a form of which it reached English by way of Norman French. The French adjective, "chaussée", carries the meaning of having been given a hardened surface, and is used to mean either paved or shod. As a noun "chaussée" is used on the one hand for a metalled carriageway, and on the other for an embankment with or without a road. Other languages have a noun with similar dual meaning. In Welsh, it is "sarn". The Welsh is relevant here, as it also has a verb, "sarnu", meaning to trample. The trampling and ramming technique for consolidating earthworks was used in fortifications and there is a comparable, outmoded form of wall construction technique, used in such work and known as pisé, a word derived not from trampling but from ramming or tamping.
The modern embankment may be constructed within a "
cofferdam": two parallel steel sheet pileor concrete retaining walls, anchored to each other with steel cables or rods. This construction may also serve as a dyke that keeps two bodies of water apart, such as bodies with a different water level on each side, or with salt water on one side and fresh wateron the other. This may also be the primary purpose of a structure, the road providing a hardened crest for the dike, slowing erosion in the event of an overflow. It also provides access for maintenance as well perhaps, as a public service.
Notable causeways include those that connect
Singaporeand Malaysia(the Johor-Singapore Causeway), Bahrainand Saudi Arabia(25-km long King Fahd Causeway) and Veniceto the mainland, all of which carry roadways and railways. In the Netherlandsthere are a number of prominent dykes which double as causeways, including the Afsluitdijk, Brouwersdam, and Markerwaarddijk. In Louisiana, two very long bridges, called the Lake Pontchartrain Causeway, stretch across Lake Pontchartrainfor almost 38 km, making them the world's longest bridges (if total length is considered instead of span length). They are also the oldest causeways on the Gulf Coast that have never been put out of commission for an extended period of time following a Hurricane. In the Republic of Panamaa causeway connects the islands of Perico, Flamenco, and Naos to Panama Cityon the mainland. It also serves as a breakwater for ships entering the Panama Canal. The oldest engineered road yet discovered is the Sweet Trackin England, dating from the 3800s BC.
Causeways are also common in
Florida, where low bridges may connect several man-made islands, often with a much higher bridge (or part of a single bridge) in the middle so that taller boats may pass underneath safely. Causeways are most often used to connect the barrier islands with the mainland.
Churchill Barriersin Orkneyare of the most notable sets of causeways in Europe. Constructed in waters up to 18 metres deep, the four barriers link five islands on the eastern side of the natural harbour at Scapa Flow. They were built during World War IIas military defences for the harbour, on the orders of Winston Churchill.
Causeways affect currents and may therefore be involved in beach
erosionor changed deposition patterns. This, for instance, has been a problem at the Hindenburgdammin northern Germany. Causeways are often a problem with an approaching hurricaneor strong tropical storm, because the high winds and waves make them dangerous. Along with traffic jams, this is a major reason for the early emergency evacuationof islandresidents during a weather emergency.
The Causeway, Western Australia
Causey Arch, County Durham, England
* Oxford English Dictionary. 1971. ISBN 0-19-861212-5.
* Collins Robert French Dictionary, 5th edn. 1998. ISBN 0-00-470526-2.
* Nouveau Petit Larousse Illustré, Paris. 1934.
* Grape, W. The Bayeux Tapestry. Prestel, Munich and New York. 1994. ISBN 3-7913-1365-7.
* Evans, H.M. and Thomas, W.O. The New Welsh Dictionary (Y Geiriadur Newydd). Llyfrau'r Dryw, Llandybie. 1953.
Causeways around the world
Various causeways in the world:
Canso Causeway, Nova Scotia, Canada(coord|45.6443|-61.4184|type:landmark)
Lake Ponchartrain, Louisiana(coord|30.1974|-90.1205|type:landmark)
Bahrain, Saudi Arabia(coord|26.1841|50.3241|type:landmark)
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