|This article's factual accuracy is disputed. (May 2013)|
||This article includes a list of references, related reading or external links, but its sources remain unclear because it lacks inline citations. (April 2013)|
|Ancestor||None. (See Ford (crossing))|
|Related||None. (See step-stone bridge)|
|Descendant||None. (See viaduct)|
|Material||Concrete, masonry, Earth-fill|
A causeway is a road or railway route across a broad body of water or wetland raised up on an embankment. Some causeways may only be usable at low tide and the distinction between causeways and viaducts can become blurred when flood-relief culverts are incorporated in the structure; a causeway is however primarily supported on earth or stone, whereas a bridge or viaduct is mainly supported by free-standing columns or arches.
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 most likely comes from the trampling technique to consolidate earthworks. In Ancient times, the construction was trodden down, one layer at a time, often by slaves or flocks of sheep. Today, this work is done by machines. The same technique would have been used for road embankments, raised river banks, sea banks and fortification earthworks. (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 pile or 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 water on 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 Singapore and Malaysia (the Johor–Singapore Causeway), Bahrain and Saudi Arabia (25-km long King Fahd Causeway) and Venice to the mainland, all of which carry roadways and railways. In the Netherlands there are a number of prominent dykes which also double as causeways, including the Afsluitdijk, Brouwersdam, and Markerwaarddijk. In Louisiana, two very long bridges, called the Lake Pontchartrain Causeway, stretch across Lake Pontchartrain for 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 Panama a causeway connects the islands of Perico, Flamenco, and Naos to Panama City on the mainland. It also serves as a breakwater for ships entering the Panama Canal. Its English name causeway is sometimes confused with "Coastway", name of a touristic zone in Panama city. The Aztec city-state of Tenochtitlan had causeways supporting roads and aqueducts. The oldest engineered road yet discovered is the Sweet Track in 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.
The Churchill Barriers in Orkney are 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 II as military defences for the harbour, on the orders of Winston Churchill.
The Estrada do Istmo connecting the islands of Taipa and Coloane in Macau was initially built as a causeway. The sea on both sides of the causeway had become shallower as a result of silting, and mangroves had conquer the area. Later on land reclamation took place on both sides of the road and the area has subsequently be named Cotai and become home of several casino complexes. In Okinawa, Japan, connected by the Mid-Sea Road are the Katsuren Peninsula, Henza Island, Miyagi Island, Ikei Island and Hamahiga-Island.
Specific causeways around the world
|This section requires expansion. (April 2009)|
Various causeways in the world:
- Canso Causeway, Nova Scotia, Canada ( )
- Colaba Causeway, Mumbai, India ( )
- Hindenburgdamm, Germany ( )
- Johor-Singapore Causeway ( )
- King Fahd Causeway, Bahrain, Saudi Arabia ( )
- Lake Ponchartrain Causeway, Louisiana ( )
- MacArthur Causeway, Florida, United States
- Mahim Causeway, Mumbai, India
- Rømødæmningen, Denmark, connecting Rømø (island) with the mainland across the wadden sea
- Swarkestone causeway, Derby, England, United Kingdom
- Ponte della Libertà, connecting Venice to the continent ( )
- Causeway across Haraldssund, Faroe Islands
- Causeway across Hvannasund, Faroe Islands
Causeways affect currents and may therefore be involved in beach erosion or changed deposition patterns; this effect has been a problem at the Hindenburgdamm in northern Germany. During hurricane seasons, the winds and rains of approaching tropical storms--as well as waves generated by the storm in the surrounding bodies of water—make traversing causeways problematic at best and impossibly dangerous during the fiercest parts of the storms. For this reason (and related reasons, such as the need to minimize traffic jams on both the roads approaching the causeway and the causeway itself), emergency evacuation of island residents is a high priority for local, regional, and even national authorities.
- The Causeway, Western Australia
- Causey Arch, County Durham, England
- Lake Pontchartrain Causeway, Metairie, Louisiana, Southern; Mandeville, Louisiana, Northern.
- Pulaski Skyway
- 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.