View source for Navigable aqueduct

{{Short description|Man-made channel for water and transport}}
{{Distinguish|Aqueduct (water supply)|Aqueduct (bridge)}}
{{more citations needed|date=May 2021}}
[[File:pontcysyllte aqueduct arp.jpg|thumb|right|[[Narrowboat]] crossing the World Heritage [[Pontcysyllte Aqueduct]] in Wales]]<!--This is the only picture that actually shows a *boat* navigating...-->

'''Navigable aqueducts''' (sometimes called '''navigable water bridges''') are bridge structures that carry [[navigable]] [[waterway]] [[canal]]s over other rivers, valleys, railways or roads. They are primarily distinguished by their size, carrying a larger cross-section of water than most water-supply [[Aqueduct (water supply)|aqueducts]]. Roman aqueducts were used to transport water and were created in Ancient Rome. The {{Convert|662|m||abbr=|adj=on}} long [[steel]] [[Briare aqueduct]] carrying the [[Canal latéral à la Loire]] over the River [[Loire]] was built in 1896. It was ranked as the longest navigable aqueduct in the world for more than a century, until the [[Magdeburg Water Bridge]] in Germany took the title in the early 21st century.

Early aqueducts such as the three on the [[Canal du Midi]] had stone or brick arches, the longest span being {{Convert|18.3|m||abbr=}} on the [[Cesse Aqueduct]], built in 1690. But, the weight of the construction to support the trough with the clay or other lining to make it waterproof made these structures clumsy. In 1796 [[Longdon-on-Tern Aqueduct]], the first large [[cast iron]] aqueduct was built by [[Thomas Telford]] at [[Longdon-on-Tern]] on the [[Shrewsbury Canal]]. It has a total length of {{Convert|57|m||abbr=}} across three intermediate piers. Within ten years Telford had completed the far more ambitious [[Pontcysyllte Aqueduct]] in Wales on the [[Llangollen Canal]] over the [[River Dee, Wales|River Dee]] valley, with a total length 307 metres and a height of 38 metres, making it the tallest navigable aqueduct in the world. Other cast-iron aqueducts followed, such as the single-span [[Stanley Ferry Aqueduct]] on the [[Calder and Hebble Navigation]] in 1839, with its innovative {{Convert|50|m||abbr=|adj=on}} [[through arch bridge|through arch]] design.

There were 32 navigable aqueducts on the [[Erie Canal]], constructed 1817–1825 in [[New York State]], United States.

==Notable navigable aqueducts==
[[File:Longden-on-Tern1.jpg|thumb|Out-of-use cast-iron [[Longdon-on-Tern Aqueduct]]]]
* [[Benjamin Outram]]'s {{Convert|44|ft||long|abbr=on|adj=mid}} single-span Holmes Aqueduct on the [[Derby Canal]] in [[Derby]] was the world's first navigable [[cast iron]] aqueduct, narrowly pre-dating [[Thomas Telford]]'s {{Convert|186|ft||long|abbr=on|adj=mid}} [[Longdon-on-Tern Aqueduct]] on the [[Shrewsbury Canal]], sometimes described as the world's first ''large-scale'' navigable cast iron aqueduct.  The oldest currently navigable cast-iron aqueduct is Outram's Stakes Aqueduct on the [[Huddersfield Narrow Canal]] at [[Stalybridge]], built c1801 to replace an original, stone-built, four arch structure, which had been swept away in the floods of August 1799.
* [[Pontcysyllte Aqueduct]] ({{Convert|307|m||abbr=|disp=comma}}) carries the [[Llangollen Canal]] over the River Dee valley in north [[Wales]]; it was designed by [[Thomas Telford]], opened in 1805 and is the highest navigable aqueduct in the world. The same canal, which includes a tunnelled section, crosses a second valley on the [[Chirk Aqueduct]] (1796–1801). This navigable canal also supplies water to the former borough of [[Crewe and Nantwich]].
* The [[Union Canal (Scotland)|Union Canal]] in [[Scotland]] has many aqueducts, including the [[Slateford Aqueduct]] that takes the canal over the [[Water of Leith]], the [[Almond Aqueduct]] over the [[River Almond, Lothian|River Almond]] at [[Ratho]], and the very impressive [[Avon Aqueduct]] over the [[River Avon, Falkirk|River Avon]]. The Avon is the second-longest aqueduct in the [[United Kingdom]] ({{Convert|810|ft||abbr=|disp=comma}}).
* The [[Agen aqueduct]] (1849) in [[France]] is {{Convert|539|m||abbr=}} long and carries the [[canal de Garonne]] across the [[Garonne|Garonne River]].
* Sir [[Arthur Cotton]] planned the aqueduct at [[P. Gannavaram]], [[Andhra Pradesh]] in [[India]] to cater for the needs of farmers in the  [[Konaseema]] area while he was constructing the [[Dowleswaram Barrage|Dowleswaram barrage]]. Originally a non-navigable aqueduct was constructed in 1859 with a length of {{Convert|700|m||abbr=}}. In 2000, a new navigable aqueduct and road bridge was constructed across the [[River Vynateya]] (a tributary of the [[Godavari River]]) near Gannavaram, to facilitate the crossing of the [[Gannavaram Canal]] and also to irrigate a farming land.
* The [[Briare aqueduct]] (1896) near [[Châtillon-sur-Loire]], [[France]], carries the [[Canal latéral à la Loire]] in a steel channel over the [[Loire]] River. At {{Convert|662|m||abbr=}}, it was the longest canal aqueduct in the world for a century.
* Following construction of the [[M6 Toll|M6 Toll Motorway]] the building of the [[Lichfield Canal Aqueduct]] ran into construction difficulties. The UK parliament passed legislation preventing a road being built in the path of a canal being renovated without providing a tunnel or aqueduct for canal traffic to pass.

[[File:Trogbrücke Magdeburg.jpg|thumb|right|The Magdeburg Water Bridge seen from the shores of the [[Elbe]]]]
* [[Barton Swing Aqueduct]] is a [[swing bridge]] that carries the [[Bridgewater Canal]] across the lower [[Manchester Ship Canal]]. A {{convert|234|ft|m|abbr=on}} section of the aqueduct rotates through 90 degrees to allow vessels to pass along the Ship Canal.
* [[Veluwemeer Aqueduct]] is a 25-meter long navigable aqueduct located over [[Veluwemeer]] lake in [[Harderwijk]], Netherlands. It was opened in 2002 and bypasses the [[Provincial road N302 (Netherlands)|N302 road]].<ref>{{Cite web|url=https://interestingengineering.com/the-netherlands-unique-water-bridge|title=Meet One of the World's Most Unique Waterways: The Veluwemeer Aqueduct|date=3 April 2021}}</ref>
* An aqueduct near [[Roelofarendsveen]], [[Netherlands]] (1961) ({{Coord|52|12|55.96|N|4|37|35.46|E}}) carries the [[Ringvaart]] [[canal]] over the A4 [[highway]] and the [[HSL-Zuid]], which are situated on land below the level of the canal (and below sea level).
* Gouwe aqueduct, near [[Gouda, South Holland|Gouda]] in the [[Netherlands]], carries the [[Gouwe (river)|Gouwe]] [[river]] over the A12 highway, which is on land below the level of the river.
* The [[Naviduct|Krabbersgat naviduct]], [[Houtribdijk]] near [[Enkhuizen]], The Netherlands, is the only aqueduct in the world that also operates as a lock.
* The [[Magdeburg Water Bridge]] in [[Germany]] (2003) connects the important [[Mittellandkanal]] over the river [[Elbe]] to the [[Elbe-Havel canal]]. Nearly {{Convert|1|km||1|abbr=on}} long, it is the longest navigable aqueduct in the world.

==Gallery==
<gallery>
Boat_on_Monocacy_Aqueduct_C_and_O_Canal.jpg|Passenger (packet) boat on the Monocacy Aqueduct of the [[Chesapeake and Ohio Canal]]
Conococheague_Aqueduct_Damage_in_1920_on_C_and_O_Canal.jpg|The wall of the Conococheague Creek aqueduct collapsed when a boat hit it, shutting down navigation until repaired.
Conococheague_Aqueduct_Damage_and_Boat_on_Chesapeake_and_Ohio_canal.jpg|The captain jumped off the boat before the wall went out, dumping the boat into the creek below. There were no casualties in this accident.
Boat_entering_lock_24_Rileys_lock.jpg|The [[Seneca Aqueduct]] was a lift lock as well as an aqueduct. 
Morris_Canal_Aqueduct_over_Pompton_River_from_HABS.png|This wooden aqueduct carried the [[Morris Canal]] over the Pompton River.
</gallery>

== See also ==
{{Portal|United Kingdom|Transport}}
* [[Aqueduct (disambiguation)]]
* [[Canal]]
* [[List of canal aqueducts in Great Britain]]
* [[Viaduct]]

==References==
{{Reflist}}

{{Bridge footer}}
{{Canals of the United Kingdom}}

{{DEFAULTSORT:Navigable Aqueduct}}
[[Category:Navigable aqueducts| ]]
[[Category:Canals]]
[[Category:Bridges by structural type]]