A submersible bridge is a type of movable bridge that lowers the bridge deck below the water level to permit waterborne traffic to use the waterway. This differs from a lift bridge

Lift bridge

A vertical-lift bridge or lift bridge is a type of movable bridge in which a span rises vertically while remaining parallel with the deck....

 or table bridge

Table bridge

A table bridge is a moveable bridge in which the deck moves along the vertical axis. Hydraulic pillars under the bridge raise the bridge deck to allow barge traffic to pass beneath it. In contrast to a lift bridge, where the deck is pulled upwards along towers, the deck of a table bridge is pushed...

, which operate by raising the roadway. Two submersible bridges exist across the Corinth Canal

Corinth Canal

The Corinth Canal is a canal that connects the Gulf of Corinth with the Saronic Gulf in the Aegean Sea. It cuts through the narrow Isthmus of Corinth and separates the Peloponnesian peninsula from the Greek mainland, thus effectively making the former an island. The builders dug the canal through...

, one at each end, in Isthmia

Isthmia

Isthmia is a noun meaning "of the isthmus"It may refer to:* The ancient Isthmian Games* The archaeological site related to the Games, including the Temple of Poseidon at Isthmia* The modern village of Isthmia...

 and Corinth

Corinth

Corinth is a city and former municipality in Corinthia, Peloponnese, Greece. Since the 2011 local government reform it is part of the municipality Corinth, of which it is the seat and a municipal unit...

. They lower the centre span to 8 metres below water level when they give way to ships crossing the channel.

The submersible bridge's primary advantage over the similar lift bridge is that there is no structure above the shipping channel and thus no height limitation on ship traffic. This is particularly important for sailing vessels. Additionally, the lack of an above-deck structure is considered aesthetically pleasing, a similarity shared with the Chicago-style bascule bridge

Bascule bridge

A bascule bridge is a moveable bridge with a counterweight that continuously balances the span, or "leaf," throughout the entire upward swing in providing clearance for boat traffic....

 and the table bridge

Table bridge

A table bridge is a moveable bridge in which the deck moves along the vertical axis. Hydraulic pillars under the bridge raise the bridge deck to allow barge traffic to pass beneath it. In contrast to a lift bridge, where the deck is pulled upwards along towers, the deck of a table bridge is pushed...

. However, the presence of the submerged bridge structure limits the draft

Draft (hull)

The draft of a ship's hull is the vertical distance between the waterline and the bottom of the hull , with the thickness of the hull included; in the case of not being included the draft outline would be obtained...

 of vessels in the waterway.

The term submersible bridge is also sometimes applied to a non-movable bridge that is designed to withstand submersion and high currents when the water level rises. Such a bridge is more properly called a low water bridge

Low water crossing

A low water crossing provides a bridge when water flow is low. Under high flow conditions, water runs over the roadway and precludes vehicular traffic...

.

See also

• Moveable bridge
  Moveable bridge
  A moveable bridge is a bridge that moves to allow passage for boats or barges. An advantage of making bridges movable include lower price, due to the absence of high piers and long approaches. The principal disadvantage is that the traffic on the bridge must be halted when it is opened for passages...
  
   for a list of other moveable bridge types
• Table bridge
  Table bridge
  A table bridge is a moveable bridge in which the deck moves along the vertical axis. Hydraulic pillars under the bridge raise the bridge deck to allow barge traffic to pass beneath it. In contrast to a lift bridge, where the deck is pulled upwards along towers, the deck of a table bridge is pushed...
  
   for a similar bridge that moves upward
• Low water crossing
  Low water crossing
  A low water crossing provides a bridge when water flow is low. Under high flow conditions, water runs over the roadway and precludes vehicular traffic...
  
  for a submersible bridge that does not move at all.

External Links

• Popular Science, November 1943, "Ducking Bridge" Lowers Span To Allow Ships To Pass built in Iraq in 1943 (bottom-right hand side of page)