Boom (navigational barrier)
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A boom or a chain is an obstacle strung across a navigable stretch of water to control or block navigation. They are sometimes mixed with pile barrages.
A boom blocking the River Foyle during the siege of Derry
Crusaders break a chain protecting the harbour (at left) in the siege of Damietta.
Boom towers in Norwich
Remains of the great chain that protected the Golden Horn
Pile barrage
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Pile barrages, among other names, are underwater barricades or barrages used for coastal military defence. They are constructed with piles, vertical poles or stakes driven into the bed of a body of wa
Boom (navigational barrier)
…boom, boom chain or variants) is an obstacle strung across a navigable stretch of water to control or block navigation. They are sometimes mixed with pile barrages. In modern times they usually have civil uses, such as to prevent access to a dangerous river channel. But, especially historically, they have been…
Pile barrage of the Shoeburyness Boom, United Kingdom
Close-up of a pile barrage from the Shoeburyness Boom, United Kingdom
Part of Stockholm's old "city pile wall" on Vädersolstavlan (1535)
The Stockholm pile driver operating on ice, from Olaus Magnus' A Description of the Northern Peoples (1555).