Blocking the Tide

by Donald R. F. Harleman, Ford Prof. of Envir. Engrg. Emeritus; Dept. of Civ. and Envir. Engrg., Massachusetts Inst. of Tech., Cambridge, MA,
Rafael L. Bras, Bacardi and Stockholm Foundations Prof. and Head; Dept. of Civ. and Envir. Engrg. Massachusetts Inst. of Tech., Cambridge, MA,
Andrea Rinaldo, Prof. of Civ. Engrg.; G. Poleni Inst. of Hydr., Univ. of Padua, Italy,
Paola Malanotte, Prof. of Physical Oceanography; Dept. of Earth, Atmospheric, and Planetary Sciences, Massachusetts Inst. of Tech., Cambridge, MA,

Serial Information: Civil Engineering—ASCE, 2000, Vol. 70, Issue 10, Pg. 52-57

Document Type: Feature article


The city of Venice is in peril as a result of increased tidal flooding, and a proposed system of movable gates offers the greatest promise of safeguarding the city's future. The proposed gates are unique in that they are raised and lowered by buoyancy. According to the preliminary design, each gate module consists of a parallel-piped steel caisson 20 m wide and between 20 and 30 m long depending on the depth of the inlet. The gate modules are hollow with internal steel bracing; their thickness is between 3 and 5 m and they range from 200 to more than 3000 Mg in weight. In its open position, the gate module is filled with water and rests horizontally in a recess in a concrete foundation structure. Each gate is connected to the foundation structure by a horizontal hinge at its seaward end. The gates can be raised in about a half an hour by introducing compressed air, expelling water, and causing the gate to rotate upward on its hinge to an angle of 40 to 50 degrees to the horizontal.

Subject Headings: Gates (hydraulic) | Tides | Steel | Hinges | Foundations | Urban areas | Thickness

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