Movable flood barriers

Low-lying coastal and riverside areas face periodic flooding from storm surges and high tides. Permanent walls would block navigation and access.

Large mechanical gates or barriers are normally open to allow river flow and shipping, but close when storm surges or high tides threaten. Closure decisions are based on forecast data.

Steel or concrete gates, hydraulic operating machinery, control rooms, backup power systems

Tide level sensors, surge forecasting models, structural condition monitoring

Protects large areas when needed; allows normal river use when open; can be designed for extreme events

Very expensive to build and maintain; mechanical systems can fail; increasing closure frequency from sea level rise reduces maintenance windows

Operational scenarios where this pattern is applied:

• Operate flood defences during events —

Real-world examples of this pattern in action: