Breakwaters

Breakwaters are coastal structures built offshore or along the shoreline to protect harbors, anchorages, and beaches from wave action. By dissipating wave energy and modifying local circulation, they create a sheltered area of calmer water behind them, reducing damage from storms and increasing the reliability of docking and loading operations.

There are several types of breakwaters. Rubble mound breakwaters use rock or rubble with an armored facing to absorb and dissipate wave energy; they are adaptable and relatively economical. Concrete breakwaters, including caisson or module-based units, provide rigid, watertight barriers and can be designed as vertical or sloping structures. Offshore breakwaters are positioned at a distance from the coast to reduce wave impact before it reaches the protected area, while shore-connected or parallel breakwaters run along the coast to shield a harbor or beach.

Design and construction depend on factors such as wave climate, water depth, sediment transport, and required navigation access. The primary goal is energy dissipation, achieved through porous or solid armor, reflection, and foundation stability. Design must account for overtopping, scour at the structure’s toe, settlement, and potential interactions with tides and currents. Materials commonly used include rock, concrete, or steel, and maintenance typically involves repair or replacement of worn armor units and dredging to restore depth where sediment deposits occur.

Environmental and coastal effects are significant considerations. Breakwaters can alter littoral transport, induce sedimentation in sheltered zones, and reduce scour elsewhere, potentially shifting erosion or accretion along adjacent shores. They also influence habitat, dredging needs, and navigation practices, and require ongoing monitoring and upkeep to remain effective.