Armoring structures are typically large, impermeable edifices designed to protect the shore from flooding, wave attack, and erosion. They include seawalls, bulkheads, and revetments.
A seawall is usually a massive concrete structure with its weight providing stability against sliding forces and overturning. Seawalls are termed non-energy absorbing when they are vertical; however, those with a sloping surface or composed of rubble mound may absorb some wave energy. The front face may also be curved or stepped to deflect wave run-up.
A bulkhead is a vertical retaining wall that holds soil in place and prevents it from sliding into the sea. A secondary purpose is to protect the land from wave attack. For eroding bluffs and cliffs, bulkheads increase stability by protecting the toe from undercutting. They are often constructed of steel sheet pile that is driven into the ground or anchored, or they can consist of rock-filled timber cribs and gabions.
Revetments are a cover or facing of erosion-resistant material placed directly on an existing slope, embankment, or dike to protect the area from strong waves and currents. Three major features are a stable armor layer, a filter cloth or underlayer, and toe protection. The filter and underlayer support the armor yet allow for passage of water through the structure. Riprap and quarrystone designs can tolerate some movement and remain functional, while concrete or asphalt slabs are unable to tolerate settling.
By creating a fixed point along naturally dynamic shorelines, armoring structures make beach erosion more noticeable, although they don't necessarily aggravate it. In certain situations, however, armoring structures can increase erosional stress on adjacent beaches by blocking cross-shore and longshore sediment transport. For this reason, armoring responses are frequently combined with other shore protection alternatives.
Reviewed 18 Jan 2013
Galveston Sea Wall
A concrete seawall has been protecting Galveston, Texas, since 1902. A response to a deadly hurricane in 1900, this structure has saved many lives and millions of dollars since it was built.