For the more information about the geologic resources of the National Park Service, please visit http://www.nature.nps.gov/geology/.


Hard Engineering

Seawall at Golden Gate National Recreation Area (NPS photo)
Seawall at Golden Gate National Recreation Area (NPS photo)

Hard structures are often placed in coastal environments to counteract erosion in sediment-deficient areas, or to deter accretion in dynamic areas such as inlets. Hard engineering includes breakwaters, seawalls, revetments, jetties, and groins. Unfortunately, these anthropogenic modifications usually increase erosion in downdrift areas, increasing the necessity for additional shoreline stabilization efforts. The creation of new hard structures is currently banned in many states, or strongly discouraged in coastal management practices.

Groins are shore perpendicular structures, used to maintain updrift beaches or to restrict longshore sediment transport. Jetties are another type of shore perpendicular structure and are placed adjacent to tidal inlets to control inlet migration and minimize sediment deposition within the inlet.

Shore parallel structures (seawalls, bulkheads and revetments) are designed to protect coastal property. However, seawalls may accelerate erosion on the beaches fronting the properties because wave energy can be reflected off the seawall. The increased wave energy and the sediment trapped behind the seawall often decrease the sediment supply near the seawall, causing erosion on adjacent beaches. Therefore, alternatives to these hard structures are strongly encouraged and actively sought by the NPS.

Other anthropogenic structures that are used to stop or alter natural coastal changes include breakwaters, headlands, sills, and reefs. These structures are composed of either natural or artificial materials, and are designed to alter the effects of waves and slow coastline erosion. Submerged reefs and sills dampen wave energy and may increase local fisheries due the creation of new habitat. However, the long-term effects of these structures, on both physical and biological processes, must be thoroughly examined.


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Last Updated: August 16, 2011