Based on questionnaire data provided to the U.S. Army Corps of Engineers districts comprising the coastal and Great Lakes regions of the United States contain approximately 11500 navigation and shore protection structures (Table 1). However, it is generally expensive and causes beaches to disappear.For a complete version of this document click here. Seawalls protect inland residential, commercial and industrial properties and roads, so they're generally built using reinforced concrete, boulders, large biodegradable sandbags, gabions, steel, and other materials.Ī seawall is considered a long-term solution against erosion and can be used for recreation and sightseeing. It deflects the waves and is ready to act as a coastal defense against tidal movements, too. Like the breakwater, the seawall is fully prepared to absorb the force of the currents and swells. Jetties also protect the coastline from tides, currents, and swells and defend the shore from erosion.Ī seawall is a large barrier built along the shoreline to protect coastal communities against flooding and mitigate the effects of erosion. It is often built on either side of a river mouth to keep the navigation channel open. The only difference between jetties and groins is the extension of the structure.Ī jetty is usually longer and narrower than a groin and is not part of a series. Groins are usually made from concrete, wood, or stone, and the spacing between them is determined according to local beach slope and wave energy patterns.Ī jetty is a robust man-made structure that completely redirects or interrupts the longshore current and accumulates sand on the updrift side. Unlike the breakwater, which generates calm water basins, groins are not constructed to create harbors and do not provide shelter to fishing boats, yachts, and vessels. It is built in series that work together to catch sediments in the surf zone brought by longshore drift. They can be a useful tool to prevent beach erosion, but breakwaters also have unintended negative consequences.Ī breakwater may be floating offshore or fixed, and it is traditionally built using large granite rocks that can handle the impact and the energy of the waves.Ī groin is a medium-sized artificial structure built perpendicular to the shoreline. Let's take a look at each one of these artificial marine barriers: The BreakwaterĪ breakwater is a human-made structure built out into the sea with the purpose of creating a safe harbor, marina, or anchorage for fishing vessels and protecting the coast from powerful swells and waves.īreakwaters are often constructed near the coast - parallel or perpendicularly - and may be part of a larger coastal management plan.īecause they're physical obstacles, they tend to trap sediments - sand, small rocks, algae - and even some marine life species. In the US, four states have prohibited the construction of coastal defense structures: North Carolina, South Carolina, Maine, and Rhode Island. So, they have both pros and cons.Īs a result, the adoption of shoreline armoring practices is often controversial and not always unanimous. What have they got in common? They're all artificial shoreline stabilization structures built to protect inland human constructions and fight erosion.īreakwaters, groins, jetties, and seawalls have a significant impact on the shoreline and can even incidentally create, improve or destroy surf breaks and surfing waves.Īll these human-made mechanisms shape the coastline and alter the behavior and movement of sand and sediments. Discover the differences and similarities between breakwaters, groins, jetties, and seawalls.
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