This refers to the construction of seawalls, jetties, offshore breakwaters and groins intended to hold shorelines in place. Although it is well understood by scientists that armoring beaches destroys beaches on a decadal time scale, this fact is still widely unrecognized by the general public or ignored by coastal developers and engineers. The demand for armoring will become even more widespread as the rate of sea-level rise and shoreline retreat increases. A few political entities (North Carolina, USA, North Sea Coast of Holland) have outlawed armoring (with moderate success) and more should be urged to do so. There are large numbers of salesmen with “unique” types of seawalls and groins (Holmberg Device) that need to be refuted.
Definitions of Shoreline Armoring Terms
- The addition of sand to a beach allowing it to widen and build out seaward.
- Groin is a structure built perpendicular to the shoreline usually of rock or metal designed to trap sand that moves in the long shore current
- Hardened beach structures
- A general term referring to groins, jetties, offshore breakwaters, sea walls, tombolos, or any other engineered
- A jetty is a hardened structure built at an inlet usually made of rock or metal designed to keep navigation channels from filling in with sediment
- Longshore drift
- Long shore drift carries sand and sediment parallel to the shore and serves as the sand source for many beaches. On the east coast of the US, the long shore current is from the north to the south.
- Offshore breakwaters
- An engineered structure placed offshore and parallel to the beach. Breakwaters mimic sandbars to cause waves to break, lessening erosion on the beach behind the breakwater, but interrupting the longshore drift.
- Shoreline armoring
- The use of groins, jetties, offshore breakwaters, sea walls, tombolos or other hardened beach structures on the shore
- Sea wall
- A sea wall is designed to protect the land from erosion particularly during storms and usually made of metal, wood, or rock. One of the most famous seawalls is the Galveston seawall in Galveston, TX built after the 1900 hurricane killed 6,000 people on the island.
- Tombolos are a special type of groin built perpendicular to the shore to trap sand, but with an end parallel to the shore designed to reduce wave energy.
Surfing in / Shoreline Armoring
A Dare County building inspector has put up “unsafe structure” notices on six oceanfront houses north of this town on Hatteras Island, NC. Most of the recent erosion seems to be in an area where owners had placed sandbags in front of the houses.
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Indonesia’s capital, Jakarta– home to 10 million people – is sinking into the sea at between 2.9 and 6.7 inches per year. To save the megacity from drowning: a $40 billion land reclamation and sea wall project estimated to take 30 years to complete. However, today, the central government has decided to suspend its implementation as the viability of the project is now questioned.
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Climate change could be the reason for conditions which have led to drastic coastal erosion at a popular Polis beach, and experts say bad weather which battered the island has caused the worst erosion witnessed for at least twenty years.
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Terminal groins are hardened structures designed to control the movement of sand and (attempt to) slow erosion on beaches.
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Sagamore Beach residents approved a mitigation project, consisting of building a revetment wall at the base of the eroding cliff, along with a stabilization system. Opponents said erosion is nature’s way of replenishing the shore. A revetment wall would block the natural flow of sand down the cliff, with the beach eventually being washed away.
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Sandbags can’t hold back the sea. Neither will a state policy allowing “terminal groins,” barriers of rock and steel that run perpendicular to the shore in a futile effort to make a shifting coastline stable.
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Salt marshes are the unsung heroes of coastal flood protection. These flat expanses of wild plants grow in muddy channels and creeks, flooded and drained by the tides. Only special types of plants can tolerate this briny environment.
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“Walls Around our Coastal Cities?” is an article from “Our Ocean Backyard- Collected Essays, ” a book by Gary Griggs.
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The South Carolina’s Supreme Court has ruled against granting a permit for a sea wall and revetment on Capt. Sam’s Spit – the wildlife-rich, 150-acre spit that is a prized piece of disappearing natural coast.
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