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
Officials are temporarily scaling back their ambitions for a massive sand berms program that was designed to block oil from hitting coastal marshes but that continues to draw federal opposition.
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Recent events in Tofino, Canada, remind us that a beach is dynamic in nature and ever evolving.
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Critics and supporters of building sand berms to shield Louisiana’s coast from the Gulf of Mexico oil spill have released dueling photo sequences.
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Of the many cleanup solutions being pursued in the Gulf of Mexico, few are as ambitious as Louisiana’s berm project.
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While the use of hardened beach structures are debated, there is little debate over what they do beaches over time.
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North Carolina law has prohibited hardened structures on its beaches and inlets for more than two decades.
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Sand bags are used to stabilize buildings that are threatened by the ocean.
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The negative impact of groins on downdrift shorelines is well understood.
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