People build various structures to prevent wave erosion, primarily focusing on altering wave action, currents, and sand movement. These structures aim to protect buildings and infrastructure built too close to eroding shorelines.
Here are some common types of structures used to combat wave erosion:
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Seawalls: These are large, robust structures built parallel to the shoreline to reflect wave energy back towards the sea. While they protect the land behind them, they can often increase erosion on adjacent beaches by reflecting wave energy.
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Groins: Groins are rigid structures built perpendicular to the shoreline, often made of wood, concrete, or rock. They trap sand moving along the coast (longshore transport), widening the beach on their up-drift side. However, they can cause erosion on the down-drift side by depriving that area of sand.
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Jetties: Similar to groins but typically larger and used to stabilize inlets and navigation channels. They prevent sand from accumulating in the channel, ensuring safe passage for boats. Like groins, they can also disrupt sand transport and cause erosion.
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Breakwaters: These structures are built offshore, parallel to the coast, to reduce wave energy reaching the shoreline. By creating a calmer area behind them, they encourage sand deposition and can protect beaches. However, the sheltered area can become a sand trap, potentially affecting sand distribution along the coast.
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Revetments: These are sloping structures placed on banks or cliffs to absorb wave energy and protect the underlying material from erosion. They are often made of rock, concrete, or interlocking blocks.
Here's a summary table:
| Structure | Description | Purpose | Potential Drawbacks |
|---|---|---|---|
| Seawalls | Parallel to the shore; reflects wave energy. | Protect land directly behind them. | Can increase erosion on adjacent beaches due to reflected wave energy. |
| Groins | Perpendicular to the shore; traps sand. | Widen the beach on the up-drift side. | Can cause erosion on the down-drift side by blocking sand transport. |
| Jetties | Similar to groins, but larger; stabilize inlets. | Keep navigation channels open. | Disrupt sand transport, potentially causing erosion. |
| Breakwaters | Offshore, parallel to the coast; reduces wave energy. | Protect beaches by reducing wave impact. | Can trap sand, altering sand distribution along the coast. |
| Revetments | Sloping structures placed on banks; absorb wave energy. | Protect banks and cliffs from erosion. | May not be as effective in high-energy environments and can be visually intrusive. |
These structures are often implemented as part of a broader coastal management strategy, taking into account the specific conditions of the coastline and the potential impacts on adjacent areas. It is important to note that these "hard engineering" solutions can have unintended consequences, and increasingly, "soft engineering" approaches such as beach nourishment and dune restoration are being used to mitigate erosion in a more sustainable manner.
