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Unlock This CourseRevetments are one of the most common hard engineering solutions used to protect coastlines from erosion and wave damage. They act like a protective wall or slope covering that absorbs and deflects wave energy, preventing it from reaching and damaging the land behind. Think of them as armour for the coast!
Unlike sea walls that stand vertically, revetments are typically sloped structures that follow the natural angle of the beach or cliff face. This makes them less obvious and often more effective at dealing with wave energy.
Key Definitions:
When waves hit a revetment, the sloped surface causes the water to flow up and then back down, reducing the energy that would otherwise erode the coastline. The gaps between rocks or blocks also allow water to drain through, reducing the pressure from backwash.
Revetments come in many different forms, each designed to suit specific coastal conditions and budgets. The choice depends on factors like wave strength, available materials and how much money is available for the project.
The most common type of revetment uses large rocks or boulders, typically weighing 1-10 tonnes each. These rocks are carefully placed to create a stable, interlocking structure that can withstand powerful waves.
Relatively cheap, uses natural materials, allows drainage, can be repaired easily and provides habitat for marine life.
Can look unsightly, rocks may shift in storms, requires regular maintenance and can be dangerous for people walking on them.
£1,000-3,000 per metre depending on rock size and transport costs. Cheaper than most alternatives.
These use specially designed concrete blocks that interlock together. Some have complex shapes that help break up wave energy more effectively than simple rocks.
Some concrete blocks are designed with holes or special shapes that create turbulence in the water, which helps absorb even more wave energy than solid blocks would.
These consist of wire mesh cages filled with rocks or concrete. They're flexible and can adapt to ground movement, making them useful in areas where the coastline might shift.
Mappleton is a small village on the Holderness coast that was losing 2 metres of land per year to erosion. In 1991, rock armour revetments were installed along with groynes. The revetments successfully protected the village, but caused increased erosion further south at Great Cowden, showing how coastal defences can transfer problems elsewhere.
This historic town has used a combination of revetments and sea walls to protect both the town and its famous fossil-rich cliffs. The revetments here use local limestone, helping them blend in with the natural environment while providing effective protection.
Results: The defences have successfully protected the town centre and harbour, allowing tourism to continue. However, they cost over £20 million and require ongoing maintenance.
Revetments can provide new habitats for marine creatures like crabs, fish and seaweed. However, they also change natural coastal processes and can prevent beaches from forming naturally.
Revetments are popular because they offer good protection at a reasonable cost. They're also more flexible than rigid sea walls, which means they're less likely to fail catastrophically during extreme storms.
Protect valuable coastal property, support local tourism, cheaper than sea walls and can use local materials to support local economy.
Create new marine habitats, allow natural drainage, can use sustainable materials and are less disruptive to install than some alternatives.
Protect communities from flooding, maintain access to beaches, preserve coastal heritage sites and provide employment during construction.
Despite their benefits, revetments aren't perfect solutions. They can create new problems while solving others and they don't work well in every coastal situation.
Main Issues:
Understanding how revetments compare to other coastal defences helps explain when and why they're chosen for specific locations.
Sea walls are more expensive but provide better protection against flooding. Revetments are cheaper and more natural-looking but offer less flood protection. Sea walls last longer but are more likely to fail suddenly.
Soft engineering like beach nourishment is more sustainable but needs constant maintenance. Revetments provide immediate, reliable protection but don't work with natural processes like soft engineering does.
Engineers must consider many factors when designing revetments to ensure they work effectively and don't cause unexpected problems.
Key Factors:
Climate change is making coastal management more challenging. Rising sea levels and more intense storms mean that revetments built today may need upgrading sooner than expected. Many coastal engineers are now designing revetments that can be easily modified or extended as conditions change.
Revetments are a practical and cost-effective solution for protecting coastlines from erosion. While they're not suitable for every situation and do have some drawbacks, they remain one of the most widely used coastal defence methods worldwide. Understanding their strengths and limitations is crucial for making informed decisions about coastal management.
As climate change continues to affect our coastlines, revetments will likely remain important tools in coastal defence, but they'll need to be used as part of integrated coastal management strategies that also include soft engineering and managed retreat where appropriate.