Why defend the coast?
There are a number of reasons for protecting the coast. Coast lines tend to be very heavily populated. They are areas of high economic value due to tourism. Coastlines are particularly prone to flooding. Finally, they are fragile ecosystems which take a long time to recover if they are destroyed.
Hard Engineering
Hard engineering approaches tend to be expensive, last only a short amount of time, are visually unattractive and unsustainable. They often increase erosion in other places further down the coast.
Hard Engineering Techniques
The table below shows a range of hard engineering techniques.
| Technique |
Description |
Advantage |
Disadvantage |
Approximate Cost |
Groynes
|
Groynes are wooden barriers constructed at right angles to
the beach to retain material. Material is trapped between these
groynes and cannot be transported away by longshore drift. Groynes
encourage a wide beach which helps absorb energy from waves, reducing
the rate of cliff erosion. |
Cheap, retain wide sandy beaches and do not affect access to the beach. |
Beaches to the south of the defences are starved of beach material due to their affect on long shore drift. |
£7000 each |
Sea Walls
|
Sea walls are usually built along the front of cliffs, often
to protect settlements. They are often recurved which means waves are reflected back on themselves. This can cause the erosion of material at the base of the sea wall. |
Provide excellent defence where wave energy is high, reassures the public and long life span. |
Expensive, can affect beach access, recurved sea walls can increase the erosion of beach material. |
£3000-4000/m |
Reventments
|
Traditionally these have been wooden slatted barriers
constructed towards the rear of beaches to protect the base of cliffs. Energy from waves is dissipated by them breaking against the reventments. In recent times concrete reventments such as accropodes have been used in places such as Scarborough. |
Less beach material is eroded compared to a sea wall. Cheaper and less intrusive than a sea wall. |
Short life span and unsuitable where wave energy is high. |
£2000/m |
Rock armour / boulder barriers
|
These are often large boulders placed along the base of a cliff to absorb energy from waves. |
Cheap and efficient |
Unattractive, dangerous access to beach, costs increase when rock is imported. |
£3000/m |
Gabions
|
This is where rocks and boulders are encased in wired mesh. They absorb the energy from waves. |
Cheap and efficient. |
Shorter life span than a sea wall. Visually unattractive. |
£100/m |
| Off-shore breakwater |
These are large concrete blocks and boulders
located off shore to change the direction of waves and reduce longshore drift. They also help absorb wave energy. |
Beaches retain natural appearance. |
Difficult to maintain, unattractive, does not protect the cliffs directly and does not stop beach material from being eroded. |
|
Soft Engineering
Soft engineering approaches are less expensive, are more long term, attractive and sustainable as they work with natural processes.
Soft Engineering Techniques
The table below shows a range of soft engineering techniques.
| Technique |
Description |
Advantage |
Disadvantage |
Approximate Cost |
| Beach nourishment |
Beaches are made higher and wider by importing sand and shingle to an area affected by longshore drift. |
Cheap, retains the natural appearance of the beach and preserves the natural appearance of the beach. |
Off shore dredging of sand and shingle increases erosion in other areas and affects the ecosystem. Large storms will require beach replenishment, increasing costs. |
£20 /cu.m |
| Managed retreat |
This is when areas of coast are allowed to erode. This is usually in areas where the land is of low value. |
Managed retreat retains the natural balance of the coastal system. Eroded material encourages the development of beaches and salt marshes. |
People lose their livelihood e.g. farmers. These people will need to be compensated. |
Depends on amount of compensation that needs to be paid to people affected by erosion. |
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