1. PowerPoint 9: Coastal management strategies

2. Hard engineering strategies
Hard engineering strategies act as a barrier between the sea and the land. Artificial structures are used to change or disrupt natural processes.
Examples of hard engineering strategies include sea walls, groynes, revetments, rock armour (rip rap), gabions and offshore breakwaters.

3. Sea walls
Sea walls are often built at the foot of cliffs to prevent cliff erosion and subsequent collapse. They are often curved, to deflect the energy of the waves back onto themselves.
Advantages
very strong coastal defence, particularly where wave energy is high
long life span – at least 25 years
reassuring to the public
may provide a walkway along the top
Disadvantages
very expensive – up to £4000 per metre
can impede access to the beach for tourists
can cause beach erosion at the base of the wall
Photo © Tony Atkin.

4. Groynes
Groynes are barriers of wood or concrete, at right angles to the beach. They trap sediment transported by longshore drift, and help to create wider beaches, which absorb wave energy, reducing cliff erosion.
Advantages
comparatively cheap – approximately £7000 each
do not affect access to the beach
retain a wide, sandy beach for tourists
Disadvantages
beaches further along the coast are starved of the sediment trapped by the groynes
will not last as long as other hard engineering strategies
Photo © Chris Parfitt.

5. Revetments
Revetments are wooden slatted barriers, usually built at the back of beaches to protect the base of the cliff. They dissipate the energy of waves breaking on the revetments. Concrete revetments called accropodes may also be used.
Advantages
erodes less beach material than a sea wall
cheaper than a sea wall – approximately £2000 per metre
Disadvantages
Short life span, particularly those made of wood
not suitable for areas of high wave energy
Photo © BazDaRambler.

6. Rock armour
Rock armour, or rip rap, is placed at the bottom of cliffs or the back of beaches. The large boulders of hard resistant rock absorb wave energy. Rock armour may be used in combination with revetments or a sea wall.
Advantages
cheap compared to sea walls, approximately £3000 per metre
lasts a long time and is efficient at absorbing wave energy
Disadvantages
unattractive and makes access to the beach difficult and dangerous
costs increase dramatically if the rocks have to brought a long distance or imported
Photo © John Lyon.

7. Gabions
Gabions are cages of wire mesh filled with rocks and stones, which are placed at the back of beaches or at the base of cliffs. They absorb wave energy, reducing erosion.
Advantages
relatively cheap, approximately £100 per metre
efficient at absorbing wave energy
Disadvantages
unattractive
short life span compared to sea walls
not very effective in areas of high wave energy
Photo © Colin Babb.

8. Offshore breakwater
Offshore breakwaters are built of rocks or boulders. They protect the shoreline by absorbing wave energy, which reduces erosion, and by changing wave direction, which reduces longshore drift.
Advantages
as this form of coastal management is located offshore, the beach retains its natural appearance
Disadvantages
unattractive
expensive to build and maintain (£2000-£20,000 per metre)
do not directly protect the cliffs
beach material continues to be eroded
Photo © Marathon.

9. Soft engineering strategies
Soft engineering is enhancing natural features, such as beaches and sand dunes, to protect the coast from erosion.
Examples of soft engineering strategies include beach nourishment, managed retreat and dune stabilisation.

10. Beach nourishment
Beach nourishment is where sand and shingle (dredged from offshore or inland) are used to make the beach higher and wider. A wide beach is an effective way of reducing cliff erosion.
Advantages
beach nourishment is relatively cheap, approximately £20 per cubic metre
the natural appearance of the beach is preserved
Disadvantages
has to be carried out regularly, usually twice a year, and sometimes more frequently,
for example after a storm
offshore dredging can increase erosion in other parts of the coastal system
Photo © Pevensey Coastal Defence.

11. Dune stabilisation
Sand dunes are effective barriers to wave erosion, but without vegetation they disappear. To prevent this, dunes are planted with marram grass whose roots keep the sand in place.
Newly planted areas are often fenced off to allow the marram grass to become established.
Advantages
it is relatively cheap, about £2000 per 100 metres
it maintains the natural environment and is popular with wildlife and people
Disadvantages
planting marram grass is time consuming
people do not always keep away from newly planted areas
Photo © Scottish Natural Heritage.

12. Managed retreat
Managed retreat lets the coastline erode naturally, often by removing coastal protection. Areas of the coast, usually land of low value such as grazing land, are allowed to flood in order to protect areas further inland.
Advantages
maintains the natural balance of the coastal system
beaches and salt marshes can be created to protect against erosion
Disadvantages
previously protected land is flooded
farmers and other coastal dwellers can lose incomes and even their homes
Photo © Southwest Coastal Group.

13. Coastal management in Lyme Regis
Phase III: Monmouth Beach and Ware Cliffs
Phase V: The Cobb
Phase III: Cobb Gate to the Harbour (completed)
Phase I: Cobb Gate to Church Cliff (completed)
Phase IV: East Cliff (completed)
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