Coastal Management Lesson Objective: Understand why methods of engineering to protect the coast have advantages and disadvantages

MANAGING THE COASTLINE “Hundreds of thousands of tonnes of chalk fell 500ft to the beach on Sunday morning, in what is thought to have been the biggest sudden loss of coastline in Britain in living memory.” “Beach hit by 200 tonne cliff collapse” “Cliff collapse in Egypt leaves 24 dead” “Beach closes after cliff collapse” “Holbeck Hall Hotel crashes into the sea” “My house is only worth £1!”

Coasts : Coastal Protection / Hard and Soft Engineering Strategies Possible Questions : Why might certain coastal protection methods be selected instead of others? What is the difference between Hard and Soft coastal protection techniques? There are many different ways to reduce the rate of coastal erosion. Some are more expensive than others, some last longer, some are less of an eye- sore..etc. There are 2 main categories of coastal protection: HARD Engineering Strategies : Building or creating something which will interfere with coastal processes – usually to reduce the power of breaking waves against cliffs. SOFT Engineering Strategies : Working with the natural processes of sea and sand in a more environmentally sustainable way. Using the natural processes to bring about an intended effect. 17

What may influence decision Choosing which methods of coastal protection is most appropriate for an area of coastline may take into account the following: COST : concrete sea wall is expensive. Wood revetments are cheaper LIFETIME : rock groynes may last decades. Beach rebuilding will have to be carried out every few months ENVIRONMENTAL IMPACT : offshore reefs will not affect the look of the beach but concrete will look awful and put tourists off using the coastline SUSTAINABILITY : using hardwood from tropical rainforests for timber groynes is not sustainable – they will deteriorate and need replacing faster than new hardwood trees grow. Beach rebuilding is sustainable as you are moving sand from where it has been deposited, to where it has been eroded from.

Links to Holderness case study C-ErO0http:// C-ErO0

HARD ENGINEERING

Groynes These are built at right angles to the coastline. They aim to slow down longshore drift and trap sediment. They can be made of timber, concrete or rock. Wood groynes are around £5,000 each. Rock groynes cost around £200,000 each. Advantages: More beach material to dissipate wave energy which slows down cliff erosion. Cheap in comparison to other hard engineering methods Disadvantages: Beaches further along the coast are starved of beach material due to their affect on long shore drift.

Sea Walls Sea walls aim to prevent erosion by providing a barrier. They reflect the seas energy. The walls are placed parallel to the shore. They are usually expensive and can cost up to £5000 per square metre. Advantages: Provide excellent defence where wave energy is high They reassure the public They have a long life span. Disadvantages: Expensive Ugly- can put off tourists They can make it harder to access the beach Recurved sea walls cause greater erosion at the base of the wall

Rip rap/ Rock Armour These are often large boulders placed along the base of a cliff to absorb energy from waves. They cost about £3000 per metre Advantages: Cheap and efficient Disadvantages: Ugly Dangerous access to beach Costs increase when rock is imported

Gabions These are steel wire baskets filled with rock and built into an eroding cliff to improve stability They are fairly cheap, costing about £350 per metre. Advantages: Cheap Fairly effective Disadvantages: Unattractive They cannot withstand strong waves

Revetments 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 revetments. Cost: £2000 per metre Advantages: Less beach material is eroded compared to a sea wall Cheaper and less intrusive than a sea wall Disadvantages: Short life span Unsuitable where wave energy is high

Offshore reef Enormous concrete and natural blocks are sunk offshore to alter the wave direction Cost £1,950 per metre Advantages The waves break further offshore so reduce erosive power The allow the build up of sand Disadvantages May be reduced by heavy storms Difficult to install

SOFT ENGINEERING

Beach nourishment/ repenishment Beaches are built up, usually by pumping sand onto the beach The source of the material is usually from offshore dredging. This has to be undertaken on a regular basis (once every five, or less, years). Pumping material can be expensive (at least £1,250 per cubic metre) unless it is a by-product of channel dredging. Advantages: Retains the natural appearance of the beach Disadvantages: Off shore dredging of sand and shingle increases erosion in other areas and affects ecosystems. Large storms will require beach replenishment, increasing costs. Can be expensive, depending on the source of the sand

Managed retreat This is when areas of coast are allowed to erode. This is usually in areas where the land is of low value. Cost: depends on amount of compensation that needs to be paid to people affected by erosion. Advantages: Managed retreat retains the natural balance of the coastal system. Eroded material encourages the development of beaches and salt marshes. Disadvantages: People lose their livelihood e.g. farmers. These people will need to be compensated.

Cliff regrading Making the cliff face longer so that it is less steep Advantages: Cheap Natural- will encourage wildlife back into the area Disadvantages: Not effective on its own- need other defences at the base of the cliff Some homes on the cliff may need to be demolished

Consider…. 1. Why are settlements defended while agricultural land is left to the actions of the sea? 2. Some people are for coastal protection schemes and others are against. Explain these different opinions.

Past exam question