Coasts : Coastal Protection / Hard and Soft Engineering Strategies

Key Terms :

Coastal protection

Coastal management

Protection strategies

Hard engineering solutions

Soft engineering solutions

Sustainable protection strategies

Example / Case-Study :

Holderness coast

Easington Gas Terminal

Withernsea

Hornsea

Mappleton

Possible Questions :

Why might certain coastal protection methods be selected instead of others?

What is the difference between Hard and Soft coastal protection techniques?

Weblinks http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalmanagementrev2.shtml

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.

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 tetrapods 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.

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Coasts : Coastal Protection / Hard Engineering Strategies

Key Terms :

Hard engineering

Concrete Sea wall

Revetment

Gabions

Rock Armour / Rip-Rap

Example / Case-Study :

Holderness coast

Easington Gas Terminal

Withernsea

Hornsea

Mappleton

Possible Questions :

Which coastal protection would you suggest for a coastal resort – and which would you reject – and why?

Which of these hard engineering techniques is most effective?

Weblinks http://www.bbc.co.uk/schools/gcsebitesize/geography/coastal/coastalmanagementrev2.shtml

Type / Location Advantages Disadvantages

Concrete Sea Wall

(HARD technique)Deflects the waves

(Withernsea, East Yorkshire)

•Deflects Waves•Strong•Effective•Lasts a long time

•Expensive•Likely to need repair fairly regularly•Deflected waves can ‘scour’ sea bed and undermine the sea wall foundations

Revetment

(HARD technique)Inter-locking concrete slabs or wooden boards to deflect the waves.(Hornsea, East Yorkshire)

•Provides hard face to cliff•Easily installed•Cheaper than sea wall•Deflects wave power

•Can be eroded from below easily•Needs frequent repair•Not very attractive

Gabions

(HARD technique)Wire cages filled with stones/rocks stacked along the cliff base(Easington, E. Yorkshire)

•Easily installed•Cheaper than sea wall

•Not very attractive•Needs frequent checking & repair•Not easy for people to get over to get to beach•May contain rats nests

Rock Armour / Rip-Rap

(HARD technique)Granite boulders (very resistant)(Withernsea, East Yorkshire)

•Popular option in recent years – seen to be effective•Cheaper than sea wall

•Not very attractive•Not easy for people to get over to get to the beach (broken ankles)•Rats may live in spaces

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Coasts : Coastal Protection / More Hard Engineering Strategies

Key Terms :

Hard engineering

Tetrapods

Groynes / Breakwater

Cliff Drainage

Example / Case-Study :

Holderness coast

Easington Gas Terminal

Withernsea

Hornsea

Mappleton

Possible Questions :

Which coastal protection technique is most appropriate for a section of cliff which has a history of slumping – and why?

Which coastal defence technique would be best for a coastal industry – and why?

Weblinks http://www.s-cool.co.uk/alevel/geography/deltas-and-estuaries-and-changes-to-coastal-areas/human-influences-at-the-coast.html

Type / Location Advantages Disadvantages

Tetrapods

(HARD technique)Interlocking concrete shapes which can be made where they are to be used.(50% of Japan’s coast)

•Popular option in Japan – seen to be effective•Can be built on-site•Allows some waves through – so less ‘reflected’ wave damage

•Not attractive at all•Almost impossible for people to get over to get to the beach •Dangerous to swimmers & small boats – stick out.

Groynes / Breakwater

(HARD technique)Wooden or boulder ‘fences’ designed to trap & accumulate sand.(Hornsea, East Yorkshire)

•Builds up the beach•Makes a wider beach•Provides calm water•Encourages tourism

•Need repairs•OK with medium waves – but strong waves still get to cliff face•Leads to faster cliff erosion down the coast by robbing it of potential beach material.

Cliff Drainage

(HARD technique)Removing water from a cliff quickly so it’s less likely to Slump(Scarborough, North Yorkshire)

•Can reduce slumping of clay or sandy cliffs•Can be made to Blend in with the coastal landscape

•Only useful where slumping is an issue•Needs to operate with other solutions like groynes or rock armour as well.

Surface Water Drainage Pipe

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Coasts : Coastal Protection / Soft Engineering Strategies

Key Terms :

Soft Engineering strategies

Offshore Reef

Beach Re-cycling

Beach Re-building

Example / Case-Study :

East Anglia

Pevensey Bay, East Sussex

Possible Questions :

Why are soft engineering strategies more sustainable?

What are the advantages of soft engineering coastal defences over hard engineering defences?

Weblinks

http://www.s-cool.co.uk/alevel/geography/deltas-and-estuaries-and-changes-to-coastal-areas/human-influences-at-the-coast.html

Type / Location Advantages Disadvantages

Offshore Reef

(SOFT technique)Man-made artificial reefs are built just out to sea to for the waves to break on them and create calmer water at the coast(East Anglia coast)

•Provides inshore area of calm water•Effective at preventing the cause of cliff erosion

•Very expensive•Need openings for fishing boats to get to sea•Damages fish nets.•Can be ‘breached’ in stormy conditions and need repair.

Beach Re-Cycling

(SOFT technique)Moving sand from areas it has accumulated to areas it has been eroded from.(Pevensey Bay, East Sussex))

•Adds to tourist amenity by making bigger beach•Attractive•Works with the natural processes of the coast

•Needs frequent renewal of more sand•Does not protect cliff face from winter storm waves.

Beach Re-Building

(SOFT technique)Dredge sand from estuary or sea bed and put it back on the beach(Pevensey Bay, East Sussex))

•Adds to tourist amenity by making bigger beach•Attractive•Works with the natural processes of the coast

•Needs frequent renewal of more sand•Does not protect cliff face from winter storm waves.

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Why have they built 2 rock groynes?

Why is one larger than the other ?

Are they working ? How can you tell?

Coasts : Coastal Protection / Hard Engineering Case-Study : Mappleton Location

Mappleton was given a £3m coastal defence scheme in 1992 due to the danger to the main north-south coast road being lost if erosion continued. This would have severely affected trade and emergency transport in the region.

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Coasts : Coastal Protection / Hard Engineering Case-Study : Mappleton Strategies 22

Key Terms :

Longshore Drift

Active cliff

Accumulation

Beach-robbing

Precedent

Evaluation

Example / Case-Study :

Mappleton, East Yorkshire

Possible Questions :

Why are there sometimes negative consequences of protecting some parts of the coast and not others?

What conflicts of interest might arise as a result of coastal protection measures?

Weblinks

View this BBC video clip

And this one BBC video clip

Successful Outcomes of the Mappleton Defences

•Erosion has been effectively stopped behind the defences. The grass growing on the landscaped cliffs shows they are no longer ‘active’ – in contrast to the cliffs downcoast.

•The road has been ‘saved’ – along with the village.

•Tourism in the area has increased as a result of the wider beach and the interest in the scheme.

Coasts : Coastal Protection / Hard Engineering Case-Study : Mappleton Evaluation

Less Successful Outcomes of the Mappleton Defences

•Erosion has increased downcoast. Material moved by Longshore Drift is successfully ‘trapped’ at Mappleton by the rock groynes – but this means it is not moving down the coast to accumulate on beaches there. As a result beaches south of Mappleton are robbed of sand, becoming narrower and erosion is faster than it used to be before the scheme

•Other villages under threat of coastal erosion say that a precedent has been set – and their villages should now be protected like Mappleton – otherwise it is unfair.

•Erosion is still taking place north of Mappleton, so in the future the protected area is likely to become a peninsula as the coast to the north and south retreats westward. So more money will have to be spent protecting the sides of it.

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Coasts : Coastal Protection / Easington Gas Terminal – A Controversial Issue

20% of Britain’s gas comes onshore at the Easington Gas terminal from the undersea gas pipeline stretching from Norway. Protecting this piece of coastline is therefore vital. The following issues occur though:

•Which form of coastal protection should be selected? What criteria would you select for your basis of choosing (cost?, effectiveness?, environmental impact? Sustainability?...

•Who should pay for any coastal protection here? (The government? East Yorkshire Council? British Gas? Gas customers?)

•Who could be negatively affected by protecting this area of coastline? (look further along the coast beyond the gas terminal)

•Should there be any compensation for anyone negatively affected? If so – who should pay it?

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The Pevensey Bay Beach Replenishment

Project

Suffolk Coast South England

Using Soft Engineering Coastal Protection techniques to Hold the Line on a coast under threat.

Coasts : Coastal Protection / Soft Engineering Case-Study – Pevensey Bay 25

Reasons behind the Beach Replenishment scheme at PevenseyReason 1 : Almost all of the 150 wooden Groynes had deteriorated and either needed repair or replacement. Both would be very expensive and use a lot of hardwood – which isn’t a sustainable solution. They were removed in 2007.

Reason 2 : The beach environment has many valuable plant species and these needed to be protected and encouraged to thrive.

Reason 3 : There are many coastal homes looking out over the beach – and their protection, but also their views needed preserving.

Removing the old groynes

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Technique 1 :

Beach Replenishment

Sand and gravel is hoovered up by a dredger ship off the coast, and sprayed onto the lower beach at high tide.

At low tide, bulldozers push the material up the beach to raise the height of the beach

This takes place 3 times a year – in early Autumn after the holiday season, in January before the main winter storms, and at Easter just before the holiday season and to correct winter storm damage to the beach.

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Technique 2 :

Beach Recycling

There is strong Longshore Drift from West to East along the bay

Bulldozers dig up the accumulated sand at the eastern end of the bay and transfer it to trucks.

Trucks take the beach material back along the beach to the western end – so that Longshore Drift can distribute it along the length of the beach over the year.

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Technique 3 :

Beach Re-profiling

This means changing the gradient of the beach to the best one for absorbing the wave energy.

Winter storms remove lots of the lower beach with their strong backwash.

Bulldozers spread the sand evenly across the beach in Spring to create a more even profile – which is better at absorbing wave energy.

Before

Re-profiling

After

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