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Our coast is Our coast is disappearing!disappearing!

What can we do?What can we do?http://www.andrewdunnphoto.com

/

Erodedcliffpacifica.jpg

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Coastal ManagementRapid coastal erosion often poses a threat to the settlement, industry and recreation that has grown up along the coast and we often look to protect the coast from erosion through appropriate management of the coastal system.There are a number of possible approached to coastal management:

1. Building Structures to defend the Coast2. Pre-planning3. Do-Nothing

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There are There are a number a number

of of possible possible approachapproach

es to es to coastal coastal

managemmanagementent

Fivepolicies.jpg

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Building structuresBuilding structures

Can be divided into 2 typesHard EngineeringThese solutions generally involve concrete, metal, stone and other hard wearing materials that are intended to stop erosion and take little account of the environment.Soft EngineeringThese methods try not to disrupt the environment and tend to be used where the environment is more important than say a town or road

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1) Groynes

£10,000 each (wooden groynes)

£1.5m each (rock groynes)

A) Hard engineering

What are they designed to do?Stop longshore driftBut further down the coast this may mean that beaches are starved of sand and shingle

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2) Sea Walls

Energy is reflected (not absorbed). Over time the energy scours the base of the sea wall undermining it, causing it to collapse

Expensive at £5,000/m Designed to stop erosion, but what landforms would that prevent being created?Would you rather go on holiday and see Old Harry or a sea wall?

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3) Gabions

Much cheaper than sea walls £1000/m, but do you think they are attractive?

Small rocks, bound in place by cages absorb the wave energy and reduce erosion

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4) Revetments

£1,000/m

Open structure of planks absorb wave energy, but allow sand and shingle to build up beyond

Are these attractive?

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5) Rock armour or Rip Rap

Relatively cheap £1,000/m, but considered environmentally ugly.When resting on sand and shingle they may be moved out of position by waves

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Would you have these?Would you have these?

AdvantagesAdvantagesThey all manage to absorb the energy from the waves and so reduce erosionThey are long lasting

DisadvantagesDisadvantagesThey are not environment friendlyThey are not prettyThey are expensive

What if anything

could make a home here?

http://en.wikipedia.org/wiki/File:11-8-07_riprap_photo.jpg

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B) “Soft” Engineering

Less expensive than hard strategies

Longer term, more attractive and sustainable as they work with natural processes

How attractive do you consider these

to be?

Advantages & disadvantages?

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1) Beach Nourishment

The beach is widened; how will this affect the energy of the waves?It will reduce the energy that the wave has meaning less erosion.Cost: £100/m/yr

Sand and/or pebbles are brought in to replace material that has eroded away. Where do you think this replacement material has come from?It has been dredged from the sea bed. In some cases it is pumped onto the shore.

Advantages & disadvantages?

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2) Stabilising Sand DunesGrasses are planted in the sand dunes to bind them together, holding them in place.

Footpaths may be designated. Why might this be?

To reduce trampling of the dunes by people, which erodes them

Advantages & disadvantages?

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3) Managed RetreatWhen the land by the sea is of low economic value it may be allowed to erode.In some cases this eroded material forms beaches which naturally protect the coast.

Advantages & disadvantages?

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Soft Engineering solutionsSoft Engineering solutionsAdvantagesThere are no direct costs apart from that of removing any defences already in place and maintenance costs are very low.Sediment flow is also restored to its natural state, beaches can be naturally replenished due to erosion of the coast, providing protection and the balance of the coastline returns.

DisadvantagesA certain amount of land will inevitably be lost including settlements, farmland and other property. Because of this, managed retreat is often not a socially acceptable plan and may invoke the need for compensation to land-owners. There might be a loss of archaeological sites and heritage.

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How do these stack up?How do these stack up?

AdvantagesAdvantagesThey are more environmentally friendlyThey tend to be cheaperThey look nicer

DisadvantagesDisadvantagesIf they are trying to, they slow up rather than stop erosionIt might be your house that gets sacrificed?

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What do you What do you think should be think should be

done here?done here?http://www.bbc.co.uk/http://www.bbc.co.uk/

learningzone/clips/a-farm-is-learningzone/clips/a-farm-is-threatened-by-coastal-erosion-at-threatened-by-coastal-erosion-at-

holderness-east-yorkshire/holderness-east-yorkshire/3189.html 3189.html

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Why protect/manage the coast?: Case Study Holderness Coast

Over 30 villages have been lost since Roman times, erosion has been taking place for last 6000 yrs

Holderness Coast is fastest eroding stretch of coastline in Europe – an average of 2 metres fall into the North Sea each year

Locally, rates of erosion have been up to 10-20m with waves biting coast away

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Mappleton and Holderness Coast

This what they are doing along this coast – and what they are not!

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Soft boulder clay

Thin, narrow beaches do little to absorb wave energy

Chunks of coast slump down the cliff

Holbeck Hall, ScarboroughWhy are the

beaches thin and narrow?

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A bit of revisionA bit of revision

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Do you remember what this is showing?There were 3 processes … E, T and D?Which are the arrows showing? What is the heap of pebbles in the corner showing?What are wooden fence-like things called?Why are they there?This picture is showing LSD – which is?

Direction of swash

Longshore Drift

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And this happens if the long shore And this happens if the long shore drift is allowed to carry ondrift is allowed to carry on

The coast changes direction

But the long shore drift carries on

But the load gets dropped as the longshore drift

looses power

Deposits and seed are caught behind the shingle

bar and a salt marsh begins to grow

What is this feature

called? It begins with

S

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What is the feature you can see on What is the feature you can see on this map?this map?

http://en.wikipedia.org/wiki/File:East_Riding_of_Yorks_outline_map_with_UK.png

© Copyright Stanley Howe and licensed for reuse under this Creative Commons Licence. It is called Spurn Head

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This Spurn This Spurn HeadHead

What 2 features can you see in the picture which might be helping the Head from moving on?What kind of engineering is each of them?What do you think is happening in the lower pictures?

© Copyright Stephen McKay and licensed for reuse under this Creative Commons Licence.

Crumbling sea wall   © Copyright Charles Rispin and licensed for reuse under this Creative Commons Licence.

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This Spurn This Spurn HeadHead

What is going on in the top picture? Is it working?This is a sculpture of a welder made from flotsam and jetsamWhat is the method of sea defence you see in the back ground?Flotsam fell overboard while jetsam was thrown deliberately

© Copyright Stephen Horncastle and licensed for reuse under this Creative Commons Licence.

Beach sculpture Spurn Point Sculpture of welder made from flotsum and jetsum on beach.   © Copyright Steve F and licensed for reuse under this Creative Commons Licence.

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This Spurn This Spurn HeadHead

What are items in the top picture called?What do you think has happened recently in the bottom picture?

Tangled Nets   © Copyright Stephen Horncastle and licensed for reuse under this Creative Commons Licence.

Storm damage to the road near the narrowest point on the peninsula. Looking North   © Copyright Paul Allison and licensed for reuse under this Creative Commons Licence.

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This is salt marshThis is salt marsh

Can you remember where that forms on a spit?How does it get there?

© Copyright Paul Glazzard and licensed for reuse under this Creative Commons Licence.

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No Homework to No Homework to talk abouttalk about

You have it alreadyYou have it already

Have a great half termHave a great half term