coastal management holderness ap

What determines whether a particular stretch of coastline is protected or not?

Protected Unprotected

Robin Hood’s Bay

1770-1994, 200 houses went over the cliffs

Caravans/cheap housing that is sparsely distributed

Whether land is protected or not comes down to the economic value of the land

A) Hard engineering

1) Groynes1) Groynes

Stop longshore drift

What are they designed to do?

Further down the coast this may mean that beaches are starved of sand and shingle

1) Groynes

£10,000 each (wooden groynes)

£1.5m each (rock groynes)

A) Hard engineeringMappleton, Yorks. coast

2) Sea Walls2) Sea Walls

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?

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

This is reduced by absorbing the energy and angling the wall

3) Gabions3) Gabions

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

4) Revetments4) Revetments

4) Revetments

£1,000/m

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

Are these attractive?

5) Rock Armour and Rip 5) Rock Armour and Rip RapRap

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

Gabions and Groynes Gabions and Groynes

6) Gabions and groynes together

Why might you choose to implement more than one coastal management strategy at a time?

To protect against erosion and longshore drift

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?

1) Beach Nourishment

The beach is widened; how will this affect the energy of the waves?

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.

It will reduce the energy that the wave has meaning less erosion.

Cost: £100/m/yr

2) Stabilising Sand Dunes

Grasses 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

3) Managed Retreat

When 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.

Holderness case study Holderness case study ((landformlandform case study) case study)

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

Holderness Coastline Video Holderness Coastline Video - Answers- Answers

1.1. Chalk depositsChalk deposits

2.2. Wave cut notch erosionWave cut notch erosion

3.3. Boulder clay- left by the ice sheetBoulder clay- left by the ice sheet

4.4. The boulder clay is easily eroded as it is a The boulder clay is easily eroded as it is a soft rocksoft rock

5.5. Longshore driftLongshore drift

6.6. GroynesGroynes

7.7. RipRap, they stop the waves eroding the RipRap, they stop the waves eroding the coastline by allowing the wave to break on coastline by allowing the wave to break on them and spread out the energythem and spread out the energy

Holderness Coastline Video Holderness Coastline Video cont’dcont’d

8.8. As there is no erosion, down the As there is no erosion, down the coastline there will be no deposits and coastline there will be no deposits and so more erosion occursso more erosion occurs

9.9. 16m has eroded in 35 years16m has eroded in 35 years10.10. Sea wall and rip rap. Sue Earl does not Sea wall and rip rap. Sue Earl does not

live in a settlement, her farm was live in a settlement, her farm was deemed as not worth protecting.deemed as not worth protecting.

11.11. Spit- longshore drift deposition formed Spit- longshore drift deposition formed it. Groynes were built to maintain it.it. Groynes were built to maintain it.

12.12. Shifting mudbanksShifting mudbanks13.13. Too expensive, and there are no Too expensive, and there are no

important settlements.important settlements.

Soft boulder clay

High energy waves

because of long fetch

Thin, narrow beaches do little to absorb wave energy

The beaches are thin because the material is carried away by longshore drift

Why are the beaches thin and narrow?

Chunks of coast slump down the cliff

Holbeck Hall, Scarborough

Holderness Coast – Cliff Processes

Material slumps down the cliff

Rain water enters cracks

Boulder Clay Cliff

Beach

Sea

Cracks formed by wetting and drying

Removal of slumped material by sea

Slip plane developing

Mappleton and Holderness Coast