Coastal Erosion Case Study: The Holderness Coast

Yorkshire, UK

Learning intentions

To learn what is happening to the Holderness coast, what processes are shaping it and how it is being managed

• The Holderness Coast is one of Europe's fastest eroding coastlines.

• The average annual rate of erosion is around 2 metres per year.

• Is losing around 2 million tonnes of material every year.

• Underlying the Holderness Coast is a solid bedrock made up of chalk.

• However, in most place this is covered by a glacial deposit called till, deposited over 18,000 years ago. It is this soft material (sometimes called boulder clay) that is being rapidly eroded.

Resistant Chalk Headland at Flamborough Head

Spurn Point provides evidence of longshore drift on the Holderness Coast. It is an excellent example of a spit. Around 3% of the material eroded from the Holderness Coast is deposited here each year.

Boulder clay cliffs near Mappleton – what’s happening? Would you choose to defend this stretch of coast?

What processes are shaping the coast?• EROSION • abrasion (corrasion)• hydraulic action• attrition• WEATHERING & MASS MOVEMENT• Free fall• Mudflows• Slumps (landslides)• TRANSPORT• longshore drift• tidal

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Landslips: also known as rotational slumps, are occasional rapid movements of a mass of earth or rock dropping down along a concave plane. Water percolating through sandstone gets into the clay beneath, saturating it. With the weight of the rock above forcing down on it the clay moves seawards as a mud flow. With the clay moving sideways the sandstone above slumps down. Undercutting of a steep slope by the sea weakens the rock above, making a slump more likely.

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Rockfall: rapid, free-fall of rock from a steep cliff face due to gravity. This is made worse by freeze-thaw action loosening the rock - water enters the joint (vertical crack), freezes and expands, breaking up the rock. A scree slope of fallen rock is formed at the bottom of the cliff. It is also possible for free falls to occur in very dry conditions – for example clay cracks as it dries out and then crumbles easily

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Mudflow: occurs on steep slopes over 10°. It's a rapid sudden movement which occurs after periods of heavy rain. When there is not enough vegetation to hold it in place, saturated clay flows out of the cliff face, almost like a river of mud.

Annotate the photograph showing features of erosion

• Undercutting at the base of the cliff• Abrasion as waves crash into the cliff face armed with

gravel and sand• Signs of attrition• Slumping/slumped block with grass on top• Mudflow/remnant of a mudflow• Fallen masonry that suggests the cliffs are receding• Abandoned house ion precarious position• Shallow beach that offers very little protection• Remains of boulder clay washed out of the cliff• Very steep cliff/unstable cliff face of bare boulder clay• Soft easily eroded boulder clay

Describe the effects of the erosion here

What would the knock on effects be?

What are the main land uses along the Holderness Coast?

Why land use important when studying erosion?

Management approaches

• Do nothing

• Advance the line

• Hold the line

• Retreat the line

What is best for Holderness? Action taken at Holderness is part of a HOLISTIC

management approach and involves different strategies for different locations

• Where there is little of value to protect it may be a case of retreat the line

• Where the land is valuable such as tourist centres and towns it may be hold the line (or perhaps even advance the line).

• In some other locations the best decision may be to roll back the line

• BUT WHATEVER THE DECISION IT MUST BE PART OF AN INTEGRATED COASTAL ZONE MANAGEMENT PLAN TO AVOID PROBLEMS FURTHER ALONG THE COAST.

Coastal Erosion Case Study: The Holderness Coast

Yorkshire, UK