Increasing Risks: Holderness Coast Case Study Flashcards
Where is Holderness?
Holderness is a lowland region of England that lies between the chalk hills of the Wolds and the North Sea. It is part of the East Riding of Yorkshire.
Why is it so under threat?
The Holderness Coast is one of Europe’s fastest eroding coastlines. The average annual rate of erosion is around 2 metres per year. The main reason for this is the Holderness Coastline is made up of soft boulder clays.
There are also powerful waves due to the long fetch (all the way from the Arctic Ocean).
What was done in Hornsea?
Wooden groynes have been built to trap sediment carried by longshore drift.
Advantages of the defences in Hornsea?
These keep the beach in place at Hornsea, and in turn protects the cliffs and town.
Advancing waves, or swash, have to travel further over the beach, and the friction caused absorbs much of their energy.
Less energy results in less erosion.
Disadvantages of the defences in Hornsea?
South of Hornsea, the village of Mappleton was being starved of the sediment trapped by Hornsea’s groynes.
Longshore drift occurs in Mappleton beach but none of it is replaced.
Rapid wave attack eroded the cliffs so much that in the 1990s nearly 4 metres of cliff per year was being eroded.
What was done in Mappleton?
Two rock Groynes were built at a cost of £2 million in 1991. They consist of Norwegian granite, laid out like groynes. The cliff face was also regraded or shaped to make it less steep and therefore more stable.
Disadvantages of the defences in Mappleton?
The downsides are that the land three kilometres south of mappleton in cowden is being faced with the problem of sediment starvation which has led to increased cliff erosion.
What was done in Withernsea?
Sea walls have been built- straight walls and recurved walls.
At the base of the sea wall is also rip rap.
Advantages of the defences in Withernsea?
Straight walls reflect wave energy out to sea rather than absorbing it, and form a barrier to prevent undercutting of cliffs.
It worked well and protecting the holiday resort and provided a promenade for tourists.
Recurved walls dissipate (or spread out) some of the wave energy, thus reducing the erosion at the base of the wall and extending its life.
Rip rap consists of large granite boulders at the base of the sea wall which dissipate the energy so preventing scouring.
Disadvantages of the defences in Withernsea?
Over time the wave energy eroded (or scoured) the base of the wall and undercut it, causing it to collapse.
Recurved walls are expensive to build because of their shape
Rip rap, to some, are unattractive.
What was done in Easington?
A rock revetment has been built to protect Easington gas terminal. The boulders are placed like a wall in a line of defence along shoreline.
Advantages of the defences in Easington?
They’re long lasting. It is effective at absorbing (not reflecting) wave energy using large air spaces between the boulders and a broad surface area
Disadvantages of the defences in Easington?
Revetments are very expensive.
Some people think they’re unattractive.
Give the social impacts of the erosion in Holderness?
Property prices along the coast have fallen sharply for those houses at risk from erosion.
Around 30 villages have been lost since roman times.
Give the environmental impacts of the erosion in Holderness?
Some ‘Sites of Special Scientific Interest’ are threatened- e.g the lagoons near Easington.
