C - Cliff Collapse

cliff_collapse.jpg
BBC videos on cliff collpase:
Buildings threatened by erosion - http://www.bbc.co.uk/learningzone/clips/a-dairy-farm-is-threatened-by-coastal-erosion-at-holderness-east-yorkshire/3190.html
Buildings threatened by erosion - http://www.bbc.co.uk/learningzone/clips/a-farm-is-threatened-by-coastal-erosion-at-holderness-east-yorkshire/3189.html
Buildings threatened by erosion - http://www.bbc.co.uk/learningzone/clips/a-house-threatened-by-coastal-erosion/3188.html
Erosion at Hallsands - http://www.bbc.co.uk/learningzone/clips/coastal-erosion-at-hallsands-causes-and-effects/9967.html
Erosion at Holderness - http://www.bbc.co.uk/learningzone/clips/coastal-erosion-at-holderness-east-yorkshire/3187.html
Erosion at Hallsands - http://www.bbc.co.uk/learningzone/clips/hallsands-destruction-of-coastland/3242.html
Case study on Happisburgh - http://www.bbc.co.uk/learningzone/clips/living-with-coastal-erosion-in-happisburgh-east-anglia-pt-1-2/7361.html
Case study on Happisburgh - http://www.bbc.co.uk/learningzone/clips/living-with-coastal-erosion-in-happisburgh-east-anglia-pt-2-2/7364.html
Various factors can contribute to cliff collapse. These include:
  • weathering processes - such as heavy rainfall that can saturate the land and make it unstable
  • mass movement such as sliding and slumping - which is more likely if the land is made of soft weak rock types
  • the power of the waves - crashing against the cliffs and undercutting them from below

Barton-on-Sea, Hampshire

Barton-on-Sea is a small village in Christchurch Bay and has long been affected by coastal erosion and cliff collapse.

Over the years a number of buildings and most recently a cafe have been lost to the sea.

Sea defences have been built to prevent coastal erosion but in 2008 there was a fresh landslip. The older houses in the settlement are now only 20m from the sea. It is expected that the houses will be lost to the sea in the next 10 to 20 years.

Why are the cliffs at Barton-on-Sea so prone to collapse?
  • the rocks are weak sands and clays. They are easily eroded by the sea and have little strength to resist collapse.
  • the arrangement of the rocks causes water to 'pond-up' within the cliffs. This increases the weight of the cliffs. The increase in water pressure within the cliffs which encourages collapse.
  • the coastline is exposed to the direct force of the prevailing south-westerly winds. This means a very long fetch and as a resultthe waves are very powerful leading to rates of erosion as much as 2m a year in places.
  • small streams increase the amount of water entering the cliffs which increases the weight of the cliff and then leading to collapse
  • buildings on the cliff top have increased the weight on the cliffs, making them more vulnerable to collapse

Video looking at cliff collapse at Beachy Head, West Sussex: