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GCSE Coastal management
1- Coastal management:
Case Study Swanage In Dorset on the south coast of England
In Durlston Bay, erosion mainly occurs at one particular point, where there was a major
weakness in the resistant limestone rock. There were three methods used to protect the cliffs
from erosion (recession): Cliff regrading – extending it forward, making slope longer and
less steep. Reduces the risk of mass movement. Drainage – removing excess water, so slope
wasn’t as heavy or lubricated after rain. Reduces the risk of mass movement and freeze-thaw
weathering. Rip rap placement – Large boulders at the base of the cliff to resist wave attack
and dissipate wave 21energy.
Swanage Bay
This is a popular recreational area for beach users, diving, fishing and sailing. Erosion
occurred along a considerable length of cliff. The town has been developed on soft eroding
cliffs and annual falls & slips have left some properties, such as The Pines Hotel, very close
to the cliff top.
Coastal management issues: The potential impact of any coastal defence works on Swanages
tourism and the aesthetic and landscape quality of the coastline.
SEA WALL• Built in the 1920s and provided a promenade as well as a barrier to wave
attack.
The most cost effective method was found to be the replacement of the 1930s groynes and
replenishment of the beach sediment. A series of mainly timber groynes were installed in the
1930s, and eighteen of them have been replaced in 2005 with new ones. These reduced
longshore drift and help make sure that a beach remained in place to absorb the energy of
breaking waves.
Beach replenishment
In November of 2005, 90,000 m3 of sand was deposited on the beach. The beach will need to
be recharged with around 40,000m3 of sand every 20 years. This works with the groynes to
ensure a good size beach. The works were finally completed in June 2006at an estimated cost
of £2.2 million.
Cliff regarding: A series of steps were made in the cliff to reduce slope angles
However: January 1st, 2013Dorset Coastguard have restricted access toSwanage beach and
the South West Coastal Paths, after heavy rains over the holiday period caused further
mudslides and cliff subsidence in Swanage.
What are the effects of coastal recession on people and the environment?
Coastal recession=when the coast is eroded and retreats
Coastal recession at Happisburg
The effects of coastal recession on people and the environment. Amount of effect is
determined by the land use. Use for settlement>farmland.
North Norfolk coast
Managed retreat/Hold the line policies?
Managed retreat is an alternative to constructing or maintaining coastal structures. Managed
retreat allows an area to become flooded. Hold the (existing defence) line – to build or
maintain artificial defences so that the position of the shoreline remains. Use of hard and soft
engineering
Cliff recession along the North Norfolk coast
Why has The North Norfolk coast’s new Shoreline management Plan adapted a
managed retreat rather than ‘hold the line’ policy? Erosion has always been a problem on
the Norfolk coast because of its soft rock geology and its long fetch(Destructive/high energy
waves)High rate of erosion. Erosion rates are between one and three metres per year, so it
has become increasingly difficult and expensive to continue protecting certain locations -and
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trying to do so makes erosion worse in other areas along the coast. This will get worse as the
effects of climate change increase.
Predicted impacts on people: What will be lost to the sea over the next 100years?- Nearly
1000 homes- 1400 caravan and chalet parks- Six hotels and guest houses- Seven historic
buildings- 3.5 km of road- Seven golf course holes- Three community halls
HappisburgVillage Factors which explain high rates of erosion in this area:
Geology: Cliff made of soft rock (clay, gravel and sand deposited by glaciers)
No sea defences: 1958: use of revetments to reduce coastal erosion. From 1995 no repairing
of coastal defences high rates of erosion.
Government has refused to protect the village because it is not cost effective: the village is
less valuable than the cost of the defences to protect it.
Impacts on people
Loss of homes: Since 1995: 25 properties and the village’s lifeboat launching station washed
away.
Loss of value: Houses worth £80,000 when the coast was defended, are now valued at 1£.
No insurance of property against coastal erosion
Erosion-related stress and depression
Impact on the environment
Loss of land: At Durlston Bay near Swanage the cliff receded 12metres between 1968 and
1988. In 200/01 severe storms and high energy waves led to a further retreat of another 12
metres.
Loss of natural habitats: Durlston County Park also lies on the top and is home to over 250
species of birds that nest on the cliff. These habitats are threatened by cliff recession, which
can affect the breeding of rare species such as puffins and falcons.
Coastal flooding
Coastal flooding occurs when normally dry, low-lying land is flooded by sea water
Causes of coastal flooding
How are the effects of coastal flooding reduced by prediction and prevention?
Causes of coastal flooding
• Severe weather: Strong winds and storms which can increase the height of waves and tides
.• Storm surge: A storm surge is an offshore rise of water associated with a low pressure
weather system*, typically tropical cyclones. Storm surges are caused by high winds pushing
on the ocean surface. The wind causes the water to pile up higher than the ordinary sea level.
*A low-pressure area, low or depression, is a region where the atmospheric pressure is lower
than that of surrounding locations
• Sea level rise: Coastal flooding associated with sea level rise will become a significant
issue into the next 100 years.
How are the effects of coastal flooding reduced by prediction and prevention? This
should be studied through forecasting, building design, planning and education (see handout)
The Bangladesh Meteorological Department has three radar stations that transmit minute-byminute weather updates. The Bangladesh Disaster Management Bureau also issues cyclone
alerts through the national media as soon as a cyclone is detected by environmental satellites.
The Thames Flood Barrier The Thames Barrier is one of the worlds largest flood barriers
and serves to protect London from flooding during exceptionally high tides and storm surges.
The Barrier can be lifted at high tide to prevent sea waters flooding London 50