Wave cut platform
A wave-cut platform is a flat area of rock between the bottom of a cliff face and the sea.
It has been formed by erosion focused at a wave-cut notch which is an indent at the base of a cliff between the low and high tide mark
The erosional processes are abrasion, corrosion and hydraulic power.
Sub-aerial weathering also attacks the top of the cliff, weakening it.
Over time the wave-cut notch becomes bigger and cannot support the cliff
Therefore the cliff collapses
This leaves a flat area of rock at the base of the cliff
As time goes by the cliff face retreats as the platform gets larger
A stack is a column of rock which is seperate from the mainland.
Initially the sea eroded two caves in a headland which were back to back
Over time the caves became joined, creating an arch
Gradually the arch became weathered by the elements and collapsed leaving a single column of rock called a stack
The erosive processes are abrasion, solution and hydraulic power
A spit is an area of deposition in the sea which is attatched to the mainland and is hook shaped
it is formed by longshore drift which shifts the pebbles and stones down the coastline
This sediment is then deposited where there is a bend in the coastline
The hook, or recurve occurs due to winds from another direction adjusting the shape of the spit
Longshore drift moves the material because the prevailing wind forces the waves onto the beach at an angle
The swash takes the pebbles up the beach at this angle
Due to gravity, the pebbles go back to the sea perpendicular to the beach so overtime the pebbles are moved along the beach
Problems due to cliff collapse
- In Baton-on-Sea the cliff is collapsing and slipping into the sea leading to engineering works to stop the process
- People in the area have had high coucil taxes to pay for the work which costs over £10,000 per metre.
- The beach is also very narrow as the cliff has slumped into it which reduces enjoyment for the local people
- They are unable to have beach huts along the part of the coast meaning there is less tourist income
- On the top of the cliff, people have problems getting insurance for their houses as their buildings are in danger of falling into the sea
- Caravans in the Naish National Park are moved away from the sea each time the cliff collapses, therefore increasing the density of the people in the resort. Which, in the long term will affect the income for the owners
- The council also has to warn people off sections of the cliff after periods of heavy rain
- They had to fence off parts of the cliff near Hoskin's Gap in 2008 to reduce any accidents
- This has lead to the park getting smaller
- Over time it will effect the facilities open to the public
Vegetation in a coastal habitat
Sand dunes have vegetation adopted to a coastal habitat. On the smallest dune which is closest to the sea it is very salty and there is little fresh water.
This is called an embryo dune and important plants are the sand twitch and sea couch grass
These grow very close to the ground so the do not suffer too much from wind damage
The sea couch has waxy leaves which help it to store water and this also reduces transpiration
The next dune inland is the yellow dune. The main plant here is marram grass which has adapted to the difficult conditions.
It has deep tap roots which help it find the scarce fresh water. its roots spread over the sand and help to stabalise it
The leaves also curve inward which helps reduce water loss due to the harsh winds
The final series of dunes are called grey dunes which are older and slightly less harsh. Heather grows here which develops well where there are few nutrients as it has nitrogen-fixing bacteria in its roots. Its small leaves also reduce transpiration in these windswept conditions
Sustainable management of a coastal habitat
Studland is a sand dune area which is managed so it can be used today but will last into the futurer. The problem is that if the marram grass gets removed there can be a blow out where the wind is able to reach the sand because there are no plants holding it together. The wind blows it all away
BBQs are banned as these can burn the plants. The rangers let damaged areas recover by fencing them off so that people do not walk on the plants
The visitor centre tells the people about the plants and why they need protecting - this educates people and they can tell their children about the problems
Fire breaks have been cut out throught the gorse, this is to hep the grey dunes which are held together by plant roots.
People are not allowed to park on the dunes as this would damage them. Instead there is a large car park
The rangers are also worried about the large numbers of rabbits and are investigating ways to prevent breeding as these animals eat the plants which stabilise the dunes. Sheep are also not grazed on the dunes
Changing sea levels
Sea levels may rise in the future due to global warming. In the next 50 years, global temperatures may rise by up 2.5 degrees.
This could cause glaciers and the ice caps to melt. This extra water would flow into the seas and the levels would rise
Some coastal areas would be flooded.
Temperatures may be rising due to the burning of fossil fuels such as coal and oil which release carbon dioxide into the atmosphere which is a green house gas
Solar radiation is able to enter the atmosphere but some of the heat is held in a blanket of green house gases
If these increase, there will be more heat trapped in the atmosphere causing temperatures to rise
However some people think that the rising temperatures is due to the increase in solar activity and climate change is a natural event
Impact of rising sea levels
London is at sea level and te River Thames could flood the city if sea levels continue to rise.
Today the Thames Flood Barrier is raised if there is likely to be a high tide.
However the barrier may need to be increased in height which would be very expensive. The area either side of the barrier would also have to be protected
it is difficult to know who would pay. Council taxes would have to be raised if local people were made to pay yet this is a political problem. If London flooded there would be many important buildings damaged such as the Houses of Parliament.
If Canary Wharf flooded it would have an important impact on the economy as many banks are located there.
The problem for the environment of flooding is that the soil would be damaged by the salt in the water which would kill many plants such as the plain trees
Also, floodwater sewage would kill fish and hamper spawning
Costs and benefits of hard engineering
To proceed with hard engineering people must weigh up the costs and the benefits.
At Barton-on-Sea hard engineering is used to protect the cliffs from slipping into the sea.
the problem with hard engineering is that it is very expensive .
It can cost £10,000 for a metre
At barton-on-sea they have built groynes to keep the shingle on the beach and they have used rock armor to protect the base of the cliff from waves.
The question is who sould pay?
Some people say it should be those who live in the town; others say it is the visitors to the beach
Some say it is the Cliff View Hotel - however the problem is that the cliff is likely to collapse anyway and spendin money will not stop it happenning however it will delay the event which is a benefit
Another problem is the hard engineering is very ugly and the beach does not look natural affect property price and tourist income - though this will occur with cliff collapse
Costs and benefits of soft engineering
To proceed with soft engineering, people must weigh up the costs and benefits.
At Freiston Shore, Lincolnshire, soft engineering has been used. In 2001, the sea bank was removed and the tides were allowed to flood the area
As the land was only used for farming, the loss of land was not a massive problem
Marsh creation is an inexpensive way of managing the coastline if the land is cheap
Nobody has lost their homes and no businesses have been closed so there was no negative social or economic impact
Even if the coastline had been protected with sea walls, the land would have been lost eventually
A benefit of this approach is that the new land has become a bird sanctuary run by the RSPB
It is now an important site for ringed plovers
Another benefit is that the 66 hectares of salt marsh absorb wave energy and protect areas further inland from being flooded