Case Studys

Coastal Management

Fairlight Cove

In 1990 a scheme was built to protect the village and consisted of
· 50m long rock revetment at the base of clay and mudstone cliffs.
· Built to absorb energy of waves
· Cost £2.5 million
· 70% paid by MAFF
· 30% by local council

At first the council decided that it was not economically viable, and that only 5 houses were at risk in the next few years. The council experts suggest that a stable bay would form in 100 years naturally, and that people knew the dangers when they bought the homes. It would cost local people £0.7million and most were not affected by the erosion.

The Fairlight Coastal Protection Society was formed. They stated that
· erosion had increased due to the Harbour works and protection works at Hastings 5km to the east, in spite of the gate that was later built to reduce it.
· The FCPS estimated the loss of 57 houses in 100 years [most of which would be lost in 75 years after the end of the life of this scheme.
· Inflation was included in the value of these homes [ there was a recession of prices at the time]
· Roads would need to be replaced as would sewers, water and an electricity sub station

Tides

1. Some places , such as Southampton have two high tides each cycle . Water flowing up the Channel diverts around the Isle of Wight so some of the high water arrives a short time after the main high water.
2. The range may depend on the shape of the Coastline. The range is very low in the Mediterranean as all the water has to pass through the narrow straits of Gibralter. The greater ranges are in funnel shaped areas such as the Bristol Channel [Avonmouth 13m ]and the Bay of Funday, Canada. As water has to fit into a narrower and narrower channel tidal bores may occur at spring high tides, e.g; the Severn bore which can flow at 30/km/hr towards Gloucester.
3. The more water moved the greater the tidal current. e.g. In the Bay of Funday where 100 00 million tons of water are moved per day. Most tidal currents are 2 -3 knots near the shore or less. They are not very powerful on the beach and rarely erode material.
4. Coriolis force is the result of the earth's rotation. In the northern hemisphere things are deflected to the right, so as the tidal water moves from the north down the North Sea water is deflected towards the British coast and gives higher tides on the English than the Danish coast.

Sea defence

BLACKWATER ESTUARY
This process is being tried on parts of the Blackwater estuary.
At Northey Island, the sea wall has been allowed to decay and the land
behind is flooded at spring tides. A new lower sea wall has been built on
higher land to protect the rest of the farm. The change has to be managed or
the tidal currents could suck out mud and not deposit it.
Near Bradwell on Sea, a break has been made in the sea wall to allow a
similar process to occur.
The salt marsh provides a new habitat for wading birds and other creatures:-
e.g. brent geese, curlew, shelduck, oyster catchers, crabs, cockles and
mussels.

JAYWICK 1986
Jaywick is on a low-lying part of the coast of Essex. just to the south of Clacton.
It was developed after W.W.I when many people from London bought plots of this land to build holiday homes. At first these were often wooden shacks with no mains water, electricity or sewage. The roads were unmade and some of them still are. Gradually the population increased and permanent homes were built behind the holiday homes [some of which were replaced by brick buildings]. In 1953 the surge breached the sea wall and flood much of the area. 35 people drowned and 600 were made homeless. The sea wall was improved after that ,but there has been minor flooding every year since and 1n 1978 and 1982 people had to be evacuated. 2000 homes plus chalets and caravans are in danger and the old sea wall was falling apart. The Anglian Water Authority was responsible so a study was carried out in 1985 when Middlesex poly kept a record of wind ,wave and tidal details over the year. A cost benefit study was done for the protection of 200 ha against flooding to a 1 : 1000 year standard. The findings were
Conditions that lead to most damage were
1. Largest waves[up to 2.5 m] from the N and NE hit the beach without refraction so there is longshore drift southwards.
2. Surge conditions affect this area when winds come from the N or NE.
3. Storm waves can move material up to 0.2mm up to 200 m offshore. In 1983 the entire beach near Eastness was removed in one storm and the wall had to be protected by rocks.
4. The loss of beach material means that the waves hit the sea wall weakening it.
5. The greater depth of water increases the strength of the waves.
6. Once picked up the tidal currents can remove the sediment as they flow over the beach. The tidal currents can reach 1m/sec which is unusually high.
Options;-
1. Conventional wall improvements £14.7 million
2. Beach recharge without breakwaters £11.4 million
3. Beach recharge with breakwaters £9.6 million
4. Do nothing [ not possible as lives were at risk ]
Benefit i.e. homes, caravans, tourist trade etc £13.6 million over 60 years

Cost : Benefit ratio = 1 : 1.4
Scheme chosen
Beach;- 10 m wide and the crest will be 1.3m above spring high tide so it will absorb all the wave energy. 180 000 tonnes of fairly coarse sand and medium at gravel was used as it is less likely to move. This had to be brought from the sea as local roads were too poor to carry the traffic. However some of it has moved downdrift between groynes. In the first year 6% of the sand was lost and all may need replacing in 9 years due to natural processes.The sea wall is 300mm above the beach to cope with the 1 : 1000 year surge level

Breakwaters ;- 300m long , built of large rocks[6-8 tonne] of Swedish granite that should not move in storms. They are built in a fish tail shape to refract the waves to limit longshore drift and to push the tidal currents off the beach, creating a protected beach cell. They are placed at the weakest points of the coast to give extra protection.

NE NORFOLK
The coast is made of glacial deposits which are easily eroded. Between 1838 and 1861 4m p.a. were lost. At Overstrand and Sidestrand are being eroded at 1m p.a. at the moment.
Reasons;-
1. Cliffs are 45 -60 m high with chalk between glacial deposits so slumping occurs in clay areas.
2. Local farm ponds drain water into the cliffs.
3. There is a 3000km fetch to the North which produces large waves that undercut the cliffs and transport the collapsed material.
4. The longshore drift carries material towards Lowestoft.
Problem
1. There is an increase in the local population.
2. Roads will need re-routing
3. Upset for local people who may loose their homes.
Work so far
1. Seawalls and groynes have been built at Cromer and Overstrand. The walls are built to last 100 years, but are expensive and only worthwhile for inhabited areas. At Overstrand the steep wall causes turbulence and scour ,which is undermining the sea wall.
2. Revetments were built at Trimingham in 1973 but were destroyed when the cliff slumped.
3. Revetments and 4 groynes were built at Sidestrand in 1985 at a cost of £1 million
4. Tube wells have been put into the cliffs between Overstrand and Cromer to drain the water away.
Options at Sidestrand
1. Revetments and groynes would decrease erosion by 50%
2. Beach nourishment
3. Nothing and forbid building within 1 km of the cliff

MAPPLETON
Mappleton is on the Holdeness coast and the cliffs are made of boulder clay and were eroding very quickly. The village was in danger, and several houses had been lost. However the B1242 road link was in danger and this made it economically viable to build sea defences. An offshore bar of granite was built at the cost of £ 2 million. This prevented erosion at Mappleton but prevented material moving southwards.

At Cowden erosion was less than 2m p.a. until the Mappleton defences were put in place . In two years, an acre of land has been lost, and the coast has eroded 80m.
Sue Earle's farmhouse was knocked down in 1997 as it was at the cliff edge and was considered dangerous. It cost the Earle's £3000 for the priveledge. They are now suing in court.

MAPPLETON
Mappleton is on the Holdeness coast and the cliffs are made of boulder clay and were eroding very quickly. The village was in danger, and several houses had been lost. However the B1242 road link was in danger and this made it economically viable to build sea defences. An offshore bar of granite was built at the cost of £ 2 million. This prevented erosion at Mappleton but prevented material moving southwards.

At Cowden erosion was less than 2m p.a. until the Mappleton defences were put in place . In two years, an acre of land has been lost, and the coast has eroded 80m.
Sue Earle's farmhouse was knocked down in 1997 as it was at the cliff edge and was considered dangerous. It cost the Earle's £3000 for the priveledge. They are now suing in court.

FAIRLIGHT COVE

This grew up in the interwar years with holiday shacks being built at first. These have been replaced by brick buildings and many retired people have moved here.In 1990 the average price was £100 000.

The cliffs are a mixture of clay with siltstone/sandstone beds and erosion is especially fast along the fault lines.
Between 198 -87 the cliff retreated 1 - 2 m per year, but the rate is increasing as clay is being exposed at the base. Some places have experienced more rapid erosion and since 1984 one house has lost 32 ft of their garden. Four coastguard houses have gone and others have lost their gardens. One house was rolled back 40 ft to prevent its loss. Forty six houses will be lost in the next 100 years.

Date of survey distance in m from grid ref

Local residents state that the sea defences at Hastings 5 km to the west have increased erosion by trapping sediment by a large groyne system and harbour wall. A sediment gate has been opened in the terminal groyne.

Processes
1. Slumping of the clay cliffs
2. Mudflows down the face of the cliff
3. Undercutting of the base by the waves

Schemes
1. Offshore rock bar which would protect 11 houses for 75 years at a cost of £2 million
2. Artificial beach and groynes for £10 million
3. Sea wall to save 35 houses for £10 million

Council argued that only 5 houses would be protected in the next few years and that the cost was greater than the benefit. They said that it would mean a 17% increase in the rates or no spending on council house repairs in order to pay for it. They felt that people knew of the danger when they bought the houses. A survey shows that in the next 100 years a stable bay will be created between the fault lines and erosion will become much slower. They argued that natural processes should be allowed to take their course.

Residents association commissioned another cost benefit analysis to make their case. The benefits included
1. A greater rate of erosion was expected so more homes 57 in 100 years would be lost
2. At that time they expected house prices to rise quickly [they actually fell].
3. Roads would be lost and need replacing
4. The sewer works would need replacing
5. The water ring main would need replacing
6. The electricity sub station would need replacing
7. There were intangibles that could not be quantified
· risk to life
· loss of recreational use
· stress and anxiety
· landscape loss
8. Once the erosion reach the stream it will cascade over the cliff increasing the rate of erosion.
the .
Residents association estimated the total benefit to be £2 - £3.5 million
They, also, suggested that the cost could be reduced to about £1.5 million This made the cost benefit analysis 1:1.4

The cliff at Farilight Cove was a geological Site of Special Scientific Interest, so some erosion had to be allowed in order to expose the cliff face.
After many years of argument, the rock offshore bar was built in 1990

BARTON ON SEA
Barton on Sea is built on a cliff of clay under sand, and this has eroded rapidly[ 1m p.a.]. This was the result of
1. A high energy wave environment with large waves from the SW. The waves create an under tow that removes beach material. The cliff is undercut and slumping occurs.
2. Longshore drift from W to E.
3. Dredging offfshore starves Barton beach
4. Groyne systems to the west starve Barton beach
5. Sub aerial processes affect the face of the cliff e.g. wind action and run off.

In the 1960's the New Forest council built a scheme based on drainage of the groundwater and protection of the cliff foot by rocks and steel piles. This scheme cost about £ 1 million and protected about 1800m of coast by 1968.
For a while people were confident and even extended their homes, but in the 1970's the cliff became unstable and erosion began to occur at the foot of the cliff. Too little material was being brought from the west to create beaches that would protect the cliff and the sea defences.
In Feb 1974 a bad storm occurred which breached the revetment and saturated the undercliff,damaging 200m of the cliff foot defences. During November the cliff began to collapse pushing some of the sheet piles seawards and allowing the revetment to collapse. the scheme was designed so that the different parts depended on each other to work and if one part was broken the rest could not function. During the spring of 1975, more erosion took place and several houses were lost.
To repair the defences would cost £166 000and this might only last a few years. Geologists were against the stabalisation of the cliff as erosion exposed fossils of the Tertiary era and it was a site of international importance as well as an S.S.SI.The attitude of the council and engineers changed and they began looking at soft not hard defences. Beach nourishment is now used to absorb the energy of the waves. The top of the cliff will be allowed to retreat until it is at a sustainable angle.

COST BENEFIT ANALYSIS
This was done after the scheme was built.

Note :-
1. Would this solution have been considered if a cost benefit analysis had been done before. {Remember the government will only pay 50% if the cost is less than the benefit}
2. The benefits were counted on maximum recession that was possible.
3. The interest rate assumed was 10%.
4. The recreational value was worked out as
number of visitors x distance travelled in cost terms
5. Should you use the property value with or without the scheme in place.
6. How do you value an SSSI , the scenery or the upset to local people [there is no
compensation for loss of land/home by coastal erosion]
7. What will be the cost of the scheme elsewhere e.g. if this eroded material protects
another site will there be increased erosion if the scheme goes ahead.

LATER DEFENCES

Since 1974 the wooden groynes have been replaced with seven rock strong points about 400m apart. These are more able to resist storm waves.
The old timber revetments were replaced by a 1.8 km long rock revetment in 1991 at the cost of £4.5 million. [ designed to last 30 years]. New fan shaped drains were put in the cliff in 1995 and some of the cliff has been regarded to make it less steep. The free face of the cliff will be allowed to retreat by weathering until it is stable.
The cost since 1987 is £ 4.5 mill
No defenses have been built at Naish farm to the west as the cost benefit analysis was 6:1. The site is an SSSI and the geology and fossils are of scientific interest, so it must be exposed. The erosion at Naish farm provides sediment for Barton and Hurst Castle spit.
Since 1954 Hurst Castle spit has been beached several times and it has moved 100m inland since 1898. The spit has been protected at the proximal end with rock armour and the crest ridge has been widened to 6m with a1:3 slope. The increase in breaching may be the result of the protection of Barton on Sea as there is less sediment moved by longshore drift.