There was also a wave cut notch and a chalk overhang visible created by under-cutting at the base of the cliff; both features displayed signs of weaknesses because I could see cracks. All the cracks would be enlarged by hydraulic action mainly.
The brown stains on the cliff were caused by the clay at the top of the cliff being washed by surface run-off. This clay is being weathered also, visible because of a difference between the cliff angle and the angle of the clay. There is only about 30cm of clay soil at the top, with very little vegetation.
This cliff also has faults and flint layers. As well as having many bedding planes which are lines of weakness and thus this is where the cliff is most likely to collapse from in the future. There is also an algae mark on the cliff which shows the mean high tide mark.
The height of the cliff was calculated by taking the number of steps down to the base of the cliff from the top. Each step was 16cm high and there were 172 of them, so the cliff is 27 m. I estimated the angle of the cliff to be about 85°; because it was constantly being eroded at the base by the sea.
There are no coastal protection schemes in place, yet a nearby housing area in the future could well be at threat.
Newhaven West:-
This cliff is also inactive; however it was active at one stage because there is no cliff protection and cliffs to the west of this site are being eroded rapidly by the sea. This change is due to a man made infrastructure- a harbour wall to shelter Newhaven’s port. This has caused debris to collect in front this cliff which has been eroded from western cliffs and transported by longshore drift easterly because of Britain’s prevailing winds.
However there are remains of an old groyne which was to stop the movement of beach material along the beach (longshore drift) into the port prior to the harbour being built.
There is evidence of mass movement at the base of the cliff. There are large boulders of sandstone (results from grains of sand being compressed and cemented together-sedimentary rock) which have fallen from the top, because this is where the sandstone is located. There are also some smaller chalk ones. These boulders had fallen some time ago as they had now been weathered and were rounded. The boulders were probably subject to chemical weathering (eg salt spray), physical weathering (eg freeze thaw) and biological weathering (eg vegetation and animals). Some vegetation has grown at the base of the cliff, eg grasses, small shrubs and plants. This vegetation holds the ground together at the base of the cliff.
Because of the presence of the habour wall a pebble beach has been made protecting this cliff; although it being eroded and the pebbles are becoming rounder and smaller the beach is being replenished naturally by the cliffs to the west of this site.
The faults on the cliff show that is was once under huge pressures. The brown stains on the cliff are most likely to have come from the sandstone at the top being washed down. However these brown stains also show that the cliff is not really being attacked by weathering or erosion otherwise it would become whiter in appearance.
The flint layers show that the cliff was built up in layer then metamorphosed into the present day chalk. There are also many very close bedding planes on the sandstone that show is was deposited over a period of time. There is a fine seam of shells, which have been deposited high up. The sandstone is very weak and can be easily weathered. This is probably caused grass growing on it and thus the roots growing into the sandstone causing it to break up; this is an example of biological weathering.
I estimated the height of the cliff to be 20m.The angle of the cliff varied and but it was overall between 80° and 90°.
Newhaven East:-
This is an inactive cliff. It is behind a man-made harbour wall and so is protected from the sea. This means that the only process attacking the cliff is weathering. There are many types of weathering on this cliff. Biological weathering can be seen from the bird holes in the cliff and vegetation growing on the cliff. There are also rabbit holes at the base of the cliff; the many series of tunnels could make it unstable. Both rabbit and bird dropping are visible, and they cause chemical weathering; however this makes only a very small proportion of the cliff being weathered.
The angle at the base of the cliff suggests that mass movement once took place here and so formed this gentle slope consisting of soil and debris, on which has grown vegetation like bramble bushes, grasses, plants and other low shrubbery which can withstand salty conditions. The top and bottom of the cliffs have the same gradient of about 45°; the middle part has a gradient of about 80°. The top has been weathered. The top is also a different stone to the rest- sandstone, which is why it is easily weathered.
Then just below this is an oyster layer, alongside flint seams. The oyster bed, which was deposited when the cliff formed under the sea millions of years ago, is stronger than the chalk and so can hold steeper angles because it is not weathered as quickly. The sandstone has left brown stains down the chalk part of the cliff (middle) due to surface run-off of rain.
There is also cracking near the top this is most likely to be salt-weathering and the effects of freeze-thaw, when water seeps into cracks and then freezes and expands by 9% thus enlarging the crack. I estimated the height of the cliff to be about 30m.
There is a sea wall, car park and small patch of land with gentle relief. This has protected the cliff, and kept cliff retreat to an absolute minimum. Weathering is just decreasing the angle of the cliff steadily.
Rates of Cliff Retreat
I worked out the cliff retreat rates by making a line at right angles on a map supplied to m, which showed where the cliff had retreated to in stages over different time periods. I used the scale to convert my measurements in centimetres into metres. I took many markings to work out a reliable average result of cliff retreat.
Past 1873-1976
Future 1976-2100
Analysis of Cliff retreat rates
The erosion rates from the two time periods are extremely different. In the past, the maximum of the mean cliff retreat rate per year reached 0.5m, but in the future it might only reach 0.3m a year. This is because there are weather events that are abnormal. For example, there may have been an exceptionally strong storm that caused a lot of cliff erosion. And vica versa, there may have been an unusually calm year, in terms of weather. These events can dramatically change the cliff retreat rates; and so it is very hard to estimate how much a cliff will erode over a long time period.
The past one is more accurate than the future one. As the future one cannot take into account storms and protection work that might be done. It can also not really take into account the different strengths in the rocks, which may cause it to withstand more erosion and weathering. Furthermore, global warming will cause sea expansion which will undoubtedly lead to a rise in the sea levels, thus more of the cliff is under threat from erosion. There will be more extreme weather patterns with global warming; this may make it harder to understand the weather patterns and forecast what weather we will experience, making the decision to protect a cliff even harder.
Problems of Cliff Retreat
If a cliff retreats too far back inland, then there are problems which arise. One of the main concerns in East Sussex is the loss of the main coast road, A259, which links large villages (Rottingdean, Saltdean, Peacehaven etc) along the coast with Brighton. At the moment this road is literally metres from the cliff and may well be at threat in the foreseeable future. This would mean the A259 would have to be re-routed. This would either force the new road to go through built up areas of residential housing or through the South Downs. Both of these would be a huge problem. Because Brighton is already a linear settlement it would be hard to find a suitable route through the city. Furthermore, the South Downs in an ANOB (an area of outstanding natural beauty) and also a registered National Park. This would make this task highly difficult to accomplish. Many would argue that a major road through the South Downs will cause environmental concerns, increase the risk of further developments on the rural/urban fringe and also some will say that there are already many busy roads criss-crossing the South Downs, such as the A272, A23, A22, so why build another one?
Cliff retreat would also put a lot of farms at risk; and this decrease in agriculture would be catastrophic for the local economy and the people relying on the farm either for produce or wages. On the stretch of the Sussex coast there is mainly pastoral (cattle, sheep etc) because the conditions are not vary good for arable farming (crops) on the top of cliffs due to salt spray and high winds. When mass movement of a cliff occurs then animals are at harm of falling to their death; and fences would have to be re-built. This causes great distress for the farmers.
However, I believe there are greater things at risk. Amenities, such as phone lines, gas and water pipes and electricity cables can be destroyed by cliff fall. This causes the lack of amenities for many residents of settlements for sometimes long periods of time resulting in much inconvenience. The re-location of these amenities costs a lot of money. This also means that housing will be at risk and thus face another problem of cliff retreat. A home-owner may find it extremely hard to get insurance on their house if they live close to the sea. In addition, house prices will fall dramatically because no-one would want to buy a house that will most likely fall victim to cliff retreat in the near future. And in the worst case scenario, a home-owner may lose their house; this is not a rare occurrence. Houses in Peacehaven and Telescombe (near site 1) will fall into the sea soon, however some coastal protection schemes are underway to prevent this, which costs a lot of money.
Tourist attractions and other facilities are also at threat. These attractions include Newhaven Fort (near site 4), Seaford Head golf course (in previous years the 18th course has fallen into the sea), many coastal paths etc. The loss of these may cause a reduced local income, a loss of an important historic site and the loss of recreational areas, which provide great enjoyment for the local community.
In the past in Sussex, there has been numerous cliff collapses. There was one in Seaford, during July in 1986. This was near the Seaford Head Golf course, which is now getting nearer and nearer to the sea. Also, a couple of years previous to now, a section of the cliff behind Brighton Marina fell. This resulted in a lot of work being carried out to protect this weakened area. Events, such as these, highlight the importance of coastal protection.
An article highlighting the importance of cliff and coastal defences. Unfortunately, this incident ended with a fatality.
Solutions
The cliffs in Sussex are primarily chalk; however in Newhaven there is a stronger presence of sandstone. This means that the chalk cliffs, which are a soft sedimentary rock, are quickly eroded if by the processes of weathering and erosion. This means there is a lot of cliff retreat. So to slow this action down many methods can be employed; which solution we use depends upon many factors, one of them being money. There are two types of coastal protection: - Soft Engineering and Hard Engineering.
Soft Engineering: - aims to dissipate wave energy by using natural coastal landforms. In this way, coastal defence works in consideration with natural processes of the local environment to help achieve an active equilibrium with the surroundings. The following strategies that can be used fall under this category:-
- Managed Retreat:
This is when not really any action is taken to protect an area but instead the rate of the retreat is watched and how far it has retreated. It is usually said that the area will be allowed to erode up until a certain point and then it will be defended. This is normally used in areas that are considered to have a low economic value, where the sea is allowed to erode and flood areas of coastline. It encourages the growth of beaches, which are a type of natural defence; and salt marshes, which are extremely important for the environment as it makes a sustainable ecosystem. However, some people will be forces to move and have to be funded by the government for the loss of housing and farming land. However, this technique is not useful in Sussex due to the nature of the shorelines.
2. Beach Replenishment Scheme:
This is where beach material is replaced to where it used to be. Because of erosion and the process of long-shore drift, beach material is transported from its original position along the beach and if the beach is not naturally replenished then that stretch of coastline is open for an increased rate of erosion and retreat. This scheme rebuilds up the beach, which provides a good natural buffer against the waves. This method can either be done by using trucks and diggers transporting sediment from one end of the beach to the other, or it can be done by using a special dredger that digs up sediment from the sea and pumps it via a pipe to the shoreline. However if the beach material is imported from a completely different area then the material may be unsuitable for this particular area. For example, I heard on the news a while ago that imported material (like stones, rocks, etc) from Egypt and Africa have insects trapped up in then and they are causing problems to the UK’s ecosystem. This scheme has been used at Seaford beach, Sussex, because the beach was “starved” of material due to the harbour wall: and it has proved highly successful.
This strategy usually cost £8,000 per 100m per annum.
Hard Engineering: - this strategy is normally employed in areas that are heavily populated and are considered to have a high economic value. In addition they normally have a high impact on the landscape. It is the most common strategy and usually costs more, but is very effective.
These are one of the oldest and best known methods. This is a barrier/wall built at right angles to the sea. This is situated in this way so that it slows down dramatically the process of long-shore drift and thus the transportation of beach material away from the beach leaving it exposed to further erosion. This is a very common technique as it is very good, because the beach material can absorb the impact of the waves, in its purpose and relatively cheap. However, if long-shore drift is insufficient this may cause down-drift starvation, causing more problems. This technique has been used along the Sussex coastline. This strategy costs £30,000 per 90m and only lasts around 20 years.
This solid impermeable wall reflects the waves back out to sea, rather than the traditional sea wall which the waves go over. The ramp absorbs the wave energy evenly. This is a very expensive method. There are also two other types of sea wall. These are two main types of seawalls a concrete one and a steel sheet one. The concrete one is often reinforced with a steel frame inside for added strength. The steel sheet one has interlocking steel sheets driven into the ground and then backfilled to give it more strength.
This type of coastal protection will cost about £600,000 per 100m and there are high maintenance costs of £5,000 per year for 100m of curved sea wall defences.
A vertical sea wall has a cheaper installment but very high maintenance costs and is less effective as a form of coastal protection.
Gabions are free-draining walls constructed by filling large baskets with broken stone. The baskets are made from galvanised steel mesh, woven strips, or plastic mesh. A typical basket is rectangular with dimensions of about 50 cm by 15 cm. They are really good as they are flexible so can absorb the force of the waves. But once the wire mesh breaks they are not really any use as the material inside starts to fall out and so they no longer do their job.
This is a relatively cheap method.
Gabions
These are large blocks of rock emplaced as a permeable ramp. They are usually graded in layers with the largest and heaviest on the exposed surfaces, taking the full force of the waves first. However, this strategy may disrupt long-shore stability.
It cost £132,000 per 100m of shoreline.
Cost Benefit Analysis
This is a basic characteristic of a coastal protection scheme. It is most easily described by applying its theory to an example. For example, if the proposed coastal protection is going to cost £4 million and the value of the area at risk is £2 million, then the “do nothing” approach should be taken. However, if the area at risk is worth £6 million then the scheme is worth undertaking. This is why most of the coastal protection schemes are near towns or large villages. An example of the “do nothing” strategy is at Birling Gap, in Sussex. This is because it is only a hamlet of a short row of houses; even though many houses have already fallen victim to cliff retreat. This theory is usually calculated as an equation. When the cost benefit ratio is above 1, the strategy is deemed economically suitable.
Money Saved
Cost of Protection
However the costs of all of these defences are very variable and so a true coat benefit analysis cannot be carried out as there is no specific site.
Managed retreat is certainly the cheapest but it does not actually protect the coast. Gabions and Tetrapods are cheap for what they do but are not suitable for all jobs as they only will disperse the energy from waves, not completely stop it. Groynes are very expensive for what the actually do as they do not directly protect the coast all they do is hold beach material in place so that is stops erosion. That is why I think that seawalls are the best for what they do although they may need to be used in conjunction with Tetrapods or other energy distributors.
Questionnaire
We carried out a questionnaire to see what people thought about what was being done to protect the coast and what they thought needed to be done. This included opinions on certain factors of coastal protection.
I thought up some suitable questions which I then put into a questionnaire; which generally had multiple choice answers so that the data collected was easier to tabulate.
Here is the questionnaire:-
Coastal Protection Questionnaire
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Gender:- male female
◻ ◻
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Age:- 18-25 26-35 36-50 <50
◻ ◻ ◻ ◻
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Where do you live? Inland ◻
Coastal ◻
- How much money do you think is spent on coastal protection?
Too much ◻ Enough ◻ Not enough ◻
- Do you think we should protect the coast?
Strongly yes ◻ Yes ◻ Maybe ◻ No ◻ Strongly no ◻
- Is the nearest coast to you defended?
Yes ◻ No ◻
- Who should pay for the coastal protection schemes?
Government ◻ Local councils ◻ Local Residents ◻
- Do you think there is enough done to protect the coast?
Yes ◻ No ◻
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What should be done to protect the coast?
Groynes ◻
Beach Replenishment scheme ◻ Sea walls ◻
Nothing ◻ Rip-Rap ◻
Gabions ◻
- What do you think about the appearance of coastal schemes?
Attractive ◻ Reasonable ◻ Ugly ◻
Any other comments………………………………………………………………………. ………………………………………………………………………………………………………………………………………… ………………………………………………… ……..…………………………………………………………………………
Questionnaire Results
Questionnaire Analysis
The results of the questionnaire are very valuable to my project. It provided me with the information on what other people thought. However it only showed a small proportion of people, out of the whole country. Thus the results are not 100% accurate as an average; but they indicate certain things.
The majority of people thought that the Government should pay. They also believed that the coastal defences are reasonable in appearance. One of the posed questions was: “do you think we should protect the coast?” and in response the majority of people believed yes, we should protect the coast. Furthermore, exactly half of the people I asked thought that not enough was invested into sea defences. This is no surprise as many houses in Sussex are extremely vulnerable to cliff retreat in the near future.
Seawalls were thought to be the most effective at protecting the cliff; closely followed by groynes. Most people though that the government should pay for the coastal improvements. Basically everyone believed that the appearance of coastal schemes to be reasonable and a few thought them to be attractive.
My Solutions for the Sites
The only cliff, that we studied, under any real erosion is the one at Peacehaven. Although Newhaven West may suffer from erosion in a few years time due to long shore drift moving the beach material away from the cliff. However to stop this, a couple of groynes could be installed and maybe a system of beach nourishment could occur, so that this particular area stays roughly the same. There is no real risk for people of collapsing cliffs in the near future, so it is no immediate action is urgently required.
At Peacehaven there is no immediate defence in place, apart from a sea wall just to the West of this site, giving a bit of shelter. However, the majority of this area is left to erosion because all the material and debris eroded is quickly transported by long-shore drift. At low tide the wave-cut platform is clearly visible; and on this, I propose to place some groynes starching along the quickest eroded places, so that beach material is collected and acts as a natural absorber of the sea’s energy. Furthermore, pebbles and large stones should fill the gaps in between to start the collection of material and prevent erosion of the cliff at the first installment. My estimation of price is around £1.9 million pounds.
I believe this to be the best strategy. The only other option is extending the sea wall from the West of this site. However, I think this is too costly and not cost beneficial; because there are not many houses or other structures at immediate or later risk. At the moment a gentle approach is suitable.
It would depend a lot on how much money there was to spend. If there were unlimited funds, then extending the seawall and creating a beach with groynes would be the best thing to do, as it would give a distinct result. But it would have to be extended for a few hundred metres otherwise it would not be worth it, this would cost more than £6 million, saying £3.5 million for the seawall, £1.5 million for groynes and £1million for the beach. This is a very expensive strategy to protect the cliffs, when some thing that is cheaper and equally as feasible, could do the job just as well. Money is constantly the main matter.
But whatever is decided, there will be at least one person who will oppose this action. This would affect many different groups or people in very different ways. The council would be the committee making the choice on what is to be done or not done in some cases; although there may be a few outsiders aiding. This could lead to partitions from local residents about the change, they could be for either argument- yes “we want it because we are under threat” or no “we don’t want it because it will spoil the beautiful scenery”. The latter generally will be received from all environmental groups, such as Greenpeace and Save the Planet. The local contractors would be happy. Local residents may be disrupted while the work is carried out i.e. roads may have to be closed, water pipes and electricity cables moved etc. What is more, the village may be affected economically and be forced to increase local taxes to cover their expenditure.
Also there is the problem that if the cliff is just left to retreat, then people will have to move out of their homes. They will not be able to sell them and they will get no compensation, this will particular effect elderly people who might not have enough money to move elsewhere or do not wish to move from there home which they have lived in all their life.
What Lewes Council have done towards Coastal Protection
Taken from Policy Statement on Flood and Coastal Defence
“Government’s Policy Aim
To reduce the risk to people and the developed and natural environment from flooding and coastal erosion by encouraging the provision of technically, environmentally and economically sound and sustainable defence measures.”
The council want to get involved with the South Downs Shoreline Management Plan, the Local Environment Agency Plans and DEFRA for this area.
“Assessment of coastal erosion risks
3.14 As identified in the Shoreline Management Plan, Lewes District Council has direct responsibility for 9.7km of coastal frontage. All of this is chalk cliffs¸ overlain in places by more recent deposits. Within this 9.7km of frontage, some 2.8km (in Peacehaven and Telscombe) is defended against erosion by concrete walls and groynes.
3.15 The risk of erosion along defended frontages is low, provided existing coast defences are well maintained. However, even in defended frontages, cliff faces are subject to weathering and instability. The extremely wet weather of autumn 2000/winter 2001 led to a number of cliff falls. The District Council carried out a programme of remedial cliffs stabilisation works in spring 2001, in the interests of public safety.
3.16 The risk of erosion along undefended frontages is higher with erosion rates of up to 0.4metres per year (See 1997 SMP for details). Most undefended frontages in Lewes District comprise undeveloped open cliff tops, as at Seaford Head and between Peacehaven and Newhaven.”
“Action to reduce or manage coastal erosion risks
3.17 The District Council is a partner in the Regional Monitoring Programme for the coast between Selsey Bill and Beachy Head, and the Channel Coast Observatory, a consortium of partners around the coast from Dorset to the Thames Estuary.
3.18 The District Council monitors the condition of those coast defences for which it is responsible every six months.
3.19 The Environment Agency monitors the condition of Seaford Beach and carries out an annual programme of beach recycling and reprofiling and, if necessary, recharge to maintain its integrity. The Environment Agency also carries out any necessary emergency works following storm events.
3.20 Our management programme takes into account the most recent predictions of climate change as set out in the 1997 Shoreline Management Plan and the approved Coast Defence Strategy for Saltdean to Newhaven/West Breakwater. Preparation of a Coast Defence Strategy for Newhaven to the Cuckmere is underway, led by the Environment Agency. An initial Scoping Study should be published by spring 2004.”
Taken from:- Draft Coast Defence Strategy for Saltdean to Newhaven
(West Breakwater): Executive Summary
“3.3.2 Conclusions
Seawall
The seawall along the full 2.5km length is in a good condition apart from a few localised areas listed below:
i) Limited undermining of the toe of the seawall between Groyne 9 and the adjacent access step to the east.
ii) Abrasion of the seawall face between Groyne 11 and Groyne 12 plus undercutting of the steps immediately to the west of Groyne 12.
iii) The access steps immediately to the west of Groyne 14,15,16,17,18 and 19 have been undercut through abrasion.
Groynes
Most of the groynes are in good condition, however, the foundations of many of the groynes have been undermined. These structures require immediate attention to prevent the structures from toppling over. The groynes which require immediate attention to their foundations are Groynes 1, 2, 3, 4, 5, 6, 9, 10, 11, 12, 14, 15, 16, 17, 18 and 19. The groynes exhibiting the worst undercutting are Groynes 3, 4, 6, 9, 10, 14, 15, 16, 17, 18 and 19. In addition to the undermining of its foundation, Groyne 19 has lost a concrete slab from the top of the groyne.”
This information talks about the coastal defences, between Saltdean and Newhaven, and there need for maintenance.
This is parts of the report on coastal defences, from one of several policies concerning this area:-
“4.50 The result has been the reduction in the natural protection against the erosive force of the sea, the most extreme example being the total loss of the natural beach at Seaford. The effects of global warming; rising sea levels and increased storminess, are expected to strengthen the attack in the future.
4.51 Many of the defences against erosion or flooding have traditionally been ‘hard engineering’ works, such as walls and groynes. However these are initially expensive and utilise large quantities of raw materials for concrete etc. More recently natural ‘soft engineering’ techniques, such as the beach replenishment at Seaford, have been preferred. Nevertheless all methods require increasingly costly maintenance to maintain protection. Therefore, Government has promoted the strategic review of the future protection of natural coastal 'cells' to determine through Shoreline Management Plans [SMPs] where to continue to invest in intervention, and where to let nature take its course. The SMP, incorporating the Lewes District, has been prepared for the coast between Selsey Bill and Beachy Head.
4.52 The SMP subdivides the area into 'management units' which correspond with features such as urban boundaries or rivers. The defence options available to this District are ‘hold the line’, which implies continued maintenance of protection, or ‘do nothing’, i.e., let nature take its course. The District Council has agreed to a set of sustainable strategies for the management units which, in essence, maintain defence of urban areas, and let natural processes prevail on the undeveloped coast.
4.54 Accordingly the District Plan allows development where tidal and cliff protection is already provided, with provisos relating to the protection of life and property where there is a residual tidal flood risk. Where such protection is proposed, but not yet in place, development which would increase the risks will be resisted until the works are provided.
4.55 However, where there is and will be no protection from flooding or coastal erosion, development will not be permitted which would put lives and property at risk within the foreseeable life of the development. Neither will development be permitted which would by itself at any time give rise to the need to carry out protection works.
7.20 The undeveloped coast in the Lewes District is worthy of protection. The cliff area between East Saltdean and Newhaven is amongst the only remaining stretches of undeveloped down land cliff top in Sussex, although some defence works have taken place and investigations into the feasibility of further works have taken place. Much of the marine and littoral areas and cliff top areas are rich in flora and fauna, specific to a particular area. The cliffs between Newhaven and East Saltdean are protected as Sites of Special Scientific Interest, primarily for the geology of the cliff and the foreshore.”
I have highlighted the text of these reports which I believe to be important and relevant to my project. In a summary, these reports say that there are certain areas which they will protect and areas which they have the responsibility to maintain as they are under their own “jurisdiction”. There are also other parts to these reports that say that they are not likely to protect the area between Peacehaven and Newhaven; due to the cost benefit ratio. Furthermore, this is partly due to scientific research; because they want to keep some of the cliff as natural and unspoilt as there are not many like that in this area. But with any coastal protection it is under constant review and scrutiny by both councilors and residents.
Reference Page
Policies of Coastal Defence from Lewes Council
- www.lewes.gov.uk/ coun/planning/lewes_ local_plan/contents_written.htm
Maps from www.Getamap.com
News Article on Cliff Collapse