To overcome these issues above, I took another set of readings measuring the angle to the top of the beach using ranging poles and clinometers. Putting these two results together. I can work out how far the cliffs have retreated since 1945,and then how much it is retreating on average each year. The ranging poles were set at 20m intervals. The height we measured this was at 1.5m.This is shown clearly in the diagram below.
These angles would benefit me in working out the measurement of the cliff height (helps me to know how high above sea level the cliff is)
Analysis and conclusion
From the results, I can deduce that the north beach is eroding and we can address the measurement as 38.5 metres in 63 years. However this is not fully accurate because we only measured the slump and not the cliff face itself. (due to it being dangerous). This information has helped me to understand that the North beach is eroding at a rate of 1.23 metres per year. This is a very quick rate and there are numerous reasons to help explore and analyse this. I have showed in early paragraphs the evidence of erosion at the Naze. However this alarming rate of erosion leads me to my sub-question: Why is the North beach eroding so quickly?
To help me answer this I will be using a range of secondary data and observations made on the North and South beach in terms of protection.
The Geology
There are two main types of rock at Walton; London clay and Red Crag. The cliffs are made up of sand and gravel deposits laid on top of London clay and it is because of this geological arrangement that the cliffs are so unstable. Water percolates through the permeable sand until it reaches the impermeable London clay. The water acts as a lubricant, causing the upper sections of the cliff to slip seawards. The sea is also eroding the lower sections of the cliff, leading to greater insecurity.From the Tables below I can deduce that Red crag has been present as part of the Piacenzian layer for 1.8 - 3million years old. At the base of the cliff forms the London Clay, this is from the Lower Eocene period, mostly of the Blackheath beds around 45 million years.
Slumping
(Foot of slumping)
Red Crag on top of cliff
London Clay rock.
Beach is a wave cut platform and is
predominantly made up of clay.
Diagram showing slumping cliff on North Beach
Protection comparison: North and South beach
North
Armour blocks are indeed one type of protection on the North side.They are relatively cheap but are environmentally unattractive. If they are resting on sand and shingle they can also be undermined by waves. There are no sea walls or groynes built on the north side. Minor plantation is seen on the cliff face. There are also apparent cracks in the wall. The cliff faces were indeed battered and bruised and there were signs of slumping. This apparent lack of protection, is a fundamental factor for the cause of the rate of which the North beach is eroding.
Rip Rap
South
Recurved Sea Walls are expensive to build and may cost up to £1million per km. They are designed to stop erosion but his also means that there is less sediment to protect other stretches of coast. They reflect wave energy, and as a result of this, the waves scour base of sea walls undermining them so that they eventually collapse.
Groynes stop longshore drift and keeps the beach in place. Basically the idea of a groyne is to prevent longshore drift. Groynes are very useful and are the cheapest and most effective way of protecting a cliff and the beach behind it.
There are also revetments present on the south beach. Revetments are the structures placed on banks in such a way as to absorb the energy of incoming waves. They’re built to preserve the existing uses of the shoreline. The revetments protect the land behind them
The Rip Rap
is contained by
a mesh. Gabion
like structure
under the
wooden frame.
Built
Conclusion
The two rocks that I have mentioned and explained above are two pivotal factors in terms of geology, for the cause of such an alarming rate of erosion on the North beach. However the north beach lacks vital protection to keep its erosion under control,and the evidence of this is exploited through its fast rate of erosion and evident slumping.Now that I have shown how and why the North beach is eroding at such a rate, it is important for me to explore the processes that are occurring on the South Beach,i.e longshore drift. This leads me to my next question,What evidence is there that long shore drift is taking place?
What evidence is there that long shore drift is taking place?
1st objective:Explore the direction and speed at which longshore drift was occuring
Method
We threw an orange into the sea and marked the position on beach with a ranging pole.We timed the orange floating in sea for a total of 5 minutes. After 5 minutes we marked the position of orange. We then measured distance and direction that the orange moved.
Problems and limitations
The oranges did not always move freely and at times were trapped on the rocks and beach.The tests were also only taken in a low number of days limitation in the sense that the wind may have changed direction on other days.
Solutions
We undertook the test several times at each location. We looked for other evidence of longshore drift to support our observations.
Results
(below)
Bar Graph from tabled results
2nd Objective: Establish whether the deposition of beach material along the groynes supported evidence of longshore drift.
Method
We looked at the depth of deposit of sand on either side of the groynes. The side of groyne with greater depth to beach would indicate direction of longshore drift. We measured the depth to the beach from fixed point on groyne. Our next measurements were the differences in height of beach on either side of the groyne. We took the readings for each groyne at lower, middle and upper parts of the groyne.
Limitations
The groynes sloped towards the sea and we could not measure from a fixed height on groyne.
Solution
To use difference in height to establish likely direction of longshore drift.
Results
Graphs
Analysis and Conclusion
The first table indicates that longshore drift is operating in a northerly direction. The chart also clearly shows us that the distance travelled by the orange is far greater at the pillboxes than on the south beach. this gives an indication that longshore drift operates more, and has a greater impact on the North side rather than the South.
As the results for the second experiment show, the upper part of the groyne has the greatest difference. This is because this area of the beach collects the most amount of material. The beach material piles up because there is no other route for the beach material to escape to. We can also see that the further we go north,the greater the difference becomes.Thus we can assume that longshore drift is getting stronger as we go north. The North side also had a greater deposit and therefore proves again that the direction of longshore drift is northerly.
What effect have the methods of coastal protection had on the scenery of the area?
What are the impacts of coastal defences on the coastal processes?
We compared beach profile. We marked out distances of 5 metres from the shore to cliff line. At each interval place ranging pole.Use a ranging pole and clinometer to measure the angle of beach over a 5 metre interval. Record profile angles on record sheet.
Analysis
From my experiments, data and
Conclusion
The north beach is eroding at a tremendous rate.The excessive protection on the south beahc