I needed to investigate the evidence that erosion was still taking place on the north beach . In order to perform this, I measured the width from the old pillbox to the bottom of the cliff. I used a measuring tape. The measurement was very relevant because knowing this would help validate how far the cliffs were retreating over a span of years. An issue in collecting this data was that we could not walk directly onto the slump, for safety reasons. I also did not have the exact placement of the pillbox.
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