The purpose of this study is to measure and explain the coastal processes occurring at Walton-on-the-Naze.
The purpose of this study is to measure and explain the coastal processes occurring at Walton-on-the-Naze.
We have chosen this particular area because it has a good rate of coastal retreat. The evidence for this is that there is plenty of bare soil which suggests that there has not been enough time for the vegetation to grow back. This means that the erosion must happen every few months.
I have included explanations of the ways that this has been combated:
. Vegetation
2. Rip Wrap
3. Drainage
4. Cliff Grading
5. Groynes
6. Sea Wall
7. Breakwaters
These are the technical terms used in the explanations of the sea defences:
Erosion: this is when rocks are worn away by the sea. Can end up forming new land structures.
Weathering: things can be weathered in three different ways, Physical Weathering, Biological Weathering and Chemical Weathering.
Mass Movement: when material moves down a slope affected by the pull of gravity.
Transportation: this is when material is transported by rivers or seas.
My aim in this investigation is to investigate the different factors affecting the rate of retreat of the Walton-on-the-Naze coastline. This will include clear diagrams and graphs of the information.
My aims are:
* To investigate and explain the rate of retreat;
* To investigate how the character of the waves and sea affects the rate of retreat;
* To investigate how transportation affects the rate of retreat;
* To investigate how the nature of the beach affects the rate of retreat;
* To investigate the nature and effectiveness of coastal defences.
The objectives are:
. To investigate how the nature of the cliffs affects the rate of retreat;
2. To investigate how the character of the waves/sea affects the rate of retreat;
3. To investigate how transportation affects the rate of retreat;
4. To investigate how the nature of the beach affects the rate of retreat;
5. To investigate the nature and effectiveness of coastal defences.
Objective One: To investigate how the nature of the cliffs affects the rate of retreat.
This will include a method about how I found out about the geology and the structure of the cliff, how I measured or estimated the height of the cliffs and how I calculated the volume of material removed from the beach.
I will draw an annotated section of the cliff, a table to explain the characteristics of the different rocks in the cliff, a series of cross sections to show the height of the cliff and the volume of material at different points on the beach.
I will tell you what each diagram and graph shows and how each aspect contributes to coastal retreat.
Objective Two: To investigate how the character of the waves/sea affects the rate of retreat.
This will include an explanation of how I measured wave crest and trough. For example how far out in the sea did I stand? What equipment did I use? How many readings did I take? And why?
Also an explanation of how I measured wave frequency. How long did I count for? Why?
I will also explain how I calculated other aspects such as water depth and wave energy. I will include the factors that could and did affect my results.
I will include a table to include the data collected and calculated.
Objective Three: To investigate how transportation affects the rate of retreat.
I will describe and explain the two methods I used and why. I will illustrate the cork method in a diagram. I will justify the methods used, outline the factors influencing your results, and outline the limitations of our methods and equipment. In these I will include reference to the tide, season of the year, weather conditions and fetch.
I will summarise and explain what each diagram and graph shows and how each aspect contributes to coastal retreat.
Objective Four: To investigate how the nature of the beach affects the rate of retreat.
I will describe and explain how I used the ranging poles, measuring tape, clinometer, spade and metre rule to complete the transect. I will include reference to the tide, season of the year and weather conditions.
I will draw a slope profile diagram to show the variations of the angles on the beach.
I will summarise and explain what the profile diagram shows, I will also explain how the beach angle and depth affect erosion and therefore the rate of coastal retreat.
Objective Five: To investigate the nature and effectiveness of coastal defences.
I will describe and explain how I collected the information used in this objective and drew diagrams. I will outline all the factors influencing my results and outline the limitations of my methods and equipment.
To investigate how the nature of the cliffs affects the rate retreat
Data Required
For this objective we needed to collect the following data:
* The geology of the cliffs was studied as an aspect of this objective,
* The height of the cliffs was ...
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Objective Five: To investigate the nature and effectiveness of coastal defences.
I will describe and explain how I collected the information used in this objective and drew diagrams. I will outline all the factors influencing my results and outline the limitations of my methods and equipment.
To investigate how the nature of the cliffs affects the rate retreat
Data Required
For this objective we needed to collect the following data:
* The geology of the cliffs was studied as an aspect of this objective,
* The height of the cliffs was studied as another aspect of this objective,
* The last aspect studied of this objective was the volume of material removed.
Method
The geology of the cliffs:
The method we used to make the measurement of the geology of the cliffs (Fig. 1.1.) was to take a sample of the cliff and to record the data we found in a table (Fig. 1.2). We found out from our observations that there were three different types of rock in the cliff. We came to this conclusion after we had looked at, felt, pushed and squeezed each of the different types of rock. We found out from our teacher that the names of these three rocks were called London Clay, Red Crag (consisting of different types of sands and silts) and Boulder Clay and Gravel. London Clay was found at the bottom of the cliff, the middle of the cliff was made up of Red Crag and the top was made up of Boulder Clay and Gravel. I have shown the positions of the rocks in the cliff in a diagram below.
(Fig. 1.1)
Fig. 1.3.
A section of the cliff below the Naze Tower. It is labelled to show you at what positions the different rock types occur.
Data Presentation
Below I have drawn up a table to show the appearance, colour, texture, hardness and permeability of the rocks in the cliff.
Boulder Clay and Gravel
Red Crag (sands and silts)
London Clay
Appearance
A thin layer on top of cliff. Loose sands and gravel.
Very worn material in middle of cliff.
Very thick layer at bottom of cliff.
Colour
Mixed colours, mainly greys and oranges.
Orange and red.
Mainly grey/black.
Texture
Ruff and crumbly.
Ruff and sandy.
Slimy and smooth.
Hardness
Offers little protection to cliff below. Can be weathered by rain and wind easily.
Very easily broken down and destroyed.
Clay is very soft and flexible.
Permeability
None.
Very easily.
Not easily.
Fig. 1.2.
There were a couple of problems encountered whilst collecting this data. The first problem was that we could not reach the section of Red Crag in the middle of the cliff. To solve this problem we had to search around on the beach for this material. The same problem aroused when we needed to record data and observations on the Boulder Clay as it was at the top of the cliff, so we solved this by using the solution used in the first problem.
How we measured/estimated the height of the cliffs:
We measured the height of the cliffs using a clinometer. We stood at the end of the wave cut platform and the edge of the water and measured the angle of this elevation. We then measured the width of the beach from the foot of the cliff to the end of the wave cut platform. This measurement turned out to be 57 metres. We then found the height of the cliffs using trigonometry. (Fig. 1.4.)
Height of cliff =
Fig, 1.4.
We encountered a problem when it came to measuring the angle of elevation of the cliff. Where we measured the angle from we were standing on quite uneven ground therefore the measurement could have been different from another point further along the beach. This means the calculation to find the height of the cliff is an estimate rather than definitive.
How we calculated the volume of material removed:
We calculated the volume of material removed from the beach in one simple calculation.
The calculation was:
Volume of material = retreat x height
The answers to the calculation were:
At the southern end of the beach (tower breakwater) = 340metres cubed
At the centre of the beach (near the pill box) = 340metres cubed
At the northern end of the beach (near the sea wall) = 85metres cubed
Analysis
Fig. 1.1 shows the different types of rocks in the cliff and where they are situated in the cliff. This shows at which areas of the cliff it is more likely to retreat because of different types of rocks.
Fig. 1.2 shows the appearance, colour, texture, hardness and permeability of the different rocks in the cliff.
Fig. 1.3 shows the equation used to find the height of the cliff. Therefore giving me the result of the height of the cliff.
To investigate how the character of the waves/sea affects the rate of retreat
Data Required
For this objective we needed to collect the following data:
* Wave frequency
* Wave type
* Wave crest
* Wave trough
* Wave height
* Water depth
* Wave length
* Wave frequency
* Fetch
Method
To measure the wave crest and wave trough we stood about 2 to 3 metres out into the sea so that we could reach to measure the main body of the wave. We used a metre rule to measure the height of the crest and trough. We took 10 readings so that we would have plenty of data as to work from later in the investigation.
Diagram
We measured the wave frequency by counting how many waves broke in a given amount of time. This given amount of time was 1 minute as 1 minute is the smallest whole number.
I calculated the water depth by using the equation like this:
Water depth = trough + 0.5 wave height
I calculated the wave length using the equation like this:
Wave length = 3.1 x 60 x v water depth ÷ wave frequency
I calculated the wave energy using the equation like this:
Wave energy = 740 x H² x wave length
Wave type was decided with the following information:
Generally, Constructive wave frequency is less than 10 per minute, Destructive wave frequency is greater than 13 per minute. But on the day we made the observations the waves were of low energy and therefore were deemed to not be destructive but constructive in nature.
Data Presentation
The data and working for objective one made on our trip is shown in a table below.
2
3
4
5
6
7
8
9
0
Wave Frequency
4
5
6
6
5
6
2
2
4
9
Wave Crest
0.45
0.40
0.40
0.43
0.44
0.45
0.40
0.47
0.38
0.37
Wave Trough
0.25
0.23
0.21
0.21
0.21
0.22
0.23
0.22
0.26
0.25
Wave Height
0.20
0.17
0.21
0.22
0.23
0.23
0.17
0.25
0.12
0.12
Water Depth
0.35
0.32
0.32
0.32
0.33
0.33
0.32
0.35
0.32
0.31
Wave Length
7.85
7.01
6.57
6.57
7.12
6.67
8.76
9.16
7.57
7.39
Wave Energy
232.36
49.91
214.4
235.01
278.71
261.10
87.34
423.65
375.68
341.78
Wave Type
CON
CON
CON
CON
CON
CON
CON
CON
CON
CON
Fig. 2.1
On the next pages I have constructed graphs to show the data collected in the table above (Fig.2.1.)
Fig 2.2.
Fig 2.3.
Fig.2.4.
Fig2.5.
Fig 2.6.
Fig 2.7.
Analysis
Fig. 2.1 shows the data collected on our trip to Walton On The Naze. It includes height measurements for Wave Crest, Wave Trough, Wave Height, Water Depth and Wave Length, Kilo-joule measurements for Wave Energy. Also frequency measurements for Wave Frequency in a one-minute time period.
Fig. 2.2 is a graph showing the data in the table for Wave Frequency.
Fig. 2.3 is a graph showing the data in the table for Wave Crest.
Fig. 2.4 is a graph showing the data in the table for Wave Trough.
Fig. 2.5 is a graph showing the data in the table for Wave Height.
Fig. 2.6 is a graph showing the data in the table for Water Depth.
Fig. 2.7. is a graph showing the data in the table for Wave Length.
Fig. 2.8. is a graph showing the data in the table for Wave Energy.
To investigate how transportation affects the rate of retreat.
Data Required
For this objective we needed to collect the following data:
* The direction of longshore drift
* The amount of longshore drift
* The height of the beach either side of a groyne
* Evidence of suspension
Method for measuring longshore drift
For this objective we had to stand out in the sea about two to three metres to get an accurate reading. One person from our group stood in the water with a ranging pole this was the start point. A cork was dropped and then another person followed the cork timing two minutes, when two minutes was up they put the ranging pole in the seabed, at the point the cork had reached. Then a third person measured with a tape measure how far the cork had travelled from the start pole and the direction in which it had travelled. This is demonstrated in Fig.3.1. the results were recorded in a table. (Fig.3.2.)
Diagram
Fig. 3.1.
Data Presentation
The data we collected for this objective on our trip is shown in the following table.
Distance travelled in 2 minutes
Distance travelled in 1 hour
Direction of travel
6.20 metres
86 metres
S/W
2
1.1 metres
333 metres
S/W
3
2.7 metres
81 metres
S/W
4
2.7 metres
81 metres
S/W
5
6.4 metres
92 metres
S/W
Fig. 3.2.
Influencing factors, limitations, problems encountered and how they were overcome
There were quite a few problems encountered whilst we were conducting this part of the objective. One major factor was the wind. It was at different strengths all the way along the shoreline. Another factor was when the tide was going out it was calm and this mucked up the first couple of readings. Also the results were not realistic for the whole year as the same weather conditions do not apply for every minute of every day of every year.
Method for measuring groyne height
To measure the height of the material either side of the groyne 2 people from the group stood one side and the other two stood the other side. Then the tape measure was passed over to measure the difference in sand height on each side of the groyne as shown in Fig. 3.3.
Fig. 3.3.
Influencing factors, limitations, problems encountered and how they were overcome.
Whilst we were measuring the difference in height of the sand either side of the groyne the tape measure started to get twisted so all we had to do was untangle the tape measure.
If we hadn't untangled the tape measure it might have made the height greater as there was more tape being used.
Data Presentation
On the next page there is a page diagram (Fig. 3.4.) showing the heights of the sand on each side of the groyne.
Fig. 3.4.
Analysis
Fig. 3.1. is a diagram showing the method in which we measured the longshore drift. This however is not accurate for the whole year but only accurate for the day that we were doing the investigations.
Fig. 3.2. is a table containing the data taken from the longshore drift experiment and direction of longshore drift travel.
Fig. 3.3. is a diagram showing the method of the experiment to find the difference in height of the sand either side of the groynes.
Fig. 3.4. is a diagram showing the height of the beach either side of the groyne and the difference between the height on either side.
To investigate how the nature of the beach affects the rate of retreat.
Data Required
* The gradient of the beach
* The width of the beach
* The depth of the sand on the beach
Method
To complete the transect of the beach we used two ranging poles, a measuring tape, a clinometer, spade, and metre rule. Firstly we used the ranging pole balanced on the wave cut platform. This would be the point from which we used the clinometer to find the angle of the beach. We used the measuring tape to measure every three metres where we would dig through the sand with the spade to find the clay wave cut platform. We used the metre rule to measure the depth of the sand on the beach until the wave cut platform below.
Diagram
Fig. 4.1.
Influencing factors, limitations, problems encountered and how they were overcome
The problems we had with this objective was that as we got higher up the beach the sides of the sand started to cave in and the holes were filing up with water from the sand. It was very hard to try and solve this and we did not succeed.
Data Presentation
On the next page I have drawn a table with the observations and measurements made on the day.
Section of transect
(started at water's edge)
Beach angle
(degrees)
Beach depth
(metres)
0 metres
0°
0
0-3 metres
-7°
0
3-6 metres
+4°
0
6-9 metres
+12°
0
9-12 metres
+5°
0
2-15 metres
+4°
0
5-18 metres
+5°
0
8-21 metres
+5°
0.02
21-24 metres
+8°
0.02
24-27 metres
+7°
0.11
27-30 metres
+14°
0.27
30-33 metres
+10°
0.31
33-36 metres
+4°
0.37
Fig. 4.2.
Total width of beach = 36 metres
Below I have drawn a slope diagram to show the variation in degrees of the wave cut platform.
Fig. 4.3.
Analysis
Fig. 4.1. is the diagram that shows what we did and the process of this objective and how we collected the data.
Fig. 4.2. shows the data we collected whilst doing the objective. It contains the beach depth and the angle of the beach at each point at every three metres. This tells us how the beach may erode.
Fig. 4.3. is a profile diagram of the beach showing the beach depth and the angle of the beach. This shows us how the beach erodes and by what extent the damage is caused.
The angle of the beach affects the rate of coastal retreat as it is a steady angle that the water has to climb to reach the cliff therefore the water would lose all its energy before reaching the foot of the cliff.
The width of the beach would affect the rate of coastal retreat as the bigger the width the further the water has to go to come into contact with the foot of the cliff.
The depth of the beach also affects the rate of retreat as the deeper the sand the more room water has to soak in therefore there is less water reaching the foot of the cliff therefore causing a low rate of coastal retreat.
To investigate the nature and effectiveness of coastal defences.
Data Required
* The location of the various types of coastal defences
* A description of the various types of costal defences
* An evaluation of the condition of the various types of coastal defences
* An evaluation of the effectiveness of the various types of coastal defences
Location of all the costal defences:
Fig.5.1.
Pictures of all the coastal defences:
Description and evaluation of the coastal defences:
Vegetation
Vegetation has been planted on the cliff slope to soak up water within the cliff also while it is searching for the water it binds the soil closer together and makes it harder to take apart. Looking at the cliff and the vegetation planted it looks like it was a pretty successful idea. The condition of this cliff defence is pretty poor as many plants and shrubs are dying and are in need of replacement.
Rip Rap
Rip Rap, which is the name for lots of large rocks, is placed along the shoreline to absorb the energy of many large waves to make them less powerful. This helps stop erosion happening faster than it needs to. If this were not here then the powerful waves would tear into the cliff slope. The rocks are in pretty good condition, which would explain that it is quite new.
Drainage
Drainage has been installed within the cliff slope to absorb any loose water in the cliff. These are made out of terracotta because this lets water through the sides of the pipe unless it is waterproofed at the bottom. This is quite successful as the area of which this has been installed the erosion has been reduced by quite a considerable margin. The pipes are old and beginning to wear with age.
Cliff Grading
Tendring District Council has introduced Cliff Grading. This is a process which makes the cliff gradient lesser therefore landslides are less likely to occur. This is quite successful as there is no recent evidence of landslides occurring.
Groynes
Groynes have been put in place to stop the occurrence of longshore drift. These are planks of wood joined together to make a barrier, which stops sand from piling up at one end of the beach. We can tell that this is successful by measuring the difference in height of the sand either side of the groyne. The condition of these groynes are poor they need replacing as planks of wood have fallen down.
Sea Wall
A Sea Wall has been built all the way along this stretch of the coastline. This stops the waves from getting at the cliff and stops erosion. It makes this possible by having different parts at different heights. This is successful as there is no erosion to the cliff at this point. The condition of this is good, but has cracks, which could lead to water freezing within the cracks and causing the cracks to expand. But this is a very expensive sea defence and would be difficult to replace.
Breakwater
One Breakwater has been assembled at the far north of all these sea defences. This is what absorbs the most energy out of the waves and is the biggest obstacle. It consists of a sturdy wooden triangle with rocks in the middle to absorb the energy. It is very successful but some of the rocks within the breakwater are eroding this would suggest that these have been here quite along time.