Evaluation
If I was to do this investigation again there are ways in which I could improve it. I could have taken more results which would mean that the average would be more accurate. Also, as it was not possible to be in two places at once, the results were taken at different times in the day. This could have affected the results because the tide level would be different.
Longshore Drift
Longshore Drift is the process of sediment is moved along the shore. It happens when waves break at an angle to the beach and carry sediment across instead of straight back out. Investigating whether longshore drift occurs on both the North and South beach is another way of looking at the differences between either beach. We carried out both groyne measurements and marked pebbles or corks to study the whether longshore drift was present on either beach.
Groyne Measurements
Aim: To get a picture of longshore drift to see if there is a difference on either beach.
Equipment: ranging pole
Method: We took measurements for 10 groynes on the South beach.
We took the groyne measurements on the South beach only because there were no groynes on the North Beach. This shows immediately that there is no need for groynes because there is less longshore drift. We a measurement of the distance from the top of the groyne to the surface of the beach material at the high tide mark, mid tide mark and low tide mark of the groyne. We took the measurement on both the Left and right (north and south), side of the groyne.
Results – South beach:
Analysis:
The diagram shows that there isn’t a particular pattern to our findings so they are not entirely useful.
Marker Pebbles method:
Aim: To investigate longshore drift on both the North and south beach to see if there is a difference between the two coastlines. This will show us the direction of long shore drift at a certain time however as the direction can change.
Equipment: ranging pole, assortment of 12 painted pebbles.
Method: We first painted a variety of pebbles in a bright colour so that they could be easily seen. We stuck a ranging pole at a point where there was swash/backwash. Then we put the pebbles in at that point. After counting for 50 waves we located any pebbles and recorded the distance and direction the stones had travelled. I calculated the average distance travelled by adding up all the distances and then dividing that number by the number of pebbles. I used the direction that most of the pebbles travelled as the direction of longshore drift.
Results:
South Beach
Average Distance travelled – 13.7m
Modal Direction travelled – North
North Beach
Average Distance Travelled – 17.3m
Modal Direction travelled - North
Analysis:
The results show that the direction of longshore drift was generally to the North. This was the direction travelled by the majority of pebbles that we found. On the North beach, the distance travelled by the pebbles was generally higher.
Conclusion:
Although I cannot spot a particular pattern from the groyne measurements, the results from the marker pebbles method show that the direction of longshore drift is clearly northwards. It also shows that towards the North the longshore drift gets stronger. This could be however because of the groynes on the South beach.
Evaluation:
As we could not define a pattern from the groyne measurements this could be because of a number of factors. We could have made it a better experiment by doing it again.
To make the results more accurate for the pebble marker experiment we could have done the experiment over a longer period for days and even weeks as it could be affected by weather patterns or other factors. We also could have used a larger amount of pebbles to get a better average.
Coastal Management
Aim: To use observation to look at the obvious differences in the landscape of the coastline between the North and South beach.
Method: I drew two sketches, one facing the North beach and one facing the South and backed the sketches up with a photo.
North Beach
South Beach
Analysis:
When looking at the two pictures I can see that both beaches have some sort of coastal protection feature. By looking at my sketches I can see that the main difference between the two coastlines is that the North beach has much less coastal management structures than the South beach. On the South beach there are man made structures built to prevent erosion by man. An example is a footpath and steps built down the steps. There is also a sea wall and groynes built to stop the waves from eroding the coast. On the North beach however, there is much less vegetation but more rocks. There is rock put at the base of the cliff to protect it as well as sand put at the base to prevent a notch forming by erosion.
The most obvious difference between either beach is that the beach on the North beach does not have groynes or a sea wall. The cliff on the North beach is also steeper and there is more evidence of slumping. On the South beach, there is a gentler slope and the vegetation is denser.
Conclusion:
A beach has groynes to slow down the process of longshore drift which suggests that there is more longshore drift on the South beach than the North beach. The South beach has a sea wall, the most effective way of preventing erosion and the most expensive so it shows that the process of erosion on the South beach is happening very quickly, the sea wall is needed to protect the residential area on the cliff edge.
Human Activities along the coast
Aim: To use observation to look at obvious differences in the coastline North and South of the Tower Breakwater. I can now look at the differences in human activities on either side.
Equipment: Observation
Method: I made these observations throughout my time at Walton on the Naze, making notes on any signs of human activity I saw either side of the Tower Breakwater.
Results: When on the North side of the Tower breakwater I observed that there was a shop, car park, bins and toilets. However there was a lot of open space as well. When looking at the South side, there was much more signs of human activities, this also being shown in the map. The area is much more built up with residential areas and roads.
Analysis: The South side is much more built up than the North Side.
Conclusion: The differences in the amount of human activity either side of the tower breakwater can explain the differences in coastal management techniques. There have been more attempts to protect the coastline from erosion on the South side of the tower breakwater because the residential area is located there. For instance, groynes, sea wall and steps have been put there to try and reduce the effects of erosion both by man and the sea to try and protect the residential area.
Cliffs
Aim: In order to find out the differences between the North and South beach we investigated the differences in the cliffs.
Equipment: Clinometer, tape measure, sketch pad, pencil.
Method:
I started by drawing a sketch of the cliff and backed it up with a photograph to help me do a neat sketch when I returned.
I then stood approximately 40m away from the cliff base. I could not get to the base of the cliff because slumping had occurred and so this measurement was just an estimate. This distance was called D.
Then, using the Clinometer, I measured angle aº by standing 40m away and pointing the Clinometer up to the cliff edge.
To calculate the height of the cliff I used the formula: (D x tan aº) + height.
The Height is my height which is 1.68m
Results: North beach
(D x tan aº) + height
= (40 x tan 24º) + 1.68
=19.48914741
=19.5m (1 decimal place)
South Beach
We could not conduct a cliff profile fro the South Beach because we could not see the top of the cliff. This was because there were beach huts and coastal protection features all down the cliff and blocking the view.
Analysis:
As I could not conduct a cliff profile for the South beach I cannot compare the two beaches. However, I can conclude that the South beach has more coastal protection features, so much so that I was unable to conduct a cliff profile as they were in the way. I can also see that on the North beach, slumping has occurred.
Conclusion:
Although the two height profiles cannot be compared I can still use observation to see that the cliff on the North side of the beach is less disturbed by man made features and the South cliff also has a gentler slope. This could be because the South beach is used more on the South beach and so they put the beach huts there.
Evaluation:
I think that I could have gathered more sketches of the cliffs so that I could look at them in more detail.
Beaches
Beach Profile
We conducted a beach profile in order to find out several factors about the two beaches. By conducting two beach profiles, one on the South beach and one on the North beach, we are able to compare the different levels and shapes of each beach. We conducted the two beach profiles each at low tide to get the maximum area of the beach to measure. We worked from the sea up to the cliff in order to get positive values so it is easier to record. Also, by working in that direction, if the tide turned, we would not have had to stop the profile as we would be working away form the tide and not into it.
Aim: To record beach profiles on North and South beach
Equipment: Clinometer, recording sheet, tape measure, two rulers
Method:
- Starting at the coastline facing towards the cliff, stand up one of the rulers. Then, walking towards the cliff place the other where you can see a change in the level of ground.
- Holding up the two rulers, use the clinometer to work out the degree in the change of level by holding it from the point on one ruler and pointing it to the point on the other ruler.
- Then see what the degree in change is.
Results:
Analysis:
After looking at both the beach profiles for the North beach and South beach I can see that the North beach has a shorter length from the sea to the sea wall than the South beach. This may have been however, because we cannot be at two places at once when measuring the beach profile and so when we measured each beach they were at different tides. So when we did the beach profile for the North beach there was quite a high tide and when we did the South beach the tide had gone out slightly. The Beach profiles also show me that the North beach goes up more steeply towards the cliff base than the South beach does towards the sea Wall. This may be because the South beach has groynes which may stop the beach sediment from piling up steeply.
Evaluation
If I were to do the beach profile again I would probably take each beach profile at the same time, with one group of people recording North beach results and the other the South beach results.. This would avoid the problem of having a slight difference in tide when doing each beach profile as it isn’t possible to be in two places at once. Also if I had time I could do more than one beach profile on each beach in order to get a greater range of results and therefore make the results more accurate.
Sediment Analysis
In order to find if there is a difference in the beach material for both the North and South beach I did a sediment analysis. By doing this I could find out if the sediment varies between beaches. I would expect to find the size to decrease and the smoothness of the sediment to increase as you travel further towards the sea. This is because erosion takes place at the bottom of the cliff, causing the beach material at the top of the cliff to collapse. The fallen sediment is smaller and smoother towards the sea because attrition, when the waves cause rocks and boulders on the beach to bump into each other, causes the particles to break up into smaller ones.
We conducted the survey at both low water and high water at either beach, North and South.
Equipment: Concentric rings, pen, Visual chart for Powers’ scale of roundness, Table to record results
Method: For 50 pebbles at each of the four points, we recorded down the radius and length using the concentric ring, and Powers’ scale of roundness for each one.
- With the 50 pebble samples I used the calliuex roundness index as a measure of the pebbles roundness. This was calculated by using the formula:
((2xradius)/length) x1000
- I tallied up the amount of pebbles scored each scale of roundness each time I did the sediment analysis and put them into a bar graph for each point at the beach
- I used the long axis measurements to put in a dispersion diagram.
Analysis
Callieux Roundness Index Averages
South Beach High -797
South Beach Low - 805
North Beach Low - 817
North Beach High - 801
By looking at the averages I can see that the beach with the roundest pebbles on average is the North Beach. I think this is because there are groynes and other coastal protection features on the South beach, which prevent attrition from happening as much as on the North beach. As I had expected, the average roundness of pebbles on the lower part of the beach are rounder than high tide due to attrition.
Bar Graphs comparing roundness
From my graph I can see that in the north beach there was much less pebbles in the lower scales than the South beach which should mean that there was more rounded pebbles. This was true as there were higher scaled pebbles in the North beach than the South, particularly low water. This shows that, as in the callieux roundness index, that there are rounder pebbles in the north beach than the south. In the North beach the bar graphs also show that there was much rounder pebbles low tide than high tide. This was due to attrition again, where the sea reduces the size and rounds stones as the backwash carry the lighter material out to sea. In the South beach however, the amounts of stones in each scale are not significantly different at low and high tide.
Long axis measurements
I would expect the size of the pebbles to decrease and the smoothness of the sediment to increase as you travel further towards the sea on each beach. This is because erosion takes place at the bottom of the cliff, causing the beach material at the top of the cliff to collapse. The fallen sediment is smaller and smoother towards the sea because attrition, when the waves cause rocks and boulders on the beach to bump into each other, causes the particles to break up into smaller ones. However, on the North beach, the long axis measurements showed that the upper quartile and median for the low water was much higher than the high water measurements, indicating that the pebbles were generally larger than at high water. This was not the same on the South beach however. The long axis measurements show that at high water, the pebbles are generally larger in size which is as I would expect. The unexpected results of the North beach could be due to incorrect measuring or insufficient numbers of pebble data collected.
By looking at the dispersion diagrams I can see how spread out all the data values for each long axis measurement are. When looking at the low water measurements I can see that the south beach measurements are much closer together. The sample difference is significant in that the median for the North beach low water is much higher at 6cm than the south beach low water at 2.4cm. This would indicate that the pebbles on the South beach are smaller in size than on the North beach. When looking at the High water results I can see that there is not particularly a significant difference between samples and the medians are exactly the same, 4cm. However, the south beach does have a higher upper quartile of 4.9cm.
Evaluation
When working out the Calliuex roundness index, I found that I kept getting numbers over 1000 for the answer. This is not possible because 1000 is a perfectly round pebble. By getting an answer over 1000 it meant that the radius of the pebble we had measured was longer than the length. This is incorrect because the radius is always shorter than the length. It was because of this that I deleted all the incorrect samples from my list of pebbles and I had to replace them with another sample to make up 50 pebbles.
If I was to do another pebbles survey I would make sure my measurements were very accurate and that I didn’t record the length of the radius to be longer than the length. I could also take a larger sample so that if I did make an error I could replace it with the extra sample I has collected.
