Two people then stood on, for example, point 2 and 3 and each used a clinometer to measure the angle between the points to get an average measurement, and to make the measuring of the angles as accurate as possible.
The two people had to be roughly the same height to make it a fair test and we made a note of whether the slope was rising or falling. These measurements were not so much to prove or disprove our hypotheses but so that we could draw beach profiles of each of the groyne sites.
To investigate into the second hypothesis about pebble size we lay a metre ruler down on the ground at a right angle to the groyne at each measuring point. At each 25cm mark we picked up the pebble that was lying there and measured its long axis length using a set of callipers. This meant that for each measuring point we had five pebbles’ lengths to work out an average length for each point, and so could compare average pebble size near the shore the shoreline to pebble size further away.
We collected the data in the afternoon, from about 2:30pm until 3:15pm. We knew that this was when the tide was quite low so that we would have the maximum amount of beach to measure. We tried to collect it quite quickly so that the tide didn’t start to come back in.
When analysing the data there are some factors that must be taken into account. One of the main factors is that on the day which we collected the data, the wind affecting the wave direction was actually blowing from the Southeast, which may affect the accuracy of the results compared to other times of year when the wind blows mainly from the Southwest.
The data was taken from three different groynes all along the beach, so the results may differ from each other. The time of day could also affect the results, as the tide at different times may alter the reliability of the data we collected.
- Data Interpretation
To help me to analyse the data we collected, I presented all of the data in a variety of different ways, including beach profiles, a scatter graph and divided bar charts.
Graphs 1a and 1b are beach profiles of the two sides of Groyne 1-the updrift and the downdrift. We measured the vertical height from the beach to the top of the groyne for both the updrift side and the downdrift side. This told us that the updrift was 182cm and the downdrift was 69cm, giving a difference of 113cm. The updrift also finished higher that the downdrift, showing that there was more shingle piled up on the updrift. This supports our hypothesis, as the waves which usually comes from the Southwest move the shingle up the beach in an easterly direction and more shingle stays on the left side of the groynes (if you are looking at the groyne from the sea.)
Graphs 2a and 2b are also beach profiles, but they are profiles of the updrift and downdrift side of Groyne 2. On this groyne, the vertical height from the top of the groyne and the beach was 220 cm for the updrift, and 94cm for the downdrift, giving a difference of 126cm, which was even bigger than Groyne 1. The updrift side also finished higher than the downdrift, which shows that the shingle is being moved by the waves along the beach in an easterly direction.
Graphs 3a and 3b are the 2 beach profiles for Groyne 3 (updrift and downdrift). The difference between this groyne and the other 2 groynes is that the updrift and the downdrift are the same distance from the top of the groyne to the beach as each other (220cm). But as we took measurements further up the beach we found that the updrift side was higher after the beginning, and ended up a lot higher than the downdrift side, showing also that there was more shingle deposited on the updrift side, again supporting our hypothesis.
Before drawing the beach profiles I had thought that they may not support the hypothesis by the updrift side having more shingle deposited on it, because of the wind blowing form the Southeast at the time we were collecting the data. It did not affect the results or these graphs, and I think this may be because it takes time to change the overall deposition of shingle on the beach from one side to another.
Graphs 4a and 4b are both scatter graphs and they show the relationship between average pebble size and distance from the shoreline.
On the graph for the updrift (4a) I have plotted the data for all three groynes’ updrift sides on the same axis, but I have done the three in different colours with a key so it is easy to look at the data for each groyne. Groyne 1 fitted in very well with the pattern that I expected to emerge, as all but one of the average pebble lengths was higher than the previous, therefore supporting my prediction that pebble size increases with distance from the shoreline. However, groyne 2 did not really fit with my prediction, as the results did not seem to have a positive correlation. For example, the second result was lower than the first, and the next was higher, then lower, then lower, and then higher. Groyne 3 fitted in with my prediction, as every single one of the results was higher than the previous one. Therefore, overall graph 4a supported my prediction that pebble size increases with distance from the shoreline.
On the graph for the downdrift (4b, on tracing paper) the results were, overall, much less like I had predicted. Although Groyne 1’s downdrift pebble sizes did not follow the exact pattern of each average pebble size getting greater with distance from the shoreline, there was an overall positive correlation. But for Groyne 2, that is not the case, and the results have no real correlation, as the average pebble sizes go up and down, rather than increasing with distance from the shoreline. The pebble sizes for Groyne 3 also have no correlation, meaning that overall, graph 4b doesn’t support the hypothesis.
I also plotted the same data in a different way, by using 3 divided bar charts for each of the groynes, with tracing paper over the top so that there were 6 bar charts in total. Like the scatter graph, the divided bar charts showed clearly that Groyne 1 had the ‘best’ results in that they supported my prediction. I did a key to show which lengths of pebbles were represented by each colour. The smallest pebbles were represented by pink, the next biggest by red, then yellow, then green, then blue and finally, the largest was represented by purple. In Graph 5a, which was for the updrift side of Groyne 1, the bars started off being just pink and red, then more yellow and green was introduced gradually and the last bar was made up of just green, blue and purple blocks, showing that overall the pebble size did increase with distance from the shoreline. Graph 6a, for Groyne 2, did not show the same pattern, as the pebble size seemed to reach a climax at about 23 metres, when the pebbles were all 6cm-8.9cm, and then the size seemed to fall again, as one of the bars had 5 blocks in a bar that were 3cm-5.9cm. The last bar, at about 41 metres contained five red blocks, and one yellow, so had decreased overall since the bar at 23 metres. Graph 7a, like Graph 5a, also supported my prediction, as the first bar was made up totally of pink blocks (0cm-2.9cm), and with distance from the shoreline, more red and yellow blocks were introduced. The last bar contained 2 red blocks, 1 yellow, 1 green and 1 purple, which showed an overall increase in pebble size.
The graphs for the downdrift, like the scatter graph, show that the overall pattern for pebble size with distance from the shoreline is not as clear as the updrift. The divided bar charts are not as accurate as the scatter graphs, and do not show exact measurements, because the data is grouped into six different categories. Groyne 1’s downdrift side (Graph 5b) seems to show an increase in pebble size, but then it peaks at about 23m, with all of the blocks being green (9cm-11.9cm), and then seems to drop slightly towards the end. Graph 6b doesn’t show a pattern of increasing or decreasing pebble size and nor does Graph 7b.
From analysing the scatter graphs and the divided bar charts, it has come to my attention that the results taken from the updrift sides of the three groynes support my prediction much better than the downdrift. I think this could be because if the prevailing wind is from the Southwest then the constructive waves will transport shingle up the beach and deposit it on the updrift side of the groyne.
Waves from Southeast transport and deposit shingle on the left (updrift) side of the Groyne. The larger waves deposit large shingle at the back, and the less powerful waves deposit smaller shingle nearer to the shoreline. This could be why the updrift readings mostly fit in with the theory of shingle deposition, but because the downdrift side doesn’t have the waves hitting it directly, it doesn’t get the same patterns of pebble size.
Something else I noticed was that the results for groyne 1 were a lot more conclusive and supportive of my prediction than Groyne 2 and Groyne 3. This could be because the beach is replenished every so often to stop coastal erosion in the area. Groynes 2 and 3 may have been recently replenished with new shingle, so small pebbles may have been piled onto the beach at the back, which is why the data didn’t fit very well with my prediction. I think it depends where the data is collected from as to how representative it is of the beach depostition processes in the area.
From the graphs that I have drawn to represent the data we colected I have concluded that on the beach in Eastbourne, longshore drift is from the Southwest.
I have also concluded that shingle size usually increases with
distance from the shoreline, but that it is more true for shingle on the updrift side of the groyne.
- Evaluation
I think that our choice of hypothesis was good because it was quite easy to collect the data. Because we chose to study physical geography rather than human, it meant we could just go to the beach and record our data rather than have to find people to interview.
The beach in Eastbourne was a good location to do our investigation, as the beach has groynes so we were able to draw beach profiles of each side of each groyne from the measurements that we took. The beach is made up of shingle, so we could use the callipers to measure pebble size. If it had been a sand beach then we wouldn’t have been able to measure the sediment, so wouldn’t have known whether the pebble size increases with distance from the shoreline. The only disadvantage of using the beach in Eastbourne is that it is replenished with new shingle, so the data we collected may not have been totally representative of what actually happens naturally.
We were organised in our approach, and in our group we all had designated jobs, for example one person measured the pebbles, and another recorded the data. We had all of the equipment that we needed with us to gather the relevant information and as a result of this, we were quite quick to finish, but we were also thorough.
I feel that the methods we chose to carry out were appropriate for the data collection. The measurement of lengths and angles we took from each break of slope helped me to draw the beach profiles and therefore work out from which direction longshore drift is. The pebble measurements we took from each point enabled us to work out averages, and plot the data on graphs.
If I were to do the project again, I would improve the method by taking more readings of pebble sizes, because for groynes when there were only 6 breaks of slope (e.g. groyne 3), this meant that there weren’t many readings to draw conclusions for.
I would also take measurements from a variety of groynes along the beach, and would use more groynes, probably about 5, so that I had more data to analyse and get more specific and accurate conclusions from.
I would try to make sure that at the time I was collecting the data, the prevailing wind was from the Southwest, as the change in wind direction that had happened before we went to Eastbourne could have had an effect on the reliability of our data by altering the direction of longshore drift.
The beach profiles that I drew of both the updrift and downdrift sides of the three groynes were relevant to the hypothesis as they enabled me to draw beach profiles and thus work out the direction of longshore drift by comparing the updrift with the downdrift.
The scatter graphs that I constructed allowed me to look at the data for pebble sizes and see if there was positive, negative or no correlation and I could read off exact measurements of average pebble sizes.
The divided bar charts are more general, as the data is grouped so it is impossible to know the exact lengths of each pebble, but know that it is between two lengths. By just looking at the colours of the blocks you can see the sort of size that each pebble is, and can easily see any patterns emerging.
The analysis about longshore drift is conclusive and it supports my prediction and the geographical theory behind it. The analysis about pebble size is conclusive for the updrift, as it supports my theory and prediction, but the downdrift is not really conclusive, as the results showed only a slight pattern that supported my prediction. The results are valid as we took lots of measures to make sure that it was fairly done, for example we took five pebble sizes at each point to get an average. Overall though, I think that the hypothesis has been proved, but if I did the project again, changing what I mentioned before, the data would be more conclusive.
The main limitation of the project was that we did not have much time to collect the data, and if we had been in Eastbourne for a longer period of time, this may have allowed us to collect even more data and get more conclusive results, or extend the project.
To extend the hypothesis we could go to one pebble beach with groynes and one without to see if pebbles size increases with distance from the shore in the same way on beaches without groynes. We could also study a beach that isn’t on the south coast and see where, if anywhere, longshore drift is coming from.
Eastbourne Project
by
Jennie Lace
10c
Contents
Introduction Page 1
Method Page 4
Data presentation Page 6-12
Data Interpretation Page 13
Evaluation Page 16
Additional work Page 18
Field Sketch (High and Over) Page 19
Field Sketch (River Cuckmere) Page 20
Field Sketch (River Meander) Page 21
Field Sketch (Holywell Retreat) Page 22
Bibliography Page 23
Additional Work
As well as studying the beach in Eastbourne, we also studied some aspects of human geography in Eastbourne and the surrounding area.
To look at and compare land use in Eastbourne, we conducted a land use transect. Each group was given a group of buildings and we had to note down what the building was used for and how many stories it had. This was to see if land use in Eastbourne is affected by distance from the coast.
On the journey back from Eastbourne, we stopped at two places. Broadfield is a small group of shops, and Crawley is a town with a large shopping area with many shops. We wanted to investigate if there was a higher proportion of shops selling comparison goods (inexpensive, not bought very frequently, e.g. furniture, electrical appliances) in Crawley than at Broadfield. To find this out we carried out land use transects at each site and compared them.
We also wanted to see if people travel further to shop in Crawley town centre than Broadfield. We interviewed as many people as possible at both of the locations, asking them questions such as where they live, how often they shop there, and what they had come to buy. We then recorded their answers in a table.
Bibliography
- ‘Understanding GCSE Geography’ by Ann Bowen and John Pallister
- ‘Mapwork Skills and local issues’ by Jack Gillet