IB Geography SL Fieldwork - An investigation of the effects of longshore drift at two different...

Geography Standard Level Fieldwork An investigation of the effects of longshore drift at two different beaches in Aldeburgh and Thorpeness

Marc Wierzbitzki

00-0815-083 Hockerill Anglo-European College IB Session May 2012 Word Count: 2498

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Table Of Content Aim ............................................................................................................................................. 2

Location ..................................................................................................................................... 2 Connection To The IB Geography Standard Level Syllabus ............................................... 3

Theoretical Background ........................................................................................................... 3 Hypothesis ................................................................................................................................. 4

Method Of Investigation .......................................................................................................... 6 Results And Analysis ................................................................................................................ 8

Raw Data ............................................................................................................................................ 8 Aldeburgh ........................................................................................................................................ 8 Thorpeness .................................................................................................................................... 14

Beach Profiles ................................................................................................................................... 20 Aldeburgh ...................................................................................................................................... 20 Thorpeness .................................................................................................................................... 23

Examining The Results Using Spearman’s Rank Correlation Coefficient Diagram ................ 26 Examining The Results Using “R squared” .................................................................................. 29 Mean Pebble Size Compared To Distance From Sea ................................................................... 31

Aldeburgh ...................................................................................................................................... 31 Thorpeness .................................................................................................................................... 33 Both Locations .............................................................................................................................. 35 Standard Deviation For Pebble Sizes ............................................................................................ 36 Analysis ......................................................................................................................................... 37

Mean Pebble Size Compared To Beach Gradient ........................................................................ 38 Aldeburgh ...................................................................................................................................... 38 Thorpeness .................................................................................................................................... 40 Both Locations .............................................................................................................................. 42 Analysis ......................................................................................................................................... 43

Shape Compared To Distance From Sea ....................................................................................... 49 Aldeburgh ...................................................................................................................................... 49 Thorpeness .................................................................................................................................... 51 Both Locations .............................................................................................................................. 53 Standard Deviation For Pebble Shape ........................................................................................... 54 Analysis ......................................................................................................................................... 54

Conclusion ............................................................................................................................... 55

Evaluation ................................................................................................................................ 56 Bibliography ............................................................................................................................ 57


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Aim The aim of this Geography Fieldwork is to answer the question: “Is there a correlation between the size of pebbles and their location (which is affected by littoral drift) in terms of distance from the sea and the gradient of the beach?” It will also be examined whether there is a relationship between the beach gradient and the pebble size.

Location The survey was carried out at two different beaches in East England that were about 4.7km apart. The first location where measurements were taken was a beach near Aldeburgh, the second near Thorpeness. In this region, there is littoral (longshore) drift from north to south (see map). Figure 1: Maps showing Aldeburgh and Thorpeness, the two areas, where the survey was carried out.1 2

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Area%of%survey%

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Connection To The IB Geography Standard Level Syllabus This fieldwork is closely linked to “Option B: Oceans and their coastal margins”, as defined in the Geography guide for first examinations in 20113. It especially focuses on subtopic number five (“Coastal margins”), since it will “examine the relationship between coastal processes […] [littoral drift] […] and different coastal landforms”.4

Theoretical Background Due to the fact that waves have a certain amount of energy, they can transport sediment when they hit the coast. Also, they often reach it at an angle. This is called longshore drift: Figure 2: An illustration explaining the concept of long shore drift5. This means that when they break their swash transports the sediment up the beach at a certain angle. At the maximum height, the backwash then pulls down the lighter sediment perpendicular to the shore. Water infiltrates the beach material so that there is less energy in the backwash. Therefore, the heavier and bigger pebbles should be found at a greater distance from the sea, whereas the lighter and smaller pebbles should be closer to the sea. Furthermore, as we did our research at two different pebble beaches, the pebbles are constantly subject to attrition. This means that theoretically, their size should continually decrease and they would get a rounder shape with the direction of the long shore drift. There, the beach should have a gentler slope due to the smaller pebbles. We can now apply this concept to the chosen location:

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Hypothesis Due to the action of longshore drift, the pebbles at Aldeburgh will be smaller and rounder in shape. The beach gradient will vary with the size of the pebbles and there will also be a steeper gradient in Thorpeness since all heavier pebbles will be disposed there.

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Method Of Investigation The following equipment was used to gather the necessary data:

9 1 clinometer 9 2 tape measures 9 4 ranging poles 9 1 clipboard

We started at the back of the beach, where we placed the first pole in the ground. The next pole was positioned at the first change of the beach slope (here it is important that the same length of the poles is in the ground, since otherwise the correct angle can’t be measured). We then measured the distance between those two poles (horizontally, not on the ground) and the angle with the clinometer. A sample of 50 pebbles was collected at the middle between those two poles. To do so, we placed a second tape measure in the middle of the poles and then took a sample of one pebble every 0.1m for 5m in total (‘systematic sampling’) to get a more accurate picture.

Figure 4: Illustration showing the how the measurements should be taken (view from the side).

ranging pole 1

ranging pole 2

change in slope

start

tape measure to measure the distance (d) between the poles

with the clinometer, aim at the same marker

on the other pole to measure the angle


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Figure 5: Illustration showing the how the measurements should be taken (bird’s view).

In order to minimize any random or human errors, we split into three groups and each group worked independently. This will also mean that instead of 50 pebble samples for each interval, we will have 150, which allows us to make a more accurate decision and evaluation. The long axis of each pebble (referred to as ‘size’) in each sample was measured using a calliper. This will be important later on in order to find out whether the pebble size increases with the distance from the sea. The criterion we used to assign each pebble a number from 1 to 6 according to their shape (to compare the shape to the gradient and distance from the sea) can be seen below:

Figure 6: Criterion used to measure a pebble’s size. 1 means ‘very angular’ and 6 means ‘well rounded’.6

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distance (d) between the poles

ranging pole 1 ranging pole 2

dist

ance

= 5

.0m

take

one

sam

ple

ever

y 0.

1m

change in slope

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Results And Analysis

Raw Data

Aldeburgh Group 1:

Pole Number Angle to next pole (+ve or –ve)

Distance to next pole (metres)

1 -3 4.79 2 +3 6.51 3 -3 6.71 4 -10 8.65 5 +5 4.62 6 -3 3.87

Pebble Samples Halfway between Poles 1 & 2 (Size with shape in brackets) 3.8 (4) 4.9 (4) 3.6 (5) 2.8 (5) 3.3 (4) 3.8 (4) 3.4 (4) 2.8 (5) 2.8 (6) 2.5 (4) 2.5 (4) 3.0 (3) 2.4 (3) 2.4 (4) 2.3 (4) 2.5 (4) 2.0 (6) 2.1 (4) 2.2 (6) 1.2 (5) 2.4 (4) 1.9 (4) 2.2 (3) 1.4 (5) 1.0 (6) 0.9 (6) 2.3 (4) 3.0 (5) 2.7 (6) 2.8 (5) 3.2 (6) 2.6 (4) 4.5 (6) 3.9 (6) 3.3 (4) 4.2 (4) 3.0 (4) 2.9 (5) 2.5 (6) 2.8 (5) 1.9 (5) 2.4 (6) 2.0 (5) 2.2 (6) 1.8 (4) 1.5 (6) 2.0 (5) 1.4 (4) 3.2 (4) 2.8 (5) Halfway between Poles 2 & 3 (Size with shape in brackets) 5.8 (3) 3.5 (3) 3.0 (3) 4.7 (5) 2.4 (5) 3.8 (6) 4.9 (2) 3.8 (3) 4.5 (3) 2.6 (2) 6.0 (4) 3.7 (4) 2.8 (6) 1.1 (4) 2.1 (4) 1.4 (4) 2.3 (1) 2.5 (5) 4.9 (5) 2.4 (6) 3.4 (4) 2.8 (5) 2.6 (5) 2.7 (4) 2.6 (4) 2.8 (5) 2.2 (4) 2.8 (3) 3.4 (4) 3.1 (2) 1.5 (4) 2.1 (5) 4.1 (6) 5.9 (2) 6.2 (3) 1.4 (5) 3.1 (5) 3.7 (5) 2.6 (4) 2.6 (4) 2.8 (5) 3.4 (4) 4.5 (6) 2.7 (4) 2.4 (4) 2.8 (4) 3.7 (4) 2.4 (3) 2.3 (6) 2.2 (6) Halfway between Poles 3 & 4 (Size with shape in brackets) 3.6 (5) 3.4 (6) 5.5 (5) 3.6 (5) 3.1 (5) 3.3 (4) 2.8 (4) 2.8 (5) 3.7 (4) 2.5 (5) 3.0 (2) 2.2 (4) 4.0 (4) 3.4 (5) 4.6 (4) 4.4 (5) 3.2 (5) 2.8 (4) 3.4 (6) 2.5 (4) 2.8 (3) 4.5 (4) 2.7 (5) 2.3 (4) 4.0 (4) 6.2 (5) 4.8 (6) 3.4 (2) 2.8 (4) 3.7 (5) 3.4 (4) 4.3 (4) 4.0 (4) 3.0 (3) 4.3 (5) 3.9 (4) 4.0 (6) 2.5 (2) 4.4 (3) 3.5 (6) 3.0 (3) 2.7 (4) 4.1 (5) 4.4 (4) 4.2 (5) 2.8 (4) 3.5 (3) 4.5 (6) 3.5 (6) 3.5 (5)


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Halfway between Poles 4 & 5 (Size with shape in brackets) 8.2 (5) 4.8 (5) 3.3 (5) 4.1 (4) 3.8 (5) 3.5 (5) 3.4 (4) 3.6 (3) 3.4 (6) 3.5 (5) 2.8 (5) 2.7 (4) 4.2 (5) 2.9 (5) 3.2 (4) 2.8 (4) 3.0 (3) 3.0 (5) 3.0 (4) 3.4 (4) 3.0 (5) 2.9 (5) 2.9 (4) 3.2 (3) 2.5 (5) 2.6 (5) 3.1 (4) 3.0 (4) 3.0 (4) 2.4 (3) 2.2 (6) 2.5 (5) 2.5 (3) 2.5 (4) 2.6 (5) 2.5 (4) 2.2 (4) 2.5 (5) 2.4 (5) 2.4 (3) 2.2 (6) 2.2 (6) 2.2 (4) 2.2 (4) 2.3 (4) 2.0 (5) 2.0 (5) 2.2 (3) 1.5 (4) 1.5 (5) Halfway between Poles 5 & 6 (Size with shape in brackets) 6.6 (5) 5.0 (4) 5.2 (4) 4.3 (5) 4.4 (6) 4.0 (5) 4.3 (4) 3.8 (4) 3.5 (3) 3.0 (6) 3.0 (6) 3.5 (4) 2.8 (6) 2.9 (5) 2.5 (4) 2.7 (5) 2.6 (5) 2.5 (6) 2.4 (4) 2.6 (4) 2.4 (5) 3.0 (4) 2.9 (4) 2.8 (5) 2.5 (4) 2.6 (5) 2.5 (4) 2.5 (5) 2.5 (4) 2.5 (4) 2.5 (3) 2.5 (5) 2.4 (4) 2.5 (4) 2.0 (5) 2.8 (4) 2.2 (5) 2.5 (4) 2.2 (4) 2.2 (5) 2.2 (5) 2.1 (4) 1.9 (4) 1.5 (4) 2.0 (4) 1.7 (5) 1.7 (4) 1.2 (5) 1.0 (6) 1.2 (3) Halfway between Poles 6 & 7 (Size with shape in brackets) 4.4 (5) 3.4 (4) 3.8 (4) 4.0 (3) 3.7 (4) 2.6 (4) 2.8 (4) 4.4 (4) 2.8 (4) 2.0 (6) 3.8 (5) 2.9 (5) 3.3 (3) 4.0 (5) 2.7 (4) 2.9 (4) 2.6 (4) 4.1 (6) 2.0 (4) 2.7 (5) 2.4 (4) 4.0 (4) 2.4 (5) 3.9 (5) 2.3 (3) 2.4 (5) 1.8 (4) 2.9 (6) 2.7 (5) 3.3 (3) 3.3 (4) 2.1 (5) 4.8 (6) 2.4 (6) 3.4 (6) 2.1 (4) 3.9 (4) 3.2 (4) 2.2 (4) 3.1 (4) 2.6 (4) 3.3 (5) 3.1 (5) 2.6 (4) 2.1 (5) 2.3 (2) 2.3 (5) 2.0 (6) 3.0 (5) 3.8 (4)


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Group 2:

Pole number Angle to next pole (+ve or –ve)


1 ±0 4.80 2 +4 7.10 3 -4 5.75 4 -10 8.55 5 +5 3.20 6 -15 1.80

Pebble Samples Halfway between Poles 1 & 2 (Size with shape in brackets) 5.0 (5) 4.7 (5) 3.6 (4) 4.0 (4) 2.5 (6) 3.6 (6) 3.5 (5) 2.1 (4) 2.4 (3) 3.4 (3) 2.8 (5) 4.2 (4) 2.4 (2) 3.2 (3) 2.0 (6) 3.1 (6) 2.9 (4) 2.8 (3) 2.8 (3) 2.8 (5) 3.6 (4) 4.2 (4) 2.6 (3) 3.0 (3) 2.8 (3) 3.4 (5) 4.3 (5) 3.6 (4) 4.2 (2) 3.5 (3) 4.7 (5) 3.0 (3) 4.5 (5) 3.3 (1) 3.5 (6) 2.1 (4) 4.6 (6) 4.0 (6) 3.5 (5) 3.0 (4) 4.6 (5) 4.4 (4) 2.5 (3) 3.6 (2) 1.8 (5) 2.5 (5) 3.1 (5) 5.5 (5) 3.0 (5) 2.0 (5) Halfway between Poles 2 & 3 (Size with shape in brackets) 5.5 (5) 7.0 (5) 3.4 (4) 4.1 (5) 3.7 (5) 3.4 (3) 3.5 (3) 2.5 (5) 3.5 (5) 3.9 (4) 4.7 (6) 3.5 (4) 3.1 (5) 3.8 (5) 4.5 (6) 2.5 (4) 4.5 (4) 3.5 (3) 4.5 (4) 3.4 (4) 5.8 (6) 4.7 (4) 2.3 (4) 3.5 (5) 4.6 (6) 6.6 (4) 3.7 (4) 1.4 (3) 2.7 (5) 4.0 (4) 3.5 (4) 4.4 (5) 4.5 (4) 3.7 (4) 3.5 (5) 4.9 (5) 2.5 (5) 3.0 (4) 2.5 (3) 3.1 (5) 2.9 (6) 3.1 (3) 3.1 (5) 3.1 (3) 2.9 (3) 3.5 (6) 3.9 (4) 3.0 (5) 2.7 (4) 3.8 (4) Halfway between Poles 3 & 4 (Size with shape in brackets) 4.0 (5) 2.7 (4) 5.3 (5) 2.5 (3) 3.5 (4) 2.7 (3) 3.9 (3) 3.7 (3) 4.5 (3) 3.9 (4) 3.0 (5) 2.8 (4) 4.8 (5) 2.0 (3) 3.5 (5) 3.3 (4) 3.0 (4) 2.8 (5) 4.4 (4) 3.7 (3) 2.8 (5) 2.7 (5) 4.1 (4) 2.5 (3) 3.6 (5) 3.9 (2) 2.9 (4) 3.4 (4) 4.3 (6) 4.2 (5) 3.8 (5) 3.5 (3) 4.4 (4) 2.5 (3) 3.7 (6) 4.3 (6) 2.8 (4) 2.8 (6) 3.3 (2) 4.6 (3) 4.5 (5) 5.2 (5) 3.5 (4) 4.6 (2) 4.2 (3) 3.2 (6) 2.8 (4) 3.2 (4) 3.2 (3) 3.2 (6) Halfway between Poles 4 & 5 (Size with shape in brackets) 5.0 (6) 2.3 (3) 3.0 (5) 3.4 (3) 3.1 (5) 3.1 (3) 2.3 (4) 2.9 (3) 2.7 (3) 2.3 (4) 5.1 (5) 2.9 (4) 3.2 (6) 4.1 (3) 3.2 (4) 4.1 (3) 2.8 (4) 2.3 (3) 2.5 (4) 2.0 (3) 2.6 (3) 3.3 (4) 3.2 (5) 3.5 (4) 2.6 (3) 2.7 (4) 2.5 (2) 2.3 (3) 2.3 (4) 1.5 (3) 3.5 (5) 2.3 (3) 3.4 (4) 4.0 (5) 2.7 (4) 2.2 (6) 3.2 (3) 2.4 (4) 2.2 (3) 1.8 (4) 4.5 (3) 1.9 (4) 3.0 (2) 3.4 (4) 2.9 (4) 2.7 (5) 2.5 (2) 2.3 (5) 2.2 (4) 2.1 (4)


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Halfway between Poles 5 & 6 (Size with shape in brackets) 4.5 (5) 4.7 (5) 3.0 (5) 2.0 (3) 2.8 (5) 1.4 (4) 3.6 (6) 2.3 (3) 2.8 (4) 2.4 (4) 3.0 (2) 4.0 (5) 3.4 (5) 2.0 (3) 3.0 (5) 1.4 (4) 2.4 (5) 3.8 (2) 2.8 (3) 2.3 (3) 3.0 (4) 2.5 (3) 2.9 (5) 3.6 (2) 3.5 (5) 2.5 (2) 3.0 (3) 4.2 (5) 2.4 (3) 3.0 (3) 4.9 (6) 2.1 (3) 3.8 (3) 2.7 (2) 4.7 (5) 2.6 (5) 2.0 (3) 3.0 (5) 3.3 (3) 3.2 (2) 3.8 (6) 3.0 (6) 3.5 (3) 2.1 (4) 3.5 (2) 4.0 (3) 2.7 (3) 2.6 (5) 2.0 (3) 3.5 (4) Halfway between Poles 6 & 7 (Size with shape in brackets) 3.1 (6) 3.1 (5) 3.1 (2) 3.2 (4) 2.6 (3) 1.9 (3) 2.6 (4) 1.6 (4) 1.5 (3) 1.2 (2) 3.7 (6) 2.7 (5) 0.4 (3) 2.9 (5) 1.7 (4) 1.8 (5) 2.3 (5) 1.4 (4) 2.2 (1) 1.8 (3) 0.3 (5) 4.2 (4) 2.3 (3) 1.9 (5) 2.5 (3) 2.9 (4) 0.2 (3) 2.6 (3) 2.1 (3) 1.5 (3) 0.3 (2) 3.3 (6) 0.3 (6) 2.1 (4) 2.5 (3) 1.7 (3) 2.1 (4) 2.1 (2) 1.6 (4) 1.3 (3) 0.3 (4) 4.1 (3) 3.4 (5) 2.4 (3) 1.9 (4) 2.5 (3) 2.6 (3) 2.1 (4) 1.5 (3) 0.1 (3)


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Group 3:



1 -3 4.7 2 +5 6.55 3 -4 6.4 4 -10 8.6 5 +5 3.5 6 -5 6



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Halfway between Poles 5 & 6 (Size with shape in brackets) 4.2 (4) 5.1 (6) 3.0 (4) 3.3 (3) 3.6 (4) 2.6 (5) 8.0 (6) 4.5 (5) 2.6 (3) 3.7 (5) 2.7 (3) 2.2 (3) 5.0 (4) 3.4 (6) 4.4 (2) 3.4 (2) 3.6 (4) 3.1 (6) 2.7 (3) 4.1 (4) 2.6 (6) 3.5 (2) 2.5 (3) 3.4 (3) 2.7 (3) 2.5 (3) 2.0 (3) 2.2 (4) 1.7 (3) 3.1 (3) 2.3 (5) 3.6 (4) 2.7 (3) 2.5 (3) 3.5 (2) 3.1 (2) 2.3 (2) 3.3 (5) 2.9 (2) 2.5 (5) 2.7 (2) 2.5 (5) 2.5 (3) 2.0 (3) 1.8 (3) 2.8 (2) 1.5 (3) 2.8 (2) 1.5 (2) 1.6 (6) Halfway between Poles 6 & 7 (Size with shape in brackets) 7.8 (6) 4.7 (3) 4.5 (6) 3.3 (4) 7.4 (3) 3.4 (3) 2.6 (5) 3.6 (3) 4.1 (3) 2.4 (3) 2.4 (3) 2.6 (3) 2.4 (3) 2.4 (3) 2.1 (2) 3.1 (2) 2.5 (5) 2.5 (4) 2.4 (2) 3.0 (3) 2.4 (5) 2.7 (5) 2.4 (4) 2.3 (4) 2.0 (3) 2.6 (2) 1.3 (3) 2.1 (6) 3.0 (2) 2.7 (3) 2.3 (3) 2.3 (3) 1.7 (2) 1.5 (2) 3.4 (5) 2.6 (2) 2.6 (2) 1.9 (5) 2.0 (2) 2.4 (3) 2.7 (3) 1.6 (2) 2.0 (3) 2.6 (4) 2.4 (2) 2.3 (3) 2.1 (2) 2.0 (2) 3.1 (3) 1.7 (2)


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Thorpeness Group 1:

Pole Number Angle to next pole (+ve or –ve)


1 +9 4.43 2 +5 7.77 3 +12 7.65 4 -3 7.67 5 +1 3.70 6 -5 9.05 7 +6 2.35 8 -9 5.75

Pebble Samples Halfway between Poles 1 & 2 (Size with shape in brackets) 3.9 (2) 4.1 (5) 3.5 (3) 4.4 (6) 4.4 (4) 5.5 (4) 3.3 (4) 4.0 (5) 2.5 (4) 3.0 (5) 2.6 (6) 5.0 (4) 3.5 (5) 3.6 (6) 2.6 (4) 2.6 (6) 2.9 (4) 2.6 (4) 2.9 (4) 2.6 (5) 2.8 (5) 2.5 (5) 2.5 (4) 3.1 (4) 3.1 (4) 3.0 (4) 2.4 (5) 2.4 (5) 2.7 (4) 2.7 (4) 3.0 (5) 2.9 (4) 4.2 (6) 3.0 (4) 2.2 (3) 1.2 (2) 2.6 (3) 2.8 (3) 2.2 (4) 2.0 (4) 2.4 (4) 2.1 (4) 1.7 (4) 2.9 (4) 1.5 (4) 2.3 (4) 1.9 (4) 2.2 (4) 1.2 (4) 2.0 (5) Halfway between Poles 2 & 3 (Size with shape in brackets) 5.4 (6) 6.2 (5) 4.3 (4) 4.0 (4) 4.5 (4) 3.2 (5) 3.5 (5) 3.6 (6) 4.0 (5) 3.7 (5) 3.5 (3) 5.4 (6) 3.7 (3) 4.8 (6) 3.0 (5) 4.7 (6) 2.8 (4) 3.0 (5) 3.4 (5) 3.8 (4) 5.0 (5) 4.0 (5) 5.9 (5) 2.4 (4) 3.8 (5) 4.3 (5) 3.9 (5) 3.7 (5) 3.3 (6) 2.5 (5) 4.9 (3) 5.0 (4) 3.1 (5) 3.6 (6) 2.9 (4) 4.5 (5) 4.4 (3) 3.5 (3) 2.7 (5) 2.9 (4) 3.7 (6) 5.1 (4) 4.1 (6) 3.6 (4) 3.6 (4) 4.5 (3) 3.5 (3) 2.8 (3) 3.6 (4) 4.2 (6) Halfway between Poles 3 & 4 (Size with shape in brackets) 4.5 (6) 4.6 (4) 4.5 (6) 3.1 (6) 4.3 (5) 3.4 (5) 3.9 (5) 2.9 (6) 3.8 (6) 5.1 (6) 3.9 (5) 3.9 (3) 3.4 (5) 3.2 (6) 4.8 (6) 4.9 (4) 3.1 (4) 3.5 (5) 3.5 (4) 4.5 (5) 2.9 (6) 2.9 (5) 3.0 (4) 4.0 (4) 4.9 (5) 3.8 (4) 3.1 (4) 2.1 (6) 3.0 (4) 3.0 (5) 3.3 (5) 4.3 (4) 2.9 (4) 3.9 (4) 3.8 (6) 3.1 (4) 2.5 (4) 2.2 (5) 3.0 (6) 2.5 (5) 3.3 (5) 3.0 (4) 3.4 (4) 2.9 (5) 3.4 (4) 2.4 (3) 4.5 (3) 2.1 (3) 3.9 (4) 2.4 (3)


% 15%

Halfway between Poles 4 & 5 (Size with shape in brackets) 5.5 (6) 5.3 (4) 4.3 (6) 3.8 (4) 4.5 (3) 3.8 (4) 4.2 (4) 3.8 (5) 2.6 (6) 2.8 (3) 4.4 (3) 2.9 (5) 3.9 (5) 3.2 (6) 2.9 (4) 6.1 (3) 4.1 (6) 2.3 (1) 3.0 (4) 4.4 (4) 4.0 (4) 3.0 (5) 4.2 (6) 4.3 (5) 4.4 (6) 2.8 (4) 4.3 (4) 4.9 (6) 5.0 (4) 4.2 (4) 3.8 (5) 2.5 (6) 2.5 (4) 3.0 (6) 2.5 (4) 4.6 (6) 3.6 (3) 2.9 (5) 3.2 (5) 3.3 (6) 3.0 (5) 3.8 (3) 2.9 (5) 3.7 (4) 3.0 (6) 3.2 (5) 3.0 (4) 3.0 (5) 3.4 (3) 3.0 (5) Halfway between Poles 5 & 6 (Size with shape in brackets) 4.0 (4) 5.2 (5) 3.5 (3) 3.5 (3) 4.8 (3) 3.4 (4) 3.3 (4) 2.4 (5) 3.0 (5) 2.7 (4) 4.0 (4) 3.6 (5) 2.8 (5) 2.6 (6) 3.5 (4) 3.0 (4) 1.8 (4) 3.0 (5) 1.8 (5) 2.5 (4) 1.9 (4) 3.1 (5) 2.7 (4) 3.6 (4) 1.9 (4) 1.8 (3) 3.7 (5) 3.0 (4) 2.5 (3) 1.9 (5) 2.3 (5) 2.5 (6) 3.1 (3) 2.1 (4) 2.2 (3) 1.9 (5) 2.2 (2) 2.9 (6) 1.6 (6) 2.0 (6) 2.5 (5) 3.0 (3) 2.9 (4) 2.4 (5) 2.9 (5) 1.9 (4) 2.9 (4) 1.8 (4) 1.2 (4) 1.1 (2) Halfway between Poles 6 & 7 (Size with shape in brackets) 3.7 (4) 3.5 (4) 5.4 (3) 3.2 (3) 2.5 (4) 2.3 (4) 2.2 (5) 2.9 (5) 4.1 (5) 3.3 (4) 3.3 (5) 2.3 (3) 2.1 (5) 2.1 (4) 4.4 (3) 2.9 (4) 3.3 (3) 3.3 (2) 2.5 (6) 2.0 (2) 2.9 (4) 2.5 (4) 3.9 (4) 2.3 (4) 2.5 (4) 2.6 (3) 2.5 (5) 2.8 (3) 2.9 (5) 2.0 (4) 3.5 (4) 1.6 (3) 2.4 (5) 1.8 (5) 2.5 (4) 2.5 (4) 2.4 (4) 2.8 (5) 2.7 (3) 2.1 (4) 2.1 (3) 1.6 (4) 1.7 (3) 2.5 (4) 2.0 (4) 2.2 (3) 1.9 (4) 1.8 (5) 2.9 (2) 1.6 (6) Halfway between Poles 7 & 8 (Size with shape in brackets) 3.5 (5) 3.5 (4) 4.4 (5) 3.6 (3) 3.9 (4) 2.7 (4) 4.7 (6) 2.4 (4) 3.0 (4) 2.5 (3) 4.0 (6) 2.5 (3) 2.5 (4) 3.3 (5) 3.0 (5) 3.1 (6) 3.1 (5) 2.2 (5) 3.0 (3) 2.7 (4) 3.1 (1) 2.1 (4) 2.3 (4) 2.8 (4) 2.8 (4) 3.4 (5) 2.8 (3) 3.3 (4) 2.2 (5) 3.3 (4) 3.6 (4) 3.9 (4) 3.4 (5) 3.2 (3) 3.0 (3) 3.4 (3) 3.0 (4) 2.1 (3) 2.8 (3) 2.4 (5) 3.3 (5) 2.3 (3) 2.0 (4) 1.7 (4) 2.0 (4) 2.5 (4) 3.1 (4) 1.8 (3) 2.9 (3) 1.8 (2) Halfway between Poles 8 & 9 (Size with shape in brackets) 3.8 (4) 2.1 (5) 3.0 (3) 4.9 (4) 2.7 (4) 2.1 (3) 3.1 (3) 3.5 (5) 2.2 (3) 2.9 (5) 3.5 (2) 2.1 (6) 2.5 (3) 2.6 (4) 2.4 (4) 2.3 (6) 2.7 (2) 3.0 (3) 2.3 (3) 1.9 (4) 2.1 (4) 2.2 (4) 1.8 (3) 1.5 (6) 1.2 (4) 2.9 (6) 2.2 (4) 2.0 (3) 2.0 (5) 2.5 (4) 4.1 (3) 2.3 (5) 2.8 (3) 2.2 (5) 1.5 (6) 2.1 (5) 3.1 (3) 1.9 (4) 2.5 (4) 1.9 (4) 2.5 (4) 1.9 (4) 2.6 (6) 1.6 (4) 2.0 (4) 3.5 (5) 1.6 (3) 1.9 (5) 2.2 (4) 2.4 (4)


% 16%

Group 2:

Pole number Angle to next pole (+ve or -ve)


1 +3 17.90 2 +2 6.20 3 +5 8.75 4 -5 8.00 5 -7 4.90 6 -2 6.00 7 -5 5.20

Pebble Samples Halfway between Poles 1 & 2 (Size with shape in brackets) 1.6 (5) 2.5 (4) 0.3 (5) 5.5 (4) 3.2 (4) 2.3 (3) 2.1 (4) 1.9 (4) 1.9 (1) 1.6 (5) 4.0 (5) 3.6 (4) 3.5 (5) 2.5 (4) 2.1 (5) 2.9 (4) 1.3 (4) 0.2 (4) 1.5 (3) 0.1 (3) 2.6 (5) 2.1 (5) 0.3 (6) 2.3 (3) 2.3 (5) 2.1 (5) 0.2 (4) 1.6 (4) 2.1 (3) 1.2 (4) 2.2 (4) 3.5 (4) 3.6 (5) 2.7 (4) 3.7 (4) 0.2 (6) 2.4 (4) 1.4 (3) 1.7 (4) 0.9 (3) 1.5 (4) 3.6 (6) 3.3 (5) 3.5 (4) 2.4 (5) 0.2 (5) 2.3 (5) 1.3 (3) 1.4 (3) 1.1 (3) Halfway between Poles 2 & 3 (Size with shape in brackets) 4.9 (5) 4.0 (6) 4.2 (5) 4.1 (5) 3.2 (6) 4.4 (3) 2.2 (4) 3.0 (5) 2.5 (5) 2.3 (4) 2.9 (5) 4.9 (6) 3.5 (6) 4.5 (5) 4.4 (2) 2.9 (4) 3.0 (4) 2.9 (5) 1.9 (5) 2.2 (2) 3.2 (5) 5.2 (5) 2.8 (6) 3.5 (5) 3.5 (3) 3.9 (5) 4.0 (4) 2.6 (5) 1.9 (5) 2.5 (5) 3.8 (4) 3.8 (5) 3.8 (2) 3.2 (4) 3.4 (4) 3.0 (5) 2.5 (5) 1.9 (5) 2.1 (3) 2.2 (4) 2.9 (6) 3.2 (5) 2.8 (5) 2.6 (6) 3.5 (2) 2.8 (5) 3.2 (4) 2.3 (3) 1.6 (4) 1.8 (3) Halfway between Poles 3 & 4 (Size with shape in brackets) 3.7 (4) 3.4 (3) 1.9 (4) 3.0 (5) 3.7 (4) 2.2 (4) 2.9 (4) 3.0 (4) 2.0 (4) 4.1 (4) 4.8 (4) 3.7 (4) 2.1 (3) 2.4 (5) 3.5 (4) 2.2 (4) 2.6 (4) 3.5 (4) 3.2 (3) 1.7 (3) 6.6 (5) 4.3 (4) 1.5 (4) 2.6 (6) 2.9 (4) 2.7 (3) 1.9 (4) 3.0 (3) 3.5 (4) 3.4 (5) 3.5 (3) 2.7 (3) 4.1 (3) 2.3 (3) 2.4 (6) 2.5 (4) 2.8 (4) 2.5 (4) 2.7 (4) 2.9 (4) 3.0 (5) 4.2 (4) 3.6 (3) 2.3 (3) 2.3 (4) 2.6 (4) 3.2 (4) 1.5 (3) 3.4 (4) 2.8 (5) Halfway between Poles 4 & 5 (Size with shape in brackets) 3.2 (6) 3.6 (4) 2.5 (5) 2.8 (5) 3.4 (4) 2.7 (3) 2.7 (4) 3.2 (3) 3.9 (5) 1.9 (4) 5.3 (5) 0.2 (4) 2.9 (4) 3.8 (5) 2.4 (5) 0.3 (4) 2.3 (5) 2.8 (6) 0.3 (5) 1.7 (3) 4.2 (5) 3.7 (4) 2.8 (5) 2.6 (4) 3.5 (4) 3.7 (3) 2.9 (3) 2.0 (3) 2.6 (3) 2.8 (4)


% 17%

4.0 (6) 3.9 (6) 2.8 (2) 0.3 (4) 2.4 (3) 2.6 (3) 2.9 (4) 2.7 (3) 2.7 (6) 1.7 (3) 3.4 (5) 3.1 (5) 0.3 (4) 2.5 (4) 2.9 (5) 3.6 (4) 3.1 (4) 2.8 (5) 2.5 (4) 2.2 (4) Halfway between Poles 5 & 6 (Size with shape in brackets) 4.0 (4) 3.3 (5) 3.6 (4) 3.8 (5) 2.6 (3) 3.2 (5) 2.4 (6) 2.2 (4) 2.2 (4) 2.3 (4) 2.5 (6) 2.6 (6) 2.6 (4) 2.9 (4) 2.5 (4) 2.5 (6) 2.5 (6) 2.3 (4) 2.0 (4) 1.9 (5) 3.2 (5) 2.7 (5) 3.5 (6) 3.5 (4) 3.2 (6) 2.6 (6) 2.3 (4) 2.0 (4) 2.1 (4) 2.0 (3) 3.0 (5) 2.2 (6) 3.1 (5) 3.0 (4) 3.1 (4) 2.4 (5) 2.6 (5) 2.5 (5) 1.6 (5) 1.6 (6) 4.4 (4) 3.2 (4) 4.4 (6) 3.2 (4) 2.8 (5) 2.0 (4) 2.2 (3) 2.2 (4) 2.1 (5) 1.7 (4) Halfway between Poles 6 & 7 (Size with shape in brackets) 4.8 (6) 5.4 (5) 5.0 (4) 2.7 (4) 2.3 (4) 2.2 (3) 3.3 (5) 2.2 (3) 2.2 (4) 0.2 (2) 4.3 (6) 2.5 (4) 3.4 (3) 3.0 (4) 2.2 (4) 4.0 (3) 3.3 (3) 1.9 (2) 2.4 (4) 1.6 (2) 4.2 (6) 2.8 (4) 4.1 (5) 2.6 (3) 2.4 (3) 2.1 (4) 0.2 (5) 2.3 (2) 2.5 (2) 1.0 (2) 3.8 (5) 3.0 (5) 3.3 (4) 4.2 (5) 2.8 (3) 1.7 (4) 2.8 (5) 1.5 (1) 2.5 (5) 0.2 (4) 3.4 (4) 3.9 (4) 3.0 (4) 2.4 (4) 2.1 (3) 2.1 (4) 2.1 (3) 2.1 (2) 3.3 (2) 2.2 (3) Halfway between Poles 7 & 8 (Size with shape in brackets) 6.0 (5) 4.1 (3) 5.0 (4) 3.9 (4) 5.5 (1) 3.2 (5) 3.0 (4) 2.0 (2) 2.6 (3) 2.2 (3) 3.5 (5) 3.4 (3) 3.3 (4) 3.2 (4) 4.1 (4) 2.1 (4) 2.4 (3) 1.9 (3) 3.0 (2) 1.5 (3) 3.9 (4) 2.9 (5) 4.9 (4) 3.9 (4) 2.6 (3) 2.9 (4) 2.0 (3) 2.5 (3) 2.1 (3) 1.5 (2) 3.5 (6) 3.7 (4) 4.0 (3) 4.6 (4) 2.2 (4) 2.6 (4) 2.5 (3) 2.9 (4) 1.7 (3) 1.7 (2) 3.3 (5) 3.5 (5) 2.9 (3) 4.5 (5) 2.2 (4) 3.0 (3) 1.3 (3) 1.6 (2) 1.5 (4) 2.5 (3)


% 18%

Group 3:



1 +5 20.20 2 -5 10.60 3 -7 5.80 4 +6 5.85 5 -11 3.85



% 19%

Halfway between Poles 5 & 6 (Size with shape in brackets) 3.1 (6) 2.9 (5) 3.6 (6) 3.3 (3) 2.4 (5) 1.9 (3) 2.5 (5) 2.7 (3) 2.0 (4) 3.4 (3) 4.4 (5) 3.5 (6) 2.3 (3) 2.9 (3) 2.7 (3) 1.9 (4) 2.9 (3) 2.1 (4) 2.0 (5) 1.9 (5) 3.5 (4) 1.3 (4) 1.9 (4) 2.5 (3) 3.1 (2) 2.1 (3) 2.0 (4) 2.1 (3) 2.3 (3) 3.1 (3) 1.9 (6) 2.4 (4) 1.9 (3) 4.4 (6) 2.3 (3) 2.2 (4) 2.0 (3) 1.7 (2) 3.1 (3) 1.8 (2) 2.5 (3) 2.3 (5) 2.3 (5) 2.1 (2) 1.8 (4) 3.1 (2) 1.6 (2) 1.6 (3) 2.4 (5) 1.6 (4)


% 20%

Beach Profiles

Aldeburgh Group 1:

Pole

1Po

le 2

Pole

3Po

le 4

Pole

5Po

le 6

Pole

7

SEA

Average pebble size: 3.00cmAverage shape: 4.46

Distance= 3.87mAngle= -3° 5m

5m






Distance= 4.62mAngle= +5°

Distance= 8.65mAngle= -10°




Figure"7:"Beach"profile"for"group"1"in"Thorpeness."


% 21%

Group 2:

Pole

1Po

le 2

Pole

3Po

le 4

Pole

5Po

le 6

Pole

7

SEA







Distance= 4.80mAngle= ±0°





Distance= 1.80mAngle= -15° 5m

5m



% 22%

Group 3:

Pole

1Po

le 2

Pole

3Po

le 4

Pole

5Po

le 6

Pole

7

SEA













5m5m



% 23%

Thorpeness Group 1:

Pole

1Po

le 2

Pole

3Po

le 4

Pole

5Po

le 6

Pole

7SEA



5m5m

Pole

8Po

le 9















Figure"10:"Beach"profile"for"group"1"in"Aldeburgh."


% 24%

Group 2:

Pole

1Po

le 2

Pole

3Po

le 4

Pole

5Po

le 6

Pole

7

SEA


5m5m

Pole

8
















% 25%

Group 3:

Pole

1Po

le 2

Pole

3Po

le 4

Pole

5Po

le 6

SEA

5m5m













% 26%

Examining The Results Using Spearman’s Rank Correlation Coefficient Diagram Now the data has to be processed and it looks like that for most of them, there is a positive correlation, just as we expected it due to the reasons explained under the section ‘theoretical background’. However, it could be that this is purely due to luck and that the results are insignificant. Therefore, the data has to be further examined using Spearman’s rank correlation coefficients. To do so, the correlation of the data has to be found first (using Microsoft Excel) and it can then be compared to the diagram below (Figure 16) in order to find out the data is significant at the 95% confidence level. The results gained from this investigation are shown below:

1. Distance from sea and pebble size Aldeburgh Group Data

pairs Degrees of freedom

Data correlation

Spearman’s rank correlation coefficient

Is the correlation significant?

1 6 4 0.053358264 ~0.90 No 2 6 4 0.772559882 ~0.90 No 3 6 4 0.916329941 ~0.90 Yes All 18 16 0.475557960 ~0.55 No Thorpeness 1 8 6 0.605043333 ~0.80 No 2 7 5 -0.473881718 ~0.85 No 3 5 3 0.747133233 ~0.95 No All 20 18 0.266494302 ~0.50 No Figure 13

2. Beach gradient and pebble size Aldeburgh Group Data


Correlation Spearman’s rank correlation coefficient

Significance

1 6 4 -0.048479103 ~0.90 No 2 6 4 0.685099913 ~0.90 No 3 6 4 0.255772986 ~0.90 No


% 27%

All 18 16 0.470393895 ~0.55 No Thorpeness 1 8 6 0.446200841 ~0.80 No 2 7 5 -0.096472700 ~0.85 No 3 5 3 0.234463164 ~0.95 No All 20 18 0.303358701 ~0.50 No Figure 14

3. Distance from sea and pebble shape

Aldeburgh Group Data



Significance

1 6 4 0.871668522 ~0.90 No 2 6 4 0.899013689 ~0.90 No 3 6 4 0.871668522 ~0.90 No All 18 16 0.355267786 ~0.55 No Thorpeness 1 8 6 0.625651073 ~0.80 No 2 7 5 0.037708997 ~0.85 No 3 5 3 -0.372445813 ~0.95 No All 20 18 0.287053211 ~0.50 No Figure 15


% 28%

Figure 16: Spearman’s rank correlation coefficient diagram.7

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% 29%

Examining The Results Using “R squared” „R squared is a statistical measure of how well a regression line approximates real data points […] [It] can be used as an indicator of the reliability of a relationship identified by regression analysis. An R squared of 0.8 indicates that 80% of the change in one variable is explained by a change in the related variable. “8

Therefore, “R squared” should now be used in order to find out whether the correlations that were found in the graphs are significant and if there is a linear relationship between them. The correlations will then be grouped into the following five categories: R2 Correlation 0.00-0.50 Weak 0.50-0.75 Moderate 0.75-0.80 Strong 0.80-0.99 Very strong 1.00 Perfect Figure 17

1. Distance from sea and pebble size

Aldeburgh Group R2 Correlation 1 0.00285 Weak 2 0.59685 Moderate 3 0.83966 Strong All 0.22616 Weak Thorpeness 1 0.36608 Weak 2 0.22456 Weak 3 0.55821 Moderate All 0.07102 Weak Figure 18

2. Beach gradient and pebble size

Aldeburgh Group R2 Correlation 1 0.00235 Weak

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% 30%

2 0.69584 Moderate 3 0.06542 Weak All 0.24764 Weak Thorpeness 1 0.19910 Weak 2 0.00931 Weak 3 0.05497 Weak All 0.09203 Weak Figure 19

3. Distance from sea and pebble shape

Aldeburgh Group R2 Correlation 1 0.00040 Weak 2 0.80823 Strong 3 0.75981 Moderate All 0.12622 Weak Thorpeness 1 0.39144 Weak 2 0.00142 Weak 3 0.13872 Weak All 0.08240 Weak Figure 20

The analysis of the data using “R squared” showed that most of the correlations can only be categorized as “weak”. There were also three moderate relationships and two strong correlations. Overall, it can be seen that this analysis reflects the results that have been gained from Spearman’s rank correlation coefficient, which seems to suggest that we will not be able to draw any valid conclusions from the data.


% 31%

Mean Pebble Size Compared To Distance From Sea

Aldeburgh Group 1:

Figure 21: Graph comparing the mean pebble size and the distance from the sea for group 1 in Aldeburgh.

Group 2:


Group 3:

0%

0.5%

1%

1.5%

2%

2.5%

3%

3.5%

4%

0% 5% 10% 15% 20% 25% 30% 35%

mean"pebble"size"(in"cm

)"

distance"from"the"sea"(in"m)"

Group"1"

0%

0.5%

1%

1.5%

2%

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0% 5% 10% 15% 20% 25% 30% 35%


)"


Group"2"


% 32%


All groups:

Figure 24: Graph comparing the mean pebble size and the distance from the sea for all groups in Aldeburgh.

0%

0.5%

1%

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Group"3"

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0% 5% 10% 15% 20% 25% 30% 35% 40%


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All"groups"


% 33%

Thorpeness Group 1:

Figure 25: Graph comparing the mean pebble size and the distance from the sea for group 1 in Thorpeness.

Group 2:


0%

0.5%

1%

1.5%

2%

2.5%

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0% 5% 10% 15% 20% 25% 30% 35% 40% 45% 50%


)"


Group"1"

0%

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Group"2"


% 34%

Group 3:


All groups:

Figure 28: Graph comparing the mean pebble size and the distance from the sea for all groups in Thorpeness.

0%

0.5%

1%

1.5%

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Group"3"

0%

0.5%

1%

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2.5%

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4.5%

0% 10% 20% 30% 40% 50% 60%


)"


All"groups"


% 35%

Both Locations

Figure 29: Graph comparing the mean pebble size and the distance from the sea in Aldeburgh and Thorpeness separately.

%

Figure 30: Graph comparing the mean pebble size and the distance from the sea in Aldeburgh and Thorpeness.

0%

0.5%

1%

1.5%

2%

2.5%

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0% 10% 20% 30% 40% 50% 60%


)"


Aldeburgh"and"Thorpeness"

Thorpeness%

Aldeburgh%

0%

0.5%

1%

1.5%

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2.5%

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3.5%

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4.5%

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)"




% 36%

Standard Deviation For Pebble Sizes Aldeburgh

Poles Group 1 Group 2 Group 3 1-2 0.842377588 0.859246181 0.878280138 2-3 1.191301809 1.041698613 1.288579062 3-4 0.814923309 0.748929903 1.012474197 4-5 0.993047834 0.761839878 0.794984277 5-6 1.038491213 0.811310052 1.089359445 6-7 0.742600835 0.991614845 1.197178349 Figure 31

Thorpeness

Poles Group 1 Group 2 Group 3 1-2 0.878179936 1.158103622 0.763821969 2-3 0.858000000 0.869997701 0.994635612 3-4 0.773307183 0.898667903 0.932171658 4-5 0.851859143 1.041439389 1.079675877 5-6 0.832752064 0.660608810 0.689814468 6-7 0.761093950 1.120401714 7-8 0.660209058 1.081916818 8-9 0.698065899 Figure 32


% 37%

Analysis Looking at the graphs that show how the mean pebble size varies with the distance from the sea (Figure 21-30), a mixture of results can be recognized. Both locations showed that the bigger pebbles can be found further away from the sea. This is what we had expected. However, there was also one graph that showed a negative correlation (Figure 26). Combining those results with the other groups still showed a positive correlation (Figure 28), which could mean that the overall result is still significant.

Furthermore, the above standard deviations (Figure 31-32) all vary between ~0.66 and ~1.29. This seems to suggest that at least for some measurements, there was a big spread of data from the mean. It was hoped that all pebbles on a particular slope would be the same size, as this would support the theory that pebble size influenced beach gradient. However, there are too many locations with a big standard deviation, which means that the pebbles there were not very similar in size and the results received from this data are unreliable. Even if the correlation was significant at those locations, we know that there were both - much bigger and much smaller - particles at that location which suggests that the hypothesis must be rejected.

Using Spearman’s rank correlation coefficient it was then found that only group 3’s results in Aldeburgh are significant at the 95% confidence level. All other results, even when combining all three groups for each location to reduce errors and to make the results more accurate are not significant.

We also said that in theory, the pebble sizes should be smaller in Aldeburgh when compared to Thorpeness because they are subject to more attrition. Taking a look at Figure 29 it can be seen that the pebbles in Aldeburgh were consistently bigger than those in Thorpeness, which was clearly not expected.


% 38%

Mean Pebble Size Compared To Beach Gradient

Aldeburgh Group 1:

Figure 33: Graph comparing the beach gradient and the mean pebble size for group 1 in Aldeburgh.

Group 2:


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Group 3:


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Figure 36: Graph comparing the beach gradient and the mean pebble size for all groups in Aldeburgh.

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Thorpeness Group 1:

Figure 37: Graph comparing the beach gradient and the mean pebble size for group 1 in Thorpeness.

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Group 3:


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Figure 40: Graph comparing the beach gradient and the mean pebble size for all groups in Thorpeness.

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Both Locations

Figure 41: Graph comparing the beach gradient and the mean pebble size in Aldeburgh and Thorpeness separately.

Figure 42: Graph comparing the beach gradient and the mean pebble size in Aldeburgh and Thorpeness separately.

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Analysis Again, it seems that there is a clear positive correlation (the bigger the gradient, the bigger the pebbles found at that place). This was expected and predicted in the hypothesis. It is due to the fact that at places where there are bigger pebbles (and the gaps between them are also bigger), the waves percolate into the ground. The backwash therefore loses a lot of its energy and will not pull back any of the heavier and bigger pebbles. The bigger pebbles will stay at that place and continue to build up to form a steeper slope. On the other hand, where pebbles are smaller (and consequently the gaps between them are smaller as well), the wave does not percolate into the ground, keeps most of its energy and pulls back bigger pebbles forming a gentler slope.

There are some exceptions (Figure 33, Figure 38), which however do not affect the overall picture (Figure 36, Figure 40). There is a great spread of the data points from the mean in all graphs and the value of R2 ranges from 0.00235 to 0.69584, which suggests that there is no linear correlation. Looking at Spearman’s rank correlation coefficients, it can be seen that none of the correlations is significant at the 95% confidence level (Figure 19). However, it is now to be considered that only the stretches of beach descending towards the sea are actually affected by the waves. Therefore, the whole analysis is now done again, this time only including negative angles. Aldeburgh, group 1:

Figure 43: Graph comparing the negative beach gradients and the mean pebble size for group 1 in Aldeburgh.

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Aldeburgh, all groups:

Figure 46: Graph comparing the negative beach gradients and the mean pebble size for all groups in Aldeburgh.

Thorpeness, group 1:

Figure 47: Graph comparing the negative beach gradients and the mean pebble size for group 1 in Thorpeness.

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Thorpeness, all groups:

Figure 50: Graph comparing the negative beach gradients and the mean pebble size for all groups in Thorpeness.

For most of the above graphs, it is not possible to use Spearman’s rank correlation coefficient, as the degrees of freedom in that case would be either 1 or 2 and the graph does not give any results for such a low number of data pairs. The only thing that can be done is combining all results for each beach (Figure 46, Figure 50) and use their correlation to examine the significance. All groups Aldeburgh Data pairs

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11 9 0.596053649 ~0.67 No All groups Thorpeness 10 8 0.501906618 ~0.73 No Figure 51

Even when only considering negative angles – because they are the ones that are likely to be affected by the waves – no significant correlation can be found. To make sure that this is really the case, we will now apply the “R squared” test to these results.

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Aldeburgh Group R2 Correlation 1 0.04172 Weak 2 0.65101 Moderate 3 0.04710 Weak All 0.35528 Weak Thorpeness 1 0.72498 Moderate 2 0.00296 Weak 3 0.93130 Very strong All 0.24751 Weak Figure 52

The “R squared” test basically proved what Spearman’s rank correlation coefficient had already shown. The result whose correlation is “very strong” can be ignored, since it only consists of three data pairs. Two points will always form a straight line and in this case, the third data item is coincidentally close to that line.

Overall it can be said that even though there is a positive correlation between the beach gradient and the mean pebble size, it has been shown that this correlation is insignificant.


% 49%

Shape Compared To Distance From Sea

Aldeburgh Group 1:

Figure 53: Graph comparing the pebble shape and the distance from the sea for group 1 in Aldeburgh.

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Figure 56: Graph comparing the pebble shape and the distance from the sea for all groups in Aldeburgh.

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Thorpeness Group 1:

Figure 57: Graph comparing the pebble shape and the distance from the sea for group 1 in Thorpeness.

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Figure 60: Graph comparing the pebble shape and the distance from the sea for all groups in Thorpeness.

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Both Locations

Figure 61: Graph comparing the pebble shape and the distance from the sea in Aldeburgh and Thorpeness separately.

Figure 62: Graph comparing the pebble shape and the distance from the sea in Aldeburgh and Thorpeness.

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Standard Deviation For Pebble Shape Aldeburgh

Poles Group 1 Group 2 Group 3 1-2 0.917387595 1.221310771 0.840000000 2-3 1.120892502 0.896437393 1.312097557 3-4 1.177964346 1.107068200 1.316966210 4-5 0.828492607 0.908625335 1.299384470 5-6 0.780768852 1.222456543 1.297536127 6-7 0.899110672 1.135781669 1.171153278 Figure 63

Thorpeness

Poles Group 1 Group 2 Group 3 1-2 0.890168523 0.945727233 1.166190379 2-3 0.977547953 1.099818167 1.314686274 3-4 0.947417543 0.732393337 1.470238076 4-5 1.132960723 0.965194281 1.323782459 5-6 0.975909832 0.885663593 1.175755077 6-7 0.925418824 1.170469991 7-8 0.989747443 0.983056458 8-9 1.036146708 Figure 64

Analysis Looking at the graphs that show how the mean pebble shape varies with the distance from the sea (Figure 53-62), positive correlations can be found, just as expected. Every graph except Figure 59 showed that the pebbles further away from the sea are more rounded. The negative correlation in Figure 59 could be an anomaly, because when the results from all three groups for this location were plotted together, there was still a positive correlation.

However, the above standard deviations (Figure 63-64) all vary between ~0.73 and ~1.47. Again, there were many locations where the standard deviation was close to or greater than one. This suggests that the pebbles there were not very similar in shape and that the results received from this data is unreliable and that no conclusion can be drawn.

We also predicted that pebbles in Aldeburgh should be more “well-rounded” as they are subject to more attrition. However, Figure 61 shows that the pebbles in Thorpeness were rounder in shape since the blue line (Thorpeness) is constantly above the red line (Aldeburgh) and therefore suggests that in fact the pebbles in Thorpeness had a rounder shape.


% 55%

Conclusion Concluding, it can be said that even though there was a positive correlation between the pebble shape and the distance from the sea, the pebble size and the distance from the sea and the beach gradient and the pebble size that would prove the hypothesis, those were proven to be insignificant. Also, it can be seen in Figure 29 that our prediction that the pebbles are bigger in Thorpeness compared to Aldeburgh was wrong.

Most of the time, especially when comparing the beach gradient to the mean pebble size, the problem was that the data points were quite far off the mean. This can be linked back to the calculated standard deviations that came out to be quite big. A big standard deviation means that the considered data (pebble size / pebble shape) had a big spread and therefore no conclusive results can be drawn from them.

Overall, it has to be said that our hypothesis has to be rejected, even though there was evidence that it could be valid. However, the overall correlation was too insignificant.


% 56%

Evaluation As it could be seen, there was a correlation in all three cases. However, those were not significant, which means that we have to think about how the data sampling process could be improved in order to reduce errors.

Firstly, the number of pebbles between each pair of poles that were collected should further be increased. It is a good idea not just to collect pebbles in the middle of the poles, but maybe after each forth of the distance between them. This would then have the advantage that when considering Spearman’s rank correlation coefficient, more data pairs would be available, which gives a bigger “degree of freedom”. As the 95% significance level is not a linear relationship between the correlation coefficient and the degrees of freedom, this would mean that at a higher sampling rate, a lower correlation coefficient would be sufficient in order for the correlation to be significant at the 95% confidence level.

Another problem can be found when looking at the sampling technique that was used. When picking a pebble each 5 cm, human error is likely to be reasonably big. We will always pick the bigger pebbles and are reluctant to pick smaller ones. This problem could be avoided by “cluster sampling” the pebbles. We should just grab as many pebbles as possible and then measure all of them and assign them a shape factor. This will lead to a different number of pebbles collected for each location but it will definitely reduce human errors and give a more accurate picture of the pebble size and shape leading to a more significant correlation provided that the hypothesis is correct. Furthermore, one should think about whether it was a good idea just to measure the longest axis of the pebbles. Maybe, it would have been better to weight them so that not just one dimension is considered in the analysis.

It was also very hard to assess the shape of a pebble just by looking at Figure 6, especially because the “roundness factors” varied between 1 and 6. Introducing more categories, at least 10 might reduce the standard deviation (spread of the data) because there are more categories that a pebble could potentially belong to. Reducing human errors within this procedure might improve the overall significance of the correlation.

To find a significant change in pebble size, maybe the two beaches that are investigated should be at a greater distance from each other. It is quite unlikely that there is a significant change in pebble size when the two beaches are only about 5 kilometres apart.


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Bibliography Nagel, Garrett; Cooke, Briony “Geography Course Companion”, Oxford 2011 Nagel, Garrett; Cooke, Briony “Geography For The IB Diploma”, Oxford 2009 Longshore Drift (http://geographyfieldwork.com/LongshoreDrift.htm), accessed September 16, 2011 14:45 GMT Virtual Fieldwork (http://www.georesources.co.uk/leld.htm), accessed September 16, 2011 10:23 GMT Longshore Drift (https://www.youtube.com/watch?v=U9EhVa4MmEs), accessed September 16, 2011 18:38 GMT

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