Coasts
Introduction a range of techniques that you can use for fieldwork in coastal environments. These
techniques can be used in the traditional way to study and analyse coastal processes and landforms.
Alternatively, why not update your fieldwork slightly to investigate one of the topical and relevant
issues in the list below, using the same set of techniques.
Coastal investigations - Why not try...?
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Investigating the value which people place on a local beach
Investigating a litter problem or another issue: why does it happen there, who is most
responsible and what is their perception of the beach environment, how might the issue be
resolved or minimised
Investigating coastal management strategies, for example groynes as habitats. What lives on
or around them? How might their removal affect the ecosystem
Investigating water quality at the local beach - does it deserve its blue flag? Should it have
one
Undertaking a cost-benefit analysis of coastal protection measures at a particular location
A ‘what would happen if...?' study. For example, what would happen if all coastal protection
measures were removed
Considering the possible implications of climate change and sea level rise. What impact will
projected forecasts of more extreme weather events and rising sea level have on existing
coastal management schemes
Technique one: Beach profiles
Aims
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To survey the shape (morphology) of a beach
To compare beaches or coastlines in different locations
To examine the effects of management on beach processes and morphology
To investigate seasonal changes in the beach profile
To examine relationships between the beach profile and other factors, for example rock type,
cliff profile, sediment size or shape
Equipment
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Tape measure
Ranging poles
Clinometer or pantometer
Compass
Recording sheet
Methodology
1.
2.
Select sampling points for beach profiles across the width of the beach
3.
Note the main changes in slope angle up the beach, and use them to inform the ‘sections' for
the profile. (A through to H on the diagram)
For each change in slope, use the clinometer to take a bearing to record the slope angle (ii).
For example, from point A to point B in the diagram below. It is important to ensure that the
4.
At each sample point in turn, place a ranging pole at the start and finish (at A and H on the
diagram). Point A should ideally be the low tide mark, or as close to this as is safe
bearing is taken from a point on the ranging pole that coincides with the eye level of the
person using the clinometer. Many ranging poles have stripes which can be used for this
purpose. Alternatively, bearings can be taken from the eye level of a person of a similar
height holding the ranging pole
5.
Measure the distance along the ground of the section (i), and record this information
alongside the slope angle
6.
Repeat processes four and five for each break in slope that you have identified
Figure one: Surveying the morphology of the beach using a clinometer and ranging poles. Data
collected using this technique can be used to create beach profiles.
Pantometers can be used by one person, and the slope can be surveyed systematically at regular,
short intervals.
Figure two: Using a clinometer to measure the angle of a beach profile.
Considerations and possible limitations
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Varying tidal conditions can affect access and safety. Make sure you check tide times before
you embark on your fieldwork
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Low tide is the best time to measure beach profiles, but places a time constraint on the
activity. This can be overcome if groups of students complete profiles at different locations
simultaneously and share their results
It is important to ensure that the ranging poles are held straight and prevented from sinking
into sand, both of which may affect angle readings
Sampling technique is an important consideration. A balance needs to be struck between time
available and the need for a number of profiles across the width of the beach to ensure the
validity of results
There may be some user error when taking readings with a clinometer, and the sophistication
of models of clinometer can vary enormously
If using a pantometer, this piece of equipment must be kept vertical when taking readings
Using the data within an investigation
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Data can be used to draw profiles onto graph paper using distance from sea as the horizontal
axis and using an angle measurer to complete the profiles. The graphs can then be analysed
and comparisons made across the width of the beach
Profiles can be measured at different locations on the same stretch of coastline or in different
seasons and compared
Different stretches of coastline which may have different natural characteristics, for
example sand and shingle, or human characteristic, for example managed and unmanaged
can also be compared
Beach profiles can be used in conjunction with other data collected to examine relationships
between different variables
Technique two: Sediment analysis
Aims
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To examine the sorting of beach material, either across the beach profile (following the
sample lines used for profiling) or across the width of the beach (linking to the process of
longshore drift)
To investigate the effect of management structures, for example groynes, on the sorting of
beach material
To investigate the origin of beach material through the study of sediment cells
To compare sediment analysis at beaches in a range of locations and attempt to explain
similarities and differences
To examine the relationship between beach sediment and other factors, for example the size
and slope of the beach
Equipment
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Clear ruler, pebble meter or stone-board
Roundness or angularity charts/indexes
Recording sheet
Quadrats (optional)
Random number table (optional)
Methodology
Techniques for measuring are the same as for sediment analysis in river studies. Please refer to this
section for more information.
However, thought should be given to the sampling technique used to ensure that a representative
sample is obtained.
Quadrats can be used to select sediment for sampling. Alternatively, ten surface pebbles touching
your foot can be selected at each location. There are many different methods of sampling sediment.
The different methods should be analysed by the researcher and an informed decision made as to
which is the most appropriate for the aims of the investigation.
Considerations and possible limitations
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Deciding on the sampling strategy is very important in reducing subjectivity and increasing the
validity of results. A sampling method should always be adopted to avoid the temptation to
select the pebbles
Sample size should be large enough to provide a representative sample of the ‘parent
population', yet not too large to be unmanageable
The sharpest point of a stone must be measured when using the Cailleux scale and
judgement of this may vary from person to person creating subjectivity
In reality, using Power's scale will reveal mostly class five/six
Anything which may affect the results should be noted, for example recent storms or
management structures which may alter the composition of beach material
Coasts - Topics
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Changes in vegetation (cover and variety) moving inland
Changes in beach profile and sand dune profile
Speed of longshore drift
Changes in land use
Changes in defences (compare to land use)
Changes in beach or dune material (size or shape
Before starting your coursework, you should also think about how you can carry out the coursework
safely and definitely carry out a risk assessment. You can make your coursework safer by doing the
following:
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Protection from the weather (waterproof jacket, umbrella, hat, suncream)
Sensible dress (remember you will be representing your school, but you should also wear clothes that
don't draw attention to yourself
Always carry out coursework in groups
Always tell an adult or teacher where you area carrying out coursework
Always carry a mobile phone with you
Never do coursework near a river or the sea without an adult or teacher and without them checking
that it is safe
Carry out coursework in day light and wear reflective clothes
Check that your study area is safe. For example it wouldn't be safe walking around downtown San
Salvador
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Don't display valuables making you more vulnerable to crime e.g. if you have a camera or a phone
keep it out of sight
Introduction
Specification: Formulating aims and hypotheses: Candidates should be familiar with hypotheses
as statements that form the basis of Coursework assignments. The hypotheses may investigate a
geographical concept e.g. ‘A CBD has the highest concentration of comparison shops’. Collecting
relevant data, analysis and drawing conclusions using the data as evidence can test these.
Hypothesis: A hypothesis is a prediction or statement that you make before your data collection. A
hypothesis is normally based on theory. During your investigation you attempt to prove or disprove
your hypothesis. A piece of coursework may have more than one hypothesis and it does not matter if
you prove or disprove it.
A hypothesis should always be SMART. If your hypotheses are not SMART then it can be impossible
to prove or disprove them.
S = Specific
M = Measurable
A = Achievable
R = Realistic
T = Time-related
SMART hypotheses may include:
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The width of a river will increase as you move from the source to the mouth
The amount of vegetation will increase as you move inland from the sea (distance = 200metres)
The hottest part of the day will be between 1200 and 1400.
Data Collection
Whenever you are doing data collection, the aim is to be as objective as possible. Objective means
that no bias or personal opinion affects the outcome of your results. The opposite to be objective is
being subjective. Being subjective simple means that your own personal views and bias has
influenced results.
Objective: This is when data collection is not influenced by people's personal opinion. This is very
hard to achieve because even the design of data collection forms are influenced by people's opinion.
However, it is possible to try be as objective as possible by following a sampling technique, collecting
data in groups and following the methodology closely.
Subjective: This is when your personal opinion has an influence on the outcome of the data
collection. Everyone has personal bias, so this is not necessarily bad, but you should recognise this in
your methodology and evaluation.
Primary data: Any data that is personally collected by you (this does not mean collecting off the
internet). Primary data may include traffic counts, pedestrian counts, environmental indexes,
questionnaires or land use surveys.
Secondary data: Any data that has been collected by someone else. Secondary data collection
maybe found in books, on the internet, in academic journals, etc. Probably the most useful secondary
data is census data.
Primary data
Advantages
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It is up to date (current)
 You can study temporal changes e.g. how
You know how the data has been population has changed over a number of years
collected i.e. what technique  It can be quicker, especially if the data is on the
It only includes data that is
internet
relevant to your coursework
 You can study a larger area
It only covers your study area  It may include data that you can not obtain
It is collected in the format that you personally e.g. salaries
want
Disadvantages
 The data may include some
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Secondary data
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It is out of date, especially if it has been printed
personal bias
in a book.
Data collection can be time
 There might more information than you need
consuming
 The information may include a larger area than
It can be expensive to travel to
your study area
places to collect data
 You may not know how the data was collected
It is hard to study temporal
and who collected the data
changes
 The data might be in the wrong format e.g. in a
Some data might be unavailable or graph and not raw figures
too dangerous to collect
Only possible to cover a small
area
Quantitative data: This is any data that involves figures. Quantitative data is very easy to present
and analyse. Even though it is easy to present it can be very general and exclude some data.
Qualitative data: This is is more written data or even photographs or pictures. It tends to me
individual and personal, but it can be very hard to present and analyse. Qualitative data often comes
about as the results of interviews with open-ended questions.
Pilot Survey: This is basically a test that you carry out before your data collection. It is very important
that you test your data collection forms to ensure that you ask all the right questions and your
collection forms contain all the right categories. It is too expensive and too time consuming to going
and collect data a second time, if you missed it the first time.
Sampling: As a Geography student you will only have a limited amount of time and money to carry
out your coursework. Therefore it will probably be necessary to only investigate a sample. A sample is
simply a section or part of the entire study area or study population. The two main types of sampling
are; systematic and random.
Photographs are an increasingly common form of data presentation. Using photos is now a lot easier
in the digital era when you can crop, manipulate and annotate photographs. However, a common
mistake is still to include photos that aren't relevant to answer your hypothesis. Many people include
photographs that aren't even referred to in their text and are not properly labelled.
Advantages of Photographs
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Disadvantages of Photographs
They are more accurate than field
 People often include photos that are not relevant e.g. a
sketches
photo of their friends
They can be good for showing data  People forget to label, annotate or refer to photos, which
collection techniques e.g. measuring a
then makes them irrelevant.
river's load
 People often only photograph the nice things e.g. pretty
They can support data collection findings view and forget the more ugly areas that are just as
e.g. they can show an example of a poor important e.g. area of pollution
environment
 They can often contains too much information e.g. people
They can show temporal changes,
and vehicles
especially if you can find historical photos.
 Because they are two dimensional, depth can be
You can annotate and label them.
deceptive
Methodology
In a real piece of coursework, you would explain how all your data was collected. In your description
you would probably contain the following information:
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Date, time and location of data collection
Group size
Description and copy of data collection forms used e.g. questionnaires or counts
Explanation of how the forms were used e.g. sample size, count period, count technique, etc.
Description of equipment and an explanation of its use.
Data Presentation
Specification: Data presentation techniques: A knowledge of the illustrative techniques to present
data across the topics for Paper 4 is required. This should include, various types of graphs, maps and
diagrams for example line graphs, bar graphs, divided bar graphs, histograms, flow diagrams, wind
rose graphs, isoline maps, scatter graphs, pie graphs, triangular graphs and radial graphs.
You will probably be asked to complete a graph, diagram or table in the coursework examination.
Therefore you should remember the same equipment as paper 2:
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Pencil
Ruler
Eraser
Sharpener
Protractor
Compass
Calculator
Data Analysis
Specification: Analysis: Candidates should be able to describe the patterns in data presented in
graphs and tables of results. Reference to relevant geographical knowledge and understanding is
often required in the interpretation of the data. Practice of this skill will improve success in Paper 4
questions.
You maybe asked to do some basic data analysis of graphs, tables, maps, photographs or sketches.
When doing data analysis remember the following:
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Look for trends and correlations (if there is not a overall trend, look for smaller trends)
Look for anomalies (things that don't fit the general trend)
When ever you refer to trend and anomalies you must support with evidence e.g. facts and figures
from graph or table.
Try and explain trends (refer back to theory or other information that you have discovered in your
investigation)
Try and explain anomalies
Conclusion and Evaluation
Specification: Formation of conclusions: Using the evidence from the data, candidates should be
able to make judgements on the validity of the original hypothesis or aims of the assignment.
Reference is also required of the reliability of the collected data and a critical evaluation of the chosen
data collection methods.
Conclusion: This is basically a summary of your investigation. If you are asked to write a conclusion
remember the following:
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Refer back to original hypothesis
Use some data to support your findings
Refer to theory (if mentioned in introduction) - do your findings agree or disagree with theory
State what you have learnt from your investigation
Evaluation: In an evaluation you state what went well in your research, but also how it can be
improved or extended in the future. If you are asked to write an evaluation, think about the following:
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What went well (keep this brief)
Any problems with data collection e.g. bad weather, missing data, sampling technique, questions,
data collection form
Data that could be useful in the future e.g. secondary data from government, more questionnaires
(bigger sample)
Additional hypothesis that you could have used
Problems with time or money that could be changed in the future
Stage 1: Before you start
Coastlines can be broadly categorised into two different types.
Low energy coasts
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stretches of the coastline where waves are not powerful
often the rate of deposition exceeds the rate of erosion
landforms include beaches and spits
High energy coasts
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stretches of the coastline where waves are powerful for a
significant part of the year
often the rate of erosion exceeds the rate of deposition
landforms include headlands, cliffs and wave-cut platforms
Waves
Waves are created by the action of wind blowing over the surface of the sea.
Wave energy depends on
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wind strength
wind duration (how long the wind is blowing)
water depth
the fetch of the wave (the maximum distance of open sea a wave can
travel before it hits land)
The highest part of a wave is the crest and the lowest point is the trough.
The difference between crest and trough is the wave height. The distance
between one crest and the next is the wavelength.
When a wave breaks, water washes forward onto the shore. This part of the
wave is called the swash. The swash transfers energy up the beach. The
backwash is the opposite action that returns water and energy down the
beach.
Constructive waves and destructive waves
There are two types of wave: constructive waves and destructive waves.
Constructive waves have limited energy. They have a strong swash that
transports material up the beach increasing the amount of beach material
and creating a shallow, longer beach. Constructive waves appear lower in
height and are less frequent (about 6-8 waves per minute).
Destructive waves have much more energy. They have a strong backwash
that transports material back down the beach reducing the amount of beach
material and creating a steeper, shorter beach. Destructive waves appear to
be higher and more frequent (about 12-14 waves per minute).
Wave refraction
The direction in which a wave moves may be altered by the shape of the
coastline. Waves travel faster in deeper water. If a wave approaches the
coast at an angle the side nearer the coast, in shallower water, loses more
energy to friction so slows down. This causes the wave to refract (change
direction).
The direction of the waves is affected by features such as coastal defences,
bays and headlands. Refraction around a headland can result in erosional
formations on each side of the headland.
Wave transport
Waves transport material in the same ways as rivers transport material e.g.
traction, saltation, suspension and solution. The energy of the waves
dictates the type of material carried. The load is the total amount of
material carried by a wave. The competence of a wave is the maximum size
of particle that the wave can transport. Waves need more energy to carry
larger particles so only the waves with the highest energy can transport
rocks and boulders. The weakest waves can only transport sand and clay.
Longshore drift
Longshore drift is the movement of material parallel to the coast.
Longshore drift occurs when waves approach a beach at an angle due to the
direction of the wind. The swash, produced by breaking waves, moves
material diagonally up the beach at the same angle as the wave. In contrast,
the backwash moves material down the beach perpendicular to the
shoreline. This results in a zig zag movement of material along the coast.
Coastal deposition
Where does the material transported by waves come from? There are
several sources of sediment at the coast:
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sediment deposited by the waves
sediment produced by mass movement
sediment deposited by rivers entering the sea
sediment deposited by human activity
Sediment deposited by the waves has been eroded and transported from
elsewhere. Deposition occurs when the waves lose energy and can no longer
transport such a large load. As wave energy falls, wave competence falls and
the largest particles are deposited first. Wave deposits are rounded by
attrition and sorted by particle size
Coastal erosion
The processes of erosion, transport and deposition at the coast are similar
to the processes in fluvial environments. There are four types of coastal
erosion.
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Hydraulic action - air present in joints is trapped and compressed by
the pressure of incoming sea-water. Over a period of time, this
increase in pressure weakens and breaks off the rock. The rate of
hydraulic action is high on coasts where waves are powerful and the
coastline is made up of a densely jointed rock.
Abrasion (corrasion) - sand, shingle and boulders, carried by the sea,
rub against the surface of cliffs and wear it down. It is the fastest form
of coastal erosion.
Attrition - the movement of waves makes rocks and pebbles crash
together, so that sharp edges are broken down, and particles become
smaller and more rounded. It affects boulders and stones that have
already been eroded from the coast.
Solution (corrosion) - rocks are dissolved by acids in seawater.
Factors affecting the rate of coastal erosion
The rate of erosion is affected by the force of the waves (erosivity) and the
resistance of the coast to erosion (erodibility).
What determines the force of the waves?
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Breaking point of the wave - when a wave breaks it releases a great
deal of energy. A wave which breaks at the foot of a cliff releases the
most energy and causes fastest erosion, particularly corrasion. A
wave which breaks offshore will have lost most of its energy as it
travels up a beach.
Type of wave - steep destructive waves have more energy, and power
to erode, than shallow constructive waves.
Fetch of the wave - waves tend to become higher and more erosive as
their fetch increases.
Shape of coastline - refraction makes waves stronger and more
erosive on headlands rather than bays.
Gradient of the seabed - the steeper the gradient of seabed, the more
likely it is that the wave will break closer to the shore. Less of the
wave's energy is used in overcoming friction with the seabed, so there
is more energy to erode.
What determines the resistance of the coast to erosion?
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Mechanical strength of rocks - some rocks (e.g. granite) are stronger
and more resistant to erosion than others (e.g. unconsolidated
sediments such as glacial till). Rocks which can become saturated
with water can collapse (e.g. clay).
Jointing - densely jointed or faulted rocks are susceptible to hydraulic
action. Faults, joints, cracks and bedding planes can all act as points
of weakness.
Chemical composition of rock - some rocks are soluble in water (e.g.
chalk is soluble in acidified water) and can be eroded by corrosion.
Vegetation - the foliage and roots of vegetation bind soil and rocks
together and reduce the rate of erosion.
Human protection - in many locations, physical structures (e.g. sea
walls) have been installed to absorb the energy of waves and so
reduce the rate of erosion.
Sub-aerial processes
Sub-aerial processes are those processes which operate at the coast but do
not involve direct contact with the sea. Material is loosened and made more
vulnerable by sub-aerial weathering and mass movement.
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Salt weathering - sea spray enters cracks. Later the water evaporates
to leave crystals of salt. Further evaporation enlarges the crystals. The
growing crystal exerts force on the rock. The rate of salt weathering is
most rapid in well-jointed rocks.
Freeze-thaw weathering - rainwater or seawater enters cracks. Later
the water freezes to ice and expands. This exerts extra pressure on the
rocks and makes cracks become larger. Thawing of the ice allows the
water to trickle into the new cracks. The rate of freeze-thaw
weathering is most rapid in well-jointed rocks. It is slower than
inland because seawater freezes at a lower temperature than
freshwater. Furthermore, frost is less likely at the coast than inland.
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Wetting and drying - water enters sediments and causes expansion.
The sediment contracts when it dries out. Repeated wetting and
drying causes stress fractures in some rocks, such as clay and shale.
Biological weathering - boring organisms (e.g. limpets) can drill into
the rock and create small depressions. Seaweed attaches itself to
rocks and the action of the waves can be enough to cause the swaying
seaweed to prise away loose material from the sea bed.
Other processes of weathering - hydration, hydrolysis and
carbonation may also occur at the coast.
Mass movement - is particularly active at the coast because undercutting of
rocks by the sea makes them unstable. There are two basic types.
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Rockfalls occur when the waves undercut the cliffs and weathering
loosens pieces of rocks on the cliff face. Rockfalls are most common
on cliffed coastlines with resistant rocks such as chalk or limestone
Landslips occur when rocks become saturated with water. The slip is
triggered either by the waves undercutting the rocks or following
heavy rain. The saturated material flows out from the base of the cliff
to form a tongue of mud.
Questions to investigate
A field investigation of a beach can involve a number of working
hypotheses, such as
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Quantity of beach material will increase in the direction of longshore
drift
Pebbles will become smaller in the direction of longshore drift
Pebbles will become rounder in the direction of longshore drift
Wave type will be different between two beaches/two areas
Stage 2: Fieldwork
When and where to carry out your fieldwork
Fieldwork on the beach may take you several hours to complete. To ensure
that you have enough time, try to carry out fieldwork on a falling tide,
ideally starting 1-2 hours before low tide. A larger amount of beach is
exposed on a low spring tide than a low neap tide. Use this page check
tides for your closest area.
Investigating longshore drift
For investigations looking at longshore drift along the shoreline, you may
choose to establish a systematic sample, using equally spaced intervals
along your beach. Quantitative evidence for longshore drift can be collected
in three main ways.
1. Beach profiles
Beach profiles use a combination of distance and angle measurements to
investigate the shape of the beach. They also allow for calculation of crosssectional area as a measure of the amount of beach material present at a
location.
If you intend to statistically analyse this data, a robust test will require at
least 10 sites.
At each location, students will follow a straight transect line from the edge
of the sea to the end of the active beach (this may be marked by a defence or
the presence of vegetation etc.). The transect is split into smaller
measureable segments. Taking measurements at equal intervals up the
beach is more straightforward, but it tends to hide the small variations in
slope which can be important in showing beach shape. Instead, you may
wish to divide your transect according to where you estiamte the slope
angle changes (from break of slope to break of slope). This means that you
normally end up taking more slope readings, but the profile that you draw
is more accurate. A step-by-step method for beach profiling is as follows:
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Person A stands at a safe distance from the edge of the sea holding a
ranging pole
Person B stands holding a second ranging pole further up the beach
where there is a break of slope
The distance between the two ranging poles is measured using a tape
measure
The angle between matching markers on each ranging pole is
measured using a clinometer
Repeat this process at each break of slope until the top of the beach is
reached
Beach profiles can also be used to investigate the effects of coastal
management.
2. Pebble measurements
Pebbles can be selected using a variety of sampling strategies and methods.
If you are looking for a difference between the two ends of your beach, you
should use stratified sampling, and collect a sample of at least 10 pebbles
from either end.
If you are looking for a correlation between distance along the beach and a
pebble characteristic, pebbles should be sampled at systematic intervals
along the beach. If you wish to carry out robust statistical analysis of this
data, you you should establish at least 10 sample sites.
At each sampling location, pebbles can be selected in a variety of ways e.g.
using a 10m tape measure laid out parallel to the water, and using a
random number chart to choose points along this tape to collect pebbles
from. Students should be aware that sediment size is likely to change with
distance up the beach and take this into account, either by selecting pebbles
from an equal distance up the beach at each location, or by collecting a
sample which represents all distances up the beach.
Once pebbles have been collected, several measurements can be taken:
(a) Pebble size
Pebble size measurements allow you to investigate whether pebbles appear
to have been moved along your coast, experiencing erosion, and therefore
becoming smaller, as they travel.
Pebble size can be measured using a 30cm ruler or using calipers for
greater accuracy. A single axis of each pebble can be measured e.g. the
longest or 'a' axis (see diagram) or students may chose to measure multiple
axes and calculate an average.
Alternatively a set of graduated sieves can be used to sort sediment samples
into different size categories (in millimetres or as phi sizes). The sieves are
arranged in decreasing mesh diameter with the largest at the top. The
sediment sample is placed in the top sieve then the sieves are shaken to sort
the sediment into the various sieves. The mass of sediment in each sieve is
measured using scales and the percentage of the total sample can be
calculated.
(b) Pebble shape/roundness
The simplest way to record pebble shape is to classify the stone as very
angular, angular, sub-angular, sub-rounded, rounded or very rounded
using a Power's Scale of Roundness.
very
angular
angular
subangular
subrounded
rounded
very
rounded
Alternatively, for more precise shape data, Cailleux's Flatness Index can be
used to obtain a numerical and reasonably objective value for roundness.
The raw data needed for each pebble is as follows.
1. The length of the longest axis (called l)
2. The radius of the sharpest angle (called r). The radius can be
measured using the Cailleux Roundness Chart with
accompanying instrutions. To calculate the Cailluex's Index from this
data, see Stage 4.
The a, b and c axes can also be used to calculate Krumbein's Index of
Sphericity and for Zingg's shape classes (see Stage 4). Zingg's shape
classes can also be visually estimated, by seperating pebbles into the
following categories by eye:
Type of
pebble
Characteristics
Example
Sphere
a, b and c axes roughly equal
Ball
Disc
a and b axes roughly equal, c axis much shorter
CD
Rod
relatively long a axis, with b and c axes shorter and
roughly equal
Tube
Blade
relatively long a axis, with a shorter b axis and much
shorter c axis
Knife
3. Other data
A variety of other data can be collected to investigate longshore drift.
Students can create field sketches and/or annotated photos to show
evidence of longshore drift e.g. showing changes in the beach on either side
of a groyne.
The float method can also be used to investigate longshore drift. A
biodegradable float such as an apple or orange is placed in the sea and the
time taken for it to travel over a set distance (e.g. 10m) is timed.
Investigating wave type
Wave analysis can also be carried out to allow students to comment on the
presence of destructive or constructive waves and to compare areas and/or
beaches. Differences in wave type may be be used to infer which coastal
processes are occuring.
The simplest indicator of wave type is wave frequency. This can be
measured by timing the number of waves breaking on the shore in 1
minute. A low wave frequency (e.g. 6-8 waves per minute) usually indicates
constructive waves, whereas a higher wave frequency (e.g. 12-14 waves per
minute) usually indicates destructive waves. By itself this method does not
produce particularly reliable data, but it can be improved by also
considering other wave characteristics such as wave height and orbit shape,
either in text or photo form.
Stage 3: Finding more data
Wave and wind data can be found at Magic Seaweed, National Data
Buoy Centre or the Channel Coastal Observatory.
The British Geological Survey Map Viewer can be used to obtain
infomation on the bedrock and drift geology of most areas.
Shoreline Management Plans for your section of coastline can be used
to find information about erosion and other coastal processes.
Projections of coastal flooding as a result of sea level rise can be modelled
using Flooding Firetree.
DEFRA have released a series of reports of sand dune processes and
management in England and Wales. Part 3 p.228 to 232 give wind
rose data for 11 weather stations around the coast of England and Wales.
You can also download PDFs of Field Studies Journal papers.
Stage 4: Data analysis
Data Presentation
Beach profile
A beach profile is a cross section of the beach from the top of the beach to
the seashore. It shows distance on the x-axis and height above the seashore
on the y-axis.
The distance and angle information for each facet of the beach can be
plotted by hand or using a spreadsheet program to create a beach profile.
See image below for an example of this. Alternatively, complete beach
profiles can be presented around a map.
The profile graph can be used to calculate total cross-sectional area.
Proportional bars representing total cross-sectional area can also be
displayed on a map for example using Google Earth graphs (see below).
Pebble measurement
(a) Pebble size
If you have measured pebble size using calipers or a ruler, you could
calculate the mean pebble size for each sample site on the beach. The data
can be presented in a graph, such as a bar chart. More complex data
presentation includes the use of Google Earth graph or the construction of
box and whisker plots (showing median pebble size and the spread of
values around the median).
If you have sieved the sediment, you can calculate phi sizes. Use the
conversion table if you do not have the phi sizes already.
Sediment
size
mm
phi
1.00
0
0.50
1
0.25
2
0.13
3
0.06
4
0.03
5
0.01
6
Calculate the percentage mass of sediment in each phi size category. For
example, if total mass=100g and the mass of material at 5-10mm = 20g,
then 20% of the total mass of sediment is 5-10mm in diameter. This can be
presented in a number of ways



using a histogram with % mass on the y axis and sediment size on the
x-axis
pie charts to show changes along the transect, which might be
overlaid on a map or aerial photograph
plot a scattergraph to show how mean sediment size varies with
distance along the beach (see below).
Alternatively, use semi-logarithmic graph paper to plot a cumulative
frequency graph of phi against mass. Plot phi size on the linear x-axis. Plot
the cumulative mass of sediment on the logarithmic y-axis.
On your finished graph, find the phi size values at 16% and 84% cumulative
mass. Use these figures in the following formula
(phi at 84% mass - phi at 16% mass) ÷ 2
Use the following table to interpret the result
result
<0.35
interpretation
very well sorted
0.35 - 0.5 well sorted
0.5 - 0.7 moderately well sorted
0.7 - 1.0
moderately sorted
1.0 - 2.0 poorly sorted
2.0 - 4.0 very poorly sorted
> 4.0
extremely poorly sorted
(b) Pebble shape / roundness
Calculating the Cailleux Index
The raw data needed for each pebble are:


the length of the longest axis (l)
the radius of curvature of the sharpest angle (r)
For each stone, calculate Cailleux Index as follows
Ci = (2r/l)x1000.
Ci=1000 for a perfectly spherical pebble. The lower Ci is, the more angular
the pebble.
Calculating Krumbein's Index of Sphericity
The raw data needed for each pebble are the lengths of the a, b and c axes.
For each stone, calculate Krumbein's Index as follows
K = cube root of bc/a2
K = 1 for a perfectly spherical pebble. K must be between 0 and 1. The lower
K is, the less spherical the pebble.
Zingg's shape classification
The raw data needed for each pebble are the lengths of the a, b and c axes.
Calculate the ratio b ÷ a
Calculate the ratio c ÷ b
Now classify each pebble into one of the four groups shown in the table
Type of pebble
b÷a
c÷b
Sphere
> 0.67
> 0.67
Disc
> 0.67
< 0.67
Rod
< 0.67
> 0.67
Blade
< 0.67
< 0.67
Presenting pebble shape/roundness
Categorical measures of shape (e.g. Zingg) can be presented using bar
charts or pie charts, which could be located on a map.
As a numerical index of roundness, Cailleux's Index may be presented using
techniques such as box and whisker plots.
Statistical Analysis
Coastal data can be analysed using a variety of statistical tests, depending
on how you have set up your investigation, for example


If you have collected data showing how a variable changes with
distance along the beach, you could use the Spearman's Rank test
If you have collected data showing the difference between two areas
of the beach, you could use the Mann Whitney U
Interpretation
Firstly describe the trends in each of your data sets referring to your
graphs and any statistical results generated. For example:


What trends are shown e.g. what is the relationship between distance
along the beach cross sectional area of the beach?
What is the strength of the trend (e.g. do you have a statistically
significant result at p=0.05?)
Explain the trends (e.g. why does cross sectional area increase with
distance along your beach?) referring to the processes which may have
caused them.
Are there any anomalous results? Can you explain them? Some
possibilities may include:
a) Cross sectional area is smaller/larger than expected in a location due to
the presence of a particular
coastal defence
b) Pebble size or shape shows an unexpected result in one area due to
input of new material via mass
movement
Link your data sets together. For example,
a) Try to link data sets collected along the beach to longshore drift or lack of
longshore drift
b) Try to link data sets collected up the beach (e.g. phi sediment size) to
wave energy and time of year i.e.
larger particles, found at the top of the beach, are deposited by the swash
of destructive waves in winter.
Stage 5: Review
Conclusion
Create a summary of your findings and answer your investigation
question/hypothesis. Secondary data can be used to support your findings
(e.g. If you have data on prevailing wind direction, you will be able to
discuss the differences between the angle of the swash and longshore drift)
Evaluation
In your evaluation section, discuss the reliability of your data collection
techniques. You should discuss the limitations or your study, and suggest
improvements and/or extensions. The type of questions that you should
address include:


How suitable was your sample site? Was it a good location to carry
out your investigation?
Was your sampling strategy appropriate? Did you have an
appropriate number of sample sites for robust
analysis?





How accurate are your results? Were there any limitations to your
method which reduced accuracy of data e.g.
how accurate is a clinometer?
How reliable are your results? For example, what are the limitations
of using subjective data such as Power's
Index?
How robust was your statistical test? Did you have enough data? Are
there any limitations inherent to the test?
How robust are your conclusions? You are likely to be limited by only
being able to sample at one time of year (perhaps only one day), so
you will not have data on seasonal variation in pebble roundness, size
and sorting, or beach profile. Your secondary data on wind strength
and direction may indeed indicate that there is seasonal variation in
wave strength and direction.
What other data would it have been useful to obtain?