Fieldwork Cranedale

• Whilst measuring the velocity at Hellworth
Beck the speed of the river was to slow to
move the impellor along the shaft of the
hydroprop. Therefore, we had to record the
velocity of the river as 0.08ms, which meant
that we could have over estimated the
velocity of the river.

Equipment for the Examinations
Black ink or black ball – point pen.
Use of pencil only for drawing.
Calculator
Protractor
Ruler
Rubber

Unit 2 – January 2009
Explain the geographical concept, process or theory that underpinned your fieldwork
enquiry. (4)
How did you respond to risks associated with undertaking your primary data
collection? (4)
Outline and justify one method of data collection that you used in your enquiry. (6)
With the aid of a sketch diagram, describe one technique that you used to present
data in your enquiry. (6)
Making specific reference to your results, suggest how your enquiry could be
improved. (5)

Unit 2 – Summer 2009
Describe the location of your fieldwork and outline why this was a suitable site for
your investigation. (4)
State one hypothesis or research question or issue for evaluation that you have
investigated in 2a. Describe one method of primary data collection used in the
investigation. (5)
Discuss the limitations of your chosen method in 2a. (6)
Outline and justify the use of one or more techniques used to analyse your results. (5)
Drawing upon your findings, explain how your enquiry improved your understanding
of the topic. (5

Sate the aim of your investigation and describe one method of data collection
associated with the aim. (6)
Discuss the strengths and weaknesses of the method of data collection desribed
above. (6)
Describe one method used to present your data. (5)
How far did your fieldwork conclusions match the geographical theory, concept or
idea on which your investigation was based? (5)

State the aim of the fieldwork investigation.
Describe the geographical theory, concept or idea that formed the basis of your
fieldwork investigation. (5)
With reference to your fieldwork, distinguish between qualitative and quantitative
data. (3)
Describe one method that you used for the collection of primary or secondary data.
(6)
Outline one technique that you used to present results from your data collection. (4)
Evaluate your investigation. In your answer, you should: a- comment on the strengths
and weaknesses of the different aspects of the study and b – suggest improvements.
(7)

Describe the purpose of your fieldwork enguiry. (5)
In the box provided below, draw an annotated sketch map of the location of your
study area to show its basic characteristics. (5)
Distinguish between primary and secondary sources of data used in your fieldwork. (3)
With reference to one technique you chose to present data in your enquiry, justify the
choice of this technique. (6)
Explain how your fieldwork enquiry could have been improved. (6)

Outline the purpose of your enquiry. (5)
Using specific examples from your fieldwork, describe the risk assessment you
undertook in relation to your enquiry. (6)
Evaluate one of your methods of data collection. (5)
Summarise the main findings of your fieldwork. (4)
How far did your findings reflect your expectations at the start of the enquiry? (5)

You have experienced geography fieldwork as part of the course. Use this experience
to answer the following questions.
State the aim of your fieldwork enquiry.
Describe the advantages of your chosen location for the fieldwork enquiry. (4)
Evaluate one method of primary data collection that you used in your enquiry.
(6)
Outline how you obtained and why you used secondary data in your enquiry.
(5)
Describe advantages of a technique that you used to analyse your data. (5)
With specific reference to your results, summarise the main conclusions of your
enquiry. (5)

You have experienced geography fieldwork as part of the course. Use this experience
to answer the following questions.
Describe the purpose of your fieldwork enquiry. (6)
Describe a sampling technique you used to collect data. (5)
Justify the use of one technique used to analyse data in your enquiry. (6)
Referring to your results, outline the main conclusions of your enquiry and
suggest further areas of research. (8)

Unit 4a – January 2010
State the aim(s) of your investigation.
Describe the location of your fieldwork investigation and explain its relevance to the
aim(s). (12)
Explain how one method of data collection that you used was suitable for the
investigation. (6)
As a result of your experience in the field. Justify one or more improvements that you
would make to a method of data collection that you used. (12)
Evaluate the usefulness of the conclusions reached in your investigation and consider
their potential implications. (10)

Unit 4a – Summer 2010
Explain the reasons why you selected this aim for investigation. (10)
Describe and justify the measures you took to minimise the health and safety risks
involved in your investigation. (8)
Describe one technique of data analysis you used and explain how far the data you
collected made this technique appropriate to your investigation. (10)
With reference to your aim(s), evaluate the success of your investigation. (12)

Select one method of primary data collection that you used in your investigation.
Explain the relevance of this method to the aim(s) of your investigation. (8)
Evaluate the effectiveness of this method in the light of your experience in the field.
(8)
Describe one technique of data analysis that you used and justify its inclusion in your
investigation. (12)
Assess how useful you found your investigation to your understanding of geography.
(12)

State the aim(s) of your fieldwork investigation.
Explain how the location of your fieldwork was relevant to the theory / concept / issue
being investigated. (8)
Describe and justify how you made sure that the data collected were as accurate and
reliable as possible. (12)
Select one method of data presentation used in your investigation. Explain, why you
used and evaluate its effectiveness in showing the data you collected. (12)
In the light of your results, suggest how your investigation could be further developed
and/or extended. (8)

All your answers must relate to the geographical fieldwork investigation that you
undertook in preparation for this examination.
Explain the importance of the choice of location for your investigation in relation to
your aim(s). (12)
Outline one method of primary data collection used in the field in your
investigation. (6)
Evaluate the suitability of this method of primary data collection. (10)
Explain how secondary data were used, or could have been used, to develop
your conclusions. (12)

All your answers must relate to the geography fieldwork investigation that you
undertook in preparation for this examination.
State the aim(s) of your fieldwork investigation
Explain the geographical reasons for carrying out your investigation in the area. (10)
Describe and justify the steps taken to minimise the risks involved in collecting data
for your investigation. (8)
Assess the usefulness of one method of data presentation that you used in
your investigation. (12)
Discuss how your investigation helped your understanding of geographical
theory. (10)

Aim
To investigate the extent that downstream mean channel
velocity for the upper Derwent river increases. Even though
the gradient of the river decreases downstream.
RQ1 – How does velocity change downstream .
RQ2 – What factors influence the change in velocity.

General Factors that Effect Velocity
Downstream Gradient of the river.
Hydraulic Radius.
Roughness of the wetted Perimeter.
Geology of the bedload.
Human interference on the river channel.

Theory
The factors that control the velocity of a river channel

Theory
As the hydraulic radius increases the ratio of water in contact with the wetted
perimeter of the river channel decreases. This means that the water loses
proportionately less energy in overcoming friction and the mean velocity of the river
channel increases.
The hydraulic radius increases as the cross sectional area of the river channel
increases. This is because as you move down the long profile of a river its catchment
area increases in size. This means that there is an increase in the amount of water
entering the river channel, either by more tributaries entering the main channel or by
surface flow, through flow or ground wtare flow.
The roughness of the wetted perimeter also decreases as the size of the stones
become smaller and smoother. This is because the river has had more time to erode
these stones, either by attrition or abrasion. The smoother and smaller stones of the
wetted perimeter again reduce the amount of friction the river channel has to
overcome. This increases the velocity of the river.

Location of the Drainage Basin
The River Derwent is situated in the North York Moors on it southern flank to the west
of Scarborough. It flows in a southern direction of the moors and joins the River Ouse.
The study area covers only a 12 km stretch of the upper course of the Derwent River
between its source a 200 meter high moorland plateau called Stoney Marl Moor to
where the river flows past Howden Moor farm at Broxa.
The drainage basin varies from high moorland plateaus in the north and north east, a
coniferous forested area in north east and an area of slopes devoted to grassland in
the south. These areas of highland are intersected by deep v-shaped valleys of the
River Derwent and its tributaries. The following three sampling sites were chosen to
investigate the aim.
Helwath Beck – 110m altitude - 3 km from source – drainage basin of 10 km2
Jugger Howe Beck – 100m altitude - 5 km from source – drainage basin 28 km2
River Derwent – 60m attitude – 12 km from source – drainage basin of 48 km2

Upper course of
River Derwent
Helwath Beck
Jugger Howe Beck
Broxa
Kirby Grindalythe
Source of Derwent
River continues
through Vale of
York to join the
R. Ouse before
flowing into the
Humber Estuary
Total length: 170km

Source area - North York Moors

Summary of the Characteristics of the Drainage
Basin
There is very little human interference of river the channel by human activity, such
as channelization or building of bridges.
The underlying geology for the whole of the drainage basin is sandstone.
The attitude of the river falls by over 50 meters within a 12 km stretch.
The size of the river’s drainage basin increases from 10 km2 to 45 km2 within a 12
km stretch.
The drainage basin of the river has high amounts of rainfall that ensure the river
flows throughout the year.
The rivers are small enough to allow sixth form students to collect primary data
safely.
All the sites can be visited in one day and we have the landlords permission to
access the sites.

Sites 1& 2
Helwath
Beck
&
Jugger
Howe
Beck
1
2

Site 3:
R. Derwent
downstream
to Broxa
3

The drainage basin within the study area of the River Derwent experiences high levels
of precipitation and within 12 km of its source it quickly increases in size from 10 km2
to 48 km2.
These factors ensured that the investigation could analyse how downstream changes
in the rivers mean velocity were influenced by significant changes in its hydraulic
radius and the roughness of its wetted perimeter.
The influence of human activity on river was minimal and sandstone formed the
underlying geology of the drainage basin. This reduced the influence that other
factors may have had on the velocity of the river and allowed the investigation to
concentrate on how the change in gradient, hydraulic radius and roughness of the
wetted perimeter influenced velocity.
Since all three sample sites were within 12 km of each other and prior permission for
access had been gained from their landlords it was possible to complete the fieldwork
within the one day allocated.
The relatively low velocities and the shallow nature of the river allowed the
investigation to be carried out safely.
This stretch of river has a large set of secondary data which can be compared to the
primary data collected to evaluate the success of the investigation.

Risk Assessment
(Hazards, Risks, Control Measures & Justification)

Risk Assessment
Hazards are the physical problems that cannot be removed e.g. steep and wet paths
leading to the upstream sites, deep water and high velocity river, uneven and
slippery stones in river channel, remote location of upper stream sites, heavy
rainfall, and cold temperatures.
A formal risk assessment was completed prior to the investigation. This assessment
listed the separate hazards and the potential risks associated with each hazard.
These risks were then assessed on a scale of low , medium or high to work out the
likelihood of these risks happening and the level of there impact.
Then appropriate control measures were put in place to minimise the risks involved in
carrying out the fieldwork.
Hazard = The physical problem that cannot be removed e.g. weather, slope, water
Risk = The likelihood of it happening and the extent of the consequence.
Then what you do to reduce the consequence.

Risk Assessment
Hazard = The physical problem that cannot be removed e.g. weather, slope, water
Risk = The likelihood of it happening and the extent of the consequence.
Then what you do to reduce the consequence.

As the path from the mini bus to the river ran down the side of a steep sided valley on
which we could easily have slipped we wore appropriate footwear, carried any extra
clothes, are packed lunch and any field equipment in our rucksacks. This allowed are
hands to be free to reduce the effect in the event that we slipped or tripped up.
To reduce the risk of catching hypothermia from any cold and/or wet weather on the
day of the fieldwork we wore clothing that was warm, layered and waterproof. In case
we encountered any unseasonably cold or wet weather each member of the group
carried a hat, a pair of gloves and an extra lay of clothing in their rucksack. The weather
forecast was also checked before we set of to make sure we were appropriately
prepared for the weather condition.
The site at Broxa was just downstream from a farm and in order to reduce the chances
of contracting Weils Disease we tape up any open cuts or grazes which may have been
exposed to the river and washed our hands before eating with anti bacterial hand wash.
Uneven and slippery rocks in a deep and / or fast flowing river – The likelihood of
injury or death from these hazards are probably low to medium. However, the impact
from an accident could be very serious ranging from a twisted or broken ankle, a person
been knocked unconscious or in an extreme case been drowned.

To reduce the risk we made sure that we only walked and did not run, wore
wellington boots and watched where we placed are feet when working in the river
channel, especially when carrying field equipment. Only parts of the river no deeper
than our calfs and where the current was slow enough for us too keep our balance
were used. We also worked in groups of three or more. If someone did injury
themselves or knocked themselves unconscious some of the group members could
have remove them from the river and remained to look after them. This left another
person free to inform the group leader of what had happened.
The remote location of the steep sided valley in which the two upstream sites were
located would have compounded the effect of the risks mentioned above. As it would
have made it very difficult and time consuming for any injured person that could be
moved to be taken to hospital for treatment.
For a very serious accident where the person could not be moved the group leader
would have had to walk and then drive to an area with mobile phone coverage to call
the emergency services. This delay along with the response time of the emergency
services could have put the persons life at risk or made treatment of their injuries
more difficult.

Methodology and Data Collection

Downstream Sites and Cross - Sections
The three sites were chosen using a stratified sampling method.
The cross section were sampled using a systematic point sampling method.

Choosing the 3 Sites
A stratified sampling technique was employed to ensure that the three sites from
which we collected our data were situated progressively downstream from the source
of the River Derwent.
An OS map was used to work out the stream order for each individual river within the
upper drainage basin of the River Derwent. Each individual river was categorised as
either 1st, 2nd, 3rd or 4th order.
One site was selected from a 2nd, 3rd and 4th order stream.
Random sampling could have led to the possibility that all the sites could have been
located in only 1 order of stream, which would not use useful in investigating how and
why the velocity changes downstream.
It was decided not to sample any 1st order streams. The distance and terrain to reach
these streams would have been too time consuming and dangerous for us to carry the
equipment needed. Also the hydo prop would not have functioned probably as the
streams would have been to shallow for the impellor to turn.

Stream Orders
All the initial, unbranched source tributaries are called first order streams. When two
first order streams merge they form a second order stream; When two second order
streams merge they form a third order stream; and so on. Notice that it needs two
stream segments of equal order to join to produce a segment of a higher order.

The sites
The following sites where selected because they represented each of the different
stream orders, they were safe to access by foot and we had permission from the
landlord cross their land.
2nd order stream - Helwath Beck – 110 ms- 3 km from source – DB of 10 km2
3rd order stream - Jugger Howe Beck – 100 ms- 5 km from source – DB of 28 km2
4th order stream - River Derwent – 60 meters – 12 km from source – DB of 48 km2
At each site a method of random sampling was used to identify where to obtain
measurements from the river. A tape was laid out to measure along the river bank for
a length of 5 meters, a random number was picked from a random numbers table, and
used to mark the position where the measurements for the cross – section would be
taken.
This method was designed to get rid of bias and avoid me choosing to measure the
easiest section of the river, which might not necessarily be representive of the river.

Data Collected at Each Site
Velocity = 3 point and mean velocity
Present width and present depth (cross sectional area)
Wetted Perimeter = chain
Bed Load Size = B axis
Gradient = m/m or angle

Velocity – Hydro Prop
The velocity of the river was measured at ¼, ½ and ¾ of the rivers width. To work out
at what intervals to measure the velocity the width of the river was divided by 4.
The impeller of the hydro prop was set to ½ the depth of the river and then wound to
the end of its shaft and given a half turn backwards to ensure it did not get stuck. With
the impeller facing upstream it was placed in the water and timed using a stopwatch
to see how long it took to reach the end of its shaft.
The time recorded in seconds was then compared with a calibration table to work out
the actual velocity of the river in ms-1. The three separate point velocities were then
averaged to work out the mean velocity of the river.
This method was repeated at all three downstream sites.

Velocity – Strengths and Justifications
This method was used as the systematic sample gave data which was representative
of the entire channel at each site and so bias or subjectivity in our technique was
reduced.
The time data was converted into ms-1.. Therefore, the data collected could be directly
compared between the different sample sites. This gave a greater accuracy to our
results so our conclusions would be more reliable.
This technique was also quite easy and quick to use.
It gave relevant data to help investigate the main aim and answer research question 1
which was How does velocity change downstream.

Velocity – Limitations
The impellor had a high critical velocity of 0.08 ms-1 .This means at low velocities
the river did not have enough energy to turn the impellor. If the impellor had not
reached the end of the shaft after one minute the measurement was stopped.
All measurements of one minute and over were converted into a velocity of 0.08
ms-1. These results might not have been a true reflection of the rivers velocity. For
very low velocities this method could have over estimated the rivers true velocity.
However, for higher flows this method would have given results nearer to the river
true velocity.
At very low channel depths the hydo props impellor was either touching the river
bed or appearing above the surface of the water. These results might not have
been a true reflection of the rivers velocity. For very low depths this method could
have over estimated the rivers true velocity. However, for deeper depths this
method would have given results nearer to the river true velocity.

Velocity – Improvements
Measure the velocity at more points along the cross – section. By using a larger
number of points to measure the velocity you would reduce the percentage error.
If only three point velocities were measured and one was anomalous then there
would be a 33.3% error in the results. If the number of point velocities measured was
increased to 9 measurements the error would be reduced to only 11.3%, a more
acceptable level of error.
Therefore, the results for mean channel velocity would be more accurate and any
conclusions draw from these results would more likely to be reliable.
Use a electromagnetic open channel flow meter to measure the point velocities. This
would reduce any overestimates of measurements where the point velocity of the
channel was below 0.08 ms-1.and give more accurate results were sections of the
channel were too shallow for the hydro prop to work properly.

Present flow – Width and Depth - CSA
To work out the width of the river a peg was placed on either side of the river channel
where the dry banks meet the water. A line was run between these two pegs and in
order to avoid drag, the line was pulled tight at 900 above the flow of the river. The
length of the line was then measured using a 30 meter tape measure.
To work out at what intervals to measure the depth of the river the width was divided
by 10. At each of the 9 intervals a meter ruler was placed in the water with its thin
edge facing upstream to measure the depth.
To work out the cross - sectional area of the river the width was multiplied by the
average depth of the river.

Present flow – CSA – Strengths & Justifications
reduced.
This technique was easy to replicate at each of the three sites surveyed. Therefore,
the data collected could be directly compared. This gave a greater accuracy to our
results so our conclusions would be more reliable.
This data was collected as the width and depth of river are used to calculate the rivers
cross sectional area. The sum of all the depths recorded is calculated and divided by
number of samples taken to work out the average depth. This is then multiplied by the
width to work our the cross – sectional area of the river.
The cross – sectional area is one of components used to calculate the hydraulic radius.
The hydraulic radius for each site was then used to try explain any changes in velocity
found.

Present flow –CSA – Limitations &
Improvements
An accurate measurement of the depth might not have been recorded as the meter
ruler was not held vertically. Also the person recording the depth could have misread
the actual depth.
By only using 9 sample points the distance between each point will be greater in the
wider stretches of the river. This could increase the chance of missing any sudden
changes in depth. Therefore, this method could produce results that did not truly
reflect the actual depth of the river and the calculation of the average depth of the
channel could have been inaccurate, which in turn would have produced a miss
leading figure for the cross – sectional area of the channel. Our conclusions relating to
how hydraulic radius influences velocity might have been unreliable.
Complete 3 or 4 cross sections for each stream order surveyed. This should provide a
more representative sample of the depth of the river. This gives a greater accuracy to
our results so our conclusions could be more reliable.

Wetted Perimeter
To work out the wetted perimeter a metal chain is run along the bed and banks of the
river channel between the pegs placed on either side of the river channel where the
dry banks meet the water.
It must be ensured that the chain follows all the undulations of the bed and banks of
river channel and is not pulled taught.
The length of the chain is the measured by feeding the chain and a tape measure
vertically through your hands simultaneous.

Wetted Perimeter – Strengths and Justifications
This method was representative of the entire channel at each site and so bias or
subjectivity in our technique was reduced.
This technique was easy to replicate at each of the three sites survey. Therefore,
the data we collected could be directly compared between different sample sites.
This gave a greater accuracy to our results so our conclusions would be more
reliable.
This data was collected as the wetted perimeter of a river channel is one of
components used to calculate the Hydraulic Radius . The hydraulic radius for each
site was then used to try explain any changes in velocity found.

Wetted Perimeter – Limitations &
Improvements
If the chain is not forced into all undulations found on the river bed and banks the
length of the wetted perimeter could be underestimated.
Errors could occur when the chain is measured against the tape measure because
the chain has not been held vertically as it is fed through your hands.
Any error in measuring the width of the wetted perimeter will result in an
inaccurate value been calculated for the river hydraulic radius. This in turn could
affect the reliability of our conclusions.
The only way to improve this method is to be careful when placing the chain across
the river beds and banks and when the total length of the chain is been measured

Bedload Size
To work out the width of the river a peg was placed on either side of the river channel
where the dry banks meet the water. A line was run between these two pegs and in
order to avoid drag, the line was pulled tight at 900 above the flow of the river. The
length of the line was then measured using a 30 meter tape measure.
To work out at what intervals to measure the depth of the river the width was divided
by 10. At each of the 9 interval a meter ruler was placed in the water with its thin
edge facing upstream to measure the depth.
The stone touching the bottom of the meter ruler was then measured along its
B – axis.

Bedload Size – Strengths and Justifications
reduced. This technique was easy to replicate at each of the three sites surveyed.
Therefore, the data we collected could be directly compared between different
sample sites. This gave a greater accuracy to our results so our conclusions would be
more reliable.
This data was collected as the roughness of a river channel is one of components used
to calculate the hydraulic radius . The Hydraulic Radius for each site was then used to
try and explain any changes in velocity found.
As the size of the bedload was measure at 9 points across each of the downstream
cross-sections , there was sufficient data to complete a Mann Whitney U- test. This
test would then see if there was a statically significant difference between the size of
the bedload at Helwath Beck and Jugger Howe Beck and between Jugger Howe Beck
and Broxa. If there was a difference in size it could be inferred that size does influence
the velocity of the river.

Bedload Size – Limitations
The size of the bedload was determined by measuring the B – axis with a ruler.
Gaining an accurate result was difficult as the sides of the bedload were not straight
and the length varies across the B – axis.
This technique could be biased in that it is easier to pick up the larger pieces of
bedload located under the metal ruler. This would skew our data collection in favour
of the larger stones at the expense of the smaller stones.
This method only calculates the size of the bedload and does not take into account
how the stone shape changes downstream. The shape of the bedload also influences
how much friction the water has to overcome. As the bedload becomes more
rounded downstream the river has to overcome proportionally less friction and its
velocity should increase. This method only takes into account how the size of the
bedload influences the river velocity, when in reality it is the both the size and shape
of the bedload that influences velocity.
Therefore, the we could question whether the data we collected would allow us to
reach a reliable conclusions about what factors influence mean channel velocity.

This technique could have be biased in that it is easier to pick up the larger pieces of
bedload located under the metal ruler. This would skew our data collection in favour
of the larger stones at the expense of the smaller stones.
This method only calculates the size of the bedload and does not take into account
how the stone shape changes downstream. The shape of the bedload also influences
how much friction the water has to overcome. As the bedload becomes more
rounded downstream the river has to overcome proportionally less friction and its
velocity should increase. This method only takes into account how the size of the
bedload influences the river velocity, when in reality it is the both the size and shape
of the bedload that influences velocity.
Therefore, the we could question whether the data we collected would allow us to
reach a reliable conclusions about what factors influence mean channel velocity.
Between Jugger Howe Beck and Broxa there was very little reduction in median stone
size and it was inferred that this small reduction in roughness had little influence on
the increase in velocity. If smoothness of the stones had also been investigated it
could have been found that it was the shape of the stones and not the size that had
had an influence on the increase in velocity in this stretch of river.

Bedload Size – Improvements
The B - axis could have been measured using callipers instead of a ruler. The distance
between the pincers of the callipers could then have been measured again the a ruler.
This would have resulted in more accurate measurement of the bedloads B – axis.
To attain more accurate data for the size of the bedload I could measure the A, B and
C axes and then work out the average size. This could have made the results more
accurate and therefore the conclusions reached about how the roughness of the
wetted perimeter influences the velocity more reliable.
I could also have measured the shape of the bedload using the ‘Powers’ Scale of
Roundess to place the bedload measured into six different categories from very
angular to well rounded.
Then using the chi - squared (X2) test these different categories of bedload shape could
then have been used to see if there was any statically significant difference of
roundness between Helwath Beck , Jugger Howe Beck and Broxa.
If a statistically significant difference in shape was found it could have been inferred
that it is mot just size but also shape that influences the mean velocity of the river.

Gradient
A 20 meter stretch of the river was measured downstream using a 30 meter tape
measure. A surveyors level was set up in the middle of this 20 meter stretch at the
side of the river channel and levelled.
Two graduated E staffs were placed vertically at either end of the 20 meter stretch.
The bottom of these poles been aliened with the surface of the water in the river.
The difference in height is then measure between each pole and the level. The
vertical drop in horizontal height (cm) can be worked out.
The measured change in horizontal height and vertical distance downstream are then
used to work out the gradient.
This process was repeated at each of the downstream sites so that the gradient of the
waters surface could be compared between the sites.

Data Presentation
and
Analysis

Types of Data Presentation and Analysis Used.
Flow Lines
Cross – Sections
Bar charts
Dispersion Graphs
Central Tendency - Range, Median and Inter Quartile Range
Mann Whitney U Test

Group 7
Velocity
0.125 - 0.125 - 0.08
0.11 – 0.26 – 0.135
0.33 – 0.26 – 0.25

The Velocity increased form 0.11 ms-1 at Helwath Beck to 0.16 ms-1 at Jugger Howe
Beck , an increase of 45%.
From Jugger Howe Beck to Broxa it increased from 0.16 ms-1 to of 0.28 ms-1 an increase
of 75%.
0.125 - 0.125 - 0.08 // 0.11 – 0.26 – 0.135 // 0.33 – 0.26 – 0.25
The Gradient decreased form 0.021 m/m at Helwath Beck to 0.013 m/m at Jugger
Howe Beck , a decrease of 38%.
From Jugger Howe Beck to Broxa it decreased from 0.013 m/m to 0.008 m/m a
decrease of 38%.

The wetted perimeter increased form 2.76 meters at Helwath Beck to 7.25 meters at
Jugger Howe Beck , an increase of 162%.
From Jugger Howe Beck to Broxa it increased from 7.25 meters to 8.92 meters an
increase of 23%.
The mean present flow depth and river width also increased downstream. This meant
that the cross – sectional area of the river increased from 0.16 m3 at Helwath Beck to
0.48 m3at Jugger Howe Beck, an increase of 200%.
From Jugger Howe Beck to Broxa it increased from to 0.48 m3 to 0.92 m3 an increase of
91%.
The reasons why the CSA increase down stream was due to an increase in the
drainage basin of the river from 10 km2 to 48 km2.
As the cross – sectional area of the river increased at a faster rate than the wetted
perimeter the hydraulic radius would also have increased downstream. Therefore, as
the channel loses proportionately less energy in overcoming friction the mean velocity
of the river channel would have increased

The hydraulic radius increased form 0.06 at Helwath Beck to 0.07 at Jugger Howe
Beck , an increase of 17%.
From Jugger Howe Beck to Broxa it increased from 0.07 to 0.10 an increase of 42%.
As the hydraulic radius of the river channel increases the channel loses
proportionately less energy in overcoming friction and the mean velocity of the river
channel increases.
These figures indicate that the increase in the hydraulic radius has had a greater
influence on the channel velocity between Jugger Howe Beck and Broxa than between
Helwath Beck and Jugger Howe Beck.

The median size for the B – axis of bedload size at Helwath Beck was the greatest at
24 cm and had a range of 14.5 cm, with the highest and lowest sizes been 25 cm and
10.5 cm respectively.
The median size for the B – axis of bedload size at Jugger Howe Beck was smaller at 7
cm and had a range of 7.5 cm, with the highest and lowest sizes been 11 cm and 3.5
cm respectively.
The median size for the B – axis of bedload size at Broxa was the even smaller at 5 cm
and had a range of 4 cm, with the highest and lowest sizes been 6.5cm and 2.5 cm
respectively.

The data between Helwath Beck and Jugger Howe Beck shows that there is a large
difference between the median size of bedload of 17 cm a 71% change in median size
and only a very small overlap between the two ranges of bedload size of 0.5 cm.
Since the bedload size is of a much smaller size at Jugger Howe Beck than at Helwath
Beck it could be inferred that the roughness of the wetted perimeter has greatly
decreased.
Therefore, this reduction in channel roughness could have had a great influence on
the increase in the mean channel velocity as the channel loses proportionately less
energy in overcoming friction.

The data between Jugger Howe Beck and Broxa shows that there is only a small
difference between the median size of bedload of 2 cm a 28% change in size and a
relatively large overlap between the two ranges of bedload size of 3 cm.
Since there is little difference in bedload size between Jugger Howe Beck and Broxa it
could be inferred that the roughness of the wetted perimeter has remained almost
the same.
Since the mean channel velocity is greater at Broxa than at Jugger Howe Beck this
increase must have been mainly caused by an increase in the hydraulic radius and only
marginally by the reduction in the roughness of the wetted perimeter.

To add greater validity to our analysis and increase the reliability of our conclusions I
conducted a Mann Whitney U test to see if there is a statistically significant difference
the median bedload size at Helwath Beck and Jugger Howe Beck and then between
Jugger Howe Beck and Broxa.
The result of the test showed there was a statistical significant difference between the
median bedload size between Helwath Beck and Jugger Howe Beck. There was less
than a 5% probability that this difference happened by chance.
However, there was not a statistical significant difference between the median
bedload size between Jugger Howe Beck and Broxa.

Dispersion Graphs
(Describe, Strengths, Weakness & Justification)

Describe how to Complete a Dispersion Graph
The x – axis was labelled with the three different downstream sample sites called
Helwath Beck, Jugger Howe Beck and Broxa.
An appropriate scale for the bedload size was then calculated for the y – axis by
working out that the highest value for the three sites was 24 cm and lowest value was
2.5 cm.
The values of the nine bedload samples for Helwath Beck were then plotted vertically
against the y - axis. Where the values were equal they were plotted adjacent to each
other.
This process was repeated further along the x – axis for the sites of Jugger Howe Beck
and Broxa.
The median and a box and whisker plot where then labelled on the graph for each of
the different sample sites.

Strengths & Weaknesses of a Dispersion Graph
It provides a clear visual representation of the range and clustering of the bedload size
at each of the three downstream sample sites. (S)
It allows a clear visual comparison of any similarities or differences that occur in the
range and clustering of the bed load size between each of the three downstream
sample sites. (S)
Valid conclusions can then be drawn about how bedload size influences the mean
channel velocity from the varying ranges and clustering illustrated at each of the
downstream sample point. (S)
It may be difficult to read the actual values of the individual stone sizes if the scale of
the y – axis is to small. (W)
It cannot used to graph data from categorised variables such as bedload shape. (W)
It cannot be used to compare data form more than one variable e.g. Hydraulic radius
verses velocity. (W)

Justification of a Dispersion Graph
Part of my aim was to investigate how different factors such as the roughness of the
wetted perimeter contributed to the downstream increase in mean channel velocity.
Therefore, a dispersion graph was constructed to visually compare how the
downstream changes in the size of bedload and its clustering may have influenced this
velocity.
The graph showed that there was a large difference in bedload size between the
sample sites of Helwath Beck and Jugger Howe Beck as 4 of the 9 stones at Helwath
Beck where clustered above the median of 24 cm and only one of the smaller stones
was of a size that overlapped with the stones sampled at Jugger Howe Beck which
were evenly distributed between 11 and 3.5 cm.
However, it was found that there was only a small difference in bedload size between
Jugger Howe Beck and Broxa as 8 of the 9 largest stones at Broxa were larger than the
smallest stone sampled upstream at Jugger Howe Beck.
This data clearly illustrated my conclusion that the downstream change in roughness
of the wetted perimeter had a diminishing influence on the increase in mean channel
velocity.

The Mann Whitney U Test
for the River Derwent

The First Mann Whitney U Test for
-
(Helwath Beck and Jugger Howe Beck)
This is a statistical test to determine whether 2 sets of data of the same variable are
significantly different. It tests the difference between the medians of the two data
sets.
By using the critical values table, it is possible to assess the probability to which any
observed difference is a result of chance.
I wrote down the null hypothesis and research hypothesis and set the level of
significance at 0.05.
NH – There is no significant difference in the size of bedload between Helwath Beck
and Jugger Howe Beck.
RH -There is a significant difference in the size of bedload between Helwath Beck and
Jugger Howe Beck.

The best way to proceed is to incorporate the finding into a table that allows you to
calculate the results
I then ranked the size of the bedload in terms of their position in both samples. The
largest stone was given the lowest rank and the smallest the highest rank. Where the
size of the stones were the same I took the average of the rank values.
I then totalled the ranks for the bedload size of Helwath Beck and Jugger Howe Beck.

I then calculated the U values for both samples using the formula below.
9 x 9 + 9 x (9 +1) – 46 = 80
2
9 x 9 + 9 x (9 +1) – 125 = 1
2

.
I used the critical values table to work out that the critical value for this set of data
was 17 at the 95% confidence level.
I found that the value for U2 of 1 was lower than the critical value of 17. Therefore, I
accepted my research hypothesis that there is a statistical significant difference in
the size of bedload between Helwath Beck and Jugger Howe Beck.

The Second Mann Whitney U Test for
-
(Jugger Howe Beck and Broxa)
This is a statistical test to determine whether 2 sets of data of the same variable are
significantly different. It tests the difference between the medians of the two data
sets.
By using the critical values table, it is possible to assess the probability to which any
observed difference is a result of chance.
I wrote down the null hypothesis and research hypothesis and set the level of
significance at 0.05.
NT – There is no significant difference in the size of bedload between Jugger Howe
Beck and Broxa.
RH -There is a significant difference in the size of bedload between Jugger Howe Beck
and Broxa.

The best way to proceed is to incorporate the finding into a table that allows you to
calculate the results.
I then ranked the size of the bedload in terms of their position in both samples. The
largest stone was given the lowest rank and the smallest the highest rank. Where the
size of the stones were the same I took the average of the rank values.
I then totalled the ranks for the bedload size of Jugger Howe Beck and Broxa.

I then calculated the U values for both samples using the formula below.
9 x 9 + 9 x (9 +1) – 67 = 59
2
9 x 9 + 9 x (9 +1) – 104 = 22
2

.
I used the critical values table to work out that the critical value for this set of data
was 17 at the 95% confidence level.
I found that the value for U2 of 22 was higher than the critical value of 17.
Therefore, I accepted my Null hypothesis that there is no statistical significant
difference in the size of bedload between Jugger Howe Beck and Broxa

Mann Whitney U Test – Analysis
There was a statistical significant difference in the median bedload size between
Helwath Beck and Jugger Howe Beck. As there was less than a 5% probability that this
difference happened by chance.
The bedload at Jugger Howe Beck was smaller than that found at Helwath Beck. From
this it can be inferred that the roughness of the wetted perimeter at Jugger Howe
Beck is lower which means that the river uses proportionally less energy to overcome
friction and the velocity should increase.
There was not a statistical significant difference in the median bedload size between
Jugger Howe Beck and Broxa. There was more than a 5% probability that this
difference happened by chance.
The bedload at Broxa was not significantly smaller than that found at Jugger Howe
Beck. From this it can be inferred that there is little difference in the roughness of the
wetted perimeter between the two sites and therefore, the river should be using
proportionally the same energy to overcome friction.

Mann Whitney U Test
(Describe, Strengths, Weakness & Justification)

Describe how to Complete a
Mann Whitney U Test
First set out the null and research hypothesis stating that there is either no
significance or that there is a significance difference in the size of bedload between
Helwath Beck and Jugger Howe Beck.
Place the individual values for bedload size into two columns, the first for the values of
Helwath Beck and the second for the values of Jugger Howe Beck.
Rank the size of the bedload in terms of there position in both samples. The largest
stone been given the lowest rank and the smallest the highest rank. For stones of the
same size take the average of the rank values.
Then separately calculate the sum of the ranks for Helwath Beck and Jugger Howe
Beck.

Use the sum of the ranks for Helwath Beck and Jugger Howe Beck to calculate the
values of U1 and U2 by inserting them into the formula.
The critical values table was then used to work out that 17 was the critical value for
this set of data at a 95% confidence level.
As the value for U2 of 1 was lower than the critical value of 17 I accepted my research
hypothesis that there was a statistical significant difference in the median size of
bedload between Helwath Beck and Jugger Howe Beck.

Strengths & Weaknesses of the
Mann Whitney U Test
This is a statistical test to determine whether the median for 2 sets of data of the
same variable are significantly different or have occurred by chance. (S)
It can be used on 2 sets of data that have different sizes, e.g. one data set could have
10 values and the other only 8 values. (S)
It contains a lengthy calculation that can be prone to human error. This human error
could result in the wrong conclusion been reached as the U values have been
calculated incorrectly. (W)
It does not explain why the difference in the two data sets has occurred. (W)
The test cannot be applied to data that has been categorised such as bedload shape.
(W)

Justification of the Mann Whitney U Test
Part of my aim was to investigate how different factors such as the roughness of the
wetted perimeter influenced the mean channel velocity.
Therefore, I conducted a Mann Whitney U Test to see if there was a significant
downstream change in the median size of bedload between the sample sites of
Helwath Beck , Jugger Howe Beck and Broxa.
The first test proved that there was a statistical significant difference of the median
size of bedload between Helwath Beck and Jugger Howe Beck as one of the U values
of 1 was below the critical value of 17.
The second test proved that there was no statistical significant difference of the
median size of bedload between Jugger Howe Beck and Broxa as both the U values of
59 and 22 were above the critical of 17.

This test added statistically validity to my conclusion that the downstream change in
roughness of the wetted perimeter had a diminishing influence on the increase in
mean channel velocity.
It was an appropriate technique to analyse the data collected for bedload size as it
was measured in centimetres, which was a form of ordinal data that could be ranked.
As 9 stones were measured at each site this falls between the minimum of 5 and the
maximum of 20 pieces of data recommend to carry at this test.

Conclusion
(what did I Learn)

The investigation did show an overall increase in downstream mean channel velocity
for the upper River Derwent even though the gradient did decreased.
However, the mean channel velocity increased at a faster rate the further the river
travelled downstream. Between the two sample sites nearest to the rivers source
there was an increase from 0.11 ms-1 to 0.16 ms-1 a relative change of 45% compared
to a change from 0.16 ms-1 to 0.28 ms-1 a relative increase of 75% between the two
sites furthest from the rivers source.
The overall, increase in downstream velocity can be attributed to two factors: a) the
increase in the efficiency of the river as the hydraulic radius becomes larger and b) the
reduction in the roughness of the wetted perimeter as the river has had more time to
erode its bed and banks.
However, there was a difference in the major factor that influenced the increase in
velocity between the two upstream sites of Helwath Beck and Jugger Howe Beck and
the two lower stream sites of Jugger Howe Beck and Broxa.

In the upper reach the major factor that influenced the increase in channel velocity
was probably the statistically significant reduction in the bedload size of the wetted
perimeter as there was only a small increase in the hydraulic radius of 17%.
In the lower reach of the river the major factor that influenced the increase in channel
velocity was probably the large increase in the hydraulic radius of 41% as there was no
statistically significant reduction in the bedload size of the wetted perimeter.
I have learnt that the mean channel velocity does increase downstream as Schumm’s
or Bradshaw’s model predicts and that gradient, hydraulic radius and the wetted
perimeter do influence this change as AS geography textbooks state.
However, my understanding of the reasons behind this increase in velocity has
developed beyond the theory provided in the AS geography textbooks. The textbooks
do not mention that the major factor influencing mean channel velocity may vary over
different reaches of a river.

Evaluate the success of your investigation using each section listed below
Aim
Location of the study area
Sampling Methods
Data Collection Methods
Data Presentation
Accuracy of Results
Reliability of Conclusions
Evaluate the strengths and weaknesses of your fieldwork investigation using each of
the section listed above.
What could I have done to improve this fieldwork investigation.
What could I have done to extend this fieldwork investigation.
In what ways would you conclusions be of use to other geographers etc.

My aim was
‘To investigate the extent that downstream mean channel velocity for the upper
Derwent river increases. Even though the gradient of the river decreases
downstream’.
My investigation was successful because not only did we discovered that the mean
velocity does increase downstream, but it increases at a faster rate the further the
river moves downstream. For example in the upper reach between the sites of
Helwath Beck and Jugger Howe beck there was a 45% increase compared to a 75%
increase in the lower reach of the river between the sites of Jugger Howe Beck and
Broxa.
I also discovered that both the hydraulic radius of the river channel and the roughness
of the wetted perimeter do influence the mean velocity as the geography textbooks
state in there theory sections.
However, my understanding was further developed as I discovered that a decrease in
roughness of the wetted perimeter has a major influence on the change in mean
velocity in the upper reach of the river Derwent between Helwath Beck and Jugger
Howe Beck and only a minor influence on the change in mean velocity in the lower
reach between Jugger Howe Beck and Broxa.

Parts of the method could have been evaluated by looking at the results obtained. For
example at Helwath Beck timing of the point velocity measurement for the right-hand
side of the channel was stopped because it exceeded 1 minute.
This timing was converted into a velocity of 0.08 ms-1. This results might not have
been a true reflection of the rivers velocity at this point. For the very low velocity at
this point in the river the hydro prop could have over estimated the true velocity.
The mean channel velocity of 0.11 ms-1 which was calculated using the three point
velocities could also have been over estimated. Therefore, the results for the mean
channel velocity would not have been accurate and any conclusions drawn could have
been unreliable.
To overcome this inaccuracy an electromagnetic open channel flow meter could have
been used. This instrument would have reduced the overestimate of this point
velocity. This is because the electromagnetic open channel flow meter works at
velocities as low 0.01 ms-1.

The results could have been evaluated by comparing them the average results
obtained by merging the data collected by all the groups that survey the river
channel.
My results for the increase in downstream mean channel velocity and the hydraulic
radius reflected the general trends for that of the group average.
Also there was only a small difference in the actual results. At Helwath Beck the
mean velocity was underestimated by 10% and at Jugger Howe Beck and Broxa
they were overestimated by about 15%.
This was an acceptable margin of error given that the point velocities were only
measured at three points along the river cross – section and then averaged to give
a mean channel velocity at each site.
However, there was a slightly larger margin of error for the actual hydraulic radius
results as they were within + or – 30% of the groups average for each site.
It can therefore, be inferred that the results that collected where fairly accurate
and therefore the conclusions drawn reliable.

My investigation could have be improved and /or extended in the following ways;
Data could have been collected from a 1st order streams. This data could then have
been added to the data collected from the 2nd to 4th order streams to see if my
investigation still reached the same conclusion that mean velocity does increase
downstream at an ever increasing rate and that the roughness of the wetted
perimeter still has a greater influence in the higher reaches of the upper Derwent
river.
The number of sample sites for each order stream could have been increased from 1
to 3. This would have given data that was more representative of the river channel
and the conclusions that were reached would have been more reliable.
The number of points that velocity was measured along the cross – sections could
have been increased from 3 to 5. This would have reduced the margin of error that
one anomalous result had when calculating the mean channel velocity from 33.3% to
20%. Therefore, the mean velocity obtained would have been a truer reflection of the
actual mean velocity of the river channel and any conclusions drawn from this data
would have been more reliable.

To attain more accurate data for the size of the bedload I could measure the A, B and
C axes and then work out the average size. This could have made the results more
accurate and therefore the conclusions reached about how the roughness of the
wetted perimeter influences the mean velocity more reliable.
I could also have measured the shape of the bedload using the ‘Powers’ Scale of
Roundess. The bedload measured is placed into one of the six different categories
from very angular to well rounded.
Then using the chi - squared (X2) test these different categories of bedload shape to
see if there was any statically significant difference of shape between Helwath Beck,
Jugger Howe Beck and Broxa.
If a statistically significant difference in shape was found it could have been inferred
that it is not just size but also shape that influences the mean velocity of the river.

The landuse of the drainage could be mapped to investigate if this was a factor in the
increase of aret of discharge.
Compare the with manning equation is evaluate
H storm curse
Work out bank full to see.

Fieldwork Cranedale

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