Fieldwork investigation - Margam

Question 1

What was the aim of your fieldwork enquiry?

Answer 1

To investigate how the characteristics of a river channel may vary from the source to the mouth along the River Ogmore.

Question 2

Give the 4 main objectives/hypotheses:

Answer 2

1: The velocity of the River Ogmore increase from source to mouth.
2: The clast size and shape in the River Ogmore will decrease from source to mouth.
3: The width and depth of the River Ogmore will increase from source to mouth.
4: The discharge of the River Ogmore will increase from source to mouth.

Question 3

What does the bradshaw model do?

Answer 3

The Bradshaw Model helps describe the changes expected as a river’s discharge will travel from its source in the upper course, through the middle course and to the lower course to the mouth.

Question 4

Describe the characteristics of the bradshaw model:

Answer 4

When the triangle gets wider towards the downstream section it means that on average that variable increases with distance downstream. If the triangle decreases in size it means that on average the variable decreases with distance towards the mouth.

Question 5

What does the bradshaw model show about the River Ogmore?

Answer 5

The Bradshaw model for the River Ogmore shows that discharge increases downstream as well as load quantity. Occupied channel width and channel depth also increases but not massively as well as average velocity.

However the load particle size decreases downstream as well as channel bed roughness and slope angle/gradient. These variables are all decreasing downstream at the same rate.

Question 6

What does the long profile do?

Answer 6

The long profile shows how a river’s gradient changes as it flows from its source to the mouth.

Question 7

What does the long profile show about the source of the River Ogmore?

Answer 7

The source of the river is in an upland area where vertical erosion is present, creating a v-shape valley.

Highland areas are usually composed of hard angular rocks, which are ideal for forming features like waterfalls and rapids.

Due to the large angular rocks present, frictional drag is greater which causes low velocity and indicates a low hydraulic radius.

Question 8

What does the long profile show about clast size and shape in the River Ogmore?

Answer 8

The average clast size/shape and bedload present in the lower course is much smaller compared to the upper course, this means there is less frictional drag which causes an increase in velocity in the River Ogmore.

Question 9

What does the long profile show about the lower course of the River Ogmore?

Answer 9

As the River Ogmore flows towards the mouth, the slopes become less steep due to a decrease in gradient.

Eventually the river will flow over flat land as it approaches the sea, lateral erosion is more present in the lower course which cause the river width to increase as well as depth.
This ultimately causes an increase in river discharge and hydraulic radius.

Question 10

Where is the River Ogmore located?

Answer 10

The River Ogmore is located in South Wales, in the suburb of Margam.

Question 11

What is the geology of the area surrounding the River Ogmore?

Answer 11

The Geology of the area surrounding River Ogmore has mainly moderate permeability with some areas of mixed permeability and very low permeability.

Question 12

What is the area of the River Ogmore like?

Answer 12

Near the source of the river the area is covered mainly with woodland, grassland and mountain heath.

Near the mouth of the River Ogmore more built up areas are present including Ogmore Vale.

Question 13

What is the annual rainfall at the River Ogmore?

Answer 13

The annual rainfall is between 3,000 and 4,000 mm, the middle section of the river receives between 1,600 and 2,000mm of rain per year and the mouth gets between 1,100 and 1,200 mm of rainfall per year.

Question 14

What is the land use of the area surrounding the River?

Answer 14

The land use in this catchment area is 55% grassland farming and 20% is forest cover.

Question 15

What is the gradient like in the surrounding area of the river?

Answer 15

The gradient of the area is higher at source which creates the a v-shape valley to form.

As the river travels towards the mouth the relief of the land is much flatter which allows more urban areas to be built up.

Question 16

What was the sampling strategy used to measure velocity and why?

Answer 16

Systematic sampling:

Using systematic sampling give a more accurate representation of velocity and allows us to choose where to measure.

Question 17

Why was velocity measured?

Answer 17

We measured velocity as it allowed us to measure river discharge.

Question 18

Outline method used to measure velocity:

Answer 18

We identified 3 sections on the river, the left side, middle and right side of the river.

We used a hydroprop flow meter to measure the velocity in each section.
We placed the hydro prop flowmeter midway through the water and used a stopwatch to time how long it took for impeller to reach the spindle.

Question 19

What were the limitations of using the method to measure velocity?

Answer 19

When measuring velocity, sediment e.g. boulders and large rocks could affect the data collected and not be a true representation of the velocity as the sediment may have caused frictional drag which causes velocity to decrease.

There also may have been a delay in saying when the impeller reached the end of the spindle which means the data collected may be inaccurate.

Question 20

What sampling strategy was used to measure clast size and shape?

Answer 20

Systematic sampling:

Allows us to choose where to measure and where would be a true representative of the sediment present.

Question 21

Why was clast size and shape measured?

Answer 21

Clast size and shape was measured as it would help indicate how velocity is affected and whether frictional drag is present and what types of erosion is present also.

Question 22

Outline the method used to measure clast size and shape:

Answer 22

Found 10 random pieces of sediment across the length of the river bed. Measured the length of each sediment piece using a calliper.
We then worked out the shape using powers scale of roundness.

Question 23

What were the limitations of using the method to measure clast size and shape?

Answer 23

When measuring sediment roundness from powers scale of roundness, the view of how round a sediment piece is very subjective and may not be an accurate representation for the data.

The specific length of each sediment piece was not measured, this gives inconsistent data, to improve this we should have measured the longest side of each sediment piece.

Question 24

What sampling strategy was used to measure depth?

Answer 24

Systematic sampling: This sampling strategy was used to collect representative data of the channel

Question 25

Why was the depth of the river measured?

Answer 25

Depth was measured as it helps work out information about discharge and hydraulic radius.
Measuring this also helps working out the cross sectional area of the river.

Question 26

Outline the method used to measure the depth of the river:

Answer 26

We measured river depth by dividing the river channel width by 6 to get 5 sections. We put a metre stick in each of the five sections and measured the depth of the river

Question 27

What were the limitations of using the method to measure river depth?

Answer 27

High velocity in the River Ogmore caused water to splash up onto the metre stick which meant it was difficult to read which can lead to inaccurate data.

Question 28

What sampling strategy was used to measure width of the river?

Answer 28

Stratified sampling: measured the upper, middle and lower course of the river

Question 29

Why was the width of the river measured?

Answer 29

Width was measured as it will help work out hydraulic radius and river discharge. Measuring width allows us to calculate the cross sectional area of the river.

Question 30

Outline the method used to measure river width:

Answer 30

The width of the river channel was measured using a tape measure. We placed one end of the tape measure on one side of the river where the water meets the bank, we then pulled the tape measure across the river to the other side again to where the water touches the bank.

Question 31

What were the limitations of using the method to measure width of the river?

Answer 31

It may be unclear where the water meets the bank which causes inaccurate data to be collected.

Question 32

What sampling strategy was used to measure river discharge?

Answer 32

Systematic and stratified sampling was used as these were the strategies used for depth, width and velocity

Question 33

Why was river discharge measured?

Answer 33

Measuring river discharge allows us to know how much water the river is carrying.

Question 34

Outline the method used to measure river discharge?

Answer 34

Calculation :

Cross sectional area X Velocity

Question 35

What were the limitations of using the method to measure river discharge?

Answer 35

If the cross section area or velocity was miscalculated, the discharge would be wrong which causes incorrect data.

Question 36

Why was a risk assessment created?

Answer 36

The risk assessment was created before completing the fieldwork in the River Ogmore to ensure that all individuals were aware of the risks that we may face going into the field.

We assessed the surrounding area as well as the weather conditions at the time and came up with risks that were more likely to happen.

Question 37

What were the hazards of the fieldwork?

Answer 37

Deep water - drowning - medium risk

Wet surfaces - tripping, falling and slipping - high risk

Weather/Temperature - getting cold and feeling ill - medium

Traffic/Busy roads - getting hit by a car - medium

Infections from water - getting ill - low

Question 38

How could the hazards of the fieldwork be managed?

Answer 38

Deep water - Check river depth and velocity

Wet surfaces - Watch where you are walking and wear suitable footwear

Weather - Wear suitable clothing (waterproof) with plenty of layers

Traffic - Be sensible and look left and right before crossing a road

Water infection - Wash hands before eating using hand sanitiser and avoid swallowing river water

Question 39

Outline the use of primary data:

Answer 39

At site 1,2 and 3 primary research was collected for our data using the methods and equipment stated above, these sites were located near the source and in the upper course.

Question 40

Outline the use of secondary data:

Answer 40

At site 4,5 and 6 secondary research was used for our data as the depth of the River Ogmore at the time of our fieldwork was too great to enter.
These sites are located in the middle course and the mouth of the river.
With the risk of drowning being too high, secondary data was used to complete our data sheet.

This secondary research was collected from the FSC staff when the river was safer to enter and the weather conditions were not as severe.

Question 41

How did you choose to present your data for clast size and shape?

Answer 41

I chose to present my data of clast size and shape as pie charts as it is a visual representation of how clast shape has changed downstream the River Ogmore.

The pie charts show house clast shape decreases, increases, appears or disappears downstream.
This allows us see how clast shape differs throughout the upper,middle and lower course.

Question 42

How did you choose to present your data for river velocity?

Answer 42

In a bar graph as it provides a visual representation of how the average velocity changes downstream.

From the bar chart there is no clear pattern of how velocity changes downstream. This could be due to the large amount of rainfall present at the time of collecting the data.

Question 43

How did you choose to present your data for river depth?

Answer 43

I have chosen to use a GIS from Google Earth to present my data for depth of the River Ogmore as it visually shows the area of each site.

It also shows the surrounding area which allows us to look at the background information the each village which could give further information of the river

Question 44

How did you choose to present your data for river discharge?

Answer 44

I have chosen to present my river discharge data in a bar chart as it is a visual demonstration of the pattern of river discharge downstream.

The data and pattern shown in the bar chart supports my hypothesis - This indicates that the width and depth of the River Ogmore will increase downstream also.

Question 45

How did you choose to present your data for cross sectional area (width and depth)

Answer 45

I have chosen to present my cross sectional area data in a bar chart as it visually represents my hypotheses of both width and depth.

This bar graph shows the gradual pattern of how cross sectional area increases downstream with each site.

Question 46

How would you analyse your data?

Answer 46

Use Spearman’s Rank Correlation Coefficient

Question 47

What does Spearman’s rank do?

Answer 47

The Spearman’s Rank Correlation Coefficient is used to discover the strength of a link between two sets of data. In this case it is the link between distance downstream and river discharge.

Question 48

Outline the results from your spearman’s rank:

Answer 48

The absolute value of Spearman’s Rank is greater than the critical value, the null hypothesis is rejected and the alternative hypothesis is accepted as it is significant.

This ultimately shows that there is a clear link between river discharge and distance downstream.

Question 49

How is Spearman’s rank a helpful technique?

Answer 49

This is a helpful technique to use as it uses the data collected and clearly shows whether there is a link or not which easily proves or disproves a hypothesis.

Question 50

What was the conclusion for river velocity?

Answer 50

The average velocity of the River Ogmore show no clear pattern of how velocity changes downstream - does not support my hypothesis and brad shaw model.

The high rates of precipitation caused the river discharge to increase.

Question 51

How did velocity change from site 1 to 3?

Answer 51

In the upper course, at site 1 there was a steep gradient which caused the large amounts of rain to move at a quicker rate, increasing velocity. At site 2 however the average velocity drops, the reason for this is unknown, however in site 3 it increases again.

Question 52

What was the conclusion for clast size and shape in upper course?

Answer 52

The pie charts presenting clast size and shape show that very angular, angular and subangular sediment pieces are most common in sites 1 and 2 which are located in the upper course of the River Ogmore.

Question 53

What was the conclusion for clast size and shape in the middle course?

Answer 53

Sediment pieces begin to getter rounded in sides 3 and 4 but angular and subangular sediment pieces are still present. This suggests that in the middle course of the River Ogmore, sediment begins to become rounder.

Question 54

What was the conclusion for clast size and shape in the lower course?

Answer 54

At sites 5 and 6 sediment pieces begin to become more rounded, subrounded and well rounded with very little angular sediment pieces being seen. This is because of the presence of attrition present which causes the sediment to get smaller and rounder.

Question 55

Do the conclusions of clast size and shape support your hypothesis?

Answer 55

These results support the hypothesis about clast size and shape.

These results represent a negative correlation as the clast size and shape decreases when the rivers distance downstream increases.
This conclusion agrees with the bradshaw model theory

Question 56

What was the conclusions for cross sectional area in the upper course?

Answer 56

From the cross sectional area data shown in the bar graph, it is evident that both depth and width of the River Ogmore increases downstream from source to mouth.

At sites 1 and 2 the increase is very minimal from 0.22 to 0.68 m2.

Question 57

What was the conclusions for cross sectional area in the middle/lower course?

Answer 57

From site 3 to 6 the increase of cross sectional section of each site is between 4 and 9 m2. This indicates that the further downstream the River Ogmore the cross sectional area increases with a greater amount each time.

Question 58

Do the conclusions for cross sectional area support your hypothesis?

Answer 58

These results support my hypothesis and shows a positive correlation between distance downstream and cross sectional area.

These statements are supported through the GIS which presents the increase of depth downstream.

Question 59

Would more time give better results?

Answer 59

More time should be given to allow the research and data to be more detailed.

One day is not enough time to go to every site and fully investigate and measure every hypothesis in great depth to reach an absolute conclusion.

Question 60

What could be done with more time and data?

Answer 60

Completing another investigation in the summer which would allow the data and results to be compared to the winter which is when the original data was collected.

By comparing the data in different seasons as well as having more time for each investigation, it would truly measure whether the hypothesis’ made are correct and increase the reliability of the data.

Question 61

Would a more reliable system improve the collected data?

Answer 61

The data capture would be done with a reliable system. To ensure reliable results, the same person should measure the same thing at each site of the river. This will cancel out any individual differences which may cause the data to be skewed.

Question 62

How would a reliable system for collecting data take place?

Answer 62

Human error would be minimised as much as possible to ensure reliable and valid data.

For example, when using a hydro prop flowmeter, the same person should measure it each time, but also making sure that the equipment is measuring the velocity at the same depth for each site to ensure the most valid and consistent data.

Question 63

Would more appropriate sites make better data collection?

Answer 63

More appropriate sites would be chosen which allowed people more access to the river, this would ultimately give more valid results as people would not be rushed out the river due to it not being appropriate for humans.

This would give us more time to ensure that the results were reliable and true to the specific river.