How does Loughton Brook change as it moves downstream?

rained for a few days so we did another calculation, 'bank full', this told us how high the

water would be when the river was about to over flow, We took this measurement so that we could that if it rains on the next day we would still have suitable results to do my coursework.

We took one measurement of the gradient so that we can work out how the speed is

affected by the gradient.

Techniques

Measure the wetted perimeter of the site we used a 30m tape measure and held it at

side of the waters edge and held it across the base of the river and onto the opposite

To measure the wetted perimeter of the site we used a 30m tape measure and held it at

one side of the waters edge and held it across the base of the river and onto the opposite

water edge. We recorded the results on our recording sheet. We chose to calculate the

wetted perimeter, as it is a key feature of rivers efficiency. If the wetted perimeter

increases down to the mouth it shows that more water will travel through and so it will

prove that the river increases efficiency as it goes downstream

To measure the width of the river we just held the measuring tape along the water surface from side to side. We used this method, as it is an easy, efficient and straightforward way to calculate the width. We recorded the results on our recording sheet. We chose to calculate the width, as it is a key feature of rivers efficiency. If the width of the river increases as we go downstream it shows us that more water is traveling through and in conclusion making the river more efficient as we travel downstream.

To measure the depth of the river we divided the width by six and then got a reading for

every sixth of the width. We used the 1 m ruler to measure this. We used this technique

so that we could use the results to draw a hydrograph and see the shape of the banks and

bed. We recorded the results on our recording sheet. We chose to calculate the depth, as

it is a key feature of rivers efficiency. If the depth increases as we make our way

downstream that means that the river is carrying more water so this again will prove that

the river becomes more efficient as it moves downstream.

To measure the gradient we used an 'automatic level5. We did this by using a metal

ruler, which had to be held by a member of my group while the other members of the

group set up the automatic level so it gave us a reading of the gradient. We took two readings at different points of the site and then deducted them from each other, which

gave us the gradient. We recorded the results on our recording sheet. We chose to

calculate the gradient, as it is a key feature of rivers efficiency. If the gradient increases

as we go downstream the water will be traveling at a high speed this means that more

water will travel through and again will prove that the river becomes more efficient as we go downstream.

To measure the pebble sizes we took 10 random samples from each site and for each

pebble we recorded its length, roundness and sphericity. To measure its length we used a 30 cm ruler. We took ten samples so that we could work out an average. This will help

we see the difference between sites at different Stream order. We recorded the results on

our recording sheet. We chose to calculate the pebble size, as it is a key feature of rivers

sediment. If the pebbles become smaller as we go downstream it will tell us that the

sediment is being reduced as it is eroded away in various processes.

To measure the velocity of the flow of water we used a cork, stopwatch and a 1 m ruler.

We timed how long it took for the cork to travel 1 m and calculated the velocity. We

recorded the results on the recording sheets. We chose to calculate the velocity, as it is a

key feature of rivers efficiency. If the velocity increases as we go downstream it again

means that there will be more ware traveling through so it will again prove that the river

becomes more efficient as it goes downstream.

To measure the bank full and low flow measurements we use a 3 meter tape measurer

which I used to measure the real width and depth. This as a result of no rain for the

previous week was unusually low so we to 'bank full5 measurements. These

measurements tell us the more reasonable width and depth. If the depth and width of the

bank full measurements increase as we go downstream we can state that the efficiency of the river increases as we go downstream as it will be able to carry a larger volume of

water. The results that we get can then be used to draw a hydrograph and then compared

with my low flow graph.

Throughout my visit to the sites I used my camera to take pictures of my sites. We wore

Wellington boots and waterproof clothing to keep us dry while we were in the water.

Justification

There were two key questions that we set ourselves before we visited the sites. They are:

• How does efficiency change with distance downstream?

• How does sediment change with distance downstream?

Here is why I used each technique and which key question it gathered evidence for:

• The technique used to measure the width of the river was very efficient and

effective as it was very straightforward. This will gather evidence for the first key question.

* The technique used to measure the depth of the river is very helpful as we can use

the results to draw a hydrograph, which is the best way to show the depth of the

river. This will gather evidence for the first key question.

• The technique used to measure the wetted perimeter wasn't very accurate but it

gave us a rough estimate. We didn't have time to use proper equipment to

measure the real wetted perimeter. This will gather evidence for the first key

question.

• The technique used to measure the gradient was extremely accurate as we used

the perfect equipment it works it out, the 'automatic level'. This will gather

evidence for the first key question.

• The technique used to measure the velocity was used because it gave us its rough

velocity. We used the lightest material possible as a boat. This will gather

evidence for the first key question.

• The technique used to collect the pebbles was used because it gave an average

idea of the major similarities between the 10 samples and the differences between

the other samples collected from other sites. This will gather evidence for the

Second key question.

The limitation for the data is quite low, as we didn't have time to take more results down.

Problems collecting the data

The only major problem from collecting the data was that for the previous week there

was no rain so the water level of the river was quite low. We then had to take

measurements of 'low flow', which was what it was on the day and 'bank full', which

was when the river was about to over flow. This will show that the river is very effective as it erodes the edges of the stones down. This again proves that they

Another problem was that we had misplaced an equipment basket so we had to share with another group. This caused us to lose some time and we had to work fast to finish our measurements, this increases the risk of human error and may have caused some

anomalies in he results that I collected. Another minor problem was, when we were trying to calculate the velocity some leaf litter slowed the cork down,

Problems with the data

The problems with the data occurred because we had problems collecting the data. The

velocity was slower than it should in some sites, as our experiment was not very

effective. Much leaf litter obstructed the cork and slowed it down. As we had lost our equipment basket, we were rushing to finish and take our result and the rush could have caused us to get some anomalous results. Even though I encountered these problems I still believe that it is good enough to answer my key questions.

SECONDARY DATA

There were many pieces of secondary data that I obtain:

• OS map of the area (sheet)

• Information from the web site

• Coursework Preparation (sheet)

• Sampling Techniques (sheet)

• Map of Loughton (sheet)

• Geology of Loughton (sheet)

• Infiltration Rates for different Geological types in Epping Forest (sheet)

• Map of sites (sheet)

• Location of Epping Forest (sheet)

• Pebble Analysis (recording sheet)

• River channel recording (sheet)

The reason why I was presented with the OS map of the area was so that I could clearly

show the location of Loughton Brook. The guide at the Epping Forest Centre gave it to

me.

I then got background information from the website so that I wouldn't miss any key fact.

I did this by myself in my own time.

Map of Loughton (sheet) - this was the most appropriate sheet to show the exact area of

Loughton

Geology of Loughton (sheet) - will shows us the different types of soil and it can be . used to see any pattern to compare

Infiltration Rates for different Geological types in Epping Forest (sheet) - to see whether

any odd results occur at different geological areas

Map of sites (sheet) - This will be used to show the different sites that I visited.

Location of Epping forest (sheet) - this will be part of location as it shows where Epping

Forest is in Redbridge.

Pebble Analysis (recording sheet) - this will be used in the data presentation as it is a

Results sheet

Main recording sheet - this will be used in the data presentation as it is a results sheet

All the sheets that I obtained as secondary data was given to me by the staff at the Epping Forest Field Centre and my school Geography Teacher.

ANALYSIS

OF RIVER EFFICIENCY

To answer my key questions I have gathered the appropriate information to construct graphs and analyse them. In this section of my coursework I and constructing the graphs which then I closely analyse for any sequences or patterns or any anomalies.

Dis from S by Velocity Graph

The graph above shows the velocity by Distance from source. As you can see from the line of best fit, the velocity increases as the distance becomes greater. It has a positive correlation. If the velocity increases as we go downstream that must mean that more water is being transported at the same time. This proves that as we go downstream the river becomes more efficient. As you can see from the graph there is an anomaly at site 10. The relationships between these two features are fairly strong.

The main reason why the velocity increases as we go down stream is that the width and depth of the river increase enabling it to transport more water in the same amount of time and making it more efficient.

The anomaly (1200, 0.53) may have been cause by geology as there might have been less leaf litter in that area enabling it to travel at a greater speed.

Channel Roughness By Velocity Graph

The graph above shows the Channel Roughness by Velocity. As you can see from this graph as the Channel Roughness increases the Velocity Decreases. This is shown when the channel roughness dropped from 0.72 to 0.16 and the velocity increased from 0.5 to 0.12. This means that they are inversely proportional. If the channel roughness is high it means that there is more friction and the water will be flowing through slower. The channel roughness gets less as we go downstream because the high velocity of the water is causing the area to erode and become smoother.

I identified 2 anomalies on this graph they are on site 2. The channel roughness is exceptional low and the velocity is quite high. It is most likely that this was caused by human errors

The channel roughness gradually decreases as we go downstream and velocity increases as we go downstream.

Dis from S by Gradient Graph

The graph above shows the Gradient by Distance from source. As you can see from this line of best fit the Gradient decreases as we move downstream. It has a fairly strong negative correlation. If the gradient decreases as we go downstream that mean that the efficiency must be decreasing. This may not be true because as we move downstream the width and depth of the river increases enabling it to carry more water and increases the efficiency. There fore this may cancel out with the decrease in gradient.

I identified 1 major anomaly (1100, 0). I believe that this was caused human error as one of the groups may not have had time to do it. This I think should have been left out but I left it in so that I could point it out.

This proves that the gradient decreases as we go downstream.

Discharge by Dis from S Graph

The graph above shows the Discharge by Distance from source. As you can see from the graph above the discharge increases as we move downstream. It shows a fairly strong positive correlation. If the discharge increases as we go downstream that means that there is less particles in the water to restrict the flow of water. Therefore this also proves that the efficiency increases as we move down stream.

I identified 1 major anomaly (1200, 0.28). This may have been invasion of the river channel by vegetation. Therefore the particle will be trapped by the vegetation which means that there will be a lot of vegetation in that area. This is the most fitting reason for this anomaly.

Lowflow Graphs for Sites 1 - 5

The 5 graphs above show the Low flow cross-sections for each site. I can see that as we move downstream the depth of the river becomes larger and larger. This again shows the increase of the efficiency of the river. These 5 graphs can be related to the graphs of the Width so that as the width increases as we move further downstream.

The last two graphs interpret the cross section of the river at the meander. As you can see there is a sudden decrease in the depth this is the outside of the meander where the water travels the fastest and causes the most erosion.

BANKFULL

The 5 graphs above show the bank full measurements for each site. Again they show dramatic change in depth and shape of the cross section as we move downstream. This again shows the increase of the efficiency of the river. These 5 graphs can be related to the graphs of the Width so that as the width increases as we move further downstream.

The first three graphs are normal but the last two I believe were taken at a meander as there is a sudden drop on one side of the river the water has been moving the quickest and eroding more. As we move downstream the depth of the river increases. This again proves that the river gets more efficient as we move downstream.

In site 5 there is a gradual increase in depth and then there is a sudden decrease. This is in 0.64 m down to sea level. This shows that there is a meander where this measurement was taken.

ANALYSIS: SEDIMENT

By analysing these graphs I have noticed a distinct pattern. As we move further downstream the majority of pebbles have either a 4 or 5 roundness total. This tells us that the river becomes more efficient as we move downstream therefore the pebbles are eroded and form a round shape and deposited downstream. For Sites 3 and 11 a group failed to gather data on the pebbles therefore both sites were short on ten readings. This is human error which makes it harder for us to analyse and comment on.

I was surprised to find at sites 4&5 there were a few pebbles with a roundness of 0. I believe that this is human error as they might have picked up pebbles that were on the ground than in the river. This of course would mean that they would be less

eroded and maybe considered as anomalies. The erosion (Attrition) on the sediment caused by the river slowly makes he pebbles a round shape. As the mover across the river bed they the friction between the bed and the pebble cause both the river to erode and the pebbles to become rounded.

So as the velocity increases as we move downstream more and more pebbles rub against each other and wear each other down so that they get rounder edges. So there is a link between the increase in velocity and the increase in roundness 4/5.

The roundness total for 5 started off high at the first site and then there was a sudden decrease. Then after that decrease there was a gradual increase in them. This shows that an anomaly occurs at site 1 as there cannot be a very high amount of pebbles there.

Sphericity

From looking at these pie charts There is a gradual decrease in Low sphericity as we move downstream and there is a gradual increase in high Sphericity. This tells me that the river is getting more efficient as we move downstream as there are more pebbles becoming rounder. The increase means that there is more friction between the rocks which is of course caused by an increase in velocity.

The pebbles become rounder as we move downstream because the efficiency of the river increases as we move downstream.

CONCLUSION

By following this investigation I can now answer the two key questions. From the evidence that I have gathered I can now state that the river becomes more efficient as we move downstream. The sediment become smaller and rounded as we move downstream

From my sediment graphs I found out that as we move downstream the roundness becomes smoother which supports my aim and prediction. The pebble got smaller in size as we move further downstream which again proves that the river does become more efficient and the sediment become smaller and rounder. The block bar chart I have drawn is very good in showing so much information in just 1 graph. Again this graph provides me with the evidence I need to prove my predictions.

From my basic observation I have found out that as the river moves downstream it becomes increasingly wider. And the V- shaped valley forms; these are shown in the j. This is as I learnt before the coursework began is cause by the erosion of the bank by the river. The graph of velocity by crossectional area also tells me that the river becomes more efficient as we move downstream because the crossectional area increases as the velocity increases. This is natural as there is more space for the water to travel through. The cross sections also shows the increase in efficiency as we move downstream as I got a few cross section that were of meander shape and meanders only form in the middle section of the river.

Throughout my analysis there is evidence that I have shown next to each graph explaining the different patterns and the sequences that have formed. The geographical background of the topic states that the river becomes more efficient further downstream and sediment becomes smaller and more rounded. This is what I have proved in this investigation by gathering the information and put it into comparable and easily accessible data

EVALUATION

Strengths

Weaknesses

Wider Applications

The most interesting aspect of my study was collecting the data as I thoroughly enjoyed fieldwork.

The most useful aspect of my study was my Analysis as it helped me with my comparisons and helped me to come to a conclusion.

The most rewarding aspect of my study was receiving the results that were geographically correct.

There was only 1 main difficulty that my group came across while collecting the data, We had left half of our equipment at the field centre. This meant that sometimes we had to wait for another group to finish collecting their data so that we could use their equipment. It also made my group work faster which means there could have been a chance of human error.

I think that this project is a snapshot study because I didn't go into full detail with the analysis. We didn't have time to collect a much wider variety of readings.

My results have been successful as they have provided me with the results that are geographically correct. They also support my prediction.

I think that the sample size for both sediment and efficiency was appropriate but I think that while reading the velocity we could have repeated it 3 times and then worked out an average. This is because sometimes there was some leaf litter in the river restricting the cork from flowing with the water.

To extend the study I could have investigated the changes in valley shape. This would have been useful to make a comparison with river efficiency. For velocity we could have taken a reading three times and then worked out an average to get a more accurate reading.

I think that the data I gathered was more than enough to help me investigate the two key questions.

To improve this investigation it would be better if next time all the apparatus was checked before we went out. While testing for velocity the stretch of river tested was cleared of leaf litter.

APPENDIX

BANKFULL

Site No.

Depth 0

Depth 1

Depth 2

Depth 3

Depth 4

Depth 5

Depth 6

0

-0.39

-0.43

-0.44

-0.41

-0.4

0

2

0

-0.05

-0.028

-0.027

-0.031

-0.033

0

3

0

-0.36

-0.34

-0.44

-0.41

-0.43

0

4

0

-0.08

-0.16

-0.24

-0.41

-0.5

0

5

0

-0.21

-0.23

-0.3

-0.55

-0.64

0

This table is for the 5 bankfull measurements taken by my group at each site we visited.

LOWFLOW

Site No.

Depth 0

Depth 1

Depth 2

Depth 3

Depth 4

Depth 5

Depth 6

0

-0.06

-0.065

-0.07

-0.06

-0.05

0

2

0

-0.075

-0.07

-0.085

-0.09

-0.09

0

3

0

-0.14

-0.15

-0.22

-0.18

-0.2

0

4

0

-0.06

-0.1

-0.15

-0.16

-0.16

0

5

0

-0.07

-0.13

-0.22

-0.31

-0.38

0

This is for the 5 low flow measurements taken by my group at each site we visited.

Dis From S

Velocity

50

0.05

540

0.12

640

0.03

770

0.07

800

0.04

810

0.11

910

0.1

060

0.11

100

0.11

200

0.53

360

0.25

This is a table for the graph for Distance from source by velocity.

Channel Roughness

Velocity

0.72

0.05

0.16

0.12

.1

0.03

0.63

0.07

0.75

0.04

0.65

0.11

0.87

0.1

0.4

0.11

0.4

0.11

0.49

0.53

0.1

0.25

This is a table for the graph for channel roughness by velocity.

Dis From S

Gradient

50

0.03

540

0.01

640

0.012

770

0.019

800

0.023

810

0.03

910

0.022

060

0.02

100

0

200

0.022

360

0.022

This is a table for the graph for Distance from source by Gradient

Dis From S

Discharge

50

0.01

540

0.02

640

0.01

770

0.01

800

0.005

810

0.04

910

0.07

060

0.01

100

0.01

200

0.28

360

0.09

This is a table for the graph for Distance from source by Discharge

Shrikrishna Selvaratnarajah 10P Geography Coursework

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