Hypothesis

I think that the velocity of the water will increase steadily as we go down stream. This is because at site one the river shouldn’t be very wide and deep, so the velocity will be slow as there will be more friction, as you go down stream the river should get wider and deeper so there will be less friction increasing therefore increasing the speed of the river.

Method

To measure the velocity of a river I will need to:

a. Measure out a 10m stretch of river,

b. At the beginning of the 10cm I will drop the cork into the river and start the stopwatch,

c. When the cork reaches the end of the 10cm stretch I will stop the stopwatch and collect the cork.

d. I will then repeat steps b and c a further, two times.

e. I will then average out the three speeds.

f. Once I have the results I will use the following equation to work out the speed of the river:

Stretch of river = speed in metres per second

Average time in cork

I will repeat the steps a to f at each site.

Results

Velocity

Site one

Site two

Site three

1st cork

75.92 secs

18.98 secs

33.90 secs

2nd Cork

82.26 secs

21.46 secs

31.90 secs

3rd cork

50. 30 secs

22.93 secs

32.83 secs

Average Cork

69.49 secs

21.12 secs

32.54 secs

Speed of river

0.14 m/s

0.47 m/s

0.31 m/s

Conclusion

From the results, you can see that a site one the river was flowing at the slowest speed, at site two it was fastest and site three was in between the both. This did not match my hypothesis that was because the velocity at site two was measured on a bend so the water travels faster.

The method used to find the velocity of the river was not very accurate because, the cork kept getting stuck in the weeds, so the results showed it took at longer time than it actually did.

Pebble Roundness

Hypothesis

I predict that the further down stream you go the less angular the stones will be, this may be because the further down stream you go the greater the velocity and the greater the velocity the faster the stones travel, and the more they knock against the sides and bed of the river, therefore eroding the edges of the stones.

Method

To find pebble roundness, I will need to:

a. Select ten pebbles at random from the bottom of the river.

b. I will then select how round the pebble is using the table below.

c. I will then need to find the:

Mode ~ most frequent

Median ~ the number in the middle when all the numbers are wrote out numerically.

Mean ~ the average

Class 1

Class 2

Class 3

Class 4

Class 5

Class 6

Very Angular

Angular

Sub- Angular

Sub-rounded

Rounded

Well Rounded

I will repeat this for all the sites.

Results

No

Roundness

1

1

2

1

3

1

4

3

5

2

6

2

7

2

8

2

9

3

10

3

Mode

2

Median

2

Mean

2

No

Roundness

1

2

2

4

3

3

4

2

5

1

6

3

7

2

8

3

9

2

10

2

Mode

2

Median

2

Mean

2.4

No

Roundness

1

4

2

4

3

4

4

3

5

3

6

2

7

3

8

2

9

4

10

5

Mode

4

Median

3.5

Mean

3.4

Conclusion

The results back up my hypothesis, the further down the stream we went, the rounder the stones became this was due to the increase of velocity the further down stream you went which lead to the increase of friction therefore the more erosion which leads to rounder stones.

This experiment wasn’t very accurate as you may have picked out 10 sharp stones, you could make this experiment more accurate by picking out more stones, and then finding the average.

Cross-Sectional Area

Hypothesis

I think the cross sectional area will start off small and increase as you go down stream, this is because as you go down stream more water joins the river making it wider and therefore increasing the cross-sectional area.

Method

To find the cross-sectional area I will need to find the width and depth of the river. To do this I will:

a. Width: I will measure across the top of the water between the two banks

b. Depth: I will then take the depth at 10 equal intervals across the river. Once I have the information, I will average out the depth.

c. Once I have the depth I will use the following equation to workout the cross-sectional area:

Width (in metres) X av depth (in metres) = Cross-sectional area

Results

Site One

Site Two

Site Three

Width

0.55 m

1.26m

2.20m

Depth

0.08m

0.09m

0.1m

Cross-sectional area

0.04m

0.12m

0.21m

Conclusion

My hypothesis was correct the further downstream we went the greater the cross-sectional area became.

Measuring the width and depth a couple more times in the same area, then finding the average could have improved the experiment.

Discharge

Hypothesis

I think the discharge will increase the further down stream you go, this is because there is more water in the river the further down stream you go, increasing velocity. The width also increases due to more water entering the river from streams, this increases the cross-sectional area, and therefore there is more discharge. (The more water in the river, the more discharge there is likely to be)

Method

To measure the discharge I will need to take the results from the velocity and cross-sectional area and use the following equation:

Velocity X cross-sectional = discharge

I will repeat this an each site.

Results

Site One

Site Two

Site Three

Velocity

0.14 m/s

0.47 m/s

0.31 m/s

Cross-sectional area

0.04m

0.12m

0.21m

Discharge

0.0056 cumecs

0.06 cumecs

0.07 cumecs

Conclusion

My hypothesis was correct the further down the stream we travelled the greater the discharge; this was due to the increase in amount of water in the river.

The method was an accurate way of collecting data to find out discharge.

Valley Side Slopes

Hypothesis

I think that the further down stream you go the less sloped the valley side gets this is because at the beginning of source of a river the slopes are very mountainous and as you go downstream the area becomes less mountainous therefore the slopes are smaller.

Method

To find the valley side slopes I will need to:

a. Place a pole at the bottom of the river a further 10m upstream I will place another pole.

b. I will then place the clinometer onto the pole and look through up

c. I will line the clinometer up with the other pole and record the reading

d. I will then move the first pole a further 10m from the second and repeat step c.

I will then repeat this for the other sites.

Results

Site One ~Left side (in degrees)

Site one ~ Right side (in degrees)

Site three ~ Left side (in degrees)

5m ~ 15

5m ~ 7

5m ~ 18

10m ~ 5

10m ~ 15

10m ~ 6

15m ~ 5

15m ~ 16

15m ~ 3

20m ~ 7

20m ~ 11

20m ~ 4

25m~ 4

25m ~ 5

25m ~ 4

30m ~ 3

30m ~ 2

30m ~ 5

Conclusion

My results agreed with my hypothesis, the valley side slope did decrease. However, we could not get a reading for site two as there was a fence obstructing the way, and a road blocked the right side of sight three.

This is a good way to measure valley side slop however things such as fences may obstruct the way.

Channel Width and Depth

Hypothesis

The further down stream you go the wider and deeper the stream gets. This should be because the further down stream you go the more water there is in it because of small streams joining to it, this means there’s more erosion which means the stream gets wider and deeper.

Method

To find the width and depth of the channel I will need to:

a. Width: I will measure across the top of the water between the two banks

b. Depth: I will then take the depth at 10 equal intervals across the river. Once I have the information, I will average out the depth.

Results

Site One

Site Two

Site Three

Width

0.55m

1.26m

2.20m

Average Depth

0.08m

0.09m

0.09m

Conclusion

My hypothesis results didn’t match my hypothesis as site two and site three had the same depths this was because site 2 was on a bend so the water on the bend would have been deeper making the average depth higher.

This was not a totally accurate way of collecting data as bends may affect the results also the river could have changed without you realising if your interval between measurements was large. You could improve this by taking measurements more frequently.

Geography Field Trip:

Rivers

By: Rebecca Roberts 10x

Introduction

In October, we went to Snipedales, to collect information about rivers. With the information we have collected, I have been able to work out the following at three different sites:

River Velocity

Cross-sectional area

Discharge

Pebble Roundness

Valley side slopes

Channel Width and Depth

With the information, we have found out with have been able to get a better view on the way a river changes as it goes down stream.