River Holford - FIELDWORK

Question 1

Where is the River Holford located?

Source/mouth?

Answer 1

Somerset, Nettlecombe.
Source - Lady Fountain’s Spring.
Mouth - Kilve Beach.

Question 2

Why was the River Holford chosen as the location? 6

Answer 2

1. 7km long - easy and accessible.
2. Walkable within a day - antecedent conditions reduced.
3. Risk assessed; safe to walk.
4. Shows different geology; Mercian mudstone - impermeable, Jurassic limestone and sandstone - permeable.
5. Gradient - shows upper, middle and lower courses.
6. Landuses - urbanisation and deciduous forests.

Question 3

What was the aim of the River Holford investigation?

Answer 3

How and why do channel characteristics change from the source at Lady Fountain’s Spring, to the mouth at Kilve Beach, along the River Holford in the Quantock Hills, Somerset?

Question 4

How was the investigation of the River Holford risk assessed? 7

Answer 4

1. Groups of 4 - in the event of an accident, the safety of the group wouldn’t be compromised.
2. Never stray from other groups - help always within reach.
3. Stay away from steep slopes to avoid slipping - particularly near Lady Fountain’s Spring.
4. Avoid deep water - never above wellington height - less risk of hypothermia.
5. Sensible behaviour to ensure instructions are heard.
6. Appropriate clothing - reduces hypothermia and tick risk - avoid Lyme’s disease.
7. Clean hands; use hand sanitizer to avoid Weil’s disease.

Question 5

What are the 7 hypothesis’ used to investigate the River Holford?

Answer 5

1. Discharge increases from source to mouth.
2. Width increases from source to mouth.
3. Velocity increases from source to mouth,
4. Depth increases from source to mouth.
5. Gradient decreases from source to mouth.
6. Bedload size decreases from source to mouth.
7. Bedload becomes smoother from source to mouth.

Question 6

What do all the hypothesis’ relate to?

Answer 6

Bradshaw’s model.
It shows that discharge, occupied channel width, channel depth and average load quantity increases downstream.
We wanted to test this.

Question 7

How did we measure the velocity of the River Holford?

- PRIMARY DATA COLLECTION

Answer 7

1. Stratified sampling - we chose 7 sites.
2. Measured the width from bank to bank using a tape measure in metres.
3. Divided the width by 3 to find 3 specific places - systematic sampling.
4. The hydroprop and impeller was held just under the water to measure the highest velocity at each point.
5. Another person timed it using a stopwatch in seconds.
6. A formula was used on the computer to work out the velocity per second, and later the discharge.

Question 8

What does reliability of the primary data collection mean?

Answer 8

How well the data reflects the River Holford.

Question 9

What does the accuracy of the primary data collection mean?

Answer 9

How well the data was collected.

Question 10

What were the limitations of the velocity primary data collection? 6

Answer 10

1. Reliability questioned - only 7 sites used.
2. Width readings could be measured due to the flow of the water caught on the tape - could increase reading.
3. Inaccurate measurements due to the hydroprop movements e.g. leaf stuck in the impeller could reduce the velocity.
4. Influence of the bedload could reduce velocity due to friction.
5. People upstream cause friction - slowed down velocity.
6. Inaccurate stopwatch timings - between calling start/stop and actually pressing the stopwatch decreases the velocity reading.

Question 11

What secondary data was used to investigate the River Holford?

Answer 11

1. Textbooks - Barker or Smith’s AQA books.
2. Bradshaw model - based on a number of different rivers under different conditions.
3. Met office/weather - shows the relationship between rainfall and discharge/antecedent conditions.
4. Geology map - needed to explain discharge and permeable/impermeable rocks.
5. OS maps - needed to locate the area and determine sites e.g. tributary meets at the River Holford.
6. Results used from existing data collection could be used to increase sample size.

Question 12

How was technology used to help investigate the River Holford? 7

Answer 12

1. GIS - can overlay geology and river data from OS maps.
2. Google earth - determined the sites.
3. Microsoft excel - for calculations.
4. GPS - carried by tutor.
5. Digital camera - for photographic annotations.
6. Multimaps - OS maps.
7. Met check office data bases - check for antecedent conditions.

Question 13

What were the results for the discharge of the River Holford for sites 1-7?

Answer 13

1. 0.01m/sec
2. 0.01m/sec
3. 0.02m/sec
4. 0.10m/sec
5. 0.58m/sec
6. 0.52m/sec
7. 0.64m/sec

Question 14

What was the anomaly for the discharge results and what could this be due to?

Answer 14

Site 5 - 0.58m/sec.
This could be due to urbanisation - Holford Village.
Impermeable surfaces increases runoff and therefore discharge.

Question 15

How was a scatter graph used to show the results of the primary data collection? 5

Answer 15

1. X axis - independent variable - distance.
2. Y axis - dependent variable - discharge.
3. Plotted the 7 points.
4. Drew a line of best fit to show a strong positive correlation.
5. Identified the anomaly - site 5 - 0.58m/sec.

Question 16

What are the advantages of using a scatter graph to present the primary collection data? 7

Answer 16

1. Identifies a trend.
2. Direction of the relationship is identified.
3. Easy to interpret.
4. Can identify anomalies.
5. Data lends itself to a non-spatial technique and ICT use.
6. Data was quantitative.
7. Doesn’t give a relationship strength; lends itself to further analysis - SPEARMAN’S RANK.

Question 17

What was the result of the Spearman’s rank analysis of the discharge primary collection data?

Answer 17

0.96
The 99% critical value was 0.929
I can reject the null hypothesis.
There is a strong positive correlation between the discharge and distance.

Question 18

Why was Spearman’s rank used? 3

Answer 18

1. It shows a statistically significant relationship between the discharge and distance from the source at the 99% critical level - there is only a 1% chance that the result was due to chance.
2. It includes 7 ranked pieces of data.
3. It determines how strong the correlation is.

Question 19

What are some conclusions for the investigation of the River Holford? 4

Answer 19

1. That the discharge increased from source to mouth e.g. site 1 - 0.01m/sec and site 7 - 0.64m/sec
2. That Bradshaw’s model was correct - that velocity, depth and discharge increased from source to mouth.
3. Decrease in bedload from source to mouth.
4. Increase in lateral erosion at the mouth.
   - All findings were supported by Spearman’s rank at the 99% critical value.

Question 20

What were the advantages of using a hydroprop/impeller? 5

Answer 20

1. Easy to use.
2. Adaptable for more measurement at different depths.
3. Repeatable.
4. Point specific.
5. Lightweight and easy to carry.

Question 21

What are the disadvantages of using a scatter graph to show the primary data collection?

Answer 21

1. The graph can be affected by large amounts of skewed data.
2. Can become easily cluttered - hard to read.

Question 22

How can the whole investigation of the River Holford be improved? 5

Answer 22

1. Increasing the number of sites investigated e.g. there were restrictions due to land use.
2. Collect more data to increase the sample size for reliability.
3. Use an automatic water flow meter - impeller often got stuck.
4. Eliminate more human error - ensure the river isn’t blocked by people.
5. Consider looking at more than one river to compare.

Question 23

How would this investigation of the River Holford be useful to others? 4

Answer 23

1. Data could be used as secondary data.
2. Data was useful as proved Bradshaw correct.
3. Environmental Agency might want it e.g people investigating Bradshaw model.
4. If somebody else was investigating another river and wanted to compare them.

Question 24

What went well regarding the investigation of the River Holford? 7

Answer 24

1. Done in one day (reliable).
2. Collected lots of bedload data.
3. Specific sites were used to collect data.
4. 4 groups = 4 sets of data (averages could be calculated and anomalies found).
5. Enough data to complete statistical techniques.
6. Methods were easy to do and pick up.
7. Drainage basin features were covered, e.g. geology and human activity.