Fieldwork Flashcards
What was the aim of our investigation?
To investigate how channel characteristics change downstream along the Glenderaterra Beck, a river running in the valley between Blencathera and Lonscale fell, in the Lake District National Park.
What were our hypothesis?
Discharge would increase downstream and bed load would become smaller and more round
What was the geographical theory behind our investigation?
Brad shore model
- Discharge increases because tributaries add water to the man channel and erosion is increased, to accommodate for this the channel widens and deepens increasing cross sectional area. This makes the river more efficient and increases the hydraulic radius, this results in increased velocity. As discharge is = velocity x area, because the area and velocity are increasing the discharge increases.
- Bed loads gets smaller downstream because there is more attrition, the channel has more energy in the lower course
Hjulstrom curve
- shows the relationship between particle size and river velocity, particles undergo the process of attrition as they are transported downstream
What are the characteristics of the study area?
- 5 miles north of Keswick in the Lake district
- Source at Sinen Gill
- Land use is sheep grazing
- Misfit river as once was a u shaped valley from glaciation, now the river has eroded the bed to become a v-shaped valley
- Little vegetation, quick run off and short lag time
- Skiddaw slates, impermeable rock, quick run off
What are the advantages of the River Glenderaterra Beck as a fieldwork site for our investigation?
- Accessible by foot path from the centre, only 2km to stream order 1
- Order 1,2,3 in short distance of each other, all data will be collected in one day during the same weather conditions
- Each area easily accessed as water levels are low, not very high velocity of water
- Short distance if need help
Describe and explain one method of data collection used
To calculate the discharge we needed to measure both the velocity and cross sectional area.
- Measure the wet width in cm, using a tape measure gold it toght from one side of the bank to the other. It is held tight to ensure accuracy. At some of our sites the bank had been undercut so when measuring the width we went right to the edge of the water
- Wet width is divided by 5 to give a systematic sample, which is not bias
- Depth is recorded at each 5th using a triangular metre ruler, the base of the ruler needs to touch the base of the channel and a triangle ruler is used so the water isn’t affected by a barrier
- average depth x wet width = csa
- then we divided the wet with by 4
- velocity readings were taken at 1/4, 1/2, 3/4
- Velocity reading where taken at 1/3rd depth, constant and accurate and is unlikely to be affected by the bed load - we used a hydro prop with an impellor and times using a stopwatch how long it took for the propeller to reach the stick using this to calculate velocity in m/s - using this method we must ensure that no one is standing in front of the flow of water, however in our investigation there were 4 groups and therefore data may have been affected by other students standing in the river just slightly upstream
- Take an average of velocity x csa will give the discharge for each site
What secondary data did we use?
- Looked at other research on the area in books and online, satellite of the river and the stream orders before we visited
- Whilst at the field studies centre we received information from the experts regarding characteristics of the area and the previous glaciation
What is one method we used for data presentation?
Scatter graphs
- Distance downstream against discharge and for bed load size and distance downstream which showed little correlation
- clear visual representation of relationship
- shows anomalies
- groupings
- we could draw a line of best fit to predict outcomes
- too simple
- doesn’t explain why or give strength of relation - further investigation is needed , leads to a spearman’s rank correlation
What method did we use to analyse our results?
Having identified a correlation between variables using our scatter graphs we were able to perform a spearman’s rank test for correlation
- our results gave us a rs value of 0.951, when we compared this to the critical value it was significant at the 99% significant level, therefore we can conclude that there is a 99% probability that there is a significant relationship between discharge and distance downstream
- good techniques as it allows us to see how strong the correlation between these variables was and makes it easier to compare to other data sets
- however it doesn’t indicate the reason why there is a correlation and during the test it is easier to make a mistake
What are the implications of conclusions for geographers and other intrested parties from our investigation?
- Made me realised that in reality it is more complex than text book theory, other factors in the area lay a huge role
- the model doesn’t fit in terms of the bed load size because of glaciation in the area, till is still being sorted by the river processes
- humans have had an imprint in the area, other student geographers may not put bed load back where they found it - sheep farming, larger rocks moved to allow sheep to cross the stream
- other interested people will include developers over flooding risk especially in the nearby town of Keswick
What were the conclusions to out investigation? How well did they fit our hypothesis?
- Cross sectional area calculated by width x depth increased downstream so fits with the brad shore model due to the increase of the volume of water, averages at site 1 was 0.13m2, site 2 0.37m2 and site 3 was 0.91m2
- velocity increased from 0.14m/s at site one, to 0.29m/s at site 2 and 0.40m/s at site 3
Therefore because the csa and the velocity increased downstream so did the discharge. The averages of the 4 groups were 0.019 cumecs at site 1, 0.104 cumecs at site 2 and 0.376 at site 3. As expected discharge increased because of the increase in the volume of water, the speed of water and the erosion and widening of the channel further downstream. - Bed load shape and roundness varied at our sites where the biggest pieces of sediment were at site 2 rather than site 3. This may be due to the fact that there had been bad weather in the area a few days before which may have caused the rocks to be transported from site 1 area. it may also have been affected by previous students who may not have returned the bed load back where they found it. Glaciation in the area also has a lasting effect on the river as its still sorting the till.
What were the risks associated with our investigation? How could we reduce them?
Rocks and debris - could cause tripping or falling, we could avoid the are but this may mean that we wouldn’t be able to visit the intended area
Weather (extremes) cold can cause hypothermia - we ensured that we were wearing the right equipment and carrying warm clothes and a warm drink - this may make the investigation longer
Steep surfaces - risk of slipping - made sure we stayed on the footpath and wore correct footwear - extra time is needed to plan the route
wildlife - sheep - intended sit may be on permissive land
What are the limitations to our investigation?
- we didn’t investigate as far as stream order 4 and 5, not really possible - or up as far as being right at the source
- data for bed load may be effected by other students form our own group and from other schools their before us
How can the results to our fieldwork investigation be improved?
- Repeat on a different day/ season when there has been different weather conditions
- Repeat in similar valleys
- Investigate further downstream at orders 4 and 5
