Geography - sampling the river holford
- Created by: Katy Matey
- Created on: 11-06-18 18:49
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- Sampling the river Holford
- Sampling strategies
- Random = Randomly choosing points
- Stratisfied= We select points which are in different groups eg/ types of rock
- Systematic = Where points are chosen based off a system eg/ every km along
- Opportunity= We sample wherever we can eg/ safe areas
- We measured the velocity at a variety of locations
- Why?
- We needed to see how it varied at different locations + how it was influenced by different factors
- How?
- We used a flowmeter to measure the water speed in m/s
- You face the oncoming flow
- You face the oncoming flow
- We did it 3 times for validity at equal spaces across the channel
- The systematic sampling of the width reduces bias
- The systematic sampling of the width reduces bias
- We used a stopwatch to measure time taken for the impeller to spin along the thread
- We used a flowmeter to measure the water speed in m/s
- Evaluation
- It didn't function as well in slow/ shallow water
- It got stuck
- Stopwatch= human error
- we could increase the number of measurements across
- Could repeat + measure in different depths
- Quite accurate; better than floating object
- Why?
- We measured the channel shapes -- width, depth and wetted perimeter
- Why?
- To calculate the efficiency, using hydraulic radius. This shows whether it influenced velocity
- How
- For the depth we used a meter ruler at 7 spaces across the channel
- For the width + wetted perimeter we used a tape measure across the channel and the banks
- This is a systematic way of sampling
- Evaluate
- Take more depth measurements to show how the shape varied
- Human errors
- water height varied whilst measuring
- generally accurate
- Why?
- We measured the gradient
- Why?
- To see if it affected velocity
- How?
- We used a clinometer -- this showed the slop angle in degrees between 2 points
- We measured it from 5m apart in the river
- Evaluate
- May not have pointed at the same height -- human
- Should be further apart
- Why?
- Secondary Data we used
- We used secondary data such as OS maps and British geology maps
- We used secondary data because we wanted to find out about different rock types as well as the overall height of the land and the location
- Sampling strategies
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