Rivers Fieldwork Flashcards
1
Q
What is the Bradshaw model?
A
Increases downstream:
Discharge
Channel width
Depth
Velocity
Load quantity
Decreases downstream:
Load particle size
Channel bed roughness
Gradient
2
Q
How to choose a site for fieldwork?
A
- not an area where the river flows too fast or deep
- accessibility
- distance between sites/evenly spaced/spread out
- away from human activity (dams, weirs)
- permission from landowner is on private land
- avoid areas of pollution
3
Q
How to measure gradient of river?
A
- Measure a 10 meter stretch of river using a measuring tape
- Two people hold 2 ranging poles at each end of the 10 meters
- Another person stands next to the top pole and use the clinometer to measure the angle of gradient, making sure that it is aligned with the corresponding part of the other pole.
- Repeat twice more and calculate an average
- Record results
4
Q
How to measure the cross section of the channel?
A
- Measure the width at water surface using a measuring tape
- Put metre sticks at either end of the bank and keep tape measure stretched and taut
- Divide the width by 4 and this will give you the 3 intervals to measure depth at
- To work out the cross section, multiply the width by the average depth
5
Q
How the measure wetted perimeter?
A
- Use a long chain to measure the stream bed
- Make sure to go over the top of rock and stones
- Measure this at the same place as the width
- Feed the chain and a measuring tape through your hands at the same time to measure the length of the wet section.
6
Q
How to measure surface velocity?
A
- Measure 10 metres along the river
- Put a float (dog biscuit, orange) at start of 10 meters
- Start stopwatch when the float is put in the water
- Time how long it takes to travel 10 metres
- Repeat twice and calculate an average
- Calculate speed by using speed=distance/time
7
Q
How to measure river discharge?
A
Q = A x V
Where Q = discharge (m^3/sec)
A = cross sectional area (m^2)
V = (m/sec)
