Water did not remain level as it splashes and surges depending on the roughness of the bed beneath. Accuracy could be compromised with splash of water as it hits ruler.
1 of 9
Depth
Every 10th of width of river insert ruler (systematic sampling). Measured from bottom of ther iver to surface of water. Ruler rigid so not prone to swaying and fairly accurate up to a mm.
2 of 9
Depth solutions
Get down to eye level, when possible and hold the ruler thin side parallel to direction of flow to minimise splash up.
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Wetted Perimeter
From bank to bank pushing tape measure to to the base of the river in straight line 90 degrees to the channel flow, pushing it up and over obstacles on the bed.
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Wetted perimeter limitations
Impossible to cover accurately the surface of every rock, particularly in the higher
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Wetted perimeter solutions
use a chain as the weight will keep on the bed of the river, but hard to carry
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Velocity
Put hydropop and impeller into the water and time how long it takes for the impeller to reach the end of the hydrpop bar. Can also do it with a dog biscuit
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Velocity Limitations
Stopwatch reading could be slightly inaccurate because of differences in human reaction times. Inaccuracy of reading the impeller as it is underwater and can be difficult to see when it has stopped.
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Velocity Solutions
Difficult except to get a very accurate stopwatch and have the same person using on all the reading points.
9 of 9
Other cards in this set
Card 2
Front
Every 10th of width of river insert ruler (systematic sampling). Measured from bottom of ther iver to surface of water. Ruler rigid so not prone to swaying and fairly accurate up to a mm.
Back
Depth
Card 3
Front
Get down to eye level, when possible and hold the ruler thin side parallel to direction of flow to minimise splash up.
Back
Card 4
Front
From bank to bank pushing tape measure to to the base of the river in straight line 90 degrees to the channel flow, pushing it up and over obstacles on the bed.
Back
Card 5
Front
Impossible to cover accurately the surface of every rock, particularly in the higher
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