Skills - Hypotheses/Methods Flashcards
Hypotheses
3
Hypotheses
Velocity up as move downstream
|_> geometry channel wider/less friction - efficiency up
Sed shape rounder as move downstream
|_> longer exposure to erosive processes
Sed shape down as move downstream
|_> longer exposure to erosive processes
Methods
Velocity
Methods
Impellar (3 equal intervals)
Width (tape measure) - pragmatic
Depth (5 reading, metre rule) - linear systemat.
Wetted perimeter (long tape measure)
Gradient (automated level)
Methods
Sed shape
Methods
5 samples where metre rule touched (depth measurement) - linear systematic
Powers index
Methods
Sed size
Methods
5 samples where metre rule touched (depth measurement) -linear systematic
Wooden calliper (length, bredth, width)
Why Holford
Why Holford
4.2 km long (good size for time and representative data)
Remote (lack of human influence as measuring physical processes)
Generally shallow enough (safe)
Why Holford
How make better?
Why Holford
Had to sample pragmatically (access/footpaths)
Add site near mouth (not enough to gain effective stat. testing)
Increase amount of time
Better time of year (weather/time)
Positives for methods
Velocity
Reliable equipment (better dog biscuits)
Calculated ave. (overcame x-channel changes from thalweg)
Improve methods
Velocity
Improve methods
Impellar struggled (too shallow) - had to tap
Take more measurements at different depths (if more time)
Improve methods
Channel Geometry
Improve methods
Width - more readings and tape had to be taught (localised winds)
Wetted perimeter - chains
Positives for methods
Gradient
NO NEED TO IMPROVE!!!
Positives for methods
Pragmatically sampled by teachers (automated level)
Positives for methods
Sediment shape
Sediment size
Positives for methods
Other groups data used (enlarge sample size/more representative)
Wooden calliper used for size
Powers index for shape (same person used)
Improve methods
Sediment shape
Sediment size
Improve methods
Tendency to select largest/easiest to retrieve
Rushed (weather/boredom)
Pebble shape subjective (bad to share results)
Larger sample (more than 5)
Use random stratified (6 numbers com gen 0-100)
Limitations
5
Limitations
Other people
Time/Weather
Accessibility
Sampling methods
Limitations
Time/Weather
Limitations
7 hours (10am-5pm)
Exteremely cold and heavy rain
January (dark early) - rain also limit visibility
|_> collection rushed (no site 7)
Limitations
Sampling methods/Accessibility
Limitations
Pragmatically selected (systematic not possible) due to:
- steep banks
- private property
- heavy equipment (automated level) restricted site choice
- sites spaced irregularly (1-3 bunched ang 5-6 1.9km gap)
