Cowside Beck Flashcards
On the Bradshaw’s model, what increases with distance downstream?
discharge, occupied channel width, channel depth, velocity, and load quantity
On the Bradshaw’s model, what decreases with distance downstream?
load particle size, channel bed roughness, slope angle
Aim of fieldwork
To investigate how applicable the Bradshaw Model is to a stretch of Cowside Beck
Hypothesis
Discharge will increase with distance downstream
Location
- Cowside Beck, Arncliffe
- Flows north east to confluence with the Skirfare
- Skirfare is tributary to the River Wharfe
Why did we select Cowside Beck?
- upland stream
- exhibits majority of changes over short distance
- deep enough to allow measurements without being excessively deep/wide
- could access enough sites for systematic sampling
- scree slopes common so affected bedload size and shape :(
Secondary Data
OS map to locate and plot 9 sites
ICT skills used (secondary data)
- digital OS map to explore changes in valley cross-profile and channel
- weather forecast online
How long was the sample site?
5km
*long enough to expect to see recognisable changes
How far apart were the sites?
500m
What type of sampling was used?
systematic
Why was this sampling technique used?
Gave us good coverage of the beck
Allowed us a statistically significant amount of sites
What needed to be considered when the sites were chosen?
Access and safety
Why didn’t we use random sampling?
We wanted to cover all sections of the river, and this may not have occurred if random was used
Access needed to be considered
Improvement to sampling technique?
Stratified sampling would have allowed two different sites to be compared, and could be paired with random and systematic within the chosen sites
How did we measure depth?
- ran tape measure along river from bank to bank (ensuring it was tight and horizontal)
- divided river into 10
- measured depth at each interval using meter ruler
- recorded results
How did we measure X-Sectional Area?
Multiplied average depth of channel by width
How did we measure river velocity?
- used a biodegradable float (orange)
- measured 10 m stretch of river
- timed how long it took the orange to travel the distance
- done at each bank and in middle
- found average time and converted it into ms-1
- took measurements using a flow meter
Health and Safety
- weather - appropriate clothing needed
- cold, fast flowing water - river levels monitored, told not to go too deep
- bank conditions - overhanging banks collapse easily
- getting lost - kept to designated areas, registers taken, worked in groups
- uneven terrain - good footwear
Presenting Depth and Width of the river
We drew the cross section onto graph paper
scale 2cm=1m. This made explaining results easier.
Measuring river discharge
multiplied average velocity by cross sectional area
Site 9 Mean velocity
1.1 ms-1
Site 9 X sectional area
1.85 m2
Site 9 discharge
2.035 cumecs
