fieldwork - river holford Flashcards
what is the title of our physical fieldwork?
Exploring downstream changes along the River Holford
benefits of the location
- river had footpaths = safe and accesible
- accesible car park
- only 7km long = we could evaluarte parts of the whole river in aday
- river showed obvious changes
- previous schools studies here = so we knew it was safe and legal to do
name 2 risks and ways to prevent them:
- slipping/tripping - wear appropiate footwear, dont run
- drowning - avoid deep fast flowing water
whats the geographical theory?
BRADSHAW MODEL
- discharge increases downstream as tribatries join
- velocity increases as there is larger for veloicity of water = more energy & less friction as chanell widens and deepens
hypothesis
- discharge will increase as we move downstream
- velocity will increase as we move downstream
- cross section area will increase as we move downstream
what sampling method did we use?
**stratified **
- measuring after tributries
- helped us asses reasons for inc discharge
- sites also chosen based on accessibilty and safety
explain the qualitve method used?
- we used a field sketch/photo and annotated it to higlight key features e.g gradient, pebble size
- helpes to understand subjective elements of each site
explain quantative method
- cross sectional area
- we used a tape measure to measure the width of the wetted edges [stratfied]
- then divided the width by 10 and used a meter ruler to measure the depth at all 10 points [thin end faced up stream]
- then used 2 measurements to calc cross sectional area
=sytematic
explain quantative method 2 [systematic]
- velocity
- at each site we measured the width w a tape measure and divided it by 3
- at each point used a** flow meter **and timed how long it took the impellor to reach the bottom
- then worked out the mean velocity from 3 readings
secondary data used ?
- geology maps to work out geology of area
- google maps = to identify safe acsess points
how did we present our data
- line graph
- plot the change discharge against distance downstream [continous data]
- see data, patterns & anomlies clearly
how was GIS used
- to locate our velocity data onto a map = so we could visually see the change in velocity
- with proportional symbols
what did our results show?
example
as we travelled downstream the discharge, cross sectional area and velocity increased
e.g
avergae width ic from 40cm to 210cm
[site 1 to site 5]
how reliable were our results
- in fast flowing parts = hard to keep tape measure taut may have impacted reading
- identifying the wetted bank = subjective
- only took data from 1 day = so the wind direction and weather may of impacted results
what improvements could be made?
- larger sample size
- gone at different times of year
- use a dif technique for velocity w low flow
- we could of ensured our ruler was facing thin end upstream when measuring depth = inc the accuracy
analysis
- data of discharge filles into table then a line graph where line of best fit was added [show clear positive trend]
- then looked alongside photos = visyual representation of change
- to make analysis more accurate our results were compaed w other groups = larger sampling size
- & compared w previous year to see if patterns were reliable
conclusions
- can conclude as we travel downstream discharge, volume, cross sectioanl area increased = supporting Bradshaw model
- accurate:
- used technical equipment like a flowmetre but human error may have reduced accuracy
- line of best fit showed few anomlies & strong positive correlation between discharge and distance = can trust our results
accuracy
issues:
- river was flowing to quickly in some places = difficult to hold tape measure taut may have impacted width reading
- indetfying the wetter back was subjective accuracy ,ay have been reduced [diff readings]
- velocity reading some places flow was to slow impellor dindt move so we simply registered 300 seconds
evaluation
- overall are conclusions were valid:
- measured velocty 3 times and took an average
- same persons identifies wetter bank to inc accuracy
- compared our results to other groups = larger sample size and inc accuracy
- tape measure wasnt always taut reducing accuracy
how could a systemic sampling stagey be used?
- we could of taken mesurements every 1km
= less bias, shows change over distance
