physical fieldwork 3 Flashcards
where is the River Ogmore ? 4
- in South Wales
- runs from north to south
- source - Ogmore Vale
- mouth - Bristol Channel
what was your hypotheses ?
- velocity increases downstream due to the increased volume of water from tributaries joining, lateral erosion and less friction
- cross sectional areas increases downstream due to vertical and lateral erosion
- the bedload size decreases and becomes more round due to attrition
why did you chose those hypotheses ?
we would be able to see the change easily throughout the course of the river
what secondary data did you use ?
- OS map to see distance downstream
- weather forecast and receding weather
- features affecting discharge
- data collected by other groups in other years
- igeology app on iPads
what primary data did you collect ?
- bedload size
- width
- velocity
- pebble size
how did you collect the width of the river data + and - ?
- tape measure
- hold tape measure from bank to bank
+ easy to read - had to make sure tape measure ends were exactly opposite
how did you collect the depth of the river data + and - ?
- metre stick
- held metre stick in water
+ easy to read - ground was sometimes uneven
how did you collect the cross sectional area of the river data ?
- cross sectional area = width x depth
- measure width and depth
how did you collect the velocity of the river data + and - ?
- use impeller
- held impeller upstream
+ easy to obtain - sometimes didn’t work so had to move position of impeller
how did you collect the river bedload and size data + and - ?
- use callipers
- picked random pebbles with mixed geology and measured them
- used Powers’s visual comparison chart to see how rounded the pebbles were
+ easy to measure and read - slightly bias
what risks did we face ? 5
- drowning
- poisonous plants
- unsanitary water
- trips and slips
- tics
how did we manage those risks ? 5
- no deeper than knee height in water
- don’t eat plants
- don’t drink water
- wear suitable footwear
- check skin for tics
how many sites did we visit, why and how were they chosen ?
- stratified
- 4 sites
- chose areas we expected to see most change
what graphs did we use ? 6
- field sketches
- cross section
- bar charts
- located proportional flow arrows
- scatter graph
- % bar chart
what do you put in your analysis ?
- statistics and data
- how did bedload, cross section and velocity change downstream
- did it follow Bradshaw’s model
- why did the river change this way
how did bedload, cross-sectional area and velocity change downstream ?
- bedload got smaller and more rounded from site 1-4 due to attrition and as velocity increases beload hits each other more often. site 1 mean bedload size was 700.6 mm whereas at site 4 the mean bedload size was 158.7 mm
- cross sectional area increases downstream due to vertical erosion, corrosion and abrasion. site 1 cross sectional area was 0.025 m(squared) site 4 was 1.352 m(squared)
- velocity increases downstream due to tributaries joining the river, less friction and vertical and lateral erosion. Site 1 was 0.12 m/s and site 4 was 0.45 m/s
did it follow Bradshaw’s model ?
yes because
did it follow Bradshaw’s model ?
- yes
- bedload size decreased
- mean velocity increased
- got deeper
- got wider
- cross sectional area increased
what did we conclude ?
that our hypothesis were correct
what do you put in your evaluation ?
- how accurate/reliable our investigation was
- what our sampling methods were
- what were our results
- how we can improve this investigation
how accurate and reliable was our investigation ?
very reliable because we created our own results but referred them to older ones and looked at models which summarise the results we should obtain
what were our sampling methods ?
- random
- systematic
- stratified
how could we improve our investigation ?
be less bias
what was the cross sectional area difference from site 1 to 4 ?
1 - 0.025 m(squared)
4 - 1.352 m(squared)
