Rivers Fieldwork

Aim of investigation

To investigate how river channel characteristics of the River Wey change downstream

Hypothesis- river width

Will increase downstream due to increased volume of water as there are more tributaries . At the mouth all the water from the catchment area is in channel so  more erosion so wider and deeper

Hypothesis- bedload

Becomes smaller and more rounded with increased distance from the source → more erosion downstream

Hypothesis- Velocity

Increases downstream due to less friction, the channel is smaller and shallower so most water is in contact with the sides causing more friction at the upper course

What is the rationale behind the investigation?

Bradshaw Model

What did we do to increase the reliability of velocity method?

Did it 3 times

What did we do to make the width method accurate?

-Pulled the tape measure as taut as possible

- Used a tape measure with smaller increments so it would be precise

What did we do to make the depth more accurate?

• ensured the meter rule was streamlined to the direction of river flow otherwise water would lap against it giving a deeper reading

• meter rule with small increments

What did we do to make the depth more reliable?

Did at 5 different points across the channel

What made the pebble method more reliable

• Took 5 pebbles at each site instead of 3 more than 5 would have also been too excessive

What made the pebble method more accurate?

Used a caliper to measure the long axis

Example of random sampling

Pebbles from a river

Example of Systematic sampling

Took a reading of depth every 10 cm

Why is it important to take a risk assessment before going into the field?

Identify hazards and ensure the appropriate safety measures are in place to prevent accidents or injury

Reasons we chose this location:

• Safe as is a small river

• Close to school

• Accessible

Positives of cross section

• Easy to compare all 4 sites onto one page

• Prove hypothesis easily as you can see if the channel gets wider and deeper

Negatives of Cross section

• Scale is tricky for for the narrower channels

• Graph paper is fiddly and has small squares but big squares would not be accurate enough

Positives of compound bar

• instead of pie chart so no protractor needed

• Compound as % is easier to compare across the sites

• Easy to visually see difference in pebble shape

Strengths of the investigation

• No time constraints so was able to repeat results and get a mean average so more reliable

• Few steep banks so easy to get into to river

Weaknesses of the investigation

• Short river - 8km ( no opportunity to measure more sites)

• Velocity would have been measured more accurately using a flow meter

• Vegetation overgrown at site 1 affecting velocity readings