Physical fieldwork

• What is the title of this fieldwork?

  'How does the channel cross profile and velocity of the River Holdford change with distance downstream?'
• What are different types of sampling?

  • Random Sampling
  • Systematic sampling
  • Stratified sampling
  • Bias in sampling
  • Sample size
• What are the positives of primary data collection?

  • reliable
  • accurate
  • up to date
  • able to control collection process
• What are the negatives of primary data collection?

  • time consuming
  • expensive
  • may not be able to carry out a large sample size
• What are the positives of secondary data collection?

  • cost-effective
  • easy to access
  • able to quickly gather large amounts of information
• What are the negatives of secondary data collection?

  • outdated
  • may not be specific to the research
  • unreliable
  • biased
• What was the location of the source?

  a wooded steep valley at Lady's valley
• What were the different risks for this fieldwork?

  • Steep and Rocky footpath
  • Fast river flow
  • Ticks
  • Damage to the environment
• How did we overcome the risks for a steep and rocky footpath?

  • wearing correct footwear
  • walking in groups
  • looking where we walk
• How did we minimise the risk with fast river flow?

  • do not go too deep
  • do not enter fast water
  • carry a throw line
• How did we minimise the risk with ticks?

  • wear repelant
  • fully covered clothing to avoid exposed areas
• How did we minimise the risk with damage to environment?

  • bring back litter to recycle
  • shut gates
  • tread carefully
• What was the secondary research method we used and what was it?

  Location maps- zoom in tool to locate specific locations and use frame tool and textbox to annotate different features present
• What primary research methods did we use?

  • width
  • depth
  • velocity
  • wetted perimeter
  • gradient
  • clast size/shape
• How is the width measured?

  Hold tape measure tight 1 cm above river surface and record the width
• What were the limitations of using the width?

  • Human error
  • undercutting of the banks meant it was difficult to judge the edges of a bank
• How was the depth measured?

  Measure the depth of the river using a meter rule 6 times across the width and work out a mean
• What was a limitation of Depth?

  • human error
  • if high current, splashing may cause inaccurate readings
• How did we measure velocity?

  Put the impeller 1 inch below the surface, switch on the flowmeter, wait 10 secs and record data shown, repeat atleast 3 times and work out a mean
• What was a limitation of using velocity?

  • people in the way may have slowed flow down
  • impeller may not be able to measure sallow areas in the source
  • not checking if the impeller is working correctly
• How did we measure the wetted perimeter?

  one person holds the tape measure at the end, pushing it down to the banks/bed, making sure to include rocks and sediment and record length
• What was a limitation of using the wetted perimeter?

  • human error may not be fully pushed down
  • the WP should always me more than the width
• how did we measure the gradient?

  1. Step 5m apart from eachother
  2. Place climometer near eye
  3. look at other persons eye level and read gradient
• What was a limitation of using the gradient?

  • human error
  • stood further than 5 m, looking at wrong thing, wrong reading
• What are the different data presentation methods we used?

  • Cross sectional area diagrams of 3 sites
  • Work out the mean depth and cross-sectional area
  • A scatter graph to show velocity against distance downstream
  • a dispersion graph for clast size
• How did the depth change with distance downstream?

  Depth increased with distance downstream due to more vertical erosion in the lower course as the river has more energy
• How did the width change with distance downstream?

  width increased with distance due to more lateral erosion happening
• How does the gradient change with distance downstream?

  Decreases as got less steep with distance
• How does the velocity change downstream?

  Increases as less interception with rocks as more sediment as well as a larger volume of water due to multiple tributaries
• How does the clast size change downstream?

  Decreases as more fluvial processes such as erosion mean decrease in the lower course
• What sites were affected by human intervention?

  • Natural debris placed in the river to reduce flooding downstream
  • River made deeper as wider near car park near beach
  • Split up into two channels to go around water treatment park
• How does the channel cross profile and velocity of the River Holford change with distance downstream?

  The cross profile increases, becoming bigger as there is higher vertical and lateral erosion downstream in the upper course, causing deeper depths and wider channels, leading to larger cross sectional area. Furthermore due to multiple tributaries joining into the river, leading to a higher volume of water, leading to an increased velocity downstream. However due to human influence, some anomalies are caused as tree trunks in river reduce risk of flooding and river made narrower in car park near beach.
• How could we extend this study further?

  using both the bradshaw model and the Hjulstrom curve theories to test