Epping Forest

• What was the enquiry question?

  How do river characteristics change with distance downstream along Loughton Brook?
• How did we choose our sites?

  We choose 3 sites, one in each course. (Upper, middle, lower)
• why did we use stratified sampling?

  Because Stratified is choosing one at each course that is save and accessible
• Which secondary data did we use?

  
  

  1. Geology map- showing rock types
  2. environment agency flood risk map.
• Explain a quantitive ,method of data collection to measure river discharge.

  We measured the river discharge through width depth and velocity.
• How did we measure the depth?

  depth= measured 1/4, 1/2, 3/4 between river banks. We used a ruler because it is stable. We then took a mean of all the depths we had measured to improve the reliability of the results
• How did we measure the width?

  we used a measuring tape. We pulled it taut.
• How did we measure the velocity?

  We used a cork, stopwatch and the ruler. Someone threw in the cork, there was a metre ruler on the bank, as soon as the cork reached the start metre ruler someone pressed start on the stop watch. When the cork reached the end the time was stopped.
• Explain a qualitative method of data collection to record the river landforms that make up the landscapes.

  Field Sketch. This helped to see the different valley shapes and landforms.
• Give an advantage and disadvantage of a method of data presentation

  the line graph was clearly shows the trend. The line graph doesn't show the fluctuations. The line Graph is suitable for continuous data
• River discharge formula


  river discharge = CA = w*d

  Cross Area times average velocity
• Why might our conclusion be unreliable

  • Different people have different reaction times
  • People throw in the cork with quite a lot of force
  • The river bed was soft, so it was hard to know how far to push the stitch down.
  • we only visited three sites, so it might not be representative of the overall trend
• Reasons why parts of Loughton Brook's floodplain are at high risk of flooding

  • Steep slopes
  • Small drainage basin size
  • Urbanisation
• Most of Loughton Brook's drainage basin is categorised as low risk
• Reasons why most of Loughton Brook's drainage basin is low risk

  • Many trees to intercept rainfall
  • Very few properties in the forested area
• Loughton has many flood management strategies including a small reservoir, channelisation, flood plain zoning and washlands
• Quantitative fieldwork method used

  Measure river width, depth and velocity to calculate river discharge
• Stratified sampling

  Choosing a safe, accessible site at the upper course, middle course and lower course of Loughton Brook
• Random sampling or systematic sampling would have been less suitable than stratified sampling
• Measuring river width

  Use a measuring tape held taut between the water's edge on either side of the river
• Measuring river depth


  Use a metre ruler at 1⁄4, ½,and 3⁄4 between the river banks, take multiple measurements and calculate the mean
• Measuring river velocity


  Use a cork, metre ruler and stopwatch to time the cork travelling 1 m
• The cork was a suitable piece of equipment because it is small, light and biodegradable
• Qualitative fieldwork method used

  Completing an annotated field sketch using SNOTT (Scale, Notes, Orientation, Title, Time and date)
• Collating and analysing the data

  1. Recorded widths, depths and velocities collated in Excel

  2. Calculated mean results to improve reliability

  3. Calculated velocity and discharge using formulae

  4. Plotted mean discharge on a line graph to show the overall trend
• The line graph could be misleading as it shows values between each site that were not directly measured
• As the river moves downstream

  • Discharge increases slowly at first, then rapidly
  • River becomes wider and deeper
  • River begins to meander
  • River valley becomes flatter
• Reasons for increasing discharge downstream include water joining from tributaries and surface runoff, especially if the geology is impermeable
• Increasing discharge and velocity

  Provides more energy for the river to erode laterally and vertically
• Erosion processes

  • Abrasion (pebbles knocking against banks and bed)
  • Hydraulic action (fast-flowing water forcing into cracks)
• As the river moves downstream


  It becomes more efficient at overcoming friction, so velocity increases
• Approximately 95% of a river's energy is lost to friction under normal flow conditions
• The field sketches confirmed that Loughton Brook became wider and deeper with distance downstream, and began to meander in the middle course