River Fieldwork: Methods (Edexcel GCSE Geography A)

River Fieldwork Methods

Data Collection Methods

• The data collection methods will depend on the aims/hypothesis of the fieldwork

• The starting point with most river fieldwork is to measure the width and depth

• Data collection should include both quantitative and qualitative methods

• The collection of quantitative data can be completed in several ways in a river study

Quantitative data collection

Width

• The measurement of width is taken where the water surface comes into contact with the river banks.

Measurement of River Width

• To take an accurate measurement:

  • Measure from the point where the dry bank meets the water on one side to the point where the dry bank meets the water on the opposite side

  • Ensure that the tape is held taut and does not touch the water this could affect the reliability of the data

Depth

• The measurement of depth should be completed at regular intervals across the width

• This ensures a full picture of the changes in depth across the whole channel width is recorded

• It also allows a mean depth to be calculated to use in the calculation of river discharge

Depth Measurements 

• To take an accurate depth measurement:

  • Work out the distance apart each depth measurement needs to be 

  • Place a meter rule into the water at the correct point

  • Ensure the meter rule is placed sideways with the flat side facing the banks: this reduces any impact on the water height ensuring more accurate measurements 

  • Record the distance from the bed to the surface of the water

  • Repeat this across the width of the river

Velocity

• The velocity is the speed at which the river flows

• This can vary across the channel width as well as along the course of the river so velocity should be recorded in three positions: towards the left bank, centre and towards the right bank

Positions in River Channel for Velocity Measurements

• Using a flow meter velocity can be easily measured by:

  • Taking readings at three equal distances across the river width 

  • Placing the flow meter into the water at least 3cm below the surface

  • Three readings should be taken at each of the three places across the channel to allow the calculation of a mean

• To take an accurate measurement using a float:

  • Measure a set distance upstream - for example, 10 meters

  • Drop a float at the start of the 10 meters

  • Time how long it takes for the float to travel the distance using a stopwatch

  • Repeat at each position three times to allow the calculation of a mean

Discharge

• The discharge of the river is calculated rather than measured

• The first step is to calculate the cross-sectional area: 

  • Cross-sectional area (m²) = width (m) x mean depth (m)

• The second step is to calculate the velocity:

  • If a flow meter the mean velocity should be calculated by adding the velocity measurements and dividing by the number of measurements

  • If a float has been used and a distance of 10m then the meantime should be divided by 10 to calculate the time taken to travel 1m

  • Discharge (m³/s) = cross-sectional area (m²) x velocity (m/s)

Gradient

• As it moves downstream rivers decrease in height

  • This is the gradient of the river

• The gradient is measured over a 10 meter stretch of river with a ranging pole placed at 0m and another clinometer at 10 meters

• A clinometer is then used to measure the difference in height between the two poles

Measuring gradient using a clinometer

Qualitative data collection

Photographs and Field Sketches

• Photographs and field sketches are qualitative data 

• Just as with any data collection and presentation they have strengths and weaknesses

• In a river enquiry photographs and field sketches can be used to show landforms and particular features such as bed load

• Photographs are also ideal for illustrating the data collection methods used

River Enquiry Data Presentation

• Data presentation can take many forms

Primary Data

• Much of the primary data collected in a river enquiry will be presented in the form of a graphs 

  • Each type of graph is suitable for particular data sets

  • The graphs also may have strengths and limitations

Line graphs 

• One of the simplest ways to display continuous data

• Both axes are numerical and continuous 

• Used to show changes over time or space

• A river cross-section is a particular form of line graph because it is not continuous data but the plots can be joined to show the shape of the river channel

Bar graphs 

• One of the simplest methods to display discrete data 

• Bar graphs are useful for:

  • Comparing classes or groups of data

  • Changes over time

Scatter graph

• Points should not be connected

• The best fit line can be added to show the relations

• Used to show the relationship between two variables

  • In a river study, they are used to show the relationship between different river characteristics such as the relationship between the width and depth of the river channel

Proportional symbols map

• The symbols on the map are drawn in proportion to the variable represented

• Usually, a circle or square is used but it could be an image

• Can be used to show a range of data, for example, population, wind farms and electricity they generate, traffic or pedestrian flows

Proportional Circles Map Showing GDP (Billion US$) across Europe

Pie chart

• Used to show proportions, the area of the circle segment represents the proportion

• A pie chart can also be drawn as a proportional circle 

• Pie charts can be located on maps to show variations at different sample sites

Pie Chart Showing Energy Sources in an Area

Secondary Data

• Any fieldwork should include secondary data as well as primary data

• In a river enquiry suitable secondary data may include:

  • River discharge data from the Environment Agency

  • Weather data from the Meteorological Office (Met Office)

  • Old photographs of the river sample site

  • Newspaper articles/websites about the river

  • Ordnance Survey maps to identify the sample sites

  • Geology maps 

  • Aerial photographs

Analysis

• Once data has been collected and presented it needs to be analysed

• The data which is collected from the river such as width, depth, velocity is quantitative data and will need to be analysed using statistical methods

• One of the main statistical methods used in a river enquiry will be the mean where mean depth or velocity needs to be calculated

• Geographical theories and case studies can also be used in the analysis to explain whether the data collected was as would be expected based on knowledge from those theories/case studies

Analysing Photographs and Field Sketches

• Use of photographs and field sketches is a qualitative analysis

• Photographs can be used in a river enquiry to analyse a number of features:

  • Landforms and their formation

  • Data collection techniques

Annotation of a photograph

Conclusion

• Once the data collected has been analysed, conclusions can be reached

• This should state whether the hypothesis has been proved or disproved

• Identify and explain anomalies such as:

  • Decreasing average depth or width with distance downstream at one site

  • Decreased velocity at a particular site

• Anomalies may just occur or may be the result of incorrect recording or human error reading equipment 

Evaluation

• The final stage of the river enquiry is the evaluation where you note how successful, or not, the river investigation was and what you would do differently next time

  • Next time I would take measurements over a longer period of time to ensure the reliability of data...

  • My equipment failed and I would make sure to bring a spare next time...

  • I think my investigation went well and I would like to repeat this after a storm event to see how much erosion has taken place...