Paper 3: Physical Enquiry Flashcards
Why is this a suitable hypothesis for a geographical investigation:
Meanders are a distinctive and common river landform found along the middle course of a river. Investigating river velocity and channel depth will help prove that the expected river processes (erosion on the outer bend, deposition on the inner bend) are occurring.
Why was the location of the Ingrebourne River a suitable location for a study area:
The Ingrebourne River has two safely accessible meanders nearby, allowing us to collect data from 2 sites (a broader data set). The depth and flow was safe enough for students to enter and conduct measurements making it a good location to collect data safely. The Ingrebourne River is also a 40 minute tube journey away from school so it is in an accessible location. The short journey time also meant we could spend longer there, investigating the meanders
Getting lost using public transport
Students clearly briefed on the route. Students travel in small groups with a member of staff and get on and off public transport as instructed.
Danger crossing roads on route to the river site
Teachers deliberately selected a site with many pedestrianised areas and safe crossings.
Cross roads only at a crossing, when it is safe to do so and in groups
Working in a river
Teachers deliberately selected a rivers site where the meanders were shallow and velocity was low enough for students to collect data safely to reduce risk of drowning.
Students were instructed to wear wellington boots to avoid slipping on the uneven river bed.
Students briefed about the risk of infection working in open water and covered cuts with plasters and used hand gel after each activity.
Channel cross profile
How was the data collected
Students worked in groups, using a measuring tape to measure width and metre rulers to measure depth at regular distances across the channel. This helped us measure the cross-section
Channel cross profile
Advantages of data collection
The meander channel cross profile (width and depth) was quickly measured and the data recorded on a table that made interpretation very easy.
Changes across the river channel were easy to see.
Channel cross profile
Disadvantages of data collection
Having a number of groups working at the same time trampling across the muddy river bed, may have slightly changed the depth in different places making the results less accurate.
Only two meanders along the river were selected and these were chosen because they were safe, accessible and very close together. The findings may not reflect less accessible meanders along other parts of the river course.
Channel cross profile
Possible improvements
If we had more time we could have had fewer groups working at one time, or have spread out over a greater number of meanders. This would reduce the likelihood of feet trampling the soft riverbed and altering the cross profile. However we are generally confident with our findings as all groups’ data showed a significantly deeper outer bend, supporting the hypothesis.
More time would have allowed us to visit more meanders at different points along the middle and lower course of the river. This would give a wider range of data sets and perhaps reveal more contrasts in channel shape. However we were able to contrast two meanders, and the findings are consistent with what we expected (the meanders were deeper on the outside bend
velocity (speed of the river) measurements
How was the data collected
Students measured a 3 metre distance along the outside bend, the middle of the river and on the inside bend. A float was dropped into the river and we timed how long it took to travel 3 metres. The measurements were completed 3 times and an average velocity measurement was calculated for the outside, middle and inside bend.
velocity (speed of the river) measurements
Advantages of data collection
Data can be collected quickly and easily. The equipment used (satsuma float, phone timers) was easy to manage and the data could be easily recorded on a table.
Taking multiple timings and calculating an average reduces the influence of anomalies and makes the findings more reliable.
velocity (speed of the river) measurements
Disadvantages of data collection
Multiple groups were working in the river at the same time, creating obstacles for the river current. This meant the flow of the water was disrupted as it moved downstream. This could lead to slower velocity compared to a quieter day with no visitors.
The depth of water was low at times meaning the float (satsuma) got stuck or students were tempted to move away from the edges of the meander to get a better flow. The data might lack some accuracy, and make velocity seem faster than it was.
Students based their judgements on a snapshot view of the velocity of the river in one day on a dry month during the summer. At other times of year the flow might vary considerably e.g. after heavy rain it could be faster.
velocity (speed of the river) measurements
Possible improvements
We could have used more sophisticated equipment e.g. a flowmeter, to get more accurate data; water flows through this device and gives a velocity reading. This would overcome inaccuracies caused by the float getting stuck.
If our groups were smaller there would be fewer students in the river, reducing the chance of human obstacles interrupting the flow. This would have improved data accuracy.
Velocity data would have been more reliable if we visited several times at different points during the year with varying levels of rainfall. If we also had data for a wetter, winter month (when discharge and velocity is greater) we could calculate an average velocity for the year. This data would be more reliable/representative.
However on both meanders there was a considerable difference in velocity in the outside and inside bend suggesting overall velocity is faster on the outside bend.
velocity (speed of the river) measurements
data presentation
The located bars showing the average velocity measurement for the outside, middle course and inside bend were very different in size showing a much faster velocity on the outside bend than the inside bend.
velocity (speed of the river) measurements
data presentation cons
Limitations: The located graphs show an average velocity measurement, therefore it gives us an overall picture of velocity across the channel but does not show variations or anomalies within the data sets.
Channel cross profile diagram: data presentation
The cross-profile line graph shows river width and depth from a sideways perspective. This makes it easy to see how the channel changes from the outside to the inside bend. The outside bend was clearly deeper for both meanders.
Channel cross profile diagram: data presentation cons
Limitations: The scale used to show depth in centimetres was different to the scale used to show width in metres which made the river look deeper than it was. However as long as the scale was read correctly the overall change in depth across the meander was still easy to see and understand.
We only measured the depth of the river at fixed intervals, so the cross-profile shape doesn’t perfectly match the actual meander’s shape.
Mapped channel cross profiles and velocity bars (2 methods combined)
Mapping the velocity bars onto the cross profile diagram allowed us to observe patterns and make links between the two data sets. For example, in meander 1, the depth was particularly deep in the outer bend and middle of the river compared to the inside bend. The velocity data was similarly fast in both the outside and middle bend, and the inside bend was significantly slower. This clearly demonstrated where the river was deeper, less friction meant the velocity was faster.
Channel cross profile diagram: data presentation
Alternative presentation method:
Alternative presentation method: Negative bar graph (bars go downwards to show depth
Channel cross profile diagram: data presentation
Alternative presentation method: pros
Advantages: It would be easy to read the depth of the river and specific points across the river meander profile.
Channel cross profile diagram: data presentation cons
Alternative presentation method:
Disadvantages
Hard to see the overall profile/shape of the river channel and how it changes in shape from the outside to the inside bend, making it harder to interpret the data.
Velocity data Alternative presentation method:
Proportional flow arrow
Velocity data Alternative presentation method: pros
Advantages: The arrows overall width is proportional. It might be easier to contrast than the bars. Arrows can also indicate direction of the river current.
Velocity data Alternative presentation method: pros
Disadvantages: The arrow would increase in width according to seconds taken to travel. As a result the slower flow would result in a wider arrow that would appear to indicate a higher value. This would be very confusing to interpret. Furthermore, flow arrows are more difficult to draw and read accurately. Human error could therefore make analysis inaccurate.
