We also discussed the possible safety issues that we should be aware of such as Weil’s disease, slippery rocks and pot holes in the river. We then ensured that a first aid kit was brought with us as well as mobile phones in case of an emergency and that appropriate clothing was worn. Also everyone was made aware of what procedures to follow in an emergency.
The week before the fieldtrip we conducted a small pilot study in a small stream in the grounds of our school where we tested each piece of equipment to make sure it functioned correctly. We discovered that our flow metre was faulty so we decided to instead to time how long it took for an object to cover a stretch of river. We decided to use an orange since it is buoyant and brightly coloured and to use a 10 metre stretch of river since we are using it for other measurements and it is long enough to give reliable results.
Also on the week before of our teachers went down to the river on a pre-site visit to check that all of our pre-determined sites were viable to use. She concluded that all our sites were practical to use in our investigation.
Data Collection: Collected on Thursday 25th October
The primary data used in this investigation is the results we took down on the fieldtrip. The secondary data sources we are going to use are the internet, our class notes and handouts, the David Wough AS level textbook and the Ordnance survey map.
The type of sampling used on the fieldtrip was systematic; the sites chosen to investigate were 1.3km apart. Pragmatic sampling would have to have been used in the event that one of the pre defined sites proved to be inaccessible on the day; none of which were.
Particle Size
Particle size was recorded at each stop by two people measuring the longest axis of 30 stones from the river bed while a third person recorded the results. The average of the lengths was taken for each stop. The equipment used was a metre ruler.
Cross Sectional Area
The width of the river was measured by two people with a measuring tape at either side of the river. The depth was then recorded by another person with a metre stick taking measurements from the measuring tape to the riverbed in increments of 0.5 metres until the whole width of the river was recorded and then an average depth was calculated from these results. The cross sectional area was then worked out by multiplying the average depth by the average width.
Velocity
A ten metre stretch of the river was measured with the tape measure. An orange was dropped at the upstream end and a stopwatch was used to record the time taken for the orange to travel the ten metre stretch. This was repeated three times and an average taken. If the orange got stuck that particular attempt would be scrapped and then it would be carried out again.
Gradient
The gradient of the river was calculated with an abney level and a gauging pole. We used the same ten metre marking used when we measured velocity. We took three readings along the ten metre width and calculated the average gradient from them.
Discharge
The discharge of the river was worked out by multiplying the average velocity and the average cross sectional area found at each site to give the discharge.
