Methodology
The measuring of the Horner Wood river was taken at four points
representing examples of the four stream order positions shown on
the map.
Image reproduced from Ordnance Survey map data by permission
of Ordnance
Survey, ©Crown copyright.
At Lang Coombe (871426) near the source the site is in a steep sided
valley which is wooded. Stoke Pero (872429) is a stream order 2
site lower down and near Horner (898458) it becomes Order 3 with
the Order 4 measurements being taken near Bossington (898480)
1. Measuring Stream size:
At each site a tape measure was used to measure the distance from
bank to bank and also the distance across the water's surface. With
two pupils measuring the third person recorded the data. This task
was rotated through the four sites.
The distance from the surface of the water to the top of the bank
was measured. Initially this was small and a 30cm ruler was used
but a metre rule was needed as the distance increased.
Measurements were taken of the depth of the water at quarter, half
and three-quarters distance across the stream, with a small rule
or metre stick. These were to enable cross sections to be drawn.
2. Measuring Wetted perimeter:
This involved holding the tape measure under the water along the
river bed and up the bank where the water was in contact with the
land.
Link
to Wetted Perimeter information
3. Measuring the
speed of flow:
It was important that the velocity of the stream was measured.
The speed of a cork to travel 5 metres was taken with a stopwatch.
This was repeated 5 times to enable an average reading to be calculated.
Finding an unobstructed length of stream was difficult in the higher
parts of the valley.
4. Measuring the slope:
The steepness of the valley floor was measured with a clinometer
by standing in the stream facing upstream and taking the reading
back to a visible point higher up the stream.
5. Measuring stone size:
The stones in the river bed were measured by picking 10 stones
at random and measuring the length of the longest axis and height
of them with a small ruler. This gave information for a formula
to calculate the order of roundness.
Download stone analysis recording sheet as PDF
or Word file
6. Measuring Visual pollution:
The final record was to complete a sheet that gave an indication
of the amount of pollution in the river.
Download visual pollution sheet as PDF
or Word file
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