Fieldwork Method
Measuring the Stream Width
The width of the river must first be found. Stretch the tape measure
from one bank to the other at 90° to the course of the river. The
start and finishing points for the measuring are the points at which
the dry bank meets the water. To avoid drag induced by the tape
making contact with the flowing water, and the consequent possible
increase in distance measured due to the tape being stretched in
to a curve, it should be stretched taught roughly 20cm above water
level. Looking from directly above the tape ensures that the reading
is accurate. It is possible that the river or stream only occupies
part of the whole channel, and that in flood conditions the river
expands and currently dry bank areas are then part of the channel.
Measuring the Water Depth
Find the depth of the river at regular intervals across it's width.
The number of readings taken will depend upon the width of the river
and the amount of detail you require. For most rivers intervals
of 50cm are a good compromise but for smaller streams 30 cm may
be used. The tape measure, which was stretched from one bank to
the other, can be used as a guide to ensure that you take measurements
in a straight line. It is also a convenient way of measuring the
intervals between readings.
Taking depth readings with a metre rule
The metre rule is immersed in the water,
every 30 or 50cm, until it just touches the bed of the river. It
is held with its edge facing upstream, thus reducing to a minimum
the surface area exposed to the running water. It is important to
reduce the exposed surface area as the water may create a bow-wave
and result in inaccurate readings. By positioning the rule with
its narrowest edge facing into the flow it is most resistant to
flexing and least able to create a bow wave. If the water becomes
too deep for a metre rule, a surveying pole or similar item can
be used, the depth marked on it and then measured with a tape. Always
record each of the depth readings as you take it. NEVER rely on
your memory. If possible have a member of your group on the bank
recording the readings as they are taken.
Download stream recording sheet as PDF
or Word file.
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