G.C.S.E
Controlled Assessment
An investigation of river erosion
along a chosen stretch of river
River Characteristics
• Any river may be divided
into upper, middle and
lower course
• A river’s characteristics
can be measured by
systematic sampling that
allows the investigation of
continuous changes as
distance increases from
the source of a river.
Width
• This is measured by placing one end of a
measuring tape at one side of the river channel,
then pulling it out to the other side of the
channel. The distance is the width of the river.
Depth
• This is completed using a metre stick. The stick
is lowered into the water every 25cm, and the
distance from the top of the water to the river
bed gives the depth. An average of the readings
is taken.
Cross-Sectional Area
• This is calculated by multiplying the width
of the river by the average depth.
Velocity
• The speed of the river is measured using a flow
meter that when dipped into the river gives a
digital reading of the speed of flow in metres per
second.
Discharge
• This is the amount of water passing any
point in a river in a certain time, normally
given as cubic metres of water per second
(cumecs).
• It is calculated by multiplying the crosssectional area of a river channel at a
certain point by the speed (velocity) of the
river at the same point.
Load
• This is the material carried by a river, ranging from large
boulders to small sediment. We focus on the load lying
on the river bed – bed load. This is measured for size
and roundness. By measuring the longest axis of 15-20
random samples at each site an idea of size is obtained.
Each stone is also given a rating for roundness.
Gradient
• The gradient of a river is a measure of how steeply it
loses height. It is measured using a clinometer over a
10m stretch of the river. Ranging poles mark out the
stretch of river. The clinometer is placed against the
height mark on one pole and the angle is observed of the
height mark on the other pole.
Health and Safety Considerations
• Weather
This is an important aspect of fieldwork – having a
reliable and up-to-date forecast for the study
area. This will ensure that you are adequately
prepared by wearing the correct clothing and
that inclement weather will not become a hazard
e.g in the upper course of a river
• Equipment
It is essential that all data collection equipment is
used solely for the purpose it was designed for
e.g ranging poles
• Clothing
Safety helmets will protect the head when working around,
and in, the river. Wellington boats help keep feet
relatively dry and provide some grip on the slippery
rocks/banks of the river. Waterproof jackets and trousers
are essential to remain dry and warm. These should be
worn over thin layers of clothing.
• Movement in the river
When collecting data in the river it is important to modify
our movement over slippery rocks and the river bed.
Three points of contact should be kept in the river
channel and the use of a walking pole can also help
maintain balance.
• Site access
This should be planned in advance – pre site visit. Access
should be assessed in relation to safety e.g the difficulty
of steep river banks or deep sections or the river and the
correct permission must be sought on private property.
Sections of erosion should also be identified e.g river
cliffs/undercutting as banks can collapse
• First Aid provision
It is essential to be familiar with the person in charge of first
aid and to make them aware of any medication that may
be required during data collection e.g inhalers