Processing Results
Fieldsketching
§ Get students to redraw the fieldsketch
§ Draw the fieldsketch on the OHP to guide
them
§ Use the 9 part grid as a guide
§ Annotate the sketch
§ Colour and title the sketch
§ Ask students questions on the sketch to
help them draw conclusions
Sketch of Owenbeg
Conclusions
‘I identified the following features: meander,
flood
plain and a bluff line. The presence of
these
features showed that
lateral erosion was taking
place. The river also seemed to be
incised into its valley.
This led me to conclude that the river
was in its middle course but it was being
rejuvenated ‘
Calculating Discharge
§
Work out the cross-sectional area of the river in metres squared
average depth x width
§
Work out the average distance travelled in a second in metres
10 metres ÷ average number of seconds
§
Work out the discharge in cubic metres per second (CUMECS)
cross-sectional area x distance travelled in a second x 0.8
(We multiply by 0.8 to account for the difference in speed at the surface and at
the bed of the river)
Plotting Discharge
Cumecs
Discharge
4
3.5
3
2.5
2
1.5
1
0.5
0
Site 1
Site 2
Site 3
Sites
Plotting Discharge
Plotting Discharge using proportional arrows
Discharge Map
Site 1
Site 2
Site 3
Dogs
Bay
1 Cumec =
Constructing a Valley Profile
§
§
§
§
§
§
§
§
Use graph paper
Copy graph paper onto acetate for use on OHP
Add up the length of each section of slope
Decide on a scale which will fit the profile onto one
sheet of graph paper
Begin by drawing a rectangle to represent the river
Use a protractor to get the slope angles
Draw the angles in pencil
Colour the profile
Constructing a Cross Profile of a Valley
Construction Lines
Profile Lines
Constructing a Cross Profile of a Valley
h
t
g
en
L
Construction Lines
Profile Lines
Constructing a Cross Profile of a Valley
2
1
Construction Lines
Profile Lines
Constructing a Cross Profile of a Valley
3
2
4
1
1
Construction Lines
Profile Lines
Constructing a Cross profile of a Valley
Construction Lines
Profile Lines
Calculating Sinuosity
§ Sinuosity is a measure of the curvature of a
river
§ Sinuosity compares the straight line
distance with the curved distance
§ The sinuosity ratio tells us if a river is
meandering or not
§ The ratio is expressed as
Straight Distance : Curved Distance
Sinuosity
For example:
52 paces : 94 paces
Always express a ratio as 1: -----1 : 94 ÷ 52
1 : 1.8
§ When the curved distance is more than one and a
half times the straight distance the river is
meandering
§ So in this example the river is meandering
Sinuosity Graphh
2.0
1.5
1.0
0.5
Site 1
Site 2
Site 3
Sinuosity
§ The sinuosity results show that the river at
Site 1 is not meandering
§ The river is meandering at Site 2 and Site 3
§ We concluded that lateral erosion is
important in Sites 2 and 3 but not so in Site
1
§ We also concluded that meandering
increases downstream
Bedload Grain Size
§ Extract the long axes of the grains from the
record sheet
§ Get the average of the long axes
Total of long axes ÷ The number of grains
§ Draw scaled diagrams of the grains onto
graph paper
Average grain Size of Bedload
Site 1
Site 2
0
1
2
3
4
5
6
7
CMS
Site 3
Index of Roundness
§ The index of roundness measures the degree of
roundness
§ Get the average long axis of the grains
§ Get the average medium axis of the grains
§ Get the average short axis of the grains
§ Index of Roundness ==
average medium axis + average short axis × 50
Average long axis
§ The closer the index is to 100 the more rounded the
grain is
Grain Size of Bedload
§ Grain size decreases downstream
§ The grains are worn down by the process of
attrition
§ The grains become more rounded
downstream because of the process of
attrition
Presentation of Results
Site 1
Site 2
Site 3
Dogs
Bay
1 Cumec =
Evaluation
§ Evaluate the planning, fieldwork and processing
phases of the investigation
§ Evaluation can be stimulated through a
questioning approach e.g.
Which activities worked?
Which activities didn’t work?
What did you do well?
What did you feel needed to be improved?
What questions were raised by your investigation?