The document discusses the river basin hydrological cycle and factors that affect the amount of water in rivers. It aims to explain how rainfall runs off impermeable surfaces and permeates through permeable soils into rivers. The water flow is then illustrated on a diagram of a drainage basin. Experiments are proposed to collect rainfall and river discharge data during storms. Hydrographs are introduced to show the relationship between rainfall amounts over time and the resulting change in river discharge levels and timing of peak flows. Factors like soil permeability, rainfall intensity and duration, and basin shape and size are identified as influencing river flooding.

1. Lesson Aims:
1. To understand how the river basin
hydrological cycle works.
2. To understand the factors that effect
the amount of water in the river

2. Water Flows
• Impermeable – water can’t permeate
through it (e.g. tramac, etc.)
• Permeable – water can permeate
through it (e.g. soil)

3. Drainage basin hydrological cycle
(p108)
INPUTS OUTPUTSPROCESSESSTORES

4. How does all this water get into the
rivers?

5. How does all this water get into the
rivers?
• On the mini white board draw a drainage
basin with a main river and tributary.
• Then add ‘real rain’ and show how it
moves down the rivers.
• What will make the ‘rain’ flow faster
into the main rivers?

6. EXPERIEMENT TIME!
How could we collect rainfall
data during a storm?

7. EXPERIEMENT TIME!
How could we collect data from a
river during a storm?

8. Hydrographs
• These are graphs
that show the
amount of rainfall
and the volume of
water discharged
during a storm by a
river.
• Label your diagram

9. 0 12 24 36 48 30 72
Hours from start of rain storm
3
2
1
Discharge(m3/s)

10. 0 12 24 36 48 30 72
Hours from start of rain storm
3
2
1
Discharge(m3/s)
mm
4
3
2
Rainfall shown
in mm, as a
bar graph

11. 0 12 24 36 48 30 72
Hours from start of rain storm
3
2
1
Discharge(m3/s)
mm
4
3
2
Discharge in
m3/s, as a
line graph

12. 0 12 24 36 48 30 72
Hours from start of rain storm
3
2
1
Discharge(m3/s)
mm
4
3
2
The rising
flood water in
the river

13. 0 12 24 36 48 30 72
Hours from start of rain storm
3
2
1
Discharge(m3/s)
mm
4
3
2
Peak flow
Peak flow
Maximum
discharge in
the river

14. 0 12 24 36 48 30 72
Hours from start of rain storm
3
2
1
Discharge(m3/s)
mm
4
3
2
Peak flow
Falling flood
water in the
river

15. 0 12 24 36 48 30 72
Hours from start of rain storm
3
2
1
Discharge(m3/s)
Basin lag time
mm
4
3
2
Peak flow
Basin lag time
Time
difference
between the
peak of the
rain storm
and the peak
flow of the
river

16. 0 12 24 36 48 30 72
Hours from start of rain storm
3
2
1
Discharge(m3/s)
Base flow
Basin lag time
mm
4
3
2
Peak flow
Base flow
Normal
discharge of
the river

17. 0 12 24 36 48 30 72
Hours from start of rain storm
3
2
1
Discharge(m3/s)
Base flow
Through flow
Overland
flow
Basin lag time
mm
4
3
2
Peak flow
Overland flow
Through flow
+
=
Storm Flow

18. What factors effect the discharge
(volume) of water in any river?

19. What factors would influence the
flood hydrograph in this area?

20. What factors would influence the
flood hydrograph in this area?

21. What factors would influence the
flood hydrograph in this area?

22. What factors would influence the
flood hydrograph in this area?