Topic 1 of 6 · Form 5
Hydrology and fluvial geomorphology
Inputs, stores, flows and outputs; water balance; storm hydrographs and the factors affecting them (rainfall intensity, antecedent moisture, basin shape, relief, rock type, soils, vegetation, urbanisation).
Notes for this topic 1 file, in order
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The drainage basin system
Inputs, stores, flows and outputs; water balance; storm hydrographs and the factors affecting them (rainfall intensity, antecedent moisture, basin shape, relief, rock type, soils, vegetation, urbanisation).
River processes and landforms
Erosion, transport and deposition; the Hjulström curve; channel shape and hydraulic radius (cross-sectional area ÷ wetted perimeter); long profile and graded rivers; landforms from source to mouth (waterfalls, potholes, meanders, braiding, floodplains, levées, deltas).
Worked example: A channel is 10 m wide and 2 m deep (rectangular). Find its hydraulic radius.
Area = 20 m²; wetted perimeter = 2 + 10 + 2 = 14 m → hydraulic radius = 1.43 m
Human impact and flood management
Land-use change, dams and reservoirs (e.g. Kariba), hard and soft engineering, floodplain zoning, forecasting and warning.
Check yourself
- What is lag time?
- Why does urbanisation increase flood risk?
- What does the Hjulström curve show?
Show answers
- The time between peak rainfall and peak discharge.
- Impermeable surfaces and drains increase overland flow and reduce lag time.
- The velocities at which particles of different sizes are eroded, transported and deposited.
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