(a) Describe five causes of flooding (b) In what four ways can flooding be controlled?

Answer Details

(a) Five causes of flooding

1. Heavy and prolonged rainfall that exceeds the rate of infiltration and river discharge, so the excess water spreads over the land.
2. Overflow of rivers when the volume of water exceeds the capacity of the channel, especially on the flood plain of the lower course.
3. Poor or blocked drainage systems in towns, where drains choked with refuse and silt cannot carry away run-off.
4. Deforestation which removes the vegetation that intercepts rain and promotes infiltration, thereby increasing surface run-off.
5. Coastal storm surges and high tides that drive sea water inland over low-lying coastal land; dam failure or excessive release from dams may be added.

(b) Four ways flooding can be controlled

1. Construction of dams and reservoirs upstream to store excess water and release it gradually.
2. Building of embankments, dykes and levees along river banks to confine the water to the channel.
3. Provision and regular clearing of wide drainage channels to carry away surface water quickly, and control of building on flood plains.
4. Afforestation and reforestation of catchment areas to increase interception and infiltration and reduce run-off; river channels may also be dredged and straightened to speed discharge.