Disaster Management · M2 · papers
Flood questions
Solved M2 questions
2-mark and 3-mark practice · full answers below each question
Practice question. Differentiate between slow-onset floods and flash floods. [3 practice marks]
Answer
| Slow-onset | Flash |
|---|---|
| Gradual rise, often from prolonged basin rainfall. | Sudden rise, commonly after intense rainfall or dam failure. |
| Usually more time for warning and evacuation. | Often little warning time. |
| Long inundation disrupts crops and livelihoods. | Fast, debris-laden flow can cause immediate destruction. |
Practice question. Explain three causes of urban flooding and corresponding measures. [3 practice marks]
Answer
- Impervious roofs and roads increase runoff; permeable surfaces and rain gardens can reduce and delay it.
- Blocked or inadequate drains cannot carry peak flows; cleaning, capacity upgrades and connected outlets improve drainage.
- Encroachment on wetlands and floodplains removes storage and exposes settlements; protection of these areas and risk-based land-use control reduce losses.
Practice question. Explain any three structural flood mitigation measures. [3 practice marks]
Answer
- Reservoir storage: retain part of a flood inflow and release water in a controlled manner to lower the downstream peak.
- Embankments: provide raised barriers that limit river overflow; inspection and maintenance reduce breach risk.
- Drainage and channel improvement: remove blockages and bottlenecks and restore designed conveyance so excess water drains safely.
Practice question. Explain floodplain zoning and its importance. [3 practice marks]
Answer
Floodplain zoning divides flood-prone land according to risk and regulates permitted development.
- It limits exposure by restricting vulnerable settlements and critical facilities in high-risk zones.
- It preserves natural drainage and floodwater storage, reducing obstruction and encroachment.
- It supports safer growth, evacuation planning and lower future rescue and recovery costs.
Practice question. State two beneficial and two harmful effects of floods. [2 practice marks]
Answer
Benefits: deposition of nutrient-rich sediment can improve floodplain fertility; infiltration can recharge groundwater and wetlands. Harm: fast or deep floodwater can cause deaths and property damage; contaminated water and disrupted services can create health and livelihood losses.