A.2.4: Flood mitigation

Question 1

Advantages of dams for flood mitigation

Answer 1

1. Holds back water during times of flood and releases it when the flood risk is gone
2. irrigation: Dams have helped farmers tackle the problem of watering crops significantly, which has resulted in a boost in crop production.
3. Source of hydroelectric energy

Question 2

Disadvantages of dams for flood mitigation

Answer 2

1. Increased loss of water due to evaporation
2. Channel erosion downstream (“clear-water erosion)
3. Spread of diseases
4. Often emit a high percentage of greenhouse gases

Question 3

Advantages of afforestation for flood mitigation

Answer 3

1. Increases the amount of interception, reducing the amount of overland flow
2. After trees have grown and start to intercept more rainfall, amount of erosion is reduced

Question 4

Disadvantages of afforestation for flood mitigation

Answer 4

Sediment loads may increase after afforestation due to a combination of an increase in:
1. Surface run-off
2. Little ground vegetation
3. Young trees

Question 5

Advantages of channel modification for flood mitigation

Answer 5

1. Raising the banks allow channels to hold more water
2. Straightening the river speeds up the flow and remove the water as quickly as possible
3. Creating new channels (flood-relief channels) to carry water when the river is in flood
4. Channels can be strengthened with steel or concrete to make them less vulnerable to erosion
5. Artificial levees: When banks of the river are increased in height so the river can carry more water and sediment

Question 6

Advantages of planning for flood mitigation

Answer 6

1. Allows for personal insurance and being prepared for floods.
2. Disaster aid: provision of money, equipment, staff and technical assistance that is given to a community following a disaster
3. In HICs, insurance is an important loss-sharing strategy.

Question 7

disadvantages of planning for flood mitigation

Answer 7

1. Not all flood-prone households have insurance and many of those are insured may be underinsured
2. Many people in low-income countries are unable to obtain flood insurance