What this lesson teaches
I can explain the positive, negative and unequal impacts of floods.
Syllabus 9173, Topic 2.1, 3. Floods in the Humid Tropics. Why do fluvial floods affect places and people differently?
Make a guess
A river floods a farming plain for a few weeks, as it does most years. Is this only harmful?
- No, because floods rarely harm people.
- No. It can renew the soil.
- Yes, because floodwater kills crops.
- Yes. A flood is a disaster.
Show the answer
No. It can renew the soil.
Shallow, predictable floods bring nutrients, refill water stores and link rivers with wetlands. Timing and depth decide whether a flood helps or harms.
Flood impacts depend on the flood's depth, speed, length and timing, and on how well people can avoid, withstand and recover from it.
Floods can bring benefits. Seasonal floods renew soil nutrients, refill water stores and link rivers with wetlands. Fish reach feeding and breeding areas. Farming and fishing gain when floods come at the right time.
Deep, fast or long floods can kill people, wreck homes and crops, pollute water and cut off transport, schools and hospitals. Businesses lose equipment and income, and supply chains spread the losses. Polluted water and erosion harm ecosystems.
Places differ. A shallow, predictable flood in a farming area adapted to it is very different from deep flooding in a crowded industrial zone. Even within one place, effects are unequal.
Groups differ too. Low-income families may live on cheaper flood-prone land, with no savings or insurance, and lose work when they evacuate. Older and disabled people may need accessible transport and shelters. Good housing, warnings, friends and public services reduce vulnerability. Wealth can raise the value of property at risk, but makes it less likely that one flood destroys a household's livelihood.
- Positive impacts
- Fertile soil, refilled water stores, fish habitat.
- Negative impacts
- Deaths, damage, pollution and lost income.
- Vulnerability
- Savings, insurance, housing and support shape recovery.
Step by step
Describe the flood
Depth, speed, length and timing.
Find who is exposed
Homes, farms, workplaces and services.
Explain vulnerability
Why do groups have different options?
Real examples to use
Thailand, 2011
Floods swamped industrial estates near Bangkok, disrupting global supplies of car parts and computer hard drives.
Worked example: Flood farming in the Mekong Delta
In the upper Mekong Delta, seasonal floods support flood-based farming and renew river ecosystems. The World Bank describes farmers adapting to these flows. But unusual timing and extreme floods can still destroy their livelihoods.
Watch out for this
The group with the biggest money loss is always the most vulnerable.
A smaller, uninsured loss can ruin a family with no savings.
Check your understanding
Why might an uninsured casual worker recover more slowly than an insured business owner after similar damage?
- The worker's home must have had deeper water.
- Lost daily income and few savings slow recovery.
- Insurance makes the river less likely to reach the shop.
Show the answer
Lost daily income and few savings slow recovery.
Yes. Vulnerability is about the ability to recover.