Flooding Cambridge IGCSE Environmental Management revision
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In plain words
A flood is water in the wrong place: a river that no longer fits inside its banks, or a sea that comes ashore. Some floods are pure weather. A good many are made worse by what people have done to the land upstream.
10 things to know
- Flooding happens when water covers land that is normally dry.
- Land relief, the shape of the land: water runs quickly off steep slopes into rivers, and collects on flat, low-lying land.
- Soil. Saturated soil is already full of water. Compacted soil has had its pore spaces squashed. In both, rain cannot infiltrate, so it runs off. Soil erosion fills rivers with silt, so they hold less water.
- Deforestation removes the trees that intercept and take up water. Some agricultural practices, such as overgrazing and ploughing up and down slopes, increase run-off. Urbanisation covers the ground with impermeable surfaces.
- Climate change raises sea level and brings more extreme weather events. Storm surges and tsunamis push the sea onto the land.
- Impacts: damage to buildings and infrastructure; loss of crops, livestock and habitats; evacuation of people and livestock; and landslides.
- Drinking-water supplies are contaminated, bringing water-related disease. There are financial losses and harm to human health.
- Before: monitoring and warning of river levels and rainfall. Land use zoning keeps buildings off floodplains. Buildings can be raised or made flood-proof. Disaster preparation covers plans, drills, emergency supplies and rescue teams.
- During and after: evacuation, shelters, the rebuilding of damaged areas, and international aid.
- Flooding also brings opportunities. Nutrient-rich silt is deposited on farmland, making it fertile. Surface water and ground water stores are recharged.
Worked example
A town has grown, and fields upstream have been covered with roads and car parks. Explain why the town now floods more often.
- Concrete and tarmac are impermeable, so rain cannot infiltrate.
- The rain becomes surface run-off, and drains carry it quickly to the river.
- More water reaches the river in a shorter time, so the river rises faster and overflows.
Tips and tricks
- For every cause, finish the chain to the river: less infiltration, more surface run-off, the water reaches the river faster.
- Flooding has benefits in this syllabus. Learn the two: fertile silt on farmland, and recharged water stores.
It lands in your notebook with its questions as flashcards.
Flooding: 6 questions and answers
These are the quiz’s questions. Do the quiz first, then come back here for the ones that got you.
What is saturated soil?
No more rain can soak in.
Why does urbanisation increase flooding?
Rain runs off concrete and tarmac.
What is a storm surge?
Strong winds pile the sea up against the coast.
Which is an opportunity brought by flooding?
The silt is rich in nutrients.
How does land use zoning reduce flood damage?
Nothing valuable is left in the way of the water.
Why does compacted soil increase flooding?Stretch
The rain runs off the surface.
Quiz
6 questions
Tap an answer and you’ll see straight away whether it’s right, and why.
Worksheet
3 questions, 8 marks. Write your answers on paper, then check them.
Flooding
Cambridge IGCSE Environmental Management 0680 · 8 marks · papermunch.org
Name ______________________________ Date ______________
Explain how deforestation increases the risk of flooding.[3]
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Trees intercept rain and take up water through their roots. Without them, more rain reaches the ground and runs off the surface. Water reaches the river faster, and eroded soil silts up the channel.
State two opportunities that flooding provides for people.[2]
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Nutrient-rich silt is deposited on farmland. Surface water and ground water stores are recharged.
Describe three strategies for managing the impacts of flooding.[3]
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Any three: monitoring and warning; land use zoning; flood-resistant buildings; disaster preparation; evacuation; shelters; rebuilding of damaged areas; international aid.
Answers: Flooding
- 1. Trees intercept rain and take up water through their roots. Without them, more rain reaches the ground and runs off the surface. Water reaches the river faster, and eroded soil silts up the channel.
- 2. Nutrient-rich silt is deposited on farmland. Surface water and ground water stores are recharged.
- 3. Any three: monitoring and warning; land use zoning; flood-resistant buildings; disaster preparation; evacuation; shelters; rebuilding of damaged areas; international aid.