Water on the Land - Flooding

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  • Created by: 12BE
  • Created on: 07-05-17 14:47
What is a flash flood?
A flood that happens without warning
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Why do rivers flood?
When the river discharge increases, so does the water level. If the level of water gets too high, water spills over the banks
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Name 4 physical factors that can cause flooding
Prolonged, heavy rainfall, low temperatures, relief and snowmelt
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How does prolonged, heavy rain cause flooding?
After a long period of rain, the soil becomes saturated so less infiltration occurs which increases surface runoff and decreases lag-time. Heavy rainfall adds lots of water to the river quickly
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How does low temperatures cause floods?
There is less evapotranspiration so more water reaches the river
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How does relief effect floods?
Water flows more quickly on steep slopes which reduces lag-time in steep sided valleys
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How does snowmelt cause flooding?
Snow and ice all melt in a short space of time as the teperature will produce a lot of water so the discharge is increased quickly
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Name 4 human causes of flooding
Dams, deforestation, buildings and global warming
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What role do trees have in preventing floods?
Trees intercept rainwater on their leaves which then evaporates and take up water using their roots and store it. They act as a natural barrier to increase lag time and peak discharge
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Why are buildings increasing flooding?
There are more impermiable surfaces e.g. concrete and tarmac which increases surface runoff and drains take water straight to the river reducing lag time
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How do dams increase flooding?
Dams flood the land behind them when they are built and can cause big problems if they burst
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Why does global warming affect flooding?
Rising temperatures mean that there is more water in rivers and climate change has caused more precipitation in some areas
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What has happened in recent years?
In the last twenty years, floods have become more rfequent and more severe
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Give an example of more frequent flooding in the UK
The River Ouse in Yorkshire reached a high water level 29 times 1966-86 but it has reached the same level 80 times 1987-2007
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Name and date 3 UK floods
Carlise 2005, Cornwall 2004 and South Midlands 2008
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Other cards in this set

Card 2

Front

Why do rivers flood?

Back

When the river discharge increases, so does the water level. If the level of water gets too high, water spills over the banks

Card 3

Front

Name 4 physical factors that can cause flooding

Back

Preview of the front of card 3

Card 4

Front

How does prolonged, heavy rain cause flooding?

Back

Preview of the front of card 4

Card 5

Front

How does low temperatures cause floods?

Back

Preview of the front of card 5
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