Why do rivers flood

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Why do rivers flood?
L.O. To understand why some rivers flood. Key
Words Precipitation Permeable Land
Use Deforestation
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Flood Plains
Flood plain. Meanders, oxbow lakes, levees and
point bars can all be found on a flood plain.
The valley is wide and flat, forming rich
farmland.
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The Causes of Floods
Precipitation The most common cause of flooding
is an increased amount of rainfall. The ground
becomes saturated and run-off increases. This
causes FLASH FLOODS and are common in Britain
after summer thunderstorms.
Type of Soil and Underlying Rock Surface run-off
is much greater in river basins where the soil
and underlying rock is impermeable.
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Land Use Deforestation increases the risk of
flooding. This is because trees intercept
rainfall, delaying the time and reducing the
amount of rainfall reaching the river.
Human Activity As urban areas grow, tarmac and
concrete replace fields and woodlands. Surface
run-off is increased. The increase in drains can
cause flash floods as the water reaches the river
quicker.