Causes of Flooding Flashcards

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Give three natural ways flood risk can be increased.
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Natural ways flood risk can be increased include:

  • heavy rainfall caused by depressions causing heavy, continuous rain which saturates the soil. The land can no longer absorb water as it is saturated increasing surface run-off, higher river discharge and flooding.
  • sudden downpours occurring following a very dry period can lead to flooding because the surface is baked hard. Surface run-off occurs as water cannot infiltrate leading to higher river discharge and flooding.
  • sudden snowmelt releases stored water that flows over the land as surface run-off
  • the loss of vegetation cover through drought or disease can lead to flooding as less interception occurs so more precipitation reaches the surface leading to increased surface run-off.

Find out more about human and physical causes of flooding.

Give three natural ways flood risk can be increased.
How does building a new housing estate on the floodplain increase the risk of flooding?
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Building a new housing estate on the floodplain increases the risk of flooding because the surface becomes impermeable due to the construction of houses, tarmac roads and concrete pavements. Surface run-off increases leading to a rapid increase in a river’s discharge.

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How does building a new housing estate on the floodplain increase the risk of flooding?
How can relief increase flood risk?
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Relief can increase flood risk because:

  • Steep sided slopes mean that it is hard for infiltration to occur which leads to greater surface run-off
  • Low lying flood plains are at risk of flooding because they do not have enough gradient to move the water on quick enough. This risk increases when the soils have a high clay content.
  • Upland areas are more likely to experience rain due to relief rainfall. This increases the likelihood of high levels of precipitation and therefore surface run-off.

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How can relief increase flood risk?
How can geology increase flood risk?
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Geology can increase the risk of flooding when:

  • The upland bedrock is impermeable, such as slate, which means there is more surface run-off
  • Soil in low lying areas is made up of clay. Because it is so compact it is difficult for infiltration to occur.
  • Areas of permeable rock, such as limestone, become inundated with water leading to increased surface run-off

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How can geology increase flood risk?
Identify three ways humans can increase the risk of flooding in urban areas.
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Three ways humans can increase the risk of flooding in urban areas are:

  • Building new infrastructure e.g. roads and paths
  • Building new houses
  • Disappearing gardens

Find out more about human and physical causes of flooding.

Identify three ways humans can increase the risk of flooding in urban areas.




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