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.

Find out more about human and physical causes of flooding.

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

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A change from pastoral to arable farming increases the risk of flooding because once crops have been harvested the soil is sometimes left bare in the winter. This reduces interception because there is no vegetation.

Find out more about human and physical causes of flooding.

Three ways humans can increase the risk of flooding in rural areas are:

• Deforestation
• Intensive farming, leaving fields bare in the winter
• Overgrazing
• Increased use of polytunnels

Find out more about human and physical causes of flooding.

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.