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.

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

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.

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.

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

Find out more about human and physical causes of flooding.