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.

Solution, suspension, saltation and traction.

Find out more about how rivers transport material.

Examples include:

• benefits wildlife by creating habitats
• it’s a natural method of intercepting precipitation and slowing water transfer in a river basin
• absorbs and stores carbon reduce the amount of carbon dioxide in the atmosphere
• relatively inexpensive.

Find out more about soft engineering.

In the upper course, the valley cross-profile is narrow and steep-sided. The river takes up most of the valley floor. In the middle course, the valley becomes wider due to lateral erosion. By the lower course, the valley is almost flat, consisting of a wide flood plain.

Find out more about the cross profile of a river.

Hydraulic action

Find out more about river erosion.