Floodplains form due to erosion and deposition. Erosion removes any interlocking spurs, creating a wide, flat area on either side of the river. During a flood, the material being carried by the river is deposited (as the river loses its speed and energy to transport material). Over time, the height of the floodplain increases as the material is deposited on either side of the river. The floodplain is often a wide, flat area caused by meanders shifting along the valley.

Find out more about landforms in the lower course of the river.

The steepest gradient in the long profile of a river is found in the upper course near to the source.

Find out more about the long profile of a river.

Hydraulic action is when the force of fast-flowing water hits the bed and banks and forces water and air into cracks in the bedrock. The repeated changes in air pressure cause the river bed to weaken.

Find out more about river erosion.

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.

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.