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.

Large boulders and rocks are rolled along the river bed.

Find out more about how rivers transport material.

Examples include:

• it can reduce habitat diversity when hillsides are covered in tree
• it can lead to acidity in the soil
• the loss of farmland

Find out more about soft engineering.

River cross profiles show you a cross-section, taken sideways, of a river’s channel and/or valley at certain points in the river’s course.

Find out more about the cross profile of a river.

Characteristics of a gorge include:

• very narrow valley
• very steep, high valley sides is
• located immediately downstream of a waterfall
• river channel takes up most, if not all, of the valley floor
• boulders litter the river bed
• turbulent, fast-flowing whitewater

Find out more about the landforms of erosion in the upper course of a river.