A river floods when the water normally flowing in the channel overflows its banks and spreads out onto the surrounding land. This causes major problems for people living close to the river.

Why do rivers flood?

People in an emergency boat in a flood in Rotherham, UK

A variety of factors can increase the likelihood of flooding.

Physical causes of flooding:

  • heavy rainfall
  • long periods of rain
  • snowmelt
  • steep slopes
  • impermeable rock (doesn't allow water through)
  • very wet, saturated soils
  • compacted or dry soil

Human factors increasing flood risk: