Floods occur whenever river water flows across normally dry land. Both rivers and seas can cause flooding and they can bring destruction. River floods also bring benefits to farmland in the form of fertile silt and mud.

To either side of a river channel there is a floodplain. This is a very flat band of land which has been made by the river during previous floods. Anything built on the floodplain – no matter how many kilometres it might be from the river – will be flooded from time to time.

A flooded airfield. Airfields are often built on a flood plain because the land is naturally flat.

A house on a floodplain during a flood.

The flooding river may carry huge amounts of material with it. In mountain areas these can be boulders and bring immense destruction.

Flooding rivers are quite capable of carrying away whole houses, especially those with wooden frames.