Floods can be deadly, particularly when they arrive without warning. Some are the result of sudden and torrential rain in the local area, while others are caused by melting snow, or by large amounts of rainfall over a wide area.

Occasionally a river bursts its banks, or the sea might surge over a coastline during a storm. Prolonged rain can produce a river flood as water from upstream tributaries gradually builds up. Areas near to the junctions of major rivers are especially vulnerable to this type of flooding.One of the worst aspects of flood damage is the contamination of drinking water supplies by sewage and other waste. It can take months for the destruction to be cleaned up. Now, in Britain there is a flood warning system managed by the Environment Agency and the BBC Weather Centre broadcasts flood alerts.