Floods

A flood is an overflow of water, an expanse of water submerging land or a deluge.

Flooding occurs when an area of land, usually low-lying, is covered with water due typically to a river overtopping its banks or to inundation by the sea. Floods from the sea can cause overflow or overtopping of flood-defences such as dikes and levees as well as flattening of dunes or bluffs. Land behind coastal defences may be inundated or experience damage.

Flash floods

A flash flood involves the rapid flooding, by rivers or streams, of low-lying areas due to intense rainfall. Flash flooding occurs when the ground becomes saturated with water that fell so quickly that it could not be absorbed. The runoff collects in low-lying areas and rapidly flows downhill leading to catastrophically rising water levels. Flash floods mostly occur in normally dry areas that have recently received heavy precipitation. They may also occur anywhere downstream from the source of the precipitation (even tens of kilometres from the source).

Storm Surge

A storm surge is an onshore gush of water associated with an intense low pressure weather system, typically a tropical cyclone. It arises partly due to an elevated sea surface resulting from the reduced atmospheric pressure, and partly to storm winds driving sea-water onto the coastline. In the worst cases, surges can exceed 6m.