Flooding is when the water level in a creek, river, lake or the sea rises and covers land that is usually dry.  Whilst some floods occur without problem, others are devastating, causing large-scale destruction and significant loss of life.  Flooding is experienced all over the world and in some countries such as Bangladesh, flooding occurs regularly.

The rise in water level can be due to numerous causes, although the most common in Australia is heavy rainfall.  Flooding that is sudden and unexpected is referred to as flash flooding.  It is usually caused by slow-moving thunderstorms that deposit an extraordinary amount of water in a relatively short period of time.

Due to its location at the foot of the Illawarra Escarpment, Wollongong is particularly prone to flash flooding.  As heavy rainfall occurs along the escarpment, runoff reaches the creeks very quickly, giving local residents little time to prepare.

Floods are often classified by their severity.  The scale used to classify floods in Wollongong is:

• Minor flooding – media reports of minor flooding, road closures, and traffic disruptions only;
• Serious flooding – media reports of floods affecting residential areas;
• Severe flooding – media reports of flooding of homes, shops or factories, evacuation of low lying properties;
• Very severe flooding - media reports of equal to worst on record extensive flooding of homes, shops or factories, evacuation of many residents and substantial damage to property and facilities; and
• Extreme flooding - media reports of unprecedented damage/levels of flooding, massive flood damage to property and facilities, widespread evacuation of residents in life threatening conditions.