Flooding in Wollongong

Contents: What is a flood? | History of flooding in Wollongong | Recorded floods in Wollongong

What is a flood?
Flooding is when the water level in a creek, river, lake or the sea rises and covers land that is usually. Whilst some floods occur without problem, others are devasting, 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 - media reports of minor flooding includes road closures and traffic disruptions only;
• serious - media reports of floods affecting residential areas;
• severe - media reports of home, shop and/or factory flooding, as well as evacuations of low lying properties;
• very severe - media reports of extensive flooding to homes, shops and/or factories, evaculations of many residential areas and substanial damage to property and facilities;
• extreme - media reports of unprecedented damage/levels of flooding, massive flood damage to property and facilities, widespead evacuations of residents in life threatening conditions.

History of flooding in Wollongong
Surrounded by natural beauty, Wollongong is a wonderful city in which to live, but the very nature of the beautiful landscape makes us prone to flooding.  The combination of steep terrain and flat coastal areas and the proximity of properties to watercourses and major stormwater drains make the area particularly susceptible to flash flooding.

Flooding is a natural hazard that affects the entire community and is something we must all contend with. Flash flooding results from relatively short intense bursts of rainfall, and due to the speed of the resulting runoff which occurs, generally providing little warning time available to minimise flood losses.

Flash flooding is common across our region and unfortunately provides residents with very little time in which to respond. Therefore it is important that all residents are aware of their flood risk and of some of the basic measures you can take to prepare yourself for a flood and how to cope during a flood event. 

It the past 50years, Wollongong has experienced over 30 floods classified as serious, severe or very severe. During this period, there were also three floods that were classified as extreme. In February 1984, 800mm of rain fell in a 24hour period! The last extreme flood occurred in 1998, causing millions of dollars worth of damage.

Historical evidence in Wollongong shows that there is a high probability that structures along creeks and stormwater drains may block during major flooding. This tends to worsen the impacts of the flooding. Structures may become blocked with natural debris (for example, tree branches) or with artifical debris such as shopping trolleys or even small cars that are washed into the watercourse. This is a catchment-wide problem.

Wollongong is a beautiful environment to live in. With the knowledge we possess about our environment's weaknesses, we are able to respond to potential flood problems with confidence.

It is important to realise that floods can occur at any time, and that floods bigger than previously recorded can occur.

If you live close to a creek, a major stormwater drain or outlet, or live in a low-lying area, you may be in risk of flooding. Visit our flood education page - it will list some basic measures you can make before and during a flood.

Recorded floods in Wollongong:

Source: Davidson (1981) Extended Forbes Rigby (2001)