Frequently asked questions about floods

Why do flood levels and information need to be reviewed over time?
There is a chance that floods of any size will occur in the future. As the size of a flood increases the chances of it occurring become smaller. Because some of these rare floods have not occurred for over a century, the height of future floods is predicted using computer models. These models simulate different flood levels and velocities for a variety of different sized floods.

Given the importance of accurately predicting flood levels and information, Council engages experts to establish and operate the computer models. From time to time, computer models are reviewed and predicted flood levels may change slightly. The reason why the models are revised can include:

• new floods occur, providing additional data to fine-tune the model;
• flood mitigation works undertaken may change flood levels;
• more advanced computer models become available;
• development within the floodplain may be outside Council’s control.

My property was never classified as ‘flood prone’ or ‘flood liable’ before. Now it is classified as being flood affected.
In 2001 the state government changed the meaning of the terms ‘flood liable’ and ‘flood prone’ to include land that could possibly be inundated up to an extreme flood known as the Probable Maximum Flood (this is a very rare flood). Prior to this, only a flood up to the 100-year flood level was considered therefore excluding some properties potentially at risk of flooding.

The definition was changed because there has always been some land that was above the 100-year flood level and at risk of flooding. History has shown us that whilst these larger floods might be unusual, they can and do arise. Examples of such events occurred in Nyngan (1990), Coffs Harbour (1996), Wollongong (1998), and recently in large areas of Europe (2002).

If your property is now classified as flood affected, the real flood risks on your property have not changed, only the classification has altered.

Will my property value be altered if I am flood affected?
If your property is classified as being flood affected, a prospective buyer of your property could have previously found out this information if they made enquires themselves with Council. The property market determines the value of any residential property. Individual owners should seek their own valuation advice if they are concerned that flood affectation may influence their property value.

Can a flood affected property be developed?
Properties affected by flooding can be developed (in most instances) so long as acceptable risk management criteria are demonstrated and applied. Wollongong City Council’s Development Control Plan 54 - Managing Our Flood Risks, sets out these criteria, consistent with the NSW Government Flood Prone Land Policy.

The planning controls applicable to a flood affected property are specific to the proposed land use and the floodplain and the extent of flooding on your property.

Council’s development controls make reference to the 100-year flood level and the flood risk precincts. You must therefore obtain and use this information when preparing a development application for your property.

Will I be able to get house and contents insurance if I am flood affected?
In contrast to the USA and many European countries, flood insurance is generally not available for residential property in Australia. Following the disastrous floods in Wollongong in August 1998 and Coffs Harbour in November 1996, some insurance companies are now offering very limited flood cover. In some instances, insurance companies may offer limited flood cover, however it is most likely that your insurer does not offer you flood cover. Obviously insurance policies and conditions may change over time or between insurance companies, and you should confirm the specific details of your situation with your insurer.

What does Australian Height Datum mean (AHD)?
Australian Height Datum refers to the elevation (on the ground) of any object, relative to a reference point. In Australia this reference point is sea level which is taken as 0 metres AHD. All flood levels, floor levels and ground levels are provided in meters AHD. For example, if the floor level of your house is 6.7m AHD and the height of floodwaters for the 100-year flood is 7.2m AHD, the depth of water would equal 0.5m (7.2m AHD -6.7m AHD).

What is the Probable Maximum Flood (PMF)?
The PMF is the largest flood that could possibly occur. It is a very rare and unlikely flood. Despite this, a number of historical floods in Australia have approached the scale of a PMF. Every property potentially affected by a PMF will have some flood risk, even if it is very small. Under the state government changes implemented during 2001, councils must now consider all flood risks, even these potentially small ones, when managing floodplains.

What is the 100-year flood?
A 100-year flood is a large flood that has the chance of occurring once in a 100-years. This does not mean that a flood of this size will only occur once every 100 years. There is a 1% chance that a flood of this size will occur in any year. If you have experienced a 1 in 100-year flood, it would be unwise to think you will need to wait another 99 years before the next flood occurs. Floods do not happen like that. Some parts of Australia have received a couple of 100-year floods in one decade.

How can I find out if a property has a flood problem?
Wollongong City Council has extensive knowledge of flood levels from recordings of historical events and also from catchment flood studies for some of the catchments across the region. There are two types of flood information that you may request Section 149 Certificates (2&5) and/or a Flood information report.

What is Council doing to manage the flooding problem?
Flood risk management in Wollongong is undertaken on two levels:

• Council enforces development controls such as minimum floor levels and prohibiting specific land uses in areas prone to flooding. These are set out in Council’s Development Control Plan 54 - Managing our flood risks; 
• in accordance with the NSW Governments flood prone land policy, Council formulates and implements Floodplain Risk Management Plans. These plans involve catchment wide studies that identify significant flooding issues and floodplain management studies that identify potential flood mitigation solutions and strategies. Some of these flood mitigation options could include:

What can I do to be flood prepared?
Visit our flood education page for flood preparation measures

What can I do to minimise flooding?
Flooding is a significant issue within the Wollongong region, which affects the entire community, and actions by individuals may have serious consequences on others within the catchment. To play your part:

• be aware if your property is affected by flooding or contains a potential overflow path;  
• be aware of what drainage easement affects your property;  
• be conscious of flow paths around your dwelling and keep them clear - be careful not to dispose of grass clippings and other garden cuttings in or near the watercourse and remove any obstructions that may cause blockages.;  
• do not fence over known flow paths;  
• do not construct raised gardens or plant significant trees or vegetation within flow paths - Certain species such as Jacaranda, Poplar, Willow, Fig, Camphor Laurel, rubber Trees and other types with aggressive root systems can cause pipelines to become blocked or cracked;  
• do not perform any significant work (earthworks, creek bank protection, bridges, piping etc) to the watercourse through your property without first consulting Council;  
• do not lay any pipes, construct a bridge or divert a watercourse without first consulting Council -  unapproved work can increase flooding for both you and your neighbours; 
• do not fill in low lying areas of your yard without seeking Council approval may cause water to pond and increase flooding potential on both your property and your neighbour’s.

With your help, we can help to minimise flood risks and damages.