Floodplain Management - Frequently Asked Questions

Answers to common questions

What should I do in the event of a flood?

If the situation is life threatening you should call 000.

For other assistance during an emergency such as flood, storm or tsunami, please contact the NSW State Emergency Service (SES) on 132 500 or visit their website at www.ses.nsw.gov.au.

It is best to be prepared for any flood. The State Emergency Service also provides advice on how to manage your flood risk, on their website at www.ses.nsw.gov.au/floodsafe/prepare-your-home/before-a-flood/

Why does Council study flooding?

Flooding can cause significant damage to property and risk to life. All Councils are required by the NSW State Government to undertake studies to determine what land has the potential to be affected by flooding. This is to ensure that new developments are adequately protected and do not make flooding worse.

What does being flood affected mean for my property?

Being flood affected means this property has a risk of being flood affected in specific rainfall event. This may result in flood-related development controls being applied to the development consent, for example raising floor levels or using flood resistant materials.

How are flood affected properties identified?

Councils’ flood modelling determines the extent of flooding throughout the catchment and the identification of properties impacted by flooding. When Council is in possession of reliable information regarding flooding, it is obliged to provide that information when asked. This consultation is one way for Council to advise affected property owners and residents of flood affected properties. Council is also required to notate S10.7 Planning Certificates for properties that are identified as flood prone.

What is the Flood Planning Area?

The flood planning area is the area within which developments may be subject to flood related development controls. The flood planning area is calculated as the area lower than the Flood Planning Level.

What is the Flood Planning Level?

The Flood Planning Level (FPL) is a height used to set floor levels for property development in flood prone areas. It is generally defined as the 1% AEP flood level plus an appropriate freeboard (see explanation of ‘freeboard’ below). This level may be higher for vulnerable land uses (e.g. hospitals or schools).

What is Freeboard?

Freeboard is a height above the 1% AEP flood level that is included in the Flood Planning Level to account for factors such as wind, waves, unforeseen blockages, other localised hydraulic effects. Freeboard is usually 0.5m above a flood level.

What is a '1 in 100 year' flood?

A 1 in 100 year flood is a flood event that has the probability of occurring on average once every 100 years, i.e. there is a 1% chance of a flood of this size occurring at a particular location in any given year. This does not mean that if a location floods one year that it will not flood for the next 99 years. Nor, if it has not flooded for 99 years that it will necessarily flood the next year. Some parts of Australia have experienced more than one ‘1 in 100 year’ floods within a decade of each other. The ‘1 in 100 year’ flood is referred to as the 1% AEP flood event in the Mascot, Rosebery & Eastlakes Flood Study.

What is the Probable Maximum Flood?

The Probable Maximum Flood (PMF) combines a range of extreme conditions and probabilities to calculate the largest flood that could possibly occur within a catchment. It is extremely rare and is calculated to aid in the design of critical facilities such as hospitals, nursing homes, schools and emergency service facilities. 

Have impacts from future changes in climate been included in existing flood levels?

Climate change has been considered in the Flood Study, by assessment of the significance of increases in rainfall and sea level on flood levels.

What is the difference between a Flood Study and a Floodplain Risk Management Study?

Flood Studies identify flood behaviour including the areas flooded, water depth, hazard categories and the likelihood of flooding within the catchment. Floodplain Risk Management Studies and Plans assess potential management approaches to reduce the impact of flooding (e.g. drainage upgrades, development controls, community awareness and emergency response arrangements).

My property has never been flooded - why is it considered flood affected?

Floods do not occur in a regular pattern. There may be a period of no floods and a period of several floods. For example, the last time the Brisbane River flooded before the 2011 disaster was in 1974. Residents who moved there in more recent times may never considered flooding an issue until the floods in January 2011. Following extensive rain every water course will flood.

I still don't think my property is flood affected? What can I do?

Members of the public can make a written submission to Council to raise flood related issues. You can provide your valuable feedback and comments by emailing Council.

The floor levels in my property are above the flood level - why has it been identified as flood affected?

Properties can be identified as being flood affected, in accordance with the Council’s policy, regardless of the floor levels in the building. This is to ensure any future developments of the property are appropriate for the Flood Planning Area and not built below the flood level.

Property owners can seek flood level information about their property from Council. Application forms for flood advice application can be found in the link below:

Flood Advice Application Form

Will I have to undertake a flood study when I want to develop my land?

It depends on the type and scale of the development. New developments which affects the flood behaviour and has potential to negatively impact the flood affectation to the neighbouring properties will require flood study & flood impact assessment with development application lodgement.

Will being flood affected impact the value of my property?

There are many factors that can affect the value of any property including inflation, a change in interest rates, increased aircraft noise or construction of a new road or shopping centre nearby. The extent to which a property’s value is affected once it has been identified as flood affected is impossible to determine. While the notification may affect one potential buyer’s decision to purchase a property it may have no impact for another. Ultimately, it is the market that determines the value.

Will being flood affected increase my property insurance?

Council doesn’t put together flood studies or floodplain risk management plans for, or on behalf of insurance companies. Flood Studies are a legal requirement for Council to complete and part of our responsibilities to help manage flood risk in the community. Insurance companies may rely on their own assessment of risk and can use their own methods to identify flood risk.

What are Councils doing to manage flood risk?

Councils prepare Flood Studies and Risk Management Plans according to the NSW Government's Floodplain Development Manual (2005). The recommendations are implemented with the technical and financial assistance of NSW Government and key stakeholders through the Flood Prone Land Policy.

What about flooding problems in my street that happen all the time?

Development over many years has left many areas with a legacy of undersized infrastructure which cannot adequately carry water from minor storms. It has also removed many natural creek or open water surface bodies in the catchment areas to accommodate stormwater. This results in flooding of many properties. Council undertakes upgrades of its piped stormwater system on a priority basis across the local government area as funding allows.

Why can't council fix all flooding?

Council’s piped stormwater system is designed to convey frequent minor storms with the aim of reducing day-to-day nuisance flooding, while major storms are conveyed via overland flow paths with the aim of protecting life and property in major events. It is impractical to provide piped drainage systems for major storm events as this is cost prohibitive.

Floodplain Management - Frequently Asked Questions
Need to contact us?

Call 1300 581 299 (weekdays 8:30am-4pm and Saturday 9am-1pm) or email council@bayside.nsw.gov.au