If you are currently being impacted by flooding, visit our Emergency Dashboard for updates from emergency services.
To find out if your property is prone to flooding
First check Shire Maps flood-prone land map which shows flood risk and planning area.
- Choose the "Flood prone land" button and enter your address in the search box
- then select "I want to..." and "Show legend"
- view your property and its current flood zone status (does not include draft Overland Flow - Flood Study).
If your property:
- appeared under a flood zone in the Shire map (instructions above), or
- you have a notation regarding flood development controls on your 10.7 planning certificate, or
- you have received a letter regarding the Draft Sutherland Shire Overland Flow - Flood Study
please contact our Catchments and Waterways staff on 9710 0333 to find out if we can provide you with flood information.
Once you have confirmed that we have flood information for your property, you can Submit an Application for Flood Information Certificate.
We are committed to sound flood risk management, as outlined in the NSW Government’s 2023 Flood Risk Management Manual.
For more information about flooding in your catchment, you can also check our flood studies and floodplain risk management studies and plans for your area.
Development and construction work in floodplains
Development and construction work in floodplains is controlled to minimise both the impact of flooding on your property as well as the impact on neighbouring properties.
Different controls apply depending on what kind of development it is, the nature of flooding and the development approval pathway.
For complying development (CDC), the proposed development must satisfy requirements given in the State Environmental Planning Policy (Exempt and Complying Development Codes) 2008 (State Environmental Planning Policy (Exempt and Complying Development Codes) 2008 - NSW Legislation).
For the purposes of the Code SEPP, all flood-affected properties in the Sutherland Shire are deemed to be a flood control lot.
Flooding FAQs
Flooding usually occurs when heavy rainfall falls faster than the ground, creeks, rivers or stormwater system can carry it away.
The size and extent of a flood depend on several factors, including how much rain falls, how long it lasts, the shape of the surrounding land and how much of the area is covered by hard surfaces such as roads, driveways and roofs.
- Overland flooding: stormwater runoff flows overland towards a waterway.
- Riverine flooding: rising water levels in creeks and rivers overtop banks and inundate surrounding land.
- Coastal flooding: inundation of low-lying coastal areas caused by a combination of high tides, storm surge and waves.
Flooding in the Sutherland Shire can result from rivers, creeks or the coast, however, the most common flooding which residents experience is overland flow flooding.
Overland flow typically occurs when rainwater flows over a surface, such as lawns, roads, roofs, car parks and natural areas, on its way to the nearest drain, creek or river. Overland flow flooding can occur during heavy rainfall when stormwater systems temporarily cannot capture all runoff, causing water to flow across:
- Natural low points in the land
- Open channels and drains
- Roads and footpaths
- Public reserves
- Private property
Floodplain Management Australia (FMA) is the national peak body for flood risk professionals. It promotes responsible development on floodplains and raises awareness of flood risks to help reduce impacts on people and property.
FMA has also developed an Overland Flow Factsheet to support clear communication with Councillors, Council staff, ratepayers and the wider community.
Overland flow explained
Flood risk is the chance of a property or area being affected by flooding and the potential consequences if flooding occurs.
In NSW, local councils are responsible for stormwater drainage and managing flood risks in their communities. The NSW Government supports councils with funding and technical advice through its Floodplain Management Program.
The aim of this program is to better understand flooding and reduce its impacts on people, homes and businesses.
As part of this program, councils prepare flood risk management plans. These plans explain how flood risks will be managed in the area and can include actions like improving stormwater drainage or other flood mitigation measures.
Flood risk management is the process of understanding where flooding may occur, how severe it could be and what can be done to reduce its impacts on people, property and infrastructure.
The process starts with a Flood Study, which uses computer modelling to understand how floodwaters behave during different rainfall events. These studies help identify areas that may be affected by flooding now and into the future.
A Flood Risk Management Study then assesses the potential risks and investigates options to reduce flood impacts. This may include measures such as drainage improvements, flood mitigation works, planning controls or community education.
The findings are used to prepare a Flood Risk Management Plan, which helps Council prioritise actions based on their cost, feasibility and the benefits they provide to the community.
Completing this process in accordance with the NSW Flood Risk Management Framework may also help secure government funding for future flood mitigation projects.
Figure 1. The Flood Risk Management Program
This process is completed once a Flood Risk Management Plan is completed, we review old Studies and Plans to update them with the latest information and review how effective they were and make any new recommendations on how to further reduce flood risk.
Flood studies use different flood events to understand the likelihood and consequences of flooding.
The most commonly used event is the 1% Annual Exceedance Probability (1%AEP) flood. This is a flood that has a 1 in 100 chance of occurring at any time.
We use this to determine a Flood Planning Area (FPA) which uses the 1%AEP flood level and adds a 'freeboard' allowance, which provides an additional margin of safety to reduce the likelihood of a home or business becoming flooded.
We also use the Probable Maximum Flood (PMF) which represents the largest possible flood event that could occur in a particular area. While extremely rare, the PMF is used to understand the maximum extent of flooding and identify risks to life and critical infrastructure during extreme events.
Council’s stormwater system includes drains, pits, pipes and open channels. Like all underground drainage, it is designed to handle smaller, more frequent rain events so people aren’t dealing with puddles every time it rains. During larger storms, the system cannot capture all the water. When this happens, excess water flows over the ground, this is 'overland flow'. Roads and valleys are often the main paths that this water follows, and open channels can often manage larger flows, but these cannot be placed everywhere.
It is not always possible or cost-effective to upgrade the drainage system to handle every storm. However, Flood Studies help identify problem areas where improvements may be needed. Follow up Flood Risk Management Studies & Plans can then assess whether upgrades to drainage could reduce flooding and improve safety.
Ideally, excess water flows along roads, through parks or along drainage easements. However, water will always follow the lowest points in the landscape. These low areas are often where natural creeks or drainage paths existed before development.
Flood behaviour can change over time as new studies, improved modelling techniques and additional survey information become available. As a result, areas identified as being affected by flooding may change as flood studies are updated.
A property may be identified as flood affected if it is located within the Flood Planning Area (FPA)*, an area used to help guide planning and development. The FPA applies development controls to protect future development of all kinds from the known risks of flooding on a Lot.
The Flood Planning Area sits within the broader Probable Maximum Flood (PMF)* extent. This very rare event is used primarily for emergency planning purposes. However, controls are applied for sensitive developments including where vulnerable populations who cannot easily evacuate or respond to emergencies are located. For example, childcare, aged care, health services, or educational facilities. Hazardous facilities that may pose an environmental risk if flooded are also subject to controls.
Being in either the FPA or PMF extent does not prevent development and importantly, only the part of a Lot identified as affected by flooding are considered when planning development.
A 'Lot' is the area of land within the boundaries shown on a land title.
Some lots have a single home or business, while others may contain multiple separately owned units, apartments, villas, townhouses or businesses.
Flood studies generally assess flood risks based on the lot because buildings and land use can change over time. This provides a consistent way to understand and manage the flood risk now and into the future.
Property values are influenced by a broad range of factors. There is no clear evidence that the adoption of overland flow information on its own would result in a sustained impact on property values.
Each insurance provider has its own risk assessment process used to set premium prices. The Insurance Council of Australia advises that insurers already hold extensive flood risk data. The industry has developed the National Flood Insurance Database (NFID), which insurers use to assess flood risk. In determining insurance premiums, insurers consider NFID data alongside other factors, including building type, location, and claims history.
We cannot rule out that Council's revised draft Overland Flow - Flood Study could impact premiums, however, it is likely it provides more accurate detail than studies conducted by an insurance company.
The standard insurers' definition of flood in Australia is defined in the Insurance Council of Australia's General Code of Practice as:
The covering of normally dry land by water that has escaped or been released from the normal confines of: any lake, or any river, creek or other natural watercourse, whether or not altered or modified; or any reservoir, canal or dam.
Overland flow does not fit into this definition and is sometimes considered as ‘stormwater’ by insurers. However, it is recommended that you speak with your insurer for a full understanding of policy coverage and other types of flood risk at your property.
Further information on flood insurance is available from the Insurance Council of Australia:
Flood insurance explained - Insurance Council of Australia
Floodplain Management Australia partnered with the Insurance Council of Australia in developing three factsheets on flood insurance:
Being in either the Flood Planning Area (FPA)* or Probable Maximum Flood (PMF)* extent does not prevent development and importantly, only the part of a Lot identified as affected by flooding are considered when planning development.
If your property is identified as flood affected, additional planning and design requirements may apply to ensure the development can safely withstand flooding and does not increase flood risk for neighbouring properties.
These requirements are outlined in Chapter 40: Environmental Risk – Flood Risk Management of the Sutherland Shire Development Control Plan (DCP). Depending on the type of development and the nature of the flood risk, considerations may include floor levels, building design, structural resilience, vehicle access and evacuation.