Living in a beautiful coastal area traversed by creeks and dotted with coastal lagoons comes with the risk of flooding. Northern Beaches Council continues to undertake a program of studies and investigations to identify the areas at risk of flooding and how this can be managed.   

Types of flooding

Floods can be dangerous. You should never enter flood waters. There are two kinds of floods that occur naturally on the Northern Beaches: flash floods and lagoon flooding. 

Flash floods

Flash floods occur when heavy rainfall causes creeks to break their banks or the stormwater network to exceed its capacity and overflow. Flash floods happen suddenly with little or no warning and recede relatively quickly.

Lagoon flooding

Lagoon flooding occurs when creeks and stormwater networks drain into lagoons during major storms. The lagoons rise from rainfall runoff and ocean swells resulting in flooding of the area around them. Water levels drop when flood waters can escape through the lagoon entrance. Tides and wave movement play a significant part, and this may take a long time.

Further information on the opening and closure of coastal lakes and lagoons can be found at Department of Primary Industries 

What we do to reduce flood risk

Council follows the NSW Government’s floodplain risk management process to identify and manage flood risk.  This is a four stage process resulting in an adopted plan for managing flood prone land:

  1. Flood Study – identification of flood risk
  2. Floodplain Risk Management Study – identification and assessment of a range of floodplain management options to reduce flood risk
  3. Floodplain Risk Management Plan – a comprehensive plan setting the strategic direction for the management of flood prone land through the implementation of a range of options
  4. Implementation of Floodplain Risk Management Plan – implementation of floodplain management options in accordance with priority and financial constraints.

Flood Hazard Map

Council's Flood Hazard Map shows the extent of land identified as flood prone throughout the Northern Beaches. You can enter your property's address to zoom in to that address.

Flood affected areas are divided into three precincts:

The Medium Flood Risk Precinct is equivalent to the Flood Planning Area, and covers all flood prone land which is affected by the 1% Annual Exceedance Probability (AEP) flood (equivalent to the 1 in 100 year flood) with a freeboard added.

The High Flood Risk Precinct lies within the Medium Flood Risk Precinct, and covers flood prone land which is subject to a high hydraulic hazard.

The Low Flood Risk Precinct covers flood prone land affected by the Probable Maximum Flood (PMF) but which is outside the Medium Flood Risk Precinct. The PMF is equivalent to the largest ever conceivable flood.

None of these mapped extents include climate change.

Planning controls for flood prone areas

One of the principal recommendations for managing flood risk is the adoption of planning controls for flood prone areas. Planning controls, sometimes known as flood related development controls, include the setting of floor levels above known flood levels. These ensure the end use of a development is compatible with the known flood hazard.

Planning controls can be found in the Development Control Plan (DCP) and Local Environment Plan (LEP) on the Planning Rules page.

Please note that at its meeting on Tuesday 15 December 2020, Council resolved to adopt minor amendments to the flood planning requirements, and these came into effect on 18 January 2021.

Northern Beaches Flood Information Network

Northern Beaches Council in conjunction with the State Emergency Service and Manly Hydraulics Laboratory have established an innovative online flood warning system for the region. 

The system involves the installation of a number of rainfall and water level gauges that provide live data on where and when flooding may occur, lagoon levels, weather warnings and any recent or forecast rainfalls. 

What you can do to protect your home and family

If your property’s on flood prone land be prepared and vigilant. Use the online flood warning system for up-to-the-minute news on current rainfall, flood warnings and safety advice.

Also, the SES FloodSafe website can alert you on flooding in your area.  Call for emergency help in flood, storm and tsunami on 132 500.

Flood Studies

Flood studies improve our understanding of flood behaviour, in particular the speed and depth of flood water, and to identify problem areas. 

Flood Study Documents

View the list of council flood study documents.