NSW Local Governments have responsibility for identifying and then managing the risk to life and property from flooding, and have a duty of care to disclose this information to the community. Local Governments must act in accordance with the NSW Flood Prone Land Policy, which aims to reduce the impact of flooding and flood liability on individual owners and occupiers of flood prone property. One of the most important steps in this process is increasing our community’s awareness of flooding so that people are better able to understand and plan for the flood risks they face.

The draft Newport Flood Study will replace a previous flood study of the Newport Town Centre (2002) and the Pittwater Overland Flow Flood Study (2013), which was a large-scale assessment of overland flow flooding in the former Pittwater area.  

The draft Newport Flood Study Map shows land that would be affected by the Probable Maximum Flood. Properties affected by the Flood Planning Level (i.e. the 1 in 100 year flood plus freeboard) are also shaded on the map. The study area includes the suburb of Newport, part of Bilgola Plateau and a very small part of Clareville and Mona Vale.

The draft Newport Flood Study Map shows land that would be affected by the Probable Maximum Flood. Properties affected by the Flood Planning Level (i.e. the 1 in 100 year flood plus freeboard) are also shaded on the map. 

The Probable Maximum Flood (PMF) is the largest flood that can occur. It is very rare.

A 1% Annual Exceedance Probability flood event is equivalent to a 1 in 100 year flood, which is a major rain event that occurs 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. 

The Flood Planning Level (FPL) is the height used to set floor levels for houses in flood prone areas. It is defined as the “1% AEP flood level” plus an appropriate freeboard (see explanation of ‘freeboard’ below). It is used for planning purposes, and land below the FPL is considered to be flood affected and therefore subject to flood related development controls.  The FPL can be calculated as:

FPL = 1% AEP flood level + freeboard (typically 0.5m)

Freeboard is included in the Flood Planning Level as a buffer, to account for factors such as unforeseen blockages, waves from vehicles (such as SES rescue trucks), other localised hydraulic effects and uncertainties in the modelling and determination of flood levels. Freeboard is typically 0.5m above a flood level, or for some areas of shallow flood depths a reduced freeboard of 0.3m may apply.

For most people, there is nothing to do in response to this flood study, as there is no immediate change to the situation. However, property owners who are planning redevelopment of their property may need to take some additional steps as part of the consent process because flood related development controls may apply. This could include the requirement to have the floor levels of new residential development set at or above the Flood Planning Level. 

To talk with someone at Council about flooding, you can email Council at floodplain@northernbeaches.nsw.gov.au(External link) or phone 1300 434 434.

If you need specific information on flooding for a particular property you can request a Flood Information Report. 

The Flood Information Report will help you to prepare information that is needed for any future Development Application.

If there is significant rain at the top of the hill, the rain will run downhill through low lying gullies, channels and surface depressions. The speed and depth of floodwaters may be less at the top of the catchment than further down the hill, but still be significant enough to pose a risk.

Councils prepare Flood Studies and Plans according to the NSW Government’s Floodplain Development Manual (2005), and implement associated recommendations with the financial and technical assistance of NSW Government through its Flood Prone Land Policy. Land use planning through development controls is one of the most effective means of managing flood risk in the catchment. Council has implemented the Northern Beaches Flood Information Network which includes live rain gauges and lagoon water level gauges, which are used by government agencies during flood events and are publically available at: http://www.mhl.nsw.gov.au/users/NBFloodInfo/ Council has also undertaken a range of targeted flood and coastal storm awareness programs for aged-care and childcare facilities.

Council uses information from Flood Studies to design and construct on ground flood mitigation options across the Northern Beaches.

Specifically in Newport, Council has already used the computer flood model from the Newport Flood Study to investigate and design stormwater system improvements at the Crown of Newport Reserve.

The results from this study will update flood information obtained from previous studies. Most properties identified in this study as flood affected have previously been identified as subject to some level of flood risk.

Studies show that an actual flood event, rather than a flood planning notation on a Planning Certificate, is more likely to have an effect on property values. 

Individual insurance companies typically identify Flood Prone Land and assess risk through their own flood studies, analysis and flood mapping exercises, irrespective of whether Council has undertaken a flood study. These calculations are outside Council’s control. The information is then used to set policies and premiums. 

If it is a life threatening situation call 000. In the event of floods, storms or tsunamis, please contact the State Emergency Service (SES) on 132 500 or visit their website at ses.nsw.gov.au. 

The State Emergency Service has a useful website providing advice on how to manage flood risk. Visit www.floodsafe.com.au  for more information. 

Flood related development controls can be found on Council’s website, in Clauses B3.11, B3.12 and B3.13 of the Pittwater 21 Development Control Plan, and Clauses 7.3 and 7.4 of the Pittwater Local Environment Plan.

The draft Study was produced using a grant from the NSW Government Floodplain Management Program, and is two-thirds funded by the NSW Government with Council paying the remaining third of the cost. 

Council contacts:

Patrick Stuart, Senior Floodplain Management Officer, 9976 1606 or  Patrick.stuart@northernbeaches.nsw.gov.au

Duncan Howley, Team Leader Floodplain Planning and Response, 02 9942 2381 or Duncan.howley@northernbeaches.nsw.gov.au