Brisbane Water Floodplain Risk Management


Brisbane Water ForeshoreDraft Floodplain Risk Management Study


'This project was supported by the NSW Government’s Floodplain Management Program.'


Characteristics and value of the Brisbane Water floodplain

The Brisbane Water estuary has only a small catchment of 165km2 with the main water body being 28km2.

The catchment has undergone extensive rural, residential and industrial development, however natural forest still covers about 50% of the total catchment area.



The catchment is partly urbanised with major concentrations of development centred in Gosford in the north and the region of Umina beach, Ettalong beach and Woy Woy in the southwest.

Other smaller residential areas including Green Point, Kincumber, Saratoga, Davistown, St Hubert’s Island, Killcare and Pretty Beach are scattered along the eastern parts of the catchment.



The Brisbane Water foreshore represents the interface between aquatic and terrestrial habitats.

Environmental values

These include bushland, wetlands, salt marshes, Casuarina forests, mangroves, mudflats to seagrass beds, submerged rock platforms and sandy or muddy estuarine beds.



The recreational uses of Brisbane Water estuary and foreshore include a range of activities such as swimming, bushwalking, boating, picnicking, recreational fishing, foreshore parks and playgrounds, cycling and bird watching.

Recreational values



The economic value of Brisbane Water includes the value of private dwellings, public infrastructure and the income provided through tourism and recreation.

Economic valuesOver 250,000 dozen Sydney Rock Oysters were produced in Brisbane Water in

2007/08, with a total value of $1.3million.


As has occurred with many coastal cities and towns around Australia, many suburbs of Gosford have been built successively within the local floodplains.

Flooding and the risk management process

This has been evidenced in the recent flood events in Gosford during the mid to late 1980’s, early 1990’s and June 2007 when many properties were flooded.


What is a floodplain?A floodplain is an area of land that has been formed by flooding over time and is still subject to periodic inundation. Floodplains are also referred to as flood prone land. Floodplains or flood prone land is all land affected by flooding up to and including the Probable Maximum Flood (PMF) event (or the highest conceivable flood that nature can produce).

What causes floods?Flooding is defined as a relatively high water flow that overtops natural or artificial banks in any part of a stream, river, estuary, lake or dam resulting from:• heavy or prolonged rainfall and/or • super-elevated sea levels and/or • waves overtopping coastline defence.


What is a floodplain?A floodplain is an area of land that has been formed by flooding over time and is still subject to periodic inundation. Floodplains are also referred to as flood prone land. Floodplains or flood prone land is all land affected by flooding up to and including the Probable Maximum Flood (PMF) event (or the highest conceivable flood that nature can produce).

What causes floods?Tidal action, such as King Tide and storm surge which is generated by storms off the east coast of Australia, are also very common causes of flooding in the Gosford Region which cause flooding within the Brisbane Water estuary and along the coastal foreshore areas.


How are floodplains managed?Local government is primarily responsible for control of development on flood prone land. However, the NSW State government, the State Emergency Service and the Bureau of Meteorology also have a major role to play in managing the flood risk. The State government provides specialist advice and financial support to assist councils to develop Floodplain Risk Management Plans which consist of the following stages:

Form a Floodplain Risk Management Committee

Collect data Flood Study preparation

Floodplain Risk Management Study preparation

Floodplain Risk Management Plan preparation

Implementation of the Plan

Review the Management Plan


We are currently at this stage:

Floodplain Risk Management Study preparation

The purpose of a Floodplain Risk Management Study is to identify, assess and compare various risk management options and consider opportunities for environmental enhancements as part of mitigation works.


The following options have been investigated and assessed for feasibility as part of the floodplain management process.

Immediate Options that could be implemented in the short term. Feasibility is generally high and additional investigations or further development of the management strategy would be minimal and would address existing flood risk.



Staged Options that could be implemented in the short to medium term. However additional investigations, feasibility studies or further development of the management strategyare likely to be required. Where appropriate, interim policy and planning measures could be employed in the intervening time to address existing and future risk.



Trigger Options that could be implemented over the long term, generally relating to projected sea level rise. Further investigations are required and the implementation of the option would be based on a predefined sea level rise “trigger level” to indicate when implementation of the option would be viable. Where appropriate, interim policy and planning measures could be employed until the specified trigger level was reached.


The options available for the management of flood risk can be categorised according to the way in which the risk is managed. There are three broad categories:

Flood modification options are aimed at preventing or reducing the likelihood of flooding to an area by modifying flood behaviour.

Flood Modification (FM)



Property modification measures are focused on preventing and reducing the consequences of flood risks. These options aim to modify properties (both existing and future) so that there is a reduction in flood risk rather than modify the flood behaviour.

Property Modification (PM)



Emergency response measures aim to reduce the flood risks. These measures generally aim to modify the behaviour of people during a flood event.

Emergency Response Modification (EM)


These options are planned for the direct future within our lifetime.


These options will be researched as part of the Climate Change Adaptation Plan .


Join the conversation and have your say.

Join the online conversation at our forum, or fill in the surveys on any management area of your choice. Don’t forget to register or leave an email address so we can keep you up to date with this project.

Visit http://haveyoursaygosford.com.au



Talk to one of our flooding experts at Council. Share your ideas and comments, or just find out more information about the project.

Call us on 02 4304 7087



Email your ideas and comments, or ask us for more information about the project.

Email us at [email protected]



27 August 20141.30pm to 4.30pmThe Erina Centre, "The Hive" Erina Fair, Terrigal Drive, Erina.

Join us at one of our information sessionsFind out about the potential impacts of coastal flooding in and around Brisbane Water and have a say in flood management options being considered by Council.

4 September 20145.00pm to 8.00pmThe Erina Centre, "The Hive" Erina Fair, Terrigal Drive, Erina.

10 September 201410.30am to 1.30pmThe Erina Centre, "The Hive" Erina Fair, Terrigal Drive, Erina.

18 September 20142.30pm to 5.30pmPeninsula Community Centre, 93 Macmasters Rd, Woy Woy.



3 September 201411.30am to 3.30pmDavistown Progress Hall, 5 McCauley St Davistown

Join us at our drop-in eventThis drop-in event is a non-structured, informal opportunity to talk to a council officer and look at the maps and study in detail.



8 October 20144.30pm to 9.00pmThe Erina Centre, "The Hive" Erina Fair, Terrigal Drive, Erina.

RSVP for our Community forum

Come along to a community forum which will include a question and answer session with a panel of experts. Please RSVP to [email protected] or call 43047087.

Brisbane Water Floodplain Risk Management

Government & Nonprofit

Transcript of Brisbane Water Floodplain Risk Management