About the Floodplain Risk Management Process PDF Print E-mail


The NSW State Government’s Flood Prone Land Policy is directed towards providing solutions to existing flood problems in developed areas and ensuring new development is compatible with the flood hazard and does not create additional flooding problems in other areas.

Under the Policy, the management of flood liable land is the responsibility of Local Government with financial and technical support provided by the State Government. The Policy specifies a staged approach to the floodplain management proces:


Wyong and Gosford Councils have initiated this process by commissioning the Ourimbah Creek Flood Study. Once the Flood Study is completed, a Floodplain Risk Management Study and Plan will be prepared. This will quantify the benefits of implementing a range of measures aimed at reducing the damage and inconvenience caused by flooding and ensure that future development is compatible with the flood risk.

What's a Flood Study?

The first step in the floodplain risk management process involves the preparation of a Flood Study. The primary purpose of a Flood Study is to determine the nature and extent of the existing flood problem across a particular area.

A considerable amount of work is completed when preparing a Flood Study. This typically includes:

1) Collection and review of all available flood-related information for the catchment;

2) Consultation with the community to obtain additional information on historic flooding;

3) Development of computer models to simulate the transformation of rainfall into runoff and to simulate how that runoff is distributed along waterways and across the floodplain;

4) Calibration of the computer models to reproduce historic floods;

5) Use of the computer models to simulate a range of hypothetical floods ranging from relatively frequent storms right up to the largest flood that could conceivably occur (known as the 'Probable Maximum Flood');

6) Interpretation of the computer model outputs to identify the variation in flood extents, depths, levels, velocities and hazard across the catchment and to identify areas that should be preserved in the future for the conveyance of flood flows;

7) Preparation of a flood study report and maps summarising the outcomes of all stages of the investigation;

An example of some outputs that will be generated as part of the flood study is shown below. This particular image shows predicted floodwater depths and velocities during a flood that occurs once every 100 years (on average).


Why do we need to prepare a Flood Study?

Flooding in Australia is estimated to cause over $250 million worth of damage each year. Over 2,300 people have also lost their lives due to floods in Australia. Accordingly, flooding can impose significant financial burdens and place lives at risk.

The preparation of a flood study will help Wyong and Gosford Councils to understand the existing flooding problem within the Ourimbah Creek catchment. It will also help both Councils to identify were flood damage reduction measures may be best implemented to reduce the cost of flooding to the community, assist with emergency management / evacuation processes and guide future development in a way that recognises the flood hazard.


Project Contributors

Wyong Shire Council Gosford City Council

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