Background

Under the NSW State Government’s Flood Prone Land Policy, all local councils are required to undertake a periodic review of Flood Studies and Floodplain Risk Management Studies. Georges River Council (GRC), with financial and technical support from the NSW Department of Climate Change, Energy, the Environment and Water, have recently commenced the Blakehurst and Kogarah Bay Wards Overland Flood Study.

To prepare the Overland Flood Study, Georges River Council has engaged an independent consultant specialising in floodplain management and flood studies.

The study area (Figure 1) includes the suburbs of Allawah, Blakehurst, Beverly Park, Carlton, Carss Park, Connells Point, Hurstville (part), Hurstville Grove, Kogarah, Kogarah Bay, Kyle Bay, Mortdale (part), Oatley (part), Penshurst (part), Ramsgate (part), Sans Souci (part), and South Hurstville.

Fig: Study area

About the draft study

This Overland Flood Study represents an important step in the floodplain risk management process, whereby Council will gain a comprehensive technical understanding of the nature of flooding within the study area using advanced computer modelling software and community feedback.

The aim of the draft Overland Flow Flood Study is to identify the nature and extent of catchment overland flooding, which is generated by rain events where drainage systems quickly reach capacity and excess rainfall flows overland. This information is crucial to keep people and property in our community safe from the impact of severe rain which causes 'overland' or 'flash flooding'.

The aim of the Overland Flood Study is to:

• Define the nature of overland flooding using the most current information and technologies.
• Improve understanding of flood behaviour and associated flood risk across the study area.
• Build community resilience by informing better planning of development, emergency management and community awareness.
• Develop information to assist in future floodplain management activities to reduce flood impacts on the community and risk to life.

Blakehurst and Kogarah Bay Wards Flood Study will prepare flood mapping across the study area including the number of lots that are "Flood Tagged". Flood tagging is a process of identifying property parcels that are at risk of overland flooding and may be subject to appropriate flood-related development controls. This is to ensure that new developments are adequately protected and do not make flooding worse. It is noted that the flood-related development controls are applicable for a new development or addition/alterations to an existing building.

Key Stages of the Preparation

• Stage 1: Data Collection, gap analysis and Community Survey - We are here.
• Stage 2: Hydrological and Hydraulic Model Development and Validation.
• Stage 3: Design event modelling, model simulations and mapping.
• Stage 4: Draft Flood Study Report.
• Stage 5: Community Consultation.
• Stage 6: Final Flood Study Report.

Following the completion of this study, subject to the availability of funding, Council will undertake the Floodplain Risk Management Plan, which uses the results of the Flood Study as the foundations for developing flood risk mitigation options. This typically involves infrastructure projects, development controls and emergency management practices.

How to be involved

Community involvement is essential to the success of the floodplain risk management process. It enables the community to:

• Contribute local knowledge of flood behaviour.
• Directly influence the calibration and validation of flood models.

Council is seeking input from the community to help provide a better understanding of overland flooding in the area. By sharing your local knowledge and personal experience, you will help us to identify key flooding concerns, issues, and 'flood hot spots'.

Council is calling on the community to complete a short questionnaire. The community's responses to the questionnaire will help identify key flooding concerns or issues and gain information relating to recent rainfall events including April 2015, March 2022 and February 2023.

We would appreciate your participation in this study by completing the short questionnaire by 7 March 2024.

If you are willing to respond, please complete and return the attached questionnaire to Council.

	Complete our online form, or
	Return a hard copy submission.

If you are returning a hard copy submission, please quote SF24/27 Public Submission - Blakehurst and Kogarah Bay Wards Flood Study at the beginning of your submission and return:

	In person to Georges River Council Civic Centre or Libraries
	Via email: mail@georgesriver.nsw.gov.au
	Via post: PO Box 205, Hurstville BC NSW 1481

Next Steps

We will review all responses received and compile all flood-related information for the area. This information received will inform calibration of computer flood models to reproduce historic floods and validation of the computer-generated flood modelling outputs. A draft Flood Study report and mapping will be produced, summarising the outcomes of all phases of the investigation.

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