19/01/2024

Feedback on past flash flooding events in the Blakehurst and Kogarah Bay Wards is being sought to help identify flood risks in the catchment as part of the Blakehurst and Kogarah Bay Wards Overland Flow Flood Study.

Community members with any information on past flood events in the study area are invited to contribute to an online survey, which is open until 7 March 2024.

Information sought in the survey includes photos and videos of flooding including floodwater rising from a local creek or waterway, water originating from local roads, overflow from local basins, water pooling in low points, or overflow from blocked drains or other sources.

The study area consists of a number of suburbs including Allawah, Blakehurst, Beverley 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, and South Hurstville.
The primary goal of the study is to identify the nature and extent of overland floods, or flooding generated by rain events that exceed capacities of drainage systems resulting in excess rainfall flowing over land.

While stormwater drainage is designed for minor, frequent storm events, 'overland flow paths' such as roads and valleys can maximise protection during major storms.

Georges River Mayor Sam Elmir encouraged community members within the study area to contribute knowledge or evidence related to historic floods and contribute to Georges River’s flood preparedness.

"Georges River Council recognises the importance of proactive flood planning. Your input will help identify key flooding concerns and local hotspots and contribute to the development of effective flood risk management strategies for Georges River,” Mayor Elmir said.

“We want to ensure the Blakehurst and Kogarah Bay Wards Overland Flood Study includes essential insights to ensure the safety of people and property in Georges River.

Flood mapping across the study area will also be produced, with property parcels that are at risk of overland flooding identified and “flood tagged” to ensure appropriate flood-related development controls to ensure new developments are adequately protected and do not make existing flooding worse for people and property.

This work is being undertaken in compliance with the NSW State Government's Flood Prone Land Policy and aims to enhance Council’s understanding of overland flooding - otherwise known as 'flash flooding' – and to inform future flood management solutions for Georges River.

"For property developers, better data will mean overland flood risk impacts in potential floodplains can be more easily factored into the development process, ensuring adequate controls to minimise impacts during flash floods,” Mayor Elmir said.

The study will investigate the likely impacts of a 1% Annual Exceedance Probability (AEP) flood – formerly known as a 1-in-100-year flood – which is a rare flood with a 1% chance of occurring in any year.

The flood study will also consider Probable Maximum Floods (PMF), the largest possible floods that could occur at specific locations to define the extent of the floodplain in the study area.

While extremely rare, some floods in Australia have approached the magnitude of a PMF, which are calculated to aid in the design of critical facilities and so that emergency managers can understand the maximum possible extent of flooding that could ever occur in a location and plan accordingly.
 
The study will undertake a sensitivity assessment of the flood levels due to future climate change and sea level rise in accordance with the Australian Rainfall and Runoff Guidelines.
 
Georges River Council has engaged an independent consultant specialising in floodplain management and flood studies to deliver the flood study, which will adhere to State Government guidelines and draw on the technical expertise of the NSW Department of Climate Change, Energy, the Environment and Water to ensure its accuracy and effectiveness.
 
Community members can participate in the flood study by sharing local knowledge and personal experiences through an online survey available on the Your Say engagement hub. A letter with the hardcopy questionnaire will be distributed to the households in the study area. The survey is open for feedback until 29 February 2024.
 
Georges River Council will review all community responses and compile comprehensive flood-related information for the flood study area. This data will then inform the calibration of computer flood models to accurately reproduce historic floods.

Following the public consultation phase, a draft flood study report and mapping will be produced to summarise the investigation's outcomes.

To participate, please visit Your Say page or scan the QR code below.

Those households and businesses within the study area have been sent a letter including the survey with a reply-paid envelope to support their participation.