Have Your Say on
Flooding in Your Area

We need your knowledge on flooding in your area
On behalf of Hunters Hill Council, GRC Hydro are undertaking the Hunters Hill Local Government Area (LGA) Flood Study. We would like to hear your experiences of flooding to better understand how flooding occurs in your area .

This study will define the existing conditions pertaining to flooding in your LGA. This study will be used by Council to manage flood risks in your area.


What is the Floodplain Risk Management Program?
The Floodplain Risk Management Program is run by the NSW Government. This program helps councils make informed decisions about managing flood risk, implementing management plans to reduce flood risk and to provide essential information to the SES to deal with flood emergency response.

This program consists of five stages and the current study will undertake the first two stages of this process; Data Collection and Flood Study.

The stages of the Floodplain Risk Management Program are presented below:


What is Flooding?
Flooding is often associated with inundation from large rivers; however, there are other flood mechanisms that can cause inundation. The Hunters Hill LGA is primarily affected by two types of flooding; overland flow flooding and mainstream flooding.
Overland Flow
Flooding

Overland flow flooding occurs as rainfall runoff moves toward downstream waterways.


Mainstream
Flooding

Creek flooding occurs when runoff from streets and drains flows into waterways causing them to rise and inundate areas that are usually dry


What is a flood study?
A flood study is a comprehensive technical investigation of flood behaviour. This study will define the nature of flood risk in the LGA by providing information on the extent, level and velocity of floodwaters for a full range of flood magnitudes up to and including the largest possible flood, termed the ‘Probable Maximum Flood’.

A commonly used outcome from a Flood Study is the 1% AEP flood result (also known as the 1 in 100 year flood). Sensitivity testing is also undertaken in these studies to account for factors such as climate change and blockage of drainage systems.


What is a flood study used for?
Flood studies provide key information for Council, the SES and the community and are part of the process to manage an area’s flood risk.

For Council, flood studies are primarily a planning tool for future development in the LGA. Examples of applications for Council are listed below:
  • to ensure that sensitive infrastructure (such as childcare centres and nursing homes) are not built on flood prone land; and
  • to ensure that development does not increase the flood affectation on neighbouring private property.


Information from the flood study will assist the SES in its evacuation and logistics planning. The outcomes of the study will provide the SES with:
  • a clear description of flood behaviour in the study area for a full range of flood events;
  • a description of flood warning times for the LGA; and
  • identification of critical evacuation issues in the LGA such as locations where road access is cut and the warning time before road access is cut.



The Study Area
The Hunters Hill LGA covers a 6 square kilometre area with two key creeks (Tarban Creek and Brickmakers Creek) that flow through the LGA and into the Lane Cove River and Parramatta River respectively. These creeks are shown in the map below.

Anecdotal evidence indicates that flooding from overland flow occurred in the early 1990s.

Any information that the community can provide on historic flooding will be welcomed.


Why your feedback is important
GRC Hydro will develop computer models to determine the existing flood affectation in the area. Calibration and validation is a key phase in the development of these models. This process ensures that the modelled flood behaviour accurately reflects the flood behaviour in reality. As such, community input and knowledge of historical flood affectation is invaluable to this study.


How you can help us
Your feedback is important in helping us get a complete picture of flood behaviour in your LGA and how this affects your community. Please share your experiences and knowledge with us by completing the questionnaire linked below.


Who can you contact for more information?
If you have any further questions regarding the flood study or any further flood information or photos, please attach them to your questionnaire or contact the following representatives.


Beth Marson
Senior Engineer, GRC Hydro
[email protected]
0409 833 039


Jacqui Vollmer
Bushland Coordinator, Hunter’s Hill Council
[email protected]
(02) 9879 9400


The Hunters Hill
Flood Study Questionnaire