North Sydney LGA Wide Flood Study

October 2019 

GRC Hydro, on behalf of North Sydney Council, are undertaking the North Sydney Local Government Area (LGA) Floodplain Risk Management Study & Plan.

We would like to hear your experiences of flooding to better understand how flooding occurs in our area and what measures may improve the current flood situation.

This study and plan will identify and recommend appropriate actions to manage flooding in the LGA.

This study will be used by Council to manage flood risks in your area.

For further information on the questionnaire, and the Floodplain Risk Management study, please go to http://www.grchydro.com.au/northsydney.html.

Your feedback is important in helping us get a complete picture of the community’s knowledge of flood behaviour and mitigation in the LGA.

You can upload your experiences and knowledge by filling out the questionnaire online.

Or download the questionnaire and email it GRC Hydro Flood Questionnaire (357KB)

 

Background 

North Sydney Council and the NSW Government, as part of the Floodplain Management grant, has completed the North Sydney LGA Wide Flood Study 2016 to begin the process of identifying flood prone land in accordance with the NSW State Government's Floodplain Development Manual.

The next stage of the study is the floodplain risk management study and plan (FRMS&P) this is currently underway and due for completion in June 2020.

A flood study is a comprehensive technical investigation of flood behaviour which defines 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.

A FRMS&P draws on the results of the flood study to identify, assess and compare various flood risk management options and opportunities aimed at improving the existing flood situation in the LGA. It provides information and tools to allow considered assessment of flood impacts, the management options, plus provides a strategic plan for implementation.

Management options are typically categorised as property modification measures, response modification measures, and flood modification measures.

 

floodplain_flowchart.jpg
 
 
2. Flood Study is the second step in the floodplain management process.

3/4. Floodplain Risk Management Study & Plan underway - completion due June 2020.

 

 

What is Flooding?

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

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

grchydro_overlandflow_5.gif

 

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

grchydro_creekflooding_5.gif

A FRMS&P provides key information for Council, the SES and the community for effectively managing and mitigating flood risk.

For Council, FRMS&P’s are primarily a planning tool for future development in the LGA and implementing flood mitigation measures for existing development areas. Examples of applications for Council are listed below:

  • examination of Council’s local flood risk management policies, strategies and planning instruments; and
  • identification and assessment of floodplain risk management measures for existing development areas aimed at reducing social, environmental and economic loss of flooding on development and the community.

Information from the FRMS&P 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.

If a property is identified as being located within the Flood Planning Levels, this means that flood-related development controls may apply for future development applications. Please note that individual properties have not yet been tagged in the Section 149(2) Planning Certificate. This next step will be undertaken as part of the upcoming Floodplain Risk Management Study and Plan. Individual property owners will be consulted prior to this change occurring.

The Flood study is available to download here:

Flood Study document (39MB)

Figures 18 to 23 - Peak Flood Depth and Contours (192MB)

FAQ (158KB)

 

Flood Insurance Fact Sheets

Insurance fact sheets - www.floods.org.au/site/flood-insurance-fact-sheets

 

Community information sessions held August 2016

WMA Water presentation (6MB)

OEH presentation (1MB)

 

Further Information

Should you have any queries or require further information please do not hesitate to contact Jim Moore, Engineering Project Manager, on 9936 8100 or email floodstudy@northsydney.nsw.gov.au

Posted on 4 October 2019

Back to Listing
waterripple2.jpg