Draft Flood Risk Managment Study and Plan (FRMS&P)

As part of a mandated NSW-wide policy (NSW Flood Prone Land Policy) requiring all councils to help reduce the impact of flooding on communities, Hornsby Shire Council has prepared a Draft Flood Risk Management Study & Plan (FRMS&P).

This draft is based on an extensive engineering study and has undergone an independent peer review.

This Plan will assist us to:

  • Reduce the impact of flooding on the communities across the Shire.
  • Help reduce flood-related risks and potential liabilities for individual property owners and residents in flood-prone areas.
  • Reduce the loss of public assets resulting from floods.

The Draft Flood Risk Management Study and Plan (FRMS&P) sets out a strategic approach to managing flood risks across the Hornsby Shire. Accurate flood modelling is essential for effective land use planning and emergency response.

Peer Review of Draft Flood Risk Management Study & Plan

In response to community concerns, an independent Peer Review was carried out in 2024.

The independent peer review has confirmed the accuracy of the data and modelling of the Draft 2023 FRMS&P.

Flood Risk Management Study & Plan Background

Council first commissioned a Flood Risk Management Study and Plan in 2014, in line with the NSW Flood Prone Land Policy.

In 2023, Council sought feedback on the draft FRMS&P Community Consultation 2023.

Flood Definitions

Is your property on the flood map?

Please check for your property on the map below and read the additional information on Key Issues

link to Flood Risk Management Study Plan

Flood Risk Management Study HSC Flooding

1. Click the link here

2. Type the correct address in the address box

3. Impacted properties will show a blue or purple colour.

Purple = affected by 1% AEP

Blue = affected by PMF

More information

Theme number 9 - 20

Land Development Issues

  • Property is only partly affected by flood

    A property is defined by its surveyed boundaries. The land within these boundaries is called a “lot.” If any part of a lot is in a Flood Planning Area, the whole lot is called a Flood Control Lot (FCL).

  • Flood Control applied without property inspection

    Flood behavior in an area is studied using advanced computer models that use satellite data to understand how and when areas in the Shire might be affected. On-site surveys are not required.

    This practice is common across Australia for flood study and recommended as acceptable method in the NSW Government's Flood Risk Management Manual (2023).

  • Flood Control Lot Criteria

    A Flood Control Lot (FCL) in Hornsby Shire is a property identified by the flood models as being lower then the level of a 1% AEP flood.

    If your property has been identified as a Flood Control Lot (FCL) your property is either partially or fully the 1% AEP flood level in the flood model.

  • House is on high ground but still flood affected

    Flooding can happen when a river or creek overflows and floods nearby areas, known as riverine flooding. Properties on high ground may be less affected by this. However, heavy rainfall can cause flooding by water flowing over the land. This can affect any property, even those on high ground.

  • Assistance with insurance companies

    Insurance companies independently determine premiums based on their own research and data. They use their own methods to assess flood risk. We do not create Flood Studies or Floodplain Risk Management Plans for insurance companies. Council cannot assist with the insurance company's processes.

Drainage Issues

  • Insufficient drainage causing flooding

    Stormwater drainage systems are designed based on the engineering standards and knowledge available at the time. Older drainage systems may not meet current needs. Our Drainage Improvement Program monitors and identifies areas that need upgrades and prioritises projects to select high priority projects based on available funding.

    Stormwater drainage systems are designed to carry more frequent stormwater events, they are not designed to carry stormwater from 1% AEP flood event.

  • Drainage work complete - flooding status unchanged

    Flood mitigation involves taking steps to reduce the impact of flooding. It doesn’t completely remove the flood risk, so it won’t change the designation of Flood Control Lot (FCL).

  • Drainage system doesn’t change flood control

    Natural watercourses usually can't manage a 1% AEP rainfall event. Flood mapping includes pipe size and shows overland flow where pipes reach capacity. Upgrading the drainage system to handle such large floods isn't economically viable, so overland flow paths are needed. Older developments didn't include overland flow paths due to lack of knowledge about flood behavior. The current flood study aims to ensure future development considers the known flood risks including these overland flow paths.

Other Issues

  • Insufficient maintenance causing flood

    Regular maintenance of stormwater drainage system may help to reduce the impact of more frequent wet weather events. Council regularly carries maintenance work on our stormwater network. Please contact Council Customer Service team on 02 9847 6666 or hsc@hornsby.nsw.gov.au to report any issues with the drainage system.

  • Sydney Water wastewater upgrade vs drainage issue.

    In the Hornsby Shire Council local government area, Sydney Water only provides services for water supply and wastewater management. These services do not affect flood behavior in the area.

  • Councils approach for reducing flood risk

    NSW Flood Prone Land Policy requires Council to be responsible for managing flood prone land within the Shire. To do this, we have produced this plan for Hornsby. The plan looks at ways to reduce flood damage by suggesting preventive measures and responses. The goal is to lessen the impact of flooding on people and property. We also need to make sure that new developments are safe from flood hazards and do not cause flooding in other areas.

  • Not happy with consultation process by Council

    The flood study is a technical study, and Council has followed the methodology prescribed by the NSW Government's Flood Risk Management Manual (2023).

    In 2022 Council notified all properties that are at high risk of flooding. A public exhibition was held from November 2022 to March 2023, Council received over 700 submissions from residents. Council analysed all submissions and grouped them into 20 theme areas and the responses are now provided on this website.


Key Documents

We encourage you to read all the information on this page. If you still think your situation is not addressed, or is unique, please comment below.

Contact Us

​If you require further information

Contact Information
Phone 02 98474803
Email frmsp@hornsby.nsw.gov.au
In writing

The General Manager, Hornsby Shire Council, PO Box 37, Hornsby 1630.