Addendum to the Ballina Flood Study Update 2023 - Flood Function Mapping

At the September 2026 ordinary meeting, Ballina Shire Council resolved to place the Draft Addendum to the Ballina Flood Study Update 2023 on public exhibition.

Adopted by Council in 2025, the Ballina Flood Study Update 2023 provides updated flood information for a range of design flood events, expressed as Annual Exceedance Probability (AEP), and improves Council’s understanding of flood behaviour, flood impacts and flood risk across the shire.

The Draft Addendum to the Ballina Flood Study Update 2023 includes flood function mapping that was not originally included in the mapping adopted by Council.

The addendum does not replace the adopted flood study. Its purpose is to append flood function mapping to the adopted study so that Council has clearer information to support development assessment, land use planning and future flood risk management work.

Floodplains naturally convey and store floodwater. Understanding these functions is important when assessing development on flood-prone land because works such as filling or constructing structures that block flows can influence how floodwater moves through the floodplain and may increase risk to other properties or the broader community.

Flood function is classified into three categories:

• Floodways – convey a significant portion of floodwater and are sensitive to changes that affect flow.
• Flood storage areas – influence flood behaviour by storing large volumes of flood water in the floodplain.
• Flood fringe areas – within the flood extent but outside floodways and flood storage areas, and are less sensitive to changes in flow or storage.

The mapping has been prepared by examining the depth and velocity of floodwater in the flood model. Faster and deeper flows have generally been mapped as floodways; deeper slow-moving or stationary water has been mapped as flood storage; and shallow slow-moving or stationary water has been mapped as flood fringe.

This mapping helps Council identify sensitive parts of the floodplain when assessing development applications and planning proposals. In particular, it will assist planners and engineers to consider whether proposed works are compatible with flood function and behaviour

Flood function mapping is also an important constraint for strategic land use planning and urban expansion. Development or filling in floodways can affect flood behaviour and should generally be avoided. Larger-scale filling in flood storage areas can also have cumulative long-term impacts on flood levels and needs to be carefully considered.

The flood function mapping can be viewed in the Draft Addendum to the Ballina Flood Study Update 2023 and on Council's online mapping portal.

Have your say

Council is now seeking community feedback on the draft flood function mapping. Please view the draft addendum and mapping before completing the feedback form below.

Submissions close 20 November 2026.

Submissions received will be reported to Council before the addendum is finalised and used to inform future flood risk management studies and plans.