Brian Matthews - Development & Projects

Flooding has once again affected Brisbane. In 2020 a wrote a series of short articles on how to check if a property floods in Brisbane and the different types of flooding. I'm sharing these again for those who may be interested in the basics. These are factual articles aimed at checking known flooding risk at the due diligence stage.

Here's Part 1 - Understanding Flooding in Brisbane

Brian Matthews on LinkedIn: Quick Overview - Part 1 of Understanding Flooding in Brisbane Flooding has once again affected Brisbane. In 2020 a wrote a series of short articles on how to check if a property floods in Brisbane and the different...

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Our mini-series on understanding flooding in Brisbane continues as we look at understanding CREEK flooding. Very similar to river flooding, but with a few differences.

Creek and waterway flooding is flooding from local creeks and waterways when the water flow exceeds the capacity of the waterway. Heavy and extended rainfall events can result in waterways becoming flooded.

In the Brisbane City Plan, creek flooding is divided into 5 ‘Flood Planning Areas’ or FPAs. I think it’s better described as levels of increasing flood intensity and risk. The levels go from 5 being the lowest to 1 being the highest.

Now like all things town planning and engineering, flood planning can be highly technical and complex. As a developer or someone who wants to develop a property, the key is for you to be able to quickly ascertain what flooding overlay may apply and what does it mean for your property.

Here are my TIPS for doing this quickly and effectively.

I’m going to abbreviate for everyone’s sake. Therefore, “Brisbane creek/waterway flood planning area 5” will simply be “Creek 5.”

Creek 5:
May flood, but unlikely. Very low risk of creek flooding. Risk increasing toward the year 2100. Generally fine with no known impact for development. There are no town planning requirements.

Creek 4:
Generally OK, with low flood risk. You should check if there are flood floor levels available in the Council Floodwise report (click here). Your development should comply with the stated levels to ensure compliance and avoid a development application.

Creek 3:
Increasing risk and likelihood of flooding. May have flooded in the past. Development may need flood engineering and assessment to demonstrate compliance with the City Plan. Important to check flood levels in the Floodwise report. Creek 3 requires a flood report for residential subdivision and industrial and most other types of development. New houses will need a 2.5m undercroft or a site specific flood risk assessment.

Creek 1 and 2:
High risk of flooding. Vital to check flood levels in the Floodwise report. All residential development will require a flood risk assessment. New houses will need a 2.5m undercroft.

When undertaking due diligence for clients, we first look at the flood overlay to understand what the mapped extent and levels are and then we consider what that means in the context of the development proposed.

Increasing risk and the likelihood of flooding. May have flooded in the past. Development may need flood engineering and assessment to demonstrate compliance with the City Plan. Important to check flood levels in the Floodwise report. Creek 3 requires a flood report for residential subdivision and industrial and most other types of development. New houses will need a 2.5m undercroft or a site-specific flood risk assessment. nt.

There are 5 types of river flooding in Brisbane. Here are my TIPS to quickly assess what impact river flooding will have on your development or property.

Brisbane River flooding is caused by water overflowing the banks of the Brisbane river. Quite simply, the river cannot hold the capacity of water flowing down it. Think 1975 and 2011 floods.

In the Brisbane City Plan, river flooding is divided into 5 ‘Flood Planning Areas’ or FPAs. I think it’s better described as levels of increasing flood intensity and risk. The levels go from 5 being the lowest to 1 being the highest.

Now like all things town planning and engineering, flood planning can be highly technical and complex. As a developer or someone who wants to develop a property, the key is for you to be able to quickly ascertain what flooding overlay may apply and what does it mean to your property.

Here are my TIPS for doing this quickly and effectively. I’m going to abbreviate for everyone’s sake. In fact, I think we can abbreviate lots of town planning terms because quite frankly most of them a ridiculously long and complex for no reason.

Therefore, “Brisbane River flood planning area 5” will simply be “River 5.”

River 5:
May flood, but unlikely. Very low risk of river flooding. Risk increasing toward the year 2100. Generally fine with no known impact for development. There are no town planning requirements.

River 4:
Generally OK, with low flood risk. You should check if there are flood floor levels available in the Council Floodwise report (click here). Your development should comply with the stated levels to ensure compliance and avoid a development application.

River 3:
Increasing risk and likelihood of flooding. May have flooded in the past. Development may need flood engineering and assessment to demonstrate compliance with the City Plan. Important to check flood levels in the Floodwise report. If your site is River 3, have a town planner check your proposal against the City Plan requirements. For land subdivision, River 3 and above will trigger flood engineering and usually require a development application.

River 2a & 2b:
High risk of flooding. Vital to check flood levels in the Floodwise report. Flood engineering required for a dwelling house and structural integrity.

River 1:
The highest mapped flood risk. Almost guaranteed to flood at some point. Not suitable for houses or residential in most cases. If in doubt, invest in a houseboat.

When undertaking due diligence for clients, we first look at the flood overlay to understand what the mapped extent and levels are and then we consider what that means in the context of the development proposed. A house, land subdivision and industrial building will all have different planning requirements.