New city-wide flood mapping is a sensitive topic, prompting backlash from thousands of impacted residents, councillors, and town planners who argue the modelling goes too far – painting dry blocks as flood prone and driving up insurance costs.
So, considering the poor optics, why has Logan City Council adopted it? And what does it actually mean for your property, beyond the technical jargon?
Flood mapping helps form part of Logan’s planning scheme, which determines what can be built around the city.
The purpose of the mapping is to stop houses, community centres, businesses and other developments from being built in flood prone areas and to keep people safe, according to the council.
The Queensland government ordered all local governments to update their planning requirements and flood mapping in 2022, following recommendations from a Commission of Inquiry into the 2011 floods.
Before the shades of blue and yellow seen in today’s map – symbolising high risk (dark blue), moderate risk (light blue) and low risk (yellow) of flooding – it consisted of a single shade of blue that was based on a one-in-100 year flood.
This map didn’t take into account factors like how deep and how fast flowing flood waters were, or projected impacts of climate change.
The new mapping, introduced in 2023 and updated twice since, considers several potential future floods, ranging from as frequent as one in 20 years (dark blue) to one in 2000 years and rarer (yellow).
These floods do not represent any historical flood event in Logan.
This is where residents, and even some local councillors, take issue.
Residents want the mapping to reflect more “realistic” chances of flooding.
Councillor Natalie Willcocks, at the most recent ordinary council meeting, said the council was being “too cautious” by including a one-in-2000-year flood and less than.
The new mapping also considers areas at risk of isolation during flooding (low and high flood islands), areas that are important for storing and moving water during a flood (high flow areas), and other areas where there has not yet been a flood-risk assessment (investigation areas).
Residents can search for their properties’ risk via flood.logan.qld.gov.au.
Here’s what your risk category means:
- Yellow (low risk): an “extremely unlikely” change of flooding (1% or less over a 30 year period) with shallow flood conditions. Development is generally considered ok, council says, unless it is for vulnerable uses like childcare centres, aged care and emergency services.
- Light blue (moderate risk): a higher chance of flooding, with conditions that may pose an “unacceptable risk” to people or properties if not mitigated through measures like resilient building design, raised floor levels and consideration of site access and evacuation.
- Dark blue (high risk): potentially life-threatening flood conditions, with an 80% chance of happening in 30 years. These waters can be deep and fast flowing. Development in this risk zone is generally not supported, particularly homes, businesses and industrial developments.
Council says the state government requires it to incorporate the risk-based approach, however, aspects of council’s policy could be changed “in response to submissions” to the draft planning scheme.
It is understood the type of considered flood events – such as the probable maximum flood or one-in-2000-year flood – is up to council discretion.
Many residents argue the modelling is flawed, targeting properties that have never seen a drop of flood water.
They say the “faulty” mapping has given insurance companies an unjustified reason to hike premiums.
Council says while the maps “may be a consideration, there are many factors driving up the value of premiums across the country, not just in Logan”.
Council says all its flood studies were completed by “qualified, independent consultants” using industry standards and guidelines, which were then peer reviewed.
Residents have until 31 October to have their say on the mapping and other aspects of the scheme.
Submissions can be made via logan.qld.gov.au/LoganPlan or by calling council on 3412 4247.
With regards to the flood mapping our already sub divided block is caught in this, meaning we can no longer build on it even tho the ground gets wet but has never flooded in the time we have owned it including after cyclone Alfred came through.