IT was supposed to be easier to understand, but latest Logan flood mapping has put even more properties in flood risk zones and created more confusion.
New user-friendly mapping were recently released, having been reviewed after the community felt high “one in 100 year” misrepresented their properties.
About 12,000 properties were impacted, causing oturage.
Now however, even more properties are considered at risk. New levels indicating “moderate risk” zones are higher than the previous 1:100 year level, and new low-risk zones cover thousands more properties that were previously not considered a flood risk.
There are fears that insurance companies will use the new flood maps to hike premiums, and property experts have told MyCity Logan there are developments at risk.
When new flood mapping was released a year ago, Logan City Council sent a letter to each impacted resident.
This time, they’ve instead relied on people reading their website, or tuning into council meetings.
A Chambers Flat resident of more than 40 years, who has asked not to be named, said she learned of the mapping changes on a Facebook community page informing people to check the new maps.
“I checked in October 2022 when the original information came out and nothing had changed in relation to my two hectares – two metre flood ingress on one far corner,” she said.
“But I was beyond horrified to find in this latest mapping my entire block is deemed flooded at the highest level.
“Council has never advised me.
“People are only going to find out when their insurance premium comes in.”
She said her neighbour’s property was not included in the mapping, even though it was known to flood.
At the end of last year when the mapping first changed, the Chambers Flat resident said her property was untouched by the flood zone.
But now her property is marked dark blue – meaning “high risk”.
“Flood water has never come anywhere near my property since my family purchased the block in 1977.”
Another resident Jeff Smith, has lived on the same Munruben property since 1974.
He said he was enraged to learn his land, which hadn’t been touched by flood water in the last 50 years, was now in a flood zone.
“They need to let every resident know as soon as possible, because this is going to affect so many people,” Mr Smith said.
Mr Smith’s property is now also marked “high risk”.
A Logan City council spokesperson said new “risk-based” modelling was the reason why some properties not flood-affected in the 2022 mapping are now in a flood-risk zone.
He said the new approach considered a range of potential floods with both lesser and greater chance of occurring than 1 per cent.
“… including the very unlikely but most severe possible flood in Logan,” the spokesperson said.
“This information is combined with factors about flood behaviour such as depth and speed of flow of floodwater to determine the impact and resulting level of risk.”
Council’s previous mapping detailed flood-affected areas with a 1% chance of happening in any year.
Now, under the state government’s orders, Logan’s mapping is based on a risk-based approach that includes factors such as climate change, isolation and access to critical services.
It’s more sophisticated modelling with the four risk categories: high, moderate, low and very low risk.
High-risk zones are areas with a high chance of being impacted by “deep or fast-flowing” floods; for example, 80% chance in 30 years.
Low-risk zones are areas with an “extremely unlikely” chance of flooding; 1% chance or less over a 30-year period, with relatively shallow or benign flooding conditions.
The spokesperson said the new mapping only applied to new developments.
“It does not affect existing land uses, however in some areas of risk, future expansion or changes to existing buildings or facilities may be restricted or subject to the new rules,” he said.
Council’s new flood portal – at flood.logan.qld.gov.au – was released 27 November.
Community consultation is expected to begin after upcoming council elections in March.
