THE Moreton Bay Rail link project contributed to deadly flooding in Deception Bay in May.
However, a report into the disaster that claimed five lives says the severe weather would have flooded 85 homes even if the project was not there.
On May 1, more than 300mm of rain hit the region.
Five people died as they tried to cross flooded roads.
More than 100 homes were inundated and 85 of those were in the area where the MBR contributed to the rising waters.
The MBR contributed 30-105mm of the 3900-4200mm that the floodwaters rose to in affected areas.
Snowy Mountains Engineering Corporation did an independent hydraulic review to determine what role the project played in the crisis.
The report said the MBR boosted floodwater levels by 30-105mm, depending on the area.
"It should be noted that 85 residential properties are located in the area where flood levels were increased by MBR works during the May 1, 2015 storm event," the report said.
"All of these properties would have experienced flooding on May 1, 2015 even without the influence of the MBR project works."
Rothwell had the biggest rise, with the water increasing an extra 90-105mm.
Infrastructure Minister Jackie Trad told Parliament on Wednesday that the amount of rain that fell on May 1 contributed to a one in 1000 year flood and was worse than a recent cyclone.
Ms Trad said that in the aftermath of the floods, Rothwell and Mango Hill residents were worried the rail link worsened the flooding.
"The extreme weather event experienced in south-east Queensland on May 1 was unprecedented and severe," Ms Trad said.
"More than 300mm of rail fell within three hours, making it akin to a one in 1000 year flood event.
"To put that into perspective, the rain event triggered by Cyclone Marcia in February, 2015 which caused devastation in Central Queensland was estimated to have been slightly larger than a one in 50 year event.
"No one could have predicted the severity of the storm."
Ms Trad said anyone wanting information on the report could phone 1800 823 123.
"We commissioned an independent hydraulic review to ensure that integrity and transparency was maintained in the delivery of this important project for the Moreton Bay region," Ms Trad said.
- APN NEWSDESK
What the Snowy Mountains Engineering Corporation found:
- There was no increase in flood levels upstream of Greene St, Rothwell including Major St and properties further upstream;
- Floodwater affected properties at and near Mary St, Mango Hill - 35mm of the water level can be attributed to the MBR project;
- Floodwater affected properties in McGahey St, Rothwell - 90-100mm can be attributed to the MBR Project;
- Floodwater affected properties at Anzac Ave; Rothwell - 90-105mm can be attributed to the MBR Project.
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