THE severe wet weather event last week has again raised the topic of stormwater mitigation to stop the flooding of the Rosewood town centre.
Rocky McLean who lives at The Bluff said that the Rosewood township was always destined to be affected by stormwater runoff to the Western Creek and the Bremer River due to its location on flat land below Perrys Knob, Tallegalla Hill and The Bluff.
“One of the main natural streams of stormwater collecting on the southern side of the local highland rim is what we know today as Mason’s Gully, which originally ran through the town,” he said.
“Local Councils over many years including the Moreton Shire and now the Ipswich City Council progressively constructed stormwater mitigation infrastructure improvements to protect the town from stormwater inundation and damage.
“This infrastructure consists of a narrow concrete town drain which commences near Cabanda Aged Care in John Street and traverses the township in a westerly direction passing under John and Albert Streets.
“For many years, Mason’s Gully and the town drain have not been able to fully accommodate all of the stormwater flow during heavy rain, resulting in stormwater overtopping the drain and gushing down John Street.”
This has happened during many heavy rain events, including in early 2011, when stormwater was between 500 and 600 millimetres in depth in some sections of lower John Street.
“In an attempt to control much of this stormwater council constructed a stormwater detention basin above John Street and Blake’s Road to capture and to slowly release the stormwater at a maximum capacity the town drain could accommodate,” he explained.
However, concerns were raised about the detention basin when it was constructed and Rocky believes the concerns are still relevant today.
“What is the structural integrity and capacity of the detention basin, because if it does fail, Rosewood will be seriously flooded,” he said.
“The detention basin will be of no mitigation benefit if and when the basin is full and all collected rainfall and stormwater flow will exceed the capacity of the town drain, which will again result in stormwater inundation in the town.”
Adding to Rocky’s concerns, is the underground stormwater infrastructure which he said is known to be inadequate.
“Following on from council’s adoption of the, Transformation of John Street Project in 2017, regular community consultation meetings were jointly held with both the State Government, Transport and Main Roads and the Council,” he said.
“These meetings were to address the excessively high road pavement camber in the lower section of John Street and to address the inadequacies and deficiencies in the underground stormwater drainage infrastructure in John Street and Railway Street.
“Drainage standards was a topic to ensure its capability to accommodate any stormwater which may overtop the town drain and to accommodate all stormwater generated in a future redevelopment of the Rosewood town centre.
“Stormwater has been surging past manhole covers in the streets, essentially because the capacity of the single underground stormwater drainage main servicing the town centre and the street inlet pits is known to be grossly inadequate.”
Rocky recalls in 2020 a joint community discussion being held with engineers, elected representatives from council and the State Government and TMR.
“At this meeting it was said that TMR would be responsible for any works conducted in John Street and any extension to the stormwater infrastructure beyond Railway Street for all stormwater to be directed under the railway line into the Western Creek,” he said.
“Council would be responsible for any works conducted in Railway Street.
“Council would then apply for a Queensland Government Grant to upgrade the stormwater system south of John Street, in Railway Street.
“The storm water upgrade in Railway Street must be completed before TMR can complete the pavement rehabilitation and stormwater drainage works in John Street.
“TMR agreed to assist the Council with its grant application and to work with council to develop a cost estimate for upgrading the stormwater system in Railway Street.
“At this time, TMR is unable to provide a timeline for completion of the stormwater upgrade and subsequent pavement rehabilitation until the cost estimate is finalised and the council grant application and funding is approved.
“It is now March 2022, and I am led to understand that this status has not changed and has not advanced.
“Council has also not provided the community with any update or reassurances with regards to the Transformation of John Street Project, adopted five years ago.”
