A flood researcher has raised alarm over “wild west” infilling of Bangholme’s retarding basin after Willow Lodge retirement village was flooded on Tuesday 16 July.
The village of more than 500 residents is on floodplains between the banks of Eumemmerring Creek and Eastern Contour Drain, and downstream from a Melbourne Water retarding basin.
The complex is surrounded by a ring of flood-protection levees as well as a retention pond.
Last week, residents watched anxiously as waters escaped the retention pond and rose under at least six elevated homes. Further homes had their backyards inundated.
“The creek is right up around us,” a resident told Star Journal.
“The retention pond is rising and the pumps are working overtime but are not keeping up.”
Fortunately, the rains stopped and the water levels subsided that afternoon. But the resident wanted answers on the cause of the overflowing pond.
Star Journal enquired with three authorities but each blamed the other for an apparent backflow issue at a nearby floodgate on 16 July.
A message from Willow Lodge alerted residents that a Melbourne Water floodgate was causing backflow issues.
However, Melbourne Water later stated it was City of Greater Dandenong’s infrastructure.
Greater Dandenong then adamantly pointed the finger at Department of Transport and Planning, and the department pointed it back to Melbourne Water.
Three days later, Greater Dandenong councillor Rhonda Garad said the council’s head engineer advised that different authorities were managing the basin’s three floodgates.
On one side was Melbourne Water’s gate, on the other was the transport department’s gate.
Last Friday afternoon, transport department workers were still working at their floodgate, which was blocked from opening due to debris, Cr Garad said.
In February 2011, Willow Lodge residents were evacuated during a massive flood event.
Bangholme flood researcher Alan Hood warns of frantic future evacuations at Willow Lodge if floods equivalent to several in the past 100 years were repeated.
At those levels, a rampaging Dandenong Creek would spread about 1.7 kilometres wide, would “roof gutter height” at Hammond Road and would “slam over” the Eumemmering Creek northern levee bank towards Willow Lodge.
“The people of Willow Lodge would need to be evacuated. But there would be no vehicular access from north or south… helicopters can’t do it fast enough.”
Mr Hood was alarmed about infilling of the Bangholme Retarding Basin just north of Eumemmerring Creek and Willow Lodge.
“The question is who approved the retarding basin to be filled so it can’t work to protect Bangholme, Carrum Downs, Seaford and Frankston from loss of homes.
“EastLink built a bridge over the retarding basin for safety but it’s been wild west from EastLink to Frankston-Dandenong Road.”
The filling had “quietly progressed westwards” up to paddocks at 250 Fernside Drive – a site which has been controversially proposed for rezoning for industrial development.
A week earlier, Cr Garad raised the alarm on behalf of Willow Lodge residents on the proposed rezoning.
At a 8 July council meeting, Cr Garad said the site was within the “Bangholme retarding basin” – a “critical” flood mitigation measure to protect residents at Willow Lodge retirement village as well as suburbs downstream.
According to a council report, Melbourne Water has stated it doesn’t have any objection to the rezoning on the basis of flood risk, “subject to conditions”.
Councillors sought a costings report on getting independent advice on the flood impact.
As for the 16 July incident, Mr Hood said rainfall levels and Eumemmerring Creek outflows shouldn’t have caused flooding of parts of Willow Lodge.
“It wasn’t an external flow. It was self-inflicted.
“A drainage ditch has been cut which runs all around Willow Lodge and a drain built down through the levee bank to drain stormwater from Willow Lodge into the creek.
“But it either didn’t have a flow valve, or the flow valve was stuck open.
“Water was flowing into the drainage ditch and around the back to the pumps, which were slowly draining the sump. The pumps were going but were nowhere near enough for such a big volume.”
