By Sophie Aubrey and Clay Lucas
Major developments on the Maribyrnong River floodplain, including part of the Metro Tunnel project, may have contributed to last year’s disastrous floods upstream.
The Metro Tunnel in Kensington is protected by a flood wall large enough to withstand a one-in-1000-year deluge and is one of a number of projects built on flood-prone land along the Maribyrnong River that experts say could have exacerbated last October’s deluge.
The green flood wall in Kensington protecting the rail tunnel behind it.Credit: Eddie Jim
The tunnel’s 350-metre-long flood wall rises to three metres and was originally designed to work in tandem with almost one hectare of land that would soak up floodwater that had nowhere to go once the wall was built.
But the land set aside to take this water was later downgraded to an area covering just one-fifth of that, with Melbourne Water’s consent.
More than 600 properties were inundated in last year’s floods; 525 of them in the suburb of Maribyrnong and the remaining homes and businesses in Kensington, Ascot Vale and Avondale Heights.
Experts noted the rail tunnel was one of a number of large-scale riverside developments that could have also altered the hydrology of the Maribyrnong catchment, along with the state government’s West Gate Tunnel project, Flemington Racecourse’s controversial flood wall and housing developments.
These developments were also given the green light by Melbourne Water with extensive flood barriers or other forms of mitigation.
Hydrology expert Geoff Crapper, who worked at Melbourne Water, said it was not clear the water authority had conducted systematic flood mapping before approving many of these projects, in particular the Metro Tunnel flood wall in Kensington.
“I would like to know on what basis Melbourne Water reduced the flood mitigation measures for the tunnel flood wall,” Crapper said.
Civil engineer Ron Sutherland was manager of land development at Melbourne Water until he left in 2002. Asked about development in the catchment, Sutherland said flood walls were often a bad idea.
“Walls will divert flows, so generally it will cause more water to be diverted into areas that originally did not cater for the higher flows,” he said.
Aerial images along the Maribyrnong River over the past 20 years show construction of thousands of new homes — with each leaving the landscape less able to soak up water and the subsequent run-off pouring into the river.
University of Melbourne Associate Professor Brian Cook earlier this month said there should be a moratorium on development on floodplains. “We’re encroaching into floodplains in little bits, nibbling at the edges, and that’s putting things in harm’s way and reducing the capacity of the river,” he said.
Liberal MP David Davis told parliament last week that planning decisions on the Maribyrnong River floodplain were potentially exacerbating flooding.
“You should not expect communities to be confronted with a flood event that has been caused in part or in whole by planning decisions that have been made foolishly,” he said.
The $12.6 billion rail tunnel’s western entrance sits on land in Kensington that was protected in last October’s flood.
Flood protection is essential for the rail tunnel, but its construction in Kensington may have had consequences for homes and businesses nearby, and elsewhere on the Maribyrnong River.
Studies completed in 2016 to assess the tunnel’s environmental effect noted its construction could increase flood levels upstream and downstream, and that compensatory flood storage of 9000 cubic metres – roughly the entire MCG playing surface at a depth of half a metre – would be required.
Flooding in October in Kensington. This photo was taken 250 metres from where the new Metro Tunnel flood wall has been built.
This requirement was revised down to 2100 cubic metres, in consultation with Melbourne Water, and a flood storage area established on land next to the river in Kensington.
Melbourne Water guides development on metropolitan floodplains. A spokesman for the authority said the decision to revise down the land needed to offset the floodplain taken by the Metro Tunnel was made using a range of information and data.
A Rail Projects Victoria spokeswoman said the Metro Tunnel project had undergone a thorough planning assessment to assess and mitigate the impacts on surrounding neighbourhoods.
Kensington resident Denise Jury’s apartment is in a building flanked by Flemington Racecourse upstream and the Metro Tunnel entrance downstream.
Kensington resident Denise Jury and dog Dougal walk past the Metro Tunnel flood wall in Kensington.Credit: Joe Armao
The building’s basement flooded in October, destroying residents’ cars and belongings held in storage cages, despite it being built to withstand a one-in-100-year flood.
She questioned the effect of major works like the Metro Tunnel on flood levels. “Have they actually taken sufficient due diligence to ensure local properties aren’t unduly affected because of its presence?” she said.
At a recent public forum on the Maribyrnong flood inquiry, Melbourne Water strategic projects manager Liz Nairn said the authority’s input was crucial to a project proceeding.
“Our advice is extremely important. It often can make or break an approval or a refusal decision,” she said.
Denise Jury’s apartment building in October’s flood.Credit: Denise Jury
Failures in the flood early warning system and planning decisions, revealed by The Age, have led to concerns about the independence of a Melbourne Water review into the flood.
Those concerns led to state parliament’s upper house last week passing a motion to hold a parliamentary inquiry into October’s floods.
A community petition pleading for the government to build flood prevention for the suburb of Maribyrnong has attracted more than 2000 signatures.
Madeleine Serle, whose Maribyrnong home was smashed by October’s flood, criticised the inconsistency of millions of dollars being poured into protecting only some sites.
“However, for me and thousands of other residents… no mitigation, and no plans for mitigation,” she said.
Greens deputy leader Ellen Sandell said successive state governments had a “scattergun approach” to planning that meant some selected sites were protected from floods while many residents were left vulnerable.
The Andrews government has rejected building a dam or retarding basin to protect the suburb of Maribyrnong from future severe flooding.
Water Minister Harriet Shing’s spokeswoman said the government would await the recommendations of Melbourne Water’s review before making any decisions relating to flood management.
A flood immune 9.1-metre building at the Metro Tunnel site in Kensington.Credit: Marcus Wong
Victorian MP David Ettershank, representing the Legalise Cannabis Party, is a Kensington resident who was heavily involved in the fight against the Flemington Racecourse flood wall built in 2007, and was also later involved with discussions about the Melbourne Metro Tunnel.
Ettershank was concerned some floodplain developments were being granted protection while flooding continued to affect residents and traders outside those sites.
“We have no confidence that the Melbourne Water inquiry into Melbourne Water will address those issues,” he said.
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