Maribyrnong residents disappointed by submissions

Melbourne Water will upgrade its decades-old Maribyrnong River flood modelling. This is after it failed to predict that a major deluge would hit hundreds of homes until just before disaster struck in October last year.

Melbourne Water will upgrade its decades-old Maribyrnong River flood modelling. This is after it failed to predict that a major deluge would hit hundreds of homes until just before disaster struck in October last year.

In a 36-page submission (submission 53), the government-owned water authority did not admit to mistakes. However, it placed some blame for the failure to adequately warn residents on the Bureau of Meteorology’s rainfall forecasts.

Melbourne Water prepared the submission for its own trouble-plagued inquiry into the Maribyrnong River flood. It was one of 62 submissions received before the March 17 cut-off and published on Friday on the flood’s six-month anniversary.

The inquiry has been mired in controversy since it was revealed it would not examine several matters, including early warning systems and urban planning.

A parliamentary inquiry was also later established after extensive reporting. The Coalition, Greens and crossbenchers teamed up to launch a wider-ranging flood review.

Melbourne Water’s submission shows it has failed to finish an investigation into the development of the Rivervue retirement village in Avondale Heights. It was on this site that 47 homes unexpectedly flooded in October.

The document also sheds no light on whether the controversial Flemington Racecourse flood wall had an impact on the October 14 disaster. This is despite its construction having been named a key focus of its inquiry following widespread community anger.

“A complex hydraulic and hydrologic model would need to be completed,” it reads. “It is usual for modelling of this kind to take at least 12 months.”

Former federal and Victorian Supreme Court judge Tony Pagone is now leading the inquiry. This is after the review’s first appointed chair, Nick Wimbush, resigned over a perceived conflict of interest.

Victoria Racing Club offers no view on Maribyrnong River flooding

The Flemington flood wall was built by the Victoria Racing Club in 2007 with a permit granted by then-planning minister Mary Delahunty. It was green-lit by Melbourne Water with mitigation works, despite being opposed by local residents and three councils.

The racing club’s submission and additional documents to the inquiry show that the structure could increase peak flood levels. Engineers investigating the feasibility of the wall during the planning stage warned that mitigating measures were necessary. Otherwise, peak flood levels in the area could increase by between 30 and 35 mm, potentially increasing flood damage.

The final engineers’ report concluded that proposed changes to a nearby road and rail bridge would more than offset the flooding impact of the wall on local properties.

The racing club’s submission offered no view on whether the wall aggravated the impact of last October’s floods on homes and businesses near the racecourse. It distanced the club’s current board and administration from decisions taken 15 years earlier.

“With the passage of time since the Flemington Racecourse flood protection was constructed, knowledge of the current board and staff is relatively limited. It has not been possible to undertake a thorough review of all potentially relevant documentation to this point in time,” the submission reads.

More than 600 properties in Melbourne’s northwest were hit in the October 14 flood. It was the worst in 48 years and the third-largest since records began in the late 1800s.

Residents deem Melbourne Water inquiry a waste of time

Submissions of residents inundated by floodwaters expressed frustration at the narrow scope of the review. Some of those residents have not yet returned to their damaged homes and slammed its perceived lack of independence from Melbourne Water. They also pointed to the lack of advance warning about the floods and the state government’s decision to approve the construction of the Flemington wall.

“I am not a hydrologist, but there were less than 20 centimetres covering our floor. The volume of water held back by the Flemington wall, if it had been dissipated over the racecourse, I believe would have saved our property and the forty-seven other properties in our retirement village,” said a resident of the Rivervue retirement village (submission 44) built on a bend of the Maribyrnong River in Avondale Heights.

Another flood-affected resident wrote: “The wall must come down.”

Maribyrnong resident Madeleine Serle expressed disappointment with the Victoria Racing Club’s submission. She is still restricted to the second floor of her home as the ground floor remains in a state of disrepair.

“I would like them to appreciate that they may have to make a change and can’t just take it for granted that they can keep this wall in place,” she said.

In her submission to the inquiry, she described the Melbourne Water review as “an egregious and misconceived” waste of time and effort. “The Maribyrnong floods were a catastrophe and a comprehensive failure by Melbourne Water to do its job, writ large,” she wrote.

Melbourne Water’s submission states that the most recent flood modelling for the lower Maribyrnong River was commissioned in 2003, using hydrological work completed in 1986 as its starting point.

“It is common practice for updated flood models to build from data sets used in previous models,” it said.

Some residents of the area have called for funding for the Arundel basin. The basin would form a natural dam that would slow flooding in densely populated areas downstream. Funding for such a project had been previously proposed.

Valuable information learned to improve modelling

The water authority says that “valuable information” from the October flood will be used to improve its modelling, but adds there is no regulated standard for the frequency of updating flood models.

Melbourne Water is examining how it can better resource its flood-modelling work. Climate change is named as a complicating factor that will be embedded into new modelling.

“Extreme rainfall events in greater Melbourne will become more intense through the next century,” the submission states. “This is making it harder to rely on historic data to predict future floods. Given this known future impact, it is no longer adequate to use past rainfall events as an indicator of the potential future events.”

Detailing the events leading up to the morning of October 14, the submission places some blame on the Bureau of Meteorology’s rainfall forecast. The submission explained it was revised down on the afternoon before the flood. That led to Melbourne Water downgrading its flood prediction to “moderate” at 2.24 pm.

Twelve hours later, the flood warning was again upgraded to “major.” However, most residents had already gone to sleep, not anticipating any danger.

“Around 12.30 am on October 14, Melbourne Water identified that the real-time data showed the river was rising faster than the model had predicted. Melbourne Water updated its predictions.”

The submission states that the rain forecast changed several times. It was conceded that “this is not unusual” because predictions become more accurate closer to the time of the rainfall.

“The Maribyrnong catchment had already received large volumes of rainfall in the preceding weeks by the time of the storm event… This means that the above-average rainfall on an already wet catchment created larger than normal volumes of runoff.”

Bureau of Meteorology denies blame

A spokeswoman for the Bureau of Meteorology, which did not enter a submission, denied it was being blamed.

“The submission talks about the facts of the event,” she said. “Daily briefings to Melbourne Water in the lead-up to the event provided greater detail around expected rainfall totals as the event drew closer.”

Melbourne Water argues in its submission that more needs to be done to help the community understand flood risk, similar to how Victoria improved bushfire preparedness.

It cited a 2018 survey that found only 44 per cent of households in flood-prone areas were aware of their flood risk.

“The flood risk profile of a city is less quantifiable under conditions of changing rainfall patterns due to climate change. This can have unintended consequences such as creating a sense of complacency that can cause communities to be less prepared.”

Melbourne Water’s inquiry panel will now review all submissions. It will then compile its findings in a report to be published later this year.

Submissions for the parliamentary inquiry are open until May 8.

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