News / Environment

Merri Creek flood ‘a taste of things to come’

Tonnes of plastic, cardboard and other litter will take weeks to clean up

A man and his dog reach a dead end on the Merri Creek path near Moreland Road on Friday.

Mark Phillips
Monday, October 17, 2022

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IT will take weeks to clean up rubbish left behind from the high water levels that broke the banks of the Merri Creek on Friday, and environmentalists are warning similar extreme flooding events will become more common in future.

On Friday, the Merri Creek became a raging river, peaking at 4 metres in the hours before dawn with the waters rising above the banks and closing walking and cycling paths along some stretches of the creek.

While there was no major property damage, the murky brown water has left a layer of mud in some areas, and tonnes of plastic, paper and other rubbish have been left behind by the fast water flows.

The flooding was caused by torrential rain earlier in the week that was too much for water catchments further upstream.

Environmentalists say that housing developments in Melbourne’s far north are further degrading water catchments and wetlands and will mean more regular flooding downstream in years ahead.

The Bureau of Meteorology said 39 mm of rain fell into the Merri Creek catchment on Thursday and within hours the impact began being felt in the creek itself.

In the Brunswick-Northcote stretch of the creek, a peak of 4 metres was recorded at 4.30am on Friday, which was above the moderate flood level of 3.8 metres. By late afternoon on Friday, it had retreated back to below the minor flood level of 3.2 metres.

It peaked at Coburg at 3.7 metres at 3.30am on Friday.

Friday’s peak was a metre below the 5 metres recorded on June 1, 2013, one of Melbourne’s wettest days on record when the catchment received a dumping of 57 mm.

The flooding created spectacular images on Friday, including videos posted on social media of rapids on the Coburg lakes.

The high waters touched the lowest lying parts of CERES in Brunswick East, but the suburb avoided the large scale damage seen from the Maribyrnong River flooding.

Parts of the Merri Creek path remained under water on Friday evening, including underneath the Moreland Road bridge, while branches, dead trees and tonnes of debris had been swept down the river.

Luisa Macmillan, manager of the Merri Creek Management Committee, said the flooding had closed paths but there had not been any permanent damage to infrastructure.

“From our perspective the biggest clean up issue is the amount of litter that has come down, plastic litter and other litter that happens after a flood event and it’s a huge task to try to remove as much of that as possible before it starts disintegrating and forming micro plastics and making its way into the Yarra and Port Phillip Bay,” she said.

“The other thing that has happened is some areas that were recently planted, we’re assuming that some of the plants have been washed away. We don’t know to what extent that has happened, but over the next couple of days we will get a better idea.”

She said it was the responsibility of Melbourne Water to remove litter and debris from the creek itself, but volunteers would be rallied to clean up litter that was now strewn along the banks of the creek.

The creek itself will also suffer from an increase of turbidity: the amount of sediment and mud in the water from soil being washed into the catchment by the heavy rains.

“The water quality definitely deteriorates every time it rains because there’s polluted stormwater drains discharging into the creek bringing all of the run off from roads and the oil and grease from cars and bits of zinc from rooves and a whole range of contaniments into the waterways,” Ms Macmillan said.

Peter Ewer of the Friends of Merri Creek group said the Merri Creek was suffering from “urban stream syndrome” caused unnatural water flows into the creek as a stormwater drain.

He said the extension of Melbourne’s urban boundary and housing developments around the Wallan area were impacting on the Merri Creek catchment and forcing more water down the creek when there was heavy rainfall.

As a consequence, more flooding will become a more regular occurrence as more water is shifted down the creek. This will be exacerbated by climate change, Dr Ewer said.

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Scenes from the flooding of Merri Creek on Friday.

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In a manifesto that has been released for the state election, the Friends of Merri Creek are calling for the establishment of a protected regional park in the upper Merri catchment area, along with a network of “smart tanks” to capture and control stormwaters.

“If the sub-divisions continue to destroy the remnant wetlands, what we saw on Friday is only a foretaste of what is to come,” he said.

“It’s absolutely vital that park is declared so we can protect those wetlands and control the flows into the creek.

“We need further wetlands down the creek and we need smart water tanks which are computer controlled and can release water during low flow periods.

“We have the solutions, but it’s a question of whether we have the political will.”

The immediate consequence of the flooding on Friday is tonnes of debris, waste and litter that will need to be collected and taken away, especially non-biodegradable plastics.

Painstaking work to re-vegetate parts of the Merri Creek will also have been washed away.

“We haven’t done an assessment yet and the water will have to recede to know how much damage has been done,” Dr Ewer said.

“We spend thousands of hours every year planting and repairing along the creek and a lot of that will be damaged.

“It will be our volunteers who will be doing most of the work. Effectively the community is subsidising the packaging industry to clean up their mess.”

Ms Macmillan agreed that increased urbanisation reduced the ability of the natural environment to soak up heavy rainfalls and was creating more hard surfaces that led to run off into the Merri Creek, but she said older areas like Brunswick were also a major problem.

Nowadays, flood mitigation infrastructure is required as part of planning permits for new developments, but that wasn’t the case when Brunswick was developed.

“It’s the older parts of the Merri Creek catchment that are the worst because they were developed 100 years ago or more and we haven’t got any retarding basins or stormwater treatment wetlands so the water goes straight into the creek with no intervening measures to slow it down,” Ms Macmillan said.

“Although the newly urbanising areas will increase the amount of runoff into the creek, there are some attempts made to slow down the flows and not make flooding conditions downstream worse, but in the older areas we have a historical legacy of a paradigm of getting the water away as quick as possible.”

If you would like to volunteer to help remove litter along the creek, the Friends of Merri Creek co-ordinate regular clean up activities. You can also contact Julia Cirillo, Rapid Response to Litter project co-ordinator at Merri Creek Management Committee for more information.