Calley Valley wetlands contamination
© Mackay Conservaton Group
Satellite imagery released by the Queensland government shows serious harm has occurred the the Caley Valley wetlands which adjoin Adani’s Abbot Point coal terminal in the aftermath of Cyclone Debbie in 2017. (Left) 14 May 2016 (Right) 1 April 2017.

Expert says sensitive Caley Valley wetlands blackened by coal-laden water from Adani's nearby port after rain from Cyclone Debbie

Coal dust released from Adani's Queensland coal port after Cyclone Debbie appears to have caused "massive contamination" of sensitive wetlands, an academic expert says.

A vast swathe of the Caley Valley wetlands has been blackened by coal-laden water released from nearby Abbot Point port after Debbie's torrential rains inundated its coal storage facilities last month.

Satellite imagery of the coal spill last week prompted an investigation by the Queensland Department of Environment and Heritage Protection (EHP), which said the port operator appeared to have acted in line with a temporary licence to release the excess water.

The caveat was that the licence did not "authorise environmental harm", an environment department spokeswoman said.

Norm Duke, a principal research scientist at James Cook University's TropWater unit and an expert in diagnosing contamination of wetlands, said an aerial image of the area showed "there's undoubtedly going to be environmental harm".

"The image shows me a massive contamination of an area that I'm very familiar with," Duke told Guardian Australia. "That's not an area they should be dumping their stuff in.

"I'm surprised [they were allowed to do so] - in some ways it would be almost better going into the sea rather than dropping it into somewhere it's just going to cause long-term damage."

Duke, who has done extensive research on contamination of mangroves from oil spills, said he had "never seen anything as bad as this for coal dust".

The spread of coal dust over a "huge" area of the wetlands risked creating a "double whammy" of harm that would have dire implications for local flora and fauna, from fish and birds to molluscs and crabs, he said.

First, the sediment would raise the level of mangroves where "if you change the elevation even by a few millimetres, some plants and animals will not be able to live there because the tidal regime will change dramatically". This could then be compounded by the potentially toxic effects of coal dust.

The extent of both problems could be established almost immediately with site visits, Duke said. But a further problem could emerge months later in the dry season, when fine coal dust could suffocate plants, he said.

"We are looking at something nobody's going to clean up," Duke said.

The department launched an investigation after it became aware of satellite imagery last Thursday apparently showing sediment-laden water flowing from Abbot Point's settlement ponds into the adjacent wetland, a spokeswoman said.

The investigation was into "whether there has been any unauthorised releases of water" into the wetlands.

"Initial monitoring results indicate releases to Caley Valley wetland were in accordance with" the conditions of a temporary emissions licence [TEL] granted to Abbot Point, which allowed the release of water with up to 100mg per litre of "total suspended solids", she said.

"In the event of major rainfall and flooding, mines and associated sites can apply to EHP for a temporary emissions licence, which is a permit that temporarily relaxes or modifies the conditions of an environmental authority.

"A TEL does not authorise environmental harm."

The spokeswoman said the investigation was continuing, "including accessing historical satellite imagery to compare wetland colour and depth fluctuations".

A spokesman for Adani said the company believed it had acted "within the requirements of the temporary emissions licence".

Peter McCallum of Mackay Conservation Group said the spill in 5,000-hectare wetlands that were home to more than 40,000 shore birds showed "the lack of capacity Adani has to operate in a sensitive environment".

The group has written to Queensland's environment minister, Steven Miles, asking how the government intended to rehabilitate the wetlands and whether any prosecutions for environmental damage would follow.

The Palaszczuk government came to power in 2015 having promised to scrap an earlier plan to allow Adani to dump dredge spoil from the port expansion on to the Caley Valley. The plan is now to dump spoil on a disused industrial site near the port and the wetlands.

Adani has directly controlled the running of the port since September, when it bought out previous operator Glencore.

It bought a 99-year lease on the port in 2011 and says it has invested more than $1.8bn in the existing terminal.