Satellite imagery has revealed the huge amounts of floodwater heading into the ocean and towards parts of the Great Barrier Reef after Queensland experienced more than two weeks of heavy rain.
Some communities were hit by heavy flooding earlier this month. Queensland could soon see more severe weather with Cyclone Alfred being tracked in the Coral Sea.
Before-and-after images were captured by commercial and public satellite providers and show large brown plumes of sediment flowing into the ocean via swollen rivers.
One image shows floodwater flowing into the ocean from the Burdekin River on February 16.
"The Burdekin River catchment particularly is huge," said Roger Beeden, chief scientist at the Great Barrief Reef Marine Park Authority.
"So when it empties, it empties an enormous amount of water out into the Great Barrier Reef lagoon."
Another satellite image shows there was also run-off from rivers north of Cardwell on February 6.
Dr Beeden said the combination of freshwater and sediment on the reef can be harmful.
"In the immediate term, the issue for particularly coral reefs that are within some of those flood plumes can be that you actually have a stress effect upon the corals.
"They're marine animals, they've evolved to deal with salt water, and so when you get fresh water on them, it can cause stress effects, like coral bleaching, in the worst scenario.
"You can get impacts on coral communities, seagrass communities, and the creatures that live within them, as a result of those flood plumes."
BOM records huge rainfall totals
The rain event saw huge falls across parts of North Queensland.
Climate hydrology specialist Caitlin Minney from the Bureau of Meteorology said an active monsoon trough, and several tropical lows, produced the heavy rain between January 27 and February 12.
"The highest rainfall totals were reported at Paluma, in the Burdekin River catchment about 40 kilometres south of Ingham," she said
The Paluma Ivy Cottage station recorded 2,662 millimetres of rainfall between February 1-12.
[CHART: RAIN]In the same period, 2,143mm and 2,072mm were recorded at the Cardwell Range and Rollingstone AL stations, respectively.
Satellite imagery taken of Ingham shows some of the impact with flooded fields and lines of cars driving through shallow water.
Dr Beeden said it's not all bad news for the reef because the rain and run-off has helped cool parts of the reef, which had been under heat stress.
"It's actually had some actually cooling effect across the reef, and in many ways, that was actually most welcome," he said.
"We have a number of tools that help us to monitor heat stress across the entire Great Barrier Reef region, during particularly summer periods when we see elevated temperatures.
"We've seen extensive heat stress through the earlier months of summer and particularly in the far northern region."
GBRMPA is now running an extensive monitoring program, which will try to understand the short and long term affects the flooding will have on the reef.
"We've been collecting, with our partners, information through marine monitoring programmes, satellite imagery," Dr Beeden said.
"It's an extensive flood plume in those areas — its all the way from river mouths in Mackay, all the way up to the Cairns region.
"It just depends upon how long it takes for that to dissipate, and some of that comes down to wind patterns, and that will be different up and down the coast."
