As the sun emerges after the recent floods a new environmental threat has emerged

Sun beating down on stagnant flood water is a dangerous combination warns the EPA.

Flood waters reach the ocean off Hills Beach at Korora last month. Photo by Evol Coutman.

As the sun emerges after the recent devastating flooding a new environmental threat has emerged with the EPA encouraging residents to be proactive and report any ‘blackwater’ events.

Flood plains in much of coastal of NSW have been inundated with floodwaters in recent weeks and with the current warm, sunny weather this could lead to what the EPA term ‘blackwater’ events, with some fish deaths and odours already reported.

Road signs under water last month. Photo from Kempsey Shire Council

EPA Director Regulatory Operations Adam Gilligan said odours from the receding floodwaters are likely to be caused by natural processes due to low levels of oxygen in the waterways.

“The recent significant rain elevated water levels in many rivers. As the floodwaters moved over low-lying areas surrounding the rivers, they picked up large quantities of organic matter, including decaying vegetation and leaves, as well as dirt, sand and other debris,” Mr Gilligan said.

Fungi flourishing after the rain on the Coffs Coast. Photo by Janine Watson

Although an important process for healthy river function, the decomposition of organic matter depletes oxygen levels in the water and releases tannins which give the water a distinctive black colour.

This natural process is commonly known as ‘blackwater’ and is likely to cause fish deaths in rivers.

The stagnant water also contributes to the odours which can smell like rotten egg gas.

“Blackwater after flooding is a natural feature of Australian river systems and the capacity to prevent and manage the impacts of blackwater is limited.”

Dale Rogers captured the sun shining after all the rain over Bonville on Wednesday morning, Mach 24.

Mr Gilligan said the EPA is supporting local councils and other government agencies by sampling flood waters and providing advice.

“The EPA will continue taking samples and testing water sites where required. We encourage the community to be patient and to make contact with the EPA if they have concerns about polluted waterways in their area,”

River water may contain infectious organisms and chemicals, particularly after heavy rain periods. Entering river water after heavy rain increases the risk of injury and infection. People choosing to swim in rivers at any time should avoid swallowing water. If you have swallowed river water and become ill, seek medical advice.

If you are concerned about polluted floodwaters please contact Environment Line on 131 555 or by email at [e-mail].