THERE is a real possibility of a black water event in the Richmond River once floodwaters start to recede, according to Richmond River County Council's floodplain services manager.
Michael Wood said there was sufficient standing floodwater in the west Coraki and lower Bungawalbyn areas to have an impact.
"Once the river falls enough for discharge, we will see what the impact is," he said. "The January flood event was small but still packed a punch in terms of overwhelming the river and dropping dissolved oxygen levels to below 1 mg/L .
"The fact that there was no significant fish kill was more that the fish had moved towards lower estuary and beaches.
"I hope the fish are still in the lower reaches and that, failing entrapment in one of the canal estates, all might be well in respect to averting a fish kill."
The floodgates at the two major flood mitigation systems, Tuckean and Rocky Mouth Creek, were managed by data loggers, which alerted Safety Management Systems staff when water quality thresholds were breached.
"Our advice from scientists is keep the gates open until the pH falls," he said.