Flooding accelerates erosion, not cause it, webinar told

Floodplain erosion webinar explores causes and ways to eliminate them

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Some of the damage caused by the February 2019 flooding. Pictures - Southern Gulf NRM.

Some of the damage caused by the February 2019 flooding. Pictures - Southern Gulf NRM.

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'Don't cut your land' is one of the key messages presented during a webinar that looked at managing erosion in Gulf floodplains held recently by Southern Gulf NRM.

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'Don't cut your land' is one of the key messages presented during a webinar that looked at managing erosion in Gulf floodplains held recently by Southern Gulf NRM.

Held as a lead-up to field days with recognised grading expert Darryl Hill planned for July and August, the webinar gave participants an overview of the causes and ways of remediating them.

The presenters were Hugh Pringle, Ecosystem Management Understanding, and Paul Theakston, a rangeland rehabilitation officer with the NSW Local Land Services.

It's an often-repeated phrase that prevention is better than the cure but was emphasised by Mr Pringle, who said that working to a whole of landscape plan was very important.

"The key point is, don't cut your land," he said.

"People think of gullies as being caused by excessive flooding but that's the accelerator pedal, not usually the start of it.

"Nick points are anywhere the land is cut, such as station tracks, culverts and animal pads."

He added that overgrazing was another accelerator pedal, not a cause.

Mr Pringle described gully fingers as thieves stealing good soil away.

"Water flows downhill, erosion proceeds uphill, even sheet erosion, and topsoil follows the water down," he said. "You end up with a canal to the coast, there are far too many that are like that."

Another example of gullies spreading further with each flow of water.

Another example of gullies spreading further with each flow of water.

Mr Pringle said land managers were currently in a terrible predicament, dealing with two problems, the erosion caused by the usual small flows, plus the scarring brought about by the massive floods of February 2019.

"I feel for you," he said. "Once water starts a gully head, it doesn't stop until it hits rock."

His presentation illustrated a variety of ways other groups had tackled the problem in their areas, including drill rods being strategically placed vertically, which he said had been astoundingly successful in raising the base level of channels and getting water back onto floodplains.

"It's really important not to be kicking water out of your channels and gullies when the reception is a gully head itself, or you just link them all up and it becomes a bigger problem," he said.

His words were emphasised by Mr Theakston, who talked about slowing down the water going onto a floodplain, upper catchment repair options, and mitigating the damage or stopping it altogether.

He gave examples of water spreading and keylines using diversion banks, and waterponding, as well as soft filters such as netting and branches to reduce the impact of the water flow.

Techniques for mitigating water flow included keeping grading to a minimum and making tracks wide so as not to create wheel ruts, and making sure tracks weren't parallel to drainage lines.

Whoaboys can be used as well.

Mr Theakston said before fixing a problem it was important to ask why the problem was there, whether it should be the priority to fix, and what you wanted to achieve by fixing it.

Then people needed to search through the toolbox for the best tool to repair the problem.

Southern Gulf NRM spokeswoman Anne Alison said so many roads had washed out in the north west, and paddocks left with scars from the high flow rate of the water over them.

"Darryl Hill is coming here for two weeks at the end of July and early August, and we could easily have had him here for longer," she said.

"He'll be showing people his techniques at field days and following up on-property, making sure that people have their slopes right and so on.

"We'll also show him gullies that have blown out to seek his advice on.

"This is general station repair work rather than high level riparian work."

Funding for the webinar and Mr Hill's field days comes from the Commonwealth/State Disaster Recovery Funding Arrangements and the Queensland government's Natural Resources Investment Program.

People wishing to attend the field days on properties at Cloncurry, Julia Creek and Richmond need to RSVP with Southern Gulf NRM by July 24.

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