Rock Chute an Erosion Control Solution in the Wet Tropics

SOLUTIONS TO EROSION

ENGINEERED ROCK CHUTE TO PREVENT EROSION

16 DECEMBER 2020

A Far Northern grazing family now has another good reason to count down to the wet season – a large-scale rock chute that needs testing out.

The 50m chute, completed last week, has been built to stop erosion that saw gullies spread like fingers out across the land over more than 30 years, causing topsoil losses on valuable grazing land and sending sediment into the river system when it rained.

Woodleigh Cattle Station owners Pete and Kate Waddell have been working with natural resource management organisation Terrain NRM on improving the land through engineered rock chutes, repairs to old tin mining tailings dam complexes and changes to grazing practices.

The new rock chute comes two years after a 100m chute was constructed on a different part of the Tablelands property.

“This one is in a gully complex that’s about 150m long, a couple of hundred metres wide and up to five metres deep – in places it’s like a cave,’’ Terrain NRM’s Jen Mackenzie said. “It strengthens this section of gully so we can direct water away from the other sections above it via a bund wall that is 600m long and extends either side of the problem area.

“It’s like a funnel for water to flow through to the creek without causing major damage like it has been.”

The rock chute and bund wall structures are expected to stop more than 250 tonnes of sediment a year – or up to 10 large haul truckloads – from flowing into the Herbert River catchment and out to the Great Barrier Reef lagoon.

Ms Mackenzie said the Waddells, like many landholders in the upper Herbert catchment, were still dealing with the impacts of historical mining practices and legacy erosion issues.

The work is part of a larger Herbert Gully and Grazing Project, funded through the Australian Government’s Reef Trust IV program to target erosion hot spots, which prevents the loss of healthy top soil and productive land and reduces fine sediment loads flowing to the Great Barrier Reef lagoon.

It is underway on five properties in the Upper Herbert River catchment and ranges from engineered erosion solutions to grazing management changes.

Mrs Waddell said the family was waiting with interest for the wet season.

“This is a great addition for erosion control – we’re hoping it works a treat,’’ she said.

The family has also been fencing to create smaller paddocks for rotational grazing and installing off-stream watering points for cattle.

“Our soil is our lifeblood but even with good grass cover and light stocking rates, some soil types here erode easily during heavy rainfall,’’ Mrs Waddell said.

“Over the last 10 to 15 years we’ve started things like wet season spelling – where we fallow paddocks – and we’ve stopped burning. We’ve noticed a big improvement in our grasses and soil biology, including the water-holding capacity of our soils. This project is the next step for us.”

Ms Mackenzie said the Herbert River Gully and Grazing Project was a five year program in partnership with landholders, and sites like Woodleigh Station would become models for future projects across the Great Barrier Reef catchment.