EROSION CONTROL – PILE FIELDS
PILE FIELDS HELP LANDHOLDERS AND THE REEF
24 FEB 2023
Eight hundred wooden piles are helping to solve erosion problems along a flood-damaged section of the Herbert River this wet season.
The recently completed pile field is the latest in a series of construction projects along the river system, which one of Queensland’s five highest contributors of fine sediment to the Great Barrier Reef.
Engineeered solutions for erosion
In the last five years, erosion-control work has included engineered solutions ranging from rock chutes and Zuni bowls to gully contouring and bank battering, as well as revegetation projects and changes to the way landholders graze cattle on their land.
The end results have been a win for property owners and the Great Barrier Reef lagoon, where sediment run-off smothers corals, seagrass and other plants and, in doing so, also affects the turtles, dugongs and fish that depend on them for food and shelter.
Abergowrie cane farmer Terry Sheahan is the latest landholder to benefit from work on his property.
“We’ve had floods over the years but there was one six years ago that cut through the paddocks, taking a corner piece of land and everything on it. With the silt dump as well, we lost about 20 acres of cane. We’ve been trying to build everything up again since.”
What are pile fields?
Terrain NRM’s Jen Mackenzie and her team are confident their latest pile field will solve problems spanning several hundred metres of riverbank. Pile fields are multiple rows of piles, driven up to seven metres into the earth. They are designed to slow down water and build up sediment, to protect and repair damaged riverbanks.
“Major erosion sites need more than vegetation initially. In coming years, we expect vegetation to establish in and around the timber piles and in time, as these piles break down, the vegetation will act as the long-term erosion control measure. We’ll also be doing revegetation work at this site at the end of the wet season.”
Ms Mackenzie said the Wet Tropics region’s high volume of rain meant that more engineering and modelling was needed for pile fields, with designs tailored to the weather conditions.
The pile fields project is part of Terrain NRM’s Upper Herbert Sediment Reduction Project. This program is funded by a partnership between the Australian Government’s Reef Trust and the Great Barrier Reef Foundation.
Thousands of tonnes of sediment savings
The structure is one of more than 10 engineered solutions constructed in the Herbert River catchment as part of the Upper Herbert Sediment Reduction Program and the Australian Government’s Reef Trust IV Herbert Gully and Grazing Project. It’s estimated that they collectively prevent several thousand tonnes of sediment from reaching the Great Barrier Reef each year.
More work needed to meet sediment reduction targets
“It’s a great start, but significantly more work is needed to meet sediment reduction targets for the Herbert River catchment,’’ Ms Mackenzie said.
“This includes land management practice changes. We’ve been working with graziers in particular for the last five years on changes ranging from rotational grazing to installing off-stream watering points and fencing to manage erosion and cattle movements. This is an important part of any long-term improvements to land and water in the Herbert River catchment.”
Cane farmer Terry Sheahan is looking forward to seeing how the pile fields area regenerates.
“They did a great job putting it in. It’s a big bonus for me. We’ll see how it goes this wet season. It’ll be a big advantage to rebuild those riverbanks and hopefully get them back to what they were.”
The Herbert River – Some facts
The Herbert catchment is the largest catchment in the Wet Tropics region.
The river spans 288km from the Atherton Tablelands to the coast at Ingham.
Under the Australian Government’s Reef 2050 Water Quality Improvement Plan, which sets water quality targets for each of the 35 river systems that drain to the Great Barrier Reef, the Herbert catchment is among the five highest contributors of both dissolved inorganic nitrogen and fine sediments.
Most of the engineered erosion solutions are in the Upper Herbert area, on grazing properties and at historical mining sites. For more information about these projects, which happened under Terrain’s Herbert Gully and Grazing Management project, visit our project page.
The new pile field is in the Herbert River near Abergowrie, about 35km north-west of Ingham. Other pile fields have been constructed by various organisations throughout the Wet Tropics region as part of erosion control measures. Pile fields are becoming increasingly popular as a long-term solution to streambank erosion in this part of the Great Barrier Reef catchment.