Pile fields help landholders and the Reef

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.