An easy change to an agricultural weed control technique is helping farmers manage weeds, improve riparian vegetation and prevent streambank erosion.

Vegetation along waterways (known as riparian vegetation) is important for stabilising creek banks—tree roots hold the banks together and slow the water flow down, preventing erosion.

In recent times, landholders in the Mossman area have expressed concern about thinning or receding riparian vegetation. Given that creek bank erosion is a major issue for farmers it’s understandable they’re worried by the changes to their riparian zones.

Terrain NRM’s Ruginia Duffy said that planting trees is time consuming and can be expensive.

“The good news is we’ve learned that making a small tweak to traditional spraying regimes— switching from a non-selective to selective herbicide—is an easy and effective way of improving riparian condition,” said Ms Duffy.

Favourable climatic conditions in the Wet Tropics means the natural seed bank in the soil usually grow easily and unassisted.

However, when non-selective herbicides are used to control problematic weeds like guinea grass, native tree seedlings are also inadvertently sprayed out. Over time this hinders the riparian forest’s ability to regenerate and repair itself, leading to thinning and receding, and eventually bank erosion.

Marcus Bulstrode from the Queensland Department of Agriculture and Fisheries works with cane growers to support the development and uptake of sustainable farming practices.

A Mossman farm has become a demonstration site for Zuni bowls – a solution to gully erosion.

Landholders, engineers, council officers and contractors are visiting the property to learn how to build the structures, where they work best and how they can be used more widely to fight erosion in Tropical North Queensland.

Terrain NRM’s Ruginia Duffy said two Zuni bowls had been built on the farm.

“They are a smaller-scale, cost-effective way for landholders to stop erosion from advancing,” Ms Duffy said. “These bowls follow on from work on an Atherton Tablelands farm last year, where smaller bowls were built and have settled into the landscape.”

Zuni bowls are a lining of rocks built into gully heads where there are abrupt vertical drops. They take their name from the Native American Pueblo people from the Zuni River Valley, who first developed and used the structures.

“These days, work starts with a bobcat and ends with shovels and crowbars,’’ Ms Duffy said. “The structures are carefully designed to prevent water from disturbing the soil any further. They work with the natural landscape – by mimicking the kind of forms found in creeks.”

The latest bowls are part of a larger project repairing flood damage in the Mossman region. Other parts of the project have included more traditional earthworks, rock work and tree-planting to stabilise creekbanks that bore the brunt of floods in the 2018-19 wet season.

The Mossman Integrated Catchment Repair Project is funded by the Queensland Government’s Natural Resources Investment Program.

Earthworks and tree-planting are giving a Mossman farmer “peace of mind” leading up to the wet season.

Carmen Henning-White and husband Trevor White found ravaged creek lines when they inspected their property after floods in early 2018, with chunks of creek bank torn away and large trees swept into the floodwaters.

“We’d had erosion on the farm before, through the creek, but nothing like that,’’ Ms Henning-White said. “We lost three to four metres off banks, it was all just gone.”

The Whites are one of five Mossman families whose properties are being worked on to stabilise creekbanks and improve their resilience to future rainfall events, thanks to Terrain NRM’s Mossman Integrated Catchment Repair Project funded through the Queensland Government’s Natural Resources Investment Program.

Terrain NRM’s Ruginia Duffy said two sites had been repaired on the White’s property. She said “rock toes” were built in the streambed, embankments were reshaped and trees, shrubs and grasses planted.

“With the rate and level of erosion, combining earthworks and revegetation is the way to hold these streambanks together for the long-term,” she said.

“The rock structures are designed to protect the bank while the trees establish.”

Gerard Puglisi’s creek-side cane land in Mossman was washed away in the 2018 floods. Now he is banking on a combination of rocks and trees to better prepare him for future wet seasons.

Earthworks began this week at Mr Puglisi’s farm as part of a project to stabilise the banks of waterways in the Saltwater Creek catchment, through revegetation and engineered construction work.

Terrain NRM’s Ruginia Duffy said ‘rock toes’ – or structures that armour the lower section of streambanks – were being built along the water’s edge while the upper section was reshaped to reduce the slope and allow for tree planting.

“With the rate and level of erosion, combining earthworks and revegetation is the way to hold these streambanks together for the long-term,” she said. “The rock structures are designed to protect the bank while the trees establish.”

The project is one of two on the Puglisi property, and it follows similar work on three other Mossman farms over the past year.

Mr Puglisi said 20m of streambank on a dog-leg section of creek was repaired several weeks ago and the current project was on an S-bend that now included an island.

“The areas were gouged out in the flood and they’ve been eroding into the headland,’’ he said.

“There is more gouging every time it floods – if we can stop the erosion, we can protect our land and there is also less chance of topsoil ending up in the waterways and going out to the Reef.”

The work is part of the Mossman Integrated Catchment Repair Project, delivered by Terrain NRM and funded by the Queensland Government’s Natural Resources Investment Program.