Gulf Group improving healthy waterways in Carpentaria

Gullies are common across northern Australia, where the wet season sends huge amounts of water moving over land, as was the case during the 2019 monsoon trough floods.

Surface water flowing in a line over inadequate groundcover scours soil, forming a channel that can come to be many metres deep.

The starting point is usually an area of disturbed soil, a livestock or vehicle track, or existing erosion. Gullies continue to deepen and can spread up or down slopes.

They’re a real danger to animals, people, and vehicles. Gullies divert water from where it’s needed, and they take topsoil, silt and nutrients away from the natural landscape.

Gullies are bad news. But they can be fixed.

The Northern Gulf Resource Management Group has been working with a landowner on a property in the upper catchment of the Einasleigh River, where a nine-hectare alluvial gully was causing serious concern.

Group Project Officer Marcus Mulholland said the gully system was very large and covered an area of almost 10 hectares.

“Through these remedial works, it is estimated that 4,790 m3/year of sediment will be prevented from entering the adjacent waterway. This improves the health of the waterway and prevents the mobilisation of sediments into the Gulf of Carpentaria,” he said.

So, how was it done?

A series of basins direct overland water flow through rock check dams. They reduce water velocity, protecting surface soil from erosion. The dams also trap mobilised sediments, which settle behind the wall, instead of going into the nearby river system.

Then, it’s essential to establish strong vegetative ground cover with a mixture of grass species. This helps the basins do their job while reducing raindrop impact and overland flow, further protecting the soil top layer from erosion.

Mr Mullholland said it was a very expensive exercise, so the key message is to address erosion early by employing good land management practices and maintaining strong ground cover.

This project was delivered through the Environmental Recovery Package, which was approved as an extraordinary recovery measure jointly funded under the Commonwealth-State Disaster Recovery Funding Arrangements (DRFA).