Actively eroding gullies difficult and expensive to fix

Fine sediment and nutrients from agricultural land are a significant threat to the Great Barrier Reef.

The Burdekin catchment is the largest contributor of anthropogenic fine sediment loads of the 35 catchments draining to the Great Barrier Reef. It delivers, on average, 3.3 million tonnes per year; more than double the load of any other catchment. Most comes from gully erosion in grazing areas.

The Bowen Broken and Bogie (BBB) river catchment encompasses an area of 11,718km2, and is part of the much larger Burdekin River system (130,000 km2). Despite its relatively small size (less than 9 per cent of the Burdekin, and less than 3 per cent of the total catchment area draining into the Great Barrier Reef), the BBB catchment generates almost a quarter of the total of fine sediment load delivered into the GBR lagoon. 

About 65 per cent of that fine sediment comes from gully erosion. A total of 22,311 active gullies were mapped in the BBB study area (~3,500 km2), with a cumulative active area of 4,620 ha. This makes the gully remediation in the BBB catchment a focus for investment activity.

Gully remediation in this landscape is challenging. The area is vast, sparsely populated and poorly serviced. The climate exhibits a pronounced wet and dry season, with most rain falling in intense falls between November and April.

Average annual rainfall is 715mm (28.1 in), with significant year-to-year variability. The window for undertaking large-scale earthworks is often narrow, and revegetation is constrained by water availability.

Many of the gullies are a legacy of historical land management, and unrelated to current land management practice or current owners.

Many gully works involve high capital cost, and deliver little private benefit to the landholder. Characteristics vary considerably between gullies, requiring tailored treatment plans for each gully.