EXECUTIVE SUMMARY
The Gully Maintenance and Monitoring Project involved monitoring 24 remediated gully sites( 19 small-scale and five large-scale) in the Bowen, Broken, Bogie( BBB) catchment during three and a half years( 2022- 2025). Maintenance was done at some sites as required. This report communicates observed changes at sites, grazing management, maintenance costs and stability achieved. No major environmental impacts( droughts, floods or fire) affected sites between the time of the initial remediation works in 2019-20 and the end of monitoring in 2024-25. All the five large-scale sites and half of the small-scale remediated gully sites were in highly erodible soils( Sodosols). Another five small-scale sites only had works done in the catchment above the gully.
Remediation of the five large-scale sites involved experts at all stages and all sites were fenced to manage livestock access. Four sites had intensive earthworks to reshape, soil ameliorants applied( gypsum, fertiliser) and pasture seed sown. Structures installed included rock check dams, rock chutes and earthen banks. Of the four intensively treated large-scale sites two had reached a stable state by December 2024 and two were mostly stable. Maintenance was most often undertaken to repair rills and shallow gullies following rain and to stabilise soil around rock chutes. Observations suggest that, at most large-scale sites, the planted legume, Desmanthus sp., is increasing and grass species are decreasing. One causal factor may be a decline in fertility since initial works were undertaken because of a lack of nutrient cycling in the proto soil material. Some of the sites may have been negatively impacted by the short-term grazes implemented in the later years.
The 19 small-scale sites were remediated with some expert input, but mostly just in the design phase. Catchment works typically involved ripping, revegetation or banks with spreaders. Eleven of the 14 treated catchments achieved a stable site within four to five years and only 11 per cent of banks required maintenance. At the gullies there was either specific fencing installed around the site or a change in grazing management of the paddock with the gully. Earthworks tended to involve reshaping, fertiliser and seeding, and rock chutes or gully plug dams. Of the 14 treated smallscale gullies only two were considered stable in December 2024 and neither were in Sodosol soils. One gully in Sodosol soil was deemed unstable. The remaining 12 were either‘ mostly stable’ or‘ partly stable’. All sites that were reshaped and seeded required some maintenance, as did all six rock chutes. Data and observations indicate that the management of grazing at small-scale sites is an important influence. At the small-scale sites, when land managers made grazing decisions with a‘ high focus on improving land condition’, gullies were more likely to progress further towards a stable state. The more typical grazing management(‘ moderate focus’) of resting the site in the wet season and grazing along with the larger paddock for one or more months in the dry season appeared detrimental to many remediated sites.
Remediated gullies, both large and small-scale, in highly erodible soils in the BBB can reach a‘ stable’ state, as defined in this report, within four to five years. However, there are several caveats:
• There is a low chance of achieving this— only 10 per cent of sites( two of 19) in Sodosols achieved a‘ stable’ rating and these were both large-scale works.
• Four years is likely the shortest time one could expect to achieve stability, with high quality implementation, timely maintenance and favourable weather.
• The definition of‘ stable’ used in this report is not comparable to the stability that would be found in healthy landscapes with functional nutrient and water cycles, and no erosion. Sites considered stable in this report are likely to lack resilience.
Sixteen of the remaining 17 treated gullies that were not yet fully stable, were judged to be on the trajectory to achieving stability( mostly stable or partly stable). However, their success hinges on future events; particularly monitoring, maintenance, grazing activity and extreme weather. One large-scale site( Site 5) is a sound demonstration of a low impact approach to facilitating natural regeneration on sites where
NQ DRY TROPICS 1