CONCLUSION
Remediated gullies, large and small-scale, in highly erodible soils in the BBB can reach a‘ stable’ state, as defined in this report, within four years. However, only four of 24 sites achieved stability and this occurred under favourable weather conditions and with a high standard of implementation and maintenance. Also stable sites are still fragile and will likely decline if vegetation is reduced and soil exposed. Most of the 24 sites monitored in this project were classed as‘ mostly stable’ or‘ partly stable’ at the end of the project( December 2024) and therefore, while considered to be on the trajectory to achieving stability, their fate depends on future events; particularly monitoring, maintenance, grazing pressure and extreme weather.
Although this study lacks scientific rigor, results suggest that the‘ moderate grazing’ pressure implemented by many of the landholders, negatively impacted the sites. The two smallscale gullies that did achieve the‘ stable’ rating by December 2024 were in Downs country Vertosol soils, a more fertile soil that is more easily revegetated. The small-scale gullies in Sodosol soils proved difficult to remediate. In contrast, the catchments of these gullies may stabilise within three years after renovation work as long as there is sufficient topsoil remaining and the area is managed well. Works in the catchments in the Downs country Vertosol soils may take only two years.
The costs of maintenance for the large-scale sites was relatively low and within a generally acceptable proportion of initial costs. In contrast, the cost of maintenance works( all earthworks) at small-scale sites was high, often more than half the cost of the initial works.
Ideally, the learnings garnered from this project will help to inform future gully remediation plans. Suggestions for improvement include:
• Sufficient time is spent in the early stages of planning to understand the erosion processes occurring at a site to ensure the efficacy of remediation works.
• Remediation plans are informed by a sitespecific risk assessment / s that provides logic to the approach taken, suggests the duration of monitoring and outlines the likely issues to monitor.
• Suitably qualified people are available to plan, supervise construction and over-see the maintenance of engineered structures such as rock chutes.
• Revegetation specialists are engaged during planning, implementation and monitoring( e. g. 5-10 years).
• Monitoring, maintenance and grazing schedules are worked out collaboratively, involve grazing specialists and are documented.
• The requirements of the landholder with regard to protecting the revegetation, monitoring and maintenance responsibilities are clearly understood, and are formally agreed to by all parties.
• Low impact remediation methods are considered for improved cost-effectiveness or when the risk assessment indicates that it is pertinent to do so.
As a consequence the planning stage is likely to take longer and require more collaboration, but is likely to achieve better remediation outcomes and greater cost-effectiveness.
54 GULLY MAINTENANCE AND MONITORING TECHNICAL REPORT