Effectiveness of alluvial gully remediation in a semi-arid rangeland catchment

Abstract

Gully erosion is a globally significant form of land degradation that affects agricultural and rangeland productivity, ecosystem health and downstream water quality. In northern Australia, gully erosion is a major source of anthropogenic sediment delivered to the Great Barrier Reef (GBR) lagoon, driving substantial investment in landscape repair and gully remediation. However, quantitative assessments of remediation effectiveness remain limited, particularly for alluvial gullies in semi-arid environments where pre- and post-remediation water-quality monitoring is rarely available. This study evaluates remediation effectiveness using hydrological and water-quality monitoring from treated and control alluvial gullies in the Upper Burdekin catchment, a major sediment source to the GBR lagoon. Results from the post-remediation monitoring period indicate that high-intensity remediation, involving extensive engineering works and soil treatments, achieved sediment-yield reductions of up to 99%, despite the first post-treatment year receiving the third-highest annual rainfall on record since 1889. In contrast, medium-intensity remediation achieved lower effectiveness of 37% after one year. These findings show that high-intensity remediation can rapidly reduce sediment export from alluvial gullies but is costly and should be targeted to gullies where erosion processes, morphometric state and sediment-delivery potential justify intensive intervention. While vegetation recovery and longer-term landscape stabilisation may require additional time, immediate reductions in sediment export are achievable, supporting targeted remediation to reduce rangeland degradation and sediment delivery at gully scales. Continued long-term monitoring is needed to assess whether remediation outcomes persist under variable climatic conditions