Catchment Solutions have successfully rehabilitated over 15ha of severe gully erosion in the Ogmore area of the Styx River catchment, funded through the Australian Government’s Reef Trust IV Program. Due to the sodic nature of the soil found within the Styx River Catchment, even with restricted grazing, active gully erosion was occurring at a significant rate. Paddock to Reef modelling has demonstrated that the Ogmore area contributes 26,880t of fine sediment to the Great Barrier Marine Park per year.
Figure 1. Severe erosion representative of the erosion issues throughout areas of the Styx River catchment.
Figure 2 Gully erosion at Ogmore property
Figure 3 Gully erosion mapping at Ogmore property
To minimise ongoing erosion, varying treatment options were undertaken at the Oakdean Station, to demonstrate various erosion remediation methods intended for future adoption of these methods throughout the broader Ogmore area. Erosion treatment methods include combinations of gully reshaping, ripping (shallow <200mm), gypsum treatment (10t/ha), lime treatment (2t/ha) and rhodes grass seed application (10kg/ha). Additionally, following cut and filling earthworks, shallow ripping was undertaken to establish a topsoil layer. These works were followed by mulching to reduce rainfall impacts on the rehabilitated gully areas as well as a high rate of seeding with mixed pasture grasses. Conservation Volunteers Australia (CVA) assisted with the mulching of key areas and the establishment of downstream porous check dams within the drainage lines, following by the planting of over 200 tubestock saplings at key locations within the reformed drainage lines.
Figure 4 CVA volunteers undertaking mulching and tree plants at Ogmore
Figure 5 Porous Check Dam
Figure 6 Reshaping and gypsum treated erosion gullies
Follow-up monitoring in May 2020, demonstrated effective germination of the seedbank and successful rehabilitation of the eroding gullies.
Figure 7 Rehabilitated gully area – looking towards Deep Creek
Figure 8 Rehabilitated gully area – looking north-west
Based on a comparison of historical aerial surveys of the site, the rehabilitation of these eroding gullies at Ogmore will prevent over 6,500 tonnes of fine sediment getting to the Great Barrier Reef.
The demonstration site will be used to hold gully rehabilitation workshops in 2021 to local landholders within the Ogmore area, providing for expansion of the treatments to other similar sites owned by neighbouring landholders within the catchment.
Figure 9 Echidna found within rehabilitated gully area