Ruamahunga River — Cliff Face Repair

As part of Cyclone Gabrielle recovery efforts, GSI was contracted by NZ Transport Agency Waka Kotahi for a design-and-build project to repair an overslip at Ruamahunga that had threatened property and disrupted State Highway 25. The cliff face on the Ruamahunga River was accessible only by helicopter — there was no road access, and the riverbank below was itself unstable.

GSI partnered with Andy O'Sullivan Geotechnical Engineering as design lead. Upon site assessment, additional problem areas emerged beyond the original scope, requiring rapid coordination with the Department of Conservation, NZTA, and local homeowners to expedite approvals and access. The design centred on removing unstable debris, drilling soil nails into the stable cliff face, and applying a shotcrete facing, with biocoir matting for erosion protection on surrounding disturbed areas.

The Ruamahunga cliff face repair was completed in July 2024, delivering a permanently stabilised face with 492 installed soil nails, full shotcrete coverage, and bioengineering erosion protection. All works were completed by helicopter-supported rope access without any road construction or permanent infrastructure in the riverbank environment.

The GSI team were commended on their workmanship, organisation, and approachability by the clients, engineers to the contract, and the homeowners directly affected — reflecting the care taken in a complex, community-facing Cyclone Gabrielle recovery project.