42 | West Coast Regional Council: Greymouth Flood Resilience PH: 03 768 0218 DARREN: 021 310 453 EMAIL: ADMIN@MBDCONTRACTING.CO.NZ MBD CONTRACTING LTD - 50 ARNEY STREET, PO BOX 114, GREYMOUTH, 7840 MBD is proud to support West Coast Regional Council Christchurch | Timaru | Greymouth | Nelson E hello@do.nz P 0800 999 333 www.do.nz Geotechnical Engineering / Environmental Science Surveying / Civil Engineering / Structural Engineering Planning and Resource Management THINK PLAN DO REGIONAL DEVELOPMENT Flood protection challenging, but necessary The programme forms part of an investment into flood protection across the West Coast, covering Greymouth, Hokitika and Franz Josef. T T Kelly Deeks “We are working in very tight corridors between the river, roads, private properties, and existing infrastructure, and in some locations we also have soft ground conditions that require careful management.” The West Coast Regional Council is continuing to shore up its Greymouth flood- protection scheme, lifting stopbanks and floodwalls across key parts of the town to strengthen protection against a one-in-150year flood event as part of a wider, $65 million regional flood-protection investment. West Coast Regional Council capital programme manager, Tom Hopkins, says the work builds on decades of staged upgrades following major flooding in 1988, which drove the construction of the original flood-protection network completed in 1990 after widespread damage across Greymouth and surrounding communities. “A major upgrade in 2010 lifted the level of service from a one-in-50-year event to a onein-150-year standard,” Tom says. “That involved strengthening and raising stopbanks and floodwalls across key areas, including the central business district, Blaketown, Cobden, and the adjoining river corridors.” He says the current project continues that approach, focusing on lifting remaining stopbanks at Blaketown and Cobden to match the level of protection already achieved in Greymouth’s central business district. “We are raising heights by around 100 to 500 millimetres in some areas,” Tom says. “We are also reshaping the landward batter slopes to reduce seepage risk and improve long-term stability.” The wider programme forms part of an investment into flood protection across the West Coast, covering Greymouth, Hokitika and Franz Josef, and delivered through a co-funding arrangement with Kānoa via the Regional Infrastructure Fund for Flood Resilience projects. Tom says that while the construction is relatively straightforward in principle, the working environment creates significant challenges for crews on the ground. “It is technically simple work, but the constraints make it complex,” he says. “We are working in very tight corridors between the river, roads, private properties, and existing infrastructure, and in some locations we also have soft ground conditions that require careful management.” The programme is scheduled for completion in September next year, and Tom says future planning will account for changing climate conditions and evolving river behaviour. “We are building to a robust current standard, but we are also aware that climate change will influence future risk profiles,” he says. Alongside stopbank upgrades, the council is also investigating replacement of existing floodgate systems at key road and rail crossings. Current portable barrier systems are cumbersome and can take three hours to install ahead of flood events. “We want to improve the speed and ease of deployment, whether that is through automation or other more efficient systems. The challenge is balancing affordability with reliability and emergency readiness.” The Greymouth works sit alongside major flood-protection projects elsewhere on the West Coast. Hokitika and Franz Josef are also undergoing staged upgrades aimed at reducing risk to homes, businesses and critical infrastructure. Tom says the combined programme reflects a long-term regional approach to resilience, rather than isolated projects. “These are interconnected systems protecting whole communities and key infrastructure,” he says. “The focus is on delivering reliable protection now, while also building flexibility into the network for the future.” The wider programme remains one of the largest infrastructure investments in the region, aimed at strengthening long-term community resilience and safeguarding critical assets across the West Coast.
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