Nearly 18,000 properties across Wairarapa are estimated to be at risk if a severe flooding event occurs, with the number expected to rise in the coming decades as climate impacts intensify. Reported by 1news.
The figures were released to Local Democracy Reporting by Greater Wellington Regional Council (GWRC) under the Local Government Official Information and Meetings Act.
In total, 17,800 properties are currently considered flood-prone, including both rural and urban areas. The regional breakdown shows 3,100 properties in Carterton, 9,400 in Masterton, and 5,300 in South Wairarapa.
GWRC group manager environment Lian Butcher said climate change is already altering the frequency and severity of extreme weather events, increasing flood risk across the region.
“Assuming existing schemes do not change, and at-risk properties are not retreated from hazard areas, the number of properties at risk is likely to increase.
Climate change modelling suggests that the effects of climate change will increase in the future. Especially as residential developments continue to be granted consent within known flood prone areas.”
Looking ahead, the projections are stark.
“For example, we estimate that by 2110, both the South Wairarapa and Masterton districts [will] have nearly 50% of all buildings exposed to flooding, (approximately 6100 and 10,900 respectively).
“This represents approximately 60% of the commercial buildings in South Wairarapa and 70% of commercial buildings for Masterton. Both councils have nearly 50% of all residential buildings exposed to flooding by 2110.”
Butcher said that while Featherston, Greytown, Carterton and Masterton are vulnerable to flooding from major rivers in the Ruamāhanga Valley, other areas are also impacted.
“Although on a higher terrace, Martinborough is cut off during flood events causing disruption to visitors and residents alike. The catchments on the Wairarapa coast are also not without risk as experienced with the flooding in the Tinui area as a result of Cyclone Gabrielle.”
GWRC has carried out a detailed flood damage assessment for Masterton, factoring in impacts on buildings, vehicles, contents, clean-up costs, relocation, and rural land.
“This estimates between $8.1m and $16.7m for present day and $21.5m and $42.3m with climate change,” Butcher said.
No similar assessments have yet been completed for Carterton or South Wairarapa.
By comparison, a 2022 flood exposure assessment for the wider Wellington region by Tonkin and Taylor found about 31% of the region’s population and buildings could be exposed during a one-in-100-year flood event.
GWRC currently leads flood-risk management through modelling, emergency planning, and maintaining flood defences. Ongoing work in Wairarapa includes flood management planning for the Waipoua River through Masterton, exploring nature-based flood solutions, and reviewing the Lower Wairarapa Valley Development Scheme.
“Following Budget 2024, Greater Wellington and Ministry of Business, Innovation and Employment’s regional economic development and investment unit, Kānoa, agreed to co-fund 16 flood resilience projects as part of a nationwide initiative.
“The programme spans 15 sites across Wairarapa and one in Ōtaki, which are critical in future proofing community, infrastructure, cultural taonga and the economy, following a major flooding event,” Butcher said.