Flooding in Masterton in 2017. Photo: PHOTO / FILE
Almost 18,000 properties across Wairarapa are estimated to be at risk in the event of a severe flooding event.
The numbers were revealed to Local Democracy Reporting by Greater Wellington Regional Council following a request under the Local Government Official Information and Meetings Act.
The exact figure of 17,800 breaks regionally down as; Carterton 3100 properties, Masterton 9400 properties, and South Wairarapa 5300 properties.
The figures, which included rural and urban properties, were set to increase.
Lian Butcher, Greater Wellington Regional Council's (GWRC) group manager environment, said climate change was already changing the frequency and intensity of severe weather.
"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.
"For example, we estimate that by 2110, both the South Wairarapa and Masterton districts [will] have nearly 50 percent of all buildings exposed to flooding, (approximately 6100 and 10,900 respectively).
"This represents approximately 60 percent of the commercial buildings in South Wairarapa and 70 percent of commercial buildings for Masterton. Both councils have nearly 50 percent of all residential buildings exposed to flooding by 2110."
Emergency services, staff and community members have put a huge effort in to clean up Tinui School so that it can be repaired after Cyclone Gabrielle flood damage. Photo: PHOTO / PIERS FULLER
Butcher said while four of the five Wairarapa towns (Featherston, Greytown, Carterton and Masterton) were at risk of flooding from major rivers in the Ruamāhanga Valley, Martinborough and other areas were not unaffected.
"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."
The council had also conducted a detailed flood damages assessment for Masterton, including allowances for buildings, vehicles, contents, clean-up costs, relocation and rural areas.
"This estimates between $8.1 million and $16.7m for present day and $21.5m and $42.3m with climate change," Butcher said.
These lower and upper bounds are based on range of damage curves. The council had not conducted a similar analysis for the Carterton or South Wairarapa districts.
By comparison, a Wellington region flood exposure assessment, prepared for the council by Tonkin and Taylor Ltd in 2022, highlighted approximately 31 percent of the broader Wellington region's population and buildings could be exposed to flooding during a 1-in-100-year flood event at that time.
Hinakura Road in Martinborough was damaged after severe rain in 2021. Photo: PHOTO / SUE TEODORO
GWRC played a key role in managing flood risk, including modelling, risk management planning, emergency management and the construction and maintenance of flood defences.
The council had a number of flood management work programmes underway in Wairarapa including: Waipoua urban reach - involving working with community members, mana whenua and Masterton District Council on a preferred flood risk management option for the urban reach of the Waipoua River, which flows through Masterton; the feasibility of using nature based solutions for addressing flood risk to Masterton and; the lower Wairarapa valley development scheme review.
"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.
LDR is local body journalism co-funded by RNZ and NZ On Air.
