New tsunami inundation maps released for Western Bay of Plenty

Western Bay of Plenty District Council has made new tsunami inundation maps available online, giving residents a clearer picture of which low-lying coastal areas could be flooded if a significant tsunami were to strike the Bay of Plenty coastline. The maps, developed from research by GNS Science (now known as Earth Sciences New Zealand), differ from existing evacuation zone maps — while evacuation maps show where people should go to stay safe, the inundation maps focus on where water could potentially reach.

The new mapping covers two scenarios: a rare offshore earthquake generating waves of between 8 and 15 metres along the Bay of Plenty coast (estimated at roughly a one-in-2500-year chance), and a second scenario involving a 5-metre tsunami from a rare offshore earthquake, with likelihood ranging from about one-in-300 in the east of the region to one-in-750 in the west.

For most of the Western Bay district this is the first time tsunami inundation has been formally mapped. Maketū, Little Waihi and Pukehina already had maps from 2017, but these will be updated — and in some cases, properties previously identified as at risk are no longer included. Council acting general manager strategy and community Emily Watton said the updated maps improve understanding of how the district's coastlines and low-lying areas could be affected, and are increasingly important given growing legislative requirements around natural hazard management.

As each hazard is mapped, affected landowners are notified and the information is added to council's website, property files and any Land Information Memoranda (LIMs). Council also uses the maps when processing resource consents, project information memoranda and building consents. The maps are available at westernbay.govt.nz.

Originally published in Katikati News (Sun Media).