Environment Waikato is stepping up work to manage a possible tsunami in the Waikato following the devastation from the Boxing Day tsunami in east Asia.
The Council has been involved in tsunami studies with Environment Bay of Plenty and reported its results in December, before the Boxing Day event. The risk from coastal inundation was considered high enough to allocate a first place ranking in the Regional hazardscape for a locally generated tsunami, and sixth place for an off-shore event.
At last week’s Catchment Services Committee meeting, Councillors heard that both councils had recognised that the threat of tsunami may be greater than traditionally thought and had undertaken research on the eastern coastline.
Stage one identified tsunami activity in the previous 500 years in Bay of Plenty and Coromandel, Stage two covered more detailed research of core samples to catalogue events and identify hot spots and stage three would develop appropriate responses, planning and management.
Findings from the first two stages showed the eastern coastline could expect a one metre wave tsunami every 80 years and a 2.5 metre wave every 320 years. There had been seven one metre events in the past 85 years and five since 1700 generating waves of one to three metres. Six events of more than five metres were found up to 3000 years ago.
Most at risk were the open coast from Otama Beach to Port Charles and out to Great Mercury Island and Mercury Bay. Locally generated tsunami were more destructive, with a shorter response time – 30 to 60 minutes – where previously the risk had been thought relatively low and recurrence interval long.
The study found the risk was comparable to a one in 100 year flood in the Waikato.
Stage three activities include consulting with local authorities, lifeline agencies and Civil Defence groups to develop planning responses and strengthen response mechanisms, management plans and strategies fore coastal communities most at risk, public education and possibilities for coastal inundation mapping.
River and Catchment Services Group Manager Scott Fowlds said New Zealand buildings may well be lighter in construction that some block wall constructions destroyed in Asia.