By Wendy Saunders, Gegar Prasetya, Graham Leonard
On the 13 March 2011 a devastating tsunami hit the north-east coast of Japan. This tsunami, shown in real time on TV, showed the almighty power and destruction a tsunami can have, even with thorough preparation. World-wide, Japan was considered a leader in tsunami modelling, engineering mitigation (such as tsunami river defences and sea walls), warning systems, evacuation planning and community involvement in evacuation exercises. Regardless of all this emergency management preparation, it was the land use that dictated the consequences of the tsunami.
Prior to the Japanese event, researchers at GNS Science were drafting a methodology for integrating tsunami modelling into land use planning – an initiative that could save lives from a similar event in New Zealand (of which we are exposed to from the Hikurangi Trench to the Kermadecs). As issues of health and safety form part of the purpose of the RMA, the tsunami risk to coastal communities needs to be incorporated into land use planning. This guide is now available to all those interested in reducing the risks from tsunami in New Zealand through land use planning.
The report provides a brief overview of tsunami basics, followed by a decision tree for including tsunami risk into land use planning, which forms the basis of the report. The purpose of the decision tree is to lead the decision maker through a process of tsunami modelling, risk assessment, review of data quality and inclusion into Land Information Memorandums (LIMs), emergency management, and land use planning.
Guidance on tsunami modelling levels for evacuation purposes is already available from the Ministry of Civil Defence and Emergency Management. To ensure consistency with this approach, the recommended modelling levels for land use planning are based on the same approach. Level 1 modelling is not recommended for land use planning purposes; Level 2 modelling is recommended for inclusion into LIMs and emergency management readiness; and Levels 3 and 4 are also recommended for land use planning purposes. Pre-event recovery planning for land use is also recommended for areas already developed.
Options are provided on how the Level 3 and 4 modelling can be incorporated into land use planning. Other topics include managing uncertainty, including one potential solution for mapping tsunami inundation zones that acknowledges scientific uncertainty. Three planning approaches are available, and can be used in combination: risk-based approach, precautionary approach, and participatory approach. An adaptive three-step risk-based approach is outlined, which involves determining severity of consequences; evaluating the likelihood of an event occurring relevant to the consequences; then the resource consent activity status is determined based on quantifying levels of risk. Resource consents become more restrictive as the consequences increase. Regulatory and non-regulatory options for including tsunami risk into land use planning are outlined.
The report is available online at http://www.gns.cri.nz/Home/Our-Science/Natural-Hazards/Active-Partnerships/Policy-and-Planning; for a high resolution copy, please contact the authors. Funding for the project was provided by the EQC and Bay Of Plenty Regional Council with additional support from BRANZ and the Zonta Club of Wellington.
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