Description: The West Coast Tsunami Evacuation Zones are to be used in tsunami response planning and in defining areas where people should be evacuated from. It is important to recognise that the West Coast Tsunami Evacuation Zones are not tsunami hazard zones, tsunami risk zones, or tsunami inundation zones. They are areas that we recommend people evacuate from as a precaution after natural warnings, or in an official tsunami warning.
The West Coast Tsunami Evacuation Zones are in the process of being upgraded as there are many uncertainties involved including knowledge of potential tsunami sources, source characteristics, bathymetry and topography, tsunami propagation and inundation characteristics. For these reasons the data provided cannot be relied for any reason other than informing evacuation in the event of a threat from a tsunami.
All viewers of these zones need to be aware that the New Zealand Coastal Policy Statement (Department of Conservation 2010) sets out national policy under the Resource Management Act 1991 (RMA) for managing areas potentially affected by coastal hazards, which includes the potential effects of tsunami, and how to avoid or mitigate them. However other than evacuation planning, the West Coast Evacuation Zones supplied by the West Coast Civil Defence & Emergency Management Group cannot be used for any other purpose such as requirements for subdivision, development, land-use and tsunami risk assessment due to the inaccuracy of the information used to create these zones.
Additional to the inaccuracy and uncertainty of the provided zones, there is a lot of uncertainty around how tsunamis will behave, particularly large tsunamis, as we have not experienced many of these in our short written history. Every tsunami is different depending on its source, the direction it is arriving from, and the sea state and tide at the time. There is no one tsunami that would inundate an entire zone. Rather, the zones represent an ‘envelope’ around many different possible tsunami scenarios. Inevitably this will lead to some degree of over-evacuation in any tsunami event. However, it is much more practical and simple from a planning and communications point of view to have three zones based on some set criteria, rather than hundreds of zones, each based on a possible scenario.
Should you have questions please contact the West Coast Civil Defence & Emergency Management Group at info@westcoastemergency.govt.nz .