Tsunami Hazard Assessment in New Zealand Ports and Harbors

The New Zealand Ministry of Science and Innovation (MSI) has sponsored a 3-year collaborative project involving industry, government and university research groups to better assess and prepare for tsunami hazards in New Zealand ports and harbors. As an island nation, New Zealand is highly dependent on its maritime infrastructure for commercial and recreational interests. The recent tsunamis of 2009, 2010 and 2011 (Samoa, Chile and Japan) highlighted the vulnerability of New Zealand's marine infrastructure to strong currents generated by such far field events. These events also illustrated the extended duration of the effects from such tsunamis, with some of the strongest currents and highest water levels occurring many hours, if not days after the tsunami first arrival. In addition, New Zealand also sits astride the Tonga-Kermadec subduction zone, which given the events of recent years, cannot be underestimated as a major near field hazard. This presentation will discuss the modeling and research strategy that will be used to mitigate tsunami hazards in New Zealand ports and harbors. This will include a detailed time-series analysis (including Fourier and discrete Wavelet techniques) of water levels recorded throughout New Zealand form recent tsunami events (2009 Samoa, 2010 Chile and 2011 Japan). The information learned from these studies will guide detailed numerical modeling of tsunami induced currents at key New Zealand ports. The model results will then be used to guide a structural analysis of the relevant port structures in terms of hydrodynamic loads as well as mooring and impact loads due to vessel and/or debris. Ultimately the project will lead to an improvement in New Zealand's tsunami response plans by providing a decision making flow chart, targeted for marine facilities, to be used by emergency management officials during future tsunami events.Tsunami effects at Port Charles, New Zealand: (top) inundation into a neighborhood and (bottom left and right) tsunami induced currents and surface agitation. The small jetty indicated with the arrow is overtopped in the second image (indicated by the oval)