Tsunami Modelling Study 1

Executive Summary

Northland Regional Council contracted NIWA to undertake an initial study on the risk of tsunami inundation facing communities in the Northland Region.

The following credible sources were identified:

  • Remote source: South American origin. Return period 50-100 years. This represents the most probable tsunami risk in the next 100 years.
  • Local/Region: Tonga Kermadec. Two events were modelled, Mw 8.5 and Mw 9.0. The return period of these events is much longer (500-2000 years) but these represent a worst-case scenario for a tsunami striking the Northland coast.

These scenarios were run up to the coastline to provide maximum water heights and speeds at the coast for specific districts. Additional inundation modelling was done for the specific communities of Taipa and Ahipara.

The remote South American tsunami did not cause significant inundation for Taipa and Ahipara, however high water speeds could cause erosion of dunes and scouring of estuaries.

The Tonga- Kermadec subduction zone tsunamis caused considerable inundation (especially the larger of the two) and the high water levels would cause extensive erosion and scouring of these two communities.

These effects are further exacerbated by the sea level rise scenarios for 50 and 100 years as projected the IPCC Fourth Assessment Report.

Download the report

File size: Please note that this report is very large due to the number of maps and graphs. It has been separated into sections to make it easier to download. The Table of Contents .pdf outlines what information is in each section. 

Find out what a tsunami is and what we are doing to prepare for managing one if it does happen: