A 2015 study to identify the risk of tsunami affecting Port Waikato, Raglan Harbour and Aotea Harbour has found wave heights will be relatively small, but inundation (flooding) may affect low-lying areas.
Despite the low likelihood of a tsunami event in these areas, tsunami may produce strong surges and currents, particularly at the entrance to the harbours, making it dangerous to be on or in the water.
The study focused primarily on tsunami generated by very large (Magnitude 9) earthquakes on known fault systems in and around the Tasman Sea and South West Pacific. This included tsunami generated by earthquakes in the Solomon Islands, along the New Hebrides trench directly north of New Zealand, along the Tonga-Kermadec trench to the east of the North Island and along the Puysegur Trench to the south and west of the South Island.
The study has also considered tsunami generated along the west coast of South America, focusing on the largest known historical events of 1868 and 1960 – each with earthquake magnitudes greater than 9 – in northern and southern Chile respectively.
The tsunami study has found that for the Waikato west coast:
Despite the relatively small tsunami heights, all of the scenarios produced potentially dangerous currents particularly at the entrance to each harbour. In each case, these dangerous currents continued for many hours.
The study, funded by Waikato District Council, Waikato Regional Council and WEL Networks, was carried out by Jose Borrero of Raglan-based international marine and freshwater experts, eCoast.