Significant surges, coastal erosion and closed boat ramps are among the effects of the Tongan volcano eruption on the Bay of Plenty's East Coast.
The Thames-Coromandel District Council said wave periods of 12-30 seconds had been observed.
Twelve seconds is considered a "high energy" surge.
"High energy waves can be dangerous" regardless of their height, said the council's emergency management manager Garry Towler.
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"People should avoid going out in this."
Purangi Boat Ramp at Cook's Beach and Whangamatā wharf were closed last night amid "wild tidal currents", said the council.
Purangi will remain closed until at least Wednesday, when some of the pontoons will be removed for safety. Contractors will be arriving tomorrow to further assess the damage to the ramp.
The council said "inundation" - when low-lying, dry coastal land is flooded - had been minimal at this stage.
Inundation continued to be monitored in areas where erosion was a risk.
Some erosion had occurred at Buffalo Beach in Whitianga, but sandbags had prevented the surges from damaging the road.
The council urged residents to remain up to date on coastal risks through the rest of the week by visiting its website or Facebook page.