Remedial work carried out several months ago may have saved a toilet block falling into the sea after high waves gouged away a grassed reserve at Sandy Bay.
Whangarei District Council (WDC) had placed boulders along part of the stream bank below the toilet block on the reserve at the north end of the beach.
In recent weeks strong easterlies and full tides have driven surf higher than usual up the stream mouth, undercutting the bank and causing the strip of reserve to slip.
Dave Gould, whose house overlooks the stream mouth, said it was the worst erosion he had seen in the 10 years he has lived at Sandy Bay.
Mr Gould said the surge of sea water coming into the stream mouth had done the damage, rather than rainwater and run-off washing downstream.
The council's work had prevented worse damage, he said. The stream's course changed about 12 months ago and its new opening to the beach, combined with tide action, had caused a build-up of sand at the beach's northern end.
The council's remedial plans include extending the boulder bank.
At the height of the extended pattern of easterly winds and high water, little damage had occurred on the Tutukaka Coast, although WDC parks and reserves manager Paul McDonald said at the time that staff were keeping a close eye on Sandy Bay.