Dodged a bullet NSW coast battered by one-in-40-year waves

The NSW coast faces several more days of hazardous surf after a powerful low-pressure system churned up huge waves and a storm surge seen only once every couple of decades.

A buoy in Botany Bay registered significant wave heights reaching 8.44 metres, an event that would typically be seen about once in 40 years, said Mitchell Harley, a senior lecturer in the University of NSW’s Water Research Laboratory.

Children hold the fence chains at North Narrabeen rockpool as huge waves hammer the Sydney coast and other parts of NSW.Credit:Nick Moir

The storm surge was about 47 centimetres, or about a one-in-20-year event, Dr Harley said, adding “we kind of dodged a bullet”.

Beach erosion could have been much worse had Tuesday night’s big storm coincided with king tides, or if the angle of the waves had been about 30 degrees further to the east. Instead, the waves were mostly from the south, hitting parts of the coastline that tend to get hammered more regularly, he said.

Ed Couriel, director of Manly Hydraulics Laboratory, said the waves were not quite as big as had been forecast, which might have put them close to the heights of a big storm in 1974 that caused a lot of damage to beaches.

The storm system also formed close to the coast and moved away quickly. With a longer range for the waves to develop given the strong winds, the impacts would have been more dramatic, he said.

Even so, some South Coast beaches reported heavy erosion, such as the south-facing Callala Beach near Jervis Bay.

Beach erosion at Callala Beach near Jervis Bay. The main beach faces south from where the big waves rolled in.Credit:Catherine Naylor

Residents reported heavy erosion in places and even a yacht washed on the sand. The storm also took out the electricity for many households.

Maroubra, in Sydney’s east, copped a large swell, as did most of the coast down to the Victorian border.Credit:Rhett Wyman

The Bureau of Meteorology has issued a warning for hazardous surf for the Hunter coast for Wednesday. Similar conditions will persist for the Sydney coast down to the border on Thursday and Friday.

The storm dumped about 80 millimetres on Sydney in about a day, coming close to the typical rainfall expected in the whole of August.

The deep low also produced strong winds. Kiama, south of Sydney, had gusts of 130km/h with Montague Island, further south, not far behind with gusts of 128km/h

Wollongong also notched a 120km/h wind reading, with Jervis Bay Airfield collecting 107km/h and Ulladulla 100km/h, the bureau said.

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Peter Hannam writes on environment issues for The Sydney Morning Herald and The Age.

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