Sydney storm: Engineer says landslide could shift Collaroy beachfront another 10 to 12 metres

A COASTAL engineer says the full extent of damage to properties at Collaroy could be far worse than first thought - with a risk more land could be lost as sand dries out.

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IT COULD be at least another week before residents of a Collaroy strip ravaged by storms know the full extent of the structural damage to their properties.

A consultant engineer acting for the Northern Beaches Council told the Manly Daily there was a risk that even more damage could be done when the sand dries.

Angus Gordon said as the sand dried, it would create a landslide effect in which up to 12 metres of land could become loose.

Coastal engineer Angus Gordon at Collaroy. Picture: AAP

“There is a thing called the zone reduce foundation capacity and this is a well defined engineering term and it looks at how far back from where you have got a vertical escarpement,” he said.

“The foundations are still sound, and in these sorts of situations you are talking about 10 to 12 metres back from the front of the escarpment. So for those homes already over the top of the escarpment, that zone reduce foundation goes back into the houses. That is a concern.”

The sand would likely not completely dry out until next week due to tidal flow and weather patterns.

Flood damage from the air at Collaroy. Picture: Toby Zerna

It is still unknown if, or when, residents will be able to enter their homes as it has not yet been safe enough for them to get on the beachfront where the houses were worst affected.

In addition, power and water have been cut off for safety reasons and sewerage lines have been damaged.

He cautioned people to stay out of the water at Collaroy due to pathogens from broken sewer lines.

Yesterday morning, residents formed a committee to deal with their concerns and liaise with Northern Beaches Council on their behalf.

Devastation with broken sewerage, swimming pool etc on the beach destroyed at Collaroy where houses have been eaten by the ocean. Picture: Martin Lange.

The spokesman for the residents’ committee, Garry Silk, said while his property was likely to survive it was still a waiting game.

“Council said to us there has been some movement overnight as far as they could tell,” he said.

“But having said that, they have got the structural engineers in this afternoon to have a look at all the houses and determine what state they are currently in. That isn’t to say they will stay in that state because we have more high tides tonight.”

He said residents expected to get updates on their properties either last night or this morning.

In the meantime, residents have been put up in temporary accommodation provided by the council.

Garry Silk in front of his house which is so damaged he cannot return to it. At Collaroy where houses have been eaten by the recent storms. Picture: Marin Lange

Mr Silk said his neighbours were far from filthy rich. “There are people who are quite old who have lived here for some time and this is their only asset,” he said. “If they get orders to demolish, it is going to be devastating.”

The council yesterday met with affected residents to offer further clarification.

Northern Beaches Council general manager Mark Ferguson said works were still under way to determine the extent of damage.

“We are going to commence further inspection of individual properties to assess the suitability of what people can access,” he said.

In the next few days, residents will be issued with emergency orders.