Aussies warned after cliff collapses under beachfront homes: 'Too close'

Living on the beachfront is a dream of many, reflected in the growing populations found across the nation's coastal cities — but the reality of this dream is that it comes with some serious risks.

Nerve-wracking scenes of a collapsed cliff edge swept away in recent storms and leaving three large homes sitting close to the edge of a 150-foot drop in California, have reignited discussions about the threat of coastal erosion.

Each of the homes at Dana Point, Orange County are estimated to be worth at least $20 million each and miraculously they have been assessed as still safe to live in for now, despite the cliff giving way beneath them.

Cliff erosion a reminder of coastal danger in Australia

The footage is reminiscent of scenes from Wamberal Beach on the NSW Central Coast in 2020 when there were fears homes on the water's edge would fall into the ocean following powerful east coast storms.

As more people try and score a home by the sea in coming years, coastal engineering expert Dr Mitchell Harley from the UNSW warns it's something "we have to try to manage" — the demand versus the need for development.

"Unfortunately, we still see examples of inappropriate planning. Coastal populations are getting bigger and everybody wants to live near the coast," he told Yahoo News.

Harley said historical poor planning has meant numerous homes and infrastructure have been developed "too close" to the coastline but this poor planning still happens today.

"That's inevitably causing greater challenges with coastal erosion, and particularly in the future with concerns about the extent to which sea levels will rise," he said. "We need to ensure that we're not creating these [same] legacy issues for future generations to deal with like we have been."

Erosion set to accelerate as sea levels rise

Coastal erosion is "basically a reduction in the coastline" and can occur during extreme storms or over a longer time period.

While coasts "naturally come and go", rising sea levels will change the way this happens as time goes on. "At the moment sea levels are rising at a rate of 3-4 millimetres per year, Harley explained. "We haven't quite seen the effects of that in terms of coastal erosion. But, at a certain point, there will be all the signs pointing to acceleration in the latter half of this century."

The Department of Climate Change, Energy, the Environment and Water's (DCCEEW's) National Coastal Risk Assessment states erosion due to higher sea levels is a "key risk" for coastal areas. "Nationally, nearly 39,000 residential buildings within 110 metres of coastlines are susceptible to erosion, of which nearly 40 per cent are located in Queensland," it says.

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Coastal flooding an immediate concern

Australia is already seeing "some effects" of sea level rise in terms of flooding, explains Harley. "We're likely to see the effects of more and more flooding first, before we see extreme coastal erosion.

"Particularly, we've got so many low-lying housing developments around our coastal estuaries. Coastal towns [are] always built on the rivers and so forth."

Just small amounts of sea level rise can mean a "significant" increase in flooding with floods from king tides increasing over the last few decades. "It is only going to get worse."

Some of Australia's most at-risk coastal locations

There are a number of spots up and down the east coast of Australia and in Western Australia that are known as "hot spots" for coastal erosion. These include, but are not limited to:

• Cronulla, Sydney, NSW

• Paradise Point, Gold Coast, QLD

• Collaroy, Sydney, NSW

• Rottnest Island, WA

• Wamberal Beach, Central Coast, NSW

• Clarkes Beach, Byron Bay, NSW

• Port Beach, Perth, WA

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