Environmental scientists see flora, fauna and phenomena the rest of us rarely do. In this series, we’ve invited them to share their unique photos from the field.


Extreme storms can cause devastating erosion and leave beachfront houses teetering on cliff edges. But our new research, published today, finds storms might also help replenish beaches by bringing in new sand from deeper waters.

We studied three extreme storms in Australia, the United Kingdom and Mexico. One, in Sydney in 2016, famously ripped a swimming pool away from a property overlooking the coastline.

For the first time, we’re able to show just how much new sand can be added to a beach in a single storm alone – over 400,000 cubic metres in some cases. That’s equivalent to the typical volumes of sand engineers use to nourish beaches artificially.

As sea levels rise, this natural form of beach replenishment might be an important factor in offsetting some of the damaging effects of climate change on beaches. Yet, with little knowledge of exactly how much sand is moving around offshore, predicting the future of beaches in the coming decades is extremely difficult.

‘like 20 tip trucks pouring sand on every metre-wide  strip’: how extreme storms can replenish beaches, not just erode them

Damaged houses at Collaroy Beach, Sydney in the wake of an extreme storm in June 2016. UNSW Water Research Laboratory, Author provided

‘like 20 tip trucks pouring sand on every metre-wide  strip’: how extreme storms can replenish beaches, not just erode them

While extreme storms can cause major erosion to beachfront properties, they can also bring in new sand from deeper water. UNSW Water Research Laboratory, Author provided

Wave after wave

Violent storm waves strip beaches of sand above the waterline, which often erodes sand dunes. In deeper waters, however, these same waves help stir up sediment lying dormant on the seabed. This sand is then pushed towards the shore and settles as the storm passes.

To study the three storms in Australia, the UK and Mexico, we used high-resolution monitoring equipment including twin engine airplanes, drones and jet skis mounted with an echo-sounder for measuring the seabed.

‘like 20 tip trucks pouring sand on every metre-wide  strip’: how extreme storms can replenish beaches, not just erode them

The UK survey team measuring sand volumes along the coast of Cornwall. University of Plymouth, Author provided

‘like 20 tip trucks pouring sand on every metre-wide  strip’: how extreme storms can replenish beaches, not just erode them

A combination of high-resolution survey equipment was used to measure changes to the beach. University of Plymouth, Author provided

In Australia, we measured Narrabeen Beach in Sydney. In the UK, we monitored the impact of several storms during the winters of 2013-2014 and 2015-2016, at Perranporth beach in Cornwall. And in northwest Mexico, we recorded the impact of the 2018-2019 winter on La Mision Beach.

In the time-lapse video below, you can see just how quickly the water can encroach on beachfront houses during extreme storms. Beneath the water surface, however, huge volumes of sand is also moving about.

‘like 20 tip trucks pouring sand on every metre-wide  strip’: how extreme storms can replenish beaches, not just erode them

A time-lapse of severe coastal erosion at Narrabeen-Collaroy Beach (SE Australia) during the June 2016 East Coast Low.
Source: Mitchell Harley (author provided)

By capturing the three-dimensional seabed changes for each event, we could quantify for the first time the precise sand volumes mobilised during these extreme storms.

To give an indication of the scale of beach change, the amount of sand added to the beach resulting from the stormy periods was on the order of 100 cubic metres for every metre length of beach – that’s like 20 tip trucks pouring sand on every metre-wide strip.


As the beaches spanned several kilometres, this amounted to 130,000 cubic metres for La Mision beach, 400,000 cubic metres for Narrabeen and 420,000 cubic metres for Perranporth.

The time-lapse video below is of Wamberal Beach during a storm in 2020. While it wasn’t included in our study, it’s another great example of how large storm waves cause abrupt changes to beaches.

Source: UNSW Water Research Laboratory (author provided)

Rethinking coastal erosion

Exactly how a coastline might change due to sea-level rise is a key question facing coastal managers, as they plan for the escalating impacts of climate change.

The Intergovernmental Panel for Climate Change projects global sea levels to rise up to 76 centimetres by 2100, under a middle-of-the-road emissions scenario where global temperatures rise 2.1-3.5℃.

The response of the coast to sea-level rise has previously been estimated using an approach known as the Bruun rule. This rule states that for a given metre of sea-level rise, the coastline is expected to retreat between around 20m to over 100m, depending on the steepness of the coast.

‘like 20 tip trucks pouring sand on every metre-wide  strip’: how extreme storms can replenish beaches, not just erode them

UNSW researcher Chris Drummond launching a drone to survey the beach in Sydney. UNSW Research Laboratory, Author provided

Using the Bruun rule, global sea-level rise caused by climate change has been projected to result in losing almost half the world’s sandy beaches by 2100. However, not all coastal scientists share this view.

Let there be no doubt: sea-level rise is a tragic consequence of climate change, and it poses an existential threat to many coastal communities, especially for island nations in the Pacific.

‘like 20 tip trucks pouring sand on every metre-wide  strip’: how extreme storms can replenish beaches, not just erode them

Mexico’s La Mision beach, on a calm day. In the winter of 2018-2019, research found that storms pushed 130,000 cubic metres of new sand into the beach system. Autonomous University of Baja California, Author provided

What our new research confirms is that the Bruun rule approach is overly simplistic, as it doesn’t take into account the many complex local factors about how individual beaches respond to sea-level rise.

This includes the amount of sand stored in deeper water immediately off the coast, and its potential to replenish beaches during extreme weather events.

‘like 20 tip trucks pouring sand on every metre-wide  strip’: how extreme storms can replenish beaches, not just erode them

Understanding how sand moves along the coast is critical for better coastal planning. UNSW Water Research Laboratory, Author provided

Improving predictions in an uncertain future

While this research has focused only on three extreme storm sequences, it shows that understanding how sediment moves along the coast is fundamental to planning for climate change impacts.

There are two ways we can significantly improve long-term predictions of coastal change in this uncertain future:

    upscaling efforts in mapping the seabed to learn how much sediment is presently stored in the deeper coastal waters

    increasing routine coastal monitoring of the entire nearshore system, from the sand dunes down to deeper waters. This is currently carried out by UK coastal observatories.

A greater understanding of sand movements off the coast, combined with computer modelling, can better forecast future shorelines. This will give coastal managers the information needed to make critical long-term planning decisions for communities.

NEWS RELATED

Yes, Weatherstripping Can Lower Your Utility Bills

This simple process can keep you more comfortable while spending less on air conditioning.

View more: Yes, Weatherstripping Can Lower Your Utility Bills

After many false dawns, Australians finally voted for stronger climate action. Here’s why this election was different

Before the 2019 federal election, many people expected Australia would vote for faster climate action. That, of course, didn’t happen. But just three years later, the climate election arrived at last. The question is – what changed? In short: Reality hit. Over the Morrison government’s term, the east coast was ...

View more: After many false dawns, Australians finally voted for stronger climate action. Here’s why this election was different

The election shows the conservative culture war on climate change could be nearing its end

Former Treasurer Josh Frydenberg’s shock loss to an independent running on a climate action platform wasn’t a fluke event. “Teal” independents have ousted five of Frydenberg’s colleagues, all harvesting votes from conservative heartland and all calling for more action on climate change. Amid the wreckage, Frydenberg was asked whether the ...

View more: The election shows the conservative culture war on climate change could be nearing its end

What Is Net Metering and How Does It Work?

The ways utilities pay you for the energy your rooftop solar makes vary, though there are a few essentials you should know.

View more: What Is Net Metering and How Does It Work?

Good timing and hard work: behind the election’s ‘Greenslide’

During Saturday’s election, 31.5% of the voters deserted the major parties, with a swag of female teal independents tipping Liberal MPs out of their heartland urban seats. By contrast, the underestimated Greens had a sensational election, surprising many pundits with the strength of their support. Even though their lower house ...

View more: Good timing and hard work: behind the election’s ‘Greenslide’

Don’t believe the backlash – the benefits of NZ investing more in cycling will far outweigh the costs

The Dutch have long been recognised as leaders in cycling. Denmark is not far behind, with more bikes than cars in its capital Copenhagen. This is the result of many years of investment. Even the UK, with less of a cycling tradition, is investing and showing growth in cycling. New ...

View more: Don’t believe the backlash – the benefits of NZ investing more in cycling will far outweigh the costs

Set Your Thermostat to This Temperature Right Now to Save Money This Summer

There are ways to keep your home cool without getting hit with costly bills.

View more: Set Your Thermostat to This Temperature Right Now to Save Money This Summer

Unplug These Home Appliances to Save Money and Electricity

High electric bill? Consider unplugging some devices around your home.

View more: Unplug These Home Appliances to Save Money and Electricity

Ecobee Smart Thermostat Premium vs. Ecobee Smart Thermostat Enhanced: Which One Should You Pick?

How to Stop Air Conditioning From Leaking Outside

We identified the 63 animals most likely to go extinct by 2041. We can’t give up on them yet

The election showed Australia’s huge appetite for stronger climate action. What levers can the new government pull?

Leave the Generator, Take the Power Station

Solar Panel Scams: How to Avoid Them and the Biggest Red Flags

Lower Your Electric Bill This Summer With These Air Conditioning Tips

Battery Backup vs. Generator: Which Backup Power Source Is Best for You?

Should You Go Solar if You Live on the East Coast: What You Want to Know

The teals and Greens will turn up the heat on Labor’s climate policy. Here’s what to expect

The teals and Greens will turn up the heat on the new Labor government’s climate policy. Here’s what to expect

Ecobee's Smart Thermostat Enhanced Has All the Basics at a Premium Price

OTHER NEWS