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Stormy seas help protect beaches from sea level rise

It turns out extreme sea storms which damage pricy coastline property may help combat sea level rise-induced shoreline erosion in the future.

(CN) — Seaside property owners grumbling about cleaning up storm wreckage today may be grateful for extreme ocean storms in the future: Researchers have found the weather events could help protect beaches from sea level rise and erosion.

An international study published Thursday in Nature Communications Earth & Environment shows extreme ocean storms may help protect beaches from the impacts of sea level rise by bringing in new sand from deeper water or from nearby beaches.

The international study was led by Dr. Mitchell Harley from the University of New South Wales water research laboratory.

“We know that extreme storms cause major coastal erosion and damage to beachfront properties,” Harley said in a statement, adding, “For the first time we looked not just above water, where the impacts of extreme storms are easy to see, but also deep down below the water as well.”

Harley said when researchers looked beneath the water’s surface they found hundreds of thousands of cubic meters of sand entered beach systems during the storms – equivalent to the scale of what engineers use to artificially supplement sand loss on coastal beaches.

“This could potentially be enough to offset some of the impacts of sea level rises caused by climate change, such as retreating coastlines, and by several decades in the long term,” Harley said.

Harley collaborated with researchers from University of Plymouth and Autonomous University of Baja California in Mexico to examine three coastlines across Australia, the United Kingdom and Mexico.

Each of the coastlines the researchers studied had experienced extreme storms or storm clusters followed by a milder period of beach recovery.

The researchers studied Narrabeen beach in Sydney, Australia, where, during a 2016 storm a swimming pool was ripped away from a property overlooking the coastline.

There, researchers used high-resolution measurements of the beach and seabed to show sediment gains were sufficient to potentially offset decades of projected shoreline erosion.

Harley said for the first time researchers were able to use specialized monitoring equipment to get accurate measurements before and after the storm.

They used a twin-engine airplane equipped with a Lidar scanner, drones and jet skis weaving back-and-forth along the coast taking measurements below the surface right before the storm hit.

In the UK, researchers of the Coastal Process Research Group at the University of Plymouth have studied Perranporth beach in Cornwall since 2006 using monthly beach topographic surveys and quasi-annual bathymetric surveys.

There, the impact of severe winter storms in 2013-14 and 2015-16 caused significant sand loss from the beaches and dunes.

But when researchers looked at the underwater part of the beach, they found by 2018 the beach had gained 420,000 cubic meters of sand.

“We are not quite sure whether this extra sand has come from offshore or from around the corner, or even both, but we do now understand that extreme waves can potentially contribute positively to the overall sand budget, despite causing upper beach and dune erosion,” Professor Gerd Masselink, who leads the Coastal Processes Research Group, said in a statement.

Researchers studying sea level rise previously estimated coastal erosion using a method called the Bruun rule which estimates for a meter of sea level rise, the coastline is expected to retreat between roughly 20 and 100 meters, depending on the steepness of the coast.

Using the Bruun rule, researchers have estimate global sea level rise caused by climate change will result in a loss of half of the world’s sandy beaches by the end of the century.

But the rule doesn’t take into consideration sand potentially stored in deeper waters offshore, according to the project researchers.

“It further reinforces that we really need to be doing a beach-by-beach understanding of how our beaches are going to change as global sea level rise continues,” Harley said.

He added that to get “a clearer picture of what our beaches could look like in the year 2100 and beyond” more extreme ocean storms need to be studied.

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Categories / Environment, Science

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