Nature holds surprises as storms escalate with climate change, battering coasts, dunes, property and infrastructure. Yet science also reveals a silver lining: fresh sand can be delivered to beaches from deep waters or nearby shores to counter rising sea levels.
The study outlining this new insight into extreme storms was led by Mitchell Harley of the University of New South Wales’s Water Research Laboratory and published in Nature Communications Earth & Environment.
“A major storm can erase coastal property. But for the first time, we’re looking not just at what happens above water, where damage is obvious, but also beneath the surface,” Harley notes.
The researchers found that during these events hundreds of thousands of cubic meters of sand flow into beach systems, a scale engineers sometimes use to artificially replenish beaches.
“This could offset some of the effects of sea level rise expected this century, roughly 0.63 to 1.01 meters by 2100, especially coastal retreat,” Harley says. “Even in the long term, it opens a new lens on how extreme storms shape coastlines.”
The study involved researchers from the University of Plymouth and the Autonomous University of Baja California and examined three coastlines across Australia, the United Kingdom, and Mexico. Each experienced a sequence of extreme storms or long storm clusters, followed by a period of milder beach recovery.
Very significant sand losses
In Australia, the team surveyed Narrabeen Beach in Sydney after a 2016 storm that ripped a pool from a house overlooking the shore, among other damage. With high-resolution measurements of the beach and seabed, the scientists showed that sediment gains were sufficient to theoretically offset decades of projected coastline retreat.
Patacona Beach in Valencia was also observed as part of the field record, illustrating similar dynamics in a different coastal setting.
“For the first time, we could mobilize specialized monitoring gear to measure the pre- and post-storm conditions with precision, and we quantified the sand volume carried by the events,” Harley recalls.
In the United Kingdom, researchers have tracked Perranporth Beach in Cornwall since 2006. Winter storms in 2013/14 and 2015/16 caused substantial sand loss from the intertidal zone and dune system, yet by 2018 the beach had gained about 420,000 cubic meters of sand.
“We’re not entirely sure where this extra sand originates—whether from nearby beaches, deep water, or both—but there is growing evidence that excessive waves can contribute positively to sand supply even as dunes erode,” says Gerd Masselink, a co-author of the study.
One of the central questions for coastal managers is how much a coastline can change under rising seas. Bruun’s rule, an older model, suggested a straightforward relationship between sea level rise and coastline retreat along with the slope of the shore.
Historically, Bruun’s rule hinted that sea level rise would push coastlines back by roughly 20 to 100 meters, depending on local conditions. Projections based on this rule suggested that global sea level rise could lead to substantial loss of sandy beaches by the end of the century.
Posters forecasting sea level rise illustrate the pressure on shorelines, yet Masselink notes that Bruun’s rule has drawn criticism for its simplicity. It does not capture the complex responses of individual beaches to changing water levels.
One important factor is the presence of offshore sand stores and their movement during extreme weather. The study’s authors argue that extreme storms should be included in long-term forecasts of coastal sediment transport and beach evolution.
From now on, they say, coast-by-coast analyses are needed to predict how each shoreline will respond as sea level continues to rise. But offshore measurement is sparse, making it hard to gauge how much sand could be mobilized in the future.
“We’re just scratching the surface. Repeating these measurements across varied storm conditions and coastal environments is essential to understanding how much sand stored offshore can buffer sea level rise and what beaches will look like in 2100 and beyond,” says Harley.
Reference work: Nature Communications Earth & Environment. This article synthesizes the findings and their implications for coastal science and management. Citation: Nature Communications Earth & Environment.
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