Nature is often surprising. Extreme storms, which are becoming more frequent due to climate change, are damaging coasts, dunes, property and infrastructure.. But science has discovered the other side, the positive side: Help protect beaches from the impact of rising sea levels by bringing fresh sand from deeper waters or nearby beaches.
The study, which provides new insight into extreme storms, was led by Mitchell Harley of the University of New South Wales’s Water Research Laboratory and published in the journal Nature Communications Earth & Environment.
“A great storm of extreme coastal erosion and damage coastal property. But for the first time, we’re looking not just above the water, where the effects of extreme storms are easily visible, but also below the water,” says Harley.
What the researchers found was this: During these events, hundreds of thousands of cubic meters of sand enter the beach systems.something like the scale that engineers use to artificially feed a beach.
“This may be enough to offset some of the effects of sea level rise caused by climate change (estimated between 0.63 and 1.01 meters by 2100), such as the retreat of the coasts. Even in the long run. It’s a new way to look at extreme storms,” says Harley.
The study, in collaboration with researchers from the University of Plymouth and the Autonomous University of Baja California, examined three coastlines in Australia, the United Kingdom and Mexico. Each suffered a series of extreme storms or prolonged storm clusters, followed by a milder beach recovery period.
Very significant sand losses
In Australia, researchers surveyed Sydney’s Narrabeen Beach after a 2016 storm that ripped a swimming pool from a private property overlooking the coastline, among other damage. Using high-resolution measurements of the beach and seafloor, the scientists demonstrated that: sediment gains were “sufficient to theoretically offset decades of projected coastline retreat”.
“For the first time, we were able to mobilize special monitoring equipment to get precise measurements before and after a storm, and we found the volume of sand carried in each,” Harley recalls.
In the UK, scientists have been monitoring Perranporth beach in Cornwall since 2006. There, the impact of extreme winters in 2013/14 and 2015/16 Significant loss of sand from the intertidal beach and dune system. But in 2018, the beach gained 420,000 cubic meters of sand.
“We’re not entirely sure where this extra sand is coming from, whether it’s from nearby beaches, deep water, or both, but we now understand that excessive waves can potentially contribute positively to the amount of sanddespite the erosion of the sand dunes and the upper coast,” says Gerd Masselink, who participated in the study.
One of the most important questions facing coastal managers and scientists is how much a coastline can change due to sea level rise. the increasing effects of climate change.
Bruun’s rule, old
In the past, it was estimated using a simple approach known as ‘.Bruun’s rule‘ indicates that for a given sea level rise, the coastline is expected to recede by about 20 to 100 meters depending on the slope.
Using Bruun’s rule, Global sea level rise caused by climate change will cause a major regression or disappearance of almost half of the world’s sandy beaches by the end of this century..
Professor Masselink added, “However, Bruun’s rule has been criticized for its simplicity as it does not take into account the many complex factors of how individual beaches respond to sea level rise.”
One such factor is the presence of sand stored in deep waters offshore and its potential to move during extreme weather events. Study authors believe that Extreme storms should also be considered in long-term forecasts of coastal sedimentary movements..
From now on, they argue, analyze coast by coast predicting how each will change as sea level rise continues. But just offshore there is so little measurement of the seafloor that it’s hard to know how much sand could potentially be mobilized in the futurethey add.
“We’re just scratching the surface. We need to repeat these types of measurements under a variety of conditions for more storms and different coastal environments. Only then will we know. the amount of sand stored offshore that can help buffer the effects of sea level riseand a clearer picture of what our beaches will look like in 2100 and beyond,” said Haley.
Reference work: https://www.nature.com/articles/s43247-022-00437-2
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