Extreme storms could help PROTECT beaches from sea level rise by bringing in new sand from deeper waters, study finds
- Violent coastal storms are often thought to cause extensive damage to beaches
- But a new study shows they could help protect beaches from sea level rise
- This is because turbulence pulls up vast quantities of sediment from deep waters
- The sediment helps to replenish damaged beaches
Extreme storms could help protect beaches from sea level rise by bringing in new sand from deeper waters, a new study claims.
Images in the wake of violent coastal storms often focus purely on the damage caused to beaches, dunes, property, and surrounding infrastructure.
However, these extreme weather events could help offset erosion to beaches caused by rising sea levels, by pulling up vast quantities of sediment from the ocean floor and depositing it along retreating shorelines.
Climate change is projected to cause a global sea level rise of between 25in (63cm) and 40in (101cm) by 2100, based on a scenario where future greenhouse gas emissions are at the high end of current modelling.
Global warming is also expected to increase wave heights during extreme weather events along almost three-fifths of the world’s coastlines by the end of the century.
But the researchers said the findings could potentially change long-term predictions about the future of our coastlines.
They found that quantities of sand deposited naturally along the coastlines in the study match the amounts required by engineers for artificial ‘beach nourishment’ projects used to combat erosion.
Researchers studied Narrabeen beach in Sydney (pictured) in the wake of a 2016 storm, which ripped a swimming pool away from a property overlooking the coastline
Researchers used a combination of monthly beach topographic surveys and quasi-annual bathymetric surveys to study the impact of extreme weather events on beaches
More tropical cyclones could hit cities because of rising temperatures
Rising temperatures brought about by climate change could see more tropical cyclones striking populous mid-latitude cities like Beijing, New York and Tokyo.
Research by Yale University-led experts suggests that global warming will reduce the temperature differential between the equator and the poles.
This, they warn, could weaken the jet stream at mid-latitudes, allowing cyclones to form — by 2100 — over a wider range than they have in the last 3 million years.
The ability for more tropical cyclones to form at mid-latitudes, where most of the world’s population lives, will place millions more within their devastating reach.
The research was led by the University of New South Wales (UNSW) in Australia, in collaboration with academics from the University of Plymouth, and the Autonomous University of Baja California.
‘We know that extreme storms cause major coastal erosion and damage to beachfront properties’, said Dr Mitchell Harley, Senior Lecturer from the University of New South Wales’ Water Research Laboratory, who led the study.
‘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.
‘What we found was that hundreds of thousands of cubic metres of sand was entering these beach systems during these events – that’s similar to the scale of what engineers use to nourish a beach artificially.
‘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.
‘It’s a new way of looking at extreme storms.’
The study looked at coastlines in Australia, the UK and Mexico, which had each been subject to a period of extreme storms followed by a period of milder weather and beach recovery.
In Australia, scientists focused on Narrabeen Beach in Sydney following an major storm in 2016, which was powerful enough to rip a swimming pool away from a coastal property.
Measurements of the beach and seabed showed that, in theory, the sediment gain from heavy weather was enough to offset decades of projected shoreline retreat.
In the UK, researchers collected monthly data from Perranporth Beach on the north Cornwall coast since 2006, as well as an annual survey of water depth.
Perranporth was hit by extreme weather over the winters of 2013-2014 and 2015-2016, resulting in significant loss of sand from the beach and surrounding dunes.
But by 2018 the beach had gained 420,000 cubic metres (549,339 cubic yards) of sediment.
The researchers said that, while the dataset was limited, it could reshape predictions about our coastlines.
Graphic shows the key sediment transport pathways under normal and extreme wave conditions on a sandy beach. Red arrows denote sediment transport pathways during extreme storm conditions and black arrows during less-energetic modal conditions. Example cross-sections at three locations in the beach compartment are: A. a rocky headland with sandy bed above the depth of closure (DoC); B. a completely sandy beach system; and C. a rocky headland with sandy bed below the depth of closure.
But they warned that, because there are few measurements of the seabed in coastal waters, it is difficult to tell how much sand could be deposited along the shore in future.
Dr Mitchell Harley, of UNSW’s Water Research Laboratory, said: ‘What we found was that hundreds of thousands of cubic metres of sand was entering these beach systems during these events – that’s similar to the scale of what engineers use to nourish a beach artificially.
‘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. It’s a new way of looking at extreme storms.’
Professor Gerd Masselink, who leads the Coastal Processes Research Group at the University of Plymouth, said: ‘Looking at the extra sand gained by the beach at Perranporth, we are not quite sure whether this has come from offshore or from around the corner, or even both.
‘However, we do now understand that extreme waves can potentially contribute positively to the overall sand budget, despite causing upper beach and dune erosion.
‘We have previously shown that coral reef islands could naturally adapt to survive the impact of rising sea levels, and this study shows the changes to our own coastlines could mean the impact of extreme storms are not wholly negative.’
The study has been published in the journal Nature Communications Earth & Environment.
EARTH’S WATER CYCLE IS SPEEDING UP
Earth’s water cycle is speeding up due to climate change, according to a new study, potentially resulting in more intense rainstorms and faster melting of the ice caps.
As global temperatures increase, climate scientists predict there will be an increase in the evaporation of water from the seas and oceans.
This will make the top layer of the sea saltier and add water to the atmosphere in the form of vapour.
This, in turn, will increase rainfall in other parts of the world, diluting some bodies of water to make them even less salty.
This acceleration of the water cycle could have profound impacts on modern society, driving drought and water shortages as well as more intense storms and flooding.
‘The acceleration of the water cycle has implications both at the ocean and on the continent, where storms could become increasingly intense,’ said Estrella Olmedo, the leading author of the study.
‘This higher amount of water circulating in the atmosphere could also explain the increase in rainfall that is being detected in some polar areas, where the fact that it is raining instead of snowing is speeding up the melting.’
Source: Read Full Article