Clipped from: https://smartwatermagazine.com/news/unsw/extreme-storms-could-help-protect-beaches-sea-level-rise
17/05/2022 UNSW
Images in the wake of violent coastal storms usually focus purely on the extensive damage caused to beaches, dunes, property, and surrounding infrastructure.
However, a new international study has shown that extreme weather events could help protect beaches from the impact of sea level rise – by bringing in new sand from deeper waters or from nearby beaches.
The study, led by Dr Mitchell Harley from UNSW Water Research Laboratory, is published today in Nature Communications Earth & Environment.
“We know that extreme storms cause major coastal erosion and damage to beachfront properties," Dr Harley says.
“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.”
In collaboration with researchers from University of Plymouth and Autonomous University of Baja California, the study examined three coastlines across Australia, the United Kingdom and Mexico. Each was subject to a sequence of an extreme storms or extended storm clusters, followed by a milder period of beach recovery.
In Australia, researchers studied Narrabeen beach in Sydney in the wake of a 2016 storm which famously ripped a swimming pool away from a property overlooking the coastline.
Using high-resolution measurements of the beach and seabed, they were able to show that sediment gains were sufficient to theoretically offset decades of projected shoreline retreat.
“For the first time, we were able to mobilise specialised monitoring equipment to get really accurate measurements before and after a storm,” Dr Harley says.
“We used a combination of a twin engine aeroplane equipped with a Lidar scanner, drones and jet skis going back and forth along the beach taking measurements below the surface right before and after the storm hit.
“This was how we were able to get an accurate picture of the volume of sand moving for each storm.”
In the UK, researchers of the Coastal Processes Research Group of the University of Plymouth have studied Perranporth beach in Cornwall since 2006 using a combination of monthly beach topographic surveys and quasi-annual bathymetric surveys.
Here, the impact of the extreme 2013/14 and 2015/16 winters resulted in very significant losses of sand from the intertidal beach and dune system. However, when looking at the total sand budget, including the underwater part of the beach, it was observed that by 2018 the beach had gained 420,000 cubic metres 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,” says Professor Gerd Masselink, who leads the Coastal Processes Research Group.
極端風暴可以幫助保護海灘免受海平面上升的影響
研究猛烈風暴侵襲海岸過後的圖像時，通常只關注對海灘、沙丘、財產和周圍基礎設施造成的廣泛破壞。然而，一項新的國際研究表明，極端天氣事件可以幫助保護海灘免受海平面上升的影響——通過從更深的水域或附近的海灘引入新的沙子。該研究由新南威爾斯大學水研究實驗室的 Mitchell Harley 博士領導，於今天發表在 Nature Communications Earth & Environment 上。
“我們知道極端風暴會導致嚴重的海岸侵蝕和沿海財產的破壞，”Harley 博士說。
“迄今第一次我們不僅看到了水面上方，那裡很容易看到極端風暴的影響，而且還看到了水下深處。
“我們發現，在這些極端風暴中，數十萬立方米的沙子進入了這些海灘系統——這與工程師用來人工培養海灘的
規模相似。
“這可能足以抵消由氣候變化引起的海平面上升的一些影響，例如海岸線後退，以及長期數十年的影響。
“這是一種看待極端風暴的新觀點。”
該研究與University of Plymouth和Autonomous University of Baja California的研究人員合作，研究了澳大利亞、英國和墨西哥的三個海岸線。每個都經歷了一系列極端風暴或擴展風暴群，隨後是一段較溫和的海灘恢復期。
在澳大利亞，研究人員在 2016 年的一場風暴之後研究了Sydney的Narrabeen海灘，這場風暴將一個游泳池從俯瞰海岸線的花園裡上扯開來。
通過對海灘和海床的高分辨率測量，他們能夠證明沉積物的增加足以在理論上抵消數十年預計的海岸線退縮。
“我們第一次能夠動員專門的監測設備在風暴前後獲得真正準確的測量結果，”Harley 博士說。
“我們使用了配備光學雷達掃描儀的雙引擎飛機、無人機和水上摩托艇的組合，它們在風暴來襲之前和之後沿著海灘來回進行測量。
“這就是我們能夠準確了解每次風暴移動的沙子量的方法。
在英國，Coastal Processes Research Group of the University of Plymouth的研究人員自2006年以來，利用每月海灘地形調查和準年度測深調查相結合的方式研究了Cornwall的 Perranporth 海灘。
在這裡，2013/14 和 2015/16 極端冬季的影響導致潮間帶海灘和沙丘系統的沙子大量流失。然而，在查看包括海灘水下部分在內的沙子進出總量時，據觀測，直到2018年，海灘已經獲得了 420,000 立方米的沙子。
“我們不太確定這些額外的沙子是來自近海還是來附近角落，或者兩者兼而有之，但我們現在確實知道，儘管會導致上海灘和沙丘侵蝕，極端海浪可能會對整體沙子進出總量做出積極貢獻， ”Coastal Processes Research Group的Gerd Masselink 教授說。
重點提示
in the wake of something [phrase] 隨…之後而來 An investigation followed in the wake of the scandal.
dune [noun] 沙丘 Down to the coast where the sand dunes were.
erosion [noun] 侵蝕；腐蝕；磨損 As their roots are strong and penetrating, they prevent erosion.
for the first (second / last) time [phrase] 迄今第一次（第二次/最後一次） For the first time in my career, I was failing.
nourish [verb] 培養；助長；支持 The food she eats nourishes both her and the baby.
rip [verb] 迅速扯開；猛力去除 He ripped away a wire that led to the alarm button.