How Waves Work in Creating Beaches

Photo credit: Fishers Island Photography

The Fishers Island Photography Instagram account recently posted this and we wanted to share it here

On Instagram: fishersislandphotography

December 2021

Took this photo on Isabella Beach a while back and am only just revisiting it now. It’s interesting to me how the wave-washed sand is so clearly delineated — so, I did a little digging and came across an essay entitled, “Disappearing beaches: drying in the tide,” by a Dr. J. Flor Anthony, which yielded some interesting insight into how a beach perpetuates itself (or doesn’t, as the case may be).

Dr. Anthony writes, “most beaches are now polluted by mud. Mud comes from the land. It washes down the rivers and ends up in the sea, where it remains close to the shore. A clean beach is easily polluted because the clean sand acts like blotting paper to ink. It absorbs the fine particles readily. Only after repeated rinsing by waves, will the fine particles be dislodged and transported towards deeper areas in the sea. This may take weeks to years.“

“Not all waves contribute to the accretion of the beach. Depending on how strong the water’s backwash is, sand will be eroded or deposited. When a wave breaks and spills, it ends up running up to the beach. If the water’s velocity is sufficient to dislodge sand, it will be transported higher up, against the force of gravity. As the water slows down, the sand settles out. Now the water starts its backwash, accelerating as it moves down the beach. At some point it starts dislodging the sand, moving it back to sea. On an unpolluted beach, the water soaks easily into the sand, which reduces the wave’s speed (both forward and backward), resulting in more sand being deposited, higher up the beach where it dries best. Clean and healthy beaches are characterized by a steep slope and a shoulder at the top of the beach, where the most recent sand was deposited.”

For anyone who would like to read more (there’s some interesting info on how dunes are made and how a beach’s ability to dry is critical to their formation/maintenance), check out the full essay here: https://tinyurl.com/beach-dry

#howwaveswork #beachhealth #FishersIsland #FishersIslandNY #FINYphoto #FINY #06390 #finyinfo06390

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