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Geology Talk, Geology, Sand Processing, Recycling

Articles from RECYCLING (263 Articles), SAND PROCESSING EQUIPMENT (172 Articles), SLUDGE DEWATERING (87 Articles)











In beach replenishment, a dredge off-shore will normally pump a water sand slurry through large pipes onto the beach.
In beach replenishment, a dredge off-shore will normally pump a water sand slurry through large pipes onto the beach.

Where the sand meets the sea

Natural sand is a diminishing resource around the world, but still in enormous demand. The dwindling of sand supplies is most noticeable on beaches worldwide. Bill Langer discusses how onshore sand quarries may in the future provide some salvation for preserving and rehabilitating our shrinking coastlines.

Sand has many environmental uses, but here is one that doesn’t usually come to mind.

When I was a kid my family spent summers, and some holidays, at the Jersey shore.

In early March 1962, a nor’easterly, called the Ash Wednesday Storm, laid waste to New Jersey resort towns from Bay Head to Cape May. We went to the shore the following spring.

The Army Corps of Engineers had begun an emergency beach replenishment project to restore damage on the storm-ravaged coast.

"Beach replenishment is the subject of serious debate in many coastal areas around the world,"

I remember walking on the beach with my dad. I was 17. There was a dredge offshore pumping a water sand slurry through large pipes onto the beach. As the water drained off, heavy equipment moved and shaped the sand into dunes and a new beach. We were witnessing a tiny part of that massive restoration project.

My dad said: “Time will tell.”

He told me wave after wave slowly but surely eats away at the beach, and it was only a matter of time until another event like the Ash Wednesday Storm would come along. (Hurricanes Sandy and, most recently, Harvey and Irma come to mind.) He predicted we would see more and more dredges spewing sand on the beaches.

Beach replenishment, or beach nourishment as it is called today, is the subject of serious debate in many coastal areas around the world, not just the Jersey shore.

Many people question if beach nourishment is economically sustainable, environmentally conscious and sound engineering practice.

However, other viable methods of beach protection are not apparent and it is unlikely that multimillion-dollar homes and billions of tourist dollars will be allowed to be washed away into the ocean.

Therefore, general opinion seems to be that, although beach nourishment may not be an ideal solution, it is the best solution we have at hand.

Once the water drains off, heavy equipment moves and shapes the sand into dunes and a new beach.
Once the water drains off, heavy equipment moves and shapes the sand into dunes and a new beach.

Most beach nourishment projects have 50-year life cycles. Furthermore, it is likely that flooding and beach erosion will worsen due to rising sea levels and increased intensity of storms associated with climate change. Unless there is a drastic change in the approach to beach protection, massive amounts of sand will be required to maintain beaches during “normal” years and for restoration after major storms.

Right now most of the sand is obtained from the continental shelf, a gently sloping, nearly flat plain that extends offshore about 130 to 145 kilometres, where it is about 90 metres deep. Beyond that is the continental slope and the ocean floor.

There are mounds and ridges of sand on the continental shelf that are remnants of barrier islands that existed during the Ice Age, when the sea level was lower. These features are prime targets for beach nourishment. They are also home to large schools of fish and other sea life, and fishermen are concerned over their use for beach nourishment. That, coupled with isolated sand shortages, creates pressure to look elsewhere for sand.

Take, for example, a beach near Miami, Florida. They are running out of offshore sand for beach nourishment, so sand is being trucked to the beach from an onshore sand operation about 160km away. Ironically, the sand comes from a deposit that was a beach in the geologic past, when the sea was higher than today.

My dad had it right about seeing more dredges in his and my lifetimes. But some day in the future my grandkids or their grandkids may see dredges being replaced by fleets of trucks hauling sand to the beach from onshore sources. Time will tell.











ABOUT THE AUTHOR
Bill Langer
Independent Research Geologist

Bill Langer is a freelance writer and retired Senior Research Geologist for the U.S. Geological Survey. Bill is now an independent researcher specialising in aggregate resources. Click here to email Bill or visit his website.
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Wednesday, 18 September, 2019 9:02am
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