Sargent's view: A modest proposal for Plum Island

Bill Sargent photo.Roughly 6,000 cubic yards of sand flow through the south jetty on Plum Island every two weeks from October to March. 

If we work with nature there is a cheap, efficient way to protect the homes on Northern Reservation Terrace. It would be to transport 6,000 cubic yards of sand from the top of the south jetty to the existing berm by truck.

The multi-acre area on the oceanside of the south jetty is what coastal geologists call a sand sink because it consists of sand that has fallen out of the sand cell that transports sand from the center of the island north. There is also a second sand cell that transports sand from the center of the island south.

About every two weeks from October to March, 6,000 cubic yards of sand naturally flows through the jetty and collects along its riverside as a 600-foot-long pristine beach.

Then waves wash this sand around the spur of the jetty and onto North Point Beach. So every year about 30,000 cubic yards of sand ends up on the beach. This is the same amount that the Woods Hole Group calculated flows north every year in the sand cell.

So, since the jetty started settling in 2015 about 150,000 cubic yards of sand have flowed onto the beach, just not in front of the houses on Northern Reservation Terrace where we would want them.

But if we give nature a hand, we can change this. We can skim about a foot of sand off the top of the sand sink and truck it down the existing 69th Street path to build up the dune in front of Northern Reservation Terrace.

Since this is a sacrificial dune, the process might have to be repeated until the beach grows enough to hold its own in a year or two.

We can expect the dunes to eventually grow as much as 400 feet eastward, as they did for almost 40 years after the jetty was disheveled by the 1978 blizzard.

Using this local source of sand would be far cheaper than trucking in incompatible sand from an upland quarry in Maine or dredging it from the river as was done to build the berm in 2018 and 2019.

Any scars left from skimming the sand would be erased within two weeks as the combined height of the tides and waves top 15 feet, which happens during every new, and full moon high tide in the erosion season.

All that we need is for Newburyport and the state Department of Conservation and Recreation to convince the state Department of Environmental Protection, that this is a far more preferable and natural solution than using boulders, upland sand or other artificial solutions to save the eminently protectable houses of Northern Reservation Terrace.

Bill Sargent is a North Shore science writer and contributing columnist. His most recent book, 20,000 Years on the Merrimack River is available in local bookstores and through http://plumislandoutdoors.org, and at www.ingramcontent.com.

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