Posted by: coastlinesproject | November 27, 2015

Plum Island erosion.

Saving Northern Reservation Terrace


The Merrimack River Beach Alliance is a remarkable organization, chaired by the able politician Bruce Tarr. Every month or so; town, state and federal officials sit around the same table and decide what to do about Plum Island. And a few months later they line up the funds and permits to make the projects happen.


Anyone who reads these articles on a regular basis knows that I don’t always agree with the projects because most of them have actually increased erosion by throwing the beach out of equilibrium.


But I have always been impressed with Senator Tarr’s ability to get the projects done. However, now, we will need all his powers of persuasion and tact to reverse the erosion that is rapidly tearing away the dunes in front of Northern Reservation Terrace.


As is often the case in organizations like the MRBA, the most important conversations usually occur after the official meeting is over. I joined one of these conversations after the November 20th meeting.


A well-known environmental scientist was using his tablet and aerial photos to explain to Senator Tarr that repairing the South Jetty has created the rapid erosion advancing toward Northern Reservation Terrace, and that moving one or two of the boulders would actually reverse the erosion and put the system back into equilibrium.


Such a conversation never would have happened a year ago. But it is now clear that at the present rate of erosion, up to 80 houses on the Terrace could be in imminent danger by 2017. Such emergencies tend to convince people to consider doing things they would have never contemplated doing before.


A local businessman has offered to dredge sand from in front of his rapidly shoaling dock and use it to construct a sacrificial sand dune in front of Northern Reservation Terrace. This would provide temporary relief and some sense of security, but it will only treat the symptoms, not the problem.


To treat the underlying cause of this erosion, the Army Corps of Engineers will have to move one or two boulders so sand can flow through the landward side of the jetty to return the system back into equilibrium.


Naysayers will say that after the Corps has just spent $12 Million to repair the jetty, they will never agree to now remove some boulders. But they are precedents for doing just that. There are numerous examples of the Corps using gaps and spurs to correct problems caused by their jetties.


The Corps knows from its own experience that this solution will work on the Merrimack River. In the 1970’s they repaired the South Jetty and it also caused runaway erosion in the Northern Reservation Terrace area. So they hired Dennis Hubbard to write a paper that explained why the erosion was occurring as well as implying that the way to reverse the erosion was to alter the landward side of the jetty.


But nature saved Congress and Newburyport a lot of time and money. Erosion and The Blizzard of 1978 undermined precisely the right rocks so that sand could flow through the jetty, eventually creating almost 400 feet of well vegetated sand dunes in front of Northern Reservation Terrace. The hand of man can do the same thing now. The Corps would simply be helping nature nudge the system back into equilibrium.


But everyone would have to admit that some of their most dearly held assumptions are wrong. But extraordinary times call for extraordinary actions. I believe we can undertake them and save the northern end of our island.


(People who are interested in hearing Dennis Hubbard’s recent Storm Surge lecture may view it on the Storm Surge website.)




William Sargent is the author of 20 books on science and the environment. His latest book, Plum Island; 4,000 Years on a Barrier Beach is available in local bookstores and through and at







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