As I See It

 Bill Sargent, The Daily News of Newburyport, Edition 1/18/2018

“Dec. 6 was a warm, sunny day with little wind, so I drove to the end of North Point to see the 10-foot-high king tide. Long period waves were riding in on top of the wing bar and breaking over the 3-foot-high berm of sand that protects the dunes. ”

“But the center of this section of the beach was a different story. I walked to the top of the highest dune and stared down at waves that were undermining the toe of the dune 30 feet below. It was a vertiginous experience.”

“Each wave was tearing away the toe of the bank, creating an avalanche of sand that inched up the vertical face of the sandy cliff. The only thing that was holding the dune together was the matrix of dune grassroots just below my feet.”

“I withdrew gingerly and continued to where I had first seen a rusty barrel jutting out of the dune several weeks before. Last night’s high tide had finally dislodged the barrel and it looked like a pair of city workers had dragged it off the beach. The barrel must have been buried when the Coast Guard built up this dune to slow erosion the last time the south jetty was repaired, in 1969.”

“But it didn’t look good. Two more feet of sand had collapsed off the top of the dune in just the last few days, and the back of the dune descended rapidly to a fence that surrounded the Coast Guard’s camera tower that allows the Coasties to monitor the bars in the mouth of the river. When such critical federal infrastructure starts to wash away, you can expect to see some action.”

“Last night’s waves had also overtopped the rest of the beach and undermined the remains of the old Coast Guard station on the other end of the beach. The nearest house was now only 106 feet from the ocean.”

“Unless the state rebuilt the sacrificial dune that slowed erosion so effectively last year, this house and about 20 others would be flooded during the coming winter. But interestingly enough, it seemed like the reason this end of the beach was not eroding quite as fast as before was that more sand was getting through the jetty. I would have to keep an eye on the situation as the winter progressed.”

“On Dec. 19, I returned to the high dune to see how much it had eroded during the last 10 days. The dune had retreated three more feet but the dune itself was two feet lower because the top of the dune comes to such a steep crest.”

“It was sad to see the great dune washing away but at the same time, I felt privileged to witness such rapid change. An alpine geologist would have to wait several thousand years to see this much erosion and if he happened to be looking at the wrong mountain, it could have grown rather than shrunk.”

“But then, I saw something I had never seen before. The base of the cliff had alternate strata of markedly coarse and fine-grained sands. I had seen hundreds of examples of such bedding in dunes before, the sand grains might have strikingly different colors but they were always close to the same size. Here, the grains were almost an eighth of an inch in one stratum while those in the next were so small I could hardly discern the individual grains.”

“It turns out the reason I had never seen such bedding is that I had never observed dunes made by rivers before. The Merrimack makes a wide curve just before it enters the Atlantic Ocean. The water travels faster on the wide side of this curve so it carves away sand on the Salisbury side of the river and deposits sand on the Plum Island side where the river’s flow is slower.”

“The deposited sand formed a long wing or point bar that jutted into the river. The strata in these point bars and along the side of the river had been put down by a series of floods and quiet flows. The floods had deposited the large coarse-grained sand while the quiet periods had deposited the finer muds and silts.”

“So what I had seen was probably the stump of a wing bar that used to jut out from the beach and the same thing is happening today. The danger is that if too much sand clogs the mouth of the river, it could cut through Salisbury Beach, leaving the jetties guarding a river that is no longer there.”

“This was how the river jumped half a mile in the 1800s. Perhaps, it was then that this fascinating bedding was first deposited along this short stretch of beach.”

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