December 19, 2014
“Academic politics are so vicious, precisely because so little is at stake.”
August 8, 1977
December was 19th was a bitterly cold day with no wind and low dark clouds. The remains of a sandy track hung six feet above the beach surrounded by huge tangles of snow fencing. Only a few months ago, huge flatbed trucks had lumbered along this road covered with steel plates, like the ones General Patton might have used to drive his tanks through the boggy swamps of Northern Italy. Each truck had dumped half a dozen 5-ton boulders on the beach where brightly colored yellow excavators had picked them up and deftly placed on the jetty, last repaired in 1970.
Plum Island homeowners were thrilled. They were sure that this $12 Million dollar outlay of public funds was going to solve their erosion problems, almost two miles away.
But it was clear that something had gone terribly wrong. Waves were scouring sand off the end of North Point and the dunes were eroding back thirty to fifty feet every month. During storms they could break through the dune line and run as far as 150 feet into the dunes. They were stopping only 300 feet from over 80 homes on Northern Reserve Terrace, most of them worth over a million dollars. At this rate, the ocean would be lapping at the houses’ foundations in 2016 and they would be in imminent danger by 2017.
The homeowners were victims of a common misperception. Local knowledge had it that a powerful current flowed out of the mouth of the Merrimack River carrying sediment that had built up a sandbar that focused erosion on Annapolis Way over a mile away.
If this had been the case, the Merrimack would have had to been as strong as the Mississippi River. Plus, the sandbar was also thought to grow in a cyclical pattern that focused erosion on different parts of the beach in a repeatable manner. Unfortunately this was all a convenient myth.
But how had this myth come about? If you look at charts from the 1800’s you can see arrows showing that currents flow from the center of the island north and from the center of the island south. Geologists call these longshore currents because they flowed parallel to the shore constantly moving sand up and down the beach. 19th century Newburyport fishermen knew these currents well because they had to row against them to reach their fishing grounds.
But back in the 1960’s erosion had also become a problem, sometimes washing away as many as half a dozen homes in a single storm. Locals had brought in The Army Corps of Engineers who had hired Duncan Fitzgerald to investigate. He gave the problem to a graduate student who had used an old fashioned wind rose to show that winds blowing out of the Northeast set up currents that flowed south along this part of Plum Island.
This was before oceanographers had emplaced an extensive array of offshore wave buoys along this coast. Now meteorologists know that in the beginning of a Northeaster, short period waves do approach from the Northeast, but as the storm develops it creates larger longer period waves that approach the beach directly from the East. There might be a few shorter period waves skidding along on top of the long period waves but the major swell will hit the shore directly from the East.
This happens because waves grow deeper as well as higher the longer they travel over the ocean. So when northeast waves near the coast their northern end hits the ocean bottom first and friction causes them to swing around so they end up attacking the shore straight on from the East.
But based on the false assumption that the longshore currents flowed south instead of north the Corps had gone ahead and repaired the jetty. And as we have seen, by 1973 they realized they had made a mistake so they had brought in Dennis Hubbard, who discovered that 90% of the time the longshore currents flowed north. And it was only when waves were over 8 feet high during major Northeast storms that sand from Salisbury Beach could skirt around the mouth of the Merrimack River sometimes getting as far south as Annapolis Way.
This meant that that during 90% of the time the repaired jetty was acting like a giant dam holding sand back from building North Point. The problem was, Duncan Fitzgerald’s analysis was simple and Dennis Hubbard’s was complicated. After all, most rivers ran north to south and water ran downhill, right?
So Newburyport’s mayor, Byron Matthews glommed onto the simpler concept followed by all the other local town and city officials. It was just plain easier to remember that all the currents flowed south than that those on the north flowed north and those on the south flowed south.
But academic politics also played a part. Dennis Hubbard was a lowly graduate student at publically funded U-Mass when he wrote the paper while Duncan Fitzgerald had been a full professor at privately funded Boston University. Then, after he finished his thesis Dennis had moved on to get his PhD at the University of South Carolina and become head of the geology department at Oberlin College.
However, Duncan Fitzgerald had stayed on at BU where he became a well known professor famous for telling his “joke of the day,” at the start of his class on beaches and dunes. He also become known as te reigning expert on all things Plum Island.
He also continued to do most of his research for the Parker River Wildlife Refuge that owned the southern end of the island where the currents flowed unequivocally south, so there was little incentive for him to redo his research on the north end of the island. And because it was considered Fitzgerald’s bailiwick nobody would redo the research again. Even if money was available, which it wasn’t.
So there it was, local misperception backed by out of date research had all fed into the convenient myth that if you just had enough money to build groins, jetties and seawalls you could beat the Atlantic Ocean into submission and stop erosion in its tracks!
Dr. Hubbard will be presenting the Storm Surge lecture at the parker River Wildlife Refuge on October 21st at 7pm.