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Dynamic Coastal Systems: Wasque as a Model

The ever-changing locations of Norton Point and the Chappy spit. Four months worth of movement in early 2012 is drawn in over an aerial image taken in May 2010. Graphic created by Woody Filley (click to enlarge)

by Terry Appenzellar

Currents ... tides...waves...storms... surge... shoaling sands... it remains somewhat of a mystery exactly what is driving the openings and closings of the inlet at Norton barrier beach and the frequency and magnitude of changes at Wasque on Chappaquiddick. But it is not for lack of caring local observers, or for that matter, of a dedicated team of scientists who are currently documenting the comings and goings of water and sand at this iconic Vineyard location. And, apparently, the answers are of national importance to our Department of Defense! We Vineyarders are blessed that the Office of Naval Research thinks Wasque might be a model for other dynamic coastal systems; they are funding a team of research scientists at Woods Hole Oceanographic Institution to prepare long-term data studies of this complex system.

All of this intriguing information was presented Thursday, June 20th at a conference cosponsored by Massachusetts Office of Coastal Zone Management, Cape Cod Cooperative Extension, and Woods Hole Sea Grant. A full conference room at the Harbor View Hotel listened and learned as a variety of speakers presented interesting graphics and amazing photographs, including satellite images of the opening over the last decade and maps documenting the changes going back several hundred years.

Graham Giese of the Provincetown Center for Coastal Studies presented data and lessons from the inlet opening at Chatham’s Nauset Beach and Monomoy Island. A major theme of his presentation was the importance of continuous data collection so that models can be updated regularly.

Britt Raubenheimer and Steve Elgar from WHOI have an ongoing data collection effort measuring the impact of multiple variables – including wave action, comparisons of Vineyard Sound vs. Atlantic Ocean tides, and impact of weather events (e.g. Irene, Sandy and Nemo) – on the relative size and geometry of the opening over time.

Rocky Geyer and Peter Traykovski addressed shoaling, explaining the asymmetry of ebb and flood tides with big elevation differences and noting that, additionally, Wasque is at the edge of the Gulf of Maine’s zone of distinctly different tidal phases. Slowly these scientists are building and testing models that will lead to conclusions about the causes of the openings and closings.

In the meantime, our local observers shared anecdotal evidence that often supported the scientific observations. Chris Seidel of the Martha’s Vineyard Commission put some hard numbers to what we have all witnessed – the retreat of our shoreline. Her GPS-based readings were striking; in at least one location the shoreline had retreated 155 feet in the last year! Bob Gilkes, Ferry Captain and Safe Harbor consultant, shared his album of photos documenting the washing away of our favorite Wasque land marks: Swan Pond, the boardwalk and staircase down to the beach, and the sand dunes and trees that lined beach cliffs.

Others contributed to the big picture of erosional change by detailing specific impacts. Russell Hopping of the Trustees of Reservations explained how sand overwash and accretion of beaches affects the nesting habits of protected shorebirds. Charlie Blair, Edgartown Harbormaster, recounted events in Katama Bay, including Hurricane Bob and extreme currents, and their economic impacts on the town and its harbor. Paul Bagnall, Edgartown Shellfish Constable, noted the extreme changes in quantity, type and quality of shellfish stores due by changes to the inlet: openings causing “carpet cleaning” of the bay bottom, while closings led to setting of greater seed quantities.

More uncertain is what can be done in the face of extreme coastal erosion. One significant intervention in response to the erosion at Wasque was described by W. Sterling Wall and Peter Rosen, who presented the analysis, engineering and implementation of the moving of the Shifter house, which was in imminent danger of destruction due to its location on top of an eroding bank. An even broader, yet perhaps more significant question is to what extent we should attempt to combat extreme, yet historically natural, erosion. David Foster, Harvard Forest Director and Polly Hill Arboretum board member, gave us historical topographic maps of openings surveyed by Henry Whiting as far back as 1845. His conclusion is that we should not be surprised by current events because of the large amount of evidence of periodic openings and related erosion.

While patterns are emerging, definitive causes are not yet fully proven as to the dynamics at Wasque and Norton barrier beach. We are indeed lucky to have the WHOI scientific team continue to study and model their findings. For most attendees, one conclusion was obvious: as articulated by Chris Kennedy (TTOR Superintendant at Wasque), human interference in trying to manage these natural processes is not likely to prevent the inevitable evolution of this amazing location. The costs do not seem justifiable; it is better to endure the changes, observe and learn from them.