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Profiling the Shoreline to Measure Change

Chatham, Massachusetts, is known for its dynamic coastline, often bearing the brunt of nor'easters and hurricanes when they hit Cape Cod. But how does Chatham's shoreline respond to storms and seasonal variability? Are Chatham's beaches resilient or are they losing ground?

To find out, residents Jane Harris and George Olmsted, with the help of Chatham's director of coastal resources, Ted Keon, coordinate a group of 24 volunteers who are participating in a Beach Watch program to map Chatham's shoreline. Their work will offer a series of snapshots of the Chatham coastline that may help reveal trends associated with storm events and seasonal changes.

The Beach Watchers, under technical guidance of Jim O'Connell, a coastal geologist for Woods Hole Sea Grant and Cape Cod Cooperative Extension, use a technique known as Emery Rod profiling to take a series of measurements along a slice of beach. Emery Rods, named for K.O. Emery, a former Woods Hole geologist, are simple to make and easy to use.

"We equipped each group of three volunteers with a kit," explains Harris. "Inside was a compass, wing nuts, four wooden sticks, and a laminated map of the shoreline." Supplies for each Emery Rod setup cost roughly $25.

In about three minutes, volunteers can assemble the 5-foot rods into a flexible parallelogram. Within an hour, they can use the device to take a series of elevation readings that will form a picture of the beach contour from the back dune to the water's edge.

Harris recalls that the first day of sampling in March 2002 "was cold, wet and windy, but we all had a great time. We visited eight stations and covered four different beaches." In Chatham, beach mapping is seasonal: once in late February or early March and once in mid-August as well as pre- and post-storm. Harris takes additional monthly readings at one station on Chatham's Hardings Beach West.

Chatham's beaches, like all shorelines, are constantly moving in response to winds, waves, tides, sediment supply, changes in relative sea level rise, and human activity.

Erosion, a hot topic in many coastal communities, is a natural shoreline process. In Massachusetts, the average erosion rate statewide ranges from .58 to .75 feet per year but fluctuates considerably along the shore. With one-third of the Commonwealth's six million residents living on or near the coast, erosion becomes a concern when people and structures are in danger. The beach profiles collected by residents like Harris and Olmsted can be useful tools to help communities manage their beaches for the future.