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New Shoreline Change Data Reveal Massachusetts is Eroding
March 2003

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Approximately 75 percent of the U.S. ocean shoreline is eroding. Massachusetts' ocean-facing shore is no exception. A recent study of shoreline change in Massachusetts by the U.S. Geological Survey, Woods Hole Oceanographic Institution Sea Grant Program, and Cape Cod Cooperative Extension reveals that approximately 68 percent, or 513 miles, of Massachusetts' ocean-facing shore exhibits a long-term erosional trend, 30 percent, or 226 miles, shows long-term accretion, and two percent, or 15 miles, shows no net change. Funding for the study was provided by the Massachusetts Office of Coastal Zone Management.

Photo caption (Figure 1, above): Codfish Park area along the eastern shore of Nantucket. Photo courtesy of Jim Mahala, MA DEP.

Updating Massachusetts Shoreline Change Data

Prior to the completion of this project, the most recently plotted Massachusetts shoreline for shoreline change analysis purposes was 1978. Since that time, there have been several high profile storms, including 1991's Hurricane Bob (August) and The 'Perfect Storm' (October), and the December 1992 nor'easter (all presidential disaster declarations), and many moderate coastal storms that made landfall along the Massachusetts shore. These storms have rendered any prior shoreline change data anaylsis obsolete.

The updated shoreline change project, completed in 2001, involved digitizing a new shoreline from digital color orthophotographs along approximately 800 miles of Massachusetts' shore. This new 1994 shoreline was added to an existing database that included up to four historic shorelines dating back to the mid-1800s. The data now span a maximum of 152 years.

Transects were drawn across all of the historic shorelines on an approximate lot-by-lot basis (every 40 meters or 128 feet), for a total of 30,354 transects. The distance between each of the five historic shorelines was measured at each transect and rates of shoreline change were calculated for each separate time interval, along with the overall long-term average annual shoreline change rate.

All of the historic shorelines were color-coded, overlaid, and printed on the color orthophotographs, along with the long-term average annual shoreline change rate for each transect. As a result, individual building locations, roads, jetties and other recognizable features can be easily identified.

Shoreline Change Data Results

For the most part, the Massachusetts shore is eroding. For the entire ocean-facing Massachusetts shore, the long-term average annual shoreline change rate ranges between -0.58 and -0.75 feet per year.

Approximately 46 percent of the Massachusetts shore is eroding at one foot or less per year, while 22 percent of the shore is accreting at one foot or less per year. Eighty-one percent of the shore fluctuates +/-2 feet per year. Based on other studies (Pilkey & Thieler, 1992), 75 percent of the U.S. ocean shore is eroding, with the U.S. East Coast eroding at an average rate of 2-3 feet per year (Leatherman, 1993). Thus, Massachusetts' average annual shoreline change rate is lower than the East Coast average. That statistic is of little comfort for shorefront property owners in the Commonwealth, where rates of shoreline change vary considerably along the shore with some areas eroding between 7-10 feet per year (Figure 1, above), and higher.

Long-term rates of shoreline change calculated for each of the 15 Cape Cod communities and the islands of Martha's Vineyard and Nantucket reflect this shoreline change variability (Figure 2, below). It is important to note that rates also vary considerably within communities.

Figure 2: Long-term average annual shoreline change rates, by town, for Cape Cod, Martha's Vineyard, and Nantucket, Massachusetts.
Credit: Jim O'Connell, WHOI Sea Grant/CCCE