That shorelines change, oftentimes dramatically in short periods of time, is an accepted fact for those who live along the shore. However, when two-thirds or approximately 512 miles of a state's ocean-facing shore exhibits a long-term erosional trend, in some locations eroding at an average annual rate of 12 feet per year, as is the case in Massachusetts, shoreline property owners, prospective shorefront property owners, and coastal managers need to pay particular attention to the future location of the shoreline to avoid physical and economic disasters.

The Woods Hole Oceanographic Institution, Sea Grant Program, the U.S. Geological Survey, and the Cape Cod Cooperative Extension recently completed an update and statistical analysis of historical shoreline change along approximately 1,000 miles of Massachusetts' ocean-facing shore, of which 754 miles were statistically analyzed (Thieler, O'Connell and Schupp, 2001; Schupp, Thieler & O'Connell, 2001). The project was funded by the Massachusetts Office of Coastal Zone Management. In general, four to five shoreline positions mapped between the mid-1800s to 1994 were used to analyze changes along the Massachusetts shore. Seventy-six shoreline change maps with accompanying data tables and a Technical Report were produced.

The results of this study reveal that approximately two-thirds of the Massachusetts shore is eroding, with 68% of the shore exhibiting a long-term erosional trend, 30% showing long-term accretion, and 2% showing no net change. ln some areas, erosion rates have accelerated based on a comparison study of previous data that was conducted in 1997 (O'Connell, 1997). Ironically, coastal property that commands some of the highest real estate values in the Commonwealth also exhibits the highest consistent long-term average annual erosion rates.

This paper describes the data sources used to map historic shorelines in Massachusetts, the methodology used to both plot a new shoreline and analyze the long-term historical data, and describes cautions necessary when interpreting and applying shoreline change data, with site-specific examples along the Massachusetts shore.