Marsh shorelines of the Massachusetts coast from 2013-14 topographic lidar data

The Massachusetts Office of Coastal Zone Management (CZM) launched the Shoreline Change Project in 1989 to identify erosion-prone areas of the Massachusetts coast. Seventy-six maps were produced in 1997 depicting a statistical analysis of shoreline change on ocean-facing shorelines from the mid-1800s to 1978 using multiple data sources. In 2001, a 1994 shoreline was added. More recently, in cooperation with CZM, the U.S. Geological Survey (USGS) delineated a new shoreline for Massachusetts using color aerial ortho-imagery from 2008 to 2009 and topographic lidar data collected in 2007. This update included a marsh shoreline, which was defined to be the tonal difference between low- and high-marsh seen in ortho-photos. Further cooperation between CZM and the U.S. Geological Survey (USGS) has resulted in another update in 2018, which includes beach shorelines, marsh shorelines and dune parameters, all of which were calculated from 2013-14 topographic lidar data. This metadata file describes the marsh shoreline that is part of the 2018 update. The marsh shoreline was defined to be the steep slope found at the seaward edge of the marsh vegetation. This definition was used because the marsh edge is the preferred shoreline indicator for computing rates of change and making position forecasts.