Data Scenarios & Assumptions
The Trustees and the Woods Hole Group, Inc. (WHG) utilized results from the Massachusetts Coast Flood Risk Model (MCFRM) to determine future projected chronic and storm-based flooding. MCFRM includes sea level rise (SLR) associated with the “high” projections as recommended by The Massachusetts Office of Coastal Zone Management (CZM), MassDOT, and the University of Massachusetts and developed specifically for the Commonwealth of Massachusetts by Deconto and Kopp (2017). This :high” scenario of SLR assumes that global greenhouse gas emissions (GHG) continue in a similar fashion as today. By using these projections, the data presented herein are consistent with the Massachusetts coast-wide analysis conducted for MassDOT using the MCFRM, which was developed to encompass all risk levels and assess critical infrastructure.
The actual elevations (in NAVD88) used to represent these SLR values vary slightly from town-to-town, and can be found below:
Impact to buildings and roads from storm flooding were determined using results from the MCFRM developed by Woods Hole Group. MCFRM considers the probability of severe coastal storms and evaluates impacts of those events in terms of coastal inundation. The storm effects consider assumed sea levels in the future given the SLR projections.
Marsh and coastal habitat changes were derived from the Sea Level Affecting Marshes Model (SLAMM) results developed for CZM by Woods Hole Group.
The SLAMM results were also developed with SLR projections that assumed the global GHG emissions continue at the current rate; however, this was completed with older SLR projections (~2015) representative of a high rate of SLR at the time, but is more comparable to a intermediate-high scenario under the more recent projections of Deconto and Kopp (2017). Current marsh accretion rates were determined by applying the Marsh Equilibrium Model (Morris, 2015) applied at the Great Marsh System for the north shore areas.
More information on potential marsh accretion rates can be found below:
Beach erosion rates were derived from the DRAFT Massachusetts Coastal Erosion Viewer.