Climate Ready Charlestown - Phase II

Charlestown's different elevations impact how and how much the area floods. High tides and storm surge can lead to fringe flooding or flooding through flood pathways.

Coastal flooding impacts depend on the size and severity of the storm that causes the flooding. The timing of when that storm arrives along the coast affects flooding impacts. Extreme storms will happen more often in the future. Without actions to reduce risks, the likelihood of coastal flooding from storms and high tides will increase over time due to sea-level rise.

The design flood elevation (DFE) is defined as the minimum elevation required to protect an area from a set level of coastal flooding. Areas that experience greater coastal flood risk require solutions that are designed to a higher DFE. The DFEs are measured relative to a fixed datum called North American Vertical Datum of 1988 (NAVD88). 

The DFE is 15.5 feet NAVD88 for Charlestown. It is important to understand that the elevation of the DFE is not above the ground surface. In most areas along the Charlestown’s waterfront, the lowest-lying locations are currently at approximately 8 to 12 feet (NAVD88). Therefore, coastal resilience solutions need to be designed at 4 to 8 feet above the current ground elevation to reach the DFE of 16 feet (NAVD88) in Charlestown.

The long-term strategy will increase the Harborwalk's height by approximately 4 to 7.5 feet above the existing grade. This strategy includes the connection of the dam to Paul Revere Park and the elevated Harborwalk. 

The Harborwalk's design will incorporate accessible sloped ramps, terraced seating, new park space, gates for waterside access, and other amenities. These will integrate the raised edge with the surrounding landscape.

The preferred long-term strategy for the Navy Yard is to raise the Harborwalk by approximately 5 to 7 feet above the existing grade. To close near-term flood pathways, some sections of the Harborwalk would need to be raised by 2030. These sections include the Harborwalk fronting Charlestown Naval Shipyard Park, at the ends of 13th and 16th Streets, and next to the property at 114 16th Street. This will form a continuous line of coastal flood protection along the waterfront from the Chelsea Street Bridge to the Boston National Historical Park.

Through the 2030s, the Cooperatives of CharlesNewtown next to the south side of Little Mystic Channel may experience fringe flooding during severe storms. To reduce impacts to residents, a 2.5 to 4 feet floodwall can be constructed along the inner edge of the Harborwalk. This floodwall can include new seating, amenities, and general improvements to the Harborwalk and nearby public spaces.

The preferred long-term strategy re-envisions the appearance, function, and use of the Little Mystic Channel. This includes extending the southern and eastern edges of the Channel outward into the water as part of a new elevated park with integrated coastal flood protection. Flood protection should reach approximately 4.5 to 7.5 feet above existing grade.

This coastline extension would provide opportunities to introduce ecological restoration projects. Projects could include constructed wetlands that improve habitat, coastal resilience, and water quality. It also presents opportunities for new community amenities along the Little Mystic.

To minimize the disruption of industries in this study area,  site- and building-scale adaptation measures are appropriate in the near-term. These solutions give business owners flexibility as they integrate resilience into their sites and preserve business continuity. 

In the long-term, some water-dependent uses at the Autoport may need to move elsewhere as sea-level rises. The City recommends Massport to evaluate options that provide perimeter protection of the Autoport.