Climate Ready East Boston - Phase II

East Boston'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 16.0 feet NAVD88 for East Boston. It is important to understand that the elevation of the DFE is not above the ground surface. In most areas along the East Boston 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 East Boston.

The proposed near-term approach would raise a part of the Bennington Street right-of-way to form a line of coastal flood protection between the Belle Isle Marsh and upland areas. A 2.5- to 3-foot flood wall on the shoulder of the roadway provides additional flood protection and has the benefit of sheltering pedestrians and cyclists from the flow of traffic. Bennington Street is a designated evacuation route; this strategy helps maintain a dry route for emergency responders and evacuation on Bennington Street. 

There is also potential for a sloped berm, living levee, or pile-supported walkway along the marsh next to the raised Bennington Street. This strategy would provide a multi-use path for pedestrians and cyclists with views of the marsh. The berm could extend from the raised roadway into the marsh with a gradual slope, softening the edge between marsh and upland urban areas. It would also provide slope for certain types of marsh habitat (high marsh) to migrate upland over time with sea-level rise.

The preferred near-term option includes a passive flood wall and multi-use pathway within an underutilized rail right-of-way between Route 1A and Chelsea Creek. The floodwall would reach 2 to 4 feet above the existing grade along the water’s edge. The design of the wall could connect with a new multi-use pathway to provide new public access along the shoreline.

The preferred strategy is to construct a landscaped berm at the water’s edge to protect against long-term flood risks. The berm would stretch approximately 2,800 feet long and would be raised to approximately 5 to 7.5 feet above the existing grade. This approach would also create a new waterfront open space with community amenities along Chelsea Creek and advance ecological restoration of the currently degraded wetlands.

On the western end of the park, the preferred option is to construct a raised berm along the shoreline. The berm would be between open water and upland residences connecting to the Wood Island Bay Edge Park. It would be 3-4 feet above existing grade and the height can be adapted overtime to protect against more severe storms and increased sea-level rise. This option connects to the long-term strategy for Constitution Beach of public access and ecological adaptation along the shoreline. 

The preferred strategy combines coastal flood protection with efforts to preserve and enhance public amenities, community benefits, and wildlife habitat at Constitution Beach. The strategy includes an elevated system of constructed dunes, berms, and open space enhancements. The coastal resilience approach would be approximately 5-7 feet above the existing grade. 

On the eastern end of Constitution Beach, the elevated dune system would tie into a berm and floodwall. The floodwall must extend along Bayswater Street to the Orient Heights Yacht Club. An optional low floodwall can extend along Bayswater Street to Shawsheen Road to reduce flooding on Bayswater Street during extreme storms.

In the near-term, the recommended strategy includes a perimeter flood wall around the north side of the rail yard. The near-term design height would be 3 to 5 feet above existing grade. 

In the long-term, the flood wall should be around the full perimeter of the rail yard, forming a line of coastal flood protection. The wall would extend 5 to 7 feet above the existing grade.

The floodwall strategy effectively reduces flood risk while limiting disruptions to rail yard operations and encroachment in the Belle Isle Marsh. The solution could potentially be combined with options for new public access around the rail yard or with wetland resilience approaches for the Belle Isle Marsh.

The strategy would construct a new bulkhead and flood wall in combination with a new elevated multi-use Harborwalk along the Condor Street right-of-way. This public access pathway can serve as an extension of and connection to the Condor Street Urban Wild. The floodwall should reach 4-5 feet above the existing elevation.

In the long-term, the design could be combined with ecological restoration in wetland areas within Chelsea Creek to improve habitat and provide more coastal resilience benefits.

In addition, the City recommends building- and site-scale adaptation approaches for water-dependent uses along Chelsea Creek. Building- and site-scale approaches can tailor to each property owner or business’s specific operational and design criteria, based upon site-scale risk assessments.

The proposed coastal resilience strategy for this location includes a raised berm on the existing upland area along Wood Island. This area is vulnerable to flooding during storms. The raised berm should be approximately 5-6 feet above the existing grade. Due to security and safety concerns related to the airport, public access is not recommended along portions of this berm. However, the berm could include opportunities for design improvements and enhanced public access along the Greenway Connector.

This raised berm strategy can combine with ecological adaptation approaches in Wood Island Marsh. Ecological adaptation can improve habitats for wildlife, promote the adaptation to sea-level rise, and provide mitigation for waves and erosion.