Boston areas that could see sea water in the streets in coming decades.
City officials are looking at a possible zoning overlay that would require homeowners looking at extensive renovations consider how to deal with seawater flooding that will come as sea levels continue to rise and storms intensify, and they've developed some possible guidelines for retrofitting those most Boston of dwelling units: Triple deckers.
In recent years, the city has required developers in certain areas that face potential widespread flooding in coming years to show what they're doing to make their buildings more "resilient" to flooding, for example, by putting their building's first floor above the anticipated top of flooding, placing their building's electrical and mechanical systems on upper floors and installing landscaping that could double as giant sponges during floods.
In a presentation to the Boston Civic Design Commission last week, Chris Busch, the BPDA's assistant deputy director for climate change and environmental planning, discussed creation of a zoning overlay that would impact both new development and existing homes and residential buildings whose owners need city permission for improvements.
The presentation talks about measures that would apply to various types of buildings, but zeroes in on triple deckers, a mainstay of the city's housing stock, especially in areas that could be hard hit by flooding as sea levels rise and storms intensify: East Boston, Charlestown, South Boston and Dorchester.
A couple of slides in his presentation focus specifically on this sort of housing. What homeowners could do, especially if given a nudge through a zoning regulation and city recommendations, would be to start with a recognition that they can't hold back the tides and to retrofit their buildings to survive periodic flooding:
Abandon the basement as living space and fill it to the current grade with material that would be resistant to "wicking," or drawing moisture from flooding to upper floors, actually raising the rest of the building roughly four feet above the level of flooding the city has designated for the building's lot as sea levels rise, and moving water, heating and other key systems above what the city says would be the flooding level in a big storm.
Also, owners could use below-surface materials that are resistant to salt water and install basement vents that would actually allow water to enter the basement during a flood - to equalize the pressure between outside and inside and keep flooding outside from collapsing walls.
Although the recommendations focus on triple deckers, the presentation adds many of the recommendations would apply to other types of residential buildings in the affected areas.
From the presentation. The blue line represents a future with floodwaters. Some of the pink proposals related to climate change more generally, such as installation of solar panels and more efficient heating and AC systems.
Coastal Resilience Solutions (29M PDF).