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City looks at how to protect triple deckers from flooding as sea levels rise

Boston sea-water flood zones

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.

Diagram: Three decker in a flood

Coastal Resilience Solutions (29M PDF).

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Comments

We could just rip up all of the filled wetlands of the Back Bay, Logan, MIT, Bay Village, the Flat of Beacon Hill, and South Bay and restore Boston to when the time when we weren't the virus.

I'm kidding, Sea level rise is happening, and it should be dealt with. There have been some calls to rip down the City garage at West Fourth Street and Frontage Road for a possible stadium for the Revs. Others have said it should be ripped up and the wetlands restored.

Anyone who lives in the areas I mentioned above, other than if you live along Washington Street and about 200 feet on either side of it and you are calling for the "restoration" of the South Bay, start with your own place first. Rip it up and let the cattails grow.

Also, nearly all of the land in Dorchester in the map above is commercial or parkland, save for a few houses in Savin Hill and Port Norfolk as well as Harbor Point. I'd be far more worried about sea flooding if I lived in a basement apartment on Dartmouth Place or Lawrence Street than I would If I lived off of Grampian Way.

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We keep hearing it is a problem with future projections. What is the actual recorded rise in Boston harbor over the past 10-20 years? Are people panicking over iffy models or are there measurements in the harbor to back up concerns?

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1921 to 2019 which is equivalent to a change of 0.94 feet in 100 years.

Sounds like this is slow enough of a problem that retrofitting a foot or two to existing and new seawalls along the harborwalk wouldn't be a problem. Put a property tax surcharge on waterfront properties to pay for construction and maintenance or get Massport to chip in partially for it.

But what do future projections say? Will the rise stay steady at 1 foot per hundred years, or will it speed up?

Add several feet on top of that for the 21st century.

Yeah, I'd like to see dots on the map showing existing triple-deckers. The lowest lying areas of Boston were filled most recently, so I suspect most of the older housing wouldn't be affected by this.

It's too bad this plan bans basement apartments. That's a good way to prevent the expansion of the housing supply. Any such restriction should come along with a plan to make sure new housing is allowed some other way.

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everywhere outside of this zone. The city even has a policy to encourage them, maybe Accessory Dwelling Units?

Are the slides from the presentation publicly available?

My apologies: I had a link at the bottom of my post, but screwed up the HTML and so it didn't show up:

http://www.bostonplans.org/documents/planning/urban-design/2020/presenta... - it's a 28M PDF file, in case you're on mobile.

We are never going to piecemeal harbor protection together in time. The only way to fix Boston from flooding is the outer harbor dam. People love to talk about ecological ramifications of turning Boston Harbor into potanaly fresh water. What about all other dams like the Charles River dam?
Did you know that on a regular high tide Boston Harbor water lever is over 7ft higher than the Charles river level? King tide its 10ft higher. We need to start building it or we are screwed.
http://archive.boston.com/bostonglobe/ideas/articles/2010/06/06/defendin...

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There are many reasons this has been determined to be a Very Bad Idea.

I suggest that you read something more recent than 2010.

For starters, it won't work - see also "topographic maps of the MA coastline".

That doesn't even get into the "oops, not tall enough" aspect of any vast investment in built infrastructure, among many many many other failings.

My suggestion: do like Seattle did 125 years ago: fill in around the buildings.

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It's still easier to fill in the other low points along the shoreline from Quincy to Revere than fill in all around every coastal buildings around Boston Harbor.

You would have to fill in the entire coastline, dear.

To quote myself from 2018:

I've seen you spar on this almost every time it comes up.

You don't need to build a mile-high dam "from Gloucester to the Cape" as you suggest to resist a short-term storm surge of water significantly damaging Boston's urbanized downtown. It doesn't matter if the Fore River swells during a bad storm, because 1) it's surrounded by wetlands that help absorb the water while i.e. the Seaport and Financial District are not, and 2) it's >9 miles from the urban downtown where the damage would be worst, with 9 miles of sparser, more suburban-style housing between there and Shawmut. These proposals are NOT trying to permanently uplift the city into the air to prepare for a Waterworld scenario, they are preventing temporary climate events like Hurricane Sandy from having the same effect on the MBTA that that had on the MTA, as one example. And yes, reinforcing potential "weak spots" in the surrounding topography (such as "elevating roads in low-lying areas by as much as 7 feet") would be part of such a seawall project.

And you KNOW that there are articles written since 2010 - because in reply to you, I posted one from the Boston Globe in 2017!

At their seaside offices at the University of Massachusetts Boston, the professors who are spending the year studying the practicality of a barrier said they’re considering costs, potential environmental damage, effects on commercial shipping and fishing, and possible locations. They will also be looking at how a barrier might affect the ecology of harbor waters and marshes, the potential threat to the quality of its expensively cleaned waters, and the possible side effects of changes to natural currents.

“It’s a very complex project, with all kinds of economic, environmental, and social consequences,” said Paul Kirshen, a civil engineer and professor at the university’s School for the Environment.

I'll have to look up how hard you promoted 2024 Olympics ...

There are many, many reasons that the Commonwealth has rejected your Grand Idea of Pork Construction at multiple levels of proposal: it is expensive, its a joke, and it wouldn't work.

Of course you would be long gone with the profits by the time most people realized the con ... just like happened in Venice.

Indeed, it seems the cheaper option has been decided: localized shoreline resiliency. But... I checked a topographical map, per your suggestion, and... if you're right, wouldn't the water just go AROUND? That's why you were saying a seawall wouldn't work, right?

Is there a link to the flood map? I can't quite see if my workplace is under water or not.

can be found here on a very detailed level: https://msc.fema.gov/portal/home

None of this resiliency stuff matters for individual building because Boston's water and sewer network isn't up to the task during floods. A building with solar power on the roof and units acting as an island above floodwater aren't going to be habitable for very long with access to potable water and a sewer system to get rid of waste.

Hurricane alley has much experience with these issues and as usual Boston in its arrogance can't be bothered to learn from other parts of the country.

The city isn't serious about this issue until it starts doing something about ancient infrastructure. Judging be the number of lead pipes still in the ground Boston isn't doing jack shit.

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Does anyone have a resource or two that shows landscaping options with native plants that might act as said giant sponges?

we are not a culture that accepts limitations well. this watery future may be televised but it won't of itself be that exciting--how Bostonians react to it, now, that is likely to be a gripping drama.

humans are not going to win this one. to adapt, you'll have to flee.

Triple deckers? Are the historic Victorians safe? Shit. There goes Boston history. But I guess it happens. UNLESS......How have we been able to save Back Bay from sinking? It will take the same capital that saved the Beacon Hill and Back Bay brownstones to save the Victorians and triple deckers threatened by rising tides.

Back Bay will sink if the water table *falls*. The wooden pilings under all the buildings need to stay wet to keep from rotting.

Keeping the ground wet is the job of the Boston Groundwater Trust. Problems like leaks into the roof of the Green Line tunnel put the whole neighborhood at risk. They have the big and important job of fixing this stuff.

I'm wondering this as well. What are we supposed to tell all the people who own or rent garden level units, particularly in our older Victorian brownstones and rowhouses? Sorry, your property value is now $0 and you need to move somewhere else?

The City cannot even control lead paint and asbestos abatement on houses that are being renovated. Many a demolition have these materials going right into the dumpster.
Flood control? Lol