Planning for more flooding

Climate change is creating more rainfall and higher sea levels. These trends will both contribute to more flooding in our neighborhoods.

The National Oceanic and Atmospheric Administration estimated in 2012 that, on average, worldwide, sea levels will rise between 8 inches and 6.6 feet by 2100 — that’s the 90% confidence interval. Some recent findings suggest that sea levels may rise faster than projected.

Communities along the Charles and Mystic Rivers — Back Bay, Fenway, Allston, Cambridge, Watertown, Belmont — are protected by seawalls at the mouths of those two rivers. The Amelia Earhart dam and the Charles River dam keep river levels down by closing to keep the high tides out and then opening at low tide to allow the rivers to drop. They are equipped with massive pumps capable of driving the full flood flow of the rivers out even at high tide.

Over the last few years, a lot of work has been done by state and local agencies to understand  how the major dams will perform as waters rise higher. The City of Cambridge recently rolled out the results of their very thorough analysis of the question. They concluded that the larger storms (1% chance or “100- year” storms) will start to flank and/or overtop  both dams around the middle of this century, at least in the higher sea-level rise scenarios.  It appears that the dams offer effective protection until at least 2030.

It’s important to understand that even when water gets past the dams the neighborhoods behind the dams will not be completely inundated — sea water will flow over or around the dams at a finite rate of speed and, when the tide goes out will subside, even if the storm continues.

Cambridge’s work suggests that the flood risks associated with increased precipitation are actually greater than the flood risks from sea-level rise (for communities along the rivers).  When heavy rain falls accumulate in the river systems, the waters rise and may peak a day or two after the actual rain event.  Low lying parts of North Cambridge, East Arlington and Belmont may be exposed to flood waters over 3 feet in depth in the 100 year storms by late in the century.  The low-side of Back Bay (close to the river along Beacon Street) and some neighborhoods in Allston are also likely to experience new risks of inundation.

One of the open questions is how sea-level rise risks, which are greatest when high-tides coincide with wind-driven storm surge, will interact with river flooding risks, which are often greatest after the peak of the storm.   Representatives Byron Rushing and Jay Livingstone and I have funded a study by a team led by Ellen Douglas of the University of Massachusetts to draw together the data on these two categories of risk and produce a consolidated mapping of the risks faced in the Charles and Mystic basins.  We expect the results of her work at some point this summer.

Already, as a result of the work that Cambridge, MassDOT and other agencies have done, many are starting to consider the  options for protecting assets — not just buildings, but also power and transportation systems.  Protection can take two forms — keeping water away and improving the ability to quickly recover from flooding (resiliency).  Resiliency can be implemented for individual structures, but holding the water back may require regional investments.

All the early results suggest that we have a couple of decades before the problems really come home, but the lead times are long for major projects.  Understanding the risks and building regional momentum to respond will remain a continuing priority of mine over the years to come.


  1. Status report on UMass study — presentation materials, February 8.
  2. City of Cambridge Climate Vulnerability Assessment.
  3. City of Boston Climate Adaptation Program.
  4. NOAA Sea Level Rise Report.
  5. MassDOT study of climate risks for the Central Artery.
  6. Metro Boston Mayors Climate Coalition.
  7. International Panel on Climate Change.

Published by Will Brownsberger

Will Brownsberger is State Senator from the Second Suffolk and Middlesex District.

31 replies on “Planning for more flooding”

  1. Glad you are working on this. While mitigation is necessary we need to mover faster on prevention starting with a fee on carbon emissions.

  2. Thanks for looking at this locally and regionally. Interesting about the dams. I have not understood why building has been allowed in the 100 yr flood plain (Stop and Shop on Pleasant Street, and I assume the new apartments there). Good goal to look at protection of utilities and prevention. In NYC they are talking about building residences with protections–I think no longer putting power and heat in the basements. Are we? So much development in Watertown already along the river and heavy rains growing stronger and more frequent. And lack of permeable lands for broad drainage. Thank you.

  3. Senator Brownsberger suggests “a couple of decades before the problems really come home.”

    He’s wrong.

    The senator writes only about averages, but the problem is already here, as proven during super-storm Sandy of 2012 in New York City, which cost $75 BILLION and killed 233 people.

    Any similar super-storm during high tide could do even more damage in Boston — ruining most of the subway tracks and city commuter rails, and putting the Turnpike in Boston totally under water.

    That super-storm disaster is already possible right now. It is not a hypothetical possibility from 2 decades into the future.

    1. Thanks, Ned. I agree that a Sandy storm here would do a lot of damage. Don’t mean to minimize that.

      I’m really focused in this piece on the risk to communities protected by the existing sea walls. Manhattan and South Boston face similar risks. Cambridge and Back Bay have a little more protection.

  4. Thanks for the report, Will. I think we could go a long way to reducing runoff in Watertown by growing the urban forest with street trees and increasing pervious pavement and swales and the like. My whole street is asphalt, no tree strip between the road and sidewalk, and maybe a couple small trees on my block. We should be following NYC’s lead (they recently completed their 1 million trees program 2 years early).

  5. Given the thought and planning that has already gone into studying the problem, can we not now come together and admit that the threat is real and that we need to plan and allocate resources now to protect our communities. Places in Europe have already begun this work. We need to follow and the findings of these reports you mention need to be promulgated to the public so that they are seen as real. Enough of arguing about if it is true. Now, what do we do about it?

  6. unfortunately my time has already come! Still no solution. Appreciated your interest however and your concern about the bigger picture!

  7. Flooding is of course only a symptom of the bigger issue of curtailing green house gases and climate change. Preparing wisely for flooding is essential, but it is akin to putting the finger in the dike to give us time to address the bigger issue. Part of the solution to the bigger issue is immediate passage of a robust solar energy bill rather than have our energy policy driven by the utilities. That can be done now, not years from now. The utilities’ proposed legislation undercuts the 15,000 jobs and hundreds of companies that have invested in rooftop and distributed solar energy. Instead of building the clean energy economy of the future, the utilities are investing in more natural gas pipelines and building massive transmission lines. So please support a robust solar bill that will lift the net metering cap, keep net metering buy back rates at retail and the current SREC program and oppose regressive, minimum bills. This is an immediately available and necessary step to curtail aggravated flooding, which is what will result if the utilities get their way.

  8. Will: Thanks for sending the information and the links. If you didn’t see it, today’s (2/8) NY Times describes some of the political hazards in aggressive flood control planned after Sandy in Hoboken, while the December 21 New Yorker carried an article by Elizabeth Kolbert about water levels in South Florida. It might be useful to review some of the Internet criticism of the figures she cited, to address any similar concerns by folks here in Massachusetts.

  9. How will the increased flood risks, as well as the potential for more frequent high wind storms, play out in insurance markets? The availability of affordable wind coverage in the Cape is already quite constrained; it seems likely that some form of this problem will begin to creep further inland.

    Can new forms of risk coverage be developed to make insurance more affordable?

    If we are talking about a problem that will most likely get gradually worse over a period of decades, are there retrofit or control strategies that should begin to be implemented within or around existing structures? A long planning horizon could bring costs down if the changes can be integrated into other retrofit or construction projects. However, some type of regulatory actions may be needed to ensure people focus on the issue.

    What we don’t want is for increased flooding risks to end up being a de facto liability of the state; or for no coverage to exist and people end up having to bear any losses in full.

  10. Will,

    This is very important and I’ll discuss it with Arlington’s soon to be established working group dealing with adapting to this kind of thing. btw, in the 30 years I’ve been working on climate change one thing I’ve almost always heard from the experts is, “It’s happening faster than we expected ” (or predicted).

  11. Well done, Senator! One may not agree with the projected timelines, but your nuanced explanation will do much to raise our communal level of understanding … with the hoped-for result that we all support taking protective as well as resiliency steps BEFORE the occurrence of a Sandy-like flood in the Greater Boston Metropolitan area.

  12. Will, This is an important issue. I am glad you have commissioned this study. My Winn Brook neighborhood is vulner- able. Fortunately my home hasn’t had deep flooding. But I did experience in the mid-nineties, serious flooding on Cross and Lake Streets and Route 2. I am sure that flooding will be worse since so many Sugar Maples have been cut down for the Uplands Housing Project.
    Anne Covino Goldenberg

  13. Even though my home on Stearns Road has not had serious flooding, I did encount er flooding of Cross and lake Steets onto Route 2 in the mid-nineties. Now that all the Sugar Maples have been cut down for the Uplands Housing Project, it will be far worse. And I imagine that my house will also have flooding.
    So I am glad you are proposing a study.

    Anne Covino Goldenberg.

  14. It is very good that you and other legislators are taking this on. After so many years of misinformation by corporate interests unwilling to face their potential loss of income, we now can move forward decisively.

    Although I appreciate the attention to our low lying basin communities, we must be cognizant that our communities are fairly affluent relative to much of the rest of the world and even the country. Solutions that serve only us are not real, long term solutions. I realize that you work at the state and not at the national level, but I would suggest in addition to focusing on mitigating high water risks that we redouble the focus on the emissions problem, joining big city mayors who are already taking the lead.

    1. Amen. We are among the best positioned to deal with this. Folks in low-lying third world countries don’t have the planning and construction resources we have. Agreed that we need to control emissions.

  15. The Alewife T Station is in the area vulnerable to flooding, as are the nearby 40B housing developments. Flooding due to increased rainfall and increased impervious surfaces due to building is already starting to occur and will increase.

    Thank you for taking this issue on. And thanks for the many thoughtful comments.

  16. Thank you for the explanation and for your involvement in addressing the issue.
    It is so important to discredit the climate deniers and to continually call attention to the gravity of the risks posed by climate change.

  17. I am glad that thought is given to the issue. And the Charles river dam explanation. Will, I don’t think you will have to take the water shuttle from Belmont to Beacon hill “island” any time soon, but how about Logan? arrivals and departures be only at low tide? Is there another dig dig like “Masspork” project to put massive sea walls or raise the height of the airport in the works? Maybe we should get out of our planes as well as cars. What about all those tunnels? At what point do we give up on Boston and let nature takes its’ course?

  18. Thank you for pursuing this. Can you add as a research topic some information on how an Allston homeowner like myself might best protect the long-term value of our home? What is the availability of flood insurance, federal or otherwise, and what’s the prospect for its availability as we get closer in time to the crisis point?

  19. I would love to know what the MBTA is doing — or not doing — about all this. A storm surge that puts a couple of feet of water into downtown Boston will probably kill the T. It seems likely there will be damage that will need fixing even after the surge subsides. In the worst case the region will be without the T for days. Is the T thinking about this? If so, how does it see the risks??

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