Preparing for storm surge

The risk of enhanced storm surge due to sea level rise is an issue that I am taking seriously as a state senator representing low-lying areas in the Charles and Mystic watersheds.  I’ve been talking with a lot of people in the region about how to develop some consensus about the risk levels and move the necessary conversations about infrastructure investments.

Hurricane Sandy has recently increased perceptions of urgency about the issue but a number of groups of have been thinking about the issue for several years.   See generally this review of other efforts prepared for this website in September by Erica Mattison.  The National Oceanic and Atmospheric Administration recently produced a new report estimating likely sea level rise by 2100. The Boston Harbor Association — using roughly consistent numbers — has produced a set of maps comparing possible storm surge levels to ground elevations in coastal areas. The Massachusetts Department of Environmental Protection is leading an ongoing study of the challenges created by likely climate change. The Office of Coastal Zone Management is also pushing communities to think about the issue.

NOAA estimates with 90% confidence that sea level will rise at least 8 inches and not more than 6.6 feet above 1992 levels by 2100.  Sea level rise is a result of global warming through (a) the expansion of warming ocean water and (b) the melting of great ice sheets. Ice melt in Greenland and Antartica is especially difficult to project.  Given the wide uncertainty, NOAA’s approach is to create four different scenarios.

  • The Highest scenario, 6.6 feet, assumes the  “maximum possible glacier and ice sheet loss by the end of the century”.  The report acknowledges that there are some higher estimates of ice sheet loss, but discounts them as implausible.  The Highest scenario does, however, project much greater loss than the last international panel report, IPCC4, which excluded “future rapid dynamical changes in ice flow”.   The Highest scenario is over three times greater than the highest suggested rise in IPCC4 (.59 m or 1.94 feet).
  • Two intermediate scenarios at 3.9 and 1.6 feet make more modest projections of ice sheet loss, with the lower of the two defining the risk primarily from ocean expansion due to warning using optimistic assumptions about global efforts to reduce emissions.
  • The low scenario, 8 inches, simply extrapolates observed 20th century sea-level rise with no acceleration due to climate change.

The scenarios above pertain to global average sea level rise.  There is some evidence that sea level rise may be more dramatic along our coast line than in some areas of the world.

Later in this century, when elevated sea levels combine with storm surges like Hurricane Sandy, areas that have been previously safe from inundation will face substantial risk of flooding. It may be that the greatest exposure will be to sub-surface infrastructure like subway and road tunnels and sewer systems. Inundation of these structures could incapacitate the Boston area for extended periods. The investments necessary to adequately control these risks may be large and it seems wise to start to try to bring them into focus, given the lag times involved in major structural investments.

The issues for Back Bay, the Fenway, East Cambridge and low-lying areas further up river are particularly difficult to evaluate. These areas are protected by damsthat keep sea water out. These dams are equipped with huge pumps sufficient to keep pumping the river out, even when harbor tides rise above river level.

According to a 1972 design memorandum from the Army Corps of Engineers (extracted and reproduced as part of MIT course curriculum here), the topography around the dam prevented a dam height of more than approximately 1.4 feet above the highest previously recorded high tide.

According to the design memorandum,

The amount of overtopping that could safely be handled was determined on the assumption that a tidal flood occurred which was 2.5 feet higher than any flood level previously experienced and coincident with a 10 year rainstorm over the Charles River Basin. For these condition[s], the pumps will be operable and could handle interior runoff and overtopping without causing a significant rise in the basin level.

In the scenario envisioned, water would be flowing over the dam from the harbor into the river basin but the pumps could keep up with it. With sea level rise of as much as 3 feet by mid-century and possibly, in addition, higher storm surges due to bigger storms, the probability of a greater overtopping than envisioned seems possible. Evaluation of this risk requires an updated hydrological model — a complex technical effort. Additionally, some careful topographic analysis is needed to understand under what conditions the dams could be bypassed entirely by overland or subsurface flows.

Getting a process going to fully assess the risks will be a high priority for me over the next couple of years.  Most likely, the basic risk assessment process should be driven by state agencies, but we may need to put legislation in place to fully empower them to address the issues.  Of course, cities and towns will have a central role as to their own infrastructure.   In particular, the City of Boston has been monitoring the issue of sea level rise.

Addendum: Here is a link to follow Senator Brownsberger’s bill S.344 on flood planning:

An Act creating a process to evaluate exposure to catastrophic flooding as a result of climate change


Published by Will Brownsberger

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

12 replies on “Preparing for storm surge”

  1. I am glad you are using the higher estimates. The IPCC predictions for arctic ice cap melt have already proved to be far too conservative, and Greenland’s loss of ice appears to be accelerating (though it is still not that fast, as a matter of sea level

    What effect is this likely to have on the lower parts of Belmont? I am somewhat worried that a rebuilt high school will not be high enough, and that the new electrical substation will not be high enough. How costly is it to raise these structures an additional meter or two? What lifetime do we expect for them?

    1. I’m not sure about effects on Belmont. I do know that the lowest neighborhoods in Belmont are actually a few feet higher than some neighborhoods in communities closer to the ocean, so, their risk of inundation is lower in any scenario.

      But this is precisely the kind of question we need better answers to for communities in both the Mystic and Charles watershed.

      1. I’m not expecting permanent wet feet this century, but I have to assume that a 3-foot-higher sea level means 3 feet less head on the Little-Alewife-Mystic drainage route to the ocean, and thus that a smaller amount of rain would be required to cause damaging floods. That’s not a complete catastrophe; we can at least contemplate mitigation (more rain barrels, fewer hard surfaces, more storage) for the ten-year rains. Someone’s got to do the numbers; I recall trying to estimate the usefulness of rain barrels in mitigating a flood, and it was not nothing, but was also clearly only an aid, not a solution (I estimated something like an inch or two less water in Claypit Pond; would be lovely to have a trained professional look at this).

        But at this point, I think that any new construction on low land near rivers (Uplands, ahem) needs to take this into account. Flood maps based on historical data are almost guaranteed to be inaccurate, and we might want land (might want to condemn land) to convert into flood storage for the 10-year case.

  2. Storm surges of the Sandy’s size affect not only Boston but cities and towns ranging from Hingham to Lynn and beyond.

    Antonio DiMambro won the 1988 BSA competition by proposing a series of dams along the natural barrier islands left as drumlins by the receding glaciers of the past ice age.

    It is important for Boston and the adjacent towns to consider how relatively much easier it is to protect their huge real estate assets than it is for New York or New Jersey. When – not if – a major storm surge combines with sea level rise, Boston and vicinity’s real estate assets could be one of the few along the East Coast which would be intact provided that work on such a sea barrier system were to be started promptly.

    London has done so and protected itself at Woolwich since the ’70s, Holland continues to improve its sea wall systems, and Boston’s barrier islands offer a perfect start of a comparably significant protection.

  3. The Boston Harbor Association map for 7.5 feet of flooding would pretty much restore the Boston area to its pre-landfill level. The islands connected to create Logan Airport would once again become islands, the Back Bay would again be a bay, downtown Boston would again be hills and coves, the neck connecting the core city to the hilly southern towns of Roxbury and Dorchester would no longer be our South End but would again be a one-block-wide isthmus that was sometimes awash in high tides. Three hundred years of human land-sculpting would be erased. Take a look:

    As we contemplate how far we should go to protect against 3 to 5 feet of flooding, we should keep in mind that if the flooding exceeds what we’ve prepared for, even by a little, we might have wasted all our effort. And we should also keep in mind that Katrina’s consequences were made much worse by the dredging and destruction of salt marshes undertaken by the Corps of Engineers.

    In other words: proceed with caution.

    1. Definitely proceed with caution — and with urgency.

      Worth noting though: The TBHA maps are based only on elevations and do not factor in the presence of dams and pumps protecting the interior watershed areas. We need some hydrological modeling to better evaluate the risks.

  4. Will,

    Your website is well set up and seems to have attracted some very thoughtful comments.

    My first thoughts are that there are risks in thinking TOO MUCH about sea level rise from global warming. As you know, the models give differing results. depending on the optimism or pessimism of the inputs.

    A valid concern is that we might be looking at the wrong effects of global warming. There are several things about Hurricane Sandy that tweaked my attention :

    (1). The storm was very late in the season, late October, when the Hurricane season usually ends by September 30. Were the ocean waters in the Gulf significantly warmer?

    (2). The storm was a Category 1 hurricane in terms of wind speeds. But it was a huge storm affecting a very large area. Category One storms do not usually cause this sort of damage.

    (3). The computer models did a good job of tracking the storm over water, but not over land. Almost all the models had the storm turning northwest through New Jersey. A very strange path but the weather forecasters got this one right.

    (4). The storm followed a very odd path when it hit land : west to Pittsburgh, and then straight North into Canada. None of the models picked up this possibility.

    (5). Virtually all of the storm damage was related to wind and tidal surge. These are typical hurricane effects in coastal areas. I heard no mention of flooding caused by rain alone.

    (6). The forecasters got the tidal surge very wrong. Early estimates of 5 to 7 feet had to be changed to 11 feet a day before the storm hit land. The actual tidal surge was 14 feet — higher than anyone had predicted. No one seems to be discussing the details of the surge projections.

    (7). I still have not figured out why the City of Hoboken stayed flooded for so long — days.

    (8). My guess is that the tidal surge in New York was so bad because the Category One hurricane was such a large storm, extending over such a broad area. This wide low-pressure area had the effect of pulling the tide levels upwards over an extensive area of water, magnifying the surge elevations.

    (9). Boston is less vulnerable that New York City because it is protected by Cape Cod. The Cape has the strange effect of reducing normal tides to a variation of 1 to 2 feet — much less than the ten feet typical of Boston Harbor. As I understand it, if Sandy had hit Boston, it might have produced a tidal surge of seven feet, rather than the 14 feet that New York received.

    (10). So we are talking about tidal surges of 7 to 14 feet. These surges are larger than the most extreme sea-level rise predictions of 6.6 feet in the next 90 years.

    (11). How should we estimate future flooding potential? We would need to ADD the background sea level rises due to global warming PLUS the tidal surges. Such a result would mean that Boston coastal flooding a century hence could be as bad as New York City just experienced.

    (12). FEMA has no planning role over coastal flooding and tidal surges. FEMA considers only rain-related flooding. The Army Corpos of Enginers considers the coastal effects and has produced maps showing a Category One hurricane causing extensive flooding at Alewife.

    (13). The Tri-Community Flooding Group for over a decade did not talk about the effects of tidal surges. All discussion was on FEMA rainfall flooding. The subject of tidal surges naturally came up at their last meeting on November 13. I discussed the matter briefly as a citizen, but I had the sense that none of the municipalities wanted to talk about the consequences of tidal surges.

    (14). Global warming could have an effect on hurricanes that is far more significant thatn simple sea level rise. If the hurricane season is extended, and if the hurricanes more frequently track inland, the flooding consequences could have large impacts much more quickly. In the past two years, we have had two major hurricanes that moved inland after coming up the coast. Both caused damage in New York City. Hurricane Irene in 2011 went west of Boston, with damage to western Massachusetts and Vermont. Sandy in 2012 turned dramatically west and affected communities as far west as Ohio. Prior to 1938, almost all hurricanes in New England went out to sea, with no damage. The 1938 hurricane went straight north up the Connecticut River Valley. In recent years that have been more instances of hurricane making landfall through Massachusetts and Maine. For Massachusetts to have two hurricane in two years bypass to the WEST should really challenge out thinking and out planning.

    (15). the bottom line is that we must consider the combined effects of general sea-level rise and of severe hurricanes, due to the size and path of the hurricane — possibly affected by global warming.

    Stephen H. Kaiser
    191 Hamilton Street
    Cambridge, Mass. 02139

    1. I completely agree with your bottom line. Everyone in the conversation is talking about the combined effect, but I think people feel even less certain about how the storm surge magnitude is going to change than they do about sea level rise. So, they tend to focus on SLR as a baseline. But yes, there is certainly reason to expect more frequent and higher storm surge and that makes the concerns even greater.

  5. If we in Massachusetts are serious about achieving the goals of the Global Warming Solutions Act of 2008, and doing our part to preserve the global ecosystems that support all life, then we must insist on significant reductions in greenhouse gas emissions from all major sources. However, the Massachusetts Department of Environmental Protection has just announced new water withdrawal policies that would accommodate increases in water withdrawals rather than require improvements in water use efficiency. The Safe Yield withdrawal limits announced by DEP on December 3 are almost double current withdrawals in the Charles River basin, triple those in the Concord River basin, and six times higher in the Parker River basin. This affects the Global Warming Solutions Act because approximately 12% of total energy usage is related to water use.

    Safe Yield limits that are higher than current withdrawals amount to an institutional denial that the amounts of water we have been withdrawing since passage of the Water Management Act in 1986 – amounts that have contributed significantly to dry rivers, disrupted ecosystems, inferior drinking water quality, and elevated greenhouse gas emissions – are a problem. Allowing these Safe Yield limits to go unchallenged would amount to exempting the water supply sector from having to reduce water-related GHG emissions. That would mean that non-water sectors would have to reduce their GHG emissions by over 90% in order to reach the Global Warming Solutions Act target of an 80% reduction by 2050.

    Massachusetts legislators displayed admirable leadership in passing the Global Warming Solutions Act in 2008. They took a leap of faith by setting a goal of 80% reduction of greenhouse gas emissions by 2050, despite the long odds of actually reaching that goal, in order to help save our grandchildren from catastrophic climate change. Why can’t the Department of Environmental Protection now follow that example and determine scientifically justifiable Safe Yield limits, while giving communities sufficient time to achieve their targets, and dealing with non-compliance by requiring more aggressive conservation measures (such as conservation-oriented water rates) rather than unproductive fines? What possible harm could striving for such a goal do? On the contrary, the long-term cost of water supply would be reduced, drinking water quality would be improved, jobs would be created, and greenhouse gas emissions would be trimmed.

    Yet the main thrust of the state’s latest water policy has been to accommodate business as usual, no matter how inefficient and/or frivolous current water use practices may be, and no matter how dire the threat of climate change. Allowing DEP’s unsafe Safe Yield determinations to stand would imply that we didn’t really mean it when we passed the Global Warming Solutions Act.

  6. Re Will Brownsberger’s blog post, “Preparing for storm surge”, 12/15/2012.

    First, a brief summary of Will’s post:

    Will wrote that given the low-lying areas he represents along the Mystic and Charles, he’s looking for “consensus about the risk levels” and wants “conversations about infrastructure investments”. He notes that Hurricanes Sandy and Irene have accelerated the discussion.

    Climate change raises sea levels and tidal surges through ice sheet melting, thermal expansion of melted water, and more frequent and severe storms and associated storm surges. Flooding can be tidal, across land, backing up rivers and streams, and inundating below-ground facilities.

    With 90% confidence, NOAA predicts sea level rise through 2100. The low is 8 inches, derived by linearly extending 20th century rates of sea level rise with no further allowance for climate change. Higher rises, of 1.6, 3.9 or 6.6 feet reflect different assumptions about rates of ice sheet loss and other factors.

    Existing pumps on the Charles and Mystic rivers can prevent lowland flooding consistent with the storm surges for which they were designed. They can handle the lower end of sea level rise predictions, 2 to 3 feet at most; they certainly cannot handle the higher end.

    My comments

    Possible responses are limited in scope and expensive to do. Adding pumping capacity to existing dams will be expensive. That capacity is limited by the structure and the height of the existing dams. Adding height to existing dams will be even more expensive. That too is limited by the existing structure and by physical topography of the surrounding area. Beyond that, physical topography prevents further protection except by building additional physical barriers as does Holland, which will be hugely expensive.

    Overall, the cost of each inch or foot of flood protection is very high. The marginal cost additional inch or foot will rise quickly.

    As a society, at the local, state and national levels, we simply don’t have the money. We are currently debating what shares of our income should go to continuing present operations, funding future capital needs and pension obligations, and paying back past debt.

    Thus, we are caught between a rock and a hard place. So far, we have been both unwilling and unable to act (so far, when it comes to conservation and climate change, all our actions, both individual and collective, however laudable, have consisted of picking the only the lowest of the low-hanging fruit). Do nothing, and allow the situation to get worse, or act, at severe cost. In short, each year, the rock gets bigger and heavier, and the hard place gets harder and harder to get out of.

    As the cost rises, the case will be made, “We *have* to do these things, either because the cost of not doing so will be even greater, or because we find unacceptable the ways we will have to change our daily way of life.” The action that we will *have* to do may be something to cut global warming, e.g. a carbon tax, or it may be something that adapts to it, e.g. building ever-higher dams. We need to make sure that as often as possible, we choose reducing climate change over adapting to it, because, in the long run, we cannot adapt to it.

    Naomi Klein’s book “Disaster Capitalism” suggests that like the banks, the rich and the elite are making their money off of the rest of us by destroying the environment. While that is arguably true, I think she ignores that it’s not only the rich who benefit, we all do. As Pogo said, “We have met the problem, and it is us”.

    We are already paying the costs, but they’re being increased gradually, so as not to bring out major protest. Those who live in the recently extended FEMA flood zone now *must* buy flood insurance as a condition of mortgage, must pay more for it, and have had the value of their houses reduced. Anyone wanna sue Cambridge for property taking?

    I recently received a home insurance bill. You guessed it, it jumped. (And I’m *not* in a flood zone.) All the insurers need to recoup their losses on Sandy, Irene, and other events. They are factoring future expectations of increased climate change and greater economic losses into their premiums.

    The Markey report

    Let me introduce some new information, “The *New* New England”, the report of (the Democrats on) Congressman Ed Markey’s Natural Resources Committee, issued 10/25/2012 (Google “Markey Natural Resources New England Climate report”). At only 15 illustrated pages, 4 of which are the bibliography, it’s a quick, high-level read.

    Its point: anthropogenic climate change has already changed the New England climate to our considerable cost, and that both the change and the cost will increase over time. The more we do to reduce the rate of global warming, and the faster we do it, the less worse off we’ll be, but no matter what, we have and will continue to incur substantial costs for what we’ve already done.

    On flooding, which is only one of several types of changes the report discusses, it notes:

    “Rates of sea-level rise from North Carolina to Massachusetts are two to four times faster than the global average. Many of the region’s population centers, economic engines and historical landmarks will be inundated.”

    “Precipitation is increasingly erratic … extreme rain and snowfall … making damaging floods more likely.”

    “Massachusetts loses an average of 65 acres (2.8M sq ft) to rising sea levels each year.”

    Figure 4, p. 8, shows inundation of almost all of Boston’s waterfront and Seaport district under a “high carbon emissions scenario”. From a flooding perspective, Boston Mayor Menino’s desire to move City Hall to the waterfront is a really bad idea, unless he makes sure that City Hall is also “City Hill”.

    More of my own comments.

    So, what can we do?

    Extend the “no-build” distance from rivers and streams. Extend the domain of wetlands buffers. Years ago, as conservation measures, these were created, for a mix of esthetic reasons, to avoid damage to rivers and streams, and to prevent property damage. If we can expect flooding to be more frequent and/or severe, it may be time to make those boundaries larger.

    In general, tailor local zoning codes more tightly to local conditions. For instance, on hilly lots, require more open space or underground wells to collect surface runoff, and/or otherwise “capture” a larger fraction of the fast surface runoff which would otherwise run off the property.

    Building codes change slowly. Sometimes, it helps when an industry or national group leads the way. For instance, in light of the major electrical damage Sandy caused to subsurface wiring, both in homes and in subways, maybe it’s time to require that fuseboxes and other critical infrastructure be placed somewhere higher up, in a manner still consistent with safety. Perhaps an industry or national group can come up with specs that can be adopted or adapted at the local level.

    Other countries have experienced the need for massive rebuilding following wars (Europe WW2), economic collapse (Eastern Europe following the end of the Cold War), or disasters (NY and NJ following Sandy). When they rebuilt, the did not merely restore what had been, but built better. We should do the same.

    For instance, this country needs roughly $1 trillion in water/sewer infrastructure spending. The need is there, the economic stimulus would be valuable, and low interest rates make it a good deal. While Republicans are doing their level best to obstruct it would be a good time to upgrade the standards new facilities should meet. So, for instance, design plants so that they can be isolated from flooding as much as possible. When they do flood, power systems, electrical systems, control facilities should be situated high enough above ground so as not to be inundated; ditto any backup equipment. Design equipment that *can* be flooded so as to to minimize loss, allow easy replacement, and allow restoration of capability as soon as possible afterwards.

    Add disaster capacity to our public buildings. We need roughly another $1 trillion for education infrastructure, ranging from elementary schools to university research labs. Just as no one today would build without allowing for Internet wiring and for energy conservation, perhaps we need to similarly build in the capacity to provide public response during disasters.

    For instance, perhaps large buildings should be *required* to build in the capacity to serve as shelters for some specified number of people for a specified period., in the event of a major public disaster, That way, when people *are* displaced from their homes, they can still be nearby. Along with a “Certificate of Occupancy”, a building might also be issued a “Certificate of Emergency Occupancy”, e.g. “Can feed 1,000 and shelter 700 for up 4 weeks”. It’s possible; after all, those canned crackers from 1950’s bomb shelters are still edible!

    We can take cues from what the private sector is already doing. None of the new office buildings in the Alewife floodplain (on Cambridgepark or Acorn Park Drives) have basements. The *only* thing you may find at ground-level is parking. Any indoor space is at least 6 feet above ground level (ditto the local electrical substation nearby). HVAC and other building-critical equipment are on the roof.

    On a more humorous note, perhaps, the Belmont Uplands should be proactively renamed “Belmont Island”, and developer O’Neill be required to provide ferry service during major floods. Mitt Romney could relocate his money from the Cayman Islands to a more local offshore facility! Or, redesigning the whole building to house corporations instead of people would give a whole new meaning to the phrase, “condos for cash”! Belmont could become a tax shelter!

  7. Will, thank you for this.

    A number of specific comments:

    1. The sea-level rise needs to be seen in the context of global warming as a whole. The NOAA report, I believe, was out before the recent finding that the melting permafrost is giving off vast amounts of methane.

    The World Bank report on climate change definitely came out before the permafrost information. Depending on scenarios, they suggest a rise of 4 degrees Celsius by 2060-2100. (Nor would it stop then.) And they say civilization will be untenable at that point – hundreds of millions displaced, societies ended, etc., etc. If we stopped carbon emissions now, we would still be in for large rise in global temperatures. [ and There was another major very mainstream-reputable and chilling report on global warming recently, but I have mislaid the information on it.

    As Aram Hollman indicates, the costs of stopping carbon emissions are far cheaper than the costs of not stopping it.

    2. Re new construction, especially on low ground: it covers ground which otherwise absorbs rainwater, and thus negatively affects all of us.

    3. With regard to Sue Bass’ comment, there will be one chilling difference in the Boston topography: I believe the original hills are far less tall now, as they were cut down to use the soil as infill.

    4. As a Cambridge resident, I would love to know the flooding scenario for the whole city.

    5. From Stephen Kaiser’s comments, “The Army Corps of Engineers considers the coastal effects and has produced maps showing a Category One hurricane causing extensive flooding at Alewife.” “At Alewife” means what, exactly?

    6. Also re Stephen Kaiser’s comments, the Gulf water generally is getting warmer, I believe, along with the rest of the oceans, although I don‘t know specifically about recently.

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