The construction and relocation of infrastructure, buildings and communities from areas that are vulnerable to flooding, erosion and other environmental hazards is referred to as “managed retreat.” This concept has become a critical tool for climate change adaptation, particularly in regions facing rising sea levels and increasing storm intensity. By withdrawing proactively from high-risk areas, managed retreat aims to reduce damage, protect human lives and minimize economic losses over the long term. It is often paired with policies to restore natural ecosystems, such as wetlands and floodplains, that can serve as buffers against flooding.
In Cambridge, managed retreat is an especially relevant strategy. As a city with a significant portion of its land near sea level and next to the Charles River, Alewife Brook (and numerous buried tributary streams) and Boston Harbor, Cambridge faces mounting challenges from climate change. According to a City of Cambridge Climate Change Vulnerability Assessment in 2017, parts of the city are at risk of experiencing flooding due to sea-level rise and storm surges. Projections indicate that sea levels in the Boston area could rise by 4 to 7 feet by 2100. With storm surges and tides, this means areas at or below 12 feet above sea level could be increasingly subject to chronic flooding.
The combined effect of rising oceans, storm surges and king tides (monthly tidal surges during the new moon) further exacerbates the risk of flooding in low-lying areas. Rising sea levels create a higher baseline for storm surges, which are temporary increases in water levels caused by strong winds and low atmospheric pressure during storms. When storm surges coincide with king tides– the highest tides of the year – the resulting water levels can lead to severe and widespread inundation. These compounding factors not only increase the frequency of flooding events but also amplify their intensity, making it imperative for all coastal cities such as Cambridge to adopt proactive measures to safeguard vulnerable areas.
Given this context, Cambridge should limit larger projects – perhaps those exceeding 10,000 square feet – to be built in areas that are at or below 12 feet above sea level. There are several reasons for adopting this policy.
First, allowing large developments in low-lying areas exacerbates the risks associated with flooding. Structures in these zones are likely to sustain significant damage during extreme weather events, resulting in high economic costs for property owners and the city. Insurance claims, disaster relief and rebuilding expenses put a considerable financial burden on the public and private sectors. The National Oceanic and Atmospheric Administration reports that the United States has experienced a sharp increase in billion-dollar weather-related disasters, many of which are driven by coastal flooding.
Second, larger developments often involve extensive infrastructure, such as underground parking, utilities and sewage systems, which are particularly vulnerable to water damage. Inundation of these facilities can lead to cascading failures, including contamination of water supplies and disruptions to essential services. Preventing such developments in high-risk areas helps safeguard the city’s critical infrastructure.
Third, prohibiting large projects in flood-prone zones aligns with Cambridge’s broader sustainability goals. The city has committed to achieving net-zero carbon emissions by 2050, and prioritizing development in safer, higher-elevation areas reduces the need for energy-intensive flood defenses. Additionally, restricting construction in vulnerable areas opens opportunities for restoring natural floodplains, which can absorb excess water and mitigate the impacts of storm surges.
The reality of widespread flooding isn’t in the far future. Some parts of Cambridge and Boston are already experiencing regular flooding due to precipitation and tides. Exacerbating efforts to mitigate precipitation flooding is the extent of Cambridge’s impervious surfaces, which include rooftops, pavement, patios and parking areas – and the attendant loss of green space. As development increases, rainwater runoff increases, placing an increased strain on these flood-prone neighborhoods. Stronger storms are becoming increasingly common, which will result in still more flooding. As a city, we need to start thinking about a reduction – or at least no net gain – of the amount of impervious surfaces.
Absent from the city’s lengthy Resilient Cambridge Handbook is even the mention of managed retreat. While we’ve been able to ignore the threat posed by rising oceans, no amount of resiliency planning or barriers will allow us to escape the rising ocean for much longer. The prediction is that we’ll have slowly increased tidal flooding every year, and that within the lifetime of today’s children, large areas of the city will become uninhabitable. The policy of managed retreat encourages equitable and smart urban planning. Flooding disproportionately affects low-income and marginalized communities who may lack the resources to recover from disasters. By steering development away from high-risk zones, Cambridge can reduce the likelihood of displacement and ensure that vulnerable populations are not left to bear the brunt of climate change impacts.
Managed retreat is a forward-thinking strategy that prioritizes safety, economic resilience and environmental sustainability. Cambridge should adopt a policy prohibiting large-scale developments in areas at or below 12 feet above sea level. This approach not only protects the city from future climate risks but also demonstrates a commitment to responsible and equitable urban planning.
Note: If you weren’t around to see the flooding of Feb. 6, 1978, this video illustrates the human impact of the flooding disaster in Revere.
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I’m sorry if I don’t believe this editorial to be in good faith. The anonymous authors simply signed “ Cambridge Citizens Coalition”. This organization has consistently opposed _any_ housing in our city, especially in the west Cambridge currently zoned single family residential. So now they say “don’t build since our lifestyle with driving everywhere is causing the seas to rise”. How interesting. Also interesting that in a single week we have CCC attacking pro-housing councillor and now this, great job CambridgeDay, slow clap
Wow… almost a caricature at this point
Anyway, I suggest that any supporters of the CCC living in the highlighted areas goes ahead and “retreats” to somewhere else. Florida? Those of us remaining can figure this out.
Stroll from Mt. Auburn Hospital to Huron Village or BB&N. You’ll see loads of big, often part-time-occupied homes.
Most seasons you’ll see professional lawn care pickup trucks idling at the curb, of huge gardens or yards, gas leaf-blowers deployed.
These properties have benefited from a FAR that means nobody can develop anything else on the properties. Until, hopefully, this coming week.
Often as not they’ve got a CCC sign out front:
“Green space is not a luxury,” some read. What a deflection. If only country club Cambridge has it, then what is it?
Like this editorial, that concept has merit. But CCC only picks up the next idea at hand when they can use it to defeat a vote for progress. I want to read this without cynicism, but given the track record, how could one not?
Should the ordinance pass, let’s see if they bring this idea up to indeed make Cambridge more resilient by further upzoning Huron Village/Observatory Hill. But, why start now?
It’s not every day that I agree with Triple C, but their suggest that we undertake significant building in West Cambridge is really compelling.
Brattle St largely falls at 40 feet above sea level, Observatory and Avon hills are even higher. Since new construction is subject to more rigorous storm water detainment regulations than existing construction, this will reduce flooding risk in the low-lying and low-income parts of the city.
This is the kind of forward looking, smart development we need to improve climate resilience in Cambridge.
OK, does the CCC support significantly removing restrictions. on high-density development in areas not impacted by flooding (like most of West Cambridge or Baldwin)? Or raising property taxes to pay for flood mitigation measures? (They don’t.)
Or are they really just interested in opposing housing, and will latch on to any suitable excuse?
Many parts of the world are already experiencing dire climate disasters, including devastating flooding. If these are the parts that could flood in 2070, Cambridge seems like overall a pretty safe place to build housing, with appropriate mitigation. Maybe we should build more housing so climate refugees from all over the country and world can join our community. Building more housing is good for climate change too!
Managed retreat? I call on the authors of this insightful piece to lead the way.
The CCC has a history of opposing affordable housing development. Now, they’re using a new tactic: climate change and flooding.
Their solution? Relocate residents from flood-prone areas—conveniently, areas with a high proportion of renters.
Don’t be fooled: affordable housing and flood mitigation can coexist. They ignore solutions like flood-resistant buildings with raised ground floors for community spaces or public-private partnerships requiring both resilience and affordability.
Notably, their plan does not include zoning reform, which could increase density elsewhere and provide displaced residents with housing.
https://www.cambridgema.gov/Services/climateresiliencezoning
I encourage readers to review the existing rules in Cambridge with regards to climate resiliency and flooding, which will be in force for new builds.
@praccu It’s reassuring that the city’s climate resiliency and flood plan doesn’t just displace renters like the CCC plan.
I wonder how many CCC members live in the “retreat zones” they propose.
Why the hate? But to further constructive dialogue: In 2021 CCC submitted the first citizen upzoning petition to end single family zoning & increase housing HERE. They have written about the luxury housing upzoning on their WEBSITE providing well researched documents on the severe risks of displacement and gentrification: (1.30.25) HERE; (1.25.25) HERE; (1.16.25 ) HERE; (1.14.25) HERE and (1.13.25): HERE. They have written about the large problems with land/housing speculation (which will now increase): (12.17.24) HERE; (12.9.24) HERE; (10.23.24) HERE; (12.4.24) HERE; (11.27.24): HERE; and (11.10.24) HERE. They have addressed the large scale environmental impacts in play: (1.29.25): HERE (1.21.25) HERE; (1.25.25) HERE; (10.3.24): HERE; and (9.29.24): HERE.
As with this post, City Planning is critical to growth (Envision): “Move quick & break it” is not a viable position anywhere, much less in an already very dense city such as ours.
@avejolt: None of those links work, but I went ahead and read parts of the 3C site.
Norris (1.30.25) correctly observes that property values will increase, but overstates the extent to which they will rise. Construction is expensive. The margins at 4 stories aren’t sufficient to justify knocking down 3 stories.
I also read through the 3C’s 2021 zoning petition. There is some good stuff in here. For example, allowing condoization. There’s some bad: freezing building facades.
It’s great that there’s some common ground, but I am intensely skeptical of proposals from the 3C. They appear to be deliberate attempts to stop zoning changes that will produce more housing, thereby juicing property values for incumbent landlords.
@cantabrigand: Good on convergences. Links worked when posted. Not sure what happened, but posts are there at @cccoalition.org. Agree on Norris (but amounts aren’t known yet). On 2021 zoning petition: facades not frozen but encouraged and could be altered with design review. Strong concern that proposed upzoning will lead to 1) higher housing costs for everyone including renters; 2) likely will lead to more gentrification; 3) grave concern that FEWER homes will be built as multi-family properties are converted to larger super expensive McMansions and luxury condos.
Research overwhelmingly shows that upzoning, combined with affordable housing policies, lowers housing costs—it does not lead to McMansions. Such claims are classic NIMBY fearmongering.
The CCC letter pays lip service to “equitable planning” but their plan would deepen existing inequalities.
It ignores the challenges of managed retreat, including the costs of relocating infrastructure and communities.
In fact, they offer no relocation plan. They advocate retreat from renter-heavy neighborhoods while opposing zoning reforms that would allow more housing in safer areas.
So yes, @cantabrigand, your suspicion is justified—the CCC’s real goal seems to be blocking new housing. And who benefits? Existing homeowners.
@avejolt The Donovan petition would have been an improvement over the current zoning but it would not have made much of a difference. It would have created few new homes and (from what I can tell) zero new inclusionary homes.
Cambridge has not built enough homes to keep up with job growth for decades. This pushes up prices because it forces existing tenants and new workers into a zero sum competition for the existing homes. I can see why some people would prefer that the building stock stay as it is or have minimal changes. That’s a perfectly valid preference to have. But failing to build enough housing in an economically thriving city does impose costs that fall on renters and people looking to buy homes and stay here long term. The available evidence has consistently indicated that more housing helps with housing affordability:
https://www.tandfonline.com/doi/full/10.1080/10511482.2024.2418044
Managed retreat is one of many ways to put the environment first, ahead of ourselves. We will not be here in 100 years, someone else will, planning for them is forward-thinking and ethical. Let’s put the environment first. Those against managed retreat and other environmental measures are not only shortsighted but selfish. Please, climate change is real.
Problems with the original premise of this, it talks about Tidal effects… in case anyone doesn’t know, the Charles River where we live is NO LONGER TIDAL and hasn’t been since the building of the dam downstream between us and the sea, back in 1910.
LL, let me know when you retreat then maybe I’ll follow
CJoe: Sorry No. Read Resilient Cambridge: HERE “Alewife, an inland area in western Cambridge, will likely be the first impacted by sea level rise and storm surge due to regional topography and flood pathways….Extreme precipitation, sea level rise, and storm surge caused by climate change are threatening the City’s aging hydrological systems. The MA. Coast Flood Risk Model for sea level rise and storm surge predicts that the Boston Harbor area, including Cambridge, is expected to experience almost 1 foot of sea level rise by 2030 and more than 4 feet of sea level rise by 2070. Based on previous projections…the Amelia Earhart Dam was at risk of being overtopped by 2045 by the 1% Annual Storm…a storm that has a 1% chance of occurring in any year, … —a 100-year storm—while the Charles River Dam was at risk by 2055 from a similar 1% Annual Storm. Today, because of updated SLR and SS projections, the dams will likely be compromised earlier.
@avejolt (Suzanne, is that you?) You need to copy the actual URL for links to work here, embedded links aren’t supported.
The “upzoning will result in McMansions” argument has been thrown around a few times, but I don’t understand the argument at all, can you explain it? Nothing under the current zoning forbids tearing down triple deckers and replacing them with large Single Family Homes. A few empty lots in East Cambridge have in recent years been built as large SFHs, for example. The upzoning proposal doesn’t make it any easier to build larger single family homes, either. Given that upzoning will likely lead to increases in land values, I would imagine that downconversions would be _less_ likely, not more likely.
Can you explain the logic that more McMansions would be built under the current proposal?
It seems like multi-billion-dollar developments in low regions are one of the best ways to protect Cambridge.
If MIT, Harvard, Alexandria, and friends collectively have hundreds of billions in assets in areas impacted by rising sea levels, I expect we’ll see whatever levees, pumps, or other infrastructure needed to keep Cambridge safely above water. If it’s just single-family homes, should the sea rise too far, I expect we’ll all be literally under water.