High Waters, Higher Stakes: Why Cambridge Must Rethink Future Development

High Waters, Higher Stakes: Why Cambridge Must Rethink Future Development

Written in conjunction with the Cambridge Citizens Coalition

The construction/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 proactively withdrawing 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, which 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 located near sea level and adjacent to the Charles River, Alewife Brook (and numerous buried tributary streams), and Boston Harbor, Cambridge faces mounting challenges from climate change. According to the City of Cambridge’s Climate Change Vulnerability Assessment (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 currently at or below 12 feet above sea level could be increasingly subject to chronic flooding.

As soon as 2070, flood zones will include East Cambridge, Cambridgeport, Wellington/Harrington, North Point, MIT/Kendall, Harvard Square, North Cambridge/Alewife, Area4/The Port, and other areas. (Image: Boston Harbor Now.)

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 like 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 constructed 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 place a considerable financial burden on both the public and private sectors. For example, the National Oceanic and Atmospheric Administration (NOAA) reports that the U.S. 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 any 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 withing 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.

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Note: If you weren’t around to witness the flooding of February 6, 1978, this video clearly illustrates the human impact of the flooding disaster in Revere. https://youtu.be/eRHoWqdSv_M?si=wEuICKlRweUKSCsF