Two If by Sea: The Urban Implications of Living with Water

ULI Boston/New England recently published a report, The Urban Implications of Living with Water, drawn from a charrette charged with exploring strategies for dealing with the effects of rising sea levels. It addresses four areas of Boston: the historic Back Bay neighborhood, Revere Beach, the Alewife Quadrangle, and the Innovation District—the target of a city initiative to transform 1,000 acres (405 ha) of South Boston waterfront lying between Boston’s transportation gateways. Here is a look at the charrette participants’ thoughts about building resiliency into the Innovation District, the city’s largest tract of underdeveloped land.

The Innovation District faces significant risk related to sea-level rise over the next 100 years. In the near term, a 2.5-foot (0.8 m) rise is predicted by midcentury, whereas a 7.5-foot (2.3 m) rise is predicted by 2100 and beyond. Rather than look at rising tides as having a negative impact on the Innovation District, solutions should provide opportunities to improve the environment and the area’s relationship with the city.

Related: Boston Living With Water

Instead of building a higher sea wall, what if the city reenvisioned the existing HarborWalk as a place that would both protect the city from an additional three feet (1 m) of sea-level rise and provide a series of public amenities? This new HarborWalk could incorporate recreational areas, and the landscape surrounding it could function as both public space and soft infrastructure, absorbing water or mitigating tidal impacts.

Measures should not only improve resilience, but provide ecological benefits as well by enhancing biodiversity. Traditional hard/gray solutions should be balanced through incentive programs with soft/green measures, given that adding green space is itself a resilience measure. Planted or porous surfaces not only act as sponges to help absorb and release water over time through groundwater transmission and evapotranspiration to reduce the impacts of increased storm and flood frequency, but also help mitigate heat islands.

With the future unclear about exactly when the full impacts of sea-level rise will occur, designing now for flexibility and the ability to adapt becomes critical. For example, with major street sections to be rebuilt, the typical 60 or 75 foot (18–23 m) cross-section can be planned to be able to change when conditions warrant. The goal is to provide for current urban linkages across the district without limiting the ability to accommodate future needs. Such needs could take the form of green infrastructure or surface channels to move water safely and quickly back to the ocean.

Designing for sea-level rise is not the same as preparing for the next superstorm. The majority of developments in Boston are preparing for emergency conditions such as hurricane-induced storm surges, not for consistent, pervasive conditions as a result of higher sea levels. It is understandably difficult to think about living with higher water and frequent inundation as a long-term, permanent condition, specifically because priorities change when it is already so costly to build in the Innovation District that it would be almost impossible to make development financially feasible if additional resilience measures for rising tides are required. Given current development costs, the strategies that are to be proposed should have minimal cost impacts on current development pro formas and allow building owners and the government to retrofit buildings and streets later, when sea-level conditions reach critical levels.