Brooklyn Bridge Park has been an experimental, paradigm-shifting project because the vision for the park was audacious at its very roots. The Brooklyn Bridge Park Development Corporation, created through a joint agreement between the City and State of New York, gave our team the responsibility to address a broad variety of issues that aren’t typically directed by landscape architects. These included revenue planning, development guidelines, urban infrastructure, homeland security, environmental sustainability, and sea-level rise. We were given unusual tools to create a new urban context in which the park would thrive — a city-making project as much as a park-making project.
We saw a complex, resilient, dynamic water’s edge as the core park experience. So, through planning and design, the idea was to vary the things that happen along the 1.3-mile waterfront: bringing people down to meet the water’s edge and also creating opportunities for raised prospects. Other features — such as a remnant pile field, a spiral tide pool, and a salt marsh — called attention to the unique ecological context of an urban tidal estuary.
At the time, we were also working on another waterfront park where tidal surge was a concern, and we had been contending with tight constraints that limited our ability to manipulate the grade, which had been a source of frustration. We were in the schematic design level, with an already developed grading plan for Brooklyn Bridge Park, when — clichéd but true — I was in the shower when I realized that although we were constrained in the other park, at Brooklyn Bridge Park we actually could raise the overall elevation.
By starting with a higher base elevation, the bottoms of the root balls of the trees we were planting — or at least the vast majority of them — would be above the 100-year flood line, which at that point was set at 1 foot higher than any flood ever recorded on the site. Even though the surge from Superstorm Sandy came in higher than our extreme flood benchmark, my shower epiphany turned out to be fortuitous because when the storm came, the only trees that suffered were the ones planted at the park entrances, which were low points because the park needed to meet the grade of the city streets.
Raising the park was an intentional strategy for protecting it against sea-level rise, but other more intuitive aspects of the design were also helpful when it came to the park’s performance in an extreme-weather event. For instance, we replaced long extents of relieving platforms and retaining walls along the water’s edge with riprap, which is a wall system of large irregular stones stacked on one another. Whether built of wood, metal, or concrete, a system of waterfront-relieving platforms and retaining walls relies on tension coming from the land side and compression from the water side to stand. Riprap, by contrast, works with gravity and is fundamentally self-stabilizing.
Although there is a logical urge to worry about the destructive force of floodwater coming in, it is actually the force of the water on its way out that is typically the cause of a wall being blown out. When the flood recedes, the ground is saturated, and hydrostatic pressure can build up behind a solid wall, causing failure. The generous gaps between individual stones in a riprap wall create a porous edge that offers abundant opportunities for the water to flow out. Even if there is some movement of individual boulders, that’s fine because although the riprap system is robust, it is also fundamentally mutable. It will be there until the next ice age.
There was a fair amount of complexity in how this played out, but the way that our team made Brooklyn Bridge Park climate-ready is almost ridiculously simple: We raised the site, especially the trees, and we made our water’s edge a porous gravity wall that doesn’t try to hold the water back. We relied on time-tested and technologically simple solutions. Now that more than six years have passed since the first sections were open, and four years since Sandy, the plants have begun to grow in, and it is amazing even to us the degree to which urban nature has become the image of this highly urban park. This fundamental rebalancing of “natural” and “human made” was part of our strategy for resiliency but also essential to making a welcoming park on this site.