07. November 2012 / Susannah C. Drake
Lower Manhattan: A New Urban Ground
Topos published the concepts for "A New Urban Ground" in Topos 73 – a short reminder of the ideas and approaches by ARO & DLANDSTUDIO, Stephen Cassell, Susannah C. Drake, Adam Yarinsky:
In the aftermath of Hurricane Sandy, ideas developed in the 2010 MoMA Rising Currents exhibition are even more prescient. As designers we suggested a future that altered the relationship between ecology and infrastructure in Manhattan to fundamentally reconfigure the character of the city. Historically, the island of Manhattan was surrounded by a buffer of shifting marsh lands that protected upland areas from storm impacts. The current ubiquitous hard edge condition creates a clear oppositional relationship between land and water that left the city disabled and scarred from storm surge flooding. By alignment of the advantages of naturally-occurring and man-made systems in an integrated and reciprocal organization of natural systems with the city’s current infrastructure can transform the city both in use and experience.
New York Now: The Challenges
Climate change is causing an incremental rise in the world’s ocean level that scientists project will hit 6 feet by 2100, inundating 21% of Lower Manhattan at High Tide. The 14 foot storm surge that crippled the city for a week would be doubled in a category 2 hurricane later in the Century.
New York 2100: The Possibilities
Given the large threat of flooding due to climate change and the high value of Lower Manhattan real estate, a major intervention is necessary to protect existing assets and re-integrate a missing ecology. A combination of a raised urban edge and modified in-street infrastructure will protect the island from flooding while providing a more flexible system to respond to climate change. Our proposal consists of two basic components that form an interconnected system: porous green streets and a graduated edge.
A New Street Ecology
City streets offer an opportunity for a new ecological infrastructure. 80 acres of freshwater wetland are necessary to absorb upland runoff for Lower Manhattan. Integration of an interior porous street network and exterior marsh system would manage flows. Up to the reach of a Category 2 Storm surge, the streets are rebuilt as a connected series of porous conduits that drain storm water without impeding vehicular circulation. This new conception of “street” will not only provide more productive park space within the city, but also reconstruct the urban experience through a greater understanding of sustainability. This highly efficient system includes existing services (water, sewer, gas and electric) relocated in accessible waterproof vaults beneath the sidewalk. Fresh water inputs from upland sources are a valuable resource for maintaining health of the ecology after a large storm event. Cisterns and Blue Roofs become an essential part of the hard infrastructure that can flush out salinity and maintain moisture levels in the soft systems.
A Graduated Edge
On the edge of the island, three interrelated high-performance systems are constructed to block higher sea levels and mitigate storm surge force and flooding: a productive park network, freshwater wetlands, and tidal salt marshes. This continuous layered ecosystem attenuates waves, manages the urban watershed, filters interior surface runoff, enhances biodiversity, and introduces a new system of public green space. The morphology of this graduated edge adapts to the unique urban conditions on the east and west sides of Lower Manhattan.
The Battery Breakwater
At Battery Park, the salt and freshwater marshes weave through a series of breakwater islands and feather into the existing park. These islands, structured with geo-textile tubes and covered with marsh plantings, are strategically placed to dull the force of storm surge. They also create a, new, large natural habitat that supports the Atlantic migratory flyway and recreational opportunities for kayaks and canoes to explore the habitat. A section of the inland park is transformed into a large collect pond that draws water from several Level 2 streets.
A Continually Evolving Urban Ground
This holistic proposal unites harbor ecologies and urban infrastructure to create a flexible and adaptive future for Lower Manhattan. By aligning the advantages of naturally-occurring and engineered systems, this new urban model transforms the city in both performance and experience. Over time, currents, tides, and storms cause an evolution of the morphology of the coastline and the local flora and fauna that it supports. Climate change and increasing population are now challenging us to be an active part of this morphology as well. A rich varying ecological succession is set in motion for generations of New Yorkers to experience. In essence, Manhattan will re-invent itself yet again by developing in tandem with natural systems.
Susannah C. Drake, is principal of the New York based practice dlandstudio as well as professor and Senior Associate of the Institute for Sustainable Design at The Cooper Union for the Advancement of Science and Art.