Living Above the Street

Flooding and sea level rise are threatening the integrity of New York City’s historic waterfront built environment. Responding to flood risk, New York City’s Post-Sandy flood policy framework (Building and Zoning Codes) requires the gradual elevation of all habitable spaces of structures within the 1% floodplain to above the DFE (Design Flood Elevation), which has in turn caused various uncontrolled streetscape changes in the city’s waterfront neighborhoods. While historic preservation considerations have been to a considerable extent left out of the city’s flood adaptation policy framework, the streetscape of waterfront historic districts are at high stake under both flood risk and potential adaptation intervention. Aiming at the policy—design nexus of the flood adaptation of historic streetscapes in New York City, this thesis reviewed key flood retrofitting design guidelines, regulations, and built cases in recent years across the United States, and explored a “streetscape-sensitive flood retrofitting toolbox” on single building and street/neighborhood scale that addresses streetscape mitigation and historic preservation considerations for the flood adaptation of historic properties. Based on an analysis of historic streetscape’s significance and tradeoffs between the multiple, conflicting values involved in its flood adaptation, under the concept of “Adaptive Streetscape,” the author established a set of semi-quantitative metrics that evaluates the quality of historic streetscape and its change under flood adaptation, characterized New York City’s flood-threatened historic neighborhoods, and applied the retrofitting toolbox on New York City’s historic built environment through two street-scaled design studies in South Street Seaport and East Harlem historic districts. Summarizing findings that emerged throughout the research process, the author advocated for a paradigm shift of the preservation enterprise towards adaptation through incremental policy reform, put forward the planning—design—review process and recommended practices in the flood adaptation of historic streetscapes, and put forth policy reform and policy-making agendas with key Federal/local institutional actors identified.