Valuing natural and built infrastructure for coastal resilience: A case study in Howard Beach, NYC
On October 29, 2012, Hurricane Sandy struck New York City and brought storm surges over 13 feet, causing more than $19 billion in damages to the city. In the wake of the storm, the City of New York asked The Nature Conservancy to prepare a conceptual study on how a mix of natural and built defenses could be implemented in a dense urban area. Given its vulnerability to flooding and sea-level rise, the City asked TNC to evaluate the community of Howard Beach, Queens.
TNC worked with engineering firms CH2MHill and TetraTech to evaluate the multiple benefits of five conceptual alternatives to address resilience in the community of Howard Beach: two natural (green) infrastructure options; two hybrid options ( green and gray); and a conventional built (gray) option. These five alternatives included various combinations of wetlands, mussel beds, berms, uplands, urban street trees, flood gates, and flood walls. We used an ecosystem services framework to evaluate the tradeoffs in each approach. The framework included a partial benefit-transfer economic evaluation to describe recreational and aesthetic value of wetlands, a Habitat Equivalency Analysis to describe cumulative gains in ecosystem services over time, and an assessment of flood damages avoided using HAZUS (natural hazard loss estimation from FEMA).
We determined that the hybrid infrastructure alternatives provide the greatest net benefit to society when compared to all-green or all-gray designs. This study demonstrates that not only do natural defenses contribute to flood protection, they also increase ecological and social resilience with the added benefits of enhancing both the environment and the quality of life in surrounding communities. This effort advances the discussion of tradeoffs in the cost-benefit of hybrid infrastructure solutions for coastal resilience in urban environments.