NYC Cloudburst Resiliency: Transformational Community Adaptation through Strong Partnerships

A 'cloudburst' is a sudden, heavy downpour that can overwhelm sewer systems and result in flash floods. These intense rainfalls are becoming more frequent, disruptive, and damaging in New York City (NYC); devastating residents, destroying homes, and disrupting businesses. On September 1, 2021, Hurricane Ida shattered the record for the highest single-hour rainfall in NYC, set only two weeks earlier by another extreme storm, Tropical Storm Henri. Both storms caused flooding, damaged property, disrupted critical infrastructure, and polluted New York's rivers and Harbor. NYC's Cloudburst Program will protect vulnerable communities, mitigate flood damage, and improve water quality. Historical data measuring which neighborhoods were hit hardest by Hurricane Ida were used to identify cloudburst planning areas, including flood extents with sea level rise, structural damage reports, sewer backups, and social vulnerability index. All the recommended Cloudburst projects are in flood-prone environmental justice areas. This project redefines stormwater management in the built environment by transforming streets, parks, and other open public areas into multi-functional community assets for recreational use and flood mitigation. Stormwater runoff from sidewalks and streets is absorbed by porous parking lanes, bike lanes, or medians and then transferred into redesigned public spaces that safely accommodate flood waters. After a storm has passed and sewers have regained capacity, the water drains back into sewer systems. This project is the first large-scale innovative application of interconnected green infrastructure for cloudburst management. NYC's ultra-dense built environment is congested and presents complex challenges that require meticulous coordination among multiple private and public agencies. Further, the complex drainage network requires careful consideration to maintain gravity flow. These challenges were addressed through interagency partnerships, stakeholder consensus building, sewer system modeling, and developing cost-effective integrated solutions. Cloudburst stormwater management integrates flood-protection solutions into public spaces, instilling a positive public perception of how engineering solutions can complement community goals. Integrating public amenities and open spaces with stormwater management solutions, such as sunken basketball courts, water squares, and playgrounds with subsurface storage, transforms these public spaces into multi-beneficial community assets. Based on recommendations from this project, the city announced $400 million in the construction of Cloudburst Resiliency Projects to better manage intense rainfall events in flood-prone neighborhoods. This presentation will cover: 1) NYC Cloudburst Program Goals 2) Social and Physical Vulnerability Assessment 3) Opportunity Screening and Adaptation Analysis 4) Cloudburst Adaptation Toolbox 5) Social, Economic, and Sustainable Design Considerations.