• SWIM

City Releases Two Important Stormwater Plans

Updated: Oct 13


NYC Stormwater Resiliency Plan


In May 2021, the Mayor’s Office of Climate Resiliency released the NYC Stormwater Resiliency Plan for NYC . The plan, which is mandated by the NYC City Council's 2018 Local Law 172, contains maps of the areas in NYC most vulnerable to increased flooding due to climate change and outlines the City’s long term approach to managing the risks of extreme rain events. The plan and maps are to be updated every 4 years.


According to the New York City Panel on Climate Change, by the end of the 21st century, NYC could experience as much as 25% more annual rainfall. The number of days marked by extreme rain will also markedly increase. On Sept. 1, 2021, between 8:51 and 9:51 p.m., Ida brought down 3.15 inches in Central Park. The City's sewer system is currently able to manage ~1.75 inches of rain per hour. The plan acknowledges that our current infrastructure does not yet have the capacity to manage what we know lies ahead. The task of preparing for extreme storms like those we saw this year from Ida and Henri is daunting. The maps in the plan reflect areas of vulnerability for rain induced flooding as well as sea level rise. We are reviewing and digesting the report in detail and will share further analysis of the stormwater, green infrastructure and CSO related recommendations in the plan after we've met with the teams working on the implementation of the plan in the years ahead.


As we've noted for quite some time now, the plan recognizes that our sewer system upgrade efforts need to be based on future projections for rainfall in our region rather than rainfall data from 2008 and real-time data on the ground. While the City has invested a great deal in stormwater and wastewater system updates and has ongoing programs in the implementation stages now through 2030, the plan provides an important set of goals and guidelines for future investments based on more current projections for rainfall in our region.


The Mayor's Office of Climate Resiliency (MOCR) and NYC DEP will attend SWIM's Fall 2021 public meeting in October to review the plan with us. We'll report back here and in our e-blasts after the meeting. The "New Normal" Report below is a document that we are looking at in tandem with the Stormwater Resiliency Plan. The two documents provide blueprints for how the city will move ahead with adaptations to extreme rain events and other climate change related impacts such as sea level rise, heat island effect and urban flooding ( both inland and coastal).


NYC Extreme Weather Action Plan


In response to the devastating impacts of Ida in NYC, City Hall issued a report titled The New Normal: Combatting Storm-Related Extreme Weather in New York City. The report provides a new blueprint for how NYC will prepare for and respond to extreme weather.


The report was compiled by the Extreme Weather Response Task Force, a top-level convening of senior leaders across City agencies, along with outside experts on climate change and resiliency, and contains a new set of protocols and policies to protect New Yorkers from future storms like Hurricane Ida.


Mayor de Blasio has announced plans to support the report’s recommendations with:

  • $2.1 billion in new funding at the Department of Environmental Protection (DEP); $238 million in accelerated funding for crucial DEP projects;

  • $400 million in new funding for other priority capital projects among key agencies including the Parks Department; Department of Transportation; NYCHA; and the School Construction Authority;

  • and $25 million in expense funding for Fiscal Year 2022

One of the action items in the report calls for advancing legislation for an expansion of the Green Roof Tax Abatement Program. A policy that SWIM has informed since its inception in 2008. Here is a link to the timeline of our sustained stakeholder advocacy effort for the GRTA and here is a link to a recent article we co-authored for the Fall 2021 issue of The Living Architecture Monitor. We've got a meeting with representatives in Albany to discuss the recommended expansion of the program this month and will provide updates on the outcomes in an upcoming blog post.

Highlights of Other action items:

  • Develop and adopt future rainfall intensity projections by mid 2022.

  • Develop and implement a new drainage standard, where hydrologically feasible, using new rainfall intensity projections that account for climate change in the planning and design of future drainage investments, including CSO Long Term Control Plans ,by 2023.

  • Incorporating future rainfall data into the NYC DEP 's drainage planning by the year 2025. DEP's drainage planning will evaluate the proposed sewer system performance for projected rainfall to see if off-line storage systems can be developed as part of the plan.

  • Conduct an assessment (to be completed by the end of 2023 and incorporated into capital planning) of adaptation strategies for sewer outfall points along the shoreline to account for sea level rise.

  • Investing in upgrades to storm sewer outfalls to better support conveyance as sea levels rise.

  • By the end of 2021, DEP will identify 10 at risk neighborhoods for the implementation of cloudburst design strategies in partnership with the Mayor's Office of Climate Resiliency, NYCHA, DOT, and the Parks Dept., which would begin work in the first quarter of 2022 and the first four neighborhoods would be completed by 2025.

  • Update building code to address intense precipitation risks and coastal flooding such as increasing mandatory permeable surface requirements for both new and existing buildings.

We’ll be following the implementation of the various recommendations in the reports very closely as they contain many of the recommendations that SWIM Coalition has advocated for and informed over the years.






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