‘We Now Live in a Place Our Infrastructure Was Not Designed For.’
In 2020, the US National Climate Assessment reclassified New York City from the coastal temperate climate zone to the humid subtropical climate zone – a recognition that we now live in a place that our infrastructure was not designed for. We face several types of flooding impacts and risks as a result.
Rising sea levels are creating more frequent tidal flooding, which we have seen particularly, but not exclusively, in the communities around Jamaica Bay. Rising sea levels are also causing groundwater levels to rise, which is exacerbated during heavy storms and periods of long-term rainfall. Of course, this means an increasing risk of coastal inundation. I note that multiple forecasters have indicated that this hurricane season is expected to be more severe than average….
In the 12 years since Hurricane Sandy, New York City has pursued two, complementary kinds of coastal flooding strategies. One is about preventing storm surges from causing flooding; this is what coastal defenses are. The reality is that these major projects – such as East Side Coastal Resiliency (ESCR), Red Hook Coastal Resiliency (RHCR), and the South Shore of Staten Island seawall – are massive, complex projects that take years to design and years to build….
Within two to three years, several of these projects will be complete, and many neighborhoods of New York City will be protected against storm surges. As of now, more than a dozen projects are underway, but none is complete and fully functional. The reality is that this year, if a storm surge hits New York City, there will be flooding.
The good news is that we have also invested huge amounts of money in resilience – which is not about preventing flooding but ensuring that we can withstand and bounce back from it. As we know, 44 New Yorkers lost their lives in Hurricane Sandy, and thousands had property destroyed, but among the storm’s major impacts was the long-term disruption it caused. Because so many buildings had their electrical equipment in the basements, many buildings were without power for weeks, and some – especially at NYCHA – were without elevators for months.
We learned from this and now, happily, our building-level resilience efforts are well advanced. Our power plants and wastewater treatment facilities are better protected. Many buildings – including at many NYCHA facilities – have relocated or hardened their critical equipment. While a flood today would still cause damage, in most cases it would be the kind of damage that disrupts lives for hours, or a day or two, rather than months.
Overall, New York City will have invested more than $18 billion in coastal preparedness in the aftermath of Hurricane Sandy, mostly from Federal funds. Roughly speaking, somewhere between a quarter and a third of that is for building- or site-specific resilience, and the remainder is for large-scale coastal infrastructure. Even with this, the work is far from complete, and… we do not have a dedicated source of funding, either Federal or local, for coastal resilience.
I say this in part because of what we may face this summer, but also because the reality is that our stormwater resilience efforts really started in earnest only two and a half years ago, after Hurricane Ida, whereas our coastal work began 12 and a half years ago, after Sandy. As with coastal resilience, it will take well over a decade for us to see measurable progress in stormwater resilience infrastructure, and it will cost billions and billions of dollars. As with coastal resilience, building-level resilience will be much faster to achieve than infrastructure-level prevention, and the reality is that we will need both.
One key difference is that we expect to pay for most stormwater resilience projects with local funding sources. That is of course both good news and bad news. As New Yorkers, we will be less dependent on State or Federal decisions to shape whether we achieve stormwater resilience, but the bad news is that the more resilience we want, the higher our bills will have to rise….
The heating caused by climate change adds extra moisture to the atmosphere, intensifying storms and making them harder to manage. These massive storms now bring short, extremely intense bouts of rain, which are called cloudburst events. The deluge from cloudburst events can overwhelm stormwater management systems.
For the past century, the New York City stormwater system generally performed sufficiently, capturing rainwater and carrying it to treatment facilities or open waterways. Storm sewer capacity varies around the city, but, at most, it is meant to manage 1.75 inches of rain per hour. Until recently, rain was expected to exceed this intensity only once every five years. In other words, there was a 20 percent chance that a storm would exceed this intensity in a given year.
But now, we are in a subtropical environment, so we see these storms more frequently. Last year was especially wet. New York City experienced rain every three days in 2023, and experienced five storms that exceeded 1.75 inches per hour, as measured at our wastewater resource recovery facilities.
Instead of one “five-year storm” every five years, we had five “five-year storms” in one year.
It is possible that 2023 was an outlier. It may be that the next few years will be somewhat drier, but increasing overall rainfall is consistent with all climate models for the northeastern United States.
The recent New York City Climate Change Vulnerability, Impacts, and Adaptation Study (a collaboration between the city and local scientists) concludes that the “five-year storm” toward the latter half of the century (2050-2099) is expected to be between 2.1 inches and 2.6 inches per hour. We are likely to face more extreme swings, so that we should expect to see more wet years punctuated by drought years. This is exactly what has happened over the last few years. It is easy to forget that, in between the record-breaking storm years of 2021 and 2023, 2022 was a drought year, with very little rain until the late autumn….
The final conclusion I ask you to think about is that this is not just a technocratic decision. DEP alone cannot deliver a stormwater resilience plan for the city. We will need a much broader conversation about how much we are willing to pay, how much flooding we are willing to accept, and what kinds of responsibilities we are willing to impose on homeowners. DEP is the right agency to offer alternatives, but these are fundamentally political questions.
Rohit Aggarwala is the commissioner of the New York City Department of Environmental Protection. This Urban Matters is excerpted from his April 26, 2024 testimony to the New York City Council Committee on Environmental Protection, Resiliency, and Waterfronts.
Photo by: MTA