Let's Absorb: Ways NYC Can Get Spongier

Hot. Humid. Rain. (Repeat)

This isn’t Florida. It’s the new NYC where the climate is officially “sub-tropical”…and you can feel it.

But while we been sweltering through heat domes and occasional thunderstorms, other places are getting cloudbursts with 5-20 inches of rain which flooded Florida, Texas, Illinois, Iowa, Minnesota, Nebraska, South Dakota and Wisconsin in recent weeks.

SOUTH DAKOTA: “This is probably the first time we’ve seen this kind of rainfall come this quickly,” said the Governor.

FLORIDA: “Looks like the beginning of a zombie movie.”

TEXAS: 11 inches of rain, dams were opened: “that caused the river to shoot up by almost five or six feet overnight.”

Of course, we have seen “smaller” versions of this in NYC, notably last Sept ‘23, when even a few inches of sudden rain wreaked havoc in our heavily cemented city.

NYC: 3 inches of rain: South Williamsburg Brooklyn Sept 2023

Can we solve for situations like these by just making our sewers bigger?

No.

The city is underway with extensive sewer upgrade work to expand its capacity beyond the estimated limit now of 1.75 inches of rainfall an hour. This was covered well here in NY Times story from the Sept ‘23 storm.

But the NYC Mayor’s office cautioned in their “The New Normal” report (2021) that “recalibrating our sewers for storms like Ida” would cost ~$100 Billion and may not keep up with the pace of water that is coming.

So….what to do in the meantime…or in our lifetime?

Yes we have things we should do to protect our buildings and streets, but even bigger sewers and more sump-pumps cannot alone handle the amount of water that we are now starting to see. [ And water seems to be coming from everywhere: from underground, from the neighbors yard, even the dripping air conditioner upstairs! ]

To live with more water, we also have to make the city spongier.

The concept sounds like what it means. Re-building our city to absorb and hold more water vs just fighting it.

In order to protect some places, we also have to give water new places to go…besides our basements, subways, and sewers.

Those places could be what existed before in the natural landscape or be new creative spaces. This is called “green infrastructure” and it is a big part of the NYC’s multi-pronged approach.

You can search and find hundreds of green infrastructure projects already completed or being planned in your area here:

For more on this from a local expert here in NYC, we talked to Wendy Andringa, the Founder and Principal of Assemblage Landscape Architecture.

A bit about Wendy: 

Five Questions The City Sponge posed to Wendy:

1. How do you describe what you do?  

Assemblage works in the creative stormwater realm - we work with teams to design green infrastructure into the urban fabric - it’s the foundation of our work.

2. If the Mayor or Governor could grant you three wishes, what would you ask for?

To really move the needle on flooding, we have to look more aggressively at “depaving” in NYC. The majority of our urban surface is impermeable - the view of NYC by satellite photo is a network of rooftops, sidewalks and streets.

Of course we have areas carved out for parks, which is really important for a multiplicity of reasons, but we must look closer at creative ways to also use our streets and sidewalks to detain and absorb rainwater.

So, my three wishes would be:

1) MORE MICRO-PARKS: I would love to see NYC start a campaign for public and private entities to implement  more “microparks”. This means creating curbside rain gardens, green roofs, and smaller-sized green spaces in the right-of-way that people can enjoy.

2) POLICY AND INCENTIVES FOR GREEN INFRASTRUCTURE: Policy would help: the city could be offering more incentives and bonuses for this to happen. And DOT could be examining our streets even more to find opportunities to carve out more space. For example, in Park Slope, 3rd Street has triple-wide sidewalks that could cede some width for a continuous plant bed under its beautiful street tree canopy. If tree roots have access to rainwater, they can absorb over 13,000 gallons of water in one year!

The problem with our current situation is that trees actually have little access to rainwater that falls on our sidewalks. Most of their roots are beneath paving, so they only take up a fraction of what they could. A continuous street tree “micropark” along 3rd St could absorb so much more rainwater that would otherwise head downhill to Gowanus. 

3) GIVE DESIGNERS AGENCY TO RETHINK THE RELATIONSHIP OF OUR SIDEWALKS TO STREETS: We need to incorporate new curb strategies into street design.  For example, street curbs could have more micro-openings designed for rainwater to pass through them to reach street tree roots underground. The street curb has so much room for innovation - simple changes can benefit our urban forest and also make the city spongier!

3. What is the coolest part of your job or a project you most proud of?

One of our first projects, a Bronx Health Care center, was to mitigate flooding in the building basement with new rain gardens that have been successful in soaking up water from heavy storms. The building staff loves the new gardens too - that's the co-benefit of green infrastructure!

4. What is the hardest part of your job?

I think one of the biggest challenges with green infrastructure innovation is that new solutions take time. Early adopters really have to push against the tide to change the current standards. Changing a curb detail sounds simple, but getting agency approval to modify a standard design detail can be like moving a mountain!

5. How could NYC citizens help?

Urge your elected officials for public to implement more “microparks” in both public and private spaces:

• curbside rain garden

• green roofs

• smaller-sized green spaces in the right-of-way that people can enjoy

Wendy is on the frontlines helping NYC with flooding solutions in ways that leverage nature. The work needs more public support, as she points out.

But its not only in requesting more “microparks” in flooded areas, actually it can even be in little things like… we got a rain garden, who looks after it?

Sounds minor, but the city is concerned about that, too.

At a recent RainproofNYC event in June 2024, hundreds gathered and heard NYC city officials and community leaders talking about the many aspects of the flooding puzzle, but there they also acknowledged that you can’t just create green infrastructure public spaces, you also have to maintain them - or “steward” them (a better word). After all, who cleans the trash out of a curb-side rain garden that the street sweeper cant get to?

Possible candidates might be sanitation, block associations, BID’s? But we need an answer.

And sometimes big ideas hinge on little operational details like this, which can be the difference between a popular attractive green system that absorbs water or a neglected community eyesore that doesn’t.

This need is part of what the RainproofNYC team acknowledges in their working group when they said a key question for flooding is: ”How do we activate existing resources to create, adopt, and own initiatives that will transform New York from a concrete jungle into a sponge?“

The City Sponge POV:

(Putting on an editorial hat here…)

The city is making a lot of effort to highlight and grow green infrastructure. But they need our help.

1) The city could solve the“steward”need by creating entry-level “green jobs” for people from the neighborhoods. Yes it is basic, but on -amping people to green job training is important for many reasons. Or perhaps give grants to block associations to do the ones on their block. This could extend to sewer basins, too.

2) For private spaces, the city could offer incentives for owners to install - and steward (maintain) absorbent spaces on their own property, helping themselves and their neighbors. Not unlike solar or green-roof incentives. This would be especially helpful if property owners felt they could prevent flooding and beautify their property at the same or lower cost than the standard ”cement race”mentality: just building up more cement walls and more impermeable surfaces and pushing water to neighbors (this topic for another newsletter).

3) We hope NYC can:

• Make it easier for people to submit green infrastructure spaces or raise their hands in support of ideas, or steward jobs

• Reduce the approval steps / permitting (don’t make it too hard)

• Provide some money or tax breaks for private owners to do something on land they control

• Create a set of basic “green infrastructure packages” as well as a network of “experts” who can help people decide what to do based on their unique situation, like the state does for health insurance.

The city can only do so much on their own. But they can encourage us - the residents and businesses - to do some small but scaleable steps which helps NYC absorb more water in a way that also looks good. 😅

Helpful Links:

Assemblage Landscape: https://assemblagelandscape.com/

NYC Green Infrastructure Main Page: https://www.nyc.gov/site/dep/water/green-infrastructure.page

NY Times on Sept ‘23 Flooding, Causes and Solutions Considered: www.nytimes.com/2023/09/29/nyregion/nyc-sewer-system-infrastructure.html 

The City on Sept ‘23 Flooding and Lessons From Past: https://www.thecity.nyc/2023/09/29/city-caught-flat-footed-flood-dredges-up-lessons/

Summary of NYC / Copenhagen Partnership on Resilience: https://www.ramboll.com/news/in-good-company-how-new-york-city-and-copenhagen-deliver-climate-adaption-together

RainproofNYC: Coalition of People Working on Flooding Solutions: https://rebuildbydesign.org/rainproof-working-groups/

NPR on China Experiments With Spongier Cities: https://www.npr.org/2023/10/03/1202252103/china-floods-sponge-cities-climate-change