Many residents and community leaders gathered at the Greenpoint Library and Environmental Education Center to talk about flooding:

  • why flooding is happening more

  • where the water wants to go

  • and what we can do about it

Always good to talk and share insights with neighbors. Water connects us! 😅

Some highlights and slides at end:

Marco: Big Apple > Big Easy

Sara Gronim, from 350 Brooklyn, started with the big picture: there is more moisture in the air because warmer temperatures draw more water up which comes down on us eventually.

It’s why NYC today is officially designated as a “sub-tropical” climate: NOAA made this change in classification in 2020. In fact, Sara shared a visual showing how NYC weather is currently on a path to become like Louisiana by 2080.

Under Us: Ghost Streams

Eymund Diegel, an expert on groundwater forensics and who describes himself as a “CSI Agent” (Creek Scene Investigator), took us back to what was under us before we built the city on top. There are thousands of forgotten streams still running through NYC.

You can see where water used to by training your eyes for visual clues on the street. Example are public parks, schools and even government buildings which were often built on land that was available because it was often wet and used to flood more historically. Another example is larger trees which are thirsty everyday and therefore grow bigger on top of natural ongoing water sources.

He walked us through the evolution of how water moved naturally and now is managed by human-built systems. But as more frequent flooding proves, clearly it has limitations.

Eymund asked us to see and appreciate the vast water network that is buried below us and consider ways to re-connect and even leverage the natural flows so NYC can better live with more water. We saw examples from other cities.

Micro: What Can I Do?

At The City Sponge, we like to get practical. So we try to answer the “what can I do?” question: from inside to outside, from basement to block, from plumbing to policy.

To start, we have to make a slight mental shift…


Most people wait to find their flood solution AFTER it floods. Got to shift that. You always spend more on recovery than you do on prevention. Studies show recovery spending is 13x more expensive than mitigation spending when you factor the true costs.

Also, we need to realize the water table is not high, it’s that we are low. Generally, NYC was built close to sea level. We are on the banks of 540 miles of coastline, with a lot of marsh and streams inland. We are a city of water, really. And everyday it’s here (NYC subways pump out 15M gallons on sunny days).

So our thinking around finding our flooding solution needs to focus less vertical and more horizontal. Less on pushing water to down to sewers and underground water tables as the only way, and more on horizontal water movement and storage. We need to spread it out and slow it down before it hits our streets and sewers and give them time to catch-up.

We discussed different flood solution tactics people can take: from free to expensive, outside and inside.

And appreciate that most people start with a bucket, a fan, and maybe a wet vac. But pretty soon they get to pumps (multiple pumps), apps and alert systems, valves, and they go up from there. We often hear that flooding solutions cost between $5k-$60K for a smaller NYC building - to really deal with it well. But that is still less than recovery spending (especially when it keeps happening).


Whatever you choose, it’s important to ask these questions:

  • Q: how many gallons of water capacity do I need to manage (from roof and ground) in a 1-5 inch storm level?

  • Q: do I have anywhere to hold or SEND the water when it comes?

  • Q: can I use green infrastructure vs just plumbing / sewers?

  • Q: how will my inside plumbing solutions and downspouts work if I install a check valve to block sewer backflow?

  • Q: do I have assets I can use: a flat or slightly sloped roof, an exposed downspout, a yard or patio area?

Also…That Library Does It

The community gathering was hosted by Brooklyn’s Greenpoint Public Library and Environmental Education Center: a great space that actually practices what we were preaching.

So many flood solutions features in this building:

  • a bioswale out front to hold and channel water away from street to plants

  • a large green roof with porous pavement tiles that lets water go down into a 1,500 gallon cistern

  • a demonstration garden on the roof to showcase native plants (they help with flooding too)

They also have an “EcoLab” classroom and an interactive screen inside to see how building uses energy. Found out that this amazing building was funded primarily from the Superfund recovery fund that got area polluters from the past to pay for this upgrade. Super nice.

Want More?

Below are copies of slides shared and ways to contact participants.

Here Are Slides

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