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What 1 Inch Of Rain Can Do
Postcards from Gowanus.
Amazing what less than 1 inch of rain water can do in NYC in a short period of time.
It’s sunny in Brooklyn right now, with some thunderstorms predicted for later. But just two days ago, on Memorial Day (May 2024), we had another “cloudburst” event. After being alerted that there would be a severe thunderstorm, I ventured out that day to see if there would be any local flooding impact in my area of South Brooklyn. Quite a bit (see below).
A few flooding “postcards” from South Brooklyn below:
And as it turned out, less than 1 inch of rain (0.83 inches) fell in the South Brooklyn area, according to the National Weather Service. That surprised me given what felt like a real drenching.
But when you see what 1 inch of rain can do, you get why the city alert systems were warning people.
The reality is that 1 inch can add up quickly in NYC and feel like a lot more than an inch when the runoff has fewer places to go. The sewers just cannot handle it all, and when they back up, it ends up coming into our living spaces, basements, subways and streets and also as direct raw sewage discharged into the canals, beaches, oceans.
I shouldn’t be surprised by what I saw….it happens about 40 times a year, according to the Gowanus Canal Conservancy (GCC), an organization at the forefront of policy, infrastructure projects, and climate justice for people who work and live in the South Brooklyn area.
Per the GCC: ”Combined Sewer Overflows (CSOs ) are the greatest source of ongoing pollution to the Gowanus Canal. The overloaded sewer system currently discharges about 363 million gallons of raw sewage and polluted run-off, or combined sewer overflow (CSO), into the Gowanus Canal each year, spread over about 40 rainfall events.”
This is why the city, under the DEP, is spending $114m just in the Gowanus area on new systems for stormwater management (one of many DEP cloudburt projects).
I actually came across part of the plan as I followed the stormwater flowing downhill that day. Eventually, the water lead me to this spot at 2nd Ave and 5th St.
The City Sponge: rain greets new CSO facility location
Hanging on the ubiquitous green construction walls, there was a sign that showed a mysterious looking building - which could be from a Sci Fi movie - but with happy dry people around it. (Note: As NYC construction signs go, this one was actually clear, and had a web site for more info.)
The City Sponge: space-age new CSO facility in Gowanus
This location is where one of two new Combined Sewer Overflow (CSO) facilities will be built in Gowanus area:
Location 1 “Head End Site” near Thomas Green Playground.
Location 2 “Owls Head Site” near 6th Street and 2nd Ave.
Q: Will these new CSO facilities in Gowanus fix the area flooding problem?
A: Not alone, they are PART of a wider strategy.
Given the amount of stormwater we will be getting, the city can’t just build bigger pipes fast enough to deal with it all. So it needs a ”layered approach” where the CSO facilities help treat more stormwater, but water also needs to be diverted and held in other places BEFORE it hits the sewers.
Source: DEP “Forth on Fourth” May 24
That is why green infrastructure projects are so important (rain barrels, gardens, green roofs….think spongey cities). The city is pushing for more of these and estimates 177 have been implemented so far just in the Gowanus area.
Source: DEP “Forth on Fourth” May 24
While out on my flood tour, I saw a small example of a “green infrastructure” in front of one of the big new buildings in Gowanus. They had a spongey garden area in the front which seemed to be holding a lot water in recent storm. It didn’t prevent a big nearby puddle from forming nearby, it seemed to reduce it, and certainly held some of the street runoff from flowing directly into the canal. Glad to see it and hope to see more.
The City Sponge: stormwater in garden in Gowanus
The City Sponge: puddle with path to rain garden in Gowanus
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In addition to CSO facilities and green infrastructure, building owners need to direct their stormwater runoff AWAY from the sewers, which is why the city passed the new Unified Stormwater Rules (see Where To Point Your Gutters). This is a massive evolution which will happen over time in almost every building in the city, but will take many years.
Q: Are there any flood reduction benefits happening soon in the Gowanus area?
A: Yes, 40% flood reduction by next year in a small area, but will take 9 years for the full impact to be realized.
More specifically, the DEP estimates that flood reduction in the 4th Ave / Carroll St area (orange area in map below) will get to 40% of what is needed by 2024, and then….9 years later…it will handle 100% of our new water reality.
DEP “Forth on Fourth (Ave)” presentation May 2024.
If you live or work in these mapped areas:
Orange area (priority): that is where flood reduction will be 100% in 9 years.
Purple area: 83% flood reduction in 9 years.
Green area: 19% flood reduction in 9 years.
So, it seems realistic to say that if you live/work in the purple or green areas, you should still expect hundreds of stormwater flooding events in the next 9 years. More needs to be done, by building owners and by the government.
Q: So what do we do in the meantime?
A: Be part of the solution and don’t wait for others to fix it for us.
There are lots of things we can do…and actually that is why this newsletter was started…to help you understand important flooding info, absorb it and get tips.
But maybe at the top of the to-do list is: let’s be realistic.
More water is coming. The city is doing things. Trying to find money and spaces to do big stuff like build protective walls, upgrade sewers, make absorbent parks, encourage water diversion. But it will take time and lots of money. The city and state are changing laws: from flood disclosure to renters/buyers to where runoff goes. And they are trying to do little things at scale, like a free rain barrel program.
Yes more can be done and is needed. But as we increase our attention and needs, we should to support the city on these projects vs just blame the city. It is a huge challenge to retro-fit a big city for changes in climate and our city needs our help.
Meanwhile, we are going to need to do a few things around our own places where we live and work (we will cover more of these in future newsletters).
When water-proofing your place, don’t just think about it as protecting your own safety and property. Sure that is important…but ideally, you can do it in a way that you are:
preventing /diverting water away from your place AND
NOT into the sewers
NOT into your neighbors places
Otherwise, we are just pushing water around. My water is your water and if we just send it somewhere haphazardly, it will feel like we are bailing out our own leaky boats, right next to each other.
Instead of being discouraged by that, I actually see it as opportunity that could bring people together.
Because when you and neighbors are flooded, it is a “truth” that no one can debate and it affects everyone; no matter how you vote. That connects people with a sense of purpose and urgency. That feels like a potential positive in a negative.
It’s amazing what 1 inch of water can do.
Helpful sites:
Gowanus Canal Conservancy overview of the CSO work and important policy background
DEP recent final scope of work
YIMBY article with explained photos of the stages and plans
FloodHelpNY on how to retrofit your place for more water
NYC Green Infrastructure plan and citizen guides
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