Texas Flood: New York Questions

Texas flooding on July 4th was national news. Then, NYC got a comparatively small taste of it about 10 days later: subway geysers from only 2 inches of rain. And then NJ got it way worse.

After seeing all that, here are some of our questions from a NYC point of view - and the answers we found with a little time and some digging around.

Q: How much rain water came down?

• Texas: The July 4 flash flooding in Texas saw 7+ inches over 3 hours.

• NYC:  The last time NYC got water like that was two years ago in Sept 2023 when 8 inches dropped in part of NYC. (NOAA) 

Q: What have been the closest similar storms in NYC?

Everyone thinks of Sandy, even though there have been others since then.

Sandy was devastating but actually dropped only about 1 inch of rain in NYC.

It was the high tide and storm surge that made the Sandy flooding so bad, and then the rain that fell on top had nowhere to go.

Since Sandy, NYC has seen a few bigger rain storms:

• Elsa (July 2021): peak rates of 1.35 inches per hour.

• Henri (Aug 2021): Set city hourly rainfall records with 1.94 inches per hour.

• Ida (Sept 2021): 3.15 inches in a single hour which made it a "1000-year storm."

• Ophelia (Sept 2023): As much as 8.65 inches of rainfall falling during a 24-hour period!

Q: How often do “1 in 100 year” storms actually appear?

Below is a great map that shows rain fall in bigger storms like “1 in 100 year storms” (= red dot 🔴) over time. Here are two to compare.

1) Sandy 2012 rain:

This map below shows the Sandy timeframe (2012), but notice the red-dots were actually south of NYC. Means we didn’t get as much rain as they did south of us.

2) “100 year rain storms” during 6 Months in 2024:

These size of storms happen more often than you may realize, but depends on where you live.

Look at the red dots appearing on the map over time. This map shows where and how often these bigger rainstorms storms occur nationally…and this is just in the last 6 months of 2024 (June-Dec).

In NY State, storms previously considered “once-in-100-year” events have happened nearly twice as often as expected in recent years (according to State government: NY State Climate Impacts Assessment).

The point is: “1 in 100 year” storms occur WAY more often than 1 in 100 years, just not always where you are. Warming air is holding more moisture so more are on the way.

Q: When are the worst times in NYC for cloudburst storms?

In the fall season, so says the New York State Energy Research and Development Authority (NYSERDA) who assembled more than 250 New York–based, national, and Indigenous climate science experts and representatives from diverse communities and industries across the state to contribute to this assessment.

And it makes sense when you look at the list of biggest NYC rain storms above.

Q: How to think about Texas vs New York City?

Besides the amount of water itself, there are two ways to look at it:

1) Tigger Mechanisms:

• Texas saw river-basin-driven surges amplified by stalled moisture and terrain.

• NYC’s are surface-level floods triggered by heavy downpours over impermeable concrete and/or coastal floods. When we get both, they are compounded.

2) Outcomes:

• Texas floods were exacerbated by rapidly swelling rivers.

• In NYC, we have rivers and over 500 miles of coastline, as well as a lot of underground streams, marsh, springs that have been paved over or filled in over time (…but they are still down there and can make flooding worse). Great map of underground water that is searchable by address from Field Form.

Q: Is NYC preparing for coastal / river surges like in Texas?

Short answer: yes. A lot.

NYC is building protective walls and gates as much as 24 feet high in certain spots. It is massively complex, expensive… and interesting.

At a recent public feedback forum in lower Manhattan, the city showed some detailed plans for this multi-billion dollar work that is already underway around lower Manhattan. A couple of City Sponge IG postcards and notes from that event:

You can see more here: FiDi Seaport Climate Resilience Plan.

Q: Where would people in NYC go if Texas-like flooding occurred here?

It sounds like science fiction, but it’s not. If the city says evacuate, that’s the deal. But not by car.

Can you imagine millions of people trying to leave NYC all at once? The traffic would quickly create grid-lock making roads impassable. Then people would abandon cars.

The city does have an extensive shelter network in many locations and aligned with evacuation plans which enabled by mass transit. They are in lots of places and you should know the closest to you:

If the city were to call for evacuation, City Emergency Management says:

• “Leave early. If you rely on elevators to get out of your building. Elevators may be out of service and may not be available at all times.

• Avoid cars: Reduces the volume of traffic.  Flooding may force the early closure of roads, bridges, and tunnels.

• Plan to use mass transit. Note: Public transportation may shut down hours before the storm.”

• The City Sponge says: Assume a lot of walking as we have seen in blackouts and post 9-11. And bring your “Go Bag”…cause it’s time to go.

Q: What has NYC tried to do since major flooding from Hurricane Sandy and are we making progress on that?

NYC Comptroller Lander’s team did a great report on this comparing what was said was needed and what is being done.

The short answer is: there is some progress, but not enough given weather predictions.

That’s what NYC Comptroller Brad Lander has found after a late 2024 review where his office looked at a number of specific items, their status, and highlighting specific areas where the city set goals for flooding, took action and what progress has been made.

Summary table below. Green is good. Orange is eeeh to okay. Red is bad. 

More on that here.

Q: Were people in Texas alerted in time?

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Q: What is the alert system here in NYC?

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Q: What did we learn about “flood risk zones?”

In Texas, some of the areas affected were “outside” the FEMA flood map (and some like the Camps were apparently in “flood zones” but then lobbied to be excluded as it probably was to lower their insurance costs).

In NYC, during 2023 Ophelia: “Over half of flooded buildings were outside of any mapped flood risk scenarios” according to NYC Emergency Mgmt damage analysis report on Ida.

Q: How many people in affected?

A: 6 Million.

“Six million people there remain under flood watches until Sunday afternoon or evening. An additional two to four inches of rain are possible across the Hill Country, with pockets of up to 10 inches, and excess runoff may cause flash flooding in low-lying areas.” NYT

Q: Why did it get so bad?

A: Warming air, more moisture, infrastructure not set up to handle it.

“Warm air holds more moisture than cool air, and as temperatures rise, storms can produce bigger downpours. When met on the ground with outdated infrastructure or inadequate warning systems, the results can be catastrophic.”