New York City may be sinking under the weight of its skyscrapers | Hacker News Reader

New York City may be sinking under the weight of its skyscrapers

architecturaldigest.com

82 pointsandsoitis63 comments

1-2 millimetres a year, or three quarters of an inch per decade, or two thirds of a foot per century. Not spread evenly among the entire city, some areas sink faster than others. The article seems concerned by how this might impact flooding due to rising seas from climate change; New York has been building a lot of sea walls recently and most seem to be aimed at handling 1-4 feet of sea level increase over the next 50 years. This research indicates a few inches of that capacity is going to be consumed by sinking land.

If... the sinking areas sink at the same rate indefinitely forever. Civil Engineering 101 covers soil compaction as a log function as voids are removed. 1-2mm a year turns to .1-.2 mm/yr after a few years, which turns to.. negligible sinking. The implication that the soil and bedrock are just oozing out from under the city is wholly unsubstantiated.

I understood from a childhood book that the magic making Manhattan possible is that the tallest skyscrapers actually attach to a granite bedrock 30m below ground level.

Is this wrong (damn you "first encyclopaedia for children") or would that imply that somehow the granite bedrock itself is sinking?

The granite bedrock itself can indeed sink/rise, if you add/remove large amounts of weight on top.

https://en.wikipedia.org/wiki/Isostatic_depression

https://en.wikipedia.org/wiki/Isostatic_rebound

As far as I can tell, the entire premise of this article is based on a model, not any empirical measurement of Manhattan actually sinking. The article then tries to distract us from examining its thin thesis too critically by connecting it to the effects of climate change. Besides, isn’t lower Manhattan made of bedrock, not sand?

Nothing to see here, move on.

This is not correct. The sinking is measured, not modeled.

As usual, ignore the article and go straight to the actual paper.[0]

"Geodetic measurements show a mean subsidence rate of 1–2 mm/year across the city that is consistent with regional post-glacial deformation, though we find some areas of significantly greater subsidence rates."

"Much of lower Manhattan lies between 1 and 2 m in elevation above sea level, and measured subsidence from Global Positioning System (GPS) there is 2.1 mm/year (Boretti, 2021)."

[0] https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2022EF00...

This is all based on the authors' estimations, not actual measurements or observations.

The scholars first estimated the cumulative weight of New York’s buildings to be 1.68 trillion pounds, and then calculated the downward pressure these buildings exert on the mixture of clay, sand, and slit that make up most of the ground beneath the city’s streets.

Based on their model, New York experiences a “subsidence rate” (the technical term for sinking) of about one to two millimeters per year on average, though Lower Manhattan, as well as particular areas of Brooklyn and Queens, show a propensity for greater subsidence risk.

Really interesting, How do you do these estimates other than using mathematical models? What kind of measurements do you expect to see?

Land registries have geodesic fixtures in many cities, so geodesists could use them as reference points for construction sites. In German cities, those marks are seen on kerb stones everywhere in the old city centers. They look like a big jeans button (3-4 cm/1" in diameter) with a hole in the center (to let geodesists aim at their centers).

Over couple of decades, such marker would have moved by several cm, relative to such markers in other areas. It would probably be impractical to measure several cm shift over 1-2 km across the river, but fixtures would drift relative to each other, and if there's a trend, it's observable -- geodesists routinely measure the drift between big fixtures in the fields over much bigger distances, and publish updates to their reference coordinates.

See https://en.wikipedia.org/wiki/Survey_marker or (German) https://de.wikipedia.org/wiki/Vermessungspunkt.

They also often are attached to buildings. Partly that’s because high points in the landscape such as church towers are often used for long-distance triangulation, partly because engineers want to track how fast a building sinks relative to its surroundings (such sinkings can be highly local in areas where buildings are built on soft ground or on below-ground sand layers. Bedrock is too far below ground in quite a few locations to build on)

GNSS with ground station assist is capable of measuring changes in elevation within millimeters.

As an example, the US maintains the National Spacial Reference System (NSRS), which is a "consistent coordinate system that defines latitude, longitude, height, scale, gravity, and orientation throughout the United States" with very high accuracy.

https://oceanservice.noaa.gov/facts/nsrs.html

https://earthobservatory.nasa.gov/images/147436/taking-a-mea...

https://pubs.usgs.gov/tm/11d1/tm11-D1.pdf

This is a non-problem for Manhattan, which has bedrock not that far down across the entire island. There are a few spots in Greenwich Village and between City Hall and Canal St where it's necessary to go down maybe 70m to reach bedrock. Everywhere else in Manhattan, it's much closer to the surface. Some of the outer boroughs are on fill, though.

Data for most of the US is available from the USGS.[1]

San Francisco for a while allowed building skyscrapers on friction piles. This bad idea resulted in the Millennium Tower mess.

Miami has far worse problems.[2] They've already had building collapses. The geology there is terrible for heavy construction.

[1] https://www.usgs.gov/centers/geosciences-and-environmental-c...

[2] https://www.the-sun.com/news/3156036/map-miami-building-risk...

I wouldn't use The Sun as a source for anything other than who is the hottest actor/actress of the current day. The building collapse there happened due to a distinct lack of negligence on the part of the owners, not because of the land it was built on.

This bad article just hit the first page of CNN.[1]

[1] https://www.cnn.com/videos/us/2023/05/19/new-york-sinking-st...

I'm surprised to see typos and how simplistic this article is. I'm not a frequent reader, but I would have expected more from architectural digest.

Came here to say the same. Even the subhead reads, "...are causing the city to descending." I've worked in newsrooms and for media companies. Twenty years ago, this kind of thing simply did not happen at a magazine like AD.

color me shocked the quality of content goes down when you cut the budgets to the staff to the levels that any journalism outlet has endured. add on top of that the ever increasing desire to be "first" to report, and the editorial review become nothing. hit post, and "we can edit after", but getting release first if much more important.

"our data indicates overt typographical and/or grammatical errors increase engagement" /s

When I see these errors I assume they've outsourced content creation to non-native speakers. Perhaps this is unfair, but it is my immediate assumption. It could just as easily happen when someone heavily edits their text.

Why would anyone use non-native English speakers? There are plenty of low wage countries where English is the dominant language (e.g. India, Philippines, Kenya, South Africa, Malaysia, Belize, Puerto Rico) or at least very popular (Central Europe).

IMO it's far more likely that they laid off their copy editors in the way that tech companies are so fond of laying off their QA staff.

This is exactly the kind of English usage I see in content produced by some of those countries. Even on packaging, I find these errors. The worst is in adverts for English language education programs.

>A scientific journal suggests that the city’s 1.68 trillion pounds of buildings are causing the city to descend, in some neighborhoods faster than others

I think this is grammatically correct.

Not only that but the article is too speculative. They have no idea if it's sinking or not but according to some model it should be sinking by "this much". Maybe do some calculations and come back? or if you have nothing new to talk about, then do some research and write about it? At this point, it's much better to read the gibberish that GPT is making up. At least, it wouldn't have grammatical mistakes.

Yes, “slit” instead of “silt”.

>> the city’s 1.68 trillion pounds of buildings are causing the city to descending

Imagine proofreading at least the headline.

Even Microsoft Word would catch that.

Not as fast as Jakarta.

Why Indonesia is abandoning its capital city to save it: https://www.aljazeera.com/news/2022/11/9/hldwhyindonesia-is-...

Bangkok has similar issues, but talks of moving the capital over a couple provinces have seemed mostly just talks at this point.

To those skeptical of the calculations and if this is measureable:

1. I bet the modelling took construction sites data, which has been accumulated a long ago. You probably didn't know, but constructors know that big buildings tend to sink by several centimeters during and a bit after construction, and there are data and simple calculation models for that. At least this is what my friends in construction engineering say.

(When I started reading, I expected this to be based on Earth crust models -- there are cases with Scandinavia that rises 1 cm per year because 10K years ago the big think glaciers melted, and pressure on crust lowered a lot -- but seems it's not the case.)

2. Many cities have land fixtures for land lots marking, and geodesic work at construction sites. You must have such fixtures, rough or fine, or you'll end up learning that your wall is projected into the adjacent building by several cm/inches, and you need to adjust the project, or, opposite, with a big gap between them.

So there's geodesic fixtures everywhere in the cities. In Germany, you can see them on kerb stones, like a big jeans button, 3-5 cm (2") wide, with a small hole in the middle as an aim. In other cities they're less pronounced, but they do exist.

3. Geodesists routinely measure the drift of such fixtures, because the ground drifts both with Earth crust alltogether, and locally, and you must know where and how much.

I'm sure such small drift relative to other shores this is measureable over decades. Not sure one can deduct it over a couple of years though, as it's just too much distance vs little drift.

But you can probably measure the drift of a grid of fixtures inside Manhattan itself and notice the trends.

Satellite measurements are not that reliable as many think, as GPS signal has interferences and error margin of a meter, and I speculate thatlocal GPS stations get their coordinates by manual input based on local geodesic fixtures.

Am I missing something, or does 1-2mm/yr doesn't sound... too bad in the grand scheme of things?

Climate change and rising sea levels are probably going to screw us in the city over much more quickly and immediately, no?

A child born today, will see New York City about 6 inches lower by the end of his full natural life.

Its magnitude is roughly about one quarter of the low end predictions for sea level rise, yeah. Not much, but worth factoring in.

Yea its peanuts.

Not as quickly as your politicians are.

I don't know how they even measure such a minute change. I mean they must need reference to compare against a stable point in space. What is that reference and what point of city you compare against that stable reference?

They don't even question that it is sinking. They take that as granted -- sinking 1-2mm according to "sattelite" data. Then they spend the study demonstrating why this is attributable to the weight of the buildings they estimated.

They measured nothing at all. That's how.

This is simply their calculation.

And it's absolutely possible to measure this, see: https://www.thoughtco.com/measuring-plate-motion-1441107 and https://www.youtube.com/watch?v=S1m1tAGbfL4

One thing the article doesn’t mention, If the skyscrapers are applying downward pressure, is the ground underneath getting displaced or is it getting compressed? If it’s getting compressed will it stop sinking at some point?

> New York experiences a “subsidence rate” (the technical term for sinking) of about one to two millimeters per year on average, though Lower Manhattan, as well as particular areas of Brooklyn and Queens, show a propensity for greater subsidence risk. As the authors note in their paper, much of lower Manhattan is currently no more than one to two meters above sea level

So let me get this straight - 1 or 2 mm per year, which is completely measurable.

But, no, they didn't actually go and measure anything, the calculated an estimate?

This isn't real science and should be relegated to the trash until they go out and actually measure something.

"are causing the city to descending"

Is this ChatGPT generated, or are the authors really this bad?

It is the copy editors one ought to excoriate. If they still have any.

ChatGPT would almost certainly do a better job than that

Nothing said about the water table of substance. I find that irritating because alongside weight/mass of buildings, excavation and pilings, is the load bearing capacity of the ground as water tables shift.

Jakarta is (as I understand it) both geotechnical at scale the way london is: the land is sinking because thats what land does sometimes, england in that area tilts, and is continuing to tilt into the north sea and because water table dynamics are involved: if you suck water out, something has to give.

What about NY? How much of this is hydrostatics?

NYC doesn't suck water out of the local water table (wherever it does exist). It's all fed from a absurdly massive and deep reservoir and aqueduct system since the later 1800s.

https://www.dec.ny.gov/docs/water_pdf/nycsystem.pdf

(Though per the above PDF, there is a small section of Queens that uses groundwater)

I've lived across the Hudson river on the New Jersey side for several decades, overlooking the skyline.

It's mindboggling how much the skyline has changed in just past 10-15 years, from uptown to downtown including the abomination condo right next to the Riveside Church.

clickbait bullshit.

Why do we need skyscrapers? Why don't we spread horizontally? When we are spreading horizontally can we ensure that most of the daily commute is within a short radius. If the commute has to be outside of that short radius can we use info highways before actual ones a.k.a work remotely.

Europe does not have skyscrapers so it is possible.

Manhattan is a huge peninsula. The boroughs around it do spread out. But having people together is the essential distinction of a city.

> Manhattan is a huge peninsula

No, it’s an island. You can’t build horizontally on an island very much.

And a rather small one, though not tiny.

That said I was under the impression much of Manhattan island was on top of bedrock. Of course a few hundred billion tons does add weight… but unlike one of our House of Reps members might believe, this will not “tip Manhattan over!

> Europe does not have skyscrapers

There are two dozen in Paris alone, going by the modern definition of a skyscraper being a narrow building at least 150m tall.

People don't realize that Europe has skyscrapers because Europe doesn't knock down the old town tourist area to build them.

Every European city of size has a Central Business District which Americans would call "downtown".

Skyscrapers aren’t that much taller than normal city buildings. Don’t assume a city filled with 30-40 story buildings is particularly different from one that has a handful of actual skyscrapers. Even 20 stories is a freaking huge building and London has 12 50+ story buildings. https://en.wikipedia.org/wiki/List_of_tallest_buildings_and_...

Going horizontally requires ever faster speeds to have similar reach. Walking 3.5 MPH past 100 story buildings is the same as 175 MPH going past densely packed 2 story buildings. That’s why cities go vertical.

20 stories is a skyscraper.

my dad was in commercial construction, and 20 story buildings was the bread-n-butter for the companies he worked at. these were quite explicitly described as NOT skyscrapers.

From Wikipedia:

Modern sources currently define skyscrapers as being at least 100 meters (330 ft)[1] or 150 meters (490 ft)[2] in height, though there is no universally accepted definition, other than being very tall high-rise buildings. Historically, the term first referred to buildings with between 10 and 20 stories when these types of buildings began to be constructed in the 1880s.[3] Skyscrapers may host offices, hotels, residential spaces, and retail spaces.

https://en.wikipedia.org/wiki/Skyscraper

I'd prefer not to destroy the environment unnecessarily, personally.

While I agree that a lot of office space is under-utilised and unnecessary, vertical housing is an enormous boon for urban planning - it's vastly more efficient than urban sprawl (e.g. it's cheaper for local government to provide services), and arguably better for the environment (e.g. making good public transport practical). For many people, it's a better living experience too - I used to live in a bungalow in the suburbs, but once I'd experienced living in a good apartment in the middle of my home city, I decided I'd never go back. Not everyone feels that way, I understand, but if we're want to preserve our valuable land for farming and nature, we need to densify.

> Europe does not have skyscrapers

That's an odd thing to say when we all have the same access to the internet, image search, Google Maps, or Europe itself.

We should never let the facts get in the way of a good rant. Especially if it provides an opportunity to use the phrase "information superhighway."

> Europe does not have skyscrapers so it is possible.

I'll steelman your argument to be "Europe has less skyscrapers than NYC" (which I think is true, IIRC).

If you need to get away with less super tall buildings, you need to spread out the density elsewhere; that is, have medium density everywhere. In US and Canada, we've decided that the suburbs are untouchable, so the only solution is to have super tall buildings in a few areas. That's how you get 30 story apartments literally next to 2 story houses [0]. This is an intentional choice. I think it's the wrong one, but overcoming it is going to take a lot of convincing.

0 - https://www.alamy.com/stock-photo-stock-photo-aerial-view-of...

In US and Canada, we've decided that the suburbs are untouchable

Not in Metro Vancouver! Of buildings >= 500' in height, 7 are in Burnaby, 4 are in Vancouver, and 1 each are in Coquitlam and Surrey; under construction are another 4 in Burnaby, 3 in Vancouver, and 1 in New Westminster. There's a dense urban core surrounded by SFHs and then as soon as you cross the border into the suburbs you suddenly get density again.

People downvoting you, but I think you are unknowingly touching on something interesting. We can get really high density without skyscrapers by building consistently somewhat high. The cores of Paris, Barcelona and Begin all have fairly consistently 4-5 story buildings without much space between them. It's also largely mixed use. I believe that the density of actually higher than many parts of Manhattan like the village or even parts of the upper east side. I think that's often outcome of somewhat central planning though and building up massively where demand is is an easier way to dynamically adjust to emerging needs.

My favorite though is as high and dense as possible and increase the likelihood that many people might even live and work within the same building. Connecting buildings on floors other than the ground floor is also something I'd love to see more of.

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