Claim: Odds of storm waters overflowing Manhattan seawall up 20-fold, new study shows

I think I know a practical reason for this, which I’ll cover in a post later, but I’d like readers to weigh in first.

From AGU:

Newfound rise of storm tides by almost a foot since 1844 adds to risk from sea-level rise

WASHINGTON, D.C. — Maximum water levels in New York harbor during major storms have risen by nearly two and a half feet since the mid-1800s, making the chances of water overtopping the Manhattan seawall now at least 20 times greater than they were 170 years ago, according to a new study. Whereas sea-level rise, which is occurring globally, has raised water levels along New York harbor by nearly a foot and a half since the mid-19th century, the research shows that the maximum height of the city’s “once-in-10-years” storm tide has grown additionally by almost a foot in that same period.

The newly recognized storm-tide increase means that New York is at risk of more frequent and extensive flooding than was expected due to sea-level rise alone, said Stefan Talke, an assistant professor of civil and environmental engineering at Portland State University in Portland, Ore. He is lead author of the new study accepted for publication in Geophysical Research Letters, a journal of the American Geophysical Union. The research also confirms that the New York harbor storm tide produced by Hurricane Sandy was the largest since at least 1821.

water level data

Tide gauge data analyzed in the study show that a major, “10-year” storm hitting New York City today causes bigger storm tides and potentially more damage than the identical storm would have in the mid-1800s. Specifically, Talke explained, there’s a 10 percent chance today that, in any given year, a storm tide in New York harbor will reach a maximum height of nearly two meters (about six and a half feet), the so-called “10-year storm.” In the mid-19th century, however, that maximum height was about 1.7 meters (about 5.6 feet), or nearly a foot lower than it is today, according to tide gauge data going back to 1844, he noted.

“What we are finding is that the 10-year storm tide of your great-, great-grandparents is not the same as the 10-year storm tide of today,” Talke said.

To get the data used in the study, Talke and a graduate student photographed hundreds of pages of handwritten hourly and daily tide gauge data going back to 1844 that is stored at the U.S. National Archives in College Park, Md. Back in Portland, Talke and his students entered the data into spreadsheets and adjusted the data where points were erroneous or missing, including using newspaper accounts of big storms to fill in some of the holes. The researchers then analyzed the data to calculate storm tide levels and look for trends, and compared the information with climate data.

The storm tide is the amount that water levels rise during a storm. It includes both the storm surge – the abnormal rise in water generated by the storm above the sea level – and the predicted astronomical tide. The rise in storm tide outlined in the recent study is in addition to the .44 meter (1.44 foot) rise in local sea level that has occurred since the mid-19th century in New York harbor.

Combining the newly calculated rise in storm tide with the rise in sea level that has taken place since the mid-1800s, the researchers found that today, waters can be expected to overtop the lower Manhattan seawall – 1.75 meters (5.74 feet) high — once every four to five years. In the 19th century, when both sea levels and storm tides were lower, water was expected to overtop the Manhattan seawall only once every 100 to 400 years, according to the paper.

tide graphic

Scientists have studied the question of increasing storm tides in the area before, but none have gone back as far as the current study, Talke said. Hourly storm tide records for New York harbor that are kept by federal agencies, like NOAA, only go back to the 1920s, he said.

In the paper, Talke and his colleagues suggest that the variability in storm tides in New York harbor over the past 170 years could be a result of multiple factors. About half of long-term change could be attributed to decades-long variations in the North Atlantic Oscillation, an irregular fluctuation of atmospheric pressure over the North Atlantic Ocean that has a strong effect on winter weather in Europe, Greenland, northeastern North America, North Africa, and northern Asia.

Longer-term trends could also be influencing the increase in storm tides over the past two centuries, according to the paper. The authors speculate that climate change and increasing global temperatures could be contributing to the increase in storm tides. There could also be local factors, like deepening of shipping channels around New York harbor, that could have affected storm tides in the area over the past 170 years, Talke said.

tide data

The study’s findings may indicate that “storm surges’ interaction with New York harbor has gotten larger so that in addition to sea level rise, the storm surges may have been enhanced,” said Chris Zervas, a scientist at NOAA’s Center for Operational Oceanographic Products and Services in Silver Spring, Md., who was not involved in the study. “For the latter part of the 1900s, [it shows] that the possibility of overtopping the seawall has increased quite a bit in addition” to sea-level rise, he added.

Having this long, continuous set of data enabled the scientists to tease out decades-long cycles and long-term increases that they may not be able to see with shorter data sets, Zervas and Talke said.  Knowing that there has been an increase in storm tides and figuring out why the increase occurred could help scientists better predict what will happen in the coming decades and help cities mitigate future problems, Talke said.

“If it turns out to be a local reason, as has been suggested in some cases, there could be local solutions as well,” Talke said. “In some cases, we may be able to turn back the clock on that a bit.”

notebook sketch




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“Adjusted?” “Filled in?” Use the data you do have, and get back to us. Even a press release not specifying the effect of created “data” on their results is so very far from good science. How would the results have changed without using numbers they did not have? What a travesty…


that’ll be subsidence then….and all their wailing and shrieking is blind faith.


There is just not enough information. I know the effects of man made flood dangers, by poor dredging (see Britain 2014), having flood control (dikes etc) when at one time seawater would flood wetlands and then recede. This is not to me as a Dutchman a very well written or well based report , but what the heck there just as many people to scare to hell out off in the greater NY area as in all of Holland.


I don’t see much to get worked up about. These days I’m a bit more suspect of “adjustments” to data, but it isn’t anything new or restricted to climate science. And they do use the term “speculate” when discussing links to changing climate, which I think is fair.
Bottom line, between rising sea levels, subsidence, human changes (dredging & filling) and other factors, the risks associated with storm surges to NYC appears to be increasing. That’s good to know. Tells me NYC would be prudent to build higher sea walls and toughen up their infrastructure to flooding. Doesn’t tell me a thing about climate change.

Does this mean the West Side Highway will be under water?

timothy sorenson

One nice caveat is that the ‘once every 4 to 5 years’ will be quickly put to the test. Aside it was nice to see that they went back and reviewed records and used data rather than run a model!


The rivers flowing into the harbors and bays of Manhattan bring down tons of silt each year causing a raising of the seafloors and the shallowing is causing waves to be higher with the same back pressure as is seen from winds equal to 150 years ago. More dredging would likely correct some of this. I wonder which “wonder model” these green geniuses used this time?


No valid reference datum (i.e. floating comparison).
How many times was the pier-post with the tacked-on-ruler adjusted since mid-1800s or did it just ‘sink’ in the mud as the barnacles grew and added weight !
Epoch fail.
Ha ha

Seems they are not sure if the elevator is going up, or the shaft is going down.


Once again, cherry-picking and “filling-in-the-blanks” to get what they want, GRANT MONEY for more studies.
When was the seawall last rebuilt, or is it original?
Seattle is currently rebuilding their seawall, with no apparent height increase to compensate for the “rising seas” attributed to CAGW.


Anyone else old enough to remember the Gilligan’s Island episode when the Professor thought the island was sinking, but it turned out that Gilligan was moving the Professor’s measuring sticks?

@krs – it was on last night on METV. 😉

David in Cal

Whatever the cause, if flooding is likely, then local steps, such as dikes and protecting the subway system, should be taken

Adam Gallon

My thoughts are what changed have there been downstream of NY’s harbour? Was there low-lying land that stormsurges flooded, that are now concrete walls & wharfs, thus funnelling water higher up into the harbour?


The east coast subsidence is well documented. Build up the sea walls as the piers were in the 1930 s. You are behind schedule.

Most of Manhattan’s current sea front proprty is man-made land fill, consisting of anything at hand, including abandoned hulks and garbage. That such 19th century expedients are now subsiding shouldn’t surprise anyone.

James at 48

Relatively small sample size, major city built on hodge podge of metamorphic bedrock interleaved with Quarternary and Pleistocene poorly consolidated moraine / moraine outwash / alluvium with all the attendant excavations, tunnels and other disruptions, plus, the well known innate sea level rise due to the long tail of the Great Melt, plus, the innate tectonic subsidence of a Passive Margin slowly moving outward from the mid oceanic spreading center.

David Ball

krs says:
April 23, 2014 at 9:53 am
“Gilligan’s Island. Those poor people,….” – Mathesar


I actually like the idea of at least getting the available tidal data in a usable form. I think notions of local changes in the sea floor from dredging and silting deserve careful attention. Bottom line, how many feet do you need to add to the seawall to establish an acceptable risk? I was reading a little while ago about how the Dutch have reassessed their seawalls and because of potential losses are adding to their flood barriers – not because of Climate Change but the increased wealth and population they are trying to protect.

a p

It will be worth it if it gets the UN out of the US

Rud Istvan

Self inflicted wounds if true. The entire New York Habour area has been changing due to landfill and siltation. Both will change the height of storm tides at a specific location. The water has to go somewhere.

Greg Goodman

“…. his students entered the data into spreadsheets and adjusted the data where points were erroneous or missing, including using newspaper accounts of big storms to fill in some of the holes. The researchers then analyzed the data to calculate storm tide levels and look for trends”
OMG more spreadsheet science for beginners.
At least they seem to be looking for other causes that kneejerk attribution to AGW.
I thought subsidence was a significant factor in that region.

Joey B

Makes you wonder why the UN is spending billions in upgrades to their building in Manhattan when it is just going to be inundated.

David Ball

One gets the impression that people would be up to speed on SLR if only they read WUWUT?


1. Are they still dredging the rivers and channels like they used to or is that now bad and not done anymore because of ecological reasons?
2. A lot of time islands and ports expand by just shoving earth out and building on it. That will subside with time. I’m guessing a certain amount of the area expanded that way.
3. What changes have happened in the over all water flow and distribution over the last 200 years? You can’t just change how water flows without consequences. You have to adapt to your changes.

Tim Obrien

Has anyone taken into account the elastic movement from adding billions and billions of pounds of steel, buildings and people there over the last century?


This is what infrastructure spending is all about: adapting to future needs. This soundsl like at most a call pointing out the obvious.


Degrading Ekman transport. The sinking of land south of New York City (they probably should read Nature or Populat Mechanics.. The newly discovered “rising Greenland” effect. Since Ekman effect makes the center of the atlantic a few feet higher in mid-atlantic than eastern seaboard, and fact that the land is actually sinking….

Charlie A

How long has the Lower Manhattan seawall been there? Is it original or something built on filled land?


When I read these kind of alarmist rising sea level perils, I think about a 1965 Gilligan’s Island episode (season 2, episode 6, title: Quick Before It Sinks). The Professor was measuring the tide levels in their tropical lagoon with bamboo sticks as tide gauges. He became very agitated and alarmed when he realized his “data” from his tide gauge sticks showed their island paradise was rapidly sinking. He proposed all sorts of radical solutions from Arks to building the huts on higher ground in the middle of the night so as not to frighten the women. Only at the end did the Professor realize it was Gilligan who was moving his sticks into deeper water for his crab trap anchors.
Lesson: Professors are easily fooled by their data and preconceived interpretations. The alternative explanation that the sticks were being surreptitiously moved by a 3rd party never occurred to him.

Water Street had its name from something, though I’m sure nobody knows what now. Surely it’s several feet under the river now, given the accelerating sea-level rise since 1900.


If they don’t account for glacial isostatic adjustment (land is like little see-saw with north of new york rising and south sinking) and the don’t account for the Sargasso Sea level changes, it’s worthless.


With regard specifically to NYC storms, did the authors also “adjust” for the increase in paved-over land over the metro area, that is, soil no longer available to absorb storm/rain runoff?


Wasn’t this lower Manhattan next to the river built on landfill?

Also, if the Manhattanoids care about their land, they can build a taller seawall (or simply pay higher flood insurance rates). Or maybe they can choose to live more than 6ft above seal level so they avoid the problem entirely. Venice is sinking pretty rapidly (relatively, at least compared with Manhattan) & it still has quite a lot of undrowned people in it. Almost as if there was some mysterious mechanism built into (most*) life forms that stopped them from just standing around gape-mouthed whilst the waters lapped over their heads.


“There could also be local factors, like deepening of shipping channels around New York harbor, that could have affected storm tides in the area over the past 170 years, Talke said.
could have? This is THE MAIN REASON.

So a trace chemical causes oceans to rise even though there is no proof of that, and the statue of liberty will soon have a bath? NO end to the state financed stupidity of this cult

Dave Wendt
Gyre-scale atmospheric pressure variations and their relation to 19th and 20th century sea level rise
Laury Miller1 and Bruce C. Douglas2
Most of the long tide gauge records in the North Atlantic and North Pacific commonly used to estimate global sea level rise and acceleration display a marked difference in behavior in the late 1800’s – early 1900’s compared to the latter half of the 20th century. The rates of sea level rise tend to be lower in the 19th compared to 20th century. We show this behavior may be related to long-term, gyre-scale surface pressure variations similar to those associated with the Northern Annular Mode. As sea level pressure increases (decreases) at decadal and longer timescales at the centers of the subtropical atmospheric gyres, sea level trends along the eastern margins in each ocean basin decrease (increase). This is not an isostatic response; the scaling between local surface pressure and sea level at interannual and longer timescales is 3 to 6 times greater than expected by that mechanism. Rather, it appears to be the result of large, possibly gyre-scale changes in ocean circulation. Some evidence is also presented indicating slow, ∼2 cm/sec, westward propagation of sea level changes in the Atlantic from the west coast of Europe to the east coast of the U.S. which produce the decadal variability seen there.
The gyre-scale circulation of the North Atlantic and sea level at Brest
P. L. Woodworth1, N. Pouvreau2, and G. Woppelmann3
“In this paper, we present a similar analysis for the North
Atlantic to that of Miller and Douglas (2007), but use sea
level and air pressure records twice as long as those used
previously. The research has been made possible through
an immense amount of recent “data archaeology”, wherein
valuable historical records have been rediscovered and their
data converted into computer form and quality controlled.”…
“. However, if the Miller and Douglas (2007) interpretation is on the right lines, then the sea level rise (fall) observed on the eastern boundary will be primarily a consequence of the spin down (up) re- sponse of the gyre to changes in wind stress curl. It follows that it will not then be related primarily to the changes in sea level that occur due to variations in ocean volume, although of course the different contributions to sea level change could be related indirectly through various climate forcings….
“It is certainly the case that the redistribution of water needs to be considered alongside the many factors responsible for ocean volume change on multi-decadal and century timescales that are included in periodic assessments such as that of Bindoff et al. (2007).”


Tide data contains three components: periodic, secular, and episodic.
The periodic data can be easily identified with a Fourier analysis. It will have components related to the phase of the moon and to the time of day (phase of the sun). because of the celestial mechanics of the orbits on the earth and moon, this will repeat itself almost exactly every 54 years and 33 days (19,756 days equals 669 synodic months equals 717 anomalistic months).
Removing this contribution will leave the monotonic secular trend (the VERY long range changes in sea level, averaged over the entire span of the data) and the episodic component due to short-term random variability (such as storms).
This kind of analysis applied to tidal records for the Atlantic coast should also reveal historical data regarding the Atlantic Multidecadal Oscillation.

Rud Istvan says:
April 23, 2014 at 10:12 am
LamontT says:
April 23, 2014 at 10:23 am
Stark Dickflüssig says:
April 23, 2014 at 10:37 am
Charlie A says:
April 23, 2014 at 10:33 am
kenw says:
April 23, 2014 at 11:11 am
JDN says:
April 23, 2014 at 11:06 am
Several writers have asked about the original shoreline across the south tip of Manhattan, others about the fill and dredging that has gone on.
Above link is to a reliable map showing why this simplistic effort is doomed to merely re-create hysteria and hype. Which IS, after all, its intended purpose.
But, land movement MUST be specifically and explicitly accounted for: With the baseline elevation, and the continued re-calibration of alignment of that baseline established. Where is Zero?
Where WAS Zero, and at what time was “Zero” established ?
How has the land moved with respect to that “Zero”?
How has Sea level moved with respect to “Zero”?

john robertson

Upon this infilled estuary We will build a city?
The management of this papers data duplicates the human management of the harbour.
I wonder what sea level rise would result from tossing the UN buildings and staff into the East River?


john robertson says:
April 23, 2014 at 12:05 pm
I wonder what sea level rise would result from tossing the UN buildings and staff into the East River?
Zero. As they are unnatural, water shall surely reject them. The Standard Test for Witchcraft states this plainly..

Robert W Turner

They actually claimed we should see the sea wall breeched every 4-5 years. If 10 years from now a storm surge doesn’t breech the wall what will the excuses be? WUWT already has a list of things CAGW causes, now how about starting a list of excuses for failed predictions.

Barclay E MacDonald

Nice job everyone! It didn’t take long for those posting here to see the problem, even without the help of “Major Domo”:))
It is amazing that they never considered the land holding the tide gauges might move! Perhaps in Portland they are back to Aristotles Geocentric, earth where the natural state of things is at rest.

Physics Major

I seem to recall reading that there used to be large oyster reefs in New York Harbor and these reefs helped to dissipate the energy of a storm surge. Sadly, the reefs are gone now – oysters on the half-shell are my favorites.


timg56 says:
April 23, 2014 at 9:41 am
Yes. No dissent.
Local or regional effects – which can and should be mitigated.


Hurricane Flashback: The Great New York Storm of 1821
September 3 marks the 190th anniversary of the Hurricane of 1821, which saw flooding and destruction in the growing metropolis. In less than an hour a thirteen-foot storm surge deluged the city, swallowing everything below Canal Street. The Battery was particularly devastated, docks were destroyed, and ships were swept onto streets. Further uptown, a bridge that connected Harlem to Ward’s Island was washed away and somewhere in Chinatown, the East River likely met the Hudson. “New Yorkers were lucky,” writes Bruce Parker in The Power of the Sea: Tsunamis, Storm Surges, Rogue Waves, and Our Quest to Predict Disasters. “The hurricane hit at low tide.“


Alarmists are simply inflexible and cowards.
Everything has to stay as it is and any change makes them fear the worst.
Come on guys, man up, get a life.
The sky is not falling all the time. It’s not dangerous out there in the real world.
But I agree, you shouldn’t have kids and grandkids.

Steve Keohane

As others have said they need to account for subsistence and moon phase, as well as compare infilled results to non-infilled results.


Those of us with a bit more experience in these matters know the value of marshes, wetlands, tide pools and other such features that have surely been eliminated over time in NYC.
Houston remembers Ike.