With climate change, today's '100-year floods' may happen every three to 20 years: research

With climate change, today's '100-year floods' may happen every three to 20 years: research
An atmospheric image of Hurricane Irene on the U.S. East Coast in August 2011. Image: NOAA

Last August, Hurricane Irene spun through the Caribbean and parts of the eastern United States, leaving widespread wreckage in its wake. The Category 3 storm whipped up water levels, generating storm surges that swept over seawalls and flooded seaside and inland communities. Many hurricane analysts suggested, based on the wide extent of flooding, that Irene was a “100-year event”: a storm that only comes around once in a century.

However, researchers from MIT and Princeton University have found that with , such storms could make landfall far more frequently, causing powerful, devastating storm surges every three to 20 years. The group simulated tens of thousands of storms under different climate conditions, finding that today’s “500-year floods” could, with climate change, occur once every 25 to 240 years. The researchers published their results in the current issue of Nature Climate Change.

MIT postdoc Ning Lin, lead author of the study, says knowing the frequency of storm surges may help urban and coastal planners design seawalls and other protective structures.

“When you design your buildings or dams or structures on the coast, you have to know how high your seawall has to be,” Lin says. “You have to decide whether to build a seawall to prevent being flooded every 20 years.”

Lin collaborated with Kerry Emanuel, the Cecil and Ida Green Professor of Atmospheric Science at MIT, as well as with Michael Oppenheimer and Erik Vanmarcke at Princeton. The group looked at the impact of climate change on storm surges, using New York City as a case study.

To simulate present and future storm activity in the region, the researchers combined four climate models with a specific hurricane model. The combined models generated 45,000 synthetic storms within a 200-kilometer radius of Battery Park, at the southern tip of Manhattan.

They studied each climate model under two scenarios: a “current climate” condition representing 1981 to 2000 and a “future climate” condition reflecting the years 2081 to 2100, a prediction based on the Intergovernmental Panel on Climate Change’s projections of future moderate carbon dioxide output. While there was some variability among the models, the team generally found that the frequency of intense storms would increase due to climate change.

Once they simulated storms in the region, the researchers then simulated the resulting storm surges using three different models, including one used by the National Hurricane Center (NHC). In the days or hours before a hurricane hits land, the NHC uses a storm-surge model to predict the risk and extent of flooding from the impending storm. Such models, however, have not been used to evaluate multiple simulated storms under a scenario of climate change.

Again, the group compared results from multiple models: one from the NHC which simulates storm surges quickly, though coarsely; another model that generates more accurate storm surges, though less efficiently; and a model in between, developed by Lin and her colleagues, that estimates relatively accurate surge floods, relatively quickly.

Today, a “100-year storm” means a surge of about two meters, on average, in New York. Roughly every 500 years, the region experiences towering, three-meter-high surge floods. Both scenarios, Lin notes, would easily top Manhattan’s seawalls, which stand 1.5 meters high.

But with added greenhouse gas emissions, the models found that a two-meter surge flood would instead occur once every three to 20 years; a three-meter flood would occur every 25 to 240 years.

“The highest [surge flood] was 3.2 meters, and this happened in 1821,” Lin says. “That’s the highest water level observed in New York City’s history, which is like a present 500-year event.”

Carol Friedland, an assistant professor of construction management and industrial engineering at Louisiana State University, sees the group’s results as a useful tool to inform coastal design — particularly, she notes, as most buildings are designed with a 60- to 120-year “usable lifespan.”

“The physical damage and economic loss that result from storm surge can be devastating to individuals, businesses, infrastructure and communities,” Friedland says. “For current coastal community planning and design projects, it is essential that the effects of climate change be included in storm-surge predictions.”

Explore further

Venice to suffer fewer storm surges

Journal information: Nature Climate Change

This story is republished courtesy of MIT News (web.mit.edu/newsoffice/), a popular site that covers news about MIT research, innovation and teaching.

Citation: With climate change, today's '100-year floods' may happen every three to 20 years: research (2012, February 13) retrieved 23 August 2019 from https://phys.org/news/2012-02-climate-today-year-years.html
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Feb 13, 2012
The global scientific community on the worldwide scale amounts to there being literally millions of people who have also have kids who will suffer in a climate crisis yet they refuse to join the dozens of climate change protesters in the streets. So the millions of people in the world of science who say a catastrophic climate crisis is upon us, refuse to ACT like its a real crisis. The tragic exaggeration is obvious and this planet lover is happy a crisis was avoided for whatever reason.

Without consensus there isn't a crisis.

Feb 13, 2012
Interesting they didn't use the years 1850-1965. I wonder why not?

Feb 13, 2012
With climate change, today's '100-year floods' may happen every three to 20 years: research

They won't be 100 year floods then, will they?

Looking at the scablands and the western shore of Superior we don't know what a real flood is, anyway.

If you're worried about high water, don't build, or buy, below the high water line. Better yet, move to Colorado, its all down hill from there.

Feb 13, 2012
Scientists are the enemy of environmentalism. You condemn my kids to a CO2 death just to milk your consultant's wet dream and you polluted the planet with your pesticides.

Feb 13, 2012
Scientists are the enemy of environmentalism. You condemn my kids to a CO2 death just to milk your consultant's wet dream and you polluted the planet with your pesticides.

Science and rational thinking are the enemies of environmentalism. Your kids have enough food to eat because of those pesticides which have had NO impact on lifespans or health other than in your fevered delusions and when you have a kid die of atmospheric CO2 I'll eat your hybrid car one piece at a time.

Feb 13, 2012
I like how they combined 4 of their crappy models into one and think it means it's more authoritative than... say, actual data. And they used input from a two decade long period and from a big fat guess about the future from the International Pannel on Catastrophy Caterwauling. People pretend this foolishness is science.

Feb 13, 2012
One of the worst floods on the Merrimack River in MA occurred in the mid 30s.
There is a photo of the Tyngsboro Bridge, made famous in the Simpsons, with river water a few feet below the bridge.

Feb 13, 2012
This topic should not be separated with other factors, like where people build, population density of surrounding regions that can increase water shed, and debris clogging paths of drainage.

Watching the water rise to a 100 year old mark on a stick while ignoring the thousands of parking lots, homes, and roads built upstream that feed the local watershed does not make a 100-year event.

I am agnostic about AGW, I am pretty sure climate change happens and there is plenty of written history since antiquity that shifts in climate has caused dramatic changes in societies.

One way or another we better stop building these flimsy custom crafted boxes of wood and mud (plaster), and jump on the growing band wagon of concrete dome-like structures that are impervious to almost anything except a bunker buster bomb.

Feb 13, 2012
Humans have always preferred to live very near water. It provides a pleasant view, fertile soil and it moderates climate extremes. As more people gain the ability to live and build where they please, more people will live near water. And regular flooding will do progressively more damage. My personal recollection is that 100-year-anythings have always happened more often than once every 100 years. Earth's climatic event never followed a schedule with any punctuality. I can't see the end goal in calling out "diversions" from some mythical norm of climate behavior.

Feb 13, 2012
All this will do is affect insurance rates. Anyone living in a 100-year flood plain pays a premium for flood insurance. It will soon be nearly impossible to pay for insurance in these areas

Speaking of 100-year flood plains: the name is a bit of a misnomer. No scientist will claim to be able to predict exactly when a flood can occur. The name is supposed to be code for "floods happen here often in the grand scheme of things". As someone mentioned, it's quite common for floods to happen several times per 100 years in a 100-year flood plain... so I'm not sure what this article is trying to prove

Feb 13, 2012
@Sean_W, read about statistical ensembles, blending many inferior models does produce better results than relying on one single model, although, why would you bother, when you've got a prejudice to nurse.

Feb 13, 2012
@qmurphy: Garbage in, garbage out, nothing more needs to be said.

Feb 13, 2012
Since CAGW has been going on for a while (according to the postnormalists), we should already see this trend, right? This research has been done, and the IPCC confirmed theres no signal in actual hurrican data.So whatever their models say, data has already falsified it, so they should build some new models (hint: CO2, not that important guys).

Feb 13, 2012
In fairness to the MIT team, they have simply used the IPCC alarmist predictions as assumed values for the 2080-2100 climate, so possilby this research is a good representation of hurricane activity in a science-fiction sense, sort of like modeling what would happen if Niburu passed through the solar system.

Feb 14, 2012
IMO the main source of global warming is of geothermal origin, but the people are contributing to droughts with excessive nucleation of atmosphere with aerosols. The global warming will increase the temperature gradient across atmosphere, which will switch the horizontal circulation into vertical one. As the result, the inland areas will suffer cold winters and droughts, whereas the coastal areas will collect most of water evaporated from oceans. This would make the weather unstable. For example, the recent freezes and snow blizzards were caused with broken Arctic circulation, which created a pocket of cold air above Siberia. Most of oceanic water condensed and fall down around Alaska coast in form of heavy snow at small area.

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