Flood frequency of the world's largest river has increased fivefold

Flood frequency of the world's largest river has increased fivefold
Inundated house along Solimões River (Central Amazonia) during the record-breaking flood in 2012. Credit: Jochen Schöngart, National Institute for Amazon Research

A recent study of more than 100 years of river level records from the Amazon shows a significant increase in frequency and severity of floods. The scientists' analysis of the potential causes could contribute to more accurate flood prediction for the Amazon Basin.

Water levels of the Amazon River have been recorded daily in Port of Manaus, Brazil since the beginning of the last century. The team used 113 years of level records and found extreme floods and droughts have become more frequent over the last two to three decades.

Their findings show that in the first part of the 20th century, severe floods with water levels exceeding 29 metres—the benchmark for a state of emergency in Manaus City—occurred roughly every 20 years. Now, extreme floods occur on average every four years.

Study lead author, Dr. Jonathan Barichivich, from Universidad Austral de Chile and former Research Fellow from the University of Leeds, said: "Increases of severe droughts in the Amazon have received a lot of attention by researchers. However, what really stands out from this long-term river record is the increase in the frequency and severity of the floods. With a few minor exceptions, there have been extreme floods in the Amazon basin every year from 2009 to 2015."

According to the study, the increased flooding is linked to a strengthening of the Walker circulation—an ocean-powered system of air circulation caused by differences in temperature and pressure over the tropical oceans. This system influences weather patterns and rainfall across the tropics and beyond.

Flood frequency of the world's largest river has increased fivefold
Flooded area in the center of Manaus in 2009. Credit: Jochen Schöngart, National Institute for Amazon Research

Co-author Professor Manuel Gloor, from the School of Geography at Leeds, said: "This dramatic increase in floods is caused by changes in the surrounding seas, particularly the Pacific and Atlantic oceans and how they interact. Due to a strong warming of the Atlantic Ocean and cooling of the Pacific over the same period, we see changes in the so-called Walker circulation, which affects Amazon precipitation.

"The effect is more or less the opposite of what happens during an El Niño event. Instead of causing drought, it results in more convection and heavy rainfall in the central and northern parts of the Amazon basin."

The ultimate underlying cause for the warming of the Atlantic is not entirely clear. However, in addition to natural variability, global warming is at least partially responsible but in an unexpected and indirect way, according to the study.

As a result of greenhouse warming, wind belts in mid to high latitudes in the Southern hemisphere have shifted further south, opening a window for transport of warm Indian ocean waters around the tip of Africa, via the Agulhas current, towards the tropical Atlantic.

Flood frequency of the world's largest river has increased fivefold
Flooded suburb of the city of Itacoatiara (Central Amazon region) in 2009. Credit: Jochen Schöngart, National Institute for Amazon Research

The changes to the Amazon Basin's water cycle have had severe consequences for people and livelihoods in Brazil, Peru, and other Amazonian nations.

Co-author Dr. Jochen Schöngart from the National Institute for Amazon Research in Manaus, has experienced Amazon River floods first-hand. He explained that these extreme flooding events last for many weeks and have disastrous consequences. Flooding can contaminate water supply and spread disease, as well as destroy homes and livelihoods. Economic activities in the floodplains such as agriculture a cattle ranching are strongly affected.

The research indicates that these floods are not over yet. The year 2017, which was not included in the study, again saw water levels rise to over 29 meters. As the tropical Atlantic is expected to continue warming faster than the tropical Pacific over the next few decades scientists expect more of these high . The findings of this study could help predict the probability of flooding extremes in the Amazon in advance and help mitigate the impacts for urban and rural Amazonian populations.


Explore further

Amazonian rainfall increases in wet season

More information: J. Barichivich at Universidad Austral de Chile in Valdivia, Chile el al., "Recent intensification of Amazon flooding extremes driven by strengthened Walker circulation," Science Advances (2018). DOI: 10.1126/sciadv.aat8785 , http://advances.sciencemag.org/content/4/9/eaat8785
Journal information: Science Advances

Citation: Flood frequency of the world's largest river has increased fivefold (2018, September 19) retrieved 17 July 2019 from https://phys.org/news/2018-09-frequency-world-largest-river-fivefold.html
This document is subject to copyright. Apart from any fair dealing for the purpose of private study or research, no part may be reproduced without the written permission. The content is provided for information purposes only.
107 shares

Feedback to editors

User comments

Sep 19, 2018
You sure this isnt due to increased runoff from massive deforestation driven by overpopulation?

Maybe you should recheck your numbers to see if you arent missing a few.

Sep 19, 2018
Will ghost that would be a good guess except that is wrong. What is really going on is global warming heating the surface of the oceans and lofting more water vapor into the air. Course when that air condenses into rain there is more water to dump in the end result is flooding. It's just exactly what you're seeing in Hurricane Florence and hurricane Harvey. In addition, global warming is altering the jet streams around the globe basically slowing down its longitudinal motion. The end results are these massive spiraling rainstorms that never stop until a weather pattern like another low blow or another high-pressure Zone pushes them out or breaks them up.

So basically you're seeing the beginnings of global warming in action. And I say beginning actions because I expect this to get a lot worse 20, 50, 90 and few hundred years and more from
now.

Sep 20, 2018
So forest dying and drought is better? It says global warming ISN'T predicted or expected to cause this, but the demented worshippers jump right on it.

Answer the question:
So forest dying and drought is better?

Sep 20, 2018
Here we are at a very fine dilemma:

Either:

A) Climate scientists are useful and necessary (with or without global warming) and can save lives and money and therefore do not need to recur to any scam to keep their jobs and funding.

OR

B) Climate Science is a scam and these guys only want to get funding for doing nothing.

Your take mates. But if you choose A you better pay attention to what they say. And if you choose B then don't even bother to complain next time any weather phenomenon harms you.

BTW, The Elfstedentocht hasn't been held for already 21 years. Deforestation because of overpopulation in the Netherlands stopping our channels from freezing? ;)


Sep 20, 2018
Will ghost that would be a good guess except that is wrong
... except that frequency and intensity have been decreasing...

"both Northern Hemisphere and overall Global hurricane activity has continued to sink to levels not seen since the 1970s. Even more astounding, when the Southern Hemisphere hurricane data is analyzed to create a global value, we see that Global Hurricane Energy has sunk to 30-year lows, at the least. Since hurricane intensity and detection data is problematic as one goes back in time, when reporting and observing practices were different than today, it is possible that we underestimated global hurricane energy during the 1970s."
https://wattsupwi...0-years/

Sep 20, 2018
Who says climate science is a scam? They're saying the politically motivated exaggerated claims by many scientists in popular media are... exaggerated.

Sep 20, 2018
Oops - hang on. The benchmark for this type is data is the 200-year event. 100 years isn't enough for a definitive flood frequency study. The South Atlantic Water Science Center of the U.S. Geological Survey has been collecting a good bit data on the Amazon. I wonder if they've set the level for the 200-year event...

Be careful about predicting a long-term result based on short-term data. Be careful about blindly equating stage to discharge. I seriously doubt the Amazon river has a simple stage-discharge relation throughout its reach.

I personally think the globe IS warming, just like it has done at least six times before. We weren't there for those events. I'm thinking we'll just have to shut up and hang on for the worst parts, and look forward to re-glaciation up to 10000 years later. One thing's for sure: Humans have never done anything for our planet that did not make it worse, regardless of intent.

Sep 20, 2018
Interesting Topic independently of the Attribution to this Variability.

Sep 21, 2018
You sure this isnt due to increased runoff from massive deforestation driven by overpopulation?

Maybe you should recheck your numbers to see if you arent missing a few.


Now you are on a list for slagging the global warming cabal's propaganda.

Sep 21, 2018
You sure this isnt due to increased runoff from massive deforestation driven by overpopulation? -TGOO

Much of the humidity in the Amazon is from transpiration from vegetation. Research shows that the Amazon kicks off its own rainy season from this effect. http://www.scienc...own-rain
Fewer trees means lower humidity and less rain.

Sep 21, 2018
"The height of the annual flood crest of the Amazon at Iquitos has increased markedly in the last decade. During this same period, there has been greatly increased deforestation in the upper parts of the Amazon watershed in Peru and Ecuador, but no significant changes in regional patterns of precipitation. The change in Amazonian water balance during the last decade appears to be the result of increased runoff due to deforestation. If so, the long-predicted regional climatic and hydrological changes that would be the expected result of Amazonian deforestation may already be beginning." A. H. GENTRY, J. LOPEZ-PARODI
Science 19 Dec 1980:

-1980 vs 2018... what's changed? A credible explanation in 1980 is no longer adequate because AGW is now a thing?

Like I say the above researchers at least have to explain WHY deforestation is no longer adequate.

But then I didnt read the paper, maybe it's in there.

If its NOT then we have to suspect political AGW motivations.

Sep 21, 2018
Will ghost that would be a good guess except that is wrong
... except that frequency and intensity have been decreasing...

"both Northern Hemisphere and overall Global hurricane activity has continued to sink to levels not seen since the 1970s. Even more astounding, when the Southern Hemisphere hurricane data is analyzed to create a global value, we see that Global Hurricane Energy has sunk to 30-year lows, at the least. Since hurricane intensity and detection data is problematic as one goes back in time, when reporting and observing practices were different than today, it is possible that we underestimated global hurricane energy during the 1970s."
https://wattsupwi...0-years/

... and you proceed to post an article from 2009. Yes, there was a minimum around 2010, currently we're at the next maximum.

Sep 22, 2018
ACE is just a sum of the squares of the maximum wind velocity of all tropical storms taken at 6 hour intervals. This makes it very hard to tell the difference between lots of little hurricanes and a few powerful ones. Since climate science suggests that there will be fewer, but stronger, hurricanes, this makes ACE even more worthless. Hurricane data supports climate science in this, so one wonders why ACE was chosen.

I've always thought that if I wanted to become a climate misinformer like Ryan Maue, ACE would be my statistic of choice for hiding what's really happening.

ACE is even more problematic for "weak" hurricanes like Harvey, Florence, and Sandy. Ace would be perfect for hiding the destructive forces of those storms.

As for this article, the paper is open source. Click on the DOI link to read the full paper. The data appears to support the conclusions.

Sep 22, 2018
HAWW...HEE....HAWW...HEEE....So basically you're seeing the beginnings of global warming in action. And I say beginning actions because I expect this to get a lot worse 20, 50, 90 and few hundred years and more from
now.

howhot3...aka...howShat da Turd, brays yet again.
LMAO.
It's patently obvious that snorting methane from the rectum of his False "Profit" Al Gore destroyed that lone neuron he shares with the other Chicken Littles.

Due to a strong warming of the Atlantic Ocean and COOLING OF THE PACIFIC over the same period, we see changes in the so-called Walker circulation, which affects Amazon precipitation.......
The ultimate underlying CAUSE FOR THE WARMING OF THE ATLANTIC IS NOT ENTIRELY CLEAR.

Of course, howShat is too stupid to realize what he's pulling out of his ass is shite.

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more