Why the Mississippi River Floods Should Have Been Expected
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By Richard A. Lovett of Nature magazine
Last year, it was Pakistan and Russia. This spring, all talk of disasters attributable to freak weather conditions turns eyes to the U.S.
First, it was snowfalls that never seemed to end. After that came tornadoes. Now, a massive slug of water is working its way down the Mississippi River, forcing the U.S. Army Corps of Engineers to deliberately flood farmland to spare riverside towns such as Cairo in Illinois, and threatening near-record water levels all the way to New Orleans. Nature looks at the underlying causes of these extreme events, and how the surge might have been predicted. (Scientific American is part of Nature Publishing Group.)
Why did it happen?
The simple answer is because it rained. A lot. Parts of the U.S. Midwest reported rainfalls up to four times the norm in April. And that came on top of a winter that saw some regions receiving unusually high snowfalls.
But that's only part of the answer. For decades, people have been building shopping malls and parking lots that cause water to flow quickly into rivers, rather than soak into the ground. They've built levees that constrict the flow of rivers, forcing water to travel downstream faster. In places, this has been referred to as a "levee war," whereby one town's levees funnels water downstream to become the next town's crisis.
"People don't realize how dramatically humans have altered many of these river systems," says Len Shabman, an economist at Resources for the Future, a think tank in Washington, D.C.
But the much-publicized diversion of water into Missouri farmlands to spare Cairo was actually a success, Shabman adds. "That was always part of the plan," he says. The federal government long ago purchased easements--the right to flood the land--from the farmers who own it, precisely for this purpose. "The farmers may not have remembered they had an easement," Shabman says. "But they were there."
Has anything like this happened before in the U.S.?
Yes. The greatest flood of the twentieth century occurred in 1927, but there were also large floods in 1937, 1973, 1993 and 2008, although only the 1927 flood compared to this year's.
"This is the blessing and curse of farmers in the American Midwest," says Bill Patzert, a climatologist at NASA's Jet Propulsion Laboratory in Pasadena, Calif. "They're blessed with rich farmland and the rivers that irrigate it. The downside is that sometimes they overflow."
Could this have been predicted?
Of course. Large snowfalls and heavy spring rains are a classic formula for flooding. All of the water has to go somewhere.
"By January or February, everybody should have known we were going to have May floods," Patzert says. "To be shocked and awed by these kinds of events is disingenuous. It means you haven't read your history."
But that's only after the snow and rains hit. Forecasting the weather patterns that produced them is still a science of the future.
It may not be so very far away, however. Even before the storms hit, a research group led by Upmanu Lall at Columbia University in New York had been trying to correlate a century's worth of floods in the Midwest to continent-wide weather patterns.
What they found, Lall says, is a surprisingly consistent pattern whereby a pair of high-pressure systems--one over western Texas and another off the U.S. Atlantic coast--conspire to force moisture inland from the Gulf of Mexico "like a funnel."
It is possible, he adds, that these persistent high-pressure zones may be produced by two well-known oceanographic patterns: La Nina and El Nino in the Pacific Ocean (which mark alterations in warmer and cooler conditions between that ocean's eastern and western equatorial waters) and the North Atlantic Oscillation (which results from weather patterns between Iceland and the Azores).
If so, he says, it may someday be possible to predict weather patterns likely to produce flooding in the Midwest, perhaps 30-90 days in advance.
So why were people taken by surprise?
Partly because conditions have changed since 1927. The population has soared and urban development has encroached onto many areas that were once farmland. There are simply a lot more people, and a lot more infrastructure, in harm's way.
Nicholas Pinter, a geologist at Southern Illinois University in Carbondale, who works on flood hydrology, has a word for this: "hydro-amnesia." It causes people to build in places that were flooded a generation ago and will be flooded again a generation hence.
"In 1927, everyone had a boat," Patzert adds. "They knew it was coming. One thing I noticed about this particular flood was that all these people living in harm's way didn't have boats in their backyards."
Did global warming play a part?
Maybe, but not a big one. In Northern Europe, Pinter says, it's clear that global warming is producing bigger floods. But in the Midwestern U.S., the impact is less clear.
Not that this lets us off the hook. A much bigger factor is the degree to which we have altered the rivers. "The river dynamics in no way resembles what it did 200 years ago," Pinter says.
In The Netherlands, Shabman adds, there is an official policy of leaving room for rivers. "In the U.S., we've done the opposite," he says. "Then we're horrified when the inevitable occurs."
This article is reproduced with permission from the magazine Nature. The article was first published on May 13, 2011.
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16 Comments
Add CommentI wonder with what precision and confidence someone like Patzert or other experts can predict flow rates at a given point on the Mississippi.
Reply | Report Abuse | Link to thisSince the myriad effects of land agricultural, industrial and residential land development are difficult to quantify, it's amazing how precise short term forecasts are.
Reply | Report Abuse | Link to thisThe article is right, though, about the dearth of seasonal forecasts. It would seem that the U.S. Army Corps. of Engineers, who are responsible for managing river dynamics, should be charges with at least seasonal forecasting.
Also, I suspect that the short term melting of Northern snow pack plays at least as large a role in determining flood impact as does spring showers...
The link below will show an enhanced Google Map I made of the Lower Mississippi and Atchafalaya river area. The control structures are shown as are the main levees along the Atchafalaya floodway. If the Morganza Control structure is opened, then much of the area between the yellow levee lines is expected to flood. Anyone is welcome to use this map link and pass it along.
Reply | Report Abuse | Link to thisThe “i” symbol (near the upper middle) links to some related information.
To see the detailed topographic maps click Hybrid ==> MyTopo. Then zoom in for more topographic detail.
To turn the symbol labels on/off click Menu ==> Labels On/Off.
http://www.mappingsupport.com/p/gmap4.php?q=https://sites.google.com/site/gmap4files/p/news/mississippi_course_change.txt&ll=30.417887,-91.201416&t=h&z=9&label=on
Joseph Elfelt
Gmap4 author
Redmond, WA
I found a recent news story stating that they'd just opened up one of the Morganza Control structure's 125 bays, to prevent flooding in New Orleans should a levee fail, and that more would be gradually opened.
Reply | Report Abuse | Link to thisIt was stated that "the "slow opening" is planned to give people living in the Atchafalya River basin time to prepare for up to 25 feet of floodwaters." Good luck to those unfortunately and unexpectedly affected...
Hopefully, though, the presumedly partial opening of the Morganza Control structure won't change the course of the Mississippi - but I think your point should be well taken.
Nice map app!
How can we be so stupid. First of all, we knew that there would be a huge runoff from the Spring thaws. Then we know that just about all of the aquifers in that region are running bone dry. Duh? It would seem a natural solution to channel that runoff from the Mississippi River to replenish those aquifers. While we are at it, we could also put structures in place to replenish the farm lands with the nutrients from the Mississippi, instead of flooding these small towns for the larger cities.
Reply | Report Abuse | Link to thisFirst:"For decades, people have been building shopping malls and parking lots that cause water to flow quickly into rivers, rather than soak into the ground."
Reply | Report Abuse | Link to thisThen: "Has anything like this happened before in the U.S.?" Yes. The greatest flood of the twentieth century occurred in 1927, but there were also large floods in 1937, 1973, 1993 and 2008, although only the 1927 flood compared to this year's."
I love how the author tries to attribute these floods to human activity, and then in the next paragraph refers to floods in other years where there was no human activity.
The fact is that floods are going to happen, hurricanes and tornadoes are going to happen. They have been since the beginnings of climate. The only reason they become tragedies is because humans choose to live in their paths.
Humans do not cause these phenomena; they can provide amelioration of their effects, and in doing so may exacerbate them. (e.g.: poorly designed and situated dikes and levees).But just like nearly every other article in this magazine, this one likes to concentrate "blame" on humankind, as though somehow we are smart enough to stop a flood. We have a better chance of stopping this magazine from producing this drivel.
I have often wondered since the spring melt and subsequent flooding is not an unanticipated event, why there has been no serious diversion design activity. There is a vast amount of unused land in the American badlands. Using the interstate system as a road map and basically existing technology, pumps similiar to those used in hydro electric dams could pump water through currently produced 20 foot diameter pipes parallel to the interstaes to resevoirs in the badlands.
Reply | Report Abuse | Link to thisWith drought conditions in some states (the everglades comes to mind) the excess water could be pumped where it is sorely needed or the resevoirs for storage. The bulding project could put America's workforce and tecnological prowess to good use. It has already been predicted that water will become a rare resource in the near future. Why not plan for that now while diverting potential flood water and protecting lives and property. This could be another New Deal labor program putting many people to work for the benefit of the whole country. The system could include computer technology to monitor the rise and fall of water levels and begin water diversion before it inundates the middle of our nation. Why do we continure to wait for the crisis to address problems?
Note to JTDWYER and SIERRA9093
Reply | Report Abuse | Link to thisWith all the government concern on getting people back to work, the flooding, the droughts, they could hit three birds with one program if they enrolled some the really intelligent people in this country in a comprehensive water routing system.
Sierra, we are not stupid just the people who are supposed to doing the planning. Unfortunatelly the intelligent people did not choose to enter government service. JTDWYER, the forecast are there for most of us to see. spring rain and melt almost every year. Are they reaslly missing it or are they choosing to ignore it?
Agreed.
Reply | Report Abuse | Link to thisAs I understand, most of the water management facilities that have been constructed in the past was in response to the 1927 floods - I think originally implemented as WPA projects during the depression that coincidentally followed shortly after...
You are right BK505. We are the heads and the people who make those decisions are the "posteriors", so how do we, as they say in the service, get our heads wired to our rear-ends so that we can get something done. As we speak, and while there is flooding along the Mississippi, would you believe there is a drought in Texas. Go figure. Also, I totally missed the economic/employment factors so kudos for mentioning that.
Reply | Report Abuse | Link to thisTo Sierra9093
Reply | Report Abuse | Link to thisAs for connecting the heads, I haven't a clue. Maybe someone can get the idea across that they might have much more to gain with some foresight instead of waiting for the next crisis. Crisis management has been around for too long. It is time to locate and apply the intelligence available to solving future problems before they become a crisis. Multi-tasking isn't only for sitcoms and political cartoons.
That is an interesting thought... replenishing the aquifers. Not easy though since the aquifers consist of water filtered over 100's of thousands of years. I doubt it would help the aquifers if we pumped muddy (to put it mildly) Mississippi water directly into the aquifers. We would need to at least attempt to purify the water somewhat prior to adding it to the aquifers.
Reply | Report Abuse | Link to thisThen there is the problem of channeling these waters to where they can be added to the various aquifers. Sounds like a monumental task. But who knows, the task may be monumental but not impossible.
Sierra, Agreed it would be wise to put some of the flood waters to use, but it's not quite as simple as building pipelines. For instance, the Mississippi has non-native Silver carp in it. I don't think anyone wants these fish in the everglades or any other waterway or reservoir where they don't currently exist. Also, the Mississippi is very polluted. So much agricultural toxic waste runs into the Gulf of Mexico, it has created an extensive dead-zone and has done considerably more harm than BP. Though the flood waters would certainly be much more diluted, I'm not sure the Everglades would be a good place to dump toxic waste.
Reply | Report Abuse | Link to thisAlso, do you think environmental groups would let building such pipelines get through the EPA?
All these comments about managing the flood water! Do you realize just how much water is out there?
Reply | Report Abuse | Link to thisPutting oneself in a flood plain is like sitting down for a picnic on a highway. You know a truck is going to come along. So don't have your picnic there. Yet we, as people, go right back in after every flood and set ourselves up to get run over again.
It IS going to flood and the more you try to manage it, the more devastating the eventual disaster.
I believe the largest volume of flood water is thought to have gone down the Mississippi in 1843. One that size is the BIg One. It'll come again.
I see the satellite map of the region and see the problem lies beyond some local situation. It seems to me there is a water flow much further from the north. For example, there are water flow from Russellville situated in the North West toward south through a big channel like terrain. You have to construct some walls maybe 30 meters under the soil and 1 meter height on the soil and later enhancing the height where necessary. These walls should be built where necessary. I wrote in some of my articles about the magma forming Mississippi referring to an article from Scientific American, therefore, a slope toward golf of Mexico. My site: http://www.hamidsadeghipour.ws
Reply | Report Abuse | Link to thisI see the satellite map of the region and see the problem lies beyond some local situation. It seems to me there is a water flow much further from the north. For example, there are water flow from Russellville situated in the North West toward south through a big channel like terrain. You have to construct some walls maybe 30 meters under the soil and 1 meter height on the soil and later enhancing the height where necessary. These walls should be built where necessary. I wrote in some of my articles about the magma forming Mississippi referring to an article from Scientific American, therefore, a slope toward golf of Mexico. My site: http://www.hamidsadeghipour.ws
Reply | Report Abuse | Link to this