Mississippi flooding and climate change

Extensive flooding along the Mississippi River is being touted as evidence of global warming by the alarmist press including the Arizona Daily Star (see article). It really is a result of the La Niña phase of the El Niño–Southern Oscillation (ENSO) and the Pacific Decadal Oscillation. The extensive tornadoes have a similar cause (see The storm over tornadoes.) Accuweather said: “The combination of a weakening La Nina and the anticipated sharp temperature anomaly gradient between the northern U.S. and the southern U.S. told us that the jet stream running across the U.S. would be abnormally strong this spring. A strong jet stream leads to more powerful storms and thunderstorms, which increases the chances of large tornadoes and widespread flooding.”

The Mississippi River system drains 41% of the continental U.S. Floods are common and cyclical. The Star article claims, “Flooding on the Mississippi has become more frequent and more extensive since about 1950…” The record for the lower Mississippi from NOAA would disagree. That record, beginning in the year 1543, shows that the most floods occurred in the 1920s and 1930s, and the most extensive flood occurred in 1927 on the lower Mississippi. Perhaps the author of the Star article was looking at this record for Wisconsin and Minnesota.

The Mississippi River has an extensive floodplain. It’s called that for a reason. We have tried to modify the floodplain, and make land available, with an extensive system of levees which work much of the time, but this is one of the times the system did not work as hoped. In fact, much land was flooded due to purposely breeching the levee to sacrifice part of the floodplain in the hope of saving cities downstream. We’ve tried to tame the mighty Mississippi with our engineering works, and many people relied on these government efforts. But there is always a risk. The risk that nature is stronger. Ultimately, if you inhabit the floodplain, you should expect to get wet once in a while.

Some geology:

The Mississippi River, left to itself, wanders across the alluvial flood plain. The graphic below, a LANDSAT image shows a portion of the river. Notice the arcuate structures on the sides. These represent former reaches of the river. Below the LANDSAT image is a map of a portion of the river showing the deposits made by the various river courses (Map by Harold Fisk, 1944 US. Corps of Engineers).



 As the river flows around a bend, erosion takes place on the outside of the curve and deposition occurs in the inside. Eventually, the river cuts off the curve leaving an arcuate oxbow lake. The graphic below from the Iowa DOT shows how this occurs.


Finally, we have a pair of photos (USGS/NASA) showing a portion of the river in May 2006 and during the flooding in May 2011.




  1. Climate is defined as the effect/averages of thirty years of weather. In some cases there are over thirty years of data – temperatures for example, which date back about 100 years – and sometimes there is not.
    Idiots will say anything – including it isnt possible to effect the earths biota as it is much too large. If you quote an idiot just to take a contrary position you are just using them as a strawman – pointless.
    Having an article explaining a process is interesting. But using the comments of a ‘possible’ idiot as an opportunity to ‘strike a blow’ isnt.
    You want the real culprit? The Army Corp of Engineers serving the interests of commerce. There hasnt been a more miguided group since the fall of the Soviet Union. A nation that was convinced that reversing rivers and damming the Nile made sense.  … oh and the harm done to the biota by unconstrained greed – which continues.
    By the way, the causes of climate change range from pollution to deforestation – the effects of our ‘cultural’ presence on earth. Unless you think our presence has no effect.
    As mean temps increase, the atmosphere has an increased capacity to transport water which results in more energetic and varied weather patterns.
    From http://www.wsws.org/articles/2011/may2011/clim-m23.shtml

    Insurance companies, positioning themselves for profit, have closely tracked the economic impact over the years. Nikhil da Victoria Lobo at the international reinsurance firm Swiss Re explained the rising tide of costs associated with the extreme weather during the UCS press conference. “Economic losses from natural disasters have soared from a global average of $25 billion annually during the 1980s to $130 billion a year during the decade ending in 2010,” he remarked.
    Although it’s not possible to say exactly how much is due to climate change—a significant portion is also attributable to increasing development in flood-prone areas—there is little doubt that climate was a major factor, he explained.
    Indeed, it is not possible to pinpoint a specific causal role for climate change in any individual flood. Nonetheless, as Dr. Hayhoe explained, “We do know that every event that happens is already superimposed on very different background conditions than we had 50 years ago.” The probability of flooding increases, analogous to “loading the dice,” she said.

    As a note – Dr. HayHoe, chosen for no reason in particular, is described here …
    I would honestly take your posts more seriously if they didnt generally take a profits protectionist position and were limited to facts and science.

  2. “Extensive flooding along the Mississippi River is being touted as evidence of global warming by the alarmist press including the Arizona Daily Star (see article). It really is a result of the La Niña phase of the El Niño–Southern Oscillation (ENSO) and the Pacific Decadal Oscillation.”

    …and everybody knows, anthropogenic influences couldn’t possibly effect the Pacific chilluns….

    Why do people that don’t know a damn thing about science insist on telling us what is going on, with political not scientific arguments.

  3. Are you calling the “Star” an idiot?  It is interesting that you refer to the World Socialist Web Site and an evangelical Christian site and complain that I refer to biased sources.  I do agree, however, that there are many causes of climate change and the principle human cause, at least locally, is land use change.

    1. I would be happy to call the Star an idiot, but I dont lend any credibility to the publisher. Its the author and the message that may be the idiot – or not.
      You mentioned the messenger, several times (star etc), I mentioned the message and identified the author of the message – who is hardly an idiot.
      I am not a pamphleteer. Are you?
      Local is good, but dont ignore the global.

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