Saturday, May 14, 2011

Historic flooding wreaks havoc along Mississippi River

Cross-posted at the Washington Examiner....

Is disaster looming in the Mississippi Delta? As the over-flowing river heads south, it is a reminder that the mighty Mississippi River has historically changed course every 1,000 years due to major flooding and silt build-up.

The Flood of 2011 could go down as one of the most devastating and could possibly do its part in moving the river as some believe it has been trying to do the past century. Already Memphis, Tennessee, and Vicksburg, Mississippi, as well as other up-river cities, have lost hundreds of homes to flooding while thousands of people wait down-river for the devastation to hit them. An expected $4 billion or more in damages is expected. NASA images show the Mississippi River before and after flooding.

The reason for all this water?
Swollen by weeks of heavy rain and snowmelt, the Mississippi River has been breaking high-water records that have stood since the 1920s and '30s. It is projected to crest at Vicksburg on May 19 and shatter the mark set there during the cataclysmic Great Flood of 1927. The crest is expected to reach New Orleans on May 23.
Tributary rivers are backing up because the Mississippi River is so full there is nowhere for the water to go, causing more flooding inland.

The Daily Impact reported the possibility of the Mississippi River trying to change course, something that has been kept in check by the Army Corps of Engineers, who called it the "war against nature," at the direction of Congress in the 1950s:
As The Daily Impact has been reporting, almost exclusively (see “Mississippi Rising: Apocalypse Now?” and “Mississippi Rising: Update”), the rising waters of the Mississippi pose an existential threat to the Port of New Orleans and, thus, a large chunk of the economy of the United States. To restate, briefly: the river has been trying for a century to change its lower course, as it had previously done periodically, and was shifting its flow toward the Atchafalaya River, which would take it into the Gulf of Mexico at Morgan City, 65 miles west of New Orleans. In the 1950s, seeing the economic disaster that would be precipitated by this change, the Congress ordered the US Army Corps of Engineers to prevent it.

The Corps built the Old River Control Structure — a huge set of flood gates — on a channel connecting the two rivers to enforce the Congressional mandate that no more than 30% of the Mississippi’s flow would be permitted to enter the Atchafalaya. The war against nature — that is what the Corps called it — was in the “mission accomplished” category for ten years after its construction, that is, until 1973. (More detailed history here.)

That year, the Mississippi recorded a flood stage of 58.2 feet (at Red River Landing just downstream from the Old River Structure). The water cut through the flanks of the structure and undercut its foundation pilings, taking it to the very brink of catastrophic failure. The Corps later reinforced and added to the Structure (that is why it is now, officially, called Old River Control Structures, plural) and assures us that the Mississippi will not change course as long as they are on duty.
Now all eyes are on the lower river area as flooding of epic proportions has inundated upper regions of the river and now heads toward New Orleans at the rate of millions of gallons of water per second.

If the Mississippi diverts to the Atchafalaya River, it could be catastrophic, according to Rafael G. Kazman and David B. Johnson of Louisiana State University who wrote about it in 1980. They surmised it could cause major disruptions to the oil and gas industry, destroy oyster beds that could take up to 20 years to return, the lower Mississippi River would become salty as the downward flow of fresh water would slow and not prevent salty tidal Gulf waters from invading further upstream, huge shipping disruptions on the river, and the loss disastrous loss of revenue from the New Orleans port. As The Daily Impact wrote:
In sum, Katzman and Johnson concluded in 1980, “in the long run the Atchafalaya will become the principal distributary of the Mississippi River and that the current main stem will become an estuary of the Gulf of Mexico…the final outcome is simply a matter of time.”

The question of whether that time is now will be answered in the next 10 days or so.
The city of Natchez is expected to flood on May 21 with New Orleans to follow on May 23.

Damage in Baton Rouge and New Orleans could be lessened if the Corps of Engineers opens the Morganza spillway to relieve pressure on levees but it would flood thousands of acres of farmland and thousands of homes. The heart-breaking aspect has made grown men cry at the thought of losing their farms, homes, and crops. Watching a news anchor standing on land that, he says, will be under 15-20 feet of water by this weekend is surreal, an incomprehensible disaster about to change some people's lives forever. Charts help explain the flooding issues now taking place, and what to expect.

Meanwhile, residents continue to stack sandbags in the hope they can hold back the powerful forces of nature, waiting to see the extent of the Flood of 2011, and engineers wait to see if the mighty Mississippi will shift to a new path to the sea.

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