Record floods on Mississippi River

One of the reasons that people suggested that the Atchafalaya would eventually "capture" (that is, the main flow of water through our state would exit Morgan City instead of its present location at the mouth of the Mississippi) is that the distance is so much shorter and steeper to the Gulf via the Atchafalaya than the meandering Mississippi:

ORCS to Gulf via Atchafalaya: 142 mi
ORCS to Gulf via Mississippi: 335 mi

If the events of 1973, as described above happened, how would life on the lower Mississippi and Louisiana coast change? Would the present-day Mississippi River suddenly dry up? Would a fisherman sitting by the river see it go "glub, glub, glub," with fish flopping around in the mud? Would ship traffic stop on the river? Would there be any impact at all? The following description of possible life after the change is excerpted from Kazmann and Johnson (1980:10-16).

In the aftermath of the huge floods that would cause the main flow of the river to jump to the Atchafalaya River, aside from the cost, anxiety, tragedy, and aggravation of dealing with massive amounts of water being in the wrong place, there would be lingering issues that would change the way of life on the lower Mississippi. Instead of 70% flow down the lower Mississippi and 30% flow down the Atchafalaya, the percentages would probably reverse. The Atchafalaya would be a rushing, raging river, even during the fall for a period of time until it scoured the channel and filled in the lower reaches so that the flow would diminish. Morgan City would have to be relocated, as would other communities and many businesses, possibly including the massive infrastructure of the offshore oil and gas industry. Fisheries would be altered measurably all across the delta. Oyster reefs would be immediately destroyed, and would take several years to reestablish and become productive (no erysters!). It would probably take two decades to adapt to the new environment around present day Morgan City. Additionally, pipelines, bridges, and the like that cross the Atchafalaya would be destroyed or rendered unsafe. The ruptured natural gas pipelines would place stress on fuel supplies for energy companies, but they would quickly change to more costly fuel sources and have little or no interruption of service. Imagine the traffic jams when and if bridges on I-10, U.S. 90, and U.S. 190 collapse (what about the railroads)? All trans-state traffic would have to be rerouted to I-20 via I-55 through Jackson, Mississippi, adding up to 615 miles to the trip (not to mention time delays from the traffic jams). The protective levees of the Atchafalaya Basin would have to be upgraded to handle the new pressure from spring flows. And, oh my gosh, think of the negative impact on the crawfish supply!

The lower Mississippi would still have a copious amount of water, but it would be slack compared to today. Shipping could continue to be an important industry, but it would be interrupted for a time. The slack water would allow (cause) the thalweg to fill in and stop deep-draft shipping. However, after intensive dredging efforts it may be found that a 50 ft channel can be easily maintained because of the tremendous decrease in sediment. New Orleans, possibly Baton Rouge, and all other cities and towns along the lower Mississippi would no longer be able to get their drinking water from the river. It would become too salty, since the lower fresh water flow would not offset the tidal movement of the Gulf. Can you imagine the cost of piping or trucking enough drinking (and flushing, etc.) water from north of Lake Pontchartrain to supply the needs of Greater New Orleans? Can you imagine Greater New Orleans without water for drinking and sanitation? Even when the water was just barely increasing in salinity, there would be severe damage to water heaters, fire sprinklers, fire truck pumping systems, and more. The quality of our coffee! As mentioned above, the fisheries (especially those associated with the fresh water river) would suddenly change. And what about the massive petrochemical industry corridor? Aside from the impact on shipping, which they could weather over time, industry could no longer use fresh river water for thermo-electric cooling. The saltier water would corrode all the pipes and related instrumentation. Of course, industry would change to salt-tolerant materials, but that would be costly and time consuming. Also, the sugarcane industry would have problems without sufficient fresh water.

All of this adjustment, and we have not delved into the intensity of impact on people's lives during the crisis and the adjustment period. All normal routines would stop. Businesses would be closed, as would schools, normal government, etc., etc. Virtually the entire population would spend months and months just coping - just putting their and others' lives back together. Imagine the emotional strain to the population - people losing a lifetime of accomplishment. This would be a tragedy of monumental proportions. It would interrupt life much like World War II.

One can also imagine the impact on the nation. Massive use of Federal dollars to protect and restore Louisiana's infrastructure. Loss of natural gas (there would be brown-outs throughout the eastern seaboard). Commerce would be interrupted by restriction of travel and Louisiana=s inability to focus on supplying items traditionally demanded from her natural resources by the nation. Prices of all Louisiana products (from the natural resources to industrial products ) would soar. The interruption of the pogie fisheries would be very negative for such food industries as chicken, catfish, and hogs (see the last section of the notes). New Orleans is one of the most important ports in the nation, and it would suddenly cease to function; all shipping and related industries on the Mississippi River would stop. International trade would be further imbalanced. The massive fertilizer business would shut down and the agriculture industry would falter.

... much more at link ...

/... http://www.americaswetlandresources.com/background_facts/detailedstory/LouisianaRiverControl.html

BATON ROUGE -- A decision on whether to open the Moganza Spillway to relieve pressure on Mississippi River levees could be made next week, Gov. Bobby Jindal said Friday.

But water already is rising in the vast floodway because of the mandated diversion of 30 percent of the Mississippi's flow into the Atchafalaya River.

Jindal said residents who flooded when the spillway last opened in 1973 should expect flooding again.

He urged residents who might be affected to make plans to evacuate on their own or to Red Cross shelters, which would be located closer to residents' homes than would be the case for a hurricane.

/... http://www.nola.com/politics/index.ssf/2011/05/jindal_to_atchafalaya_resident.html