Showing posts with label Atchafalaya River. Show all posts
Showing posts with label Atchafalaya River. Show all posts

Monday, May 30, 2011

High Water along the Atchafalaya and Mississippi Rivers, May 2011

As I described in the previous article, the Atchafalaya River carries 30 percent of the combined flow of the Mississippi and Red Rivers. In times of flood, more than 30 percent may have to be diverted to prevent levees being overtopped in Baton Rouge and New Orleans.


One of the towns subject to high water is Melville, Louisiana. The first photograph shows the landing for the former Melville-Pointe Coupee ferry service, which permanently closed in December 2010. Dump trucks were rumbling past to a site just south of the landing, where the levee was being elevated. The second photograph shows how high the water was under the railroad bridge, 14 May 2011.


Morgan City is a historic town near the Gulf of Mexico mouth of the Atchafalaya. Having suffered from many floods in the past, the Corps of Engineers built a levee and floodwall system around the town in 1926. The concrete floodwall is a popular tourist attraction because you can look down on the Atchafalaya on one side and down on the historic city on the other. Normally there are a boardwalk and docks on the river side, but this time, the river was well above the base of the floodwall (15 May). The bridge in the background is US 90


Finally, New Orleans. The levees have been reinforced since Hurricane Katrina and raised in some areas. Along the French Quarter, the levees were well above the water level, even under conditions of the 2011 flood. For tourists, it was a great opportunity to be photographed next to Ol' Man River (or The Big Muddy).

(Photographs taken with an Olympus E-330 camera and Olympus 14-54mm f/2.8 lens)

Saturday, May 21, 2011

Where does the Water Go? The Old River Control Structures, Louisiana

Introduction.  The 2011 Mississippi River flood brought the news media to towns like Memphis, Vicksburg, and Natchez. But although they showed photographs of wet homes, they did a shallow coverage of the river, its flow, and water control, and explaining what happens to the water and sediment and why our economy depends critically on this control. It is a complicated topic, but I will try to summarize why the US Army Corps of Engineers built and operates major hydraulic structures at Old River, Louisiana, and show some photographs.
Mississippi River drainage area (from US Army Corps of Engineers). Pink shows the area protected by the Mississippi River &Tributaries Project
Background. "The Mississippi River has the third largest drainage basin in the world, exceeded in size only by the watersheds of the Amazon and Congo Rivers. It drains 41 percent of the 48 contiguous states of the United States. The basin covers more than 1,245,000 square miles, includes all or parts of 31 states and two Canadian provinces, and roughly resembles a funnel which has its spout at the Gulf of Mexico. Waters from as far east as New York and as far west as Montana contribute to flows in the lower river." (from US Army Corps of Engineers).

Before the mid-1800s, the Red River joined the Mississippi about 45 miles northwest of Baton Rouge, Louisiana, at latitude 31.1 degrees north. By definition, the Red was a tributary because it added its water to the main river. Just a short distance to the south, some water diverted off the main channel into the Atchafalaya River, which carried the flow to the Gulf of Mexico. Therefore, the Atchafalaya was a distributary because it carried water away from the main channel.
From US Army Corps of Engineers
In the early 1800s, the Atchafalaya only carried a small percentage of the total flow because it was clogged with immense rafts of logs and debris. But starting in the mid-1800s, the Corps of Engineers and State of Louisiana methodically cleared the logs to open up the channel for navigation and commercial development. Clearing log jams on Western rivers was one of the Corps' earliest civil works missions.

By the early 20th century, the Atchafalaya had been cleared and dredged to create a Federal navigation project. Dredging continued to improve navigation. But, a serious problem developed: during the early years of the 20th century, the Atchafalaya channel naturally scoured (became deeper) and proceeded to capture an ever greater percentage of the Mississippi's total flow. The reason was geological: The distance from Old River to the Gulf of Mexico via the present river channel past Baton Rouge and New Orleans and ending at the present Balize delta was about 300 miles, while the distance along the Atchafalaya waterway was only 140 miles. This meant the new route was steeper and therefore more efficient. From 1880-1950, the percentage of Mississippi water flowing down the Atchafalaya increased from 7 to over 25 percent, and river hydrologists predicted that by the 1970s, the Atchafalaya would capture almost all the flow (Reuss, 2004). Under natural conditions, this type of channel shifting occurred about every 1000 years, but for a modern industrial economy, such a shift would have disastrous economic consequences.

Consider what might happen: New Orleans would lose its fresh water supply. The many petrochemical plants and the nuclear power plant on the river between Baton Rouge and New Orleans would lose water supply. It might be close to impossible - or vastly expensive - to maintain a deep-draft navigation channel suitable for ocean-going vessels to reach Baton Rouge. Note: Baton Rouge is now a deep-draft port, meaning one suitable for ocean-going vessels. The reason this is possible is the scouring action of the Mississippi flow, which flushes much of the sediment load out to sea, leaving a deep channel.

In the 1954 Flood Control Act, Congress authorized the Corps of Engineers to build structures to control the flow of water down the Atchafalaya. The Act also authorized future appropriation for navigation locks. The flow was to be maintained at 30 percent of the total at that latitude. This is complicated to compute because it includes the input from both the Mississippi and Red Rivers. Therefore, the diversion from the main trunk of the Mississippi is somewhat less than 30 percent, depending on how much water is coming down the Red. The following figure shows what Congress intended.
From US Army Corps of Engineers
Presently, "The Old River Control project consists of several large engineering structures. These structures include the Old River Low Sill and Overbank Structures that began operation in 1962; the Old River Lock completed in 1963; and the Auxiliary Structure built in 1986." (From US Army Engineer District, New Orleans, web page.) The lock is necessary because often the Red and Mississippi are at different levels, and the lock lets barges transit from one river to the other. Adding to this complex, in 1990, the Sidney A. Murray, Jr. Hydroelectric Station was built to generate electricity using turbines.

Photographs.  Driving south on Louisiana 15, which follows the levee along the west side of the Mississippi, the road crosses a bridge at the Sidney Murray station, then crosses the Overbank Structure, and finally reaches the Low Sill Structure.

Upstream side of the Sidney A. Murray hydroelectric plant. This 2009 photograph was taken at low water. The intakes for the turbines are way below the water level and there is little to see for the casual visitor..

The downstream side of the Overbank Structure at low water on January 19, 2009.

One of the bays in the Overbank Structure. During floods, wood boards or batons can be lifted one by one to control the flow of water. In the 2011 flood, leakage past the boards amounted to about 50,000 cubic feet per second (cfs).

Downstream side of the Low Sill Structure, 14 May, 2011, with flow of approx. 200,000 cfs.

The upstream side on the Low Sill structure. Water this high is a very rare event; it may be decades before we see it as high again. During the flood of 1973, a great scout hole formed on the south side of the structure (the far side in this photograph). Engineers feared the structure might collapse, which would have led to the abrupt switching of water flow down the Atchafalaya waterway. If this had happened, a new structure could have been built in summer, when the water was low, but it would have been technically difficult and very expensive. Congress would have had to appropriate emergency funds. Months of excess flow down the Atchafalaya waterway would have caused many economic, sedimentological, and environmental consequences.

The vertical panels are the gates. A crane moves along a track, and the operators raise or lower the panels into the concrete slots in the dam. The amount of water is controlled by how high the panels are above the concrete bottom. Water flowing along the bottom of the concrete channel flushes sediment through the system into the outlet canal and, ultimately, into the Atchafalaya.

The next structure to the south is the Auxiliary Structure. This was built after the 1973 flood almost destroyed the Low Sill Structure and engineers realized that that another structure was needed to channel some of the water to the Atchafalaya. Construction began in 1981 and was completed in 1986.

Downstream side of the Auxiliary Structure, 14 May 2011.

One of the the six tainter gates. These are steel arches fixed to trunnion blocks and lifted by steel cables. In this photograph, the gates are up 23 ft, resulting in total flow of 230,000 cfs. These gates can be controlled more precisely than the rectangle steel panels used in the Low Sill Structure.

The operators have to coordinate with the hydroelectric plant to adjust the water flow through all the structures. On May 19, the Mississippi was flowing at about 2,000,000 cfs, so the hydro plant, Overbank, Low Sill, and Auxiliary released about 600,000 cfs to the Atchafalaya, maintaining the 30/70 percent ratio.

Wood and flotsom get jammed up against the gates, and the raft often contains some interesting cargo. The cables hold up the gates and go up into the structure to heavy-duty electric winches.


The morning I visited, the gate operators and a ranger hoisted up a boar that had gotten stuck on the log raft. They said they were going to feed him corn for a few weeks. Sounds like an upcoming BBQ and plenty of bacon.

References

For a long but engaging description of the topic, I suggest a February 23, 1987 New Yorker article by John McPhee titled "The Control of Nature, Atchafalaya": Control of Nature

A shorter summary was written by Alexis Madrigal for a May 19, 2011 article in The Atlantic:
What We've Done

For a more scholarly treatment: Reuss, M. 2004. Designing the Bayous, The Control of Water in the Atchafalaya Basin, 1800-1995. Texas A&M University Press, College Station, TX, 474 p.

Acknowledgments

Thank you to New Orleans District Corps of Engineers and the operators of the Old River Control Structure for hosting tour groups from the Waterways Experiment Station in 2009 and 2011. We appreciate the time they took to show us around.

Thursday, January 21, 2010

The Mississippi River Basin Model, Jackson, MS

The Mississippi River Basin Model at the Waterways Experiment Station (WES) was the largest hydraulic model ever built. It was also the most complex attempt ever undertaken to model the river system that drains a good part of the North American continent. The purpose of the model was to test the behavior of the 1.25 million square mile Mississippi River and Tributaries Project and evaluate levees, floodways, cutoffs, and reservoirs. The ambitious project was conceived by Lt. General Eugene Reybold in the early 1940s after smaller models had proven their worth in examining the behavior of individual projects.


During World War II, many engineers and technicians were serving in the war effort and manpower was scarce. General Reybold arranged to use German prisoners of war as laborers to clear and prepare the site. A site was chosen in Clinton, Mississippi, about 35 miles east of the Waterways Experiment Station in Vicksburg. By the end of the war, about 1,800 prisoners of the Afrika Korps were living nearby in an internment camp. I have read that many of these men were engineers and highly-trained professionals who worked on the project with enthusiasm and typical German precision and engineering prowess. (Also, this assignment may have been a bit more pleasant than cutting timber in lumber camps in Wisconsin in winter.). Some of the officers married Clinton women.

The project took 20 years to complete, with the last sections finished in 1966. WES used the model during the great flood of 1973 to predict what would happen if the Old River Control Structure in Louisiana were to fail, allowing a major portion of the of the Mississippi system's water to flow down the Atchafalaya watershed. The last use was in 1993, during the record-breaking floods of the Mississippi system in the upper Midwest. When the Corps planned to breach some of the main stem levees near Prairie du Rocher and Fort de Chartres, Illinois, the model was partially revived to examine water flow and effects of the levee breaches. The Corps finally closed the project permanently and turned the land over to the City of Jackson in 1993. The City of Jackson mowed the grass through 2006, but abandoned all maintenance after that.
The concrete portions of the model are still largely intact. You can easily visit the site by taking Springridge Road south from Interstate 20 and then turning left on McRaven Road. Turn left into Buddy Butts Park. Part of the site has a fence, but much of it has fallen down. The land is no longer clear as in the aerial photograph above, and brush and trees are slowly taking over. But, as of January 2010, you can still easily climb the observation platforms, walk around in the river basins, and pretend that you have walked from Morgan City to Sioux City.
The concrete shaping of the landscape was amazing. Imagine the survey skill required to precisely shape the terrain representing a major portion of the continent. The little pegs in the channels are friction elements.
Some of the buildings are falling down, but several of the control houses are largely intact.
Stevens paper chart recorders
The control buildings still have rows of Stevens paper chart recorders on shelves, abandoned in place just as if the technicians planned to return to work some morning. One of my coworkers was a property officer and remembers how she had to record the serial numbers on all the instruments and pumps annually. (July 2016 update: the recorders have been stolen.)
The massive pumps are still in place, slowly rusting and getting overgrown. From what I can tell, the City of Jackson does not maintain anything on the site. This is a good example of how nature takes over, a small scale experiment of the transitions speculated in the History Channel's Life After People.
I took these photographs on January 18, 2010 with an Olympus E-330 digital camera. The first three photographs in this blog are courtesy of the Coastal and Hydraulics Laboratory, Engineer Research and Development Center, U.S. Army Corps of Engineers, Vicksburg, Mississippi.

Update May 7, 2013 (anniversary of V.E. Day): The historian of Mississippi Valley Division, Mr. Charles Camillo, generously sent me this photograph of the POWs working on one of the drainage canals. Date and photographer not recorded. 

Update July 26, 2016: For more photographs of the Basin Model, please click the links:

http://worldofdecay.blogspot.com/2010/12/update-mississippi-basin-model-further.html

http://worldofdecay.blogspot.com/2010/07/update-on-mississippi-basin-model-in.html

http://worldofdecay.blogspot.com/2013/01/mississippi-basin-model-construction.html

http://worldofdecay.blogspot.com/2015/11/mississippi-river-basin-model.html

UPDATE JULY 2017:  A volunteer organization has been formed to clean and clear the site and develop it as an education/interpretive center. Readers interested in participating in the cleanup work, please contact: 

Sarah McEwen
President, Friends of the Mississippi River Basin Model
601-376-9131
Twitter: @MSRiverBasinMod
Facebook: @FriendsofMississippiRiverBasin Model