Geological investigation of the alluvial valley of the lower Mississippi River

While some of the conclusions of this report are dated, the beautiful maps of the evolution of the river are the best illustration of the dynamic nature of river deltas. The maps are known as meander maps.

Fisk, H.N., 1944, Geological investigation of the alluvial valley of the lower Mississippi River: U.S. Department of the Army, Mississippi River Commission, 78p.


Click on the image for larger size.

Inundation Maps – Flood of 2011 on the Lower Mississippi

Lower Mississippi water flows and inundation map – 11 & 16 May 2011, from the Corps.

Warning to the residents from the Corps’ WWW site:

Every year, written notices are issued to all interests reminding them of the possibility of operation of the floodway. In the event that Morganza needs to be opened, the USACE project managers, along with news media and civil officials, will help notify all interested parties as soon as possible. On receipt of such notice, expeditious action must be taken as soon as possible to protect life and property. If the Morganza Floodway is operated, there is a possibility that personal property will be flooded. In the event of an opening, all water and/or gas wells must be sealed and capped to prevent contamination from floodwaters.

Current High Water Flows – 16 May 2011 (Full size image)

Current High Water Flows

Current High Water Flows – 11 May 2011

Current High Water Flows

 

 

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Estimated Inundation Map Scenario 1 depicts anticipated impacts from operation of the Morganza Floodway at 50% of its capacity with full operation of the Bonnet Carre’ Spillway. The previously released Estimated Inundation Map is the same as the Estimated Inundation Map Scenario 1.

Estimated Inundation Map

 

 

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Inundation Map Scenario 1a depicts anticipated impacts from operation of the Morganza Floodway at 25% of its capacity with full operation of the Bonnet Carre’ Spillway. (Click here for full size image.)

Estimated Inundation Map

Estimated Inundation Map Scenario 2 depicts anticipated impacts from non-operation of the Morganza Floodway with the Bonnet Carre’ Spillway operating at 100% capacity.

Estimated Inundation Map

 

 

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Estimated Inundation Map Scenario 3 depicts anticipated impacts from non-operation of the Morganza Floodway with excess flowing through Old River and the Bonnet Carre’ Spillway operating at 100% capacity.

Estimated Inundation Map

 

 

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Old River Control Structure

This is the gate on the Mississippi/Red River confluence that is the source of the Achafalaya River. At the moment it is flowing at nearly 300,000 CPS. This is as much as Morganza with all the bays open, and three times more flow than than the Niagara Falls complex. During the flood of 1973, the water began to erode the banks and get under the supports of the structure. Had it been destabilized, it could have failed and let the bulk of the Mississippi flow down the Achafalaya. That would have catastrophic consequences down river during a flood event, and could prevent shipping on the lower Mississippi until enough flow could be restored to float barges safely. John McPhee wrote about this in his book, Control of Nature.

 

Fisk, Harold Norman. Geological investigation of the Atchafalaya Basin and the problem of Mississippi River diversion. Waterways Experiment Station, 1952. – This report predicted the capture of the Mississippi River main channel by the Atchafalaya River by the 1970s, resulting in the construction of the Old River Control Structure.

Kazmann, Raphael Gabriel, and David B Johnson. “If the Old River Control Structure Fails?” (1980). – This report analyzes the economic consequences of the Old River Control Structure failing. These include the end of shipping to the Gulf on the old channel and the loss of drinking and industrial water in New Orleans and up river as the saltwater backed up the river.

Corps, Old River Control, (2009) – Brief history and pictures of the ORCS

Ashley N. Cox Jasen L. Brown Robert D. Davinroy Jason Floyd Emily Rivera Ivan H. Nguyen, Mississippi River and Old River Control Complex Sedimentation Investigation And Hydraulic Sediment Response Model Study, (2011) – An in-depth look at the current capacity and geology of the Old River Control Complex, including extensive plates in the appendixes.

Heath, Ronald E., et al. Old River Control Complex Sedimentation Investigation. No. ERDC/CHL-TR-15-8. ENGINEER RESEARCH AND DEVELOPMENT CENTER VICKSBURG MS COASTAL AND HYDRAULICS LAB, 2015.

 

Morganza – too late, still too little?

Morganza is slowing being opened. The projected crests  downstream have been revised, but as the previous post illustrates, the projected crests still leave very high water from Baton Rouge to New Orleans. We can debate (and will) the Corps decision to delay opening Morganza in hopes it could protect the floodway. Now that the floodway is in use, there is no reason to keep the river levels so high. Morganza could be fully opened. This would reduce the down river levels and flush the flood waters out of the lower river faster, rather than letting high water persist well into June.

Every day the river is this high, the levees get soggier and weaker, and more water pass under the levees. When the river is very high, navigation is also slowed and is more difficult. This increases the shipping losses. It also increases the chance that a navigation accident will break a stressed levee. Over the weekend, a string of barges broke loose and two barges struck the old Highway 190 bridge in downtown Baton Rouge. Fortunately, the bridge does not appear to be damaged. But those barges could also have hit the levee, and since the water is so high, such a hit would have a higher chance of breaking through the levee and letting water into downtown. The longer the Corps leaves the downriver areas with high water levels, the greater the change of a catastrophic levee failure.  The longer the Corps keeps the river in flood, the great the chance of more upstream rain piling into the existing flood, and the higher the risk of the river system still being loaded with an early season hurricane.

Water Levels in South Lousiana

The state has closed access to the levees all along the Mississippi. This makes getting pictures of the water level more difficult.

This was taken on the West Levee opposite the old ferry landing in St. Francisville, LA. This is a very big, tall levee. The water is about 15 feet deep on one side, and is at least ten feet from the top of the levee. It will rise a bit more with current projections, perhaps a couple more feet. Normally, there would be dry land on both sides of the levee.

 

 

 

This is downtown Baton Rouge. Notice the water level in relation to the top of the walkway. The walkway is at at the height of the top of the levee, and water is only 3-4 below it. When this picture was taken, 14 May, the river was at 44 feet in Baton Rouge. It was originally projected to crest at 47.5 feet, before the decision was made to open Morganza. Even at the new projected crest of 45 feet, the levees are under very high stress, at some points water is pushing into downtown parking lots on the river.

This picture was taken downtown New Orleans on 15 May. Look at the water level in relation to the walkway on the top of the levee. As with Baton Rouge, there is very little freeboard. The river is about 17 feet in this picture, and was originally projected to crest at 19 feet.

Playing Politics with Morganza?

Took a drive up to the Old River Control Structure and the Morganza Spillway on the 12th of May. I was curious about what is keeping the Corps from opening the spillway until the flow hits 1.5 M CFS. One reason would be that until the river gets to that level, the water is not high enough for the spillway to work. I found that the water is high enough, so that we have to think about the politics.

While the Corps was able to get development easements as well as flowage  easements over most of the floodway, it is not clear that these have been enforced. The floodway also endangers Morgan City, which sits at the end of the Atchafalaya river, were the floodway necks down and the water has to flow out into the gulf through a main and minor branch of the river. (For those who are not local, tt is pronounced A CHAF A LIE A – short As.) The Corps trigger point is 1.5 million CFS at Red River Landing, just above the control structure, not the water heights downstream. How that flow corresponds to downstream heights depends on a lot of factors that change through time. The Corps has not publically addressed why it is sticking to the 1.5 MCFS, which was determined when the structures were built. It might have been the right number then, but now it results in very (record) high water downstream – that, or the flow is actually higher and the Corps have not figured it out.

The water level is below the levee tops, but it is well up the side of the levees. The projected crests before Morganza will be opened is pretty close to the tops of the levees. This puts a lot of pressure on the levees and pushes a lot of water under the levees. This water flows through sand boils, which are old stream beds which were covered when the levees were built. The water also flows through the saturated ground. The river is deep in many places and the water spreads out through the soil for a long distance. The longer the water level is high, the more water the clay in the levee absorbs, which weakens the levee. Clay levees do not melt away as did the sand levees on the middle Mississippi which broke during the 1993 flood. But when they develop a crack (crevasse), it erodes quickly and is difficult to plug during high water. In New Orleans, most of the city is below sea level and trapped within flood control levees. A levee break could rapidly put enough water into the city to flood many areas as deep as Katrina, and at least as fast. It would be worse because the water would be flowing through the high ground that was not flooded during Katrina. This might be the French Quarter, or the Ochsner medical center, or other high value areas that escaped Katrina damage.

The advantage to the Corps in putting these areas at unnecessary risk is that it will mute criticism when the spillway is opened and floodway is flooded, displacing people and destroying crops, and perhaps flooding Morgan City. Ironically, it is not a tradeoff – as the Corp’s maps show, if the spillway is not opened, it will be overtopped, as will other levees allowing water into the floodway. If the Corps opened all the relief valves early, protecting the levees downstream in Baton Rouge and New Orleans, it would be accused of not needing to open the spillway – unless the Corps creates a threat downstream, no one in the floodway would accept that there would have been a threat. (I have discussed this in my smallpox paper – politically, you do not want to roll out the smallpox vaccine until there are enough deaths to really scare people. Then no one will second guess you when there are serious vaccine complications. Do it early, stop the outbreak, and all people will see are the complications.)

The down side to the “scare them downstream strategy” (and the smallpox slow reaction strategy) is that if you guess wrong, it is catastrophic. The politicians in Baton Rouge and New Orleans are reassuring the population that the levees are perfect and that there is no risk. This means no evacuations, no thinking about what you would do if there was a break. Lower Mississippi levees are much better than hurricane levees, and much less susceptible to failure. Among other reasons, they are maintained by the Corps, while New Orleans levees were (not) maintained by the local levee boards. But there are probably 200 miles of levees between the Old River Control Structure and New Orleans. It is hard to assure that every mile is perfect. It is also impossible to keep materials and crews to plug a leak along the whole area. It would take a lot of time to get folks in place to repair a break, enough time to do real damage, and perhaps long enough for the levee to break down to the point where it cannot be repaired during high water.

An additional downside is the uncertainty for the people in the spillway. The Corps’ policy of only announcing a decision to open the spillway at the last minute leaves persons in the spillway uncertain whether they will need to evacuate. and when they need to be gone. The Corps predicted the record crests in Baton Rouge and New Orleans weeks ago. If the policy was to prevent levees downstream from being subjected to dangerous loads, the Corps could have announced that the spillway would be opened early in May. This would have given more evacuation time and would also have saved Baton Rouge and New Orleans from being exposed to unnecessary catastrophic risk.  It would also have allowed the gradual fill time necessary to protect wildlife without extending the high risk levels downstream.

 

NAS Climate Change Project

Convened by the National Research Council in response to a request from Congress (P.L. 110-161), America’s Climate Choices is a suite of five coordinated activities designed to study the serious and sweeping issues associated with global climate change, including the science and technology challenges involved, and to provide advice on the most effective steps and most promising strategies that can be taken to respond.

NAS Climate Change Project – original link

America’s Climate Choices

Advancing the Science of Climate Change

Limiting the Magnitude of Future Climate Change

Adapting to the Impacts of Climate Change

Informing an Effective Response to Climate Change

 

Climate Change and Polar Ecosystems

“The polar regions are experiencing rapid changes in climate. These changes are causing observable ecological impacts of various types and degrees of severity at all ecosystem levels, including society. Even larger changes and more significant impacts are anticipated. As species respond to changing environments over time, their interactions with the physical world and other organisms can also change. This chain of interactions can trigger cascades of impacts throughout entire ecosystems. Evaluating the interrelated physical, chemical, biological, and societal components of polar ecosystems is essential to understanding their vulnerability and resilience to climate forcing.”

Frontiers in Understanding Climate Change and Polar Ecosystems: Summary of a Workshop Committee for the Workshop on Frontiers in Understanding Climate Change and Polar Ecosystems; National Research Council, NAP (2011)

Ocean Rise in New York State

New York State Sea Level Rise Task Force, Report to the Legislature, December 2010.

“New York State’s extensive ocean coastline has places that we know, that we remember and that have shaped us in some way. The state’s coastline includes many notable locations—Montauk Point, Coney Island, Robert Moses State Park, Battery Park and the Hudson River’s shores from New York City to the federal dam at Troy. More than 60 percent of New Yorkers live in homes on or near these waterfront areas. Each shoreline area is unique and part of the essence of New York. But these places will change as sea level rises, and the differences will become more obvious as the sea continues to rise to levels never experienced by humans. A result of the world’s changing climate, a rising sea will alter more than just the coastline. The entire state will feel the effects as residents and a significant amount of the landscape are affected. These areas are diverse and interconnected and share New York’s rich agriculture, commercial, economic and environmental history and resources.

“The communities along New York State’s coastline, including their structures, their residents, their environment and the surrounding natural resources, are products of decisions made over the course of many years. These decisions shaped decades of investment, development and conservation. While the extent of the impacts to coastal communities from a rising sea are not fully known, even the most conservative projections make clear that there will be dramatic changes in this century. Thus, how coastal communities and our state address this collective challenge is important to today’s decision makers. The responses needed to protect communities from the threat posed by sea level rise will take time, and now that the challenges are better understood, government is obligated to protect its citizens while there is time to do so effectively. New York must focus on the smart use of limited resources to address the impacts associated with sea level rise.

The surge barrier alternative.