Mississippi River Delta Subsidence Caused by Compaction

On February 17, 2008, Torbjorn E. Tornqvist of Tulane University and other researchers published a letter in the journal Nature Geoscience entitled Mississippi Delta subsidence primarily caused by compaction of Holocene strata. The research findings suggest that the Mississippi delta is sinking as much as one fifth of an inch per year, but that the sinking is mostly limited to the upper layers of sediment while the land beneath is more stable.

This research suggests that the high rate of subsidence is largely the result of compaction of the shallow sediment deposits from the last 10,000 years in the upper few hundred feet near the surface of the earth. These findings suggest that flood control structures that penetrate through the shallow sediment deposits and rest on the more stable foundation below would not subsidence as quickly.

News articles reporting on this research include: Science Daily in an article entitled Post-Katrina Rebuilding? Mississippi Delta Both Spongy and Stable published on February 22, 2008; and New York Times in an article in a section entitled Observatory with the article title Support for a Theory As to Why Land Sinks Along the Gulf Coast by Henry Fountain published on February 19, 2008.

Erich P Rapp

Study Finds Ice Age Sediment Makes Coastal Louisiana Sink

A recent article in the Geophysical Research Letters entitled, Post-glacial sediment load and subsidence in coastal Louisiana by Erik R. Ivins, Roy K Dokka, and Ronald G. Blom concluded that heavy sediment deposited in the Mississippi River delta at the end of the last ice age has caused coastal Louisiana in the Mississippi River delta to sink. This process is expected to continue for hundreds of years. The process will likely cause the area in question to subside over three feet in the next two hundred years.

The sinking of this land will likely be compounded by a general sea level rise from global warming. These factors will make the area more vulnerable to hurricanes and tropical storms. Of course, the hurricanes and tropical storms will then themselves do further damage to the coastal wetlands.

News Accounts related to this research paper can also be found at;

Associated Press: Sediment Make New Orleans Sink - February 1, 2008

Environmental News Service: Ancient Glacial Sediments Drag Down Louisiana's Sinking Coast - February 10, 2008 

Erich P Rapp

Research on the Decline of the Sediment Load in the Mississippi River Passing through Louisiana

I have repeatedly written about the role of dams, locks and reservoirs in the Mississippi River system and their role in the loss of coastal wetlands in Louisiana. Now, I will provide some research in support of this position.

Dr. Richard H. Kessel, a professor of Geography and Anthropology at Louisiana State University, is the person that has written the most extensively on the decline of the sediment load in the Mississippi River and its role in the loss of coastal wetlands in Louisiana. His papers have included:

1. An Approximation of the Sediment Budget of the Lower Mississippi River Prior to Major Human Modification which was published in volume 17, pages 711-722 (1992) of Earth Surface Processes and Landforms.

2. The Role of the Mississippi River in Wetland Loss in Southeastern Louisiana, U.S.A. which was published in Volume 13, Number 3, pages 183-193 of Environmental Geology and Water Science.

3. The Decline in the Suspended Load of the Lower Mississippi River and its Influence on Adjacent Wetlands which was published in Volume 11, Number 3, pages 271-281 of Environmental Geology and Water Science.

4. Chapter 12 Historical Sediment Discharge Trends for the Lower Mississippi River in Volume II: Technical Narrative of the Outer Continental Shelf Study by the Mineral Management Service, study number 87-0120 which larger document is entitled Causes of Wetland Loss in the Coastal Central Gulf of Mexico.  

The gist of Dr. Kessel's research shows that the suspended sediment load in the Mississippi River as it passes through Louisiana has declined by about 80% since the 1850's. He divides the history of this decline into three periods. These periods are 1) Prior to 1900, 2) a pre-dam period until extensive dam construction began between 1930 and 1952, and 3) the post dam period since 1952. The suspended load decreased 41% before dam construction began and another 51 percent after the dams in the Missouri and Arkansas Rivers were constructed. This change has altered the balance between sediment deposit in the wetlands adjacent to the Mississippi River and the ongoing process of subsidence and global sea level rise. In the most recent period, the rate of sea level rise and subsidence exceeds the rate of sediment deposit. Thus, the coastal wetlands are being lost to open water.

Erich P. Rapp 

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Why Moving Water Transports Sediment and Also Cleans Clothes

When I have questions about basic geology, I refer to Physical Geology by Charles C. Plummer, David McGeary, and Diane H. Carlson. It is an introductory college text with great explanations for everything geology related with many pictures and diagrams. 

For example, why does flowing water transport or carry sediment? The answer is on page 28,

"In a water molecule, the two hydrogen atoms are tightly bonded to the oxygen atom. However, the shape of the molecule is asymmetrical, with the two hydrogen atoms on the same side of the atom. This means the atom is polarized, with a slight excessive positive charge at the hydrogen side of the molecule and a slight excessive negative charge at the opposite side. Because of the slight electrical attraction of water molecules, other substances are readily attached to the molecules and dissolved or carried away by water. Water has been called the universal solvent. Dirt washes out of clothing; water, in blood, carries nutrients to our muscles and transports waste to our kidneys and out of our bodies."

Of course for our purposes in this blog, streams and rivers also transport sediment.

Erich P Rapp.

Federal Liability for Damage to Louisiana Coastal Wetlands - Existential Property Rights?

No one disputes the existence of property rights in coastal wetlands of Louisiana. People own wetland property. Nevertheless, the federal government destroys this property everyday and does not pay damages.  A claim for this damage could be made. Supreme Court Justice Oliver Wendell Holmes said a claim against the federal government required "turning square corners."  That may be so, and this claim is complex, but it exists. One of the purposes of this blog is to discuss  federal liability for damage to the coastal wetlands in Louisiana. That discussion will take many entries. Today, I begin with the philosophical.

When one owns property, what does one actually own. The Louisiana Civil Code art. 462 speaks of "tracts of land" as constituting immovable property. The coastal wetlands are tracts of land, and the government grants property rights in these wetlands.  The coastal wetlands, however, are not typical tracts of land. They exist not as a static thing but as the result of a dynamic process. The wetlands are continuously subsiding, and the flood waters of the Mississippi River were in the past depositing new sediment on that wetlands to offset the subsidence. When that process is disrupted, the land is destroyed. At present, the amount of sediment being deposited by the Mississippi River is not offsetting subsidence and thus, the coastal wetlands are lost to the open water.

I, thus, began wondering if the federal government had ever recognized and protected an interest in real property as a process, and not as a static tract of land. Amazingly, I found an answer to this question, not in a law book, but in a book on the Mississippi River written by landscape architects.

On page 48 of Mississippi River Flooding - Designing a Shifting Landscape by Anuradha Mathur and Dilip da Cunha, the authors describe the Stack Island Supreme Court case. 

In 1995, the United States Supreme Court decided the Stack Island case. The case involved 2200 acres of mud in the water course of the Mississippi River. In the early 1800's, the muddy acres were an island near the bank of the river on the Mississippi side. By the time of the case in the 1990's, supposedly the same muddy acres were no longer an island and were instead attached to the bank of the river on the Louisiana side. Nevertheless, the court found that these muddy acres on the Louisiana bank of the river were the same property that was an island in the river in the 1800's. The New York Times reporter, Hubert B. Herring writing about the case on November 5, 1995 asked, “Existential Geology Anyone?”

The Stack Island case gave me a new vision of the coastal wetlands. The coastal wetlands are not static land washing away. They are a dynamic process of subsidence offset previously by sediment deposit from the Mississippi River. Yet to the casual look, the wetlands are perceived as land just as any other land. With the Stack Island case, now in the eyes of the law, perception is reality or in this case "real property."  The property owners have a property right in the wetlands even if the soil making up the land changes in the dynamic process of subsidence and sediment deposit.  The Louisiana coastal wetlands are an “existential” property and legally protected as such. The wetlands are real property because they are perceived to be real property and not because they are once and always made up of the same soil.

Erich P Rapp

Corps Knowledge of Louisiana Coastal Land Loss Revealed in 1961 Report

The Corps of Engineers claims it learned of Louisiana coastal land loss in the early 1970's.  The Corps' November 2004 Louisiana Coastal Area Ecosystem Restoration Study suggests discovery "in part" from the publication of a 1972 study. No earlier date is mentioned. Discovery in 1972 is not true "in part" or otherwise.

The Corps knew long before the1970's that Louisiana was losing coastal wetlands and that the cause was their management of the Mississippi River. They even knew the wetlands below New Orleans were being lost more quickly than wetlands to the west. As described in my prior blog entry, they also knew the consequences of the land loss on hurricane storm surges. 

Culpability is a function of knowledge. If the Corps knew when it took action that the action would cause damage, they have greater responsibility than if they did not know. Suggesting discovery in 1972 would tend to reduce responsibility for the consequences of  what the Corps did before.

On December 29, 1961, the Corps published: Interim Survey Report Mississippi River Delta At and Below New Orleans. The report was mentioned in my last blog entry about hurricane storm surge. In appendix B of this report on page B-2, it states:

 "The shorelines of the ponds, lakes, and bays within the marshland and the seaward edges of the marshland are being eroded by wave action. At present very little (and in the greater part of the area none) of the sediments carried down by the Mississippi River reach the marshlands. The bulk of the sediments is carried into the gulf and deposited along the outer continental shelf in the vicinity of the mouth of the river. Although wave action is contributing to the destruction of the marshlands, the irregular jagged shorelines in the area show that subsidence has been the dominant factor. Both subsidence and wave attack will continue in the future and unless sediment laden water is introduced into the area to replace material being lost, and to compensate for subsidence, the inland bodies of water will continue to enlarge and the seaward facing edges of the marshland will continue to retreat. This will happen much faster on the east side of the Mississippi River where the marshlands are more exposed to prevailing winds, and there is less to destroy." (emphasis added).

This 1961 report was not an original statement, but it was an eloquent one. More to come.

Erich P Rapp.

Hurricane Storm Surge and Corps of Engineers Response to Time Magazine

The US Army Corps of Engineers responded on August 13, 2007 to the Time Magazine story, The Threatening Storm. The Corps contends that the Time story contains "many errors and misrepresentations" and describes it as a "wreckless disregard for the truth." 

The Corps response appears to contain at least one significant omission. The response states: "The Corps acknowledges that wetlands have a beneficial role in storm surge and wave dissipation, but adequate quantitative information about that role has not been developed." 

At least as far back as December 29, 1961, the USACE published a report entitled: Interim Survey Report Mississippi River Delta At and Below New Orleans. Much of appendix A deals with hurricane storm surge and on page A-11, the report suggests the difficulty in finding meaningful correlations to specific characteristics of hurricanes. Nevertheless, the report reaches a very simple conclusion:

"The study of available observed high water marks at the coastline and inland indicates a fairly consistent simple relationship between the maximum surge height and the distance inland from the coast, as shown on plate A-6. This relationship exists independently of the speed of hurricane translation, wind speeds or directions. The data indicates that the weighted mean decrease in storm surge height inland is at the rate of 1.0 foot per 2.75 miles. The relationship remains true even in the western portions of Louisiana where relatively high chenieres, or wooded ridges, parallel the coast."  An excerpt of the report is linked.

The existence of coastal wetlands south of New Orleans decreases storm surge at New Orleans and the loss of wetlands increases storm surge at New Orleans. The Corps has known that for many years.

Erich P Rapp. 

Dam Removal Is Good For Louisiana Coastal Wetlands

I appreciate the people of Pennsylvania for being leaders in the dam removal movement. Dams and locks damage river systems. Dams and locks in the Mississippi River drainage basin damage the Louisiana coastal wetlands by trapping sediment that would otherwise travel to the river delta and help sustain the coastal wetlands.  

The Harrisburg Patriot-News posted an article on Pennlive.com on August 6, 2007 entitled: Old Dams: Removing these barriers allows waterways to regain free-flow. 

Over 1/3 of Pennsylvania is within the Mississippi River drainage basin. According to the Patriot-News, Pennsylvania has removed 70 dams in the past decade and is removing an additional 3 dams on one creek in the next year. Although the removal of a dam in Pennsylvania will not directly improve the health of the coastal wetlands in Louisiana because so many dams and locks remain in place between Pennsylvania and Louisiana, the dam removal movement should be encouraged.

Officials in Louisiana should monitor the water resource policies of other states. They should encourage good decisions and discourage bad ones. What is done in the Mississippi River drainage basin outside of Louisiana matters, but is often ignored in Louisiana.

Erich P Rapp.

Hard Hitting Time article on Louisiana Coastal Wetland Issues

Kudos to Michael Grunwald of Time Magazine. In an article posted on August 1, 2007,
titled: The Threatening Storm, he has written a strong worded and hard hitting article about the need to rebuild the coastal wetlands of Louisiana. He strongly criticizes the Corps of Engineers and the political process that enables them to make pork barrel decisions instead of well reasoned decisions.

I am particularly impressed with his comments on the need to examine the entire ecosystem of the Mississippi River drainage basin when deciding how to address the problem of coastal land loss in Louisiana. The dams built far upstream from New Orleans have played an important role in the destruction of the wetlands in Louisiana. The officials making decisions about  Louisiana coastal wetland protection and restoration need to look beyond the boundaries of the wetlands themselves when making decisions.

Erich P Rapp.

Extent of Louisiana Coastal Wetland Loss

The New Orleans Times Picayune has created an interactive graphic to depict the scope of coastal land loss in Louisiana.

Select the interactive graphic entitled: The Rise and Disappearance of Southeast Louisiana. The presentation will explain in about seven minutes how the hydrologic cycle described in my last blog entry applies to the Mississippi River and Southeast Louisiana.

Most important when the active presentation ends, you will be left with a map of Louisiana and to the right side of the screen, you will have the ability to select a map of Southeast Louisiana as it existed in 1932, 2000, 2005 and a projection for 2020. Leaving aside what might come to be in the future, alternate views between the map as it was in 1932 and as it was in 2005. What you see will take your breath away.

The interactive graphic is an excellent presentation of the basic geology, but it leaves out an important part of the story. Dams are destroying the wetlands at the mouth of the Mississippi River and not levees. Near the mouth, there are no levees.

Erich P Rapp. 

 

Mississippi River Created Louisiana Coastal Land

The Mississippi River built the part of Louisiana now being lost to the sea. All water running across land carries sediment. All rivers and streams carry sediment. Rivers, streams and the sheet flow over the adjoining land are eroding sediment in one place and depositing it in another.  This natural process has existed as the earth has existed.

Transport of sediment in rivers is part of the hydrologic cycle. 

Water evaporates out of the ocean. The clouds moves over land, and the water returns to earth as rain. The rain runs across the land eroding sediment as it gathers in streams and rivers and makes its way back to the ocean. This description is a gross simplification, of course, because some of the water goes into storage as ground water, in lakes, plants and elsewhere along the way from falling as rain to its return to the ocean. 

As a result of the hydrologic cycle, water transporting sediment in the Mississippi River and depositing it at or near the coast built much of Louisiana over a very long period of time.

The law applies to this process. The transport of sediment in rivers is a natural process that creates a legal relationship between the land along the upstream portions of a river and the lands adjoining the same river system much closer to the ocean. If the process is disrupted, the land building and maintenance stops and as will be described later, the land slowly turns back to open sea.

This blog will show how the law protects property rights associated with the sediment transport process in rivers.

Erich P Rapp.