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the northern section of the (submerged) Chandeleur Island chain photographed from about the same location and altitude on 25th June (top), 2nd July (middle), and 7th July (bottom) Image: Courtesy of Len Bahr |
The latest blow to the highly stressed landscape of the Mississippi River Delta was the Macondo Deep Horizon oil well blowout on April 20 of this year. This explosion killed eleven men and, until being capped on July 15, released an estimated 60,000 barrels a day of crude petroleum a mile beneath the gulf surface and about twenty miles southeast of the closest land.
Absence of plans for responding to such a massive oil release, combined with panic and desperation among coastal residents, created an irresistible political opportunity for action on the part of an ambitious governor and his cabinet.
Jindal and local government leaders seized the emergency created by the blowout to propose a physical barrier "solution" -- to pile up defensive sand berms. The rationale for this action is to intercept oil in waters from the Gulf before it can contaminate the wetlands, the fish and wildlife they nourish, the human population centers they protect, and the delta sediments they hold in place.
The coast of Louisiana frames North America's largest delta, which has been rapidly shrinking and sinking for a century. River channelization, flood levees, upriver dams and coastal oil and gas production continue to take their toll, with a net loss of about 2,300 square miles of inundated landscape per year.
Reduction in the subaerial delta landscape has made southern Louisiana more and more vulnerable to hurricanes. In August 2005, Hurricane Katrina crossed the hobbled coastal landscape to devastate New Orleans and coastal Mississippi, becoming the most damaging American hurricane of the past century. This storm washed away about 200 square miles of emergent wetlands, some of which have since recovered.
About 80 miles of 6-foot-high sand berms are now under construction on the lower east and west sides of the Mississippi River. The total quantity of sand required to complete this project is said to be 56 million cubic yards -- the equivalent of 11.2 times the volume of the Superdome!
Some of this sand is being dredged from the lower river channel, but most is being mined from shoals remaining from sunken barrier islands. Sand dredging deepens the subsurface profile and reduces hydraulic friction that formerly absorbed energy during approaching storm surges. An add-on to the sand barrier project was a proposal to partially fill a number of tidal passes -- places in the shoreline where ocean water makes its way inland on high tides -- using rocks.
State officials justified these projects by dusting off longstanding but unfunded plans to nourish deltaic barrier shorelines on a massive scale, using sand dredged from the river and from 7,000 year-old offshore shoals. The prospect of charging BP for a scaled down version of this concept, sparked by dredging industry lobbyists, resulted in a back-of-the-envelope plan to create new linear sand features parallel to existing shorelines.
The implied motive for these emergency sand and rock projects was presumably to restrict the wind-driven influx of oil-bearing gulf water by "shortening" the shoreline, using partial barricades to choke down pathways for the intrusion of floating oil and trap some oil on sand.
Project proponents virtually ignored the extensive knowledge base of the Mississippi River delta in a rush to implement construction contracts quickly and with as little scientific scrutiny as possible. These proponents are apparently naive about basic hydrologic (tidal) processes. For example, they ignore the fact that reducing the cross sectional area by which tides currently operate will not change the volume of water exchanged during a tidal cycle; it will increase the current velocity (and scouring power) of the water.
Reducing the influx of (oily) gulf water during flood tides would require one of two measures:
1) The tidal exchange volume could be reduced by elevating the bathymetry, raising the bottom profile into the intertidal zone by infilling estuarine shoals, using sediments pumped in on a massive scale.
2) Alternatively, tidal exchange could be eliminated by erecting a continuous floodwall to shut off all tidal exchange -- the so-called Dutch approach.
"Solution 1" would be worthwhile but infeasible and "solution 2" would be destructive and infeasible. The governor's approach, trying to partially block the pathways for oil intrusion, is just foolish.
Minor storms have already washed away portions of the first sand berm segments constructed and permits to infill tidal passes have been denied by the US Army Corps of Engineers.
Len Bahr, PhD, is a former LSU marine sciences faculty member who served 18 years as a coastal policy adviser to Louisiana governors from Buddy Roemer to Bobby Jindal. He edits LaCoastPost. His e-mail is leonardbahr@gmail.com.
Related stories:
[23rd June 2010]
[19th May 2010]
[17th May 2010]
[Comment posted 2010-08-09 10:14:06]
Please email for an updated list of signatories:
Brian Blanton, PhD, Renaissance Computing Institute, UNC Chapel Hill
David M. Bush, PhD, PG, University of West Georgia
Andrew Coburn, Associate Director, Program for the Study of Developed Shorelines
Andrew Cooper, PhD, University of Ulster
George Crozier, PhD, Executive Director, Dauphin Island Sea Lab
Joseph Donoghue, PhD, Florida State University
Roy Dokka, PhD, Fruehan Professor of Engineering, Louisiana State University
Charles H. Fletcher, PhD, University of Hawaii
Chester W. Jackson, PhD, Georgia Southern University
Joseph Kelley, PhD, University of Maine
Mark Merchant, PhD, Director of Research, Louisiana Environmental Research
Center, McNeese State University
William J. Neal, PhD, Grand Valley State University
Andy Nyman, PhD, Louisiana State University
Randall W. Parkinson, PhD, PG, RWParkinson Consulting, Inc
Orrin H. Pilkey, PhD, James B. Duke Professor Emeritus, Duke University
Denise J. Reed, PhD, Director of Pontchartrain Institute for Environmental Sciences,
University of New Orleans
Peter Ruggiero, PhD, Oregon State University
Arthur Trembanis, PhD, University of Delaware
J.P. Walsh, PhD, East Carolina University
Harry Dallon Weathers, PhD, University of New Orleans
The views expressed in this letter should not be interpreted to reflect the views or
official endorsement of the institutions employing the signatories.
[Comment posted 2010-08-06 10:38:56]
"Alan McWright accused me of bias and sour grapes against my former employer Louisiana Governor Bobby Jindal, with respect to my claim that Louisiana state officials have ignored coastal scientists in responding to the Deep Horizon well blowout. Mr. McWright challenged me to back up my claim with the names of specific scientists whose opinions on coastal engineering have been dismissed.
In response I call his attention to a recent letter by Western Carolina University Professor Robert S. Young, and signed by 23 coastal scientists. This letter was sent to Admiral Thad Allen, President Obama's point person on the oil disaster, and posted in LaCoastPost.com.
Len Bahr, Ph.D."
[Comment posted 2010-08-05 15:54:50]
LINK
Wisdom seems to be more difficult to find in rulers these days.....
[Comment posted 2010-08-05 13:36:54]
Who are these researchers you speak of, Mr. Bahr, and how many? Who disagrees with them and you? And how many? Is yours a minority or majority opinion?
The author comes across such that it appears that his way is the only way--that he is right and everyone else is wrong. Maybe that is true and maybe it isn't. His approach here is not very scientific and the entire piece seems much more like a political attack than anything else.
I would like to see a rational, scientific debate on this issue rather than the anti-Jindal rant thus presented.
The fact that he used to work for Jindal makes me suspicious of his motives given his statements.
Were other researchers consulted? What did they have to say? Did Jindal's administration come up with this idea on their own, or was it the result of advice given by other researchers who are in disagreement with Bahr? Well, Bahr doesn't say.
Where is the raw data, sir? Your empirical evidence to back up your claims?
[Comment posted 2010-08-05 12:53:45]
Yet there is one scientist that they will have little choice but to listen to. Mother Nature.
[Comment posted 2010-08-05 11:29:02]
Someone had to move.
The point is that these people were ready to take action when no one else was getting the job done. If you don't agree with what was being called for, that is fine and you are welcome to say so. But we need to lay off the pejorative language about those who were trying to find a solution to a serious problem that no one had faced before. (At least they weren't trying to protect the walrus population by calling a person who had been dead for 5 years!)
[Comment posted 2010-08-05 11:18:42]
[Comment posted 2010-08-05 10:57:22]