Stopping a storm surge superhighway

How a shipping channel intensified the floods in New Orleans

The Mississippi River Gulf Outlet Canal known as MR-GO was designed by the Army Corps of Engineers in the 20thcentury to be a shorter route between the Gulf of Mexico and the Port of New Orleans. Termed by critics as a storm surge superhighway during Katrina, the channel acted as a funnel pushing Katrina closer to the city center. The MRGO also caused a dramatic reduction of cypress swaps and wetlands which act as natural storm surge barriers for the city. Although the MRGO officially closed in 2009, New Orleans is still reeling from the wake of ecological destruction caused by the channel.

TechKnow’s Marita Davison spoke with John Lopez Ph.D., the Coastal Program Coordinator for the Lake Pontchartrain Basin Foundation about where the process of wetlands restoration stands now and why these efforts for natural ecological restoration are so important for the future of New Orleans.

The following was adapted from an interview with “TechKnow.” It has been edited for length and clarity.

TechKnow: Why don’t you tell me about why wetlands are so crucial (to New Orleans)?

John Lopez: In a coastal area like this…they help buffer storm surge and unfortunately in Louisiana, we are a low lying coast. We are very dependent on that coastal buffer to dampen the surge that comes with hurricanes. We still need levees but we need our wetlands to protect our levees.

TK:  Are the wetlands here in New Orleans still compromised?

JL: I think that in the current situation with the improvements they’ve made, that I think that for a 100 year event, we’re probably ok, but we can have great storms like Katrina, and our coast is still in decline so we have an increasing vulnerability even with the improvements that we’ve made.

TK: Why is the coast still in decline?

JL: There’s a whole litany of natural and manmade problems that have contributed to the decline of our coast. Of course we have things like sea level rise and subsidence that is causing land to sink but there are many man made things like canals and of course the Mississippi Gulf Outlet. That was one of the largest in this area that basically cut right through the heart of the estuary here and caused a lot of immediate damage but also a lot of lingering long term problems… this accelerated decline was really man induced.

TK: What are those accelerated declines that we see from the MRGO Channel?

JL: The canal was initially cut right through wetlands so that immediately caused a direct impact just from the footprint of the channel, but then they took material and put it on the side so then they buried wetlands and caused even more loss...It completely changed the plumbing of the estuary here causing a much more direct link from the gulf and essentially increased salt water intrusion and accelerated the amount of salt water that was moving into the coast.

TK: What was the role that the MRGO channel in intensifying the effects of Katrina? 

JL: Before Katrina, the MRGO was already referred to as a surge superhighway…I think because the folks, particularly the folks in St. Bernard where the channel was located, they just kind of intuitively realized it was just a huge corridor that comes through and the original channel was dredged to 500 feet, but the banks eroded.  There’s now some sections that are almost over 2,000 feet wide so that it was this huge waterway coming in… The MRGO allow(ed) surge to the very heart of the city and… in the center of the city is where we had some of the worst failures. 

TK: Can you describe how a storm funnel was created in the MRGO?

JL: The industrial canal runs more or less East/West along the coast and the MRGO runs more North/South. They converge where the surge barrier is so that creates sort of a V or funnel geometry so you have the these two channels that were converging towards the Industrial Canal which is that heart of the city.

TK: Now is it possible to say that had the MRGO not been there, the impacts of Katrina would have been less?

JL: Very clearly, you would not have had probably the large scale failures of in the industrial canal which was a big part of the flooding…It would not have had that big channel that had all the big waves. So yeah, there is no question, if the MRGO had not been there, there would have been less damage, there would have been fewer people who were killed in the storm.

TK: What’s the MRGO restoration project all about?

JL: The corps did what they call a feasibility study after the closure, I mean there was a legal closure, a de-authorization of the channel as a deep draft channel and that was in 2007 and in 2009 they built the physical dams.

TK: Why was it closed?

JL: In the aftermath of Katrina, it became obvious it was this great vulnerability and it did not really have the economic benefits. It finally put the MRGO in a very harsh light and the reality was there all along.  Katrina just put that in focus and so the politics finally swayed that way where we got it legally de-authorized.

TK: What is the restoration project at the MRGO channel?

JL: So the (Army Corps of Engineers), they did the physical closures. They did a feasibility study and that included a whole array of projects. It’s actually three billion dollars’ worth of restoration projects. The direct impact to wetlands from the MRGO is estimated to be at about 27,000 acres so some of that is to actually rebuild some of those wetlands by pumping sediment rebuilding the marsh, rebuilding swap… There is no funding that has been appropriated, and so the project has been authorized and the feasibility study for about not the whole three billion dollars but I think  about 1.5 billion dollars of the MRGO feasibility study has been authorized but there’s been no appropriation.

Marita Davison and John Lopez travel by boat to the MRGO funnel

TK: What are those areas of improvement?

JL:  The central wetlands and it’s something that’s drawn a lot of attention locally…It’s an important area however it is inside the levee and although we’d like to see restoration wherever we can, we are being pragmatic about this and frankly we’d like to see more restoration on the outside of the levee because when it’s on the outside, it helps provide that surge buffer…That’s where you get the environmental and the surge protection.

TK: So there is no way to fully restore that area?

JL: No, in fact like the channel, no one is even suggesting that. For instance, the channel itself would ever be filled up. When they drudged the MRGO , the volume of dredge material was actually more than what was dredge with the Panama Canal…We are hoping to just fix enough that the system can still be sustainable and give us that additional surge benefit.

TK: So if you are not trying to restore back to original conditions, than what is the goal?

JL: I think it’s not practical to restore all the way back. What you have to do is be selective and do things that are kind of the key functional aspects of the estuary, like the rock dam. Basically it was a hydrologic restoration. It stopped that salt water intrusion so that was a very cost effective project. I think it was less than 20 million dollars but it effected probably two thirds of this estuary…We’re looking for things that kind of have that maximum benefit either environmentally or from a flood protection standpoint.

TK: Where does coastal restoration stand now?

JL: Our big takeaway in this Katrina anniversary is that a lot of things have been done and New Orleans is on a good track towards sustainability, but the job’s not done here.  The part that hasn’t been done is the coastal restoration across the whole coast, but in this area that restoration piece is largely about the MRGO.

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