September 3, 2008

After Gustav

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I have a piece up on the Guardian site with some post-Gustav reflections:

The fact is, due to feedback from human activities, nature has begun to change faster than US government institutions can keep up. There’s a healthy scientific debate over the potential role of global warming in hurricane activity. Some scientists believe a warming atmosphere will lead to more powerful storms. Others say the effects will be minimal. But most everyone agrees that hurricane activity in the Atlantic is in a dangerous, possibly decades-long upswing.

If it is indeed amplified by global warming, we’re going to see some storms unlike any in the past in the coming years. Meanwhile, the lure of living on the coast (and along riverbanks) has put many millions more people in the path of danger, along with their valuable properties, increasing the risk of huge, Katrina-scale losses that will test the insurance industry and the federal government’s budgetary limits.

In order to deal with this, we’re going to have to make some basic changes in how the government operates. Right now, it’s reactive – a major disaster happens (whether a natural catastrophe, or a crash in the financial system, or the food system, or … ) requiring some kind of federal intervention – not just a cleanup operation but some genuine reforms. Congress and the president do something (or not). But I’m guessing that global warming will accelerate the speed at which the environment is changing and quickly outpace all the systems we have in place to make sure people can go on living their lives. We’ll need a government that processes information faster, and acts more quickly.

 

September 3, 2008

More evidence of a climate-hurricane connection

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There’s a new paper out in Nature that adds yet another layer to the debate about global warming and hurricanes (the umbrella term is tropical cyclones). Scientists, including James Elsner at FSU, studied wind speeds in cyclones around the world since 1981, and concluded that the top speeds of the largest storms had increased significantly:

Although there was hardly any increase in the average number or intensity of all storms, the team found a significant shift in distribution towards stronger storms that wreak the greatest havoc. This meant that, overall, there were more storms with a maximum wind speed exceeding 210 kilometres per hour (category 4 and 5 storms on the Saffir–Simpson scale).

This is in keeping with the work of MIT’s Kerry Emanuel and other scientists – many of them using atmospheric computer models – who believe that a warming atmosphere and warming ocean temperatures will result in greater heat-dissipation potential in large storms. This study is significant because it focused on past storms. It’s based on a statistical analysis of satellite data that attempts to smooth out irregularities in measurement caused by varying technologies and techniques around the world. That’s made it hard, for example, to compare trends in the Atlantic basin, where storms have been very carefully monitored for decades, with those of the South Pacific, where government agencies and scientists have been playing catchup.

So: this study, based on hard data, suggests a climate signal already out there, operating now.

This will give some skeptics in this debate pause – many of them are data-driven meteorologists who think that natural cycles and atmospheric effects such as wind shear – sharp differences in wind speeds that can shear off the tops of cyclones – are what really determine the strength of major storms. But the most prominent of these critics, Christopher Landsea, remains, well, skeptical:

Christopher W. Landsea, a science and operations manager at the National Hurricane Center in Miami who has been skeptical of the connection, said the statistical methodology in the new study was excellent, but questioned the underlying data, particularly corrections for data over the Indian Ocean prior to 1997 when there were fewer satellites observing the storms.

Dr. Landsea also said that the increase in Atlantic hurricanes arose from natural variations when decades of active hurricane seasons are followed by decades with few hurricanes. The current period of active hurricane seasons began around 1995.

“The paper has some elegantly calculated statistics, but these are generated on data that are not, in my opinion, reliable for examining how the strongest tropical cyclones have changed around the world,” Dr. Landsea said.

So the debate continues. But this is a provocative addition to it.

 

September 2, 2008

Why did the Industrial Canal fill up?

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There’s a question I’d like to know the answer to. Hurricane Gustav dealt New Orleans a glancing blow, passing it by on northwest course. Yet as the world saw yesterday, the city’s Industrial Canal – the large waterway that runs north-south – filled nearly to the top, and there was some alarming if mostly harmless overtopping due to wind and waves. Why did this happen, and what does it say about the city’s vulnerabilities in future storms?

I sort-of know the answer to this. The Industrial Canal is connects to both the Gulf Intracoastal Waterway and the notorious Mississippi River-Gulf Outlet, or MRGO. The latter is slated for closure because of its role in coastal erosion and (though this is controversial) as a conduit for storm surges into the city. Both these waterways run adjacent to open marshes that are rapidly eroding, and Lake Borgne, which is essentially a large lagoon open to the Gulf. So it’s very easy for a lot of water to get into the heart of New Orleans. It happened in Katrina. Now it has happened in Gustav. The Corps of Engineers plans to build a gate across both waterways where they meet in a giant “V.” That area also became notorious after Katrina because storm surge water flowing into the vertex of the V can rise up very high and overtop levees. And from that point, it’s a straight shot to the Industrial Canal, alongside neighborhoods of the St. Bernard, the Lower 9th Ward and eastern New Orleans.

But if the large flow into the Industrial Canal, and its near overtopping Monday, is due partly to the diminished protection of disappearing marshes, this whole area may be getting even more dangerous. Building a gate may offer a good solution, but it also seems we’re getting closer to a New Orleans-as-Venice scenario, in which Gulf waters are lapping against levees, gates and other structures – a risky scenario indeed.

 

September 1, 2008

Whew

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Hurricane Gustav has spared New Orleans. The levees held. The wind never reached hurricane strength. The evacuation of an estimated 95 percent of the population wasn’t perfect (there were heavy traffic delays) but it worked. Hundreds of buses picked up people without transportation and got them to safety by road or rail.

But consider how lucky New Orleans was. Gustav dealt the city only a glancing blow; its northwesterly course took it over mostly-rural Acadiana. As a result the storm surge never penetrated deep into the city, as it did during Katrina. But a shift of a few degrees east, or a slight change in the angle of approach, and things would have been very different.

New Orleans is still very much in the crosshairs, a city routinely in all-out peril. We are in an “up” cycle for hurricanes, one that may be pumped up further by global warming. Sea levels are rising and New Orleans is sinking. All of this is happening faster than the Corps of Engineers and other institutions can keep up with.

The other question is how much damage Gustav has done to the wetlands that ring the city. Every time a storm hits, it accelerates the erosion process. It undoes painstaking restoration work. It brings the whole Mississippi delta region a step closer to its inevitable death.

 

September 1, 2008

The Plaquemines levee

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A levee in Plaquemines Parish has apparently been overtopped and may be in danger of breaching. This is obviously a serious problem, but to put things in perspective, the affected area, Braithwaite, is quite small, and outside the federal hurricane levee system. Plaquemines runs from east of New Orleans down to the end of the river. As in most of the parish, there’s Mississippi River levee on one side, a road/homes, and then a “back levee” abutting the marshes. It’s this back levee that’s endangered by floodwaters coming from the south and east. Those waters ought to be subsiding now, so the danger may abate.

Interestingly, Braithwaite abuts the Caernarvon Fresh Water Diversion Project, a gate in the Mississippi River that’s opened at strategic times during the year to send river water over the marshes, depositing silt and slowing the progress of coastal erosion. Now the Corps plans to open the gates and allow floodwaters to flow in the opposite direction – into the river instead of out – in order to ease the pressure on the affected levee.

The site is also notorious: during the 1927 Mississippi River flood, Louisiana officials dynamited the river levee at Caernarvon, flooding Plaquemines and St. Bernard Parishes in order to save New Orleans. Residents were promised restitution, but got almost nothing afterward. And blowing up the levee turned out to be pointless – thanks to levee breaks upstream, New Orleans would not have flooded. This is one source of the persistent rumors about dynamiting levees that resurfaced during Katrina.

Update: MSNBC is reporting that opening the Caernarvon gates worked; the water level has dropped and the levee is intact.

 

September 1, 2008

Overtopping in New Orleans

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Not good: water has begun to overtop floodwalls in the New Orleans Industrial Canal. This is happening in the Upper 9th Ward – i.e., on the other side of the canal from the Lower 9th. As the picture and the name of the canal indicate, this is an industrial area of town. The floodwalls in question have been fortified post-Katrina. Corps officials are saying that this is not true overtopping – i.e., it’s mainly waves being pushed over by wind.

However, indications are the water is still rising. In Shell Beach, which lies to the east, water levels have reached 10 feet:

The Industrial Canal connects both to Lake Pontchartrain and to the eastern marshes where Shell Beach is, so the water level has the potential to keep rising as the storm moves through. Also, once water starts coming over the top of a levee or floodwall, its capacities are obviously exceeded; structural problems begin to mount and the risk of a breach increases. Fortunately, these floodwalls are equipped with concrete splashpads on the dry side so that water flowing over them won’t erode the foundations.

Update: Corps officials in Baton Rouge say they believe the wall will hold. Water levels in the canal will likely drop because the water will flow into Lake Pontchartrain, where the water level has not risen appreciably (which is why they have not had to shut the new floodgates on the drainage canals that lead into city neighborhoods). Gustav’s winds have been pushing water into New Orleans from the south and east. But to get into the lake, the Gulf storm surge has to travel both farther north and then a lot farther inland. That would require powerful, sustained easterly winds. That’s why the lake isn’t filling up – Gustav is too far to the west, and moving away. Also, as you can see from the Shell Beach graphic, the water level to the east of New Orleans appears to have topped out at 10 feet. As Gustav moves on, the winds will shift to the west and begin pushing that water back out to sea.

Later update: The water level in the Industrial Canal (AKA the Inner Harbor Navigation Canal – that is the official name, but in NO it’s universally known as the Industrial Canal) is dropping, though the TP reports there is still some wave overtopping occurring.

 

August 31, 2008

The storm surge

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The forecast continues to incrementally improve for New Orleans. The Corps of Engineers’ latest storm surge projections show a lower risk for New Orleans:

The latest prediction of reduced Hurricane Gustav storm surge should be good news for the Industrial Canal and St. Bernard Parish levees, but may still potentially put water over deficient levees on the west bank of Jefferson Parish, the Army Corps of Engineers’ ranking officer said Sunday.

Lt. Gen. Robert Van Antwerp, the corps’ chief of engineers, also suggested that only one of three New Orleans outfall canals still have to be closed against the surge.

St. Bernard Parish lies to the east of New Orleans and would bear the initial brunt of storm surge flooding driven by Gustav’s counterclockwise winds. The Industrial Canal bisects the city, running north-to-south. It breached in several spots during Katrina and repairs and restoration are ongoing. Officials were worried that high water could find remaining weak points, posing danger to adjacent neighborhoods. It also appears that the storm surge heights along the south shore of Lake Pontchartrain won’t be that severe, which is why they may not have to close all three canal floodgates.

There’s a much larger risk to the sprawling west bank suburbs. The storm will pass much closer to them, driving floodwaters into Barataria Bay and northward into communities. The levee system down there is an incomplete patchwork.

Update: Apparently the state’s modeling shows the risk for the west bank suburbs also declining.

Gov. Bobby Jindal said storm surge modeling indicated water levels could be much lower on the West Bank than the weather service announcement predicted, and surge would not be likely to overtop levees in Jefferson Parish.

Fingers crossed that these trends continue.

 

August 31, 2008

The politics of Gustav

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The juxtaposition of Hurricane Gustav and the Republican Convention has naturally set off lots of idle speculation about the political impact of the storm. It’s the perfect Drudge convergence: disaster and partisan politics. God is on the side of the Democrats! (former DNC chair Don Fowler) There is a God after all! (Michael Moore) It’s an opportunity for Republicans! (the Associated Press).

I am grateful the storm has given the Republican Party and the McCain campaign a chance to show a little restraint for a change. But obviously nobody can predict the political impact of a storm before it happens, because that depends on the real, physical impact. And that’s what we should be worried about. Lives and communities are literally at stake here.

One note, though: if a disaster has a political impact, it’s almost always negative. If things go well – if FEMA doesn’t screw up terribly, if people are rescued in a timely fashion – that’s good. Or great, considering the recent record. But historically, those situations have not been huge political pluses because that’s what is supposed to happen. It’s when things go wrong – when people’s expectations are not met – that you see political impacts. Very negative ones.

This is a paradox of disaster management that the Bush administration learned the hard way. Though it takes a lot of effort to put robust emergency management policies and institutions in place, the political upside is minimal. If the emergency plan works, you won’t get much credit after the storm, at least among the population at large. If things go south, though, the political downside can be huge. That’s why presidents (and governors, and mayors) neglect emergency management at their own peril.

So, it would be nice if everybody speculating about this would just shut up and let FEMA, the National Guard, the Coast Guard and other responders to their jobs. If they do them well (and New Orleans is still intact afterward) this will likely cause few ripples on the national political scene. Which I’m sure is perfectly OK with both McCain and Obama.

 

August 31, 2008

Category 3

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A measure of good news: Hurricane Gustav did not strengthen as much as expected over the Loop Current and is expected to remain a Category 3 storm. The forecast track has also shifted slightly to the west, away from the New Orleans area. Of course, this could change in the next 18 hours.

 

August 31, 2008

Gustav weakens, but not for long

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Hurricane Gustav weakened somewhat overnight, but is expected to strengthen rapidly again – thanks to the warm waters of the Gulf’s loop current – before striking the coastline midday Monday. Meanwhile, the forecast track again shifted incrementally eastward. Each increment increases the likelihood of hurricane-force winds and levee-topping storm surges in the New Orleans area, especially in suburbs on the west bank of the Mississippi River (i.e., south of the city proper) which abut marshes and where the levee system is incomplete. This is bad.

 

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