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Louisiana suffers flooding of historic proportions, and many see climate as a driver

Louisiana suffers flooding of historic proportions
REUTERS/Jonathan Bachman
Chris Landaiche looking out to his flooded backyard in Sorrento, Louisiana, on Sunday.

The river rose all day, the river rose all night.

Some people got lost in the flood. Some people got away all right.

The river have busted through clear down to Plaquemines —

Six feet of water in the streets of Evangeline.

 — Randy Newman, “Louisiana 1927.”

Though strangely slow to grasp the enormity of last week’s flooding around Baton Rouge, national media have surged back in recent days with solid and sophisticated reporting on a weather/climate disaster of historic proportions.

By Wednesday the Red Cross had officially characterized the flooding as the worst U.S. disaster since the Hurricane Sandy in 2012, which killed 100 people in the northeastern U.S. (and more than 130 more in other countries).

At the time of the Red Cross announcement, high water in the Baton Rouge region had claimed just 11 lives while prompting rescues of 20,000 residents and damaging an estimated 40,000 homes. But that was early on.

By the weekend the death toll had climbed, mercifully, only to 13. But the number of rescues had grown by 50 percent, according to the Associated Press on Saturday, to more than 30,000 (not counting an estimated 1,000 pet rescues). So had the count of damaged homes, to 60,000.

Even that latter figure may prove to be a major understatement. National Public Radio checked in with an official of the Baton Rouge Chamber of Commerce and found that the eventual figure is likely to be closer to 110,000.

Sixty thousand, Ryan Kailath explained, was merely the number of homes that had already been reported damaged by their owners in the midst of chaos; 110,000 was the total number of homes in the low, flat floodplain east of Louisiana’s capital city.

And across Livingston Parish — ground zero for flooding of the Amite and Comite Rivers — it was already estimated that three homes out of four had been damaged or destroyed, according to the New Orleans Times-Picayune.

The parish is also the center of what the AP referred to as “a uniquely Louisiana problem” — the watery unburial of coffins from vaults that sit mostly aboveground because of the terrain’s high water table.

At least 15 cemeteries across seven parishes have had disruptions, the Louisiana Department of Health reported Saturday, although they don't yet have an estimate of how many graves, tombs and vaults have been damaged.

The department is reaching out to affected parishes to do assessments. In most cases, the disinterred caskets and vaults are still within the territory of the cemetery, although one casket ended up in a nearby backyard.

More rain than 1927

Measurements of rainfall from the exceptionally slow-moving storm varied some with location but were consistently huge,  typically summarized as more than two feet of water in less than three days. Thirty-nine hours seems to be the general outside estimate for the rain’s duration, starting late Thursday or early Friday depending on location.

But over at Mashable, I found this intriguing statistic: In the Livingston Parish community of Watson, 31.39 inches of rain was recorded during the event.

Although the storied flooding of 1927 took place over a much larger area, of course, the rainfall it brought to southern Louisiana is described at Greenwire as having been 15 inches in 18 hours. That means the beleagued residents of Watson, and maybe some other places, may have endured a downpour of the same rate as 1927 but for up to twice the duration.

Elsewhere, ClimateWire reported:

A river gauge near the city of Denham Springs recorded a high-water mark of 46.2 feet, according to the U.S. Geological Survey, which has monitored the Amite River for at least 95 years. The previous record was set in 1983 when the river surface was 4.7 feet lower, said Frank Revitte, warning coordination meteorologist at NWS New Orleans/Baton Rouge.

"That's very significant," he said. "Normally you break a record by just a small amount, but that's a 4- to 5-foot difference; that is considerable."

Rainfall records were also set. At Livingston, 21.86 inches of rain fell over two days. The probability of that much rain in any given year in that locality is 0.1 percent. That makes this a once-in-a-1,000-year event. In New Iberia, the rains were a once-in-500-year event.

ClimateWire, by the way, was among the publications speaking most softly about the role of climate change as a driver of the Louisiana deluge.

It called the storm “a freak event driven by the atmosphere and the ocean” and concluded that while it fits with larger patterns of heavy rainfall events growing larger and more frequent, “dynamic weather systems are governed by an element of randomness that has not yet been overwhelmed by climate change.”

Others, of course, are drawing tighter connections.

A pattern of extreme rain

An assessment in Scientific American noted that, “Over the past year alone, catastrophic rain events characterized as once-in-500-year or even once-in-1,000-year events have flooded West Virginia, Texas, Oklahoma, South Carolina and now Louisiana, sweeping in billions of dollars of property damage and deaths along with the high waters.”

Speaking to Inside Climate News, the Texas Tech climate scientist Kathryn Hayhoe explained that the Louisiana storm resulted from one factor clearly related to climate change (increased moisture content in a warmed atmosphere) and one not so much (the eerily slow pace of the storm’s movement across the Baton Rouge region).

"This storm is a good example of why we care about a changing climate ... because Louisiana is a place that is already at risk of flooding and climate change is taking the risk that we already face, and it's exacerbating" the threat.

These storms have all happened as the planet is on track to have its warmest year on record. (In fact, July was the hottest month ever recorded). "With such a warm year, you're going to see much higher-than-average sea surface temperatures," Hayhoe said. Those water temperatures, in this case the Gulf of Mexico where the storm system formed on Aug. 7, mean the air above it has more than its usual share of water vapor, Hayhoe explained. 

In the usual chide-the-victims portions of the coverage — and here the echoes of Hurricane Katrina were loud and clear — some publications asked why the people of Baton Rouge hadn’t been better prepared to meet the danger as it arrived.

There was the usual back-and-forth about the adequacy of public-safety alerts but the more interesting points (at least to me) were about the limits to what even excellent preparation could achieve in a time of such big changes in weather patterns, the underlying climate, or both. Back to Scientific American for a moment:

One of the first shifts that must happen, many experts in hazard mitigation say, is to stop using the climate of the past to plan for the future.

“One of the great challenges is to recognize that a lot of communities, a lot of cities, a lot of human settlements in general were designed to reflect the climate of the past,” said [Gavin] Smith [director of the Department of Homeland Security’s Coastal Resilience Center of Excellence],  who also served as the director of the Mississippi Office of Recovery and Renewal after Hurricane Katrina.

“These issues, they are happening and they’re going to become worse, and the changes are occurring within a context where we’ve designed cities to reflect a previous climate,” he said.

And now over to The Atlantic’s City Lab:

All the diversion canals, freeboard standards, and flood insurance policies in the world would not have entirely saved Baton Rouge from the damaging effects of 25 inches of rain in three days. It’s a stunning amount, anomalous by every measure.

“This was above and beyond anything that I think you could really could prepare for,” says Melissa Daigle, a resiliency specialist with Louisiana Sea Grant Law & Policy Program, who lives a few minutes away from (and a few feet above) some of the worst-flooded areas in the city.

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Comments (7)

We are moving into an era

We are moving into an era where the effects of climate change cannot be denied. It will be in the front of everyone from now onwards.

Even in Minnesota we have expereienced extraordinary rainstorms multiple times this summer. I recall few rainstorms of a couple of inches that were big news when the happened. But 6 inches (plus) rains, multiple time this summer in Minnesota alone ? Extraordinary !!

And further, the rains happen more in downpours, with few instances of a rainy period of light to moderate rain lasting for days.

A warming climate allows for thair to carry more moisture. The air over Louisiana had a record amount of moisture in it. Record warmth of gulf and pacific water sent their moisture skyward. And a circular hurricane air movement ensued where air moved south into the gulf and returned north with fresh precipitable moisture. That pattern held for days.

It basically was a low speed hurricane stuck perched on the gulf coast where the revolving wind system replenished moisture and guaranteed record rainfalls in the area. A similar system had set up in the Tampa/Orlando area earlier and also led to record rainfalls. The ability of a storm to stay stuck in one place for a longer time is a testament to the dropping temperature difference from the north pole to the equator. That greater temperature difference drove the jet-stream winds firmly from west to east and pushed weather systems with it. The higher temperature in the arctic have resulted in a slower and more meandering jet stream where weather patterns can hold for longer than previously and big pockets of southern heat and moisture can be brought further north, resulting in the epic rains that we now see.

But hey, it's all a conspiracy and the climate scientists get a check each time there is an excessive rainstorm event, doncha know...

It seems that this changed world has something new to show us, which portends for some very difficult condtions on

Climate Change

And then there is the Hubbard exception, "...Who’s going to keep spreading nonsense about global warming? That’s why I have to vote for Trump.”

A little geologic history

In the geologic past, the Gulf of Mexico was a larger shallow sea. It covered southern Alabama, Mississippi, Louisiana, and East Texas. It became enclosed, evaporated. and left a big salt layer known as the Luann salt. The sea returned and became smaller and deeper. Its former sea bottom is now a big flood plain. Nothing to do with so called Climate Change.

....In the geologic

....In the geologic past..

And it is all about the time scale. The changes you mention took millions of years. What is happening now is within a couple of generations.

Advice

Don't build on flood plains. They can get wet in a short time.

You might want to review the

You might want to review the ancient Western Interior Seaway--the Twin Cities would be right on the shore. It may be that way again some day with enough melting of the ice caps.

http://www.fossilmuseum.net/fossil-art/maps/seaway/seaway100mya.htm

Sea level

We are about 850 feet above sea level. Not enough ice for the water to get to us.