In the days following one of the worst natural disasters to strike American soil, national media outlets portrayed Hurricane Katrina as a two-fold story: juxtaposed on top of the images of human suffering was the commentary track of bureaucratic malfeasance.
As the empirical work of determining what exactly happened and what caused such massive damage is being undertaken by professionals and academics alike.
Versed in the language of storm surges, load failures and the Saffir-Simpson Hurricane scale, University scientists have offered their insights on Hurricane Katrina and the damage that has followed in its wake.
“According to our models, we are only halfway through this year’s hurricane season,” was the first thing on Perry Samson’s mind, a professor in the department of Atmospheric, Oceanic and Space Sciences. “We expect more, some of which could be the size of Katrina.”
“The power of a hurricane is almost entirely a function of how warm the ocean is beneath it,” Samson said. Having had all summer to warm up, the Gulf of Mexico and other large bodies of water are only now reaching their peak temperatures.
“All their energy comes from water that is evaporating off the ocean, so the warmer the water is, the stronger the hurricane will be,” Samson said.
Katrina itself was an uncommonly large hurricane. While originally thought to be a moderate storm that would track up the Florida panhandle, the inconstant Gulf Stream winds pushed it into the Gulf of Mexico, where it lingered, building up energy and gathering intensity.
By that time Hurricane Katrina had reorganized itself into a much fiercer beast, placing it between a four and a five on the Saffir-Simpson scale, which rates hurricanes from one to five based on wind speed.
The other metric used on hurricanes is based on the area of land they cover. “At that point it was the fourth largest hurricane in terms of size in Gulf history,” Samson said. When it crashed into the Gulf coast, Katrina stretched all the way from Florida to Texas.
At that point, the coastal buildings bore the brunt of wind speeds of about 140 to 150 miles per hour. Most modern buildings are designed to withstand winds of up to 145 miles per hour, according to James Wight, a University professor of civil and environmental engineering.
“The modern high-rises did okay, but it was the low-rise, nonengineered buildings that did suffer,” Wight said. “The tide coming in the front end of the hurricane did wipe out a lot of wood structures.”
Wight added the incoming force of water, or hydraulic surge, was what wreaked much coastal damage in states such as Mississippi.
The devastation of hydraulic surge is compounded during times of high tide, and Katrina was so massive and so slow moving that “both low and then high tide occurred as the thing was moving on shore,” Samson said.
As the tide surged in, “water – pushed into New Orleans and Lake Ponchartrain,” Samson said. At that point, the only thing keeping back the lake’s waters from pouring into the adjoining New Orleans was a 300-mile network of levees.
“If a hurricane makes landfall around that area, the counterclockwise winds will put a lot of stress on the levees,” said Nikolaos Katopodes, the chair of the civil and environmental engineering department.
“The levees were upgraded back in 1965 to withstand a level-three hurricane,” Katopodes said.
“It was clear there was a plan in place to increase the level of protection, which would have required an increase in levee height,” Steven Wright, a professor of civil and environmental engineering, said.
“The levee was constructed of a concrete wall on top of an earth-built levee,” Wright said. “My understanding is that one failure was in major part caused by the impact of a barge with the levee itself.”
And yet, along those 300 miles, “only three points, the weakest points, failed in the levee system,” Katopodes said.
As widespread and visible as the current damage is, scientists are wary to draw too many conclusions from this single disaster.
“To say any particular storm was so big because of global warming is a stretch,” Samson said.
Which is not to say that there weren’t other long-term factors involved.
“Every year the American Society of Civil Engineers gives the U.S. infrastructure a report card,” Katopodes explained. “For the last five years, the country has gotten a ‘D’ .”
“It’s the basic maintenance issue … It was clear there was a plan in place to increase the level of protection, but the government had other priorities,” Wright said.
The prediction of the hurricane was state of the art, you couldn’t have wished for anything better,” Katopodes said. “It’s absolutely scary.”
“They knew how tall the levees were, they ran the models, they knew what would happen if this kind of storm came in,” Samson said. “What are we gambling with next?”