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DESIGN OBSERVER GROUP

During: The Deluge
On Tuesday, August 23, 2005, tropical air fueled by unusually warm ocean water spiraled in an upward, counterclockwise direction over the southeastern Bahamas. The westward-edging, low-pressure column sucked increasing quantities of heated air into the system, growing it sufficiently for the National Hurricane Center to classify it as Tropical Depression 12, and by the next morning as Tropical Storm Katrina. By late Thursday afternoon, Category 1 Hurricane Katrina approached the metropolis of southern Florida with 75-mile-per-hour winds. The system and its heavy rains killed nine people in the north Miami area overnight and then, surviving the jaunt over the Florida peninsula, entered the Gulf of Mexico.

Although the 2005 hurricane season had been accurately predicted as an extraordinarily busy one, tropical activity had disarmingly abated during July and August, and most New Orleanians only passively noted the seemingly weak and distant storm. But awaiting Katrina in the gulf was a gigantic source of storm fuel: a loop current of deeply layered warm water, pulsating in from the Caribbean between Cuba and the Yucatán and breaking off into eddies through the Gulf of Mexico before exiting into the Atlantic between Cuba and Florida. With sea surface temperatures around 90 degrees Fahrenheit and without the reprieve of cooler subsurface waters, a system that made it into the gulf at this particular time would strengthen dramatically.

Computer models at first forecast storm tracks up the Florida peninsula, then westward over the panhandle, then further westward to the Alabama border, where so many storms had landed during the preceding 10-year surge in tropical activity. The farther west Katrina crept, the more energy it drew from the warm loop current, and the more seriously it threatened coastal communities.

Yet as schools and offices closed down in New Orleans on Friday afternoon, most conversation and email concerned weekend plans and next week’s business, not evacuations and possible closures, much less national calamity. It was not until that evening, when the forecast tracks started pointing to the Louisiana–Mississippi border and Governor Kathleen Blanco declared a state of emergency, that citywide attention turned to the heightening threat.

With Katrina a strengthening Category 3 storm and the notoriously divergent computer models now all ominously concurring on a Louisiana landfall, the central Gulf Coast population finally mobilized on Saturday. Emergencies were declared at the state level in Mississippi and the federal level in Louisiana, something rarely done before a disaster strikes. Officials activated the complex contraflow evacuation plan, allowing motorists to use incoming interstate lanes to flee the New Orleans metropolitan area. Many departed Saturday; more left Sunday, August 28, when the system strengthened to Category 4 and Category 5 levels within five hours. By late Sunday morning, with Katrina’s winds hitting 175 miles per hour, nearly all qualified observers confirmed a New Orleans–area landfall. Mayor C. Ray Nagin ordered a mandatory evacuation of the city, though no one seemed to know exactly what that meant, and many could not comply even if they wanted to.

By Sunday night the evacuation window had all but closed, as the initial feeder bands whisked over the city; the only choices now were to ride it out at home or take refuge in the Superdome. Roughly 100,000 New Orleanians — one in every four to five — remained in the city, and of those approximately 15,000 lined up outside the Superdome, expecting at least a safe if uncomfortable night in this shelter of last resort. A solemn and profoundly troubled air prevailed among the reporters and authorities on the local news stations that evening. No one could believe that the proverbial Big One, the topic of endless planning scenarios and stern authoritative admonitions, the butt of countless doomsday jokes and glib clichés, was finally upon New Orleans, all within a summer weekend.

Overnight, Hurricane Katrina’s low barometric pressure and high winds sucked up a dome of gulf water and blew it north and northwestward into the Mississippi Gulf Coast and Louisiana deltaic plain. Shallow coastal depths reverberated the vertically churning water upward, further heightening the dome-shaped, landward-moving surge. Under natural conditions, hundreds of square miles of wetlands would have absorbed or spurned much of the intruding tide. But a century of coastal erosion had cost the region precious impedance, while a labyrinth of man-made navigation, oil, gas and drainage canals served as pathways for the surge to penetrate inland. The funnel formed by the Gulf Intracoastal Waterway (GIWW) and the Mississippi River-Gulf Outlet (MR-GO) allowed Katrina’s surge to swell waters 16 feet above normal levels in the circa-1920 Industrial Canal. Pressure built on the floodwalls and levees and upon the high-organic matter soils beneath them. Seepage began to trickle into the topographical bowls on the other side…

View full version (Places.DesignObserver.com): Delta Urbanism in New Orleans

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“Design Observer was founded in October 2003 by Michael Bierut, William Drenttel, Jessica Helfand and Rick Poynor with design and technology by Ruby Studio.”

Tags: Delta, Design Observer Group, Flood, Hurricane, Katrina, LA, Louisiana, New Orleans, Urbanism

This entry was posted on Thursday, April 1st, 2010 at 10:51 am and is filed under Accountability, Aging Infrastructure, Environment, Infra Views, Inland Waterways, Levees, Local, Seaports, Transit, Urban Planning . You can follow any responses to this entry through the RSS 2.0 feed. Both comments and pings are currently closed.