This page, added on to the hurricane review on page 14-10, surveys the history and effects of Hurricane Katrina, what is now cited as inflicting the costliest natural disaster ever to happen on the mainland United States. Hurricanes Rita and Wilma, occurring later the same year (2005), are also examined. The role of remote sensing is emphasized, especially as it pertains to the types of damage produced by this devastating storm.
The year 2005 has witnessed an extraordinary hurricane season. As of December 31, 27 storms ranked from tropical depression to fullblown hurricanes (9 of those) had developed in the Atlantic and were given names (the male/female naming system has been exceeded, so that the secondary system of Greek letters is now in place). The devastation to Atlanic and Caribbean islands, the Atlantic Coast line, and states and countries in the Gulf of Mexico is greater than any past time for which records are kept. The cost in 2005 U.S. dollars far surpasses any previous year. By far the worst destroyer is Hurricane Katrina - now rated as the worst natural weather disaster to ever beset the United States. This first illustration summarizes the 2005 storm history in the Atlantic and Gulf through November 1 (more detailed tracks for several earlier storms including Katrina appear below):
On August 29, 2005 and for days before and after, meteorological remote sensing experienced one of its "finest hours" as a monitoring system when the southern U.S. was subjected to arguably the worst natural disaster in North America on record. Hurricane Katrina (the second time this name was use; one called Katrina struck Central America in 1999) slammed into the Gulf Coast as a Category 4 storm (but later analysis has determined it to be a high Category 3 at New Orleans) which caused extraordinary havoc in and around the Crescent City. As of this writing, the death toll in Louisiana stands at 1586 - most at and near New Orleans. Damage greatly exceeds $100 billion dollars ($55 billion covered by insurance companies), making it even more costly than Hurricane Andrew. Most of New Orleans (around 75%) was underwater for nearly a month after storm surges from Lake Pontchartrain breached several dikes, and anarchy was unfettered for several days. The effects of this massive storm, whose large size (width) accounts for huge area of devastation, have already exceeded the Category 5 Hurricane Camille in August, 1969 - reputed then to be the worst storm catastrophe as judged by the material destruction to hit the U.S Gulf Coast. Towns including New Orleans, Biloxi, and Gulfport may require years to rebuild.
On this special add-on page we will review the story of this national tragedy. First, let's establish the setting through this MODIS image that shows most of the areas hardest hit by Katrina; New Orleans is just below Lake Ponchartrain:
By the end of August of 2005 three significant hurricanes - Dennis, Emily, and Katrina - had hit Florida and/or the Gulf Coast. Here is their tracking history
Katrina, by far the worst of the trio, may have begun as Tropical Depression 10 by mid-August in the tropical zone within the south-central Atlantic. (Already, with the main hurricane season still ahead through October, there have been an abnormally high number of such tropical disturbances, some developing into hurricanes such as Emily and Dennis.) That depression apparently dissipated but may have re-emerged as Tropical Depression 12, located several hundred kilometers southeast of the Bahamas. The space image below shows this depression, now named Katrina, in this area just before it became a Category 1 hurricane:
The new hurricane side-swiped the Bahamas to slam into South Florida near Miami. As it passed the Bahamas, the Quickscat satellite obtained this picture of the increasing wind velocities:
At this stage, the hurricane had yet to develop a distinct eye:
Cloud height data from TRMM is shown in the next image:
This NOAA satellite image, colored to show general ranges of wind speeds, shows Katrina had developed an eye which passed just north of Miami on August 25. Wind damage was moderate but widespread flooding inundated whole towns. Damage costs amounted to less than $2 billion; 12 lives were lost mainly by drowning.
Katrina looked poorly organized and weakened as it entered the Gulf of Mexico. At first it seemed headed westward towards open Gulf water.
However, Sea Surface Temperatures (SST) were quite warm in the Gulf and steering currents began to divert Katrina's path towards a northwest, then a north trajectory.
As it moved northward, Katrina quickly intensified into a Category 2, then 3, then 4 strength hurricane. Rainfall seen by TRMM indicated that it would be a floodmaker when it struck land.
Residents from west of New Orleans and east through Biloxi and Gulfport in Mississippi, and further east through Mobile, Alabama and Pensacola, Florida were first warned to "batten down", and then urged to begin a mass evacuation. More than three hundred thousand escaped New Orleans, spreading out northwards.
Finally, nearing land, the size of Katrina expanded and its winds topped 155 mph, making it for a short time a Category 5 hurricane. At one stage, its internal pressure reached 902 millibars, 4th lowest recorded from Atlantic storms. Evacuation on Saturday and Sunday accelerated. Here is a NOAA image of the storm at this stage.
No series of still pictures can give a "you were there" idea of the storm's fury. Those who were there attest to its frightening destruction. Here is just one that shows something of the wind and rain effects on a stretch of the Gulf Coast.
The storm, as it passed onto the Mississippi Delta, weakened to a category 3 and steering currents moved it just east of New Orleans, where it made landfall in the morning hours of August 29. Thereafter, it moved inland, constantly weakening, into the Tennessee and Ohio Valleys, into western New York and then Canada. The high level damage it inflicted on the southern coast covered 237000 square kilometers (90000 square miles).
Observations made by the AIRS instrument on Aqua (see Section 16) show the temperatures of the cloud deck above Katrina as it began to dissipate. The oranges in the images indicate still considerable moisture causing the heavy rains in the central U.S. The blue shows lower temperature that correlate with the "drying out" of the central storm, hence less rainfall.
The greatest urban calamity in American history resulted from the passage of Katrina on shore. Let us set the stage for what happened to New Orleans by first reminding you of how this city appears from space (also, refer to the write-up on page 4-2). Below the space image are three maps - one giving a regional geographic perspective; the second, the central parts of the city; then a map of the Parishes (Counties) around New Orleans.
At first, the remaining residents of New Orleans - called "The Big Easy" or the "Crescent City" by the tourist interests - believed they had "dodged the bullet". Word came soon that Gulfport, Biloxi, and other Gulf towns had experienced heavy wind and water damage. There the storm surge reached 8.7 meters (29 ft), largest on record from an American hurricane. Then, the levees coming off Lake Pontchartrain started to break, spilling the top 2/3rds of a meter (two feet) of its water into New Orleans (much of the city is in a topographic "bowl" just below sealevel), and eventually submerging up to 80% of its area to depths of 1 to 6 meters (3 to perhaps as much as 19 feet). These pictures show some aspects of this levee collapse
Hundreds of photos of flooding in and around New Orleans have been published:
This map shows the extent of maximum flooding and the dikes that were breached (largely a failure of inadequate levee construction which eroded away its material as storm surge effects pressed against the structures). Note that neither the dikes along Lake Pontchartrain or the Mississippi were breached directly, only those along the canal system within the city.
The next two higher resolution (10 meters) images were obtained from NASA's EO-1 satellite. In both, flooded areas are indicated by black tones in the streets. The first image shows that the somewhat higher land in central (downtown) New Orleans remained dry - never flooded. This includes the famed French Quarter, which can trace its origin to the founding of New Orleans in 1718 when French pioneers built the first settlement on the highest ground adjacent to the Mississippi River (even in its early decades, the citizens experienced enough flooding to erect protective earthen levees). The second shows how north-central New Orleans was flooded by failure of the east 17th Street Canal dike but the west dike held up keeping that part of New Orleans from flooding.
Experts had known for years that a powerful hurricane could breach one or more of the (obviously too low and outdated) levees raised against Lake Pontchartrain and the Mississippi River. Their recommendations to upgrade these levels were ignored (in part for unwillingness to commit funding). What happened in the case of Katrina was that counterclockwise winds on the west side of the hurricane's eye (to the east) pushed against the levees from the north as a storm surge. Water from Lake Borgne, which lies in a swampy area, was particularly effective in inundating the Lower 9th District. Here are two illustrations that depict the danger that previous computer models predicted would face much of New Orleans that was below sealevel. This cross-section explain why the French Quarter (St. Louis Cathedral, on left) and adjacent areas did not flood - they were five feet or more above sealevel. :
After a "mandatory evacuation" order was given on Sunday, August 28, a quarter of a million people left town. But more than 130,000 citizens of New Orleans stayed behind, some choosing not to evacuate but most without the means (such as autos) to escape on short notice. As waters rose, most of these were driven from their homes, or had to be rescued by air, or drowned. Over much of the first week, the search and rescue operations proved woefully inadequate (the "blame game" fingers all levels - federal, state, and local - for poor execution of existing plans. At the federal level, FEMA (Federal Emergency Management Agency) shouldered much of the criticism, particularly against its top management which included key decision makers with little emergency handling experience.
The famed Superdome in New Orleans was opened to shelter about 15000 people. That dome had it outer cover pealed off and some panels broken, causing roof leaks. The Superdome soon became uninhabitable and its refugees (and many at the Convention Center) were moved from New Orleans by bus. For several days, before National Guard and federal troops arrived to support the beleagured town police, looting, shooting, and other forms of anarchy ruled the passable streets.
The New Orleans Convention Center also served as a refuge. Both large facilities failed as shelters, largely because of inadequate bedding, food, and toilet provisions. As help finally arrived, and some semblance of disaster management took hold, these two buildings were evacuated. In time more than 400000 citizens from the most affected areas on the Gulf were moved to Texas and many other states. Tragically, as recovery operations hit their stride, it was discovered that several hospitals and nursing homes contained scores of dead who were overlooked during the critical evacuation hours.
Surprisingly, the Lake Pontchartrain Causeway - longest of its kind in the world - sustained little damage: a tribute to its excellent engineering (in the open waters of the lake the storm surge effect was reduced). But the shorter (12 km; 8 miles) Twin Spans Bridge, part of Interstate 10 from Slidell, LA to New Orleans, being in a more confined part of the Lake, was heavily damaged with sunken or separated span blocks, and will need nearly complete rebuilding.
To the east in Mississippi, the double span bridge on Highway 90 between Bay St. Louis experienced a west-leaning downdrop of most individual segments of the concrete bridgeway:
Turning now to additional contributions to damage assessment using space imagery: Most earth-observing systems returned useful and dramatic pictures. Terra's MODIS obtained the first, smaller scale view from space of the flooding of New Orleans:
Landsat-7 checks in with its own partial scene view of flood and preflood imagery of New Orleans.
A SPOT-2 false color image taken at 20 meters on August 31 shows that most of the flooding came from failure of levees associated with Lake Pontchartrain. Areas close to the Mississippi River were largely spared.
Digital Globe's Quickbird satellite obtained the first high resolution views of flooding in New Orleans. The top image is one taken in March of 2004, the bottom is the same area seen on August 31 right after the hurricane, with flooded ground appearing black.
Additional Quickbird images for August 31 show in more detail the downtown area, which suffered less flooding, and the Chalmette suburbs, which was completed submerged along its streets, with water entering at least the ground floor of the majority of homes.
The Orbimage satellite produced several black and white images that really show the boundary between flooded residential areas and the downtown business district and industrial areas along the Mississippi River:
Orbimage-3 obtained a view of Tulane University before the flood, and again after the campus was almost totally inundated.
New Orleans could not start rebuilding until the floodwaters are drained off, after which electricity, sewerage, and water systems have gradually been brought back up. This lovely city has suffered a catastrophe but the townsfolk and the federal government have vowed to restore most of the city. New and better floodwalls will need to be built and adjustments to the Mississippi River channel system will be designed to restore some of the protective delta wetlands.
Now lets take a tour of some of the damage along the Mississippi coast. First, Quickbird images of part of Biloxi.
The rest are ground and aerial views along the Louisiana and Mississippi coastal areas; read the captions for details.
The delta wetlands at the mouth of the Mississippi and many offshore islands were either washed away or flooded. For example, Chandaleur Island, off the Mississippi state coast, about 160 kilometers (100 miles) east of New Orleans experience this near total destruction:
In addition, some land segments at the Mississippi's mouth had homes on them, many to house the families of workers on the offshore oil drilling platforms (a large number of these were severely damaged). This curved land within the distributaries saw complete destruction of this pre-hurricane housing:
As of September 20, the area of flooding in New Orleans was, through a massive pumping effort, reduced from 80% to 40%. By month's end, almost all water was gone - well ahead of schedule - only to experience some return in the worst hit 9th Ward when Hurricane Rita struck (see below).
In retrospect, these facts or strong surmises can be recorded here: 1) Katrina is now called the worst natural disaster to hit North America in terms of area affected and dollars needed to recover; original estimates of insured damage at $25 billion proved quite low, new estimates range beyond $60 billion (compared to $43 billion for an inflation-adjusted Hurricane Andrew) and will probably rise another $120 billion when other sources of recovery funding (federal; private); experts in disaster assessment conjecture a real total cost as nearing $200 billion when lost job income, business failures, and industrial shutdowns are included; 2) up to a half million refugees are spread over many states following near-complete evacuation of New Orleans and other areas; unfortunately, for the desire for full recovery, many displaced citizens as of early 2007 are defiantly contemplating not to return; 3) full reopening New Orleans has taken months just to get the situation in control before years of permanent rebuilding; however, about 180,000 were told they can return by early October, 2006 to those areas that avoided flooding; 4) authorities knew that a Category 4 or 5 hurricane would likely flood New Orleans, yet did almost nothing to improve its protection with better levees; 5) the Search and Rescue phase and evacuation/refugee care efforts were slow, especially since the pre-hurricane studies had predicted the problems so that a quick response should have been in place; the Afro-American community bore the brunt of this failure; 6) the disruption of offshore Gulf oil production (more than 140 platforms damaged and 12 destroyed by Katrina and the later Hurricane Rita [see below]) and the shutdown of the many refineries along this part of the Gulf Coast have accounted for part of a sharp increase in U.S. gasoline prices and a period of scarcity (mainly in states east of the Mississippi where most of the pipelines were directed) Mayor Ray Nagin of New Orleans was the first to forecast a possible death toll rising to 10000. Mercifully, this death toll has proved to be much lower, with the full number in New Orleans not determined until all the water is pumped out. As of November 15, 2005 the four state toll stood at 1311, far more than the 246 who died when hurricane Camille struck the same area in 1969 (although 113 of those died from floods in Virginia as the hurricane tracked north). New Orleans and surrounding areas of Louisiana have counted more than 1071 fatalities (likely to rise a bit as homes are cleaned out and debris removed); Mississippi suffered 226 dead, Florida 12, and Alabama 2. This is thus the third most deadly hurricane in U.S. history (first: Galveston, TX 1900, more than 6000 dead; second San Felipe-Okeechobee FL 1928, 1826 dead in U.S. and 312 in Puerto Rico).
As if Katrina weren't enough, another Category 5 hurricane developed in mid-September. Hurricane Rita began in the western Atlantic, moved past the Bahamas, passed over the Florida Keys, and entered the warm waters of the Gulf of Mexico where it strengthened from Category 1 to 5. It is now rated as the third most powerful Atlantic hurriccane on record. Even in September, the waters of the Atlantic were unusually warm. As Rita moved into the central Gulf of Mexico, its huge size (more that 400 miles in diameter), its winds reaching 175 mph, and its low pressure (884 millibars) indicated it could be a rival of Katrina or even worse. 
The entire central Gulf seemed threatened. Mandatory evacuations from north of Corpus Christi, Galveston and Houston, Beaumont, and western Louisiana were ordered. Three million people went northward. Officials were determined not to have a repeat of the Katrina fiasco. Massive traffic jams occurred in east Texas. Concern for much more damage to the Gulf oil refineries sent prices rising once more.
But as Rita swung northward, one natural condition favored less of a potential calamity. The hurricane moved over pockets of cooler water, as shown in this Aqua AMSRE image.
This loss of thermal energy weakened Rita so, while still large and ferocious, when it came on shore in the early morning of September 25 about at the Texas-Louisiana border its winds had dropped below 135 mph.
Still, this was a destructive hurricane that caused widespread damage. The next two images show a coastline just inside of Louisiana and the flooding of Cameron, LA. Extensive damage occurred in Beaumont and Port Arthur, TX, in Jefferson Parish, LA, and other small cities and towns. Parts of New Orleans were reflooded when wind-driven storm surges and rainfall caused several levees to be topped. But, while damage overall may exceed $8 billion, loss of life was minimal (3 direct; 24 turning an evacuation bus fire) and the gasoline refineries were largely spared.
On October 15 a third major hurricane started to organize. Of the three discussed here, this one in some ways was the most bizarre. It started in the Carribean as a tropical depression that in just a few days grew into a Category 5 hurricane. In fact, for a brief time, Wilma became the most powerful hurricane since modern instrumentation came into use to determine strength as its barometric pressure dropped to 884 millibars (26.04 inches). For 2+ days, it struck the Mexican Yucatan and sat over Cozumel and Cancun with almost no forward motion. Then as predicted, upper atmospheric steering currents caused an abrupt 90° eastward turn that headed it towards southern Florida. It completely crossed that state, wreaking havoc as a Category 3, then moved rapidly up the western Atlantic paralleling the American coast.
The track of Wilma appears below.
This set of 6 image panels shows three visible images of Wilma on different dates and for each a colored coded image indicating cloud heights.
The insured damage from Wilma exceeded $10 billion dollars. Considerable damage was first produced in Jamaica, then much flooding and wind damage in the Yucatan, followed by severe flooding in Cuba. Wilma entered Florida on October 24 as a Category 3 and remained at that level when exiting the east coast around Fort Lauderdale. Structural damage was not that great - although quite noticeable - but thousands of trees were uprooted throughout southern Florida and for the first two days up to 6 million people were without power. Here are two views of damage; location is given in the captions.
Since Wilma tropical storms Alpha (the National Weather Service went through all its named storms for the year and elected to use the Greek alphabet for subsequent storms) has come and gone with only rainfall effects. Then on October 27 tropical depression Beta become a Category 1 hurricane that struck Central America. In mid-November, the third such storm, Gamma, grew in the western hemisphere and moved onto Honduras with heavy rains. To everyone's surprise, on December 30th Tropical Storm Zeta formed in the eastern Atlantic.
As the stories of Katrina, Rita and Wilma unfold, some very difficult questions need to be answered. Most stem from the Katrina fiasco. Along the Gulf Coast, one insurance institute estimate places the number of homes that may not be salvagable and must be torn down as approaching 150000 (mostly middle class/poor in New Orleans) - a staggering number which may diminish if/when experts come up with innovative solutions to restore water-soaked lower levels and disinfect disease-carrying mud and waste. Some have even raised the trenchant question of whether the present location of New Orleans should be abandoned. The city has continued to sink (ground water withdrawal plus compaction without replensishment of soil from river flooding - New Orleans does have periodic small floods from rainstorms) even as sealevels are rising nearby.
What is needed to improve New Orlean's chances from inevitable future hurricanes are two obvious lines of defense: 1) higher and more secure levees, with possibly more canals (the present ones go back to the 1840s), and other engineering adjustments such as pumping stations that have their own protected power sources; and 2) a potent program of land reclamation that produces more barrier islands, delta extension, water-attracting swamps, marshes, and bayous; this would also entail redirecting the Mississippi River without compromising its key role in shipping. Another important modification: make the several gasoline and other petroleum product refineries much more immune to storm damage, and further protect the pipeline systems that transport these energy sources to the midwest and east. For decades now, scientists and engineers have been warning about the potential for catastrophe along the Gulf Coast. Plans to give back to the Mississippi its natural ability to deposit sediment along the delta to build its shoreline into the Gulf and extend the areas of wetland, which together would provide more protection for New Orleans to the north, have been proposed but not acted upon. The history of the delta is well known. Its principal distributaries have shifted significantly over the last 10 million years, as seen in this map:
Enough information from ground and aerial surveys, and satellite observations, have allowed maps of the present delta distributary complex to be produced. Look closely - there are discernible changes (see caption for dates):
Satellite imagery has been used to determine where and how much land was removed by storm surge/tidal erosion caused directly by Katrina. This map shows this land in black:
The Bird's Foot distributaries are constantly being modified. Some of this is natural; some is caused by the confinement of the Mississippi upstream by levees which affect the river's ability to spread its sediment load in its normal way; some results from hurricane action. This image of the delta, constructed from multiyear satellite observations, shows land eroded in red and deposited in green:
All told, more than 600,000 acres of wetlands have been lost in recent decades. Erosion rates as high as 40 acres in a day have been recorded. This map shows the extent of this loss and possible ways of eventually adding rather than eroding land:
Engineering the Mississippi flow patterns to optimize wetlands and shoreline protection is one of the main solutions. Building better dikes, levees, canals, and pumping stations are also important in protecting lowlands. It has long been known that New Orleans is highly susceptible to flooding. Proposals to provide major new components of a protection system (for a Category 3 hurricane; a Category 5 was considered too unlikely and thus too expensive) have been made for decades to state officials and more importantly to Congress and Federal agencies. Although some monies and authorization were provided, these fell far short, so that only token work to improve some of the facilities has been done.
In hindsight, the crux of the problem was failure to recognize the "Achilles heel" of the New Orleans dike system. The dikes were anchored by steel pilings driven to a depth of 33 m (20 ft). At that depth the local soil was a form of organic debris plus mud (Peat) which was very weak and porous. Water driven by the storm surges that seeped to this depth eroded through the peat, sapping (undercutting) the levees above so that the concrete floodwall within the levees were made unstable and then collapsed. Particularly vulnerable was the Industrial Canal, affected by the Lake Borgne storm surge. Warnings given about the peat layers as potentially unstable had been given but went unheeded. The blame for the Katrina disaster therefore can be spread to many; most of the failure is tied to political decision-making (rejection or minimalization of critical funding) that turned a blind-eye to the dangers forecast by the engineering/science communities. These shortcomings extend over several administrations. But, the latest example is typical: in 2005 Senator Mary Landrieu of Louisiana has pushed for $98 million dollars for short term action to improve levees by the U.S. Army Corps of Engineers, the Bush Administration countered with $22 million, and Congress settled on $42 million. Little of this has been actually allocated. Compare these numbers with sound estimates that the total dollars needed to really protect New Orleans and other areas in that part of the Gulf would probably be about $9 billion. Now, reflect on the huge price tag of as much as $150 billion to recover from Katrina and Rita and recall the phrase "Pennywise and Poundfoolish". Perhaps the best example of "I told you so" is to be found in the October 2001 Scientific American article by Mark Fischetti entitled "Drowning New Orleans" in which his scenario proved to be remarkably prescient when compared with the actuality of Katrina. In preparation for the future, the Corps of Engineers has strengthened and raised the key dikes throughout New Orleans. Other "preventitives" are being emplaced or considered. But so far nothing significant has been done to prepare the city for a Category 5 hurricane. A much improved evacuation plan is being implemented. Unfortunately, two critical conditions are getting worse. Sealevel continues to rise (some protection can be provided by restoring wetlands). But, studies in 2005-06 have revealed that parts of New Orleans and surroundings are sinking at rates from 6 to 29 millimeters per year. Exact causes are yet to be discovered. Here is a map of relative sinking published in 2006.
On a more general note, a rise in sealevel of 3 meters (10 ft) during the 21st Century (global warming due to a combination of natural interglacial temperature increase and gas emission hothouse effects) would notably modify the Gulf Coast, drowning many cities (if these cannot be protected) as shown in this map:
Looking back at the Katrina disaster, let's be grateful that worst case scenarios were somewhat WRONG. Lets hope that applies to the future. Let's put faith in Americans' ingenuity to restore much of the water-logged properties in New Orleans. Above all, that city must be renovated beyond its previous qualities. What other city east of the Mississippi (besides Charleston, SC) retains such a modern remnant of a glorious past - symbolized by the ever popular French Quarter, which deserves future visitors. Bring back Jazz to its native home!
Primary Author: Nicholas M. Short, Sr.