Hurricanes Katrina, Rita, and Wilma - Remote Sensing Application -
Hurricanes Katrina, Rita, and Wilma Part-2

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 Florida and some to 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.

The I-10 Twin Spans as the paired bridges reach New Orleans
Aerial view of a small part of the Twin Spans.

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:

Downdropped Highway 90 bridge; photo courtesy Paul J. Richards, AFP/Getty.

Landsat-7 checks in with its own partial scene view of flood and preflood imagery of New Orleans.

Landsat-7 views of New Orleans; flood view on top, preflood at bottom.

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.

SPOT-2 image of part of New Orleans; areas displaying in black are floodwaters.

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.

Quickbird image of much of New Orleans, taken preflood on March, 9 2004; note the large city part against the lake.
Quickbird image of the flooding in New Orleans as of August 31, 2005

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 view of central New Orleans.

Orbimage-3 obtained a view of Tulane University before the flood, and again after the campus was almost totally inundated.

Preflood image of Tulane University; note Gormley Stadium; Orbimage-3 image.
The Orbimage-3 image of the flooded Tulane University campus.

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. As one would expect, the delta country in Louisiana sustained huge damage. Here is an aerial view of destruction in Plaquemines Parish south of New Orleans:

Damaged homes in the delta country.

Eastward, Mississippi state experienced severe damage that extended tens of miles inland. Here is a Quickbird image of part of Biloxi.

Quickbird view of the water front; bottom view is pre-Katrina; top view shows the hurricane damage including the shifting of a floating casino on to the shore.

Among the casualties of Katrina are many of the antebellum (pre-Civil War [1861]) homes in Biloxi and other Gulf cities.

Damages sustained by antebellum homes in Biloxi.

Among Gulf cities receiving extensive damage was Gulfport, in Mississippi:

Katrina damage in Gulfport, MS.

The rest are ground and aerial views along the Louisiana and Mississippi coastal areas; read the captions for details.

Aerial view of part of Biloxi, after the waters have receded.
Street damage in Biloxi.
A single home in Pascagoula, MS, showing how wind and water undercut the home, while most of its surrounding trees were much less damaged; courtesy Louis DeLuca, The Dallas Morning News.
Automobiles piled up by Katrina.
Power boats moored along the Gulf, moved by waves into this jumble.

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:

Before and after Katrina views of Chandaleur Island.

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:

A Mississippi delta land mass that was completely destroyed.

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 $70 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)are factored in; experts in disaster assessment conjecture a real total cost as nearing $200 billion - enough to fund NASA for more than 10 years - when lost job income, business failures, and industrial shutdowns are included; 2) up to a half million refugees were 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 took 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 around 1900, 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 1700 fatalities; Mississippi suffered 226 dead, Florida 12, and Alabama 2. This is thus the third most deadly hurricane in U.S. history (first: Galveston, TX in 1900, more than 6000 dead; second San Felipe-Okeechobee FL in 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 hurricane on record. Even in September, the waters of the Atlantic were unusually warm.

The warm waters of the tropical Atlantic, September 18, 2005.

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.

Hurricane Katrina.

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.

Small, but important variations in surface water temperature.

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.

Category 3 Hurricane Rita making landfall.

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.

Devastation along the Louisiana Gulf Coast.

One longer term destructive effect from Katrina and Rita might not come to mind until one is prompted to think about the topic of "fallen trees". An inventory of downed trees in the Gulf Coast caused by these two hurricanes disclosed that about 320 million trees were affected. The areas of major damage appear in this map:

Areas, in color, of major tree damage from Hurricanes Katrina and Rita.

This aerial photo illustrates the haphazard way many of these trees were downed:

Fallen trees (brown) in a Mississippi forest; these resulted from swirling winds during Hurricane Katrina.

Most of the trees affected were pines and some hardwoods. These trees have been decaying rapidly, putting CO2 into the atmosphere (equal to about all the carbon dioxide removed from air over the U.S. by normal growth processes). For the short term, trees that have taken root since the hurricanes are of species not favorable to the desired ecology. It will take time and effort to restore the balance by reintroduction of pines and other evergreens.

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.

The path of Wilma.

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.

A series of Terra MISR images of Katrina; the colored panels indicate 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.

Water surge on the west coast of Cuba.
Damage in a shopping center in Cancun, Mexico.

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:

Areas of the primary delta distributary system in the last few million years.

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):

The land mass components of the Mississippi River delta distributary system in 1973 (left), 1989 (center), 2003 (right)

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:

Land in the Mississippi Delta lost (shown in black) from tidal and storm surge erosion during Hurricane Katrina.

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:

The Bird's Foot delta of the Mississippi; areas eroded over the last 30 years are shown in red; areas built up appear 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:

Loss of land in the Mississippi River Delta
From David Merrill, USAToday

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.

The U.S. Army Corps of Engineers has now spent about $20 billion on shoring up the levee system in New Orleans. It is expected to be completed by 2011. This system should withstand a category 4 hurricane, but if the eye passes just to the east, flooding from Lake Ponchartrain remains a threat.

The New Orleans levee system as of 2011.

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.

Measured sinking rates in parts of New Orleans.

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:

The new coastline in the southern U.S. resulting from a 3 meter rise in sealevel; note positions of present day cities.

As this paragraph is written on August 28, 2010 - the 5th anniversary of Katrina - these general observations seem appropriate: New Orleans has "bounced back" (largely recovered). Tourism is at new levels of popularity. The economy is stable. As a blessing from the attention Katrina forced on the city, the problem it had before with subpar schools has been turned around through a highly successful charter school program that has raised student performance levels above the national average. The city's morale was given a big boost by the victory of the New Orleans Saints (football) in the Superbowl. On the negative side, the city population remains about 100,000 below pre-Katrina days. And the citizens of this Gulf Coast region continue to look with distaste and disfavor on the shortcomings of both federal and state government responses during the first days and weeks following the hurricane.

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!

The French Quarter

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Primary Author: Nicholas M. Short, Sr.