The Probability of a Major Hurrican Hitting New Orleans

The Probability of a Major Hurricane Hitting New Orleans

Table of Contents

Executive Summary 3

Introduction 3

Hypothesis 7

Analysis & Method 8

Conclusion 10

References 12

Appendix 14

Executive Summary

New Orleans, Louisiana lies at the second lowest elevation among major cities in the United States. It is a city surrounded by water, making it almost like an island. To counter this dangerous combination of the low elevation along with the lakes, rivers and swamps surrounding it, the Army Corps of Engineers built a series of levees around the city to foster its protection. It is these very same levees however that might doom the city should a Category 3 hurricane ever hit. Our statistical analyses examined the current belief that there is a 39% probability that New Orleans will be hit by a major hurricane and based on the resulting Z-score, rejected that belief. We did find however that the probability, while not 39%, was still in the 30th percentile range, which should still be a major cause for concern among the leaders and residences of the city of New Orleans.

Introduction

New Orleans is a city that is rich in culture as well as history. The city is in effect, an island - Lake Pontchartrain surrounds the city to the north, the Mississippi River to the west and south, and a bevy of lakes - including Lake Borne to the east. Surrounding the city is a series of levees to keep these bodies of water at bay. In addition to these levees, the only defense the city has is a series of canals and a very antiquated pumping system. However, the same levees that protect the city, makes it a death trap should a major hurricane make a direct hit to the metropolitan area. The risk of intense flooding brought forth by storm surges of 20+ feet would wipe the city out.

Picture: http://www.publichealth.hurricane.lsu.edu/Would%20New%20Orleans%20Really%20Flood.htm

New Orleans was founded to be a port to the world - with its intersection at the Mississippi River and the Gulf of Mexico, it was a great location for world trade. However, it was also a cesspool of disease, floods, and other problems. Despite this, the city was a major economic powerhouse and the city grew and prospered despite of the problems.

As the city expanded, swampland was reclaimed to expand the city. To protect its citizens, the Army Corp of Engineers built a series of levees around the city. These levees form a bowl around the city. It is precisely this architecture that was meant to protect the city will in effect destroy the city.

What is a major hurricane? Hurricanes are measured using the Saffir-Simpson scale. The scale ranges from a Category 1 hurricane, which is the weakest, to a Category 5 hurricane, which is the strongest and most dangerous hurricane.

The following chart illustrates the differences between the categories, which are measure by the winds of the hurricane.

Saffir-Simpson Scale

Saffir-Simpson

Category Maximum sustained wind speed Minimum surface pressure Storm surge

mi/h m/s kt mb ft m

1 74-95 33-42 64-82 greater than 980 3-5 1.0-1.7

2 96-110 43-49 83-95 979-965 6-8 1.8-2.6

3 111-130 50-58 96-113 964-945 9-12 2.7-3.8

4 131-155 59-69 114-135 944-920 13-18 3.9-5.6

5 156+ 70+ 136+ less than 920 19+ 5.7+

Major hurricanes are those classified as a Category 3 (sustained winds of 111+ miles per hour or higher.)

Looking at the chart, the problem for New Orleans is evident - storm surge and the wetlands and barrier islands that are loss at an astounding rate every year. These wetlands and barrier islands work to slow down the storm surge and slow down the storm itself. Without these barriers, water will push inland to New Orleans and spill over the levees. According to Walter Maestri in the Jefferson Parish (a suburb of New Orleans) emergency office, gives this scenario:

"The hurricane is spinning counter-clockwise, it's now got a wall of water in front of it some 30 to 40 feet high, as it approaches the levees that surround the city, it tops those levees," describes Maestri. "The water comes over the top - and first the communities on the west side of the Mississippi river go under. Now Lake Ponchartrain-- which is on the eastern side of the community--now that water from Lake Ponchartrain is now pushed on the population that is fleeing from the western side, and everybody's caught in the middle. The bowl now completely fills and we've got the entire community under water, some 20 to 30 feet under water."

Remember all those levees that the U.S. Army built around New Orleans, to hold smaller floods out of the bowl? Maestri says now those levees would doom the city, because they'll trap the water in. "It's going to look like a massive shipwreck," says Maestri. "Everything that the water has carried in is going to be there. It's going to have to be cleaned out-- alligators, moccasins and god knows what that lives in the surrounding swamps, has now been flushed -literally--into the metropolitan area. And they can't get out, because they're inside the bowl now. No water to drink, no water to use for sanitation purposes. All of the sanitation plants are under water and of course, the material is floating free in the community. The petrochemicals that are produced up and down the Mississippi river--much of that has floated into this bowl... The biggest toxic waste dump in the world now is the city of New Orleans because of what has happened."

To any other city in the United States, this scenario would cause damages like the 2004 hurricanes did to Florida. However, most cities are above sea level. New Orleans