Geography Reference
In-Depth Information
flood wall and levee protection system, constitutes a shallow bowl, surrounded by
huge masses of water in which the metropolitan area is situated (see Figure 9.1).
This configuration explains the particular vulnerability of New Orleans.
The entire eastern seaboard of the United States is exposed to hurricane hazards
(see Chapter 1), especially in subtropical areas. There is an estimated 5.3%
probability that in any given year, a major hurricane, with winds of at least 180 km/h
(a Category 3 storm on the Saphir-Simpson scale) will strike New Orleans. In less
than a century, five major hurricanes have directly hit New Orleans - in 1915, 1947,
1965 (Betsy), 1969 (Camille) and 2005 (Katrina). Each of these caused extensive
flooding of the delta, but only since the city began expanding into marsh area did
vulnerability become a serious issue.
Containment of the Mississippi River has spared New Orleans the worst of
periodically devastating floods. But containment has also altered the sedimentation
cycle that sustains delta marshes. Approximately 4,900 square kilometers of
wetlands have been reclaimed by the Gulf of Mexico since 1930. Scientists first
sounded the alarm in 1975, and the first wetlands restoration initiatives were
proposed in 1990 (Coastal Wetlands Planning, Protection and Restoration Act, or
Breaux Act, named for Louisiana Senator, John Breaux, the Bill's principal
sponsor). The restoration of 26,700 ha of marshlands had been approved prior to
Katrina, but this only represents 5% of recorded losses, and very little has been
achieved so far due to lack of funding. The federal program, (Coast 2050 Plan)
approved in 1998, anticipated spending $14 billion on coastal engineering. The
program was reviewed, and funding reduced to $1.9 billion over 10 years, by the
Republican majority in Congress after 9/11. Although it is difficult to prove, this
type of short-term cost-cutting may have been responsible for some of the $128
billion
2
of damage caused by Katrina. Indeed, it is estimated that it requires
approximately 6 km of coastal wetlands to absorb a storm surge of 1 meter.
A United States Geological Survey (USGS) report stresses that wetland loss in
the Mississippi Gulf Delta iss mainly the result of subsidence. While the natural rate
of subsidence of the delta is estimated at 1 to 5 mm/year, average observed rates of
subsidence were in the order of 8-12 mm/year between 1965 and 1993. The report
attributes 80% of this subsidence to the oil and gas industries that extracted millions
of cubic meters of crude oil, natural gas, and water from the subsoil. The first
Mississippi Gulf Delta oil well came into production in 1901, and the first pipeline
became operational in 1908. The USGS report further shows that extraction
2
. Public expenditures effectively linked to Katrina in the following two years. More than
three-quarters of this expense went to flood relief, and the rest went to public administration
and infrastructures. It remains a provisional figure.
