Shorelines and Shoreline Processes - The Changing Earth: Exploring Geology and Evolution - page 426

of 230,000 km 2 . Gulfport and Biloxi, Mississippi were mostly
leveled, but most of the public's attention has focused on the
damage in New Orleans, Louisiana (

Figure 16.19).
Even when New Orleans was founded in 1718, engineers
warned that building a community on a swampy, subsiding
parcel of land between Lake Pontchartrain to the north and
the Mississippi River to the south was risky; now most of the
city lies below sea level. In any case, New Orleans was nearly
surrounded by levees (earthen embankments) and flood-
walls (structures of concrete and steel) to protect it from the
lake and river.
When Hurricane Katrina came ashore, the levees ini-
tially held, but on the next day some of the floodwalls
were breached and about 80% of the city was flooded.
And because New Orleans is mostly below sea level, the
fl oodwaters could not drain out naturally. In fact, the city
has 22 pumping stations to remove water from normal
rainstorms, but as the city fl ooded, the pumps were over-
whelmed, and when the electricity failed, the pumps were
useless. All in all, Hurricane Katrina was the most expen-
sive natural disaster in U.S. history; the property damages
exceeded $100 billion and more than 1800 people died.
Then, in September, Hurricane Rita hit the Gulf Coast,
mostly in Texas, and caused about 120 more fatalities and
nearly $12 billion in damages.
Scientists, engineers, and some politicians had warned of
a Katrina-type disaster for New Orleans for many years. They
were aware that during a large hurricane the levees or fl ood-
walls would likely fail. In fact, the political leaders in Louisi-
ana had pleaded for years for funds to strengthen the levees,
but for one reason or another, the funds were never allocated.
“What do we do now?” is a question that will be debated for
many years. Another factor to consider is that coastal fl ood-
ing is exacerbated by rising sea level that
results from global warming. Most of
you reading this topic will not become
geologists, but perhaps you will be en-
gineers, city planners, members of plan-
ning commissions, politicians, or simply
concerned citizens of coastal communi-
ties and will have to deal with these or
similar problems.

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Marine terrace

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Figure 16.17 An Emergent Coast in California Emergent coasts
tend to be steep and straighter than submergent coasts. Notice
the several sea stacks and the sea arch. Also, a marine terrace is
visible in the distance.

Image not available due to copyright restrictions

HOW ARE COASTAL
AREAS MANAGED AS
SEA LEVEL RISES?
During the last century, sea level rose
about 12 cm worldwide, and all indi-
cations are that it will continue to rise.
The absolute rate of sea-level rise in a
shoreline region depends on two fac-
tors. The fi rst is the volume of water in
the ocean basins, which is increasing as
a result of glacial ice melting and the