Page 269 - Geosystems An Introduction to Physical Geography 4th Canadian Edition

Chapter 8 Weather 233
(a) Part of New Orleans on April 24, 2005, before Hurricane Katrina.
(b) Flooded portions of the city on August 30, after Hurricane Katrina.
▼Figure 8.20 New Orleans before and after the Katrina disaster. [(a) and (b) USGS Landsat Image Gallery. (d) Kyle Niemi/ AP Images.]
(d) New Orleans on August 29, looking toward Lake Pontchartrain with Interstate 10 at West End Boulevard in the foreground. The 17th Street Canal is just to the left, off the photo.
Lake Pontchartrain
Lake Pontchartrain
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New Orleans International Airport
Orleans Avenue Canal
University of New Orleans
London Avenue Canal
French
4 KILOMETRES
17th Street Canal
Inner Harbor Navigation Canal
Industrial Canal
Ninth Ward
National Guard barracks
Louisiana
Superdome Quarter Tulane
Lake Pontchartrain
University Convention Center
Levee/floodwall
Area below sea level
Levees breached during Katrina
(c) Location of levee breaks.
with the Northern Hemisphere circulation patterns of Hurricane Gilbert in Figure 8.18a.)
Although tropical cyclones are rare in Europe, in Oc- tober 2005, the remnants of Tropical Storm Vince became the first Atlantic tropical cyclone on record to strike Spain. Likewise, Super Cyclone Gonu in 2007 became the stron- gest tropical cyclone on record occurring in the Arabian Sea, eventually hitting Oman and the Arabian Peninsula. In January 2011, an unusually strong category 5 tropical cy- clone hit northeastern Australia in the same area that un- derwent severe flooding a few months before.
Coastal Flooding from Hurricane Katrina The flooding in New Orleans after Hurricane Katrina in 2005 resulted more from human engineering and construction errors than from the storm itself, which was actually down- graded to a category 3 hurricane when it made landfall. About half of the city of New Orleans is below sea level
in elevation, the result of years of draining wetlands, compacting soils, and overall land subsidence. In addi- tion, a system of canals, built throughout the 20th cen- tury for drainage and navigation, runs through the city. To address the ever-present flood danger from coastal storms, the U.S. Army Corps of Engineers reinforced the canals with concrete floodwalls and levees, earthen embankments constructed along banks of waterways to prevent overflow of the channel.
Hurricane Katrina’s landfall, just south of the city, was accompanied by high rainfall and storm surges that moved into the city through canals. As the level in Lake Pontchartrain rose from rainfall and storm surge, four levee breaks and at least four dozen levee breaches (in which water flows over the embankment) permitted the inundation of this major city (Figure 8.20). Some neigh- bourhoods were submerged up to 6.1 m; the polluted water remained for weeks.
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