GEOG 1350 Lecture Notes - Lecture 1: Windbreak, Lower Ninth Ward, Flood Wall
30 Nov 2017
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GEOG*1350 Earth: Hazards and Global Change
Video: Hurricane Katrina
1. What is a tropical depression? Describe the origins of Hurricane Katrina.
A centre of low atmospheric pressure. Water vapour rises then cools releasing heat energy which
fuels the storm, this sucks in more warm air which shoots upwards, hits the stratosphere and goes
back out, causing counter clockwise motion.
• Katrina formed from a tropical wave that had moved off the coast of Africa and then developed
into a tropical depression.
• Katrina begins as a small storm called a tropical depression, a centre of low atmospheric
pressure. In the warm waters of the eastern Atlantic, water vapour rises from the ocean then
cools which forms clouds and releases heat energy which fuels the storm.
• When the rush of air hits the stratosphere, it flattens out and the storm starts turning counter
clockwise.
• As soon as the winds reach 39 miles per hour, the depression is called a tropical storm
2. What were the government standards for the construction of the concrete levees?
• After Hurricane Betsy in 1965, the government set standards for the levees.
• The congress provided the Army Crops of Engineers with funds to upgrade the levees to
withstand a Category 3 hurricane and no more.
3. Why did the wetlands begin disappearing after the levees were built? How have disappearing
wetlands increased the vulnerability of New Orleans?
• Before the levees, when the Mississippi river flooded the wetlands were strengthened and
replenished.
• The wetlands protected New Orleans against hurricane storm surges, soaking up the violent
waters like a sponge, while stands of cypress trees acted as a windbreak.
• The wetlands began disappearing after the levees were built because the levees stopped the
rivers from flooding which starved the wetlands of new soil and started disappearing at an
alarming rate.
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