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NOVA ScienceNOW

Hurricane Katrina: Wetland Destruction

  • Teacher Resource
  • Posted 12.17.05
  • NOVA scienceNOW

Wetlands along the southern coastlines of the United States serve as natural speed bumps to approaching hurricanes by starving them of warm ocean water and creating physical barriers to surging flood waters. However, in the last 100 years, the construction of levees and canals has turned thousands of square miles of wetland habitat into open water. This video from NOVA scienceNOW explores the importance of these critical habitats and examines the damage Hurricane Katrina caused to one stretch of Louisiana wetland.

NOVA scienceNOW Hurricane Katrina: Wetland Destruction
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  • Media Type: Video
  • Size: 42.9 KB
  • Level: Grades 6-12

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Source: NOVA scienceNOW: "Hurricane Katrina"

Background

Humans have been altering the natural environment to suit their needs for thousands of years. We've constructed shelter where none existed, planted food crops where forests once flourished, and in one of the more striking examples, built an entire city in the middle of a swamp. New Orleans, Louisiana, is a testament to the human will and ingenuity required to overcome seemingly impossible odds — in a part of the world where a great deal of commerce stood to be gained. However, in August 2005, Hurricane Katrina tragically illustrated the potential consequences of defying the forces of nature.

New Orleans sits in the middle of an ancient floodplain of the Mississippi River. Periodically, this mighty river, like most wild rivers, overflowed its banks, inundating the surrounding area. What was a natural and necessary occurrence for the wetland ecosystem of the Gulf coast threatened the viability of communities along the banks of the Mississippi. In response to this threat, people, as part of a government plan, began building a system of levees to heighten the river's banks and protect themselves from flooding.

Ironically, the centuries-old effort to control seasonal river flooding in New Orleans and other coastal cities has made the same communities increasingly vulnerable to ocean flooding from tropical storms and hurricanes. Wetlands along the Gulf coast provide the first line of defense against deadly hurricanes, by both limiting the storms' access to the warm open ocean water that drives them and by creating a physical barrier to the floodwaters, or storm surges, that they generate. Yet, coastal wetlands have been deteriorating and shrinking for decades because they no longer receive the influx of sediment and nutrients that periodic river flooding once provided.

The bottom, or substrate, of coastal wetlands is unstable. It settles and sinks continuously. Without a steady supply of new sediment and nutrients, wetland plants soon become flooded themselves, causing expanses of open water to form. As a result of Mississippi River flood control, together with the opening of shipping channels that have caused saltwater to infiltrate freshwater wetlands, Louisiana has lost nearly 5180 square kilometers (2,000 square miles) of coastal wetlands, an area the size of the state of Delaware, in the last 70 years. As this trend continues, the likelihood that another hurricane will devastate the Gulf Coast region only increases.

To learn more about how human-engineered changes have altered the Mississippi River system, check out The Mississippi River Delta and Flood: Farming and Erosion.

To learn more about hurricanes and how they impact the Mississippi River Delta, check out Hurricanes: New Orleans Under Threat, Hurricane Katrina: A Scientist's Response, and Hurricane Katrina: Possible Causes.

Questions for Discussion

    • Explain how wetlands act as a buffer against the ocean's force when a hurricane approaches the coastline.
    • Why do some people think it is important to rebuild the marshes that were damaged during Hurricane Katrina?
    • Do you think there should be restrictions on building in wetlands? Explain your reasoning.

Resource Produced by:


					WGBH Educational Foundation

Collection Developed by:


						WGBH Educational Foundation

Collection Credits

Collection Funded by:


						National Science Foundation



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