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Flood: Farming and Erosion

  • Teacher Resource
  • Posted 12.17.05
  • NOVA

Farmers and rivers have a close, though not always friendly, relationship with one another. Rivers can create prized farmland, but they also flood fields and the communities built alongside them. What's more, farming practices may contribute to an increase in the magnitude and intensity of river flooding. This video segment adapted from NOVA explains the flooding problem and suggests possible solutions.

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NOVA Flood: Farming and Erosion
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  • Media Type: Video
  • Running Time: 4m 38s
  • Size: 13.9 MB
  • Level: Grades 3-12

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Source: NOVA: "Flood!"

This resource was adapted from NOVA: "Flood!"

Background

The Mississippi River watershed drains more than one-third of the United States; rain falling in eastern Montana may eventually end up in the Gulf of Mexico. Such an expansive watershed accommodates a huge volume of water. On average, the Mississippi carries 173,600 cubic meters (227,000 cubic yards) of water per second. On occasion, however, this great river overflows its banks and inundates a wide swath of land on either side known as the floodplain.

Flooding is a natural part of the life of a river. Before humans intervened, the Mississippi River flooded every year. In fact, floods and the sediments they deliver are largely responsible for the richness of the soil found in floodplains. Unfortunately, these soils and other resources provided by the river have also encouraged people to build communities in the paths of floodwaters.

For decades, the most common solution to the problem of rivers overflowing their banks -- and damaging property and endangering lives -- has been to artificially increase the height of riverbanks. The Army Corps of Engineers, which has been in charge of flood control in the United States since 1928, boasts a 13,700-kilometer (8,500-mile) system of heightened riverbanks, or levees, along the country's most flood-prone rivers. In addition, the federal government has built flood-control dams on most major streams and rivers in the Mississippi River watershed.

This engineering solution arose following a major flood of the lower Mississippi River in 1927. The event flooded 14,000 square miles (37,000 square kilometers) and forced 700,000 people from their homes. Unfortunately, floods have continued to breach levees since 1928, and many people think that simply building higher, stronger walls is no solution to a recurring problem.

Many experts suggest that natural solutions can help to minimize the devastation from floods. They advocate restricting the development of communities in floodplains to keep people and property out of harm's way. They recommend farming practices that help reduce the erosion of topsoil, and in turn the amount of runoff. These include constructing terraces where necessary to reduce the slope of fields, planting non-cash crops between crop rows to better retain moisture and protect topsoil, and plowing circular bands along the contours of fields to slow the flow of water off of them. Lastly, they advocate the conservation of remaining wetlands and the restoration of those that have been damaged or drained. These areas naturally absorb huge volumes of runoff caused by large storms and keep them from entering the river channel where they can cause harm downstream.

To learn how farming practices and an anomalous weather pattern caused one of the costliest disasters in U.S. history, check out The Great Flood of 1993.

To learn about farming practices that can reduce flood risk, check out Organic Farming: Conserving Top Soil.

To learn about other land management practices that can increase the risk of flooding, check out Hurricanes: New Orleans Under Threat and Hurricane Katrina: Wetland Destruction.

Questions for Discussion

    • Discuss the factors that influence the permeability of soil.
    • How does farming affect the soil and make it more prone to flooding?
    • What can humans do to manage flooding in an agricultural setting?
    • Compare wetlands and farms in terms of how they respond to an increase in water in the soil.

Resource Produced by:


					WGBH Educational Foundation

Collection Developed by:


						WGBH Educational Foundation

Collection Credits

Collection Funded by:


						National Science Foundation



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