River Flooding

River Flooding


Floods can be big problems for people who live near great rivers, but for the rivers themselves flooding is a natural event. In this activity, you will learn about how and why river floods occur.        


Go to The Ups and Downs of River Flooding and read the "What Is a Flood?" section. Once you have finished that section, view the San Diego River annual hydrograph for an example of a river with very flashy flooding behavior.

As you are looking at these resources, think about answers to these questions. You can record your answers on the River Flooding student sheet.

  • Why is the hydrograph (flood pattern) of a river much like a signature?
  • Are small rivers flashier than large ones? Why or why not?
  • Are seasonal floods regular events and do they occur on a schedule?
  • What might happen if the Amazon failed to flood for one year? What about for 10 years?

Go to The Ups and Downs of River Flooding and read the "What Is a Flash Flood?" section. Your teacher will divide the class into small research teams. Your team should search the Web for information on well-known flash floods. You may use the examples below, or others that you have heard of or can find in a Web search. Your research team should find the answers to the questions on the Flash Floods student sheet.

Your team should prepare a brief report on "your" flash flood. It might be illustrated with maps, photos or drawings, and bulleted points.

Example Flash Floods:

  • Cheyenne, Wyoming; August 1, 1985
  • Shadyside, Ohio; June 14, 1990
  • New Braunfels, Texas; August 2002
  • Madison County, Virginia; June 25-27, 1995
  • Fort Collins, Colorado; July 28, 1997
  • Rapid City, South Dakota; June 9, 1972
  • Johnstown, Pennsylvania; May 31, 1889
  • Big Thompson Canyon, Colorado; July 31, 1976

Optional: Get some safety information from the NOAA National Weather Service Flash Flood site and the Red Cross Flash Flood Safety. The latter site includes advice on what to do if you are camping, in a car, outside, or trapped by a flash flood.

Go to The Ups and Downs of River Flooding and read the "What Is a Great Flood?" section. Once you have finished that section, take a visual tour of the Grand Forks Flood of 1997 and visit the PBS Journey to Planet Earth site and read about the great flood of 1993 and how it affected Grafton, Illinois.

As you are reading and looking at these websites, think about answers to these questions:

  • How is a great flood different from a seasonal flood?
  • Are great floods predictable?

Now, go to the "How Are Floods Good?" section, read it, and then take a short visit to the Nile River at the World Resources Institute Watersheds of the World: Africa-Nile Watershed. Study the map and the map description statistics below it and be prepared to answer these questions:

  • Where are most of the cities?
  • How many major cities are in the watershed?
  • What proportion of the watershed is forest, grassland, cropland, or barren?
  • Is this an arid watershed?
  • How might these factors influence flooding in the watershed?

Floods are not always good. Sometimes they are very very bad for humans. Go to the "How Are Floods Bad?" section and read it. Now visit the Fatal Flood website and work your way through some of the available resources describing how the Mississippi Flood of 1927 affected people. The transcript of the film "Fatal Flood" as well as some of the primary sources used in making the film are particularly interesting.

Be prepared to answer these questions.

  • Can a great river like the Mississippi be controlled by humans?
  • Can humans work hand-in-hand with natural flood-dissipation processes to protect their towns and property?
  • What are some of the causes of catastrophic floods?
  • What are some of the effects of catastrophic floods on humans?

This esheet is a part of the Great Rivers 2: The Ups and Downs of River Flooding lesson.

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Esheet Details

Grades State Standards