Objective: To familiarize students with the ecological changes that have
taken place along the Missouri, and more broadly, with the concept of erosion.
Time: 1-2 class periods
Skills: Scientific Observation and experimentation
Content: Environmental History and Science
(Note: If your students have limited backgrounds on river ecology and/or ecosystems, you
may want to refer to Exercise V in the Grades 4-5 section of the teacher's manual. The activities listed
there can be adapted for older students, and the American Rivers website is a great place to
start for an introduction to river science. See : http://www.amrivers.org/kids-rivers.html.)
Vocabulary:
alleviate - to make more bearable; to lessen
endangered - in a state of danger or peril
hydroelectric - relating to the production of electricity by water
ecological - having to do with the relationship between organisms and their environment
Mandan - a group of American Indians from the Missouri River Valley region
If Lewis and Clark were to travel along the Missouri River today, they would not recognize
much of what they saw. When they traveled up the Missouri, they encountered a river that
was changing constantly. The water flowed through several main channels but also coursed
through thousands of smaller side channels and chutes. Water depths varied all along the
river, as did the speed of the water. New side channels were being created all of the time
when the river flooded, and old ones closed as they filled with sediment and silt. One observer
remarked in the early 1900s that the river never seemed "content with the bed" it occupied.
Today, the picture of the Missouri is very different. The river is 127 miles shorter, only 1/3
as wide between Sioux City and St. Louis, and much deeper and faster than it was when the Corps
of Discovery made their historic journey.
Because the Missouri is so central to North America-it travels 2,315 miles and drains 1/6 of the
continental United States-people have been trying to tame the river, ever since the Lewis and
Clark expedition. Travel along the Missouri was so treacherous during the 19th Century that
some estimates indicate that 3 of every 7 boats were destroyed by "snags" (the common name for
obstacles such as fallen trees). As a result, farmers and merchants, among others, have sought
a river of uniform depth and constant water speed in hopes of speeding transportation along the
river. As early as the 1830s, engineers began systematically removing snags from the river.
In 1896, the Montana Power Company constructed the first in what was to become a series of dams
intended to harness the river's water power. In 1910, engineers created a 6-foot deep channel
between Kansas City and St. Louis, using rock and wood pilings to stabilize its banks.
In every case, flooding of the river proved too powerful for these man-made improvements.
After the disastrous flooding of the river in 1943, which forced residents of Omaha, Nebraska
to navigate their city by boat, the U.S. Army Corps of Engineers began making plans to build
a series of dams and levees to regulate the flow of the river. What they came up with was
the Pick-Sloan Plan, a plan for 5 of the world's largest earthen dams in Montana and the Dakotas,
to add to Fort Peck Dam, built in Montana in the 1930s, and a 732-mile navigation canal between
Sioux City and St. Louis. The construction turned once-open water into an additional 100,000
acres of land. Although the dams did succeed in producing hydroelectric power for surrounding
residents, the changes failed to alleviate the flooding, as had been intended. In addition,
the creation of dams, levees, and a main channel ended up causing serious ecological damage.
The river's sandbars have been worn away, the banks have been eroded, and the temperature in
some places has changed as much as ten degrees Celsius.
All these changes have greatly threatened species that had adapted to the natural conditions of
the river. More than 30 species native to the Missouri have been placed on state and federal
endangered species lists, according to a review by the U.S. Fish and Wildlife Service.
In addition, approximately 70 other species are rare, according to resource managers.
The alteration of the river has affected people, too. Native Americans have lost more
than 350,000 acres of farmland due to the damming and channelization of the river. After the
creation of the Garrison Dam in 1953, for example, a newly constructed reservoir swallowed up
nearly 85 percent of the Mandan Indians' lands and a number of their homes.
To give you some idea of the extent of the ecological transformation, when Meriwether Lewis first
stumbled upon the Great Falls of Montana, he described them as "one of the most beatifull objects
in nature...." Today, when one looks over the Great Falls, one stares straight into the Ryan Dam.
Flooding, moreover, has only gotten worse with all of the man-made "improvements" to the river.
Now, when the river floods, it crests even higher than it used to at many places. The levees
designed to shield farms from flooding often were built too close to the river, so they offer
little protection. What makes all of these natural costs so hard to bear is that the primary
goal of the Pick-Sloan plan-to increase barge traffic on the Missouri-has never happened.
Authorities originally hoped that the Missouri would carry up to 20 million tons of cargo a
year, but the most that the river ever held was 3.3 million tons in the late 1970s.
Discussion Questions
-
Based on the above reading, name some of the transforming events in the history of the Missouri
River. What do you think has been the greatest period of change? What were the benefits and
"costs" of each of these events?
-
Describe the basic features and intent of the Pick-Sloan plan. Another reason that President
Franklin Roosevelt was so interested in undertaking this dam-construction project is that he wanted
to put to work the large number of soldiers returning from WWII. Do you think that this was a
good idea? Based on your knowledge of American history, what other kinds of jobs did returning
soldiers find? Discuss the trade-offs involved in this kind of decision.
-
Why would farmers and merchants consider the "natural" state of the Missouri a problem?
Can you think of other cases, besides rivers, where humans have attempted to overcome
the obstacles of nature in order to facilitate their own activities? Were they any more or
less successful? Why?
-
Why do you think flooding has grown worse since the damming and channelization of the river?
(See the science experiments in the "extended activities" section below to test your hypotheses.)
Extended Activities
-
Using the events listed above as a starting point, try drafting a timeline of changes in the
Missouri River. Have students do additional research to fill in the gaps between the items listed
above. (A good starting point is the American Rivers Guide to the Missouri River of Lewis and Clark:
Passage of Discovery by Daniel B. Botkin. If you are interested in learning more about this book,
you will find ordering information in the Additional Resources section of the Teacher's Manual.) Do
the periods of greatest activity fit with the answers that students gave for question #1 above?
-
Erosion of the banks of the Missouri is critical to the survival of many different plants and animals.
By contributing sand, silt, and trees, erosion helps to create important river habitats. Trees that
once washed into the Missouri River, for example, accumulated in side channels, contributing to the
production of insects that were in turn consumed by fish and waterfowl. Ask students to speculate
about how channelization of the Missouri affected this erosion process, then have them perform the
following experiment to see Erosion in Action.
Materials: pen or pencil; drinking straw, cut in half; paper cup; scissors; modeling clay;
flat surface, like a cookie sheet or cardboard covered in foil; ruler; soil; plastic jug or other
container filled with water
Procedure:
-
Use a pen or pencil to poke a hole in the side of the paper cup close to the bottom edge.
-
Insert 1/2 of the straw into the hole in the cup and then seal the cracks around the hole with the
clay or some other insoluble substance.
-
Place the flat surface on the ground and raise one side a couple of inches by placing soil
underneath it.
-
Cover the surface of your cookie sheet or cardboard with a thin layer of soil and position
your cup in the middle of the raised end of the sheet.
-
Fill the cup with water, holding one finger over the opening of the straw to prevent water from
leaking.
-
After filling the cup, release your finger and observe how the water moves down the sheet
through the soil.
-
Dry off the sheet and repeat steps 4-6, raising the end of the sheet first 4 inches and then 6
inches.
What happened to the soil when you raised the sheet? Did more of less soil get washed away? Why?
Was the water moving more quickly or more slowly each time? What does this tell you about the factors
that affect the rate of erosion?
NOTE: As an extension, you may have students try placing several leaves, sticks, and small
rocks on top of the soil. Do students think that more or less soil will wash away? Keeping the
tray tilted at the same angle as in one of the above experiments, have students release the same
amount of water from the cup. Did more or less soil wash away? (If it is difficult for students
to measure the amount of soil, you may want to have them catch the water at the bottom of the sheet
in a plastic container and then try filtering the water through paper towels.) Do the results match
with your thoughts about how channelization would affect the river? Would the water move more
quickly or more slowly through a channel? Why?
