REMOTE-SENSING ACTIVITY
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Old Wanderings

Purpose

To find evidence that a river channel has changed position over time.

Materials

a satellite image of the Missouri River

a sheet of poster board or construction paper

markers

glue

Background

During a flood, a river not only overflows, it also becomes more powerful--it carves away its banks at a faster rate, it gouges a deeper channel, and it carries more sediment. But a river that is carrying more eventually drops the extra sediment.

The Great Flood of 1993

October 4, 1993, Landsat Image prepared by Janet Chien

If the sediment drops in the old channel, then a new channel must be created. And sometimes a section of the river is stranded and an oxbow lake is formed.

That's the way it's "supposed" to work... river channels are supposed to change over time. Rivers are supposed to wander across their floodplains.

When people just used floodplains for farming it was okay for the river to flood and the channel to wander. But what if a factory or shopping center is built on a floodplain? What if an entire town is built on a floodplain?

Is it still okay for the river channel to wander?

Of course not!

Engineers have developed ways to keep a river channel from moving. They build levees before a flood, and they dredge the channel and bulldoze the sediments after a flood. Engineers can do many different things to keep a river in its place.

But if people no longer see the channel of the river near them wandering across the floodplain, how can we show them that their river wandered too?

You and your partner have decided that the Visitor's Center in River National Park should have a display that features a satellite image of the Missouri River clearly showing evidence of its changeable channel. You plan to label the image to point out evidence for positions that the river channel occupied in the past.

The section of river that you will use is available by clicking on the image above. It will take you to a closeup of the area in the yellow box. Then click again on the enlarged image to view a full-resolution Landsat image.

Procedure

Examine the image. Look for signs that the Missouri River's channel has not always been where it is today. Print out a color copy of the satellite image, draw straight lines pointing to each of the different features you find. Write a paragraph to explain how each feature shows the dynamic nature of this river. Diagrams may be helpful too.

Conclusion

Prepare the image and paragraphs that you want to be displayed in the Visitor's Center. Decide how you can best show your findings. Be creative! A game, poster, model, or other display can work. Just be sure that it points out the features that demonstrate channel movement and includes evidence that changes have occurred.

Try to give your display a catchy title too.