Streams, rivers, and watersheds:
Modeling the effects of slope and volume on erosion and channeling
Earth science
(middle grades)

Introduction

This unit explores streams, rivers, watersheds, and stream tables to model their evolution. It includes intended learnings, activity sequence, lesson plans, scoring guides, supporting materials, resources, materials and lab notes. Ready to go.

Overview

Water leaves footprints.

Streams, rivers, watersheds, and stream tables to model their evolution. Watersheds are where water collects and where water flows to the oceans. However, streams and rivers are not just water. They include particles: sand, clay, soil, and more; which are suspended in the water and move with the current or sink to the bottom. Either way they pile up as sediment or erode the river bed as they move, changing the flow and shape of the rivers, streams, and watersheds over time. This can create serious consequences for safety, erosion, production of energy and recreational opportunities; all of which affect the quality of life and health of organism who depend on stream, river, and watershed environments. Knowledge of how water flows and it interactions in streams, rivers, and watershed is also important for our understanding of ecosystems to preserve, restore, and prevent their degradation.

This investigation explores how different volumes of water flow and how it effects erosion and channeling of streams and rivers.

Students will collect and organize observational information as it relates to flow and these variables to create explanations and develop models for stream and rivers.

The term meander originated from the ancient Greek Meander River (Greek, Μαίανδρος Maiandros; Latin, Maeander). It had a very twisted convoluted path across a flood plain before it flowed into the Aegean Sea.

At the mouth of the Meander River the ancient Greeks built a seaport town that was considered the greatest Greek city in the east. Today, the town is called Milet is in Turkey and the Turkisn name of the river is Büyük Menderes River.

Not only did the river meander but it carried large amounts of silt, Which caused the river valley to silt up pushing the shore line farther into the Aegean Sea. The map shows how the shore line moved over time so the town became landlocked and today is miles from the shore. Source

Map source: Eric Gaba, Wikimedia Commons user [GFDL or CC BY-SA 3.0], via Wikimedia Commons

Meander has become a common noun used to describe anything convoluted and winding. For example, speech and ideas. His explanation meander before arriving at a conclusion.

Big ideas, concepts, facts, and outcomes

Pedagogical ideas

Materials

• Stream-table setup: plastic siphon tubes of different diameters (4mm, 5mm, 6mm), reservoir container, catch container, plastic drain tube,
• 300 ml coarse sand
• 300 ml of fine sand
• Sheet of stiff plastic
• Ruler
• Pencil, colored pencils, brown, blue, black, green,
• Paper
• 600 ml mixed sand (coarse and fine-sand)
• Large stone
• 600 ml of soil
• Grass seeds

Focus questions:

• What is water?
• How does water interact with the Earth?
• How does water shape the Earth and geography of the Earth?
• What are the forces that cause the shaping?
• How can you collect data to model the flow of water from falling as precipitation and its travel to the ocean.

Scoring guide

Low level: Describes rain as related to streams and rivers and streams and rivers as concluding where seas and oceans begin.

Middle level: Describes rain and run-off as causing erosion and water from it as collecting in streams and rivers and emptying into seas and oceans.

Upper level: Describes rain and run-off as a powerful force proportional to the slope or volume of the flow. That water flow erodes the Earth in specific ways to create channels. And even thought large volumes of water or steep slopes can increase erosion long periods of time can erode the most erosion tolerant earth materials.

Top level: Describes rain and run-off is a powerful force that erodes the Earth and how different flows of water interact with the Earth to create stream beds. How different interactions depending on flow volume (related to precipitation and run-off), speed of the flow (related to the slope, run-off and shape of the channel), and earth materials (related to the flow of the water, mass, hardness, shape, and location of materials) create different channels and deposits.

Additional resources

• Watershed exploration with the WikiWatershed Toolkit & to model your watersheds. A tool kit to map your geographical region and provide watershed information.
• Excellent research article on avulsions: how they form, evolve, and stream table models used to model their behaviors. When the Levees Break by Fred Pearce in Science May 14, 2021.
• Excellent research article on historical avulsions around the world. Where Rivers Jump Course by Sam Brooke et. al. in Science May 27, 2022.

Activities

Lesson plans

Lesson plans for each of the activities are not included. Recommendation for them would be to follow a learning cycle (exploration, invention, discovery) for each activity. The lab notes can be used to generate a plan for each activity chosen for students to participate in.

Example:

Exploration: The investigation questions in the lab notes can be asked and disussed. Discuss what the students know about the question and how information can be collected with an investigation to provide information for students to validate their ideas and create explanations and models. The materials, set up, and procedures in the lab notes can be used to provide guidance and suggestions for the invention. When students have different ideas, then the students ideas should be replace for their procedures.

Invention: The investigations are implemented, students collect information from their investigation, share the results with the class, discuss differences, and explain how their observations can be used to answer their investigation questions and make decisions on how to further investigate.

Discovery: Review, summarize, and dicsuss what was found and how it can or can't be generalized to streams, rivers, and watershed on Earth and other planets and what might be further explored. Often, a follow-up investigation can be considered as moving to the next activity in the Lab notes.

Lab Notes

Characteristics of water flow
Streams shape, volume, and slope

Investigation question
How can different streams be modeled and mapped?

Materials

• Stream-table setup: plastic siphon tubes of different diameters (4mm, 5mm, 6mm), reservoir container, catch container, plastic drain tube,
• Ruler
• Pencil
• Paper

Set up and creating streams

• Set up the stream table with one end raised 12 centimeters higher than the other
• Practice starting and stopping the flow.
• When you can control the flow continue.

• Make a stream and watch the way it flows.
• The grid on the stream table should help you see if the stream goes straight or changes direction.
• Let all the water flow from the reservoir.

• Refill the reservoir and make another steam.
• Does it look like the first one?
• Make more streams to see if they are like the first two.
• Does each stream look a little different?

What similarities were there?

Draw one of your streams.

Which one of these is closest to your drawing?

Explain.

Steams with different shapes and volumes

Investigation question
How can different volumes of water in a stream be modeled?
How does the volume of water affect the size and shape of a stream?

Materials

• Stream-table setup: plastic siphon tubes of different diameters (4mm, 5mm, 6mm), reservoir container, catch container, plastic drain tube,
• Ruler
• Pencil
• Paper

Set-up

• Try a different sized plastic tube and see if different sizes of plastic tubes make different kinds of streams?
• Is the stream different from the first one that you made?

• To be convinced that there is a difference try each of the three sizes several times.
• Make two or three streams with each of the different sized plastic tubes.
• Draw a map for the streams.
• Record the plastic tubes size next to your map.

Tube size ...... Slope ......

Tube size ...... Slope ......

Tube size ...... Slope ......

Tube size ...... Slope ......

Tube size ...... Slope ......

Tube size ...... Slope ......

Summary

Which tube made the widest stream?

The narrowest stream?

How does the size of the plastic tube affect the size and shape of the stream?

How does it effect the volume of the stream?

Streams with different flow rate, slopes

Investigation questions
How can different slopes of streams be modeled?
How does the slope of a stream affect the size and shape of the stream?

Materials

• Stream-table setup: plastic siphon tubes of different diameters (4mm, 5mm, 6mm), reservoir container, catch container, plastic drain tube,
• Ruler
• Pencil
• Paper

Set-up

• Lower the raised end of your stream table about three centimeters to make the slope less steep.
• Make a stream.
• Make more streams until you are satisfied as to the kind of stream that will form.
• Draw a map of your stream.
• Record the size of the plastic tube and the height of the end of the slope.

Tube size ...... Slope ......

Tube size ...... Slope ......

Tube size ...... Slope ......

• Lower the elevated end of your stream table about three centimeters. This will decrease the slope more.
• Make a stream.
• Make more streams until you are satisfied as to the kind of stream that will form.
• Draw a picture of your stream.
• Record the size of the plastic tube and the height of the end of the slope.

Tube size ...... Slope ......

Tube size ...... Slope ......

Tube size ...... Slope ......

Summary

When you have some good ideas about how the slope and different sizes of plastic tubes affect the stream, then answer these two questions:

How do the different sizes of plastic tubes affect the size and shape of the stream?

How does the slope affect the size and the shape of the stream?

Moving the streams into a bed

Volume and Speed in a Stream bed

Investigation questions
How does volume and speed affect a real stream?

Materials

• Stream-table setup: plastic siphon tubes of different diameters (4mm, 5mm, 6mm), reservoir container, catch container, plastic drain tube
• 300 ml coarse sand
• Ruler
• Pencils - blue and brown or black
• Paper

Set-up
Usually streams flow over dirt, rocks, sand, stones, and mud.
We can add sand to model these and see.

Making a dam

• Dampen the coarse sand with a little water.
• Carefully pour the sand onto the upper end of the stream table.
• Then spread the sand out between the lines on the table as shown in the picture.
• Make sure the sand is as flat as possible.
• Now make a channel in the dam.
• The channel should be about 2 centimeters wide.
• Again, flatten the sand.
• Slope the stream table so the top end is 12 centimeters high.
• Use the large plastic tube to start a stream flowing.
• Observe where the water flows.
  
• Draw a map of your stream.

Draw on the paper grid where the water flows with a colored pencil.
Show where the sand is with another colored pencil.
Color the map dark where the sand is thick and light where it is thin.
A little hill might look like this:

Next to your map, be sure to record the height of the end of the slope and the diameter of the plastic tube you used.

Your map might look something like this:

Tube size 6mm Slope 12 cm

Begin by seeing how the volume of water affects the stream. Start with the large tube, make a dam, a two cm channel, and see what happens.

Tube size 6mm Slope 12 cm

Based on your observation what kind of stream would you predict a smaller plastic tube will make.

Will it wash away less sand?

Check it out.
Mix the sand.
Rebuild the dam.
Use a plastic tube with a smaller diameter.

Tube size ...... Slope 12 cm

Can you find a way to have less sand wash away when you use the large (6-mm) plastic tube?

Try out your idea.
Again, mix all the sand together and rebuild the dam as before.

Tube size ...... Slope ......

Summary

Was there a difference?

What was the difference?

What did you discover?

No erosion?

The amount of sand erosion is reduced if the slope is lower or the volume of the stream is smaller. What would happen if both variables were reduced so the tube size is 4mm and the slope is 0?

Draw a map to show what you think would happen.

Tube size 4 mm Slope 0 cm

Mix the sand and make a new dam with a two centimeter channel. Refill the reservoir and test your prediction.

Was your prediction correct?

It's hard to tell exactly where the sand is going to move, isn't it?

Draw a map to show where the sand actually moved.

Tube size 4 mm Slope 0 cm

Summary

When you tried to reduce the amount of sand moved by water, did you make the water move faster or slower?

Describe how the speed of the water affects the movement of sand.

Describe how the volume of the water affects the movement of sand.

Write statements about how the speed and volume of water affects the movement of sand. If you described how one variable effected another variable, then that is a hypothesis.

Volume and Speed in a Stream

Investigation question
Can an experiment be created to support or reject the hypotheses about speed and volume described in the previous investigation?
How does water flow, volume and speed, affect sand in a stream?

Materials

• Stream-table setup: plastic siphon tubes of different diameters (4mm, 5mm, 6mm), reservoir container, catch container, plastic drain tube
• 300 ml coarse sand
• Ruler
• Pencils - blue and brown or black
• Paper

Set-up

Use the information in the chart to set-up some models and conduct a controlled experiment to answer this two part question: How does volume and speed effect the flow of a stream?

• Mix the sand and make a new dam with a channel about seven centimeters wide.
• Make streams flow using the four different setups, one at a time.
• Remix and form the sand between each trial.
• Draw a map for each.
• Record the setup data for each map.
• Your maps should show any differences you observed.

Tube size 6 mm Slope 0 cm

Tube size 4 mm Slope 0 cm

Tube size 6 mm Slope 9 cm

Tube size 4 mm Slope 9 cm

Summary

Use the evidence recorded on the maps.

Were your ideas supported?

List observations that support your hypothesis; or write a new hypothesis that is supported by your observations.

Streams Erosion, Transportation, and Deposition

Investigation question
How does water pick up, move, and drop sand in a stream?

Materials

• Stream-table setup: plastic siphon tubes of different diameters (4mm, 5mm, 6mm), reservoir container, catch container, plastic drain tube
• 300 ml coarse sand
• Ruler
• Pencils - blue and brown or black
• Paper

Helpful Vocabulary

• Erosion is the washing away of the sand.
• Transportation is the movement of materials by water.
• Deposition is the dropping of materials from a stream.

Set-up

Make a new dam. It doesn't matter what kind of dam you make, but try to make the very slowest stream you can. Once the stream starts flowing try to keep it going. When the water in the reservoir is almost gone, scoop some more from the catch pail and refill the reservoir.

Watch the dam carefully as it erodes, or wears away.

Here are three sets of questions to help answer the investigation question as you observe the sand being eroded, transported, and deposited.

Set 1

• What size particles move first?
• Do particles on the top or bottom move first?
• What happens to the corners of the dam?
• What shape does the dam become?

Set 2

• Look for a place where sand is being transported. Observe it carefully.
• Does the sand move in a steady stream?
• Watch just one piece of sand as it moves down the steam. How does it move?
• Does the sand affect the water flow?

Set 3

• Watch a place where sand is being deposited.
• Are all the particles of sand dropped at the same place?
• Does sand affect the water flow?
• Find two or three places where sand is being deposited. Can you tell why this is happening?
• Put your finger in the stream where sand is being transported. What happens to the water?
• What happened to the sand?

On what did set 1 focus observation?

On what did set 2 focus observation?

On what did set 3 focus observation?

Now make a faster flowing stream.

Observe erosion, transportation, and deposition.

Summary

Draw a picture to show and words to describe how does water picks up, moves, and drop sand in a stream?:

Water flow causes sand to be picked up ...

Water flow causes sand to be moved ...

Water flow causes sand to be dropped ...

Movements of sand, erosion, and deposits

Investigation questions
How does size of particles effect movement?
How are deposits formed from stream flow?

Materials

• Stream-table setup: plastic siphon tubes of different diameters (4mm, 5mm, 6mm), reservoir container, catch container, plastic drain tube
• 300 ml of fine sand
• Sheet of stiff plastic
• Ruler
• Pencils - blue and brown or black
• Paper

Set-up

In this activity you will work with fine sand.

• Remove all the coarse sand from the stream table.
• Pour fine sand onto the stream table, moisten it, and make a dam.
• Choose one of your maps you made when you used coarse sand in activity 2.
• Using the fine sand, make the same setup.
• Then make a stream.
• Observe the flowing water.
• Then draw a map.
• Show the water and sand patterns on your map.
• Record the plastic tube size and the height of the stream table.
  

Tube size ...... Slope ......

Which best describes what happened?

• More fine sand moved than coarse sand.
• Less fine sand moved than coarse sand.
• The same amount of fine and coarse sand moved.

Select another map from the coarse sand experiments.

• Set up the stream table just as you did for that map. See how good records are helpful?
• Make the water flow.
• Draw a map of the sand and water patterns.
  

Tube size ...... Slope ......

Compare your map showing fine sand and your map showing coarse sand.

Was more, less, or the same amount of sand moved?

How does the particle size of sand affect the amount of sand moved by a stream?

If you are not sure how the particle size of sand affects its movement, find another map, set up the stream table just as you did for coarse sand, make a stream flow, and collect more information until you are sure.

Set up the stream table so that you will get a medium flow of water. Then, make a dam (it doesn't matter what kind) and start the stream flowing. Let the stream run long enough so that you can see the pattern of deposition. Now stop the stream.

After the water stops flowing, lay the plastic sheet on the stream table about 20 centimeters below the dam. Place a pencil under the bottom of the sheet parallel to the lower edge.

Let the stream flow over the sheet. Observe what happens.

What happened to the speed of the water as it flowed over the plastic sheet?

If you are not sure, put a tiny piece of paper on the water at the top of the stream table. Notice if the paper changes speed as it moves down the stream.

Do you think that changing the speed of the water might cause deposition?

Write an explanation for your idea.

When a stream drops material it is carrying, the deposit is called a fluvial (flu've-al) deposit. Sometimes the stream drops some of its load just after it passes through the dam.

Another kind of fluvial deposit is called an alluvial ( a-lu've-al) deposit. It generally occurs where a stream widens as it leaves a valley.

When the stream hits the pond, almost all of its load is dropped. This is called a deltaic (del-ta'ik) deposit. This kind of deposit occurs when a stream enters a pond, lake, bay, or ocean.

When the stream changes speed, as it flows over a plastic sheet, deposits are left along the stream bed. These are also fluvial deposits. They occur as a stream changes speed or direction along its course.

Summary

Use your explanation to explain all three types of deposits.

Putting your ideas to the test

Design a model that will make as much alluvial deposit with as little deltaic deposit and other fluvial deposits as possible.

Arrange your stream table any way you wish and try different combinations until you find one that makes large alluvial deposits.

Map your model, describe the method for forming the deposits, and explain what is happening to create a large alluvial deposit.

Alluvial deposits

Tube size ...... Slope ......
Notes:

Design a model that will make as many fluvial deposits as you can with very little or no alluvial or deltaic deposits.

Try making channels of different widths, changing the height of the end of the stream table, and using plastic tubes of different widths. When you are sure that you have found the best way for making the deposits, map your model, describe the method for forming the deposits, and explain what is happening to create a large alluvial deposit.

Need a hint: use your explanation for how changing water speed affects alluvial and fluvial deposition.

Fluvial deposits

Tube size ...... Slope ......

Make two deltas that are very different. Map and explain each.
Delta 1

Tube size ...... Slope ......

Delta 2

Tube size ...... Slope ......

Summary

Not all rivers have deltas, there are many reasons why this is so. Try to think of as many as you can.

Describe how different sizes of sand are moved in streams.

Describe how different sizes of sand are deposited in streams.

Optional activity

Have you noticed black particles in the sand?

Make another dam, it doesn't matter what kind. Then make a stream that flows very slowly. Watch the movement of the black sand. Where is it deposited?

Why do you think the black particles are separated from the light-colored ones?

Most of the light-colored sand is quartz. What are the black particles?

Where could you find more information about sand?

Erosion deposition and meandering streams

Investigation questions
Why do streams curve in different places?
What makes the difference if a stream flows straight or makes loops and curves?

Materials

• Stream-table setup
• Plastic tubes of different diameters (4-mm, 5-mm, and 6-mm)
• Metric ruler
• Colored pencils
• 600 ml mixed sand (coarse and fine-sand)

Set-up

• Remove all the sand in the stream table.
• Replace it with twice as much mixed sand, 600 milliliters, and make a dam.
• Dampen the sand with a little water.
• Pour the mixed sand onto the stream table.
• Make a wide dam,.
• Use your finger or a pencil to make a big C channel in the sand.

Let the stream flow down the table and observe what happens in the channel.

Map what happened to the sand. Be sure to write the size of the plastic tube and the height of the end of the slope.

Tube size ...... Slope ......

Mix the sand and make another C channel. This time adjust the end of the slope so the water will flow faster. Observe the pattern of erosion and deposition along the channel. Map the pattern.

Tube size ...... Slope ......

Make one more C channel, but this time make the water flow very slowly. As it flows, look for erosion and deposition along the channel.

Usually erosion and deposition occur at different places along a curved channel. As you keep the water flowing slowly, watch the inside and the outside edges of the curve.
Where does erosion occur?

Draw a map of the channel. Mark an "X" wherever the sand eroded and show depositions in a dark color.

Tube size ...... Slope ......

Now make a smaller "C" channel like this:

Let a very slow stream flow through it. Does erosion and deposition occur at the same places as for the larger C channel?

Do you think that erosion generally occurs at the same place along a curved channel?

Map and mark X's wherever you think erosion occurs.

Tube size ...... Slope ......

What happens to a C channel in a faster stream?

Both the C diagram and your written explanation might be a hypothesis if you described how the change in one variable will change another variable.

You can test your hypothesis with an even smaller C channel. Try one like this:

Use a very slow stream for your test.

How do you think the channel will erode when you start the water flowing? Show your prediction by making a map.

Tube size ...... Slope ......

Start the water flowing and look for places where erosion occurs. Draw them and describe which of your explanations was supported.

Tube size ...... Slope ......

You can also test your hypothesis with S curves. Mix the sand and make an S channel like this:

What will happen to the channel if the stream is very fast? Try it and see. Is one of your hypothesis supported?

What do you think will happen as a very slow stream moves through an S channel? Draw a map to show your prediction.

Tube size ...... Slope ......

Mix the sand and make the channel. Set up the stream table for a slow stream, and let it flow. Draw a map to show what happens. Next to your map, explain what is happening by describing how one variable change causes another variable to change (hypothesis) and describe observations to support it.

Tube size ...... Slope ......

Brain Busters:
Try to make a stream that will flow in "S"-shaped channels.

Here are some to try:

You can think of many more. Try them and make a drawing of those that work and explain why.

Tube size ...... Slope ......

Tube size ...... Slope ......

Can you make a channel so that water will flow uphill, even for a very short distance?

You have discovered what S channels become if the water flows very fast.

Can you get an S or C channel to form all by itself?

If not try some more experiments.

Summary

Describe how erosion and deposition occur in different places in a curving stream.

Describe why some streams flow straight and others make loops and curves.

Expansion Activities:

Investigation questions
How does the movement of sand change the angle of the channel, the number of channels, and the location of the channels?
How do different kinds of objects speed up or slow down the movement of sand?

Materials

• Stream-table setup
• Plastic tubes of different diameters (4-mm, 5-mm, and 6-mm)
• Metric ruler
• Colored pencils
• 600 ml mixed sand (coarse and fine-sand)
• Large stone
• 600 ml of soil
• Grass seeds

Set-up

• Remove all the sand in the stream table.
• Use a mixture of coarse and fine sand on the stream table.

These activities are questions to investigate. To answer each question, you will probably want to make the stream flow at several different speeds. You can make a dam of any width, although the pictures show dams that are 30 centimeters wide.

How does the sand move when you have two channels like this?

What will happen if you have two channels like this?

Or this?

Or this?

What will happen with many channels instead of two?

What about this pattern?

What happens if you put an object in the channel?
How do you think the sand will move?

What would happen if the stone was at another position in the channel?

Tube size ...... Slope ......

What if a pencil were put in the channel (like a tree or beaver dam, or ...) ?

Does the position of the pencil make a difference? How?

Tube size ...... Slope ......

Changing sand and gravel to soil

If you use soil to make a dam do you think you will get the same results?

Remove the sand from the stream table and put in an equal amount of soil.

Repeat some of the tests, with soil instead of sand, that you have just done.

Does the soil interact the same as the sand?

Explain why the soil interacts the way it does?

How would growing seeds in the soil affect the way that the dirt moves?

Grass grows fairly quick so it could be grown or a clump of sod could be used to save time from having to wait for it to grow.

Start with a very slow stream.

Slowly increase the speed of the water.

Do plants affect erosion?

Describe the erosion and channeling.

Tube size ...... Slope ......

Here are some more grids for more experimenting:

Tube size ...... Slope ......

Tube size ...... Slope ......

Tube size ...... Slope ......

Summary

Describe how the movement of sand is affected by the angle of the channels, the number of channels, and the location of the channels.

Describe how different kinds of objects speed up or slow down the movement of sand.

Expansion Resources

• Watersheds & inquiry activities and plan for middle level
• Irrigation and runoff - A great source with data and model to suggest lower water tables can reduce flooding and improve irrigation management. The Water Machine of Bengal: A data-driven and policy-supported strategic use of aquifers for irrigation is needed to maximize their benefits. Science September 16, 2022.

Top

Dr. Robert Sweetland's notes
[Home: homeofbob.com & thehob.net ]