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

Overview

Water leaves footprints.

Streams and rivers is where water collects and begin its flow to the oceans. This can create serious consequences for safety, erosion, production of energy and recreational opportunities all which affect the quality of life, health of organism who depends on stream and river environments.

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.

Meander River map smallAt 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

Earth science - Streams and erosion

Big ideas: Streams and rivers are created as water flow down a slope and gathers in channels. These channels are formed by the interaction of the flow down a slope, the volume of water, and the erode ability of the earth materials through which they flow.

Related concepts and facts

  • The volume of water effects the size and shape of a stream.
  • The slope of a stream effects the size and shape of the stream.
  • The kind, size, and shape of earth material effects erosion.
  • Water flow causes sand to be picked up.
  • Water flow causes sand to be picked up and moved.
  • Water flow causes sand to be dropped.
  • Fine sand is moved more easily than coarse sand by streams.
  • Deposits are formed as a result of the streams flow.
  • Erosion and deposition occur in different places in a curving stream.
  • Some streams flow straight and others make loops and curves.
  • The movement of sand is affected by the angle of the channel, the number of channels, and the location of the channels.
  • Different kinds of objects speed up or slow down the movement of sand.

Outcome

Describe the relationships of water flow on erosion and channeling. Describe how earth materials and its surface interact with the flow of water and how volume and speed of flow effect the size, shape, and flow of streams and rivers.

Specific outcomes -

  1. Describe greater volume will create larger channels and faster flow.
  2. Describe rain and run-off as a powerful force that erodes the Earth.
  3. Describe how different flows of water interact with the Earth to create stream beds.
  4. Describe how different flow volume relate to precipitation and run-off.
  5. Describe how speed of the flow relates to the slope, run-off and shape of the channel.
  6. Describe how different earth materials effect the flow of the water by mass, hardness, shape, and location of materials.
  7. Describe how different channels and deposits are created.

Inquiry - processes - constancy, change, measurement - variables relate to observable changes

(How science inquires for understanding: process, skill, methodology, practice)

Observed changes in properties can be attributed to changes of other variables and used to explain cause and effect for the observed change.

Related concepts and facts

  • Observed changes can be described as changes of properties (variables).
  • Variables are observations of a property that changes - size, shape, temperature, amount, volume, rate, ...
  • When people disagree on an observation, they usually make more and better observations.
  • Observation, creativity, and logical argument are used to explain how variable changes effect resulting observations.

Outcome

Describe change as a result of interactions. Describe those interactions as changes of a characteristic/ property (variable) that interacts with the object that changes.

Specific outcomes -

  1. Describe changes as a result of interactions (water interacts with earth materials to erode and create channeling).
  2. Describe interactions as changes of a characteristic/ property (variables) [(erosion, channeling, ...)] that interacts with the force of water created by [(slope, volume, ...)] that changes [(change the Earth)].

Inquiry - processes - evidence, models, & explanation

(How science inquires - process, skill, methodology)

Science or a scientist uses observable evidence to create an explanation.

Related concepts and facts

  • Observed changes can be explained as being caused by changes of variables (changes of properties/ characteristics).
  • Explanations are based on observations.
  • Evidence is observation.
  • Inference is an explanation based on observation.
  • When people disagree on explanations, they can make more observations or change their explanation.

Outcome - processes - evidence, models, & explanation

Make observations of change, identify variables associated with the change, and create explanations of how the variables effect those changes.

Specific outcomes -

  1. Identify variables related to a change (volume, slope,properties of earth materials).
  2. Relate variables to change with an explanation.
  3. Erosion and channeling are evidence that can be used to explain (infer) the history of the water's interactions with the environment over time and used to predict the future.

Activities to provide sufficient opportunities for students to attain the targeted outcomes.

Possible Activity Sequence

  1. Focus student's attention and collect diagnostic assessment information by asking and letting students discuss the focus questions.
  2. Demonstrate how to set up a siphon with the materials which will be used.
  3. Students practice making streams.
  4. Experiment and create streams with different shapes and volume.
  5. Experiment with streams flow rates, slopes.
  6. Begin experimenting with streams in beds (add course gravel) for flow rate and volume
  7. Controlled experiment to test hypotheses about speed and volume.
  8. Streams Erosion, Transportation, and Deposition
  9. Design a model for fluvial: fluvial, alluvial and deltaic deposits.
  10. Erosion, deposition, and meandering streams (shapes of streams)
  11. Expansions activities

Pedagogical ideas

Materials

Focus questions:

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.

Activities

Exploration Activities:

Activity: Characteristics of water flow

 

Lab Notes

Streams shape, volume, and slope: set up and creating streams

Investigation question
How can different streams be modeled and mapped?

Materials

Set up

What similarities were there?

Draw one of your streams.

grid image

Which one of these is closest to your drawing?

three streams image

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

Set-up

grid image Tube size ...... Slope ......

grid image Tube size ...... Slope ......

grid image Tube size ...... Slope ......

grid image Tube size ...... Slope ......

grid image Tube size ...... Slope ......

grid image 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

Set-up

grid image Tube size ...... Slope ......

grid image Tube size ...... Slope ......

grid image Tube size ...... Slope ......

 

grid image Tube size ...... Slope ......

grid image Tube size ...... Slope ......

grid image 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

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

Making a damdam and channel image

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:

Hill image

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:

sample map 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.

grid imageTube 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.

grid image 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.

grid image 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.

grid image 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.

grid image 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

Set-up

Setup Plastic tube diameter Slope
1 large 6 mm 0 cm
2 small 4 mm 0 cm
3 large 6 mm 9 cm
4 small 4 mm 9 cm

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?

grid image Tube size 6 mm Slope 0 cm

 

grid image Tube size 4 mm Slope 0 cm

 

grid image Tube size 6 mm Slope 9 cm

 

grid image 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

Helpful Vocabulary

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

Set 2

Set 3

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

Set-up

In this activity you will work with fine sand.

grid image Tube size ...... Slope ......

Which best describes what happened?

Select another map from the coarse sand experiments.

grid image 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.

deposits image

 

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

grid image 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

grid image Tube size ...... Slope ......

 

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

grid image Tube size ...... Slope ......

Delta 2

grid image 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

Set-up

image

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.

grid image 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.

grid image 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.

grid image Tube size ...... Slope ......

 

Now make a smaller "C" channel like this:

image

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.

grid image 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:

image

 

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.

grid image Tube size ...... Slope ......

 

 

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

grid image Tube size ...... Slope ......

 

 

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

image

 

 

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.

grid image 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.

grid image Tube size ...... Slope ......

 

 

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

Here are some to try:

 

image image image

 

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

grid image Tube size ...... Slope ......

 

grid image 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

Set-up

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?

image

 

 

What will happen if you have two channels like this?

image

 

 

Or this?

image

 

 

Or this?

image

 

 

What will happen with many channels instead of two?

image

 

 

What about this pattern?

image

 

 

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

image

 

 

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

grid image 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?

grid image 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.

grid image Tube size ...... Slope ......

 

Here are some more grids for more experimenting:

grid image Tube size ...... Slope ......

 

grid image Tube size ...... Slope ......

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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.

 

 

Dr. Robert Sweetland's notes
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