STREAM TABLE LAB – Observing Stream Erosion And Deposition
NAME
DATE
Running water is the dominant agent of erosion on Earth’s surface. A stream’s ability to transport
sediment depends on its gradient, speed and discharge. Stream flow changes between the headwaters and
the mouth (base level), resulting in development of different characteristics along a river’s course.
Pre-Lab Questions -- Predict the following.
1. Where will a river erode more, near its headwaters or near its mouth?
2. Where will a river deposit more sediment?
3. What happens to stream load, in terms of amount and grain size, as the speed of the water increases?
4. What will happen to the speed of a river as its gradient decreases?
5. Where in a meander does a river erode sediment and where does it deposit sediment?
Objective: to compare the effects of stream gradient, speed and discharge on erosion and deposition in a
stream and to recognize patterns and features in stream development.
Materials: stream table, sediment, water, pump, hose, buckets, textbooks, colored pencils
Procedure – Review the entire procedure with your group before beginning the lab. Decide who will
be responsible for what parts of the equipment operation.
1. The stream table is set up and ready to go. Listen carefully to the instructions about pump operation.
Be sure that there is always water in a bucket ready to pour into the pump basin. BE SURE THAT
THE PUMP NEVER RUNS DRY – turn the power switch OFF immediately if the water level in the
pump basin gets too low. USE CAUTION WHEN OPERATING THE ELECTRIC PUMP
AROUND WATER. Watch your step around the lab area and clean up any water spills immediately.
2. Begin with a gently sloping stream – the stream table is propped up with ONE textbook under the
upstream (pump) end. The sediment should be smoothly packed in the top half of the tray with a
relatively smooth sand surface that slopes gently away from the pump towards the downstream end of
the tray, banked slightly higher along the sides of the tray.
3. Start with a pump basin filled with water. Do not overfill the basin. Be sure the hole at the
downstream end of the tray is over the sink. Note where the intake hole is at the base of the pump –
the water should never fall below this level. Refill the buckets each time you add water to the basin
so that there is water ready when needed to refill the basin. Two people in the group should be
responsible for checking the water level in the basin and keeping the buckets filled.
4. The hose from the pump will flow into the small tray at the upstream end of the stream table. Be sure
the hose stays in place during operation. Turn on the switch for the power supply. Slowly turn the
dial until water starts to flow through the tube and into the small tray and begins to “rain” down on
the sand. Adjust the flow until there is a slow, continuous rain. You may need to turn the dial higher
to start the flow, but dial it back to the lowest possible flow. Take a minute or two to adjust the flow
then turn the pump OFF using the switch on the power supply. Note the setting on the power supply
dial here:
Maintain this slow but steady flow throughout the lab.
5. Turn on the pump and let the water flow for about 5 minutes. Keep adding water to the pump basin
as needed. Watch as a stream forms. Carefully observe how the stream develops and changes over
time. Note where sediment is eroded (picked up) and deposited (dropped) by the stream. Observe the
different parts of the stream load (bed load versus suspended load).
QUESTIONS
a) Which particle sizes move faster and farther? (Take a look at what makes it to the end of the
stream.)
b) Which particle sizes move the slowest or not at all?
c) What particle sizes move as bed load?
Describe HOW the bed load
moves – look for evidence of traction and saltation.
6. After 5 minutes, stop the water flow by turning off the switch on the power supply.
7. In the box below, sketch what the stream looks like after 5 minutes. Show the main channel and any
smaller channels that were active and/or abandoned during flow. Use ARROWS to show flow
direction(s). LABEL areas where the stream was eroding and depositing sediment – look for signs of
erosion and deposition in the channel, along the sides of the channel, and at the end of the stream.
LABEL identifiable features. These may include: headwaters, mouth, rapids, point bars, cut banks,
meanders, abandoned meanders, delta, floodplain, braided channels, distributary channels, oxbows.
Refer to your river notes to identify features and processes.
Sketch 1
8. Refill the basin and buckets. Turn on the pump. Let the water run for 2 more minutes at the same
flow rate as before. Carefully observe any changes in the stream.
9. Increase the flow SLIGHTLY by turning the dial up the dial on the power supply – an increase 5 to
10 on the power supply will create a significant change in discharge. Let the pump run at this higher
rate for about ONE minute. Watch the water level in the pump – you will use water faster than
before.
10. After the 1-minute “flood”, DECREASE THE FLOW to the original rate and run for 2 more minutes.
Stop the pump by turning off the power switch.
Sketch the stream, following the same instructions as in Sketch 1. Show where erosion and
deposition occurred and label features. Focus on changes that occurred during and after the flood.
Sketch 2
11. Refill the basin and buckets. Turn on the pump and run for 2-3 minutes at the original setting. Turn
off the pump. Make final observations and sketch the results below; label the features.
Sketch 3
12. SUMMARIZE how the stream changed over time. Consider changes in channel width and depth,
numbers of branches, sediment load, and development of features like meanders, bars, delta,
floodplain, etc. How did the flood affect the river and its features? Did the river recover after the
flood?
13. Carefully add a second textbook under the upstream end to increase the slope of the stream. Repack
the sand in the upper half of the tray – you are starting a new stream with a steeper gradient. Refill
the basin and buckets. Turn on the pump and let the water flow at the original rate. Observe the
stream for 4-5 minutes. You do not need to make a sketch, but list observations in the space below.
Observe how flow changes with a steeper stream in terms of gradient, speed, stream load, amount and
location of erosion and deposition, and development of features.
KEEP AN EYE ON THE WATER LEVEL IN THE PUMP BASIN and refill as needed.
Observations of Steeper Stream
14. Turn off the pump and turn the power supply dial back to ZERO.
Repack the sand as it was at the beginning of the lab.
Remove one of the books.
Use towels to dry any spills of water around your area.
Clean up any spilled sand and put it back into the tray.
Refill the basin and buckets so that the station is ready for the next class.
Failure to properly clean your station will result in loss of 20 points from your lab grade.
Analysis and Conclusions
Fill in the blanks choosing from the following: increased, decreased, remained the same.
As the slope of the stream increased, the speed of the stream
and the rate of erosion
. As discharge (flow volume) increased (during flood stage), erosion
and the amount of sediment load moved by the river
. As flow decreased,
erosion
and deposition
, especially at the mouth
where a deposit called a
formed.
3.
Which graph below best shows the relationship between particle sizes in the stream load compared to
speed of stream? Circle your choice.
Speed 
Particle Size 
Particle Size 
Speed 
2.
Speed 
Label the headwaters & mouth on each sketch in the lab. Where along the stream is erosion
dominant, near the headwaters or near the mouth?
Where in the stream is
deposition dominant?
Speed 
1.
Particle Size 
Particle Size 
4.
Sketch a graph that shows the relationship between speed and amount of deposition in a stream.
5.
What particle sizes tend to move in the suspended load of a stream? (Not sure? See what got washed
into the sink.)
Where along a river’s course is the suspended
load deposited?
What particle sizes comprise the bed
load?
WHY?
6.
As a meander develops in a stream channel, where in the meander does deposition occur (on the
inside or outside?)
Where does most erosion occur?
7.
Show on the diagram below where erosion (E) and deposition (D) occur along the meandering
stream. Place the letters “E” and “D” on the diagram where they are appropriate. Label the possible
location of one point bar and one cut bank.
Flow direction
8.
Explain why, in terms of speed, the pattern of erosion and deposition occurs along a meandering
stream as shown in question 7.
9.
Describe some shortcomings of this stream model in terms of its ability to represent what can happen
in the development of a river over time. What types of features were difficult to observe and why?
Suggest possible ways to improve the experiment.