Science Fair
Project
Riprap: Not Hip-Hop But
Erosion Stop
By Maddison Schink
Lopez Elementary
Statement of the Problem
Which type of
riprap works
best at slowing
erosion (fine or
coarse)?
Project Overview
I chose this topic because after I had taken
an easy, and quick quiz on sciencebuddies.org,
they showed me a few projects that I might find
interesting. I scanned the list, but this project
was the one that really caught my eye. I never
really had thought about the water that came out
of my sink, but in this project I would test which
type of riprap worked best at slowing erosion,
so that not as much dirt, and other particles
would be in our water. I was fascinated that they
could somehow slow erosion, and I thought I
would learn a lot by doing this project.
At the same time, in science, we were
doing stream tables. The purpose of the stream
tables was to teach my classmates, and I about
what erosion can do. I thought the topic of my
project would go well with what we were
learning in school. Then I knew, that it was the
perfect project for me.
Research
• Water Displacement and Archimedes’ Principle: Water
displacement occurs when an object is dropped (immersed) in a
fluid, like water. This object pushes the fluid out of the way, and
takes it’s place. This causes the water level to rise. The volume of
the object put in the fluid, is the exact volume the fluid will rise.
Basically, an object that sinks displaces the amount of fluid equal to
the volume of the object. The buoyancy is expressed through
Archimedes’ Principle, which states that the weight of the object is
reduced by it’s volume, and then multiplied by the density of the
fluid. If the weight of the object is less than this displaced quantity,
the object floats; if more, it sinks.
• Erosion: Erosion is when the process we know as weathering
breaks up rock, so that it can be carried away by the process
known as erosion. The three agents of erosion are water, wind, and
ice. This does also include waves. They all wear away at the surface
of the earth, and carry those particles from the earth with them.
Erosion can cause various different landforms to occur.
For example, canyons, deltas, and plateaus are just a few of the
landforms that can occur because of erosion. The mighty Grand
Canyon in Arizona is one of many beautiful landforms that erosion
has formed. This particular canyon was formed by the fast-flowing
water of the Colorado River.
Research
• Riprap: Riprap is usually rock ,but can be made out of another
material, and is used to armor shorelines, streambeds, bridge
abutments, pilings and other shoreline structures against scour ,
water, or ice erosion. Also, when made out of rock, it is most
commonly made of granite or limestone. Occasionally, it is made
from concrete rubble from building and paving demolition. It can
also be used to protect coastlines, and structures from erosion by
sea, rivers, or streams. Waterways, and water containment where
there is potential for water erosion, is another place where riprap
can be used.
• Civil and Environmental Engineers: A Civil Engineer is someone
who works in a professional engineering discipline that deals with
the design, construction, and the maintenance of the physical and
naturally built environment. This includes works such as roads,
bridges, canals, dams, and buildings.
An Environmental Engineer is one who
works in the application of science and engineering
principles to improve the environment. These people
try to improve the air, water, land, and it’s resources
in order to provide healthy water, land, and air for
humans, plants, animals, and other living organisms.
Research
Definitions:
• Fine (adjective)- Very small in weight, or
thickness: not thick, coarse, or dull
• Coarse (adjective)- Composed of
relatively large parts or particles: rough
or loose in texture
• Force (noun)- Strength; energy; power;
intensity: a personality of great force
Variables
• Controlled variables: My controlled variables are
the amount of water I use, the amount of sand I use,
the amount of coarse gravel I use, the amount of
fine gravel I use, and how long I wait after I pour
the water in.
• Independent variable: My independent variable
was whether I used one, or two layers of riprap in
the rain gutter.
• Dependent variable: My dependent variable is
how much water gets through the type of riprap
I’m testing.
Hypothesis
Hypothesis: If I use finer riprap,
then I think less water will get
through. I think my hypothesis will
be correct because I believe that
with the coarse gravel, the water
will just be able to go over and
around the bigger rocks easier
than with the small rocks.
Therefore, I think the fine riprap
will work better.
Materials
•
•
•
•
•
•
•
•
•
•
•
•
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One 4-6 feet of a rain gutter- found at Home Depot
One sturdy box or stool- found in my garage
One dry measuring cup- found in my kitchen
One 4-cup liquid measuring cup- found in my kitchen
50 pounds of play sand- found at Home Depot
4 gallon-sized plastic baggies- found in my kitchen
Fine gravel approximately 1/16th to 3/8th inch, need approximately 2
gallon-sized plastic bags full- found at Home Depot
Coarse gravel approximately 1/2 x 1/2 x 1 inch, need approximately 2
gallon-sized plastic bags full- found at Home Depot
Stopwatch- my watch at home
Lab Notebook- school supplied
Source of water- sink at home
Place to dump water, sand, and rocks- my front yard
Paper, or graph paper- found in lab notebook
Procedure
•
Step 1: Gather your materials for the experiment.
•
Step 2: Set up materials by first placing the swivel-end of the extender on the box or stool, and
place the other end on the liquid measuring cup. Extender should be slightly higher than the
end resting on the liquid measuring cup.
•
Step 3:Test four types of riprap three times by first sprinkling sand evenly over the gutter part if
the extender, and record how much sand you use each time. You should use the same amount of
sand every time you run the experiment.
•
Step 4: Make a graph like this one:
Riprap
Type
Control:
No Riprap,
Only Sand
Sand+
Fine
Gravel
Sand+
Coarse
Gravel
Sand
+Fine+
Coarse
Gravel
Trial 1
Water
Level
Trial 2
Water
Level
Trial 3
Water
Level
Sum
of
Trials
Average
of Trials
Procedure
•
Step 5: Measure out three cups of water in a liquid measuring cup, and pour it all at once into the
swivel-end of the extender.
•
Step 6: Wait 3-5 minutes to allow all the water to completely drain out of the gutter. The exact time
you wait is not critical. Just make sure you wait the same amount of time for each trial in the
experiment. Record in your lab notebook about how much time you waited.
•
Step 7: Record the water level in the liquid measuring cup.
•
Step 8: Dump and rinse out the water in the liquid measuring cup.
•
Step 9: Thoroughly rinse out the gutter.
•
Step 10: Repeat steps 3-8 two more times using only sand on the gutter.
•
Step11: perform steps 3-8, this time using sand by 1 cup (or more as needed) of evenly distributed
fine gravel. Record in your lab notebook how much fine gravel you needed to evenly cover the
sand. Perform 3 times total.
•
Step 12: Perform steps 3-8 three times, using sand topped by a layer of coarse gravel ( evenly
distributed). Record in your lab notebook how much coarse gravel you needed to evenly cover the
sand. Again, make sure to use the same amount of sand and coarse gravel each time you do a trial.
Procedure
•
Step 13: Finally, perform steps 3-8, three times with the sand topped by a layer of coarse gravel
and then topped by a layer of fine gravel (evenly distributed). Use the same amount of sand and
fine and coarse gravel for each trial, recording the amount of each, in your lab notebook.
•
Step 14: Plot your results for each type of riprap on the regular or graph paper. Which type of
riprap displaced the most water? This is the type of riprap that did the poorest job at preventing
erosion. Which type of riprap displaced the least amount of water? This is the riprap that did the
best job at preventing erosion.
Data/Observations
The Best Riprap
Riprap
Type
Trial 1
Water
Level
Trial 2
Water
Level
Trial 3
Water
Level
Sum of
Trials
Average
of Trials
Control:
No
Riprap,
Only
Sand
2
Cups
2½
Cups
2½
Cups
7
Cups
2⅓
Cups
Sand+
Fine
Gravel
2
Cups
2
Cups
2¼
Cups
6¼
Cups
2 1/12
Cups
Sand+
Coarse
Gravel
2¼
Cups
2½
Cups
2¼
Cups
7
Cups
2⅓
Cups
Sand+
Fine+
Coarse
Gravel
2
Cups
2
Cups
2¼
Cups
6¼
Cups
2 1/12
Cups
Conclusion
Based on the results of my experiment, I found that fine gravel worked best at slowing
erosion. In my Hypothesis, I predicted that the finer riprap would do it’s job best, and my
hypothesis was accepted or correct. I noticed that the fine riprap worked best because it slowed
and, trapped the water while it was running down. With the coarse gravel, it slowed the water
better, but only trapped the water in two or three little pools, and didn’t nearly catch as much as
the fine gravel did overall.
This information may benefit our society because both environmental, and civil
engineers would know which type of riprap works better at preventing erosion. Then, riprap could
protect shorelines and riverbanks from being eroded away by water.
The scientific principles involved in my outcome are the force of the water, the erosion
and deposition, and the unnatural object blocking the flow of the water, in this case the riprap.
These are my scientific principles involved in my outcome because they all state why my project
reacted, and happened the way it did. For example, the force of the water and the slope of the
extender made the water flow faster, but the riprap was blocking it’s path, and keeping it from
eroding the channel. The water that did pass, still deposited sand though, and sometimes the force
at the end of the extender was still strong and would push riprap along with it. Without any riprap
though, the water was faster, had a lot more force, eroded many channels, and wiped away most of
the sand.
If I could change something in my experiment, I would probably test a fifth type of
riprap. Even though it is usually rocks, it can be made from several different materials. For
example, I could have used bark. Engineers would then have another type of riprap that could be
used, if it was proven to do a good job.
Works Cited
1. Dictionary.com, December 9, 2010 (date accessed).
http://dictionary.reference.com/
2. “Fine,” Merriam-Webster’s Intermediate Dictionary
1998, pg.282
3. Hughes, Stephen W. “Displacement (fluid).”
Wikipedia.org, 2005.
http://en.wikipedia.org/wiki/Displacement_(fluid)
4.Merriam-Webster.com, December 9, 2010 (date accessed).
http://www.merriam-webster.com/dictionary
5. Rosenberg, Matt. “Erosion.”
About.com, December 6, 2010 (date accessed).
http://search.about.com:?q=erosion
6. Wiki/answers.com, December 9, 2010 (date accessed).
http://www.wiki.answer.com/
Acknowledgements
I would like to thank my Mom, Dad,
Bailey, Lily, and Mr.Kuhne for making it
possible to run my experiment smoothly,
and understand the science of my project. I
would also like to thank them for helping
me with my PowerPoint and Science
Report. Without them, my project would not
be as complete and interesting. Thank
You!!!!!