Home Store Project Ideas Project Guide Ask An Expert Blog Careers Teachers Parents Students

Riprap: It's Not Hip Hop But Erosion Stop

Difficulty
Time Required Average (6-10 days)
Prerequisites None
Material Availability Readily available
Cost Low ($20 - $50)
Safety No issues

Abstract

Have you ever been to the Grand Canyon and seen what water can do over millions of years? When you turn on the faucet, do you see water come out, or mud? In this experiment you'll find out how engineers help prevent erosion, which keeps dirt out of our water.

Objective

In this science project, you will build a model of a water channel and determine how best to prevent erosion in that channel.

Credits

Kristin Strong, Science Buddies

Adjust-A-SpoutTM is a registered trademark of HSN Improvements, LLC.

Cite This Page

MLA Style

Science Buddies Staff. "Riprap: It's Not Hip Hop But Erosion Stop" Science Buddies. Science Buddies, 22 May 2014. Web. 30 Sep. 2014 <http://www.sciencebuddies.org/science-fair-projects/project_ideas/EnvEng_p024.shtml?from=ParentsBoyScouts>

APA Style

Science Buddies Staff. (2014, May 22). Riprap: It's Not Hip Hop But Erosion Stop. Retrieved September 30, 2014 from http://www.sciencebuddies.org/science-fair-projects/project_ideas/EnvEng_p024.shtml?from=ParentsBoyScouts

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.


Last edit date: 2014-05-22

Introduction

Water has tremendous force, meaning it can carve into soil and even solid rock. As water carves, it picks up little bits of soil and rock and carries them away. This process is called erosion.

Practically any place where water and land meet—river banks, river bottoms, irrigation ditches, canals, shorelines, beaches, or farmland—you'll find civil and environmental engineers working hard to slow erosion. One way they slow erosion is by placing pieces of jagged rock, called riprap, on the land in or around waterways. This riprap blunts or dulls the force of the water so that it cannot break down the soil or carry it away as readily.

In this project you'll build a model of a waterway and see what kinds of riprap (fine or coarse, one layer or two) work best at keeping sand in the waterway and out of the water downstream.

Terms and Concepts

To do this type of project you should know what the following terms mean. Have an adult help you search the Internet or take you to your local library to find out more.

  • Force
  • Erosion
  • Civil engineer
  • Environmental engineer
  • Riprap
  • Fine
  • Coarse
  • Angular
  • Displacement of water
  • Archimedes' principle

Questions

  • What size of riprap works best at slowing erosion (fine or coarse)?
  • What shape of riprap works best at slowing erosion (smooth or angular)?
  • Are multiple layers of riprap better than a singer layer?

Bibliography

Materials and Equipment

To do this experiment, you will need the following materials and equipment:

  • Adjust-A-SpoutTM downspout extender, available at hardware stores or online. An alternative would be approximately 4-6 feet of a rain gutter.
  • Sturdy box or stool
  • Dry measuring cups
  • Liquid measuring cups (4-cup size or larger), need 2. The read-from-above types are easiest to use.
  • Play sand, 50 pounds
  • Plastic baggies, gallon-sized (4)
  • Fine gravel approximately 1/16th to 3/8 inch (shown in Figure 1), need approximately 2 gallon-sized plastic bags full
  • Coarse gravel, approximately ½ x ½ x 1 inch (shown in Figure 1), need approximately 2 gallon-sized plastic bags full

    Environmental Engineering  Science Project examples of fine and coarse gravel (riprap)
    Figure 1. Shown here are examples of fine and coarse gravel (riprap).

  • Stopwatch
  • Lab notebook
  • Garden hose
  • Place to dump water, sand, and rocks
  • Graph paper

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.

Experimental Procedure

  1. Set-up your materials, as shown in Figure 2, first by placing the swivel-end of the extender on the box or stool and the other end on one of the liquid measuring cups. The swivel-end of the extender should be slightly higher than the end resting on the liquid measuring cup.

    Environmental Engineering  Science Project experimental setup showing downspout extended lying across liquid measuring cup and box
    Figure 2. Experimental setup.

  2. You will be testing four types of riprap, three times each. Make a data table to record your observations, as shown below:

    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
    Sand + Fine Gravel
    Sand + Coarse Gravel
    Sand + Fine Gravel + Coarse Gravel

  3. Sprinkle sand evenly over the gutter part of the extender, as shown below in Figure 3. The amount of sand needed to evenly cover the bottom of the gutter will depend on the length of your extender. For example, a 4-foot extender will need approximately 1 cup of sand to evenly cover the bottom, while a 6-foot extender will need almost twice that. Record in your lab notebook how much sand you used so you will remember for each trial. It is important that you use the same amount of sand each time you run a trial in the experiment.

    Environmental Engineering  Science Project child sprinkling sand evenly over the extender
    Figure 3. Sprinkle sand evenly along the extender.

  4. Measure out 3 cups of water into a liquid measuring cup.
  5. Pour the water all at once into the swivel-end of the extender.
  6. Wait 3–5 minutes to allow 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 so you will remember for each trial.
  7. Record the water level in the liquid measuring cup at the end of the extender.
  8. Dump and rinse out the measuring cup.
  9. Thoroughly rinse off the gutter.
  10. Repeat steps 3–9 two more times using only sand on the gutter.
  11. Perform steps 3-9, this time using sand topped by 1 cup (or more, as needed) of evenly distributed fine gravel, as shown in Figures 4 and 5. Record in your lab notebook how much fine gravel you needed to evenly cover the sand. Be sure to use this same amount of sand and fine gravel each time you do a trial.

    Environmental Engineering  Science Project sand topped by a layer of fine gravel in the downspout extender
    Figure 4. Sand topped with a layer of fine gravel in the extender.

    Environmental Engineering  Science Project sand topped with a layer of fine gravel in the extender
    Figure 5. Water poured all at once over the sand and fine gravel layers.

  12. Perform steps 3–9 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.
  13. Finally, perform steps 3–9 three times with the sand topped by a layer of fine gravel, and then topped by a layer of coarse gravel (all 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.
  14. Plot your results for each type of riprap on the graph paper. Which riprap type displaced the most water (had the highest water level reading)? This is the riprap type that did the poorest job at preventing erosion. Which riprap type displaced the least water (had the lowest water level reading)? This is the riprap that did the best job at preventing erosion in the channel. Did two layers work better than one?

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.


Variations

  • Compare smooth, round riprap vs. angular riprap.
  • Compare which sequence works best in layering—fine riprap first and coarse second, or coarse riprap first and fine second.
  • Add a layer of grass seed to any of the riprap types, sprinkle lightly with water, and let it grow until blades can be seen. After the grass has grown, do not water for 2–3 days and then repeat the trial to see if the addition of a plant mat does a better job at preventing erosion than riprap alone.

Share your story with Science Buddies!

I did this project I Did This Project! Please log in and let us know how things went.

Ask an Expert

The Ask an Expert Forum is intended to be a place where students can go to find answers to science questions that they have been unable to find using other resources. If you have specific questions about your science fair project or science fair, our team of volunteer scientists can help. Our Experts won't do the work for you, but they will make suggestions, offer guidance, and help you troubleshoot.

Ask an Expert

Related Links

If you like this project, you might enjoy exploring these related careers:

soil scientist taking soil sample from dry field

Soil Scientist

Not all dirt is created equal. In fact, different types of soil can make a big difference in some very important areas of our society. A building constructed on sandy soil might collapse during an earthquake, and crops planted in soil that doesn't drain properly might become waterlogged and rot after a rainstorm. It is the job of a soil scientist to evaluate soil conditions and help farmers, builders, and environmentalists decide how best to take advantage of local soils. Read more
Chevron civil engineers examine blueprints

Civil Engineers

If you turned on a faucet, used a bathroom, or visited a public space (like a road, a building, or a bridge) today, then you've used or visited a project that civil engineers helped to design and build. Civil engineers work to improve travel and commerce, provide people with safe drinking water and sanitation, and protect communities from earthquakes and floods. This important and ancient work is combined with a desire to make structures that are as beautiful and environmentally sound, as they are functional and cost-effective. Read more
female environmental engineer measuring streamflow

Environmental Engineer

Environmental engineers plan projects around their city or state—like municipal water systems, landfills, recycling centers, or sanitation facilities—that are essential to the health of the people who live there. Environmental engineers also work to minimize the impact of human developments, like new roads or dams, on environments and habitats, and they strive to improve the quality of our air, land, and water. Read more
landscape architect working on plans

Landscape Architect

Have you ever visited a new city and marveled at how nice looking it was? Perhaps the streets were wide, the public places were well organized, and the parks and gardens were green and had lots of attractive plants. Well, what you experienced was a well-balanced and designed landscape plan put together by a landscape architect. Landscape architects design everything that is outside of buildings. Their goal is to make a design that is functional, but one that is well balanced with nature and in which people feel happy and comfortable. Landscape architecture is the perfect blend of engineering, art, and nature. Read more

Looking for more science fun?

Try one of our science activities for quick, anytime science explorations. The perfect thing to liven up a rainy day, school vacation, or moment of boredom.

Find an Activity