The Effect of Slope Angle on the Amount of Eroded Material

Researched by Alex Y.
2003-04

PURPOSE





The purpose of this experiment was to determine the effect of slope angle on the amount of material eroded by water.

I became interested in this from a science unit in fifth grade called “Rivers”.

The information gained from this experiment might help farmers, road builders, and land architects prevent soil from eroding away. It could help geologists prevent mud slides and other natural problems associated with water erosion.
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HYPOTHESIS





My hypothesis was the steeper the slope angle the more material will be eroded.  

I based my hypothesis on the Internet site called WWW. factmonster. com that said, “The principal agents of erosion are gravity, running water, near shore waves, ice (mostly glaciers), and wind. ”
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EXPERIMENT DESIGN

The constants in this study were:
 

  • Amount of water used in each test
  • Force of water flow at starting point
  • Size of erosion box
  • Soil type
  • Material layer pattern in erosion box
  • Testing procedures
  • Method of measuring eroded material
  • Soil amount


The manipulated variable was the steepness of the slope in the erosion box.

The responding variable was the amount of eroded material.

To measure the responding variable I caught all of the eroded material in a bucket and after draining the water used a triple beam balance to determine the mass.
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MATERIALS

QUANTITY ITEM DESCRIPTION
1 15 in. x'ing. Erosion box
4000 g. Soil (per test)
1 Triple Balance Beam
1 Bottle
1 Clock or timer
1  Bucket to catch eroded material
1 Drainer
28 Standard Lego Blocks
1 Scientific Calculator
1. 5 gallons Water Per Test
2  Pitchers
Plenty coffee filters

PROCEDURES

1. Build erosion box.  
2. Create a constant flow system
A. Find a bottle with a lid.
B. Poke a small hole in the lid.
C. Cut out the bottom of the bottle
D. Fill 2 pitchers for an unlimited water supply.  
3. Put 4000 g of soil in the erosion box.
4. Use calculator to figure out angles.
A. Place lego's under closed end of box.
B. Measure height of the closed end of box from bottom surface to bottom of box.
C. Calculate angle.
1. Divide height by length of box.
2. Find the Inverse sine (sin ?1).
3. Output is the degree of the angle.
5. Fill bottle with water with your finger over the hole.
6. Start timer when you let your finger off of the lid.
7. Let water run for 10 min.
8. Sift dirt out of the water with the coffee filters.
9. Put material into a bowel or on a cloth to dry.  
10. Set aside eroded material to dry.
11. Repeat steps 3 through 10 for the other angles.
12. Weigh eroded material.
A. Put soil in a bowl
B. Weigh filled bowl 
C. Empty the bowl
D. Weigh bowl
E. Subtract the weight of the empty bowl from the weight of the full bowl and you have the weight of the soil
11. Repeat step 10 for other amounts of soil.
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RESULTS

The purpose of this experiment was to determine the effect of slope angle on the amount of material eroded by water.

The results of the experiment were when I put the material at 10 degrees the water eroded 6. 5 grams of material, but when I put it at 30 degrees the water eroded 862 grams of material.  

See my data table and graph below.

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CONCLUSION

My hypothesis was the steeper the slope angle the more material will be eroded.

The results indicate that this hypothesis should be accepted, because the steeper the angle of the soil was the more the material was eroded.  

Because of the results of this experiment, I wonder if the temperature or time of year would affect the amount of eroded material. I also wonder if the type of soil or the amount of plant growth in the soil makes a difference.  

If I were to conduct this project again I would use plain dirt. I would also make sure that my box doesn’t have a leak. I would use a better sifting method. I would conduct each test more than once.
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RESEARCH REPORT

Introduction

Erosion is a natural process by which rocks and soil are broken up and transported to a new location. There are a few specific things that cause erosion: water flow (as in the Grand Canyon), wind movement, and glacial movement.  

Water Erosion

Water erosion is one of the most significant natural forces throughout the world. Two main variables affecting water erosion are precipitation and surface run off.  

Process

Erosion carries weathered and broken down particles or materials down riverbeds. Large rocks can even be eroded in a stream or river. When particles in water scratch away at a rock they slowly break it down, once it is light enough to be carried down the river bed the water forces it along until it hits a slow part in the river, here it will fall to the bottom if the water isn’t moving fast enough. Each year all of the rivers in the US deposit 3. 5 tons of eroded material in to the ocean.

Raindrops

Raindrops are the most common form of precipitation, and can be very destructive when they strike bare soil. When the raindrops hit the ground at over 20 mph, they splash grains of soil into the air and wash out seeds. Then surface run off or overland flow carries away the detached soil, witch can be deposited elsewhere.

Accelerated Water Erosion

There are four kinds of accelerated water erosion that are commonly recognized: Sheet, rill, gully, and tunnel. Sheet erosion is uniform removal of soil from an area without the development of water channels. Rill erosion is the removal of soil by the cutting of many small, but conspicuous, channels where runoff concentrates. Gully erosion is the result of water that cuts down into the soil along the line of flow. Tunnel erosion may occur in soils with horizons or layers that are more subject to entrainment in moving free water than is the surface horizon or layer.  

Controlling Water Erosion

You can help control water erosion by leaving stems, leaves, and stalks from previously harvested crops. You can also help by planting trees and bushes to protect bare soil.  
 
 

Wind Erosion

Wind erosion is the action of wind on exposed sediments and friable rock formations. Wind erosion occurs in arid or semi-arid lands. Wind erosion cannot be divided in to such distinct types like water erosion. It occurs mostly on dry, flat plains or moist sandy soil like on beaches. It also causes dryness.  

The diagram below me got from http://www. soils. ecn. purdue. edu/wepphtml/wepp/wepptut/jhtml/wndersn.html shows how 
How wind erodes sand. Wind can also reduce vegetation cover, topsoil, seeds, and nutrients.

Wind erosion is a big problem in many parts of the world, and can be worse in a drought. Wind erosion 

Glacial Erosion

Glacial Erosion can create landforms, carry heavier things such as boulders, and sculpt the land beneath them. Glaciers can carve sharp “V” shaped valleys into smooth “U” shaped valleys. Glacial erosion can occur more than 500m below sea level.  

Mechanical and Chemical Weathering

Rock can be weathered by mechanical and chemical weathering. They both occur constantly in most environments.

Mechanical Weathering

Mechanical weathering breaks rocks and minerals into fragments. It has many examples: frost wedging, crystal growth, mechanical exfoliation, root penetration, thermal expansion, and abrasion. Frost wedging occurs when water gets into cracks in rocks, freezes, and expands, dislodging pieces of the rock. Crystal growth takes place when salt water gets into cracks in a rock then evaporates leaving salt crystals to grow and break the rock. Mechanical exfoliation is when rocks expand and crack. Root penetration occurs when tree roots grow into rock fractures. Thermal expansion and contraction is the enlargement and reduction of crystal shape in response to heating and cooling. Abrasion is when minerals and rocks collide in a moving current.  

Chemical Weathering

Chemical weathering converts the chemical composition of unstable rocks and minerals to more stable substances. Chemical weathering also has a few examples: dissolution, oxidation, and hydrolysis. Dissolution is when soluble compounds are dissolved. Oxidation is when mineral ions and oxygen combine to form oxide. And hydrolysis is when H+ ions displace other ions to form a different mineral.  

Summary

Erosion can do a lot of damage so try to protect your land by planting trees and leaving dead roots from plants in the ground.
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BIBLIOGRAPHY





Chernicoff, Stanly and Fox, Haydn. Essentials of Geology. Houghton Mifflin Co, 2003. pp. 97-115

“Degradation of the Land. ” Schlessinger Video. 1993.

"Erosion," Microsoft Encarta Encyclopedia Deluxe, 2001.

Horenstien, Sidney. Rocks Tell Stories. Brookfield, Connecticut:  The Mill Brook Express, 1993. p. 27.

“Soil Erosion,” October 29, 2003. www. Elibrary. Bigchalk. com

“The Problem of Wind Erosion” February 4, 2004. www. weru. ksu. edu/problem.html

Van Rose, Susan. Earth: Eyewitness Science. DK Publishing, 1994. pp. 54-55

“Wind Erosion”January 29, 2004. www. gcrio. org /geo/erosion.html

“Wind Erosion” January 29,2004. Http://WWW. soils. ecn. purdue. edu/wepphtml/wepp/wepptut/jhtml/wndersn.html
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ACKNOWLEDGEMENTS

ACKNOWLEDGEMENTS

I would like to thank the following people for helping make my project possible:
* My dad for helping me with my experiment and any way he could.
* Mr. Newkirk for keeping me on track and not letting me get behind.
* My grandpa for helping me build my erosion box.
* Mrs. Helms for helping me any way she could.
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