Introduction: (Initial Observation)
Erosion is the loss of soil from the land. It is a process that is always occurring and is causing damages to farmlands, roads and buildings.
When it rains, river and stream banks erode, adding soil and silt to the water. That is why river and pond water looks dirty when it rains.
In this project we will study the causes of erosion and see if it can be prevented.
Information Gathering:
Find out about erosion. Read books, magazines or ask professionals who might know in order to learn about the causes of erosion and the ways it might be prevented. Keep track of where you got your information from.
Following are some information about erosion.
Soil Erosion
The rate of erosion can be increased by
- removing plant cover by burning pasture or felling trees, shelter belts or forests and by having too
- many animals on the land
- bad cultivation practices
- wind
- frost
- rain and water runoff and
- extreme climatic effects e.g. Cyclone Bola.
Erosion can be like this.
Erosion can damage roads, bridges and fences. It can cause pollution of waterways and destroy stock when it occurs rapidly.
- Find examples of erosion occurring in your local area.
- Take photographs of these areas.
- Explain why the erosion is occurring.
- Find out what people are doing to:
- prevent erosion occurring
- reduce the effects of the erosion that has occurred.
Question/ Purpose:
What do you want to find out? Write a statement that describes what you want to do. Use your observations and questions to write the statement.
The purpose of this project is to study the causes of erosion and the ways that it can be prevented. Specific questions for this project are:
- How does rain affect the rate of erosion?
- How do vegetations affect the rate of erosion?
Identify Variables:
When you think you know what variables may be involved, think about ways to change one at a time. If you change more than one at a time, you will not know what variable is causing your observation. Sometimes variables are linked and work together to cause something. At first, try to choose variables that you think act independently of each other.
For the first question, the variables may be defined like this:
Independent variable (also known as manipulated variable) is the amount of rain. Possible values are 5cm, 10 cm, 15 cm.
Dependent variable (also known as responding variable) is the amount of erosion. This can be measured by the loss of elevation on a pile of soil or by the amount of sand and soil that is washed away.
Constants are the speed of rain, the size of rain drops, the type of soil, the initial condition (dryness) of soil.
Controlled variables are wind, weather temperature and other environmental factors that may affect the rate of erosion during our experiment.
For the second question, the variables may be defined as below:
Independent variable (also known as manipulated variable) is the amount of vegetation. Possible values are none, low, high.
Dependent variable (also known as responding variable) is the amount of erosion. This can be measured by the loss of elevation on a pile of soil or by the amount of sand and soil that is washed away.
Constants are the speed of rain, the size of rain drops, the amount of rain, the type of soil, the initial condition (dryness) of soil.
Controlled variables are wind, weather temperature and other environmental factors that may affect the rate of erosion during our experiment.
Other variables such as ice and wind can also affect the rate of erosion but we will not study them in this project.
Hypothesis:
Based on your gathered information, make an educated guess about what types of things affect the system you are working with. Identifying variables is necessary before you can make a hypothesis. Following are two sample hypotheses for the two questions suggested above.
Sample Hypothesis for question number 1:
My hypothesis is that rain will cause erosion and the amount of erosion increases by any increase on the amount of rain.
Sample Hypothesis for question number 2:
My hypothesis is that plants and vegetation can prevent or decrease the rate of erosion. As the amount of plants increases, the rate of erosion will decrease.
You may think about other factors or methods of preventing erosion and write a different hypothesis.
Experiment Design:
Design an experiment to test each hypothesis. Make a step-by-step list of what you will do to answer each question. This list is called an experimental procedure. For an experiment to give answers you can trust, it must have a “control.” A control is an additional experimental trial or run. It is a separate experiment, done exactly like the others. The only difference is that no experimental variables are changed. A control is a neutral “reference point” for comparison that allows you to see what changing a variable does by comparing it to not changing anything. Dependable controls are sometimes very hard to develop. They can be the hardest part of a project. Without a control you cannot be sure that changing the variable causes your observations. A series of experiments that includes a control is called a “controlled experiment.”
Following are some sample experiments. Use them as an idea to design your own experiment.
Experiment 1:
Erosion demonstration
Introduction:
In this experiment we want to demonstrate the erosion caused by rain.
Procedure:
Take some soil, make a little mountain at least 20 cm high, with steep walls and a flat top. With a hose, water it down to simulate a rain, avoiding direct jets. You will see the borders slide down and the heap of mound of soil progressively take the typical profile of a true mountain. Observe and describe what happens during this artificial rain.
Build another mountain with stones, clay, sand and ground in different positions. Observe the different behavior of the materials towards the artificial rain.
If you want to test the erosion caused by wind, you can repeat this experiment, but instead of watering it, blow on it using an electric fan. Initially air current will dry up the soil and then it starts to move the small soil particles away. Note that wind speed some times is much higher than what an electric fan can produce. Also high winds carry sand that are abrasive and increase the erosion.
Experiment 2:
Effect of grass and vegetation on erosion
Introduction:
In this experiment we investigate the effect of grass on reduction of erosion.
Material:
4 pans that are alike, soil, water, sprinkling can, grass seed or a piece of sod
Procedure:
1. Poke holes along the side of one of the short ends of the pans. Fill one pan with soil.
2. Fill the second pan with soil or cut a piece of sod to fit in the pan. If you are using sod go to step 4.
3. Plant grass seed in the second pan. Place in a sunny location and water as needed to keep the soil moist, but not wet. When your grass is an inch high go on to step 4.
4. Place a block of wood under one end of the pans so they are on a slope with the holes on the low end. Place a pan or bucket underneath the holes.
5. Fill the sprinkling can and pour it on the high end of the first tray. Repeat the process for the second tray. Pour from the same height each time.
6. After each trial empty the contents of the runoff pan or bucket into a clear container and compare the results.
What was the result?
1. Which pan loses more soil?
2. How does water hurt the land?
3. How do plants help?
Experiment 3: Effect of furrows direction
- Fill two boxes about 3/4 of an inch full with soil.
- Set them on a table propping up one side so that there is an angle that makes a slope.
- Cut out a spout at the lower end of each box and place a jar below each spout.
- Now, using your finger make furrows across the soil in one box and up and down in the other.
- Then fill two watering cans or cups with water and sprinkle the water over each box at the same time and rate.
What do you see happening?
Do you see a difference in the content of each jar?
What does this project tell you about how contour farming works to help prevent soil erosion?
Experiment 4: Effect of Rain on The Rate of Erosion
- Fill one boxe about 3/4 of an inch full with soil.
- Set it on a table propping up one side so that there is an angle that makes a slope.
- Cut out a spout at the lower end of the box and place a jar below the spout.
- Then fill a small watering can or cup with water and sprinkle the water over the box.
Collect any run-off in the jar. Remove the jar. Label it Jar # 1.- Repeat the steps 4 and 5 with 4 more cans of water and collect the run-offs in new jars that you number them #2, #3, #4 and #5.
- Allow the content of each jar dry and then weigh them and record your data in your data table.
- Calculate the cumulating amount of displaced soil for each number of cups. For example if you add the amount of soil in jars #1, #2 and #3 you will have the cumulative sum of displaced soil by 3 cans of rain.
Make a graph:
To visually present your results make a bar graph with five vertical bar. Number the bars from 1 to 5 indicating the number of cans or cups of rain. The height of each bar will represent the cumulative amount of displaced soil by that amount of rain.
Your data table may look like this:
| Cups or cans of water | Erosion per cup or can | Cumulative Erosion or displaced soil |
| 1 | 17 | 17* |
| 2 | 28 | 45 |
| 3 | 32 | 77 |
| 4 | 31 | 108 |
| 5 | 37 | 145 |
* The data in the above table are not real. They are there to show you how the cumulative erosion is calculated.
Materials and Equipment:
The list of material depends on your experiment design. Following is just a sample.
List of material can be extracted from the experiment section. Following is a partial list of material used in the above experiments.
- Sprinkling cans
- two shallow pans
- a deeper pan
- soil
- soil with grass growing in it
- water in a container
- Electric Fan
Results of Experiment (Observation):
Experiments are often done in series. A series of experiments can be done by changing one variable a different amount each time. A series of experiments is made up of separate experimental “runs.” During each run you make a measurement of how much the variable affected the system under study. For each run, a different amount of change in the variable is used. This produces a different amount of response in the system. You measure this response, or record data, in a table for this purpose. This is considered “raw data” since it has not been processed or interpreted yet. When raw data gets processed mathematically, for example, it becomes results.
Calculations:
No calculation is required for this project, however you can calculate the rate of erosion. To calculate the rate of erosion do the following:
- Weight the soil that you are using before starting your experiment. (Dry or almost dry weight.)
- Weight the soil remained in the box after your experiment. (Dry it and then weight it).
- The weight loss is the amount of soil lost by erosion.
- Divide the weight loss by the original weight of soil before experiment and the result is the rate of erosion for certain amount of rain (water) that you used.
Summary of Results:
Summarize what happened. This can be in the form of a table of processed numerical data, or graphs. It could also be a written statement of what occurred during experiments.
It is from calculations using recorded data that tables and graphs are made. Studying tables and graphs, we can see trends that tell us how different variables cause our observations. Based on these trends, we can draw conclusions about the system under study. These conclusions help us confirm or deny our original hypothesis. Often, mathematical equations can be made from graphs. These equations allow us to predict how a change will affect the system without the need to do additional experiments. Advanced levels of experimental science rely heavily on graphical and mathematical analysis of data. At this level, science becomes even more interesting and powerful.
Conclusion:
Using the trends in your experimental data and your experimental observations, try to answer your original questions. Is your hypothesis correct? Now is the time to pull together what happened, and assess the experiments you did.
Related Questions & Answers:
What you have learned may allow you to answer other questions. Many questions are related. Several new questions may have occurred to you while doing experiments. You may now be able to understand or verify things that you discovered when gathering information for the project. Questions lead to more questions, which lead to additional hypothesis that need to be tested.
Possible Errors:
If you did not observe anything different than what happened with your control, the variable you changed may not affect the system you are investigating. If you did not observe a consistent, reproducible trend in your series of experimental runs there may be experimental errors affecting your results. The first thing to check is how you are making your measurements. Is the measurement method questionable or unreliable? Maybe you are reading a scale incorrectly, or maybe the measuring instrument is working erratically.
If you determine that experimental errors are influencing your results, carefully rethink the design of your experiments. Review each step of the procedure to find sources of potential errors. If possible, have a scientist review the procedure with you. Sometimes the designer of an experiment can miss the obvious.
