Our group collectively decided to experiment with something having to do with erosion, but we were not quit sure what we were going to do with it. After putting all of our ideas together we came up with our final idea, which is to test the erosion of the bluffs and what affects the erosion, such as weather. During our research of the erosion of the bluffs, we expect to find erosion to be erratic over the course of our experimentation yet calculable due to slope and precipitation variables. We do not anticipate that erosion to be uniform from one point to another. We will be testing the erosion weekly to get as much data as possible, we want to take special care in checking after it rains because we feel that weather, rain in particular, is going to have a large impact on the erosion of the bluffs. Because it is hard for us to predict how much the bluffs will erode we have many questions that can be answered only through our data analysis. We decided on our questions by questioning what was going to happen over the course of time that we will be performing the experiment. We plan to test our hypothesis and answer the questions that we have formed ourselves. For example, we plan on finding out where the heaviest eroded areas are or what kind of affect rain has on the erosion? All of the questions came from our curiosity of the experiment.
We plan to take measurements every week from the twenty stakes that we have plotted in a grid form in a specific area of the bluffs. Our area is 6 by 9 meters and each stake is going to be about 1 meter apart from each other. The change in weather will affect the erosion, some weather conditions more than others. We were first interested in many things we learned on our nature walk initially some people in the group were interested in the bluffs and how they were formed. Some of the group was interested in erosion but didn't know what to do with it to make it into an experiment. After talking to some people about the options we had, we came to our final conclusion. All four of us developed an interest in this experiment as we talked more about it and discovered many things that we didn't know but would like to learn about.
II. Relevancy of Our Research Question:
We gathered around ten sources of material relating to our lab topic, soil erosion. Our group is specifically concerned with rainwater and its erosional affect on soil. Recently, our group decided to narrow down our previous ten research resources to five of our best. We went with the sources that related the closest to our specifics in our project. We looked at a few books which outlined in detail what erosion was, and its relation to soil erosion. A very informative source, that our group used, was that by D. Zachar. In this work, we got most of our beneficial information for the chapter that was directly related to water erosion. This work helped us in the understanding of exactly how the rain droplets moves dirt on the ground to produce various forms of water erosion. "When rain droplets fall on the ground, it disperses the soil outward, thereby creating an indentation and removal of soil" ( Zachar 34).
Another helpful literary resource was a book titled Soil Erosion by Sandra Batie. In this informative resource, she explains to the reader about various types of erosion, and was very helpful when we were identifying our lab site to the type of erosion that occurs there. Specifically, the book depicted various different forms of water induced soil erosion. The pictures helped us to understand the similarities between one type and the actual effects of erosion we found on site.
We received very good information from various online sources. From an Iowa statistics lab we obtained an explanation and pictures of various forms of erosion, relating to the previously gathered information. [ The type of erosion that most closely represents our site is that of rill erosion. Rill is where water falls and creates grooves in the soil. Sometimes the grooves get really deep and then form into more of a gully result. "Rill erosion is the removal of soil through the cutting of many small, but conspicuous, channels where runoff concentrates" (www.statlab.iastate.edu/ssmnew/chap3t.html 1). It was very informative and closely related to the actual site we were basing our lab on. This also gave the group an understanding of the type of further erosion that we will likely experience as the project progresses. In another website, we learned that water erosion is the main type of erosion that occurs when we deal with soil. It is a dominating 56%! We also learned that when we are dealing with water induced soil erosion, the most occurs on hilly, barren, no vegetation landscapes. This site works well for our purposes because it relates well to our test site at the bluffs.
The literature that we covered was helpful. In fact, in one of the best resources we found, www.gcrio.org/geo/soil.html, we found a definition and actual ways to go about testing your own erosion experiment. It related extremely close to the method we came up with before.
Standard techniques, using erosion pins to detect soil creep or sheet and rill erosion, painted rock lines and other sediment tracers to determine soil movement, cliff recession and headcut markers, Young pits, repeated profile and slope measurements, and repeat photography using reference points. Repeat measurements of water and sediment collected in permanently installed hillslope troughs provide seasonal, annual and longer-term estimates of erosion and storage along hillslope profiles. Rates of soil erosion can be estimated using erosion-prediction equations developed during the last four decades. Among these algorithms are the Universal Soil Loss Equation (and its recent update the Revised Universal Soil Loss Equation), the Water Erosion Prediction Project model, and the European Soil Erosion Model (www.gcrio.org/geo/soil.html 1).
This also gives our group a very new and definite approach to study the erosion. The equations do give a more professional perspective to this project.
This research relates to the overall project and to overall humanity because it gives laymen an introduction or awareness to the effects of rainwater on a non-vegetative slope, can have. Such erosion is useful in understanding the conservation of forestry, natural shrubs and landscaping. It is interesting to take the time to see that on a given piece of land, what factors do indeed shape and change it. Even though, according to some of the research we found, a good erosion study should be measured over a period of a couple decades, our brief timed research of erosion on the bluffs is a somewhat good indicator of the erosion that may take place in a small period of time. It is an interesting subject to tackle just to see exactly what effects rainfall does indeed have on a barren slope.
III. Materials and Methods:
· Experimental Design.
A] A field area of 6.0 x 9.0m is established in the bluffs and stakes are evenly distributed 1.8 meters. The stakes are placed vertically into the ground and the ground level is marked on the stakes. Weekly, the level of soil removal in relation to the previous mark on the stake is noted and the measurable distance is recorded. The control for the experiment is a topographical map of the bluffs via a global survey by the United States government. The design is set up so as to accurately and efficiently gauge the erosion of the bluffs. We aren't measuring the whole bluffs simply because much of the bluffs are too steep to be able to measure and safely traverse.
B] At this point the lab is statistically sound. However there are some precautions to be taken to ensure accurate results. It is possible for the stakes to wash away should there be too much erosion. Also some erosion may actually accumulate around a stick, which might cause our results to be off. However we don't anticipate such things as being likely. To be unbiased we will use purely quantitative data. The class we assume to be intelligent enough to measure in millimeters.
C] Important materials are primarily graduated dowel rods. We will then be able to simply look at and gauge the erosion. Also the government topographical map will be utilized as a control.
D] After measuring we will make tables and construct graphs with our data. The class will go with us to the bluffs and after we've demonstrated our data collection techniques, the class will also collect data. The class will calculate our p-values for just that week. We will have p-values for every week. In addition to weekly t-test we will use data from different weeks and compare them against each other by utilizing t-test and calculating p-values.
E] Our data sheet will include relevant graphs, calculations and collected data that effectively illustrate the erosional effects on the bluffs. Our hope is that graphs and tables that indicate the changes in soil displacement after rainfall will support our hypothesis.
F] Weekly trips to the bluffs starting October 2nd and concluding when data needs to be analyzed for our final lab and will be no longer calculated or collected.
G] The student participation will include the following steps:
1. Walk to the bluffs and observe the area and the stakes.
2. We as a group will climb a little ways down the bluffs and observe each stake where the original black mark was recorded and then every point after that as the class watches and learns.
3. Walk back to the classroom and work on the computers to record the p-value and T-test for each recording.
A] Our final results indicate variations in erosion levels due to the slope of the bluff or the distance from the topmost area of the bluffs. Our data sheets [included separately] clearly illustrate the differences in erosion levels based on the pitch of the bluff upon which the stake was inserted. Areas at the bottom received greater erosion party based on rainwater run-off from the top and also upon the greater pitch of the base. The stakes at the top were on mostly level land and therefore most erosion was caused by rainwater penetration and less on run-off. The erosion was decidedly less on the top then on the bottom of the bluffs.
B] We are using mean, standard deviation and t-tests to analyze our results. We used mean to determine the erosion from week to week, and standard deviation to determine the change in erosion from week to week. The t-tests will tell us whether our data is significant and whether they came from two different sets of data. Our means and standard deviations can be scene in the charts on the attached sheet. Our results show that there is a 10-fold difference between the upper row of the bluff and the lower rows. This indicates that that the slope of the bluffs contributes to the effects of rainwater run-off on the lower stakes in the bluffs. We concluded this by calculating the p-values from each stake on the top row with the corresponding stake on the bottom row. Our p-values were as follows:
2A. and 6A. t = -.5644
2B. and 6B. t = -.80736
2C. and 6C. t = -3.662
2D. and 6D. t = .539
2E. and 6E. t = -5.844
2F. and 6F. t = -4.451
C] Our results show that the p-values are below .05 and are therefore significant in nature. It indicates that the two sets of data were from different test sites and were significantly different. This is in alignment with our hypothesis that the stakes at the bottom received a greater amount of erosion than the stakes at the top probably because of rainwater run-off. Our final results including mean, standard deviation, and p-values and a comparative chart are attached.
Discussion and Conclusion;
A] Our data, and observations of erosion patterns of the bluffs, leads us to interpret our results as revealing erosion as primarily a function of rainfall. The erosion patterns around the test site, for example in places where small pebbles or roots blocked the intended impact of the rain drops less erosion and striping of the bluffs occurred. This observation along with the fact that some stakes recorded negative erosion caused us to conclude that the primary erosion factor was the actual impact of the rain. The stake itself blocked the intended impact of the rain and therefor the area the stake was measuring was not receiving the actual amount of rain as the rest of the bluffs, also the areas that did receive rain just outside of the area of the stakes would splatter when on impact. Veins in the areas that were blocked by roots and stakes and pebbles indicated that the erosion was mostly an effect of direct rain penetration and less on rain run-off although it was a factor in erosion as well because it explains the difference in erosion from the top and bottom rows.
B] Other groups in our class alone have experiments related to ours. The rainfall experiment that measured the amount of rain in western campus is related to ours because our experiment was hinged on the amount of rain that fell in a given time. More rain according to our experiment hypothesis will mean more erosion so these two experiments are related to each other. Obviously the other erosion group will have data in correlation with ours and we can use their soil test to hypothesis future erosion in our site since theirs dealt with soil composition and erosion effects.
C] We have questions about the relevancy of our data because our experiment was set up in a way that didn't provide a clear cut set of data. Is it possible to set up a stake measuring system in a way that can be accurately measured without outside interferences that affects data. To further investigate our subject we would need to collect sonar images to measure a total picture of every point to get a totally accurate and reliable image of the erosion of the bluffs.
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