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"Pfeffer Park is Falling Down: How Erosional Patterns and Effects Modify the Cliff"
I. Introduction
For our group project, we decided to test the erosion patterns on the cliff above the bluff at Pfeffer Park. On our nature hike earlier in the semester, the teaching assistants mentioned that over the years, the cliff had slowly eroded away, thus leaving tree roots visible from the cliff's edge. We were intrigued by the erosive history of the cliff. After the hike, we sat down to brainstorm ideas for our student-generated lab. After much deliberation, we came to the conclusion that further research would predict the future conditions of the cliff at Pfeffer Park. We believe that our study will be useful in aiding the conservation of the park based on drastic erosional changes within recent years. Our goal for our project is to collect data weekly that illustrates the impact of wind and rain on the landscape of the cliff. Our hypothesis is that over the course of our experiment, our data will reflect patterns of deterioration due to the natural forces of rainfall and the resultant soil moisture on the cliff.
The cliff at Pfeffer Park is an example of the progressing stages of erosion. These stages include first, sheet erosion, the uniform removal of soil from the surface. Second is rill erosion which is considered the intermediate stage between sheet and gully erosion. In the rill erosion stage, channels are created by sediment runoff. Third is gully erosion, which produces deeply incised channels, as seen at the cliff in Peffer Park. We will be examining the type of soil to determine how it correlates with the amount of erosion. In examining the soil contents we will be comparing soil surveys taken from each of the ten stakes in the10 by 5 plotted areas near the edge of the cliff (Toy et. al, 2002). The other erosion factor we will be examining is precipitation runoff as the cliff has been subject to rill, sheet and gully erosion. Our main objective is to observe just how fast it erodes, and how the precipitation and soil type contribute to the rate of erosion.
For rainfall as an erosive agent, our goal is to understand the cause and effect of how the forces of precipitation must overcome the soil's particular bonding forces and how these bonding forces cause particle detachment, thus leading to erosion.
II. Relevance
In proceeding to find more information about erosion patterns due to rainfall and soil types we discovered many pieces of literature where others had delved into this topic. Researchers have developed the theory that the "landscape develops by the upslope encroachment, upon each slope element, of the one below it of lower gradient and greater degree of reduction" (Gerrad 1981). This idea might help us in understanding the reason why the bluff has so many layers, and why these layers have been formed. Other researchers have found that erosion rates vary with groundwater, climate relief, rock and soil type, and location of the stream system. Lanbein et. al. (1949), shows that the mean annual run-off decreases with increasing temperatures. Calculations have revealed the fact that erosion decreases exponentially with increased vegetation cover under the same conditions. This information will help our group to further understand why some areas are more prone to erosion, the areas with less vegetation (Daniels, 1992). Our research is going to yield very interesting results, as we test one researchers findings that, "rainfall impact is negligible when the flow depth is larger than three times the raindrop diameter" (Julien, 1995).
We hope to discover a general pattern of degradation in the cliff area, and apply that further to the park as a whole. By finding these new patterns, we can hopefully propose mechanisms and practices which can slow the destructive forces of erosion. Furthermore, we may find that in the course of our experiment, the soil of the site is either especially susceptible or resistant to erosive agents such as rainfall, and this knowledge can be used not only in methods to slow erosion in the park, but in broader environments, such as the Miami Valley.
III. Materials and Methods
A. Materials
10 Wooden Stakes
Plastic Bags
Measuring Tape
Markers
Shovels
Camera
Soil Moisture Meter
Munsell's Color Chart
B. Methods
We will begin our project by assigning a 10m x 5m area that will serve as our experimental context. We will then place our stakes at one meter intervals with the last stake being placed 2 meters from the edge of the cliff. After the stakes are placed, we will mark the ground level on each stake, so as to indicate where the ground level was at the beginning of the project, so that we can compare it to successive levels possibly altered by runoff.
Each week, we will visit the site twice, each time recording not only the distance of the final stake from the edge of the cliff, but also the ground level at each stake. These tests will ensure an accurate measurement of any erosion that has occurred. We will record the cumulative rainfall totals each time since the last data collection. To supplement these totals, we will collect soil moisture data to understand the precise impact of precipitation on the site. We will combine the data we collect from the soil moisture meter with the composition of the soil based on the Butler County Soil Survey.
Additionally, we will be taking soil samples at 5 of the 10 stakes, and placing them in plastic bags at the beginning of the project, and comparing that to soil samples to be taken at its conclusion. This data will provide information how susceptible the soil is to erosion as well as if there have been any changes in the soil due to erosive agents. We will compare the soil to MunsellŐs Color Chart in order to figure out the soil's composition.
We will also be taking pictures of the site once every week, to provide others with a visual representation of the changes over time. As much as we can control the actions and attitudes of the students, we are hoping that by demonstrating our design through an outline, pictures, and any needed individual explanation, the students will be able to perform the tasks that we require of them. We will then ask them to travel to the site and measure the changes in ground level and distance from the cliff, as we would do normally, however many times we are allotted.
Our project is as statistically sound as it can be, because without more time and resources, we cannot accurately study all of the forces which have an impact on the cliff area. We will be taking only a few statistical data tests because of the limited amount of time. We will tabulate weekly averages for the amount of precipitation. Also, we will compare the weekly means of precipitation and the soil moisture. Based on the data collected from the means, we plan to calculate the total mean precipitation and soil moisture over the span of the five week data collection. We will only be able to study rainfall, because it is the only force that will be likely to provide us with statistically significant data and meaningful results within the time frame. However, we do plan to graphically analyze our data, and extrapolate information that will indicate to us how possible future patterns of erosion. Our data will be unbiased within the framework of our project because we have established a superficial experimental context which will become a rather standard setting for empirical data collection.
Data Sheet
Date:
Time:
Data Collectors:
Initial Distance from GL to new GL:
Distance from edge to stake:
Total precipitation from last collection:
Level of soil moisture
(ppm):
GL= ground level
IV. Project Timeline
We will do our data collections Tuesdays and Fridays at 4:30 in the afternoon.
Week 1:
October 22nd - collect data at site
October 25th - collect data at site
(Student participation- soil sampling & digging)
Week 2:
October 29th - collect data at site
November 1st - collect data at site
Week 3:
November 5th - collect data at site
November 8th - collect data at site
Week 4:
November 12th - collect data at site
November 15th - collect data at site
Week 5:
November 18th - November 26th
Analyze data, type up results, write discussion, and finish lab write
up in general.
** Thanksgiving break**
Bibliography
Agassi, M., & Bradford, J. (1999, January 18). Methodologies for interrill soil erosion studies. Soil & Tillage Research, 277-287.
Chulsang, Y., Valdes, J. & North, G. (1998, August 15). Evaluation of the impact of rainfall on soil moisture variability. Advances in Water Resources, 375-384.
Daniels, R.B., and Hammer, R.D. (1992) Soil and Geomorphology (John Wiley and Sons, Inc.)
Fox, D., & Bryan, R. (2000, January). The relationship of soil loss by interrill erosion to slope gradient. Catena, 211-222.
Gerrard, A.J. (1981) Soil and Landforms (George Allen and Unwin)
Julien, P.Y. (1995) Erosion and Sedimentation (Cambridge University Press)
Lee, E., Hall J., & Meadowcroft I. (2001, October). Coastal cliff recession: the use of probabilistic prediction methods. Geomorphology, 253-269.
Nachtergaele, J., & Poesen, J. (2002, August). Medium-term evolution of a gully developed in loess-derived soil. Geomorphology, 223-239.
Newson, Malcolm (1994) Hydrology and the River Environment (Oxford University Press)
Ollesch, G., & Vacca, A. (2002, August). Influence of time on measurement results of erosion plot studies. Soil & Tillage Research, 23-39.
Pielou, E.C. (1998) Fresh Water (University of Chicago Press)
Sidorchuk, A. (1999, October). Dynamic and static models of gully erosion. Catena, 401-414.
Toy, T.J., Foster, G.R., Renard, K.G. (2002) Soil Erosion: Processes, Prediction, Measurement, and Control (John Wiley and Sons, Inc.)
United States. Department of Agriculture. Soil Conservation Service. Butler County Soil Survey Lerch, Norbert K. Issued 1980
Zachar, P. (1982) Soil Erosion: Developments in Soil Science 10 (VEDA: Publishing House of the Slovak Academy of Science)
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