THE “NOT SO FLAT SURFACE” PROJECT
We had two working hypotheses, one hypothesis going into this project was that the uneven parking lot is channeling water towards eroded areas. Ideally rain water should flow evenly down slope. The other hypothesis was that the angle and the material were causing the erosion.
Each group tested their hypothesis through measurements and modeling. In the uneven surface hypothesis, we plotted the southern (lower) half of the parking lot into 10ft x 10ft squares, roughly a 30ft x 240ft area. We then used a Brunton compass to measure the slope in each of the 10 ft plots. We then brought our findings together to be recorded on a graph that was made of the parking lot. The angle hypothesis group focused our project on the dirt portion of the parking lot since that seemed to be getting most of the runoff. To start out we measured the angles every 12 feet across the entire span of dirt in front of the parking lot. After taking all the measurements we found that 10 degrees and 20 degrees were the most common slopes. To simulate a rainfall and the effect it had on the dirt and how it eroded we created 4 models to simulate rainfall. Two models were made at 10 degrees and two were made at 20 degrees using dirt from the eroded area as the base. To test the theory that it was the material that was the issue we added rock over the dirt to one model for each angle. When all of the models were complete we used one gallon of water poured through a watering can on all of the models to see what results would occur.
In each group a portion of the findings contributed to a better understanding of the erosional process of this parking lot. We were able to determine that because of the combination of loose gravel and traffic and other factors causing erosion to the lot's surface, the slope is not running evenly southward. The flow of rain runoff is channeled into the eroded areas of the sides of the basin. In addition, the model where the dirt covered in a layer of rock demonstrated a slope more resistant to erosion and had significantly less wash out. We determined that the angle was not as big of an issue as was the soil composition.