A GIS analysis of soil erosion potential on the Guilford College campus Abigail D. Blodgett and Angela M. Moore. Environmental Studies, Guilford College North Carolina Academy of Sciences March 19, 2005 Introduction Erosion Observed on the Guilford College Campus Soil erosion is a serious environmental problem. It can cause degraded soil quality and decrease the productivity of the land. Also, excessive erosion can increase sediment pollution in streams and waterways. This can decrease water quality, make it a less suitable habitat for species living in the water, and increase the cost to maintain waterways. The purpose of this study is to determine if some areas on the Guilford College campus are more susceptible to erosion than other areas. Based on the characteristics of the land, Where There is Visible Erosion on Campus Amount of Mitigation at Each Site there may be more erosion in some areas than in others. Erosion will already be accelerated in some areas on campus due to current heavy construction, particularly around the Milner parking with the construction of 5 new dormitories and a community center. The Revised Universal Soil Loss Equation is used in this study to estimate the annual soil loss in tons per acre. There are 46 spots on the main part of campus where erosion is occurring. Signs of erosion that were looked for include a lack of The majority of erosion vegetation, an unnatural buildup of sediments, points on campus, 28 out of the Procedure and gullies created by runoff during storms. 46, are not being mitigated at all. The majority of these points are located on There are 16 points that are being (to stream) To evaluate the properties of soils found on Guilford College’s campus, a base map of the college was created using GIS Arc Map, version 9.0. Maps for water, streams, colleges, topography, the Coronaco-Urban land complex (CuB). This slightly mitigated. This means and buildings were obtained from the city of Greensboro, North Carolina. A map of soils in Guilford County was obtained from the National Cooperative Soil Survey. soil type is on the most highly elevated part of that there is a little hay thrown campus, and the rest of campus surrounding this down on the area or some pebbles. To evaluate the potential for erosion based on the properties of the soils on campus, a map was created using the National Cooperative Soil Survey data. area down-cuts towards the stream and the lake. There are only 2 points that are This means that the sediments lost from the being fully mitigated. This means The next step was to estimate the amount of soil loss on campus. The Revised Universal Soil Loss Equation (RUSLE) was used to determine if certain areas of campus are more susceptible majority of the points of erosion on campus are that there is a substantial amount to erosion than others. The K, R, C, and P factors were found through outside resources. The C factor values were added as a new column in the attribute table of the land use layer, the K factor polluting the stream and the lake. A small amount of pebbles on the area. Also, the 3 values were added to the attribute table of the soils layer, and then the layers were both converted to raster to set up for the RUSLE calculation. The LS factor was determined manually. Maps of points are also located on the Coronaca clay major areas of erosion near the were created to show the K, C, and LS factors since they differ throughout the campus. The LS factor was determined using a raster data set with the raster calculator found in the Spatial loam (CrC) soil type where the apartments are, lake depicted by the RUSLE Analyst tools. First, the slope of the area in degrees raster data was added in to the base map. Then, that data was used to find flow accumulation, and the flow accumulation was then used to and the Madison clay loam (McD2) soil type findings as well as the findings find the LS values. Finally, the RUSLE equation was solved by multiplying the 5 coefficients together in the raster calculator. around the lake. The only difference between a from the field observations are Coronaca soil and a Madison soil that affects barely being mitigated. The last was to determine how much and where soil erosion was actually occurring on campus. To do this, I used a Magellan Meridian Gold GPS unit to mark the points of erosion on erosion is that a Madison soil is on a somewhat According to this data, campus. These waypoints were then loaded into the base map as a new layer in order to evaluate their location in relation to the type of soil at each point. I then added additional columns into steeper slope (National Cooperative soil Survey erosion is not being addressed as the attributes table for the waypoints to show amount of mitigation at each site and the causes of erosion. Three maps were created from this data. 1977). much as it should by the grounds There is a major correlation between the staff. Since the soil lost is being outcome of the RUSLE equation and the erosion transported into the stream, the Types of Soils on Campus that is currently visible on campus. The 3 most lake, and ultimately most of the Greensboro, NC prominent lines of erosion on campus are on the water bodies in Guilford County, controlling erosion should be edge of the athletic field, just as predicted by the RUSLE equation (see Annual Soil Loss on more of a concern to the college. The meadows Campus Measured in Tons per Acre). These 3 are mostly major problem areas are contributing greatly MhC2. This towards excessive sediment pollution in the lake. soil has a low potential for urban uses Greensboro because of its slope, Causes of Erosion permeability and high mica Runoff creates Recommendations and Conclusions content erosion when there (National Lack of vegetation is a period of Modeling general erosion trends with GIS is relatively straight-forward and can Cooperative can be humanly rainfall. When it be conducted with publicly available spatial data. Soil Survey induced, a result of rains, the storm 1977). over grazing or drain here empties Using GIS to implement the RUSLE equation for general soil erosion foraging, or a Potential for Erosion natural occurrence. runoff, causing erosion. effectively predicted some specific areas of significant erosion on campus, that matched well with field observations. Based on this study, this methodology appears to provide a good screening tool Heavy pedestrian The majority of the soils on campus are classified as being to identify locations with likely soil erosion problems. traffic removes moderately eroded, so land use restrictions should be The main part vegetation so there considered. Methods to control erosion should always be There are various practices that could be implement to control erosion more of campus is is an increased applied to construction sites on campus especially. If the effectively on campus: mostly CuB, amount of erosion potential for erosion of these soils was ignored, it would First of all, erosion mitigation should always occur when there is an urban land because soil is result in a significant amount of sediment pollution into the construction. Some methods to do this are temporary sediment basins, cover complex. exposed. stream and the lake on campus, and ultimately all of the areas that have a lack of vegetation with hay, cover sediment piles with water bodies in Guilford County. Erosion is also tarps, and vegetate the area as soon as possible. Construction caused by To control erosion where there is a lack of vegetation, the grounds staff There are 13 types of soils on Guilford College’s Campus. There are 3 should focus on keeping grass and/or basic plants all areas on campus. highly disturbs runoff in these sandy loams, 3 sandy clay loams, 4 clay loams, and 2 urban land The area on campus that is a source of erosion should be covered with soils by moving, pictures. These complexes. tarps if the school uses the leaves and the wood from these piles. If they uplifting, and piles of soil The soil boundaries were created by estimation with the use of aerial aren’t used, then the piles should be dispersed throughout the woods. piling the soils so were made by photos, and then verification on the ground by soil scientists (Soil Survey Steep slopes should be prevented and leveled out. that more erosion the grounds Division Staff 1993). occurs with runoff staff. and wind. In addition to these simple methods for erosion control, the points of erosion marked in this study should not be ignored after they are tended to by these A source means that controls. Since the campus is always changing, especially recently, it is crucial there is a pile of that these points are checked up on a least once a month to make sure that these Estimated Annual Soil Loss Using RUSLE sediments that will be eroded by rain or controls are working and still existent. wind. This source is Also, there should be a future studies to collect field observations of erosion a pile of leaves and occurring in the woods to compare to the outcome of the RUSLE equation as well The Revised Universal Annual Soil Loss Equation (RUSLE) a pile of lumber on as to measure sediment concentration in the streams and in the lake overtime to RUSLE is a general equation that provides the edge of the determine the effect of any mitigation efforts. the basis for most assessment of soil erosion. A= average annual soil loss in tons per acre woods. It calculates the expected annual potential K= soil-erodibility factor Overall, permanent erosion controls need to be implemented on campus in soil loss per acre based on rainfall pattern, A = K * R * C * LS * P R= rainfall erosion index addition to the temporary controls that generally already exist. Vegetating more soil composition, vegetative cover, slope and C= crop management or plant cover factor areas on campus would be the easiest permanent erosion control. Also, there conservation practices. It is empirical, or LS= slope geometry, based on steepness and length should existing steep slopes, especially near the lake, should be leveled out and based on observations, rather than P=conservation practice factors future ones should be prevented. theoretical. The Slope Geometry (LS Factor) The Annual Soil Loss on Campus Measured in The LS factor is determined Tons Per Acre The Plant Cover Factor (C Factor) by slope length and The other 2 coefficient not Acknowledgements The Soil Erodibility Factor (K Factor) steepness in relation to the picture are the rainfall The C factor reflects the type of potential for erosion. The erosion index (R factor) Special acknowledgements towards Richard Farris for helping to identify soil types The K factor values were land cover in relation to the LS factor of each 5 ft by 5 ft and the conservation for ground-truthing the county soil data and to Chris Freeman with the Greensboro obtained from the Guilford amount of rainfall interception. cell in this raster data set is practice factors (the P GIS office for providing the raster data to compute the LS factor. County Soil Survey. The part The woods on campus have the determined not only by the lowest C factor at 0.003. This is slope within each cell, but factor). The R factor for of campus that is the most because there is a canopy from the cell around it at a Greensboro is 225 developed has a soil erodibility factor 0f 0.24. The preventing a large percentage of higher elevation. The (Randolph 2004). The P factor is 1 because there are References majority of the woods and the rainfall from contributing to equation used to determine erosion. The open fields have a the LS factor reflects no conservation practices area around the lake has a soil National Cooperative Soil Survey. 1977. Soil Survey of Guilford County, North slightly higher C factor, 0.004, variated topography. on campus. erodibility factor of 0.28. A Carolina. because there is less of a canopy. On campus, the areas with The areas on campus with small section of the woods The developed part of campus the highest LS values are the highest annual soil loss and part of the meadows has a Randolph, John. 2004. Environmental Land Use Planning and Management. Island was classified as suburban with a directly west and along the is on the edge of the soil erodibility factor is 0.32. Press, Washington D. C. C factor value of 0.01 because stream in the woods and athletic fields. This is This means that the soils there is less vegetation due to the surrounding the lake. This because of the high C covering the developed part Soil Survey Division Staff. 1993. Soil Survey Manual. Soil Conservation Service. presence of impermeable mean that the sediments factor value that the athletic of campus are less susceptible U.S. Department of Agriculture Handbook 18. surfaces and human intervention. from the main part of fields have. This result is to erosion than the rest of The athletic fields on campus campus flow downhill especially problematic with campus that is less disturbed. Yang, D. S. Kanae, T. Oki, T. Koikel, & T. Musiake. 2003. Global potential soil were classified as golf courses towards the stream in the the field near the lake This is because the soils on erosion with reference to land use and climate change. Hydrological Processes, 17 with the highest C factor value of woods and the lake. This is because there is a steep the developed part of campus (14): 2913-2928. have a higher percentage of ).2 because there isn’t any plants problematic because this slope with sediment besides grass and is highly means that there is a certain buildup on the edge that is clay, which highly resistant to altered by frequent mowing and degree of sediment pollution closest to the lake (see detachment from runoff fertilizer. (Yang 2003). occurring in the stream and Causes of Erosion (National Cooperative Soil the lake. pictures). Survey 1977).