Phosphate and Upland Erosion
Sediment is a major contaminant in Seven Mile Creek. The sediment itself clouds the water and silts over fish spawning sites. Sediment also serves as a means of transportation for phopsphorus that is attached to soil particles. The major source of eroded sediment in the SMC Watershed is bank erosion, which we have determined to be a result of an imbalance in stream mechanics. The second largest contributor is upland erosion, in which soils are washed off cultivated fields into the creek.
RUSLE & CREAMS
RUSLE (Revised Universal Soil Loss Equation) and CREAMS (Chemicals, Runoff, and Erosion from Agricultural Management Systems) are two methods used to estimate soil erosion rates. RUSLE is characterized as a rainfall soil erosion prediction model, while CREAMS includes a phosphorus enrichment algorithm. In both models sources of input considered for anaylsis include the riparian corridor, open tile intake basins, the upland region, and bank erosion. CREAMS incorporates the input of phosphorus due to non-complying septics, as well. Soil erosion rates obtained from these methods are expressed in tons of soil loss per acre per year. RUSLE is a computer program developed by the USDA and available to the public. You can learn more about the development of the method and download the program at the National Sedimentation Laboratory website.
