Available at: http://digitalcommons.calpoly.edu/theses/259
Date of Award
MS in Agriculture - Soil Science
Brent G. Hallock
Erosion is a natural process that occurs when soil particles are detached from one site and transported to another by water or wind, and can occur naturally or be accelerated by humans. Sediment can cause direct mortality or reduce growth of fish and other aquatic resources, particularly larval fish and eggs. Three treatments consisting of compost and jute netting, crimped straw with native seeds, and jute netting and vegetation filter strip were used to evaluate loss of runoff water and sediment on steep slopes. Erosion plots were built on slopes of 27 percent and filled with soil. The treatments were applied in triplicate and irrigated at 14-day intervals. Each erosion plot was irrigated with approximately 79 gallons of water for 10 hours and runoff was collected in pre-weighed containers during each period. After each collection, runoff from each plot was measured and recorded by subtracting the weight of each empty container from the combined weight of water and sediment. Turbidity, pH, and electrical conductivity were measured, and the separate weights of runoff and dry sediment were determined. The combination of jute netting over a layer of commercially available compost was over 99 percent effective at reducing runoff and sediment loss as compared to the untreated control erosion plots. Jute netting combined with a vegetative filter strip of creeping wild rye was over 94 percent and 99 percent effective at reducing runoff and sediment loss when compared to the untreated control erosion plots, respectively. Runoff and sediment loss from plots treated with crimped straw and native seeds was significantly greater than that of the other treatments, yet this treatment was over still 80 percent effective at reducing runoff and nearly 97 percent effective at reducing sediment loss. The cost-effectiveness of each treatment was evaluated based on the cost of the total treatment compared to the amount of water each treatment prevented from leaving the site, using the control plots as a baseline. The combination of jute and vegetation filter strip cost approximately $0.47 per liter of water prevented from leaving the site and was almost as effective at reducing runoff and sediment loss as was jute combined with compost, which cost $1.04 per liter. While each of the three treatments significantly reduced runoff and sediment loss when compared to the barren control plots, the jute and filter strip treatment was the most cost-effective of the three treatments. All treatments were effective at decreasing runoff and sediment loss when compared to the control, though no significant difference in runoff was observed between the control and any of the treatments after ten weeks. Thus, erosion control BMPs should be implemented well before the first storm causing runoff in order to be most effective.