Experiences for Undergraduates
Name Lee MacDopnald
Department Earth Resources
Work Phone 970-491-6109
Project Title Effects of Burned-area Rehabilitation Treatments on Runoff and Erosion
Project Abstract Numerous studies have documented order-of-magnitude increases in runoff and erosion following wildfires in forested areas. Land managers usually apply a series of treatments to try and reduce the magnitude of these increeases. Typical treatments include the application of grass seed (usually by helicopter), the felling of burned trees across the slope to act as dams for water and sediment ("contour felling"), and the application of mulch in the more accessible areas. While the use of these treatments are widespread, there has been very little rigorous study of the effectiveness of these techniques (Robichaud et al., 2000).
The Bobcat Fire burned over 40 km2 of forested lands west of Fort Collins in June 2000. Due in part to pressures from downstream water users, the U.S. Forest Service and Natural Resources Conservation Service applied each of these treatments over portions of the burned area. The purpose of our study is to evaluate the effectiveness of these treatments. Approximately 40 sediment fences were installed in the late summer and fall of 2000 to measure sediment production rates from each of these treatments. Sediment from these fences is being collected, weighed, and sampled for water content and particle size. We also have been tracking changes in percent cover over time to evaluate whether seeding increases plant density relative to natural regeneration processes. We also have been measuring the infiltration rates in the trenches immediately upslope of the contour-felled logs to determine if this treatment enhances infiltration. Finally, we have been evaluating the percent of contour-felled logs that are effective and the sediment storage capacity of each log. Preliminary results indicate that mulching substantially reduces erosion rates, but the other treatments have no statistically-significant effect, in part to the high spatial variability. We have not observed a decrease in sediment production despite an increase in vegetative cover in all treatments.
The REU student would be involved in making the continuing field measurements to determine the effectiveness of each treatment over time as well as the key controlling factors. In summer 2002 we will be continuing to measure sediment production rates, infiltration rates, changes in percent cover, and the amount and intensity of rainfall using 10 recording gages. The student could select one component of the project as their focus, and this could be the spatial and temporal variability in rainfall, differences in infiltration rates as a result of the different treatments, sediment storage capacity of the contour-felled logs, or changes in percent cover. The student would need to be capable of physically-demanding field work, but the proximity of the site to Fort Collins means that they would not have to be away from campus overnight.