HR: 0800h
AN: H51C-1149    [Abstracts]
TI: Effects of a Wildfire and Salvage Logging on Hillslope Erosion: Star Fire, Placer County, California
AU: * Chase, E H
EM: echase76@lamar.colostate.edu
AF: Department of Forest, Rangeland, and Watershed Stewardship, Colorado State University, Fort Collins, CO 80523 United States
AU: MacDonald, L H
EM: leemac@cnr.colostate.edu
AF: Department of Forest, Rangeland, and Watershed Stewardship, Colorado State University, Fort Collins, CO 80523 United States
AB: Post-fire erosion rates have been measured in many areas, but there are few published data on how salvage logging affects post-fire erosion. The primary objective of this study was to compare sediment production rates from sites burned at high severity and subjected to helicopter, cable, or tractor logging, respectively. Sediment production was measured with sediment fences on 32 logged sites and five unburned, unlogged sites over two wet seasons in the central Sierra Nevada of California. The independent variables measured on each site included slope, aspect, contributing area, percent bare soil, percent rocky outcrop, percent ground disturbance, soil texture, and soil water repellency. The first wet season had near-normal precipitation and a calculated erosivity of 556 MJ mm ha$^{-1}$ h$^{-1}$. Mean sediment production rates were 2.5 Mg ha$^{-1}$ from the burned sites and zero from the unburned sites. The second wet season had only 13 MJ mm ha$^{-1}$ h$^{-1}$ of erosivity because most of the precipitation fell as snow, and the mean sediment production rate from the burned sites declined to 0.11 Mg ha$^{-1}$. Mean sediment production rates did not significantly differ by logging type due to the high variability between sites in the first wet season and the very low sediment production rates in the second wet season. Slope, percent ground disturbance, and percent bare soil were significantly correlated with increasing sediment production per unit area. Percent ground disturbance was significantly higher for the cable- and tractor-logged sites than for the sites logged by helicopter (p$<$0.001), but there were no significant differences in percent bare soil by logging type. Sites logged by helicopter tended to have lower sediment production rates than cable-logged sites (p=0.086). The results indicate that logging methods that increase ground disturbance and bare soil will generate more sediment, but statistically significant differences in sediment production may be difficult to detect given the natural variability between sites and the variability in harvest practices.
DE: 1803 Anthropogenic effects
DE: 1815 Erosion and sedimentation
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting