HR: 0830h
AN: H51D-1107    [PDF]
TI: Effectiveness of Emergency Rehabilitation Treatments in Reducing Post-fire Erosion, Colorado Front Range
AU: * Rough, D T
EM: drough@lamar.colostate.edu
AU: MacDonald, L H
EM: leemac@cnr.colostate.edu
AB: Daniella T.M. Rough Department of Forest, Rangeland, and Watershed Stewardship, Colorado State University, Fort Collins, CO Lee H. MacDonald Department of Forest, Rangeland, and Watershed Stewardship, Colorado State University, Fort Collins, CO Burned area emergency rehabilitation (BAER) treatments are often applied to reduce post-fire flooding and erosion, but few studies have quantified their efficacy. The effectiveness of different BAER treatments in reducing post-fire erosion rates is being studied for three different wildfires in the Colorado Front Range. The treatments being monitored include seeding, contour felling, mulching, scarification with seeding, and a polyacrylamide (PAM). Sediment production rates are being measured at the hillslope scale using sediment fences installed immediately after the June 2000 Bobcat fire and the 2002 Hayman and Schoonover fires. Neither aerial- nor ground-based seeding significantly reduced erosion rates in the first three years after the Bobcat fire. In contrast, 4.5 t ha$^{-1}$ of straw mulch consistently reduced sediment yields by more than 90%. Contour felling initially reduced erosion rates for small and moderate storms, but was less effective following the largest storms, presumably due to overwhelmed sediment storage capacity. A paired\-swale design is being used for the 2002 Hayman and Schoonover fires, as this provides a more sensitive evaluation of BAER treatment effectiveness. The ground-based application of straw mulch and the aerial application of hydromulch each reduced sediment yields by more than 95% in both 2002 and 2003. However, the ground-based application of hydromulch in fall 2002 did not significantly reduce sediment yields in 2003. In 2002 the application of 11 kg ha$^{-1}$ of PAM in an ammonium sulfate solution reduced sediment yields by 66%. In 2003 neither these sites nor three newly treated sites showed a significant reduction in sediment yields. A dry application of 5.6 kg ha$^{-1}$ PAM had no detectable effect on sediment yields, nor did scarification and seeding in 2002 or 2003. These data suggest that treatment effectiveness varies with time since application, storm intensity, and amount of ground cover. Studies on these and other fires indicate that percent ground cover is the primary control on post-fire erosion rates because this reduces rainsplash, sheetwash, and rill erosion. Mulching has been the most effective BAER treatment because this immediately provides ground cover. Treatments that do not immediately increase ground cover (e.g., seeding, contour felling, and PAM) have shown more limited effectiveness in reducing post-fire erosion rates.
DE: 1815 Erosion and sedimentation
SC: Hydrology [H]
MN: 2003 Fall Meeting