HR: 09:45h
AN: H51M-08    [Abstracts]
TI: Watershed-Scale Post-Fire Treatment Effects on Runoff and Erosion After the Hayman Fire, Colorado
AU: * Wagenbrenner, J W
EM: jwagenbrenner@fs.fed.us
AF: USDA Forest Service, Rocky Mountain Research Station, 1221 S. Main St, Moscow, ID 83843, United States
AU: Robichaud, P R
EM: probichaud@fs.fed.us
AF: USDA Forest Service, Rocky Mountain Research Station, 1221 S. Main St, Moscow, ID 83843, United States
AU: Brown, R E
EM: bbrown02@fs.fed.us
AF: USDA Forest Service, Rocky Mountain Research Station, 1221 S. Main St, Moscow, ID 83843, United States
AB: Wildfires can cause large increases in runoff and erosion. Although post-fire treatments are used to mitigate these effects, their effectiveness is not well documented. A study was initiated after the 2002 Hayman Fire to determine natural post-fire recovery rates, measure the effectiveness of contour-felled logs, straw mulch, and hydromulch, and determine effects of post-fire salvage logging. Sediment traps and weirs were installed in six severely burned small watersheds (3-5 ha) at 2 sites in the Hayman Fire. The above treatments were applied to four watersheds while one watershed at each site was left untreated as a control. Precipitation, runoff, and sediment yields were measured through 2007. Between 2002 and 2006, 11 rain events produced runoff in the contour-felled log site and 12 events produced runoff in the mulch site. The minimum rainfall required to produce runoff was 4.3 mm, while the 10-minute maximum intensity that produced runoff ranged from 9.1 to 72 mm hr^-1. Snow melt did not produce runoff in any of the watersheds. Runoff from all six watersheds was flashy and heavily sediment-laden. Event runoff in the control watersheds was between 0 and 8.6 mm in the first year after the fire and between 0 and 0.6 mm 5 years later. The maximum peak flow rate in a control watershed occurred two years after the fire and was 7.1 m³ s^-1 km^-2. The mean annual sediment yields in the control watersheds were 23 Mg ha^-1 yr^-1 in 2003 and 22 Mg ha^{- 1} yr^-1 in 2004. Only one site produced sediment from one event each in 2005 and 2006; the sediment yields from the controls for these events were 5.1 and 2.1 Mg ha^-1, respectively. The contour-felled log and straw mulch watersheds produced less runoff, lower peak flows, and less sediment than their controls. The hydromulch watershed responses were closer to, if not greater than, those in its control. Salvage logging did not produce any measurable increases in runoff or sediment yields relative to its control. With large hydrologic responses occurring in these watersheds 5 years after the fire, it is clear these sites have not yet recovered to their pre-fire condition.
DE: 1804 Catchment
DE: 1815 Erosion
DE: 1850 Overland flow
DE: 1879 Watershed
DE: 1895 Instruments and techniques: monitoring
SC: Hydrology [H]
MN: 2007 Fall Meeting