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<br />property. After more than half a century of active fire suppression, which
<br />increased the threat of catastrophic wildfires, greater emphasis was placed
<br />on prescribed burning in forest lands to reduce the buildup of fuelwood
<br />began in the late 1950s (Weise and Martin, 1995). Since 1984, prescribed
<br />burning has been used on an average of 1,200 km2 per year in about 773,000
<br />km2 of US national forests (USFS, written commun., 1997). Most studies
<br />done to assess the effects of wildfires on watershed hydrology have been
<br />for chaparral vegetated areas (dense, low evergreen oaks) in southem
<br />California (e.g., Florsheim et aI., 1991; Weise and Martin, 1995). Fewer
<br />studies have been done for other forest ecosystems and most focus on
<br />sediment runoff (e.g., White and Wells, 1981; Parrett, 1987; Meyer et al.,
<br />1995; Cannon et aI., 1995; Ewing, 1996). Because southern California
<br />differs from vegetation and soil types in other forested areas in the
<br />United States, study results, may not be transferable or may need to be
<br />modified fo different forest ecosystems. Hydrophobic (water-repellent
<br />soiis) conditions often develop after a wildfire from the burning of oils
<br />in vegetation that coats soil and substantially reduces infiltration (USFS,
<br />1979a). Hydrophobic soils, decreased vegetation cover, and reduced surface
<br />storage following wildfires dramatically increase the potential for extreme
<br />flooding, sediment transport and deposition (USFS, 1979b).
<br />Fire-suppression activities also make it difficult to estimate the natural
<br />frequency of fires from historical fire records and for ecosystem
<br />management.
<br />
<br />Study Area
<br />
<br />The community of Buffalo Creek is iocated in unincorporated Jefferson
<br />County in the foothills of Jefferson County within Pike National Forest
<br />near the confluence of Buffalo Creek and North Fork (NF) South Platte River
<br />(fig. 1). The community, at an elevation of about 2,012 m, consists of
<br />several hundred residential homes within a montane forests (predominantly
<br />lodgepole and ponderosa pine, douglas fir, and aspen). Topography is
<br />rugged and soils are shallow, coarse sand (pea gravel), and generally are
<br />moderately well drained (Colorado Water Conservation Board, 1997). Bedrock
<br />on average is about 1 m below ground, but is exposed on many steeper
<br />hillslopes. Accumulation of organic litter (duff) on unburned forested
<br />areas averages about 60 mm. The climate is semiarid and mean annual
<br />precipitation is about 400 mm, much of which falis as snow from about
<br />October through April. Streams are ephemeral in the burned area and flow
<br />into the NF South Platte and South Platte Rivers, which primarily are fed
<br />by melting snowpack. Flood flows in the vicinity of Buffalo Creek can
<br />result from flash flooding from intense, localized thunderstorms,
<br />generalized rainstorms, and spring snowmelt (Jarrett, 1990). Long-time
<br />residents reported no significant flooding in the Buffalo Creek area in at
<br />least 70 years. The 1996 wildfire, driven by strong winds, burned most
<br />vegetation and produced hydrophobic soils in much of the burned area.
<br />
<br />Methods
<br />
<br />No systematic precipitation, streamflow, and sediment monitoring networks
<br />existed in Buffalo Creek prior to the wildfire. In April 1997, four
<br />recording precipitation and three streamflow gages were placed in Buffalo,
<br />Morrison, and Spring Creek basins by the USGS in cooperation with the
<br />Denver Water Department (John Moody, USGS, written commun., 1997). The NWS
<br />provided 13 Buffalo Creek residents with non-recording precipitation gages
<br />to assess the spatial variability of rainfall, monitor flood potential, and
<br />assess/refine rainfall estimates from Doppler radar (NWS-WSR-88). Few
<br />raingages are located in the burned area, therefore, a basin-wide
<br />monitoring approach was undertaken to document each runoff event.
<br />Paleoflood hydroiogy is the study of flood-transported sediments and
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