Effects of Wildfire on In-Channel Woody Debris in the Eastern Sierra Nevada, California 1

Management of in-channel woody debris after wildfire is controversial. Post-fire increases in stream discharges can cause more frequent downstream flooding. The resulting heightened transport and accumulation of debris can wash out bridges and cause other damage. Inchannel debris is sometimes removed or cut into smaller pieces to expedite flushing through the system and to avoid debris jam formation. Biotic values of debris for fish cover, pool formation, sediment storage, and food sources for invertebrates and microorganisms are lost or reduced, however, when debris is removed or cut up. Information on debris dynamics after wildfire in the Sierra Nevada is scant. Changes in debris frequency, mobility, volume, aggregation, and carbon loading after a 1994 wildfire in the eastern Sierra Nevada were quantified by before and after comparative measurements at Badenaugh Creek in northern California, and by comparing selected attributes to a nearby “reference” stream. Fifty-seven percent of wood volume, and 25 percent of the pieces, were consumed by the fire. The fire reduced aquatic carbon loading from about 2½ to 1½ times terrestrial loading after the fire. Although more pieces moved 1 year after the fire at Badenaugh Creek than in the control stream, the size and number of debris jams both immediately and 1 year after the fire were appreciably reduced from pre-fire levels, probably because fewer pieces were available to form aggregates. Decisions on the disposition of post-fire debris must consider the interaction between fire intensity, channel width, and the size of the remaining wood. If few pieces of channel-spanning length remain after a fire, they may pose relatively little downstream danger.