Abstract:
Amounts of natural debris in small headwater streams under old growth
stands of Douglas-fir vary from 6 1/2 tons per 100 ft. of stream
to 26 tons per 100 ft. of stream, depending on terrain and timber
characteristics and sequence in the natural accumulation-flushing
cycle. Approximately 10% of the weight of total debris is in the size class
smaller than 10 cm in diameter.
After falling, there was an increase of debris depending on stream
protection measures, falling methods and environmental factors.
After yarding, the amount of total debris was reduced on the
average to almost 50% from what it was originally. At the same time,
the amount of branch-type debris increased although the amount of finer
debris (<1 cm) decreased.
A wide buffer-strip provided an almost complete physical barrier
against debris movements, while a very small buffer-strip provided much
less stream protection in terms of logging residue. Cable-assist
falling methods minimized breakage and provided for cleaner yarding as
compared to conventional timber falling.
