A selective wood removal technique to expose coarse substrate in small sand-embedded streams

Many Wisconsin Lake Superior tributaries contain large sand bed loads which are retained in channels by abundant woody debris and beaver dams.  A selective wood removal method has been developed and used by Wisconsin Department of Natural Resources staff to specifically target the embedded spawning habitats of headwater trout streams.  Primary objectives of this study were to detect significant changes in (1) sand content, (2) coarse bottom substrate, and (3) evaluate the biotic response to this method.  Treatment effects were compared between a treatment and an upstream reference station before and after treatment.  In addition, a downstream reach was monitored for effects of transported sediment.  Treatment station wood removals induced fine sediment transport, exposed underlying coarse bottom substrates, narrowed stream widths, and increased flow velocities.  Numbers of fall spawning redds and habitat for macroinvertebrates also increased.  Reference station physical conditions were unchanged.  After treatment, the released sediment flux caused aggradation of the downstream reach, but near pre-treatment conditions returned by one year post removal.  These findings support the selective wood removal method as a viable, cost-effective technique for increasing spawning and macroinvertebrate habitat in headwater reaches of small sand-laden streams.