STREAM CHANNEL MORPHOLOGY AND WOODY DEBRIS IN LOGGED AND UNLOGGED BASINS OF WESTERN WASHINGTON

Channel morphology and habitat characteristics of stream segments drai ning unharvested old-growth forests were compared with those from stre ams within intensively and moderately logged basins. Sites covered a b road geographic range in western Washington State and were stratified by basin area and channel gradient. Although the number of pieces of l arge woody debris (LWD) within stream channels was unaffected by timbe r harvest, there was a clear reduction in LWD size in harvested basins . Timber harvest also resulted in a shift in location of LWD towards t he channel margins, outside the low-flow wetted width of the channel. Intensive harvest simplified channel habitat by increasing riffle area and reducing pool area and depth, although the commonly used index of pool-to-riffle ratio appears inadequate to document these changes. Gi ven the natural variation from stream to stream, we conclude that simp le counts of instream LWD and channel units (habitat types) are not us eful as management objectives. Instead, these attributes should be use d collectively as indicators of the complexity and stability of in-str eam habitat with respect to the specific channel and valley geomorphol ogy.