CGRG Bibliography of Canadian Geomorphology
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Author : Beaudry, L.
Date : 2004.
Title : Large woody debris replacement in small headwater streams in central British Columbia.
Publication : Forest Land – Fish Conference II. Ecosystem Stewardship through Collaboration, April 26-28, 2005. Edmonton, Alberta.
Issue :
Page(s) : 13-14.
Abstract
To identify the effect of current riparian management practices on long-term large woody debris (LWD) levels we are adapting a woody debris depletion model for use in north-central British Columbia. LWD is important in headwater streams, it infl uences channel morphology by creating pools and trapping sediment and organic material, improving in-stream habitat. LWD provides a substrate for invertebrates and algae that will drift downstream to provide fish food. The model is being applied to a series of experimental watersheds located in the vicinity of Prince George. The project is part of a cooperative small stream research project investigating the effects of riparian management strategies on the ecology of small streams. We measured the quality and variability of LWD in a series of undisturbed small streams with bank-full widths between 80 and 160cm, and gradients less than 6%. The streams run through a variety of stand types and parent materials, and are located across a wide range of regional precipitation regimes (440-900mm year). Within each of the twelve streams, one or more 50m reaches were sampled. For each reach, all in-stream woody debris greater than 5cm in diameter was measured and described. An inventory of the riparian stand by species and size class was compiled for 10m on either side of the stream. Current levels of LWD in all the streams were between 26 to 100 pieces per 50m of stream length. Over 30% of this woody debris provided hydraulic function at low stream flows. In all streams measured, over 40% of the LWD was in the size class “5 to 15 cm in diameter” and at least one piece (to 15 pieces) of LWD was in the size class “> 30 cm diameter”. Lodgepole pine leading stands had fewer LWD pieces greater than 30cm diameter (1 to 2 per 50m). The proportion of large trees was 3 to 4% lower in the stream than in the undisturbed adjacent riparian stand. Small streams have large wood as natural instream components, which require replacement over time. Two to 40% of LWD was classifi ed as wood that is not yet in the stream but lying above the
Bibliography of Canadian Geomorphology