Large Woody Debris Fish Habitat Structure Performance And Ballasting Requirements PDF Download

Large woody debris recruitment to streams from adjacent riparian forests influences stream channel morphology, sediment routing, and fish habitat. A mathematical model was developed to 1) determine whether the trees in a stand adjacent to a stream, upon falling, would provide large woody debris of a specified size to the stream and 2) determine the volume of trees, upon falling, that reach a stream over a specific time period. The model considered stand and topographic parameters such as tree size, tree form, distance from the stream, hill slope gradient, stream gradient, stream width, riparian buffer width, and basal area of the stand. The likelihood that a tree of a specified size will reach the channel is the probability the tree will fall in a given direction evaluated at 1 degree azimuths from 0 to 360 degrees multiplied by the probability it is tall enough to reach the stream. Volume estimates were calculated by multiplying estimated tree volumes by the joint probabilities. A test riparian polygon comprised of Douglas-fir (Pseudotsuga menziesii {Mirb.] Franco) was selected to illustrate how the model predicts large woody debris recruitment of both key pieces and volume to an adjacent stream. Estimating large woody debris recruitment to streams from adjacent riparian stands over several decades may be useful in determining effectiveness of various configurations of riparian buffers and provide assistance in the prediction of the future quality of aquatic and terrestrial habitats in riparian zones. This model provides one way to estimate where large wood is coming from within a riparian leave area and could be useful in determining necessary widths for riparian areas that are intended to provide large woody debris recruitment over time.