CHANNEL MORPHOLOGY, LOCAL RIPARIAN CONDITION, AND BASIN LAND COVER ASSOCIATIONS; SOUTHERN APPALACHIANS

Previous research has shown that the elimination of tree cover in riparian zones results in narrower channels for channels less than 20m wide. In this research, we investigated the effects of riparian vegetative conditions on a suite of channel morphological variables: active channel width, the variability of width within a reach, large wood frequency, habitat distribution, median particle size, and percent fines. We measured channel characteristics on 47 wadeable streams throughout the Upper Little Tennessee River Basin in the Southern Appalachians. The results indicate that riparian forest conversion has reduced active channel width and the variability of channel width, reduced wood frequency, simplified habitat, and reduced median particle size. We also found that channel width was better predicted by the ratio of drainage area to local channel slope (A/s) rather than drainage area alone. When channel widths were evaluated against this width predictor, the relative effect of riparian conversion on channel width was nearly invariant across the range of A/s. Channels with grassy riparian zones were one third the width of channels with forested riparian zones. Riparian forest conversion also increased maximum daily stream temperatures by several degrees. The data suggest that even modest increases in the extent and width of forested riparian buffers would substantially improve stream habitat conditions for native aquatic species.