Morphology and Channel Evolution of Small Streams in the Southern Blue Ridge Mountains of Western North Carolina

Small streams are understudied in the Southern Blue Ridge Mountains, yet they constitute a huge portion of the drainage network and are relevant with respect to human impact on the landscape and stream restoration efforts. Morphologies of 44 streams (0.01 to 20 km² watersheds) from western North Carolina are characterized and couched in the context of historical channel evolution and human impacts. Topographic cross-sections and longitudinal gradients, channel and floodplain widths, and bed particle sizes are the basic data. Regression equations describe channel form. New optically stimulated luminescence, radiocarbon, and cesium-137 dates resolve channel evolution. Results indicate that channels behave in a predictable linear fashion of changing in response to increasing watershed size. However, forested reaches have much wider channels than pastured/grassland reaches, indicating more than 50 percent loss of instream habitat related to conversion of riparian forest to pasture/grassland in some cases. Floodplain widths conservatively indicate long-term (century-scale) lateral erosion rates of about 0.5 to 5.0 cm/yr. Colluvial inputs are probable drivers of channel form and particle size on the smallest headwater streams. The modern floodplain appears to have established itself in the early 1900s and it is still evolving.