STREAM CAPTURE ALONG THE LINVILLE RIVER AS A DRIVER OF INCISION AND GORGE FORMATION

The asymmetrical Blue Ridge Escarpment divides low-gradient west flowing streams from high-gradient east flowing streams in the southern Appalachians. Specifically, the steeper slopes on the south and east side of the escarpment have a lower base level which provides an opportunity for stream capture from the west-flowing streams on top of the escarpment. The Linville River crosses the Blue Ridge Escarpment indicating a likely stream capture event. This is supported by quartzite cobbles found on large terraces to the west of the Linville River that must have been sourced from the east of the river. Additionally, “hanging” valleys exist to the east of the river indicating a previous gradient that was much lower than the current tributary gradients. The capture event would have tripled the drainage area of the Linville River. The resulting increase in discharge likely drove incision in what is now Linville Gorge - forcing responses from adjacent hillslopes and tributaries. Broadly, large drainage capture events, including the Linville River and others like it, can create dramatic topography and help maintain the high relief of the ancient escarpment. However, these events are spatially infrequent and preliminary data suggests that smaller, more common drainage captures and reversals likely play a role in escarpment retreat and preservation.