MORPHOLOGY AND EVOLUTION OF THE LINVILLE RIVER, NORTH CAROLINA, USA

Fluvial terraces are recognized as indicators of environmental shifts within a stream system including tectonic activity, climate change, and anthropogenic alteration. In the Blue Ridge physiographic province in North Carolina, at least one terrace is consistently present along most streams. However, it is unclear whether these terraces are the result of past changes in climate or a legacy of human activity. Here, we examine the evolution of the Linville River by mapping the terraces and then examining soil development on those terraces. Additionally, we use charcoal samples to age the surfaces. Our mapping indicates the presence of a lone terrace with variable morphology throughout the forty-mile stretch encompassing the Linville River – including both reaches above and below Linville Falls. In the upper reaches, valleys are wide and low gradient allowing for more extensive terrace formation while the lower reaches are constrained by valley-width and terraces only form in rare, wide reaches. Terraces comprise coarse sediments along the modern channel but finer, sandy sediments away from the modern channel. We interpret this sedimentology to indicate that the channel has remained relatively in place while periodic flooding aggrades sandy sediment across the terrace surface. Below Linville Falls, radiocarbon ages and cumulic soils suggest consistent aggradation over the past ~ 6ka. Above Linville Falls, buried soils 0.5 m underground indicates at least one period of stability during aggradation. These findings suggest that terraces in the area do not comprise legacy sediments like many other deposits in the region. Instead, it would appear that aggradation of sediments is likely the result of consistent, high magnitude floods in the latter half of the Holocene.