Controls on Suspended Sediment Concentrations and Turbidity within a Reforested, Southern Appalachian Headwater Basin

Water quality data collected between 2007 and 2014 within the Allen Creek Watershed were used to: (1) determine the factors controlling the temporal variations in turbidity and suspended sediment concentration (SSC) within a representative, high-gradient headwater basin in the Southern Appalachians; and (2) assess the recovery of water quality following extensive logging operations during the early to mid-1900s. Regression analysis suggests that suspended sediment is primarily derived from upland areas and variations in concentration reflect rainfall intensity and total event precipitation. Overall, SSC and turbidity were low in stream waters in comparison to both reference values for stable streams and more developed basins in the region. Some floods were characterized by high SSC values, but limited turbidity and vice versa. Differences in measured SSC and turbidity between storms reflect different controls on the two parameters, and the apparent influence of natural organic matter on turbidity during rainfall events that are incapable of transporting sediment to the channel via overland flow. Low SSC and turbidity values are presumably related to the reforestation of hillslopes and riparian buffers following the cessation of logging operations. They also are due to a historical reduction in the sedimentological connectivity of hillslopes and tributaries with the axial channel that occurred during logging operations. OPEN ACCESS