Total Suspended Sediment Dynamic Under Managed and Unmanaged Conditions in Headwater Watersheds

This study examined the long-term effects of timber harvesting on total suspended sediment (TSS) in the Piedmont region of North Carolina. It focuses on two headwater catchments (HF1 and HF2) at Hill Demonstration Forest that were converted from hardwoods to pines 12 years ago and continuously monitored for streamflow from 2008 to 2023, and TSS from 2010 to 2013 and 2023. In 2011, HF1 was cleared, and a 15.2-meter vegetated riparian buffer was left around the stream. Selective harvesting in the riparian buffer of HF1 reduced basal area by 27%. The harvest followed the North Carolina Neuse River Basin Riparian Buffer Rule to protect water quality. Following the clearcut, loblolly pine trees were planted in HF1. HF2 was preserved in its natural state to serve as a reference watershed. While TSS concentration did not change significantly after the clearcut from 2011 to 2013 in either watershed, TSS load in the treatment watershed increased substantially, likely due to increased total discharge and movement of in-channel legacy sediment. There were also significant relationships between precipitation and streamflow and TSS load in both HF1 and HF2 watersheds. The close relationship in sediment concentration between HF1 and HF2 indicates sediment dynamics are influenced by increasing weather extremes. Our study provides watershed land managers with important water quality information about managed and unmanaged headwaters.