COMPARISON OF ANTHROPOGENIC EFFECTS ON BEDLOAD PARTICLE SIZES TRANSPORTED BY PIEDMONT STREAMS OF CENTRAL NORTH CAROLINA

Billions of dollars have been spent on the physical restoration of Atlantic-margin waterways in an effort to minimize water pollution and restore biological integrity. However, little research exists on the physical conditions of stream channels prior to Euro-American settlement of the Carolina Piedmont. We hypothesize that the maximum size of bedload (cobbles and boulders) being transported by piedmont streams of central North Carolina has increased following post-European American landscape modification resulting initially from agriculture and more recently from urban and suburban development.

Ready and Crabtree Creeks located within the boundaries of Umstead State Park, Wake County, North Carolina were the focus of this study. Field procedures consisted of 1) detailed geomorphic assessment of target areas, 2) sediment characterization and sampling of the size of the current bedload, channel bars, and stream banks, (3) sediment characterization and sampling of pre-European bedload and channel bar deposits preserved beneath anthropogenic valley-bottom legacy sediments that crop out in modern stream bank exposures, and 4) cross-valley coring beneath former millpond sedimentary deposits and shallow subsurface geophysical surveys to investigate the extent of pre-European axial channel gravel deposits. Preliminary results demonstrate that the bedload particle size of pre-European channels is significantly smaller than the bedload being transported by the investigated reaches of the two study streams today. Restoring geomorphic and ecological function to impaired piedmont streams will depend in part on an increased awareness of baseline physical characteristics prior to the initiation of substantial anthropogenic modifications, some beginning as early as the Colonial era.