Piedmont Drainage
• The Piedmont is drained by five major river systems: the Potomac, James, Roanoke, Rappahannock, and York. Tributaries of the Chowan River in North Carolina drain part of Virginia’s Piedmont.
Map of Virginia's major drainage basins. Note that the Potomac, James, and Roanoke Rivers all begin west of the Piedmont and Blue Ridge, whereas the Rappahannock, York, and Chowan systmes form in the Piedmont. (Image from College of William and Mary geology website, courtesy of C.M. Bailey)
• Piedmont streams are typically dendritic and flow southeastward across the northeast-southwest regional trend of the bedrock structures.
Close-up of a central Piedmont drainage system showing the dendritic pattern of streams. Because the Piedmont streams flow across the northeast-trending regional structures, some geologists think that the Piedmont rivers formed on an older surface. This older surface might have been developed on ancient Coastal Plain sediments (now eroded away) that sloped toward the southeast like the present Coastal Plain.
(Image courtesy of the Virginia Division of Geology and Mineral Resources)