Piney River (Nelson County) - 1.) The "Big Piney" (Alhambra to VA. 827 ['Perkins Mill Rd'] Woodson) (VA)
400 to 450 is a good guide to minimum flow. The upper range of flow will, of course, vary depending on individual groups' skill level and disposition.
The second of the low water bridges. Get out and take a look. Can usually run either far right or far left.