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 first of the two low water bridges. get out on the right and take a look. Can usually run on the right if the level is reasonable. Avoid the nasty culvert in the middle.