Sandy Run (Occoquan River tributary)Sandy Run is a long second-order tributary to the Occoquan River in Fairfax County, Virginia.CourseSandy Run rises on the Pope Head Creek divide and then flows south to join the Occoquan River about 3 miles northwest of Occoquan, Virginia.WatershedSandy Run drains of area, receives about 43.5 in/year of precipitation, and is about 69.29% forested.