Abstract: A subterranean drainage unit for protecting a structure by intercepting subsurface fluid flows, comprising a sheet base member having parallel first and second planar surfaces, regularly spaced discrete frusto-conical members projecting from the first planar surface creating intersecting channels to allow for lateral and vertical uninterrupted flow of fluid, the second planar surface being constructed and arranged to cohesively adhere to the surface of the structure being protected and a filter media supported by the projections to maintain a substantially rigid surface which is non-interfering with the flow of fluid within the intersecting channels.