A device which fits on the downstream end of a culvert pipe or sluiceway which reduces the hydraulic energy of high velocity water flows. Arranging for the discharge to strike a large rock, log, etc., can also dissipate the energy of the flow. This is sometimes used in the absence of a downspout on the downstream end of a culvert or sluiceway to prevent severe erosion of a stream bank where the outlet is high above natural stream grade.