Photo Credit: Alex Mead
This is the spillway of a medium sized dam on the Huron River in Michigan. When water is released down the spillway it exits under a sluice gate in the supercritical flow state. Supercritical flow, however, has too high a velocity for the natural river bottom and will cause an erosion issue. To prevent this fast flowing erosive water force concrete blocks, called baffle piers, are added just downstream. This causes a hydraulic jump to occur transferring the flow from supercritical flow to subcritical flow. Subcritical flow is closer to natural river flow and is therefore less of an erosive force. The baffle piers of this dam can be seen under the water about two-thirds up the page.