Where is the culvert door?

Culvert outlet of a river, channel or reservoir. It is usually built at the outlet of culverts in rivers, channels or reservoirs to prevent water from flowing too fast or too slow, causing floods or wasting water resources. Culvert sluice is a common sluice type in hydraulic engineering, which is used to regulate water flow and control flood. Culvert sluice is a sluice facility located at the outlet of culvert, and its main function is to control water flow in and out, slow down water flow speed and change water flow direction.