Flap gate
хавхлагат хаалт
клапанный затвор
A gate hinged along one edge, usually either the top or bottom edge. Examples of bottom-hinged flap gates are tilting gates, and fish belly gates so called from their shape in cross section.
Source Guidelines on Instrumentation on Large dams by Central Water Commission Ministry of Water Resources, River Development & Ganga Rejuvenation Government of India, June 2017, p.73Зураг