Abstract
Labyrinth weirs can pass more flow than conventional weirs with fixed openings for the same headwater, thanks to their increased crest length. However, nappe interference and local submergence in downstream cycles reduce discharge efficiency. This study experimentally and numerically investigated stepped-in-plan labyrinth weirs, designed to minimize these issues. Four stepped weirs and a diagonal linear weir were tested under the same crest length and free overflow conditions, and compared with conventional labyrinth weirs. The results showed that, for constant crest length and head, discharge efficiency decreases with more steps, mainly due to flow separation and turbulence on the weir walls, unlike traditional labyrinth weirs.