A side weir is a hydraulic control structure used to divert flow from a main channel into a side channel when the water level in the main channel exceeds a specified limit. Side weirs, also known as lateral weirs, are flow diversion devices widely used in irrigation as a head regulator of distributaries and escapes, land drainage, and urban sewage systems. The geometric shapes of side weirs could be rectangular, triangular and etc. Also these geometric shapes would be used in plan which are known as labyrinth side weirs. The studies on the subject have been generally focused on rectangular and triangular side weirs located on a straight channel. However, the same is not true for labyrinth side weirs. In this study, the hydraulic characteristics of triangular labyrinth side weirs with various length in subcritical flow were considered. Discharge coefficient, water surface profiles, variation of specife energy, three-dimensional velocity distributions over the side weir, variation of angle over the side weir were investigated. Results show that the discharge coefficients of triangular labyrinth side weirs have much higher values than those of justify; LINE-HEIGHT: normal; MARGIN: 0in 0in 0pt; unicode-bidi: embed; DIRECTION: ltr; mso-layout-grid-align: none" dir=ltr Key words: Discharge coefficient, Flow angle, Triangular labyrinth side weir, Velocity distribution, Water surface profile
