4.6 Undersluice and Silt Excluders

• The openings provided on the wall of a weir with their crest set at a lower level are called undersluices.
• Undersluices are provided with adjustable gates.
• Weir and diversion headwork are constructed in the middle position, whereas undersluices are constructed at the ends and adjacent to canal head regulators.
• Undersluices are separated from the weir by the divide wall.
• Silt gets deposited in the pocket just upstream of the undersluice.
• They are also called scouring sluices.

Functions of Undersluices

• Maintaining a clear and well-defined river channel
• Scouring away deposited silt
• Passing low floods without dropping weir crest shutters
• Controlling silt entry into the canal
• Lowering flood level