Abstract: To address severe bed load sedimentation at the intake of a diversion-type hydropower station, this study works out a new L-shaped structure of sediment diversion sills. A laboratory scale model experiment and numerical simulations are used to study the behaviors of these sills on a movable-bed in a case study of a large diversion-type hydropower station. Their hydraulic characteristics and sediment exclusion effectiveness are examined using comparative analysis against the traditional sills of straight shapes, focusing on the effects of their layout parameters (spacing, height, and angle) and hydraulic parameters. Results demonstrate the L-shaped sills achieve superior sediment exclusion performance, effectively diverting sediment away from the intake while minimizing sediment migration behind them. The sill height imposes a critical influence on exclusion efficiency－a 2 m increase leads to a 59% reduction in sediment deposition volume behind the sediment retention sill. The diverting sills maintain effective sediment control under varying diversion ratios and Froude numbers, but as both parameters increase, sediment migrates toward the first upstream sill and deposition increases on its lee side and behind the retention sill. And, the structure causes minimal extra head loss－its average head loss is as low as 0.069 m at the relative sill height of 5 m. Thus, the L-shaped sill and its design provide a novel solution to sediment control in water intake structures.

Key words: diversion-type hydropower station, water intake, L-shaped sediment diversion sill, hydraulic characteristics, sediment exclusion effectiveness, numerical simulation, movable-bed physical model experiments