Prevention of Bedload Transport in a Lateral Water Intake by a Guiding Structure in a Mountain River

A lateral intake withdraws water from the Lech River, a mountain river characterized by high bedload and coarse substrate, to supply a hydropower plant. The water intake features a flushing channel that experiences sedimentation several times a year. Hydraulic sediment removal from the riverbed upstream of the facility and the flushing channel requires a drawdown of the backwater level, resulting in economic losses for operators and reduced green energy production. Therefore, it is essential to prevent sediment aggradation in the flushing channel and the intake of the hydropower plant. Physical model tests with geometric scales of 1:25 and 1:15, respecting Froude similarity, were conducted to explore different sediment guiding structures with objectives to (1) prevent bedload deposition in the flushing channel and bedload transport in the intake of the hydropower plant, (2) enable efficient hydraulic sediment removal from the flushing channel, and (3) provide general insights into the design of guiding structures. The proposed solution combines a deflector, a guiding wall, and a nonerodible area. The deflector serves as a pivotal element in the design proposed in this study. It connects the guiding wall to various bank geometries and protects the flushing channel from sedimentation. This final design optimizes the structure’s size, with variations in the inclination of the guiding wall showing that the best sediment rejection occurs at minimal inclination relative to the main flow direction. Consequently, sediment can be diverted parallel to the wall and discharged downstream via the sluice gates. Additionally, the intake area’s flushing capacity can be maintained by implementing a notch in the guiding wall, which allows for efficient hydraulic sediment removal. Finally, the area between the guiding wall and water intake is protected against erosion to prevent unwanted sediment mobilization.