The Yakama Nation Fisheries team identified chronic sediment interference and poor fish passage performance for a critical fishway project which is used to bypass a steep series of cascading falls on the Klickitat River. The fishway is a 200-foot-long tunnel blasted into the basalt canyon wall and was originally fitted with vertical slot baffles to provide passage around the falls. A weir was added near the exit to reduce sediment deposition; however, due to a poor weir design, sediment deposits moved over the weir, filled the baffles, and created a significant barrier, preventing upstream fish passage for steelhead and salmon through the fishway.
Kleinschmidt led the investigation into causes of the sediment deposition, analyzing system hydrology and the river’s hydraulic characteristics related to the existing weir system. Through detailed hydraulic modeling over various flows, velocities correlated to various sediment sizes and habitual transport/deposition patterns. With knowledge of the hydraulics and transport/deposition regime, Kleinschmidt developed several alternatives, including an inflatable weir conceptual design that used an Obermeyer system to selectively raise and lower up to three different weir sections depending on flows to redistribute sediment and reduce deposition in the tunnel and at its outlet. Given unique site conditions, constructability considerations were accounted for in the cost estimating process.
Kleinschmidt’s innovative approach uses an inflatable weir design to redistribute sediment in the river system, offering a promising solution to a longstanding sediment deposition problem. Early modeling results reflect a high probability of reducing sediment deposition in the tunnel while retaining natural material in the river system and providing gravel for downstream spawning habitat.
Regional Vice President
Paul Larson, P.E.
Paul Larson has 28 years of hydropower and infrastructure experience and is Kleinschmidt’s Northwest Regional Vice President. and specializes in the management of technical teams relative to engineering and utility operations. Paul has managed cross-disciplinary teams on a wide range of hydropower generation, transmission, and distribution projects and other projects for clients in the Northwest....