Author(s): Matt Gellis; Ed Zapel
Linked Author(s):
Keywords: No Keywords
Abstract: Recent interest in restoring anadromous steelhead (Oncorhynchus mykiss) populations in Mission Creek on the south coast of California has lead to a series of fish passage assessment and alternatives evaluation studies. Most recently, a physical scale model of the Mission Creek flood control channel was constructed in the laboratory and a suite of channel modification alternatives were tested to determine their suitability for achieving upstream fish passage. Results of the modelling work showed that flow velocity, depth, channel capacity and sediment transport criteria could be met without increasing the overall footprint or gradient of the larger flood control channel, by excavation of a low flow concrete subchannel with low weirs and sidewall indentations in the existing channel apron. Similarly sized and larger sub-channel alternatives constructed with large embedded roughness elements designed to provide velocity cover had adverse impacts on channel flood flow capacity and sediment transport characteristics. The preferred design met fish passage criteria over the limited range of passable channel discharges, did not increase flood water surface elevations, successfully passed expected sediment, and is expected to meet the construction cost limitations anticipated by the City of Santa Barbara. The observations made during the scale modelling efforts will prove useful in future investigations of fish passage modifications to other paved South Coast steelhead streams. Modelling results have already been applied to a similar fish passage modification project on San Jose Creek, located to the west of Mission Creek in the City of Goleta, California. The lessons learned in the Mission Creek model about effective roughness created by embedded roughness elements and hydraulic characteristics contributed by the sub-channel features were applied to the numerical and physical modelling investigations supporting the physical design of the San Jose Creek flood control channel.
Year: 2009