Water Resources Collections and Archives

Lower Silver Creek in San Jose, California has been extremely altered by urbanization and is susceptible to major flood events. Multiple flood control projects have been proposed over the last thirty years and an environmentally conscious plan is currently under construction. The purpose of this study was to assess how the flood control plan of Lower Silver Creek evolved, to compare how well a built reach of the project (reach 1a) complied with the design documents, and to establish permanent benchmarks to assist future project monitoring. The first single-purpose plans for Lower Silver Creek recommended excavating the channel and lining it with concrete to prevent flooding. The most recent plan (1998) simultaneously addressed the flood problem using less concrete, introduced fish habitat, increased riparian vegetation, and attempted to return some geomorphic processes to the creek. Overall the earthen reach matched the design drawings; however the slope was an order of magnitude higher and the roughness was much lower because there was no vegetation at the time of the study. As a result the maximum velocity and shear stress were higher than designed and may result in substantial erosion. The establishment of vegetation prior to a major storm event is a major factor in the success of the project.