Robert Einhellig, Connie Svoboda, Warren Frizell, Nathan Cox. 2010. "Physical Modeling of the Folsom Dam Tailwater Confluence Area". Bureau of Reclamation, Report Number PAP-1023.
Abstract: Folsom Dam, located upstream of Sacramento on the American River in central California, was designed and constructed by the USACE. The Bureau of Reclamation (Reclamation) has operated Folsom Dam since construction was completed in 1956. Various hydrologic analyses which include the period of record since the project’s completion have led to a substantial increase in the identified Probable Maximum Flood (PMF) for the facility, as well as an increase in the identified flood risk for the Sacramento area. To address the dam safety and flood protection concerns raised by the most recent hydrologic information and analyses, Reclamation and the USACE agreed to work together on a Folsom Dam Joint Federal Project (JFP). The current JFP plan includes increasing both the low-level and total release capacities of Folsom Dam through the addition of an auxiliary spillway. Design of the auxiliary spillway was facilitated through the use of several physical model studies. A 1:48 scale Froude-based model of the proposed auxiliary spillway and the main dam spillway confluence was constructed in Reclamation’s laboratory in 2007. This model includes the main dam spillway (all 8 gates) and the lower chute, stepped chute, stilling basin, and exit channel of the proposed auxiliary spillway, their confluence with the American River, and several hundred feet of river downstream from the new bridge across the American River. The primary purpose of the model was to evaluate flow conditions in the confluence area after completion of the JFP. During the design process, the scope of the model study was expanded several times to include evaluations of main dam spillway capacity, energy dissipation on the auxiliary spillway steps, and auxiliary stilling basin performance with various baffle block arrangements designed to minimize cavitation potential. Evaluation of various design concepts in the model proved to be invaluable and led to cost savings in the final design.
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