Page - 133 - in Book of Full Papers - Symposium Hydro Engineering

Hydrologic engineering analyses also included seasonal analysis of Lake Oroville inflow volume-frequency. Products included the following: 1. Inflow volume-frequency curves for 1-, 3-, 7-, 15-, and 30-day durations for each month. 2. Hydrographs derived from the monthly frequency curves. These were used to develop inflow hydrographs, which were used as boundary conditions for flood routings with the HEC-ResSim model. 3. Results of flood routings with HEC-ResSim for a set of operation scenarios. 4. Monthly Lake Oroville elevation-frequency analysis information for a variety of design and operation alternatives formulated by DWR. Challenges in the hydrologic engineering analysis for Oroville Dam included: (1) the need for quick turnaround to provide information critical for decision making about recovery; (2) common difficulties calibrating a precipitation-runoff model and determining appropriate initial and boundary conditions for application with extreme events; (3) the risk of misunderstanding or misinterpreting model results as critical decisions were made; and (4) requirement for concurrence by FERC and DSOD with PMF calculations and conclusions about dam safety based on routing the estimated PMF. Solutions included: (1) the use of cloud computing, with parallel model runs on multiple servers in the Amazon cloud, and multiple modelers to configure and execute model runs and synthesize results; (2) the use of the wealth of hydrometeorological and operational data collected and stored by DWR in the California Data Exchange Center, which is accessible at http://cdec.water.ca.gov; (3) careful communication to decision makers of the results by DWR and consultant experts; and (4) continuous collaboration and coordination with reviewers and regulators through in-person meetings, a series of webinars, and technical memorandums for which review and comments were solicited. 6. HYDRAULIC ENGINEERING ANALYSES DURING RECOVERY Hydraulic engineering analyses were critical to the quick recovery of Oroville Dam’s FCO Spillway chute and Emergency Spillway. The analyses completed included the following:  Simulation of behavior of flow in the FCO Spillway chute to inform decision makers by the DWR design team. This included computation of water surface elevation profiles and hydraulic forces to inform decision makers about chute curvature and alignment, wall heights, and other design properties. It also included assessment of aeration and cross waves in the chute, and evaluation of cavitation potential due to high velocity flow in the chute. Reviews of the original design, maintenance records, and historical performance of the FCO Spillway 133