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[8] USACE Hydrologic Engineering Center. Reservoir System Simulation (HEC-ResSim), 2013, Version 3.1, Davis, CA. [9] USACE Hydrologic Engineering Center. Hydrologic Modeling System (HEC-HMS), 2016, Version 4.2, Davis, CA. [10] USACE. Hydraulic design of spillways, Engineering Manual 1110-2-1603, Washington, D.C., 1990. [11] USBR. Chapter 4: “General spillway design considerations,” Design Standards No. 14, Appurtenant structures for dams (spillways and outlet works) design standards, August 2014. [12] FALVEY, H.T. Cavitation in chutes and spillways, Water Resources Technical Publications, EM 42, Bureau of Reclamation, Department of Interior, 1990, Denver, CO. [13] WILHELMS, S.C., GULLIVER, J.S. “Bubble and waves descriptions of self-aerated spillway flow,” J. Hyd. Res., 2005, 43(5) 522-531. [14] YOUNGERMAN, J.M. “Volume II, Design Notes,” Oroville Dam spillway, Final design, DWR, June 1965. [15] FRANCE, J.W., et al. Independent Forensic Team Report: Oroville Dam spillway incident, United States Society on Dams, January 2018. SUMMARY During the Oroville Dam Spillway Incident, hydrologic and hydraulic engineering and reservoir operation analyses provided information to support decision making by DWR management. Reservoir inflow forecasts were made almost continuously by DWR staff and the NWS, using conceptual models of Feather River Basin watershed hydrology. Reservoir behavior and operation with various operation and potential failure scenarios were simulated to predict future pool elevations and timing of potential Emergency Spillway discharge. Inundation that could result from potential failure was predicted and displayed with maps included in Oroville Dam’s Emergency Action Plan, which emergency and incident command teams consulted. These maps were augmented with situation-specific maps prepared in near real time as the incident progressed. Additional hydraulic analyses provided DWR managers with information about potential flow paths along the hill slope downstream of the Emergency Spillway, and with estimates of debris and sediment loads in the Feather River downstream. Challenges for analysis during the event in February 2017 included: (1) the need for almost immediate turnaround to provide information critical for decision 142