Oroville Dam Spillway Emergency Assessment and Rehabilitation
At 770 ft, Oroville is the tallest dam in the United States. Following the partial failure of its two spillways in February 2017 that led to evacuation orders for 188,000 residents living downstream of the dam, the California Department of Water Resources (DWR) launched one of the largest dam safety and emergency repair efforts in the United States, whose total cost eventually reached $1.1 billion. NHC provided specialized hydraulic engineering support as part of a multidisciplinary team that included DWR, regulatory agencies, and engineering consultants responsible for assessing damage and developing repair strategies.
California Department of Water Resources
Water Infrastructure
Northern California
During the emergency response, NHC developed advanced Computational Fluid Dynamics (CFD) models using FLOW-3D to assess existing conditions, evaluate repair concepts, and analyse hydraulic performance across a wide range of operating scenarios. Given the emergency nature of the work, the large size of the spillway, and the need to produce results quickly, NHC performed multiple around the clock CFD simulations using high-performance computers, equivalent to several years of computer processor time. These hydraulic analyses provided critical information on spillway performance and downstream hydraulic conditions, guiding immediate risk management decisions and supporting the development of repair alternatives.
NHC participated in technical advisory committee meetings and worked closely with project stakeholders to develop hydraulic modelling approaches for both the main flood control spillway and the emergency spillway.
For the flood control spillway, NHC’s modelling supported the evaluation of interim and permanent repair options, including the assessment of flow trajectories, energy dissipation, and discharge capacity. Additional analyses helped refine hydraulic design parameters and address technical challenges identified during the rehabilitation process.
NHC also led CFD modelling efforts for the emergency spillway, providing detailed information on water depths, velocities, shear stresses, and downstream flow conditions. These results informed the design of erosion protection measures, energy dissipation features, and other critical infrastructure improvements required to enhance spillway safety and performance.
Provided critical hydraulic analyses that informed the emergency repair and long-term rehabilitation of the Oroville Dam spillways, helping improve dam safety, reduce flood risk, and strengthen the resilience of critical water infrastructure serving millions of Californians.
