Abstract Submission: Sedimentation and river hydraulics (SRH) 2D and HEC-RAS 1D models were developed to perform hydraulic analysis along the Columbia River from River Mile (RM) 102.16 to 111.73 to support a complex bridge replacement project. The models were each selected to generate the specific outputs necessary to support the design advancement process, various project permitting needs (federal, state and local), and to provide agency reviewers and stakeholders with a conceptual estimate of potential hydraulic impacts. The discussion will focus on how the two models were each created to support specific tasks, while working in conjunction to provide a more robust and validated set of results. The 1D model was produced using USACE’s HEC-RAS, including HEC-RAS Mapper. The 1D model was developed to estimate the existing and proposed project conditions, water surface elevations, and velocities to evaluate the hydraulic impacts of a conceptual bridge design. The 1D model also served as the basis for the floodplain analysis, which required updating and evaluating against the FEMA effective data . The 2D model was developed to facilitate navigation simulations, design of bank protection, and scour calculations, outputs included water depths, velocities, and shear stresses. Flow split percentages generated in the 2D model were used as input data for the HEC-RAS 1D model to facilitate a range of flows. The discussion will highlight similarities and differences in surface representation, calibration approaches, and the driving factors for effective selection of modeling approaches and software for project applicability.
