Pre-Modeling Communication: Hydraulic Model Considerations

HEC-RAS is a program commonly used to generate one-dimensional hydraulic models. (Image Source: Hydrologic Engineering Center, USACE)

• State the software selection and describe the limitations of the program as they apply to this project.
• Describe the hydraulic scenarios to be modeled and any scenario-specific assumptions that will be applied.
• Note the sources of information and describe the uncertainties or limitations of that information. Also identify data needs and how those gaps will be addressed.
• State whether a steady or unsteady flow condition will be modeled. Also state whether a one-dimensional, two-dimensional, or three-dimensional hydraulic model will be used. Justification should be provided for the selected approach based on project objectives and available data.
• Describe the anticipated model extent and boundary conditions. Also note how model boundaries will be evaluated to assess calculation independence at the location(s) of interest in the model.
• Describe the source of flow data (including base flows, design flows, and hydrographs) and energy loss coefficients.
• Describe the model geometry data including terrain data source and resolution as well as bridge, culvert, and other hydraulic structures within the wetted area of the model.
• Summarize information regarding dams, spillways, and reservoirs where reservoir routing will occur. This should include a description of reservoir routing methodology, initial reservoir levels, stage-storage-discharge curves, and assumed operation of gated spillways or outlet works. Information and assumptions regarding dam breach approach should also be provided if applicable.
• If a parametric sensitivity analysis is planned, describe the approach.
• Describe the model validation or calibration approach. If historic gage data are used for calibration, provide detailed descriptions of the available information.