The development of any hydraulic model requires an accurate representation of the terrain data and the hydrologic inputs used as boundary conditions. Additionally, appropriate model parameters for terrain roughness and hydraulic structures must be estimated and then calibrated in order to have confidence in the model results. As these guidelines are focused on the development and use of unsteady flow models for dam break studies, discussions of basic data requirements, hydraulic parameter estimates, and model calibration/validation are not discussed. The HEC-RAS User's Manuals (HEC, 2020) contain information describing model input, data requirements, parameter estimation, and model calibration.

This section of the guidelines presents hydraulic modeling aspects that are unique to performing a dam break analysis. Topics include: inflow flood routing through a reservoir; estimating dam breach parameters; recommended approach; example application; and downstream routing/modeling issues.