7.7.2 Final Hydraulic Design
The initial hydraulic design is performed during preliminary engineering (see
). During final design, refinement of the hydraulic design is needed to incorporate final roadway alignments and profiles into the design. The design storm frequency should be verified and all allowable velocities, allowable backwater/headwater, FEMA rules and regulations, National Flood Insurance Program (NFIP) requirements along with any other local or state agency requirements should be confirmed.
Coordinate with the local FEMA FPA early if applicable. The FPA can advise which base model to use and how much, if any, increase in backwater will be allowed. The FPA may also provide a copy of the original model or help locate one. It is advised to work closely with the FPA throughout the project.
Drainage design requires continuous coordination with roadway design activities.
Hydraulic design may result in the need for drainage easements in areas not already owned by or classified as waters of the State. In such instances, this task will have direct input into reviewing and obtaining additional ROW, access control, and easement requirements.