Capacity should be determined by inflow hydrographs

The computation of an inflow hydrograph is a function of the watershed characteristics, while an outflow hydrograph is both function of inflow and dam design, including reservoir characteristics, dam height, spillway characteristics, and gate(s) operating procedures. The setting of SDF design based on the outcome of that design is circular logic.

The owner’s engineer must develop PMF hydrographs for 6-, 12-, and 24-hour durations. The hydrograph that creates the largest peak outflow inflow is to be

used to determine capacity for nonfailure and failure analysis.