If a hydrograph is used, then it serves to establish the time scale. The user is encouraged to try different peak times for the storm tide to find the maximum discharge and velocity through the bridge with the given hydrograph. Ideally, when storage is not considered, the maximum tidal flow will occur half-way between high tide and low tide. There are an infinite number of combinations for combining tidal discharges and riverine discharges. The assumption that the peak tidal flow and the peak riverine flow occur simultaneously is a very conservative approach to tidal routing analysis. Such an event is likely to have a recurrence interval greater than the value used for either the riverine hydrograph or the tide hydrograph. The user is encouraged to consider the risk that such an event could occur (that is the joint probability of this combination) when establishing the relationship between the riverine hydrograph and the tidal storm hydrograph.
If a constant riverine (stream) discharge is used, the user can let the peak time be the default time value of 0, and input the information on the high tide elevation for time zero.