Calculation Options

On the final page of the wizard, you can specify some calculation options that apply to the scenario.

The default active solver is the Explicit (SWMM Solvers). The default routing time step is 5 seconds along with a default output increment of 3 minutes or 0.05 hours.

The simulation duration multiplier is a factor used to calculate the simulation duration of the scenario. This factor is multiplied by the duration. The default is 2. If the duration is 24 hours, then the simulation duration is calculated as 48 hours. This allows for the entire storm to run and to account for all rainfall during that simulation.

If you select the Explicit (SWMM Solvers), you can also specify whether or not to use the Bentley transition equation by checking that option.

The minimum time interval determines if a user defined time interval is used when generating storm events using dimensionless time curves. This is especially useful for shorter durations. The default is 1 minute. If the option is off, the calculated increment is used. If the option is on, the entered time interval is used for all generated storm events where the calculated time interval is less than the entered value.

The "Use Bentley Transition Equation" option applies only to the SWMM Solver and determines if the custom Bentley Transition Equation is used when using the SWMM solver.

When you click finish the creation of the scenarios, alternatives, calculation options and storm events is started. A preview of how many scenarios and storm events created is shown on page 3.

There is a one-to-one relationship between the scenario and rainfall runoff alternative as each scenario represents a different storm event.