General Options

The General page in the Simulation Options setting contains the following items.

Process Models

This section allows the user to select which of SWMM’s process models will be applied to the current project. For example, a model that contained Aquifer and Groundwater elements could be run first with the groundwater computations turned on and then again with them turned off to see what effect this process had on the site’s hydrology. Note that a specific process model may be disabled if t no relevant items are present in the SWMM project. For example, if there are no Aquifers defined for the project, then the Groundwater option will appear in the unchecked and disabled state.

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Infiltration Model

This option controls how infiltration of rainfall into the upper soil zone of subcatchments is modeled. The choices are: 

1.     Horton

2.     Modified Horton

3.     Green-Ampt 

4.     Modified Green-Ampt

5.     Curve Number 

 

Changing this option will require re-entering values for the infiltration parameters in each subcatchment.

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Routing Model

This option determines which method is used to route flows through the conveyance system. The choices are:

1.     Steady Flow

2.     Kinematic Wave 

3.     Dynamic Wave 

 

Miscellaneous

In addition to the above simulation options, GeoSWMM enables the user to set some special considerations when processing the model simulation. These are optional choices for a user, and they have been provided under the Miscellaneous items. The choices are:

Allow Ponding: allows excess water to collect atop nodes and to be re-introduced into the system as conditions permit. In order for ponding to actually occur at a particular node, a non-zero value must be set to its Ponded Area attribute.

Report Control Actions: lists all discrete control actions taken by the Control Rules associated with a project (continuous modulated control actions are not listed). This option should only be used for short-term simulation.

Report Input Summary: enables listing and a summary of the project's input data.

Skip Steady Periods: checking this option will make the simulation use the most recently computed conveyance system flows during a steady state period instead of computing a new flow routing solution. A time step is considered to be in a steady state if the change in external inflows at each node is below 0.5 cfs and the relative difference between total system inflow and outflow is below 5%.

Minimum Conduit Slope: allows to set the minimum value allowed for a conduit's slope (%). If blank or zero (the default), then no minimum is imposed (although SWMM uses a lower limit on elevation drop of 0.001 ft (0.00035 m) when computing a conduit slope).