General

Process models

This section allows you to select which of SWMM’s process models will be applied to the current project. As the GeoSWMM 2D focuses on flooding, you must turn on hydrology “Rainfall/Runoff” and hydraulics “Flow routing” options.  

ü  Routing method

• To simulate the 2D flood model, you must select Dynamic Wave routing option. This method solves the complete one-dimensional Saint Venant flow equations, continuity and momentum equations for conduits and a volume continuity at nodes, ensuring that most theoretically accurate results. Dynamic wave routing allows for pressurized flow in full flow conduits, accounts for flooding at nodes, and can represent channel storage, backwater, entrance/exit losses, flow reversal, and pressurized flow. It is ideal for systems with significant backwater effects and flow regulation via weirs and orifices. Note that this method requires smaller time steps, typically around thirty seconds or less, to maintain numerical stability.

Infiltration model

·       This option controls how the infiltration of rainfall into the upper soil zone of subcatchments is modeled. The choice of infiltration method often depends on the availability of soil parameters in the modeled area.

Miscellaneous

ü  Checking the “Allow Ponding” option will allow excess water to collect atop nodes and re-enter the system when conditions permit. For ponding to occur at a particular node, its Ponded Area attribute must have a a nonzero value. This option should be checked to ensure that no water is lost from the calculation and to determine flood water volume properly.