The precipitation that falls on a catchment can only be converted into a flow to a sewer if the user specifies the following:

• Area to determine magnitude of available flow(For more information, see "Entering Area" .)
• Runoff method which consists of:
• • Loss method to determine the amount of available flow that actually runs off
  • Hydrograph method to determine the shape of the runoff hydrograph

The modified rational method does not explicitly have a loss method associated with it.