 # Channel travel time (Tc) to compute intensity

 Product(s): StormCAD, SewerGEMS, CivilStorm Version(s): 08.11.XX.XX and 10.00.00.XX Area: Calculations

# Problem

Does StormCAD compute the travel time (ie. Tc) in open channels and add it the system travel time to get the correct intensity?

# Solution

Yes, StormCAD does compute the travel time in open channels and adds it to the system travel time to get the correct intensity.

For example, look at the following images.  At the cross section:

System flow time = (catchment flow time) + (conduit flow time)
System flow time = 10.000 min + 0.290 min
System flow time = 10.290 min
System intensity = 3.407 in/hr

At the outfall:

System flow time = (catchment flow time) + (conduit flow time) + (channel flow time)
System flow time = 10.000 min + 0.290 min + 5.000 min
System flow time = 15.290 min
System intensity = 2.683 in/hr

The channel element does not contain a property that reports the travel time through the channel. This field can be added by creating a formula user data extension. The process of doing this is explained in this article, however the following image gives a general idea of how it would be configured. Enhancement #710699 was submitted to:
1. Add "System Flow Time" and "System Intensity" fields to cross section element properties.
2. Add the "Time (Channel Flow)" field to the channel element properties>