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I’m having a senior moment. I can’t recall the Best Practice with regards to Tc segments through a subcatchment. I prefer to model catch basins, drain manholes and the piping using insignificant-storage ponds. But… should these pipe segments be included as Tc segments as well? Or does the fact that the ponds are included in the routing take care of the time?
As with a multitude of things we face in engineering, there are “many ways to skin the cat.” The typical workflow I have used in over 25 years of experience is this:
Pond level Hydrology & Hydraulics (H&H) is modeled using SCS methods. Most closed drainage systems are not specifically modeled and included in Tc paths. The exception would be drainage systems which connect ponds or are part of pond outfalls.
All other Closed Drainage systems are modeled using FWHA /Rational Methods analysis of flows, gutter spreads, inlet capture & bypass, and pipe capacity.