How are the coefficients derived for the HEC-22 structure loss method?

Product(s): StormCAD, CivilStorm, SewerGEMS
Version(s): V8i, CONNECT Edition
Area: Modeling


How are the coefficients derived in StormCAD when using the HEC-22 structure loss method?

Problem ID#: 58019


The `HEC-22' structure loss method used in StormCAD (and the GVF-Rational solver in CivilStorm and SewerGEMS) is based on the FHWA's Urban Drainage Design Manual, Hydraulic Engineering Circular No. 22 (HEC-22) energy-loss methodology. This method computes an adjusted headloss coefficient by multiplying the initial headloss coefficient by correction factors for diameter, flow depth, relative flow, plunging flow and benching (Structure Headloss). This adjusted headloss coefficient is then multiplied by the velocity head in the outlet pipe to determine the total junction headloss. This is the method outlined in the current edition of the HEC-22 document (HEC-22, Second Edition, August 2001).

Note that is more recent versions, the Third Edition HEC-22 structure loss method is also available.

See Also

HEC-22 2nd edition energy loss calculations with the Implicit solver

What are the differences between HEC-22 3rd edition and HEC-22 2nd edition?

HEC-22 "junction loss" (equation 7-10 of HEC-22)

Junction minor headloss coefficients for standard method