Existing roadway sheet flow and profile (HGL) calculation

[pinkpig]

Without using 2D modeling, what’s the best way to calculate an existing roadway sheet flow profile (HGL along roadway) under different return period storms? Suppose the roadway has subsurface storm sewer as well as roadside drainage ditches. Thanks.

 

[TerryScan]

FHWA HEC-22

https://www.fhwa.dot.gov/engineering/hydraulics/pubs/10009/10009.pdf

 

[gbam]

Not sure what you are asking. If you have channels/ditches paralleling a roadway one would typically use Manning's or HECRAS with XSECs cut perpendicular to the roadway; but this is not sheet flow. If you are looking for flow over the roadway then use the weir and approximate DS flow using Manning's with really large sections? Not sure if this helps; but thought I would try.