Subcritical Flow and Steep Slope

The procedure for subcritical flow (d > d
c
) but steep slope (d
c
 > d
u
) is similar with the following exceptions:
  • Choose a decrement in depth, δd = negative.
  • If the depth, d, reaches critical depth before the inlet of the culvert is reached, the headwater is under inlet control (
    Headwater Under Inlet Control
    ) and a
    hydraulic jump
    may occur in the culvert barrel (refer to the following subsection for discussion of the hydraulic jump in culverts).
  • If the depth at the inlet is higher than critical depth, determine the outlet control head using Equation 8-15 as discussed in the
    Energy Balance at Inlet
    subsection. A hydraulic jump may occur within the culvert.