The Culvert command lets you model the behaviour of a culvert
under various conditions of flow.
Because of the many variables involved, the process is largely
one of trial and error and MIDUSS does not suggest initial
feasible values for the design.
Culvert design can be carried out for either steady, (i.e. time
invariant) flow or for an inflow
hydrograph. When inflow is in the form of a hydrograph the
hydraulic design can be followed by
a routing process that shows the attenuation of the inflow
hydrograph caused by ponding that
occurs upstream of the embankment. In such cases the peak outflow from the barrel will be less
than the peak inflow and you can refine the barrel design for the
reduced flow if desired.
Your Culvert design can be preceded by a Channel design with
either a trapezoidal or
complex cross-section. When this is done the cross-sectional shape
of the channel is ‘inherited’ by
the culvert design and used to describe the flow cross-section
upstream of the culvert. If the
inflow is a flow hydrograph, a channel design may be followed by a
Channel routing process from
which the channel outflow forms the inflow to the culvert.
The culvert is assumed to be located below a sag point in a
highway embankment that will form
an overflow weir in the event that the barrel flow capacity is
sufficiently surcharged. Flow
separation between barrel and weir flow is assumed to be
recombined downstream of the barrel.
The cross-section of the barrel conduit may be a circular pipe, a
rectangular box, a horizontal or
vertical ellipse or a pipe arch. Multiple barrels may be used but
cross-section and other hydraulic
parameters are assumed to be the same for all barrels.