Wingwalls -- Retaining walls set at an angle to the head wall to further support the fill and direct the flow
of the water.
Crown -- Outside top of the culvert. When dealing with corrugated metal pipe culverts, the inside and
outside elevations of the culvert are assumed to be identical.
Invert -- Inside bottom of pipe.
Fill depth -- The depth of fill from the top of structure to the invert (inside bottom) of the culvert.
Cover -- The depth of fill from the top of structure to the crown outside top of the culvert.
Figure 5-1. Cross-section of culvert in place
PART A - THE THEORY OF CLOSED CHANNEL FLOW
The flow or discharge capacity (Q) of a culvert is the amount of water which the culvert will carry in a unit of
time, expressed in cfs. For a particular culvert, Q is controlled by one or more of the following factors:
The elevation of the culvert inlet.
The slope or hydraulic gradient (S) of the culvert.
The length (L) of the culvert.