Hydraulic Design of Highway Culverts - DOT On-Line Publications

1. Skewed Barrels. The alignment of a culvert barrel with respect to the roadway centerline is
referred to as the barrel skew angle. A culvert aligned normal to the roadway centerline has a
zero barrel skew angle. For any other alignment, the barrel skew angle is the angle from a line
normal to the highway to the culvert centerline. Directions (right or left) must accompany the
barrel skew angle (Figure VI-17).
Figure VI-17--Barrel Skew Angle
It is common design practice to place the culvert barrel on an alignment and grade that
conforms to the existing stream channel. The barrel skew is established from the stream
location and the proposed or existing roadway plan. The advantages of this design practice
include a reduction of entrance loss, equal depths of scour at the footings, less sedimentation in
multibarrel culverts, and less excavation. A disadvantage of this design procedure is that the
inlet may be skewed with respect to the culvert barrel and the culvert will be longer
It is not always prudent to allow the existing stream bed alignment to dictate the barrel skew
angle. Modifications to reduce the barrel skew angle and shorten the culvert barrel may
produce a more economical solution in some situations. Chapter II contains a discussion of
alternative culvert location procedures as related to culvert length.
2. Skewed Inlets. The angle from the culvert face to a line normal to the culvert barrel is
referred to as the inlet skew angle (Figure VI-18). The inlet skew angle varies from 0-degrees to
a practical maximum of about 45-degrees. The upper limit is dictated by the difficulty in
transitioning the flow from the stream into the culvert.
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