Geometry of Circular Culverts
The following equations are used in FishXing to calculate the wetted perimeter, top width, and cross-sectional area of the flow through a circular culvert that is not-embedded.
Definition sketch for Geometry of a circular culvert:
Equations Used in the Calculation of Circular Culvert Geometry:
d = Diameter of culvert
r = Radius of culvert
y = Depth of water in culvert
P = Wetted Perimeter of water on the bottom
T = Top width of water surface
A = Cross sectional area of flow
Rh = Hydraulic radius
Another common method for determining culvert geometries involves the use of a table of geometric ratios developed for a partially full pipe that is not embedded. If the depth of flow is known, a ratio of depth to diameter can be used to calculate the area of flow, wetted perimeter and hydraulic radius.