HY8:Increased Resistance in Culverts

Increased Resistance in Box Culverts

The input variables required for this calculation are the following:

• h/r_i—Ratio of roughness element height divided by hydraulic radius taken about the top of the roughness element.
• Height of the roughened section (h)

Increased Resistance in Circular Culverts

The input variables required for this calculation is the following:

• L/D_i — Ratio of roughness element spacing divided by the diameter of the culvert opening at the roughness element. (Range = .05 to 1.5)
• h/D_i — Ratio of roughness element height divided by the diameter of the culvert opening at the roughness element. (Range = .005 to .1).
• L_r/P_i — Ratio of the roughness length to inside perimeter (Range = 0.0 to 1.0)
• Diameter of roughened section (Opening, D_i)

The following figure shows the flow regimes and variables for an increased resistance energy dissipator implemented in a circular culvert.

Variables from the figure

• L — Length from beginning of one roughness element to the beginning of the next roughness element.
• h — height of roughness element
• D_i — diameter of roughened section (opening)