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Urban Storm Drain Design: Transverse Slope

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Presentation on theme: "Urban Storm Drain Design: Transverse Slope"— Presentation transcript:

1 Urban Storm Drain Design: Transverse Slope

2 Slope break Transverse slopes are in range of 2%-4%
(.02 ft/ft – 0.04ft/ft) Typical is 2% increasing to 3% after some distance depending on longitudinal slope. Slope breaks are normally accomplished at lane lines

3 Ponded width Ponded width computations will usually involve all “Z” values in the typical section. Z1 is usually the slope closest to the curb and gutter.

4 Ponded depth Ponded depth is the depth at the curb (or edge).
If at an inlet, the depth would be measured from the lip of the inlet.

5 Inlet placement to reduce width
Inlets are placed in low points Consider intersections Acceptable ponding widths

6 Inlet placement to reduce width
Ponding width

7 Inlet placement to reduce width
Partial capture with carryover

8 Inlet on grade LR Compute length of inlet for total interception
Subjective decision of actual length Estimate carryover LR

9 Inlet on grade Design guidance in HDM pp. 10-30 – 10-35.
Formula for estimating required length Need geometry Need desired flow (to capture) Calculate equivalent cross slope Inlet height used here Apply formula for required inlet length

10 Inlet on grade Value of carryover
Uses more of inlet open area – hence may be able to use shorter inlet (if there is compelling need)

11 Profile grade vs. inlet length
Inlet length is proportional to longitudinal slope As slope increases, required length increases Length for complete capture Longitudinal slope

12 Profile grade vs. inlet length
Inlet length is proportional to longitudinal slope As slope increases, required length increases


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