TROY

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GEM 4409HydrologyFall 2005

• TROY
• UNIVERSITY

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Storm Recurrence Intervals for Use in Highway
Design
Item Return Frequency Bridges 50 yrs or
flood of record (but check to see if local
flood ordinance rules), 25 yrs for county
structures, or sometimes lower depending upon
the type of facility Culverts 50 yrs or
flood of record (but check to see if local
flood ordinance rules) Cross Drain Pipe 50
yrs Storm Sewers Inlets 10 yrs (but 50 yrs in
sags) Median Flume 50 yrs Lateral Flume 10
yrs
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Intensity-Duration Curve for Huntsville
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Intensity-Duration Curve for Birmingham
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Intensity-Duration Curve for Montgomery
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Intensity-Duration Curve for Mobile
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Composite (Weighted) Runoff Coefficient