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Urban Street Drainage Design - Safety, Convenience, and Stormwater Transport

Learn about the importance of urban street drainage systems in preserving safety, convenience, and managing stormwater transport efficiently. Explore the roles of minor and major stormwater systems, intersection drainage design, and calculations for flow depth and width.

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Urban Street Drainage Design - Safety, Convenience, and Stormwater Transport

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  1. Urban Drainage and Intersection Design CE 453 Lecture 27 Image: http://www.dhi.dk/Consulting/WaterInTheCity

  2. Urban Street Design - Drainage • Drainage is a secondary function of an urban street system • Runoff in areas is actually brought to the street and the gutter (versus water either being intercepted or brought to the ditch in rural areas) • Goals with Drainage on Street • Preserve safety and convenience of traveling public • Provide economical means of stormwater transport • Prevent water from leaving street system except where appropriate

  3. The Stormwater System • Minor system: • Role – collect stormwater and discharge to major system • Design Storm (return period) – 2 to 10 years typically (some use 25-year) • Use inlets and conduits (small stuff - most of the system) • Major system: • Role – carry stormwater from minor system to natural watercourses • Design storm – typically 100-year • Use culverts, bridges, retention basins (detention basins?) – big stuff • If fails, property damage or loss of life

  4. Intersection Drainage Design - Driveways • Avoid changes in longitudinal drainage due to driveways (ponding, etc. result) • Prevent water entering driveway by: • High point of drive should exceed maximum inside curb flow (top of curb for arterials/collectors and 0.1 m over curb for locals) • Contour land to flow into roadway

  5. Intersection Drainage Design - Intersections • Avoid ponding on approaches – use minimum grades, and avoid sag immediately before intersections (Hazel and 4th Street) • Locate inlets upstream of intersections (limits flow in intersection)

  6. Intersection Drainage Design - Intersections • Consider impact on drainage due to intersection cross slope adjustments (for smooth travel) – alternatives • Adjust minor street only (for local/collector and collector/arterial) • Adjust gutter line of both streets (only appropriate if intersection area is small – local/collector) • Adjust both centerlines but maintain cross section of both – generally avoid

  7. Calculations Given Q, find d (depth) and T (width) of flow Use Q=0.557(Z/n)S1/2 d8/3 where: S = longitudinal grade in ft/ft (not percent!) Z = reciprocal of the cross slope d = depth at the curb in ft. d = [n Q/.56Z S1/2]3/8 See Iowa DOT Design Manual (excellent)

  8. Sources: Green Book and SUDAS

  9. Typical plan and profile for storm sewer

  10. nQ

  11. Source: SUDAS

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