*Urban Drainage and Intersection DesignImage: http://www.dhi.dk/Consulting/WaterInTheCity

*Urban Street Design - DrainageDrainage 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

*The Stormwater SystemMinor system: Role collect stormwater and discharge to major system Design Storm 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 stuffIf fails, property damage or loss of life

*Intersection Drainage Design - DrivewaysAvoid 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

*Intersection Drainage Design - IntersectionsAvoid 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)

*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 Intersection Drainage Design - Intersections

*CalculationsGiven Q, find d (depth) and T (width) of flowUse Q=0.557(Z/n)S1/2 d8/3 where: S = longitudinal grade in ft/ftZ = reciprocal of the cross slope d = depth at the curb in ft. d = [n Q/.56Z S1/2]3/8See Iowa DOT Design Manual (excellent)

*Sources: Green Book and SUDAS

*Typical plan and profile for storm sewer

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*Source: SUDAShttp://www.iowasudas.org/documents/Ch2Sect5-05.pdf

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