Term Project Presentation CE 394K.2 Hydrology Presented by Chelsea Cohen Thursday, April 24, 2008

 Low Impact Development (LID) Technique  Mimic natural landscape  Open, shallow channels  Slow Runoff  Lower Velocities  Promote Infiltration  Filter Runoff  Trapezoidal or Parabolic Shape  Long, narrow, vegetated channels

 Model 25-yr and 100-yr design storms  Flood Control  Decentralized vs. Centralized System  Vegetated Swale vs. Detention Pond  Minimize Downstream Flow Off-Site  Conveyance  Contrast to Traditional Curb and Gutter  Aesthetic Appeal in Community

 Seattle Street Edge Alternatives (SEA)  Pilot project along residential street  Wisconsin DOT Technical Standard  California Storm Water BMP Handbook  San Francisco Drainage Calculations  City of Austin Drainage Criteria Manual

 Synthetic Storm  SCS Type III Rainfall Distribution  25-yr, 24-hr, 7.63in  100-yr, 24-hr, 10.18in

 Six ¼ -acre lots in series  2% Slope  Infiltration: SCS Runoff Curve Number  Assumed Type C Soil for moderately fine to fine soils  Pre-development: CN=74 ▪ Open space, Good Condition, Grass cover >75%  Post-development: CN=83 ▪ Residential, ¼ acre, 38% impervious

 Longitudinal Slope Range: 0.5%-4%  1% Vegetated Swale Slope  Side Slope 3H:1V or flatter  Swale Bottom 2 to 8-ft  5-ft Bottom  25-ft Width  116-ft Length  Dense Grass Cover  n=0.25 3H:1V 25’ 5’

 Connect vegetated swales with culverts  Sizes: 6” and 10” PVC pipes  0.5% Pipe Slope

 Safety Barrier between pedestrians and motorists

 EPA’s Storm Water Management Model (SWMM)  Rainfall-Runoff simulation model used for single event or long-term (continuous)  Simulation of Runoff quantity and quality from primarily urban areas  Iterative Process

 Design Iteration between Swale Size, Pipe Size and Storm Capacity 100-yr 25-yr

 Infiltration: 13-17% Total Precipitation (in) Total Infiltration (in) Total Runoff (in) 25-yr %83% 100-yr %87%  Post-Development Flow less than Pre-Development Flow  Provide Detention Storage in Swales  No increase in peak flow as a result of development Outfall Peak Flow (cfs) Pre-DevelopPost-DevelopDifference 25-yr yr

 Low swale velocity to prevent scour and promote infiltration Max Swale Depth (ft) Available Depth (ft) Freeboard (in) Swale1Swale2Swale3 25-yr yr Maximum Velocity (ft/s) 25-yr100-yr Swale Swale Swale30.43 Pipe Pipe Pipe  Swales do NOT over top for 25-yr or 100-yr storms

 Design the ROW to be beautiful as well as useful  Neighborhood Enjoyment and Care  Common destination for neighborhood residents  Add native vegetation  Seattle Street Edge Alternative (SEA) Project  Reduced total volume of storm water flow leaving the street by 99%

 Water Quality Improvement  Cost Benefit  Compare to Curb and Gutter System  Application to Entire Neighborhoods

 Management of Rainfall  Filter and Slow the Flow of Storm Water  Increase safety if convey 100-yr storm in swale and not roadway  Cost Effective and Aesthetically Pleasing  Responsible Design  Environmental Benefits  Methods to minimize developmental effects  Attempt to mimic natural landscape prior to development