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16 06-2010 wgrc-jwb_day2_stream_f_9.20_blog

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  • But very popular in London – technical guidance available.
  • Transcript

    • 1. Modelling a Green Roof and the Benefits to Storm Water Management
      James Berryman
      16th September 2010
    • 2. Introduction
      Micro Drainage develop the industry-standard drainage design software in the UK and Ireland.
      Its WinDes® drainage design software is relied upon by engineers around the world, with over 14,000 software modules currently in use globally. 
      WinDes allows engineers to design drainage solutions that meet the evolving challenges of flood management, environmental legislation, climate change and sustainability.
    • 3. Storm Water Management?
      Established benefits of Green Roofs
      • Amenity space
      • 4. Urban heat sink
      • 5. Aesthetic
      • 6. Enhanced biodiversity
      • 7. Improved insulation
      • 8. Pollutant removal
      Final validation – Storm Water Management
    • 9. Overcoming the Sceptics
      The What Ifs?
      Fair tests
      Drainage Standards
      Single storms (no tests for continuous analysis/Antecedent Conditions)
      New systems, no allowance for :
      FOG
      Sediment
      Root ingress
      Blockages (both internally and at inlets)
      Deformation
    • 10. Specification
      Static Volumes v Real Time Analysis
      Pragmatic approach
      Two key variables to generate a runoff model
      Roof Area
      Substrate Depth
    • 11. University of Sheffield : Field Test
      • Virginia Stovin selected the most suitable modelling approach based on reviews of existing research and test rig results
      Rainfall/runoff data obtained from the University of Sheffield’s Green Roof test rig was compared with model outputs tested and calibrated using in WinDes
      (1 x 3 m, standard Alumasc extensive sedum configuration on ~105 mm substrate + drainage layer).
    • 12. Two Forms of Storage
      Interception (Depression) Storage
      Depth of water that is retained in the roof (only lost through evapo-transpiration)
      Attenuation (Lag) Storage
      Conceptually equivalent to a unit hydrograph for the vertical flow through the substrate, the drainage layers and into the storm water network
      It was recognised that the total storage will vary with the Antecedent Dry Weather Period (ADWP)
    • 13. Interception (Depression) Storage
      Field tests and other academic research (Pallaet al. 2008, Stovin et al. 2007, Denardoet al. 2004) indicated:
      That the retention to be expected after 2 days ADWP would provide a reasonably conservative perspective.
      An Interception value of 5% of substrate depth would be a reasonable average for an ADWP of 2 days.
    • 14. Interception (Depression) Storage Applied
      1ha Green Roof with 100mm of soil substrate applying a depression storage of 5%
      This will result in the first 5mm of rainfall being held in the roof
      Equating to 50m³ of storage
      Continuous Analysis and evapo-transpiration
      To scale
    • 15. Attenuation (Lag) Storage
      Three Time Area Diagram (TAD) options were considered:
      Time Area Diagram 0-4 minute entry
      “Unit Hydrograph” (time to peak of 32 mins and a time base of 90 mins)
      Exponential
    • 16. Calibration and Validation: i
    • 17. Calibration and Validation: ii
    • 18. Calibration and Validation: iii
    • 19. Exponential Method Incorporated into WinDes
      A = factor required to scale the curve to provide the correct total catchment area
      e = exponential
      k = the decay coefficiency
      t = the time in minutes
    • 20. Summary: Benefits for Storm Water Management?
      Consider a 2 ha warehouse roof discharging to storage tank.
      If a Green Roof is used the volume of storage reduces from 450m³ to 300m³
      To scale
    • 21. Further Research
      Future scope to calibrate the method:
      Varying roof construction materials /techniques
      More locations, slopes etc
      Increased/reduced lag affect?
      El Struthio
    • 22. Contact Information
      James Berryman
      Tel: 01635 582555
      james.berryman@microdrainage.co.uk
      Micro Drainage Ltd
      Jacobs Well
      West Street
      Newbury
      Berkshire
      RG14 1BD