16 06-2010 wgrc-jwb_day2_stream_f_9.20_blog

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16 06-2010 wgrc-jwb_day2_stream_f_9.20_blog

  1. 1. Modelling a Green Roof and the Benefits to Storm Water Management<br />James Berryman <br />16th September 2010<br />
  2. 2. Introduction<br />Micro Drainage develop the industry-standard drainage design software in the UK and Ireland.<br />Its WinDes® drainage design software is relied upon by engineers around the world, with over 14,000 software modules currently in use globally. <br />WinDes allows engineers to design drainage solutions that meet the evolving challenges of flood management, environmental legislation, climate change and sustainability.<br />
  3. 3. Storm Water Management?<br />Established benefits of Green Roofs<br /><ul><li>Amenity space
  4. 4. Urban heat sink
  5. 5. Aesthetic
  6. 6. Enhanced biodiversity
  7. 7. Improved insulation
  8. 8. Pollutant removal </li></ul>Final validation – Storm Water Management<br />
  9. 9. Overcoming the Sceptics <br />The What Ifs?<br />Fair tests<br />Drainage Standards<br />Single storms (no tests for continuous analysis/Antecedent Conditions)<br />New systems, no allowance for :<br />FOG <br />Sediment <br />Root ingress <br />Blockages (both internally and at inlets)<br />Deformation<br />
  10. 10. Specification<br />Static Volumes v Real Time Analysis <br />Pragmatic approach <br /> Two key variables to generate a runoff model <br />Roof Area<br />Substrate Depth<br />
  11. 11. University of Sheffield : Field Test<br /><ul><li>Virginia Stovin selected the most suitable modelling approach based on reviews of existing research and test rig results</li></ul> 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<br />(1 x 3 m, standard Alumasc extensive sedum configuration on ~105 mm substrate + drainage layer).<br />
  12. 12. Two Forms of Storage<br />Interception (Depression) Storage<br />Depth of water that is retained in the roof (only lost through evapo-transpiration)<br />Attenuation (Lag) Storage <br />Conceptually equivalent to a unit hydrograph for the vertical flow through the substrate, the drainage layers and into the storm water network<br />It was recognised that the total storage will vary with the Antecedent Dry Weather Period (ADWP)<br />
  13. 13. Interception (Depression) Storage<br />Field tests and other academic research (Pallaet al. 2008, Stovin et al. 2007, Denardoet al. 2004) indicated:<br />That the retention to be expected after 2 days ADWP would provide a reasonably conservative perspective.<br />An Interception value of 5% of substrate depth would be a reasonable average for an ADWP of 2 days. <br />
  14. 14. Interception (Depression) Storage Applied<br />1ha Green Roof with 100mm of soil substrate applying a depression storage of 5% <br />This will result in the first 5mm of rainfall being held in the roof<br />Equating to 50m³ of storage<br />Continuous Analysis and evapo-transpiration <br />To scale<br />
  15. 15. Attenuation (Lag) Storage <br />Three Time Area Diagram (TAD) options were considered:<br />Time Area Diagram 0-4 minute entry<br />“Unit Hydrograph” (time to peak of 32 mins and a time base of 90 mins)<br />Exponential<br />
  16. 16. Calibration and Validation: i<br />
  17. 17. Calibration and Validation: ii<br />
  18. 18. Calibration and Validation: iii<br />
  19. 19. Exponential Method Incorporated into WinDes<br />A = factor required to scale the curve to provide the correct total catchment area<br />e = exponential<br />k = the decay coefficiency<br />t = the time in minutes <br />
  20. 20. Summary: Benefits for Storm Water Management?<br />Consider a 2 ha warehouse roof discharging to storage tank. <br />If a Green Roof is used the volume of storage reduces from 450m³ to 300m³<br />To scale<br />
  21. 21. Further Research<br />Future scope to calibrate the method:<br />Varying roof construction materials /techniques<br />More locations, slopes etc<br />Increased/reduced lag affect?<br />El Struthio<br />
  22. 22. Contact Information<br />James Berryman<br />Tel: 01635 582555<br />james.berryman@microdrainage.co.uk<br />Micro Drainage Ltd<br />Jacobs Well<br />West Street<br />Newbury<br />Berkshire<br />RG14 1BD<br />

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