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25 th AWRC Conference Orange Beach, AL September 9 th 2011

Runoff Mitigation from Urban Vegetated Roofs in the Southeastern US Jason Kirby, Katie Rigney, Julie Price, Matt Winslett, Ronald Sherrod, Stephen Watts and Robert Peters University of Alabama at Birmingham. 25 th AWRC Conference Orange Beach, AL September 9 th 2011 .

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25 th AWRC Conference Orange Beach, AL September 9 th 2011

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  1. Runoff Mitigation from Urban Vegetated Roofs in the Southeastern USJason Kirby, Katie Rigney, Julie Price, Matt Winslett, Ronald Sherrod, Stephen Watts and Robert PetersUniversity of Alabama at Birmingham 25th AWRC Conference Orange Beach, AL September 9th 2011

  2. Environmental Dilemma: • Stormwater runoff has been identified by the US EPA as a major source of pollution in urban and suburban streams, detrimentally impacting sensitive aquatic ecosystems in these watersheds. • Impervious cover reduces the hydrologic time of concentration and amplifies the volume of associated stormwater runoff.

  3. Shanghai Skyline (1990 to Present): • Explosive 20yr growth • Significant environmental pollution

  4. Why The Concern ? • Sediments, metals, oils / grease and general trash adversely impact our urban streams. (NPDES Permits) • Stormwater infrastructure is at capacity in many of our cities / communities. • Municipal expansion of sewers = $$$ • Urban flooding = $$$ • Due to increases in global population and rates of urbanization, the severity of environmental damage is escalating. • 2009 US: 0.30 Billion; 83% Urban • 2009 China: 1.33 Billion; 45% Urban • 2009 India: 1.15 Billion; 32% Urban

  5. An Urban Research Environment: Birmingham, AL 35294

  6. UAB Vegetative Roofs: • UAB is currently investigating extensive (shallow) vegetative roofs for their potential benefits to: • Decrease urban runoff and improve water quality • Building performance (insulation, cost, durability, etc.)

  7. An Urban Research Environment: Birmingham, AL 35294

  8. UAB Vegetative Roof Research:History • 2006: Concept investigation; two MSCE • 2007-present: Chemistry Building; thermal investigation • 2008 -present: Hulsey Center; 14,000 ft2 concept application (20,000 sedum plants) • 2009 -present: Campbell Hall; vegetation selection • 2010 -present: BEC; irrigation and runoff • 2011-present: Campbell Green house; soil amendments

  9. Research Objectives: (Presentation) • To expand our understanding of vegetated roofs in the Southeastern US and their role in reducing urban runoff: • Determine an optimal plant matrix for stormwater retention and peak flow reduction. • Evaluate the potential impact of different vegetated roofs on effective curve number (CN) values.

  10. UAB BEC Experimental Roofs: • Thirty mini-roof structures (4 ft tall x 12 ft long x 4 ft deep were constructed. The roof of each “building” is fitted with standard materials required for an extensive vegetated roof, including: waterproofing, insulation, drainage layers, filter fabric, and four inches of green roof soil.

  11. UAB BEC Experimental Roofs: • Mini-roofs were planted with the following scenarios (identical soil: 80% fines, 20% castings): • Monoculture Sedum album, a succulent plant; • Monoculture Boutelouacurtipendula, a bunchgrass; • Monoculture Phlox bifida, a forb; • A mixture of the 3 species above, planted in a randomized arrangements • Soil and Conventional Roof Controls

  12. UAB BEC Experimental Roofs: • Instrumentation: • Soil Moisture / Temperature (Decagon Devices) • Capillary Drip Irrigation (KISSS USA) • Surface and Subsurface flow (Campbell Scientific) • Ambient Weather Conditions (Davis) • Rainfall duration / intensity, temp, wind speed, heat index, solar intensity,

  13. UAB BEC Experimental Roofs: • Previous studies indicate that a vegetated roof can effectively lower the curve number of a conventional roof from 98 to 82-90*. • Lowering runoff volume (attenuated on rooftop) • Increasing runoff lag (improve Tc) • However, the vegetated roof performance is closely associated with: • Design Storm (<10 yrs) • Vegetation selection and soil conditions • Physical coverage, roof slope, ambient conditions…

  14. UAB BEC Experimental Roofs: • Monitored Storm Events (February – June 2011):

  15. UAB BEC Experimental Roofs: Methodology utilized to evaluate the effective curve number for the various vegetated roof treatment scenarios was consistent with previous efforts [Carter and Rasmussen, 2008; Prowell, 2006; Getter et al., 2007; and Stumme, 2008].

  16. UAB BEC Experimental Roofs: • Preliminary • UAB Results: • Strong CN improvement • Consistent with literature • Attenuated Volumes ~75% • Irrigated Avg. = 77.7 • Non-irrigated Avg. = 77.0

  17. UAB BEC Experimental Roofs: Based on UAB data currently available, all vegetated roofs are statistically identical yet measurably better than conventional roofs.

  18. UAB BEC Experimental Roofs: • We anticipate that differences in the flow reduction and retention of stormwater of unique vegetated roof scenarios may not be completely evident until after the plants have been in place for at least a full growing season. • By this time, the plants will have had time to more fully envelop the soil surface and develop dense root masses (dependent upon inherent root morphology and sufficient soil moisture).

  19. Conclusions: • NRCS curve number data across the various vegetated roof applications are similar with those observed in published research outside the investigational area. • Vegetated roofs are potentially viable for use as a stormwater control technology within urban areas of the southeastern United States.

  20. Future UAB Research: • Vegetated Roofs: • Plant selection (ET, survival, irrigation, age,…) • Augment soils with AAC(autoclaved aerated concrete)to enhance moisture availability and solar reflectance. • Water quality of vegetative roof runoff. • Evaluate interaction with rain gardens to potentially improve urban stormwater runoff quality. • Capture / evaluate larger design storms and their impact on effective curve numbers. • ….

  21. Acknowledgements: • Research funding was provided by the U.S. Department of Interior, through the Alabama Water Resources Research Institute. • Performed in correlation with: “Experimental Investigation of Runoff Mitigation from Vegetated Roofs”. PI~Dr. Jason T. Kirby • UAB Facilities Management Department • Irrigation Water Technologies America, Tremco, and ITSaul Plants.

  22. Questions???

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