Urban Vegetated Roofs in the Southeastern US

1. Urban Vegetated Roofs in the Southeastern US 26th AWRC Conference Orange Beach, AL September 6th 2012 Jason Kirby, Katie Sheibley, Julie Price, Matt Winslett, Stephen Watts and Robert PetersUniversity of Alabama at Birmingham

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 urban water bodies. • Stormwater infrastructure is at capacity in many of our cities / communities. • Municipal expansion of sewers = $Billions • Urban flooding = $Billions • Due to increases in global population and rates of urbanization, the severity of environmental damage is escalating. • 2012 US: 0.30 Billion; 83% Urban • 2012 China: 1.34 Billion; 47% Urban • 2012 India: 1.23 Billion; 31% Urban (Unicef)

5. 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.)

6. Urban Research Environment: Birmingham, AL 35294

7. Urban Research Environment: Birmingham, AL 35294

8. UAB Vegetative Roof Research:History • 2006: Concept investigation • 2007- present: CB; thermal investigation • 2008 - present: Hulsey Center; 14,000 ft2 • concept application (20,000 sedum plants) • 2009 - present: Campbell Hall; vegetation selection • 2011 - present: BEC; runoff quantity • 2012 - present: BEC runoff quality AWRRI Funded

9. Research Objectives: • 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. • Evaluate runoff water quality during rainfall events (<5yr) • irrigated and non-irrigated conditions. • new installations and established vegetated roofs. • with respect to first-flush effects.

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 Only 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. 2011 -2012 RESEARCH RESULTS

14. Plant Selection: • With minimal drip irrigation the selected plants thrived…. • Price, J.G., S.A. Watts, A.N. Wright,R.W. Peters, and J.T. Kirby, 2011. “Irrigation Lowers Substrate Temperature and Enhances Survival of Plants on Green Roofs in the Southeastern United States”. HortTechnology, 21: 586-92.

15. Plant Selection: (Non Irrigated: Summer 2012)

16. 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, prior storm events,…

17. 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].

18. UAB BEC Experimental Roofs: • Strong CN improvement • Attenuated Volumes ~75% • Irrigated Avg. = 77.7 • Non-irrigated Avg. = 77.0

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

20. Water Quality Research: Ongoing 2012 Task 1. Retrofit existing UAB Greenroofs for Water Quality Analysis

21. Water Quality Research:Ongoing 2012 Task 2. Soil Substrate Assessment Green roof soil has been analyzed for mineral nutrients, including Ca, Mg, K, P, Cu, Fe, Mn, Zn, B, Al, Cd, Cr, Pb, Na, Ni, total C and total N using saturated extract at the Auburn Soil Testing Lab • Fresh Soil (preserved from original planting) • Aged 2yr Irrigated • Aged 2yr Non-irrigated • All Controls

22. Water Quality Research: Ongoing 2012 Task 3. Water Quality Analysis • First Flush / Storm Composite: • Nutrients (Nitrogen, phosphorus) • Heavy Metals (Cu, Zn, Cr, Pb, Cd) • (TS/TSS/TDS) • Alkalinity • Biological Oxygen Demand (BOD) • Chemical Oxygen Demand (COD) Grab: • pH • Dissolved Oxygen • Conductivity

23. Water Quality Research: Ongoing 2012

24. Conclusions: • Vegetated roofs are potentially viable for use as a stormwater control technology within urban areas of the southeastern United States. • The benefits and advantages of targeted greenroof research are many and need continued academic, industry, and funding support.

25. Future UAB Research: • Vegetated Roofs: • Augment soils with AAC(autoclaved aerated concrete) to enhance moisture availability and solar reflectance. • Evaluate interaction with rain gardens to potentially improve urban stormwater runoff quality. • Capture / evaluate larger design storms and their impact on effective curve numbers. • ….

26. 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 • “Experimental Investigation of Stormwater Runoff Quality Originating from Urban Vegetated Roofs” PI~Dr. Jason T. Kirby • UAB Facilities Management Department • Irrigation Water Technologies America, Tremco, and ITSaul Plants.

27. Questions???