Using Native Plant Communities as a Template for Green Roof Design

Doug Daley, P.E.Environmental Resources Engineering

SUNY College of Environmental Science and Forestry Syracuse, NY

Annual Meeting of the American Ecological Engineering Society June7-9, 2012

Summary

• Native plant communities are used as the basis for a Proof-of-Concept design approach

• Rooftop growing conditions at SUNY ESF Gateway Building will emulate dune and alvar communities found along the eastern shore of Lake Ontario

• Rooftop system will meet hydrologic performance requirements, support efforts to conserve unique ecological resources, and educate ESF’s broad community, including parents, students, Board, SUNY, municipal officials, designers,…

Green Roof Design in NY

• NYS Stormwater Management Design Manual: Green Roof (Chapters 4/5)

• Runoff reduction by storage and ET

Design Components - Functional

• Structural support• Waterproof barrier• Drainage layer (soil) supports vegetation, no

clay, porosity > 15%• Geosynthetic filter fabrics to prevent clogging• Plants with tolerance for regional climate,

harsh rooftop conditions and shallow rooting depth (e.g. alpine, arid)

Role of Vegetation

• Evapotranspiration• Vegetation on extensive roof captures about

10% of storm event (Michigan State, VanWoert, et al, 2005, JEQ, 34(3): 1036-1044)

• Medium captures about 50%• Other values

– Aesthetic– Habitat– Conservation

Green Roof Classes

• Intensive– Wide variety of plant species, including shrubs and trees,

greater diversity of choice– Deeper substrate >4” to 6”– Park-like and accessible

• Extensive– Shallow soil (<=4”)– Herbs, mosses, grasses, sedums (NYSDEC)– “Low” maintenance – 2 visits/year to remove “invasives”

• Native vegetation is recommended (NYSDEC)

SUNY ESF Gateway Building

Great Lakes Sand Dunes

• Growing conditions include extreme temperatures, strong winds, shifting sands

American beachgrass, Ammophila breviligulata http://www.seagrant.sunysb.edu/glhabitat/PDFS/ELODWAFactSheetDunePlants.pdf

Endangered plant species found there:

• Champlain beachgrass (Ammophila breviligulata), • rough avens (Geum laciniatum),• woodland bluegrass (Poa sylvestris), • marsh horsetail (Equisetum palustre), • large twayblade (Liparis liliifolia), • livid sedge (Carex livida), • giant pine drops (Pterospora andromedea) • sand dune willow (Salix cordata).

Alvar Barrens

• Prairie-like barrens– Flat, thin- to no-soiled, rocky (limestone bedrock)– Grasslands, limestone woodlands, cedar forests,

pavement barrens– Adapted to extreme conditions:

• Shallow soil, regular spring flooding, summer drought

• Local Nature Conservancy efforts at Chaumont Barrens Preserve, Jefferson County– Extend through Michigan

http://www.epa.gov/ecopage/shore/lakeont.html

Alvar Pavement Barrens

Plenty of Options for Color and TextureSelected Alvar Species

Agropyron trachycaulum – slender wheatgrass Aquilegia canadensis – wild columbine Artemisa campestris var. caudata – tall wormwood Aster ciliolatus – aster Bromus kalmii – brome grass Carex eburnea – ebony sedge Carex granularis – sedge Carex vulpinoidea – brown fox sedge Danthonia spicata – poverty grass Deschampsia cespitosa – tufted hairgrass Fragaria virginiana –wild strawberry Geum triflorum – prairie smokeJuniperus communis – common juniper Muhlenbergia glomerata – spike or marsh muhly Oligoneuron album – upland white aster Penstemon hirsutus - hairy beardtongueRosa blanda – meadow rose Saxifraga virginiensis – early saxifrage Solidago hispida – goldenrod Solidago nemoralis – gray goldenrod Sporobolus heterolepis – northern prairie dropseedZigadenus elegans var. glaucus – white camas Zizia aurea – golden alexanders

Green PRoof

• Original design – SUNY CF– Thin soil, sedums

• Uprising– Original thought?– Creative design?– World-class environmental science and design

programs?• Team of ecologists, LA, engineer

Green PRoof of Concept – Day 13

3” Bed

8” Bed

Concept – Day 34 (July 19)

Concept – Day 64 (August 18)

Dune Willow, Salix cordata (3 months)

Tall wormwood, Artemisa campestris var. caudata (Day 10-134)

Rapid coverage, great survival

Sand cherry, Prunus pumila var. depressa

Sand cherry was pruned to reduce competition, and provided great color and cover

Color/Texture

June 6, 2012 (Year 3)

ESF Gateway Building – Green Roof Section

Mirafi G4

ESF Gateway Bldg – Dune Profile

MiraDrain G4 Drainage Composite

• Filter fabric• Moisture retention mat• Drainage mat• Protection Fabric• Storage Capacity = 0.32” rain (7.97 L/m2 )(1.63

lb water/SF)• Flow rate = 75 gpm/SF

Green Roof Runoff Reduction

• Water Quality volume (WQv) = 678 CF

• Storage Volume= 739 + 0 + 132 + 0 = 871 cf

• WQv<Storage

12

))()(( ARvPWQv

)(009.005.0 IRv

P (in) = 90% Rainfall Event Number (See Figure 4.1) = 0.9I = Impervious Cover = 100 PercentRv = 0.95 A = site area = 9500 SF Minimum Rv = 0.2 if WQv > RRv

pondingdrainmatdrainlayersoiltotal VVVVV

Dune and Alvar Plantings

American Beachgrass

Field WormwoodWavy HairgrassCanada Wild Rye

Sand Dune Willow Salix cordata

Eastern Sand Cherry

Monitoring

• Soil temperature, moisture content• Survival, growth and cover• Pioneers• Precipitation, runoff

Design and Management Issues

• Designer resistance– Innovative? Need proof of concept– Faith?

• Plant propagation– Sedums are widely available

• Cost – Additional soil, unusual plants and increased structural

loads• Management

– is it a garden, or a native system?

Summary

• Native plant communities are used as the basis for a Proof-of-Concept design approach

• Rooftop growing conditions at SUNY ESF Gateway Building will emulate dune and alvar communities found along the eastern shore of Lake Ontario

• Rooftop system will meet hydrologic performance requirements, support efforts to conserve unique ecological resources, and educate ESF’s broad community, including parents, students, Board, SUNY, municipal officials, designers,…

Acknowledgments

• Co-Authors/Investigators/Photographers (SUNY ESF)– Tim Toland– Don Leopold– Terry Ettinger– James Johnson

• SUNY Construction Fund• NY Economic Development• Illustrations: Sea Grant New York