hydrologic performance of vegetated roofs - michigan · 2016-02-26 · • most companies report...
TRANSCRIPT
![Page 1: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/1.jpg)
Hydrologic Performance of Vegetated Roofs
Donald Carpenter, Ph.D., PE, LEED AP Nathan Griswold, ASLA, GRP
Lawrence Technological University Inhabitect, LLC
![Page 2: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/2.jpg)
Session Overview
• Brief Introduction to Vegetated Roofs
• Hydrologic Performance
• Monitoring
• Modeling
• Hydrologic Design Parameters
![Page 3: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/3.jpg)
Stormwater Management
• Every drop of stormwater
that hits a jobsite must be
accounted for and managed
in some form or fashion
• Vegetated roofs are capable
and have the ability to
managing a high percentage
of this rain on our rooftops
• Filter the runoff to improve
water quality
![Page 4: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/4.jpg)
Vegetated roofs, also known as green roofs, eco-roofs
or living roofs, are engineered systems that are
installed over a watertight, man-made, structure
Green roofs offer a wide range of economic,
ecological, and social benefits in both the public and
private sector
Vegetated Roofs
![Page 5: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/5.jpg)
Public Benefits of Green Roofs
• Create “Green Collar” jobs
• Improve stormwater management (quality and quantity)
• Improve air quality
• Increase biodiversity
• Decrease municipal infrastructure costs
• Increase tax revenue
• Reduce the urban heat island effect and peak load energy demand
• Improve community health and well being
• Facilitate new recreational opportunities
• Reduce greenhouse gas emissions
![Page 6: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/6.jpg)
Private Benefits of Green Roofs
• Aesthetic improvements
• Energy savings
• Increase property values
• Increase employee productivity
• Reduce employee absenteeism
• Improve solar panel efficiency
• Improve roof membrane durability
• Meet stormwater and green space regulations
• Improve marketability
• Urban agriculture revenue potential
![Page 7: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/7.jpg)
Typical Assembly
• Plants
• Engineered media
• System Filter
• Drainage and Water retention
• Insulation
• Root Barrier
• Waterproofing
![Page 8: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/8.jpg)
Extensive Intensive
Types of Green Roofs
![Page 9: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/9.jpg)
Intensive Roof
![Page 10: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/10.jpg)
Intensive Roof
![Page 11: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/11.jpg)
Extensive Green Roofs
![Page 12: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/12.jpg)
St. Clair Community College
Extensive Roof
![Page 13: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/13.jpg)
Comparing the Two Roofs
Characteristics Intensive Green Roof Extensive Green Roof
Soil Greater than 6” of soil
depth
Less than 6” soil depth
Vegetation Accommodates large
trees, shrubs, and well-
maintained gardens
Capable of including
many kinds of vegetative
ground cover and grasses
Load Adds 35-300 pounds per
square foot
Adds 12-35 pounds per
square foot
Access Regular access
accommodated &
encouraged
Usually not designed for
public accessibility
Maintenance Significant maintenance
required
Low maintenance
requirements
Drainage Includes more robust
drainage systems
Simple drainage system
![Page 14: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/14.jpg)
Vegetated Roofs act like a Sponge
![Page 15: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/15.jpg)
Vegetated Roof Hydrologic Design
• Hydrologic response is dependent on roof type and rainfall
characteristics
• Most companies report annual retention values – not helpful for
site design
• CN and C will vary for each storm – need site specific
information or modeling
![Page 16: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/16.jpg)
Hydrologic Performance
• Response is diverse due to:
– variation in the physical properties of the media
– layered structure of the various proprietary systems
– local climatic conditions
![Page 17: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/17.jpg)
Southfield
Lawrence Tech
![Page 18: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/18.jpg)
Lawrence Tech Vegetated Roof
• 10,000 sq ft: Hydrotech
Garden Roof Assembly • Research project to determine
the long term effectiveness with regards to water quality and quantity (USEPA and LTU COE)
![Page 19: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/19.jpg)
LTU Vegetated Roof Cross-Section
![Page 20: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/20.jpg)
LTU Vegetated Roof Performance
Evaluation Goals • Establish long-term monitoring station capable of
determining the temporal performance of the green roof
• Determine the overall percent of precipitation retained and
detained by the green roof (water quantity)
• Determine the nutrient loading capabilities of the green roof
(water quality)
• Determine the reduction in ambient temperature associated
with the green roof (air quality)
![Page 21: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/21.jpg)
Experimental Set-Up
Blackroof
Stoneroof
Greenroof
• Performance monitoring
equipment was set up on three
full scale roof systems on
campus
– 3496 sq ft Garden Roof
(greenroof)
– 912 sq ft new rock ballast
roof (stoneroof)
– 1647 sq ft existing asphalt
roof (blackroof)
![Page 22: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/22.jpg)
Monitoring Equipment
• Teledyne ISCO Avalanche Samplers
• Teledyne ISCO 730 Bubbler Flowmeter
• Teledyne ISCO 674 Rain Gauge
• 4" Palmer-Bowlus Flumes
• Microdaq USB Temperature sensors
![Page 23: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/23.jpg)
Flow Monitoring Equipment
![Page 24: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/24.jpg)
Normalized Hydrographs - June 10, 2008
0
0.005
0.01
0.015
0.02
0.025
0.03
0.035
0.04
0 2 4 6 8 10
Time (hours)
Dis
ch
arg
e (
cfs
) p
er
1000 s
q f
t ro
of
0
0.005
0.01
0.015
0.02
0.025
0.03
Ra
infa
ll (
ft)
Blackroof
Stoneroof
Greenroof
Rainfall
![Page 25: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/25.jpg)
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 1000 2000 3000 4000
Time (hours)
Ru
n-o
ff /
Rain
fall
(ft
)
10.44%
48.56%
68.24%
Cumulative Runoff Depth (ft)
![Page 26: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/26.jpg)
Greenroof Retention (April - September 2008)
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
Apr-08 May-08 Jun-08 Jul-08 Aug-08 Sep-08
Month
De
pth
(in
)
0
10
20
30
40
50
60
70
80
90
100
Pe
rce
nt
Re
tain
ed
(%
)
Amount Retained Rainfall Percent Retained
![Page 27: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/27.jpg)
Runoff Volume Coefficient
Runoff Comparison - 3 Roofs
0
0.5
1
1.5
2
2.5
3
0 1 2 3
Rainfall (inches)
Ro
of
Ru
no
ff (
inch
es)
BR
SR
GR
Linear
(BR)
Linear
(SR)
Poly. (GR)
Runoff Comparison - 3 Roofs
0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
0 0.2 0.4 0.6 0.8 1
Rainfall (inches)
Ro
of
Ru
no
ff (
inch
es)
BR
SR
GR
Linear
(BR)
Power
(GR)
Linear
(SR)
![Page 28: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/28.jpg)
LTU Water Quantity Summary
• Volume Retention
– Rain = 13.4” Black = 12.0” Stone = 6.88” Green = 4.25”
• Peak discharge reduction of 54.23% to 99.94%
• Run-off volume coefficient varies with event magnitude
Size Category Storm Size Number of
Observations Greenroof Blackroof Stoneroof
Small 0.1 -0.5 (in) 9 0.037 0.88 0.44
Medium 0.5 – 1 (in) 8 0.13 0.91 0.36
Large > 1 (in) 3 0.55 0.92 0.62
![Page 29: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/29.jpg)
Hydrologic Modeling
![Page 30: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/30.jpg)
What is the market asking for?
• Proof of green roof performance
• Specific stormwater management data
• Proof of compliance with local and federal code requirements
• Stormwater quantification data
• For use in measurable drainage computations
by design professionals
![Page 31: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/31.jpg)
National Stormwater Calculator (SWC)
• Developed by the EPA
• A desktop tool that helps users control
runoff to promote natural movement
of water and to protect and restore the
environmental integrity of our
waterways
• Clean water is essential to keeping our
families and the environment healthy
![Page 32: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/32.jpg)
National Stormwater Calculator (SWC)
• Location
• Soil Type
• Soil Drainage
• Topography
• Precipitation
• Evaporation
• Climate Change
• Land Cover
• Low Impact Development (LID) Controls
• Runoff
![Page 33: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/33.jpg)
Green Values Stormwater Toolbox
• Developed by the the Center for
Neighborhood Technology (CNT)
• Primarily for planners, engineers, and
other municipal staff
• Calculates the benefits of green
infrastructure for individual sites and to
influence public policy
![Page 34: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/34.jpg)
Green Values Stormwater Toolbox
• Learn what green infrastructure is and
what it offers
• Learn how green infrastructure can help
you save money
• Understand the costs and benefits of
using green infrastructure to mitigate
the need for different types of built
water infrastructure, such as sewers and
detention basins
![Page 35: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/35.jpg)
Hydrotech Hydrology Tool (HHT)
• Manufacture specific calculation
• Calculations offered free of charge
• Utilizes known performance of specific
green roof materials
– Lawrence Tech was one of many monitoring
programs used to calibrate the HHT
![Page 36: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/36.jpg)
Hydrotech Hydrology Tool (HHT)
• Can address site specific stormwater
requirements
• Provide proof of the Hydrotech Garden
Roof Assembly’s performance
• Stormwater quantification data for use in
accurate and measurable drainage
computations
![Page 37: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/37.jpg)
Hydrotech Hydrology Tool (HHT)
• 24 hour storm event evaluations
– How much water is retained within the
Garden Roof Assembly
• Short duration storms events (Rational
Method)
– How fast water is leaving the Garden Roof
• Long term storm evaluations
– Predicts average performance of the Garden
Roof
• Establish LEED compliance
– Does the Garden Roof help the projects
LEED goals
![Page 38: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/38.jpg)
Extensive Vegetated Roof Design
Parameters
• Recommend Modeling for Performance BUT…
• Curve Numbers
– CN = 65 for rain events 3 x’s depth of media (MI LID
Manual)
– CN = 85 for events greater than moisture holding capacity
(ASCE Green Roof TC)
• Runoff Volume Coefficient
– 0 < Cv < 0.8
• Time to Peak
– At least one hour
![Page 39: Hydrologic Performance of Vegetated Roofs - Michigan · 2016-02-26 · • Most companies report annual retention values – not helpful for site design ... –912 sq ft new rock](https://reader033.vdocuments.us/reader033/viewer/2022043016/5f3929e9d587f24f1e580c68/html5/thumbnails/39.jpg)
Smarter Design
• Vegetated roofs are a value added piece of the larger, longer term, infrastructure puzzle
• Vegetated roof systems must be designed according to local climatic conditions
• Performance expectations must be based on vegetated roof system and the climatic conditions
• Important to understand performance in the region of application and preferably from full-scale monitoring or modeling results