Green Roofs - Living Architecture Monitor - Summer 2017 - 9

RESEARCH PROFILE

RESEARCH:

THE CONTROL OF NUTRIENTS
IN GREEN ROOF RUNOFF
BY MIKE HARDIN, PHD, PE, CFM

One of the most significant benefits of green roofs is the stormwater volume
reduction they can provide in urban environments. This inherently provides
a water quality benefit, in the sense that a runoff volume reduction typically
results in a mass reduction.

H

owever, green roofs have a significant mass of organic materials associated with them. This comes in the form of organics
such as compost or peat that are a part of the growing media,
the plants, and any fertilization during plant establishment.
Conventional roofs can also be a source of nutrients with the
primary source being atmospheric deposition, for example
combustion processes release NOx into the atmosphere which
can accumulate on roof tops during interevent dry periods and be
washed off during rainfall events.
Several studies performed by the University of Central
Florida's (UCF) Stormwater Management Academy examined
the water quantity and quality benefits of a specifically designed
green roof. That design consisted of a green roof that utilized a

cistern to capture runoff and reuse it for irrigation of the green
roof. This resulted in a significant increase in stormwater
volume reduction. This reduction is, of course, dependent on
the amount of storage provided and local rainfall patterns.
A model which allows for prediction of the hydrologic efficiency
based on green roof design, cistern size, and local rainfall data
was developed as part of this work. It is a long-term continuous
simulation model that uses a mass balance approach to calculate
the hydrologic efficiency. Figure 1 shows an example efficiency
curve for Orlando, Florida. It can be seen that a green roof in
Orlando, Florida can reduce the volume of stormwater by between about 40% to 95% on an average annual basis, depending
on if a cistern is used and the size.

AVERAGE ANNUAL FRACTIONAL RUNOFF VOLUME REDUCTION

FIGURE 1: GREEN ROOF HYDROLOGIC EFFICIENCY RELATIVE TO CISTERN SIZE
FOR ORLANDO, FLORIDA

0.9
0.75
0.6
0.45
0.3

0

1

2

3

4

5

6

CISTERN STORAGE SIZE (INCHES/GREEN ROOF AREA)

LIVINGARCHITECTUREMONITOR.COM

LIVING ARCHITECTURE MONITOR / SUMMER 2017 / 9


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Table of Contents for the Digital Edition of Green Roofs - Living Architecture Monitor - Summer 2017

Green Roofs - Living Architecture Monitor - Summer 2017 - Intro
Green Roofs - Living Architecture Monitor - Summer 2017 - Cover1
Green Roofs - Living Architecture Monitor - Summer 2017 - Cover2
Green Roofs - Living Architecture Monitor - Summer 2017 - TOC
Green Roofs - Living Architecture Monitor - Summer 2017 - A
Green Roofs - Living Architecture Monitor - Summer 2017 - 1
Green Roofs - Living Architecture Monitor - Summer 2017 - 2
Green Roofs - Living Architecture Monitor - Summer 2017 - 3
Green Roofs - Living Architecture Monitor - Summer 2017 - 4
Green Roofs - Living Architecture Monitor - Summer 2017 - 5
Green Roofs - Living Architecture Monitor - Summer 2017 - 6
Green Roofs - Living Architecture Monitor - Summer 2017 - 7
Green Roofs - Living Architecture Monitor - Summer 2017 - 8
Green Roofs - Living Architecture Monitor - Summer 2017 - 9
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Green Roofs - Living Architecture Monitor - Summer 2017 - 27
Green Roofs - Living Architecture Monitor - Summer 2017 - 28
Green Roofs - Living Architecture Monitor - Summer 2017 - 29
Green Roofs - Living Architecture Monitor - Summer 2017 - 30
Green Roofs - Living Architecture Monitor - Summer 2017 - 31
Green Roofs - Living Architecture Monitor - Summer 2017 - 32
Green Roofs - Living Architecture Monitor - Summer 2017 - 33
Green Roofs - Living Architecture Monitor - Summer 2017 - 34
Green Roofs - Living Architecture Monitor - Summer 2017 - Cover3
Green Roofs - Living Architecture Monitor - Summer 2017 - Cover4
Green Roofs - Living Architecture Monitor - Summer 2017 - M1
Green Roofs - Living Architecture Monitor - Summer 2017 - AD1
https://www.nxtbook.com/dawson/greenroofs/lam_2020Summer
https://www.nxtbook.com/dawson/greenroofs/lam_2020Spring
https://www.nxtbook.com/dawson/greenroofs/lam_2019Winter
https://www.nxtbook.com/dawson/greenroofs/lam_2019Fall
https://www.nxtbook.com/dawson/greenroofs/lam_2019Summer
https://www.nxtbook.com/dawson/greenroofs/lam_2019Spring
https://www.nxtbook.com/dawson/greenroofs/lam_2018winter
https://www.nxtbook.com/dawson/greenroofs/lam_2018Fall
https://www.nxtbook.com/dawson/greenroofs/lam_2018summer
https://www.nxtbook.com/dawson/greenroofs/lam_2018spring
https://www.nxtbook.com/dawson/greenroofs/lam_2017winter
https://www.nxtbook.com/dawson/greenroofs/lam_2017fall
https://www.nxtbook.com/dawson/greenroofs/lam_2017summer
https://www.nxtbook.com/dawson/greenroofs/lam_2017Spring
https://www.nxtbook.com/dawson/greenroofs/lam_2016winter
https://www.nxtbook.com/dawson/greenroofs/lam_2016fall
https://www.nxtbook.com/dawson/greenroofs/lam_2016summer
https://www.nxtbook.com/dawson/greenroofs/lam_2016spring
https://www.nxtbook.com/dawson/greenroofs/lam_2015Winter
https://www.nxtbook.com/dawson/greenroofs/lam_2015fall
https://www.nxtbook.com/dawson/greenroofs/lam_2015summer
https://www.nxtbook.com/dawson/greenroofs/lam_2015spring
https://www.nxtbook.com/dawson/greenroofs/lam_2014winter
https://www.nxtbook.com/dawson/greenroofs/lam_2014fall
https://www.nxtbook.com/dawson/greenroofs/lam_2014summer
https://www.nxtbook.com/dawson/greenroofs/lam_2014spring
https://www.nxtbook.com/dawson/greenroofs/lam_2013winter
https://www.nxtbook.com/dawson/greenroofs/lam_2013fall
https://www.nxtbook.com/dawson/greenroofs/lam_2013summer
https://www.nxtbook.com/dawson/greenroofs/lam_2013spring
https://www.nxtbook.com/dawson/greenroofs/lam_2012fall
https://www.nxtbook.com/dawson/greenroofs/lam_2012summer
https://www.nxtbook.com/dawson/greenroofs/lam_2012spring
https://www.nxtbook.com/dawson/greenroofs/lam_2012winter
https://www.nxtbook.com/dawson/greenroofs/lam_2011fall
https://www.nxtbook.com/dawson/greenroofs/lam_2011summer
https://www.nxtbook.com/dawson/greenroofs/lam_2011spring
https://www.nxtbook.com/dawson/greenroofs/lam_2011winter
https://www.nxtbook.com/dawson/greenroofs/lam_2010fall
https://www.nxtbook.com/dawson/greenroofs/lam_2010summer
https://www.nxtbook.com/dawson/greenroofs/lam_2010spring
https://www.nxtbook.com/dawson/greenroofs/lam_2010winter
https://www.nxtbook.com/dawson/greenroofs/lam_2009fall
https://www.nxtbook.com/dawson/greenroofs/lam_2009summer
https://www.nxtbook.com/dawson/greenroofs/lam_2009spring
https://www.nxtbook.com/dawson/greenroofs/lam_2009winter
https://www.nxtbook.com/dawson/greenroofs/lam_2008fall
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