the impact of trees on storm water runoff in an urban environment
TRANSCRIPT
8/3/2019 The impact of trees on storm water runoff in an urban environment
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This is my Story and I’d like to share it!
My Name is:
Norman Dewar
I would like to share a Pecha-Kucha presentation about:
“The impact of trees on storm water runoff in
an urban environment”
Community Dialogue Series – October 13, 2100
8/3/2019 The impact of trees on storm water runoff in an urban environment
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The style of presentation being used is called Pecha-Kucha.Drawing its name from the Japanese term for the sound of "chit chat", it rests on a presentation format that is based
on a simple idea:Pecha Kucha:
20 images x 20 seconds.6 minutes 40 seconds per presenter.
Note: Because of the presentation style, you need thespeaker notes to make sense of the slides so I’ve
embedded them in the slides. Also because of thestyle presentation, I was not able to formally credit mysources
until the end of the presentation.
8/3/2019 The impact of trees on storm water runoff in an urban environment
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“City sewers overwhelmed again”Heavy rains in Charlottetown caused thecity's combined stormwater and sanitarysewer system to overflow again.
“I’m reading yet another story about the City’s stormwater system overflowing”.
8/3/2019 The impact of trees on storm water runoff in an urban environment
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The interception effect
“And I look out my office window and notice this. It has been raining for
an hour but still the pavement is dry in a 25 ft radius around this very large
maple tree on my street.”
8/3/2019 The impact of trees on storm water runoff in an urban environment
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During the past five years, in my
neighbourhood of only 5 city lots,
we’ve lost:• 6 mature elms (70 years old?)
• 12 young elms (30 years old?)• 3 mature poplars (50 years old?)
8/3/2019 The impact of trees on storm water runoff in an urban environment
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37
“And this is the number of elms trees I heard the City has cut down this year.
Though I haven’t confirmed this number, seeing a work crew cutting down
one of these old majestic elms hardly makes you look twice, it is so common.”
8/3/2019 The impact of trees on storm water runoff in an urban environment
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Could this be impacting stormwater
runoff in Charlotteotwn???
“And that got me thinking, based on what I saw from my window,
could this be impacting stormwater runoff in Charlottetown?”
8/3/2019 The impact of trees on storm water runoff in an urban environment
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and I found these numbers…
Rainfall Interception by Trees
– 10 - 40% of annual rainfall (Zinke, 1967)
– Canopy interception ave. 35-40% (Calder 1990, 2003)
– Even in winter
• 15% for a deciduous tree (Xiao et al 2000).
• 27% for an evergreen species (Xiao et al 2000).
8/3/2019 The impact of trees on storm water runoff in an urban environment
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A 1 inch of rain in Charlottetown equals 27,697,080
gallons of water. A loss of 10% tree canopy means 0.5 –
1.3 million gallons more stormwater.
8/3/2019 The impact of trees on storm water runoff in an urban environment
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Urban vs Forested
Storm Hydrographs
0
50
100
150
200
250
300
350
400
0 2 4 6 8 10 12 14 16
Time
F l o w R
a t
urbanurban
forestforest
“As show in in this graph, in an urban environment, the storm water flow is “flashy”
versus a forest which holds holds the water and releases it slowly over a longer period.”
8/3/2019 The impact of trees on storm water runoff in an urban environment
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Fewer Trees = More Runoff
8/3/2019 The impact of trees on storm water runoff in an urban environment
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trees & stormwater: some conclusions
1. Increases in tree cover and tree size will result inreduced total runoff and peak runoff rates
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trees & stormwater: some conclusions
1. Increases in tree cover and tree size will result inreduced total runoff and peak runoff rates
2.Effects on runoff are greatest when urban trees
are large and well-established
8/3/2019 The impact of trees on storm water runoff in an urban environment
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2. Effects on runoff are greatest when urban
trees are large and well-established
• These are exactly the trees we are losing.
• Whatever engineering solutions we come
up with today will be inadequate in the
future unless we change our stormwater
management practices
• The trees we plant today could extend the
life of our stormwater system
8/3/2019 The impact of trees on storm water runoff in an urban environment
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3. Effects on runoff are greatest when urban
trees are large and well-established
• These are exactly the trees we are losing.
• What ever engineering solutions we come
up with today, we can expect their
capacity will be exceeded in 40 years
• The trees we plant today could extend the
life of our stormwater system
• A small investment today could return
millions of dollars in future savings.
8/3/2019 The impact of trees on storm water runoff in an urban environment
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Are we missing an opportunity?
8/3/2019 The impact of trees on storm water runoff in an urban environment
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The following slides contain links to the presentations
which I used as reference. They are excellent and Iencourage you to have a look.
8/3/2019 The impact of trees on storm water runoff in an urban environment
http://slidepdf.com/reader/full/the-impact-of-trees-on-storm-water-runoff-in-an-urban-environment 18/19
using trees to reduce stormwater runoff
http://www.slideshare.net/watershedprotection/using-trees-to-reduce-stormwater-runoff-formatted-presentation
8/3/2019 The impact of trees on storm water runoff in an urban environment
http://slidepdf.com/reader/full/the-impact-of-trees-on-storm-water-runoff-in-an-urban-environment 19/19
urban watershed forestry
concepts
http://www.slideshare.net/watershedprotection/formatted-uwf-slideshow-presentation