EXTENDED TREE PITS IN HAMILTON,

ONAn ASCE-Inspired investigation into the

benefits of ETPs and Analytical Probabilistic approaches

Robert RawlinsICWMM 2019Feb 28, 2019

ROBERT RAWLINS

• 2016: B.Sc Integrated Science (McMaster University)

• 2017-Present: M.A.Sc Civil Eng [Water Resources] (McMaster University)

• Love: Playing any sport, singing, adventure, talking about a more thoughtful and intentional world!

OVERVIEWContext:• The World’s “To-Do List”• Sustainable Development Goals

(SDGs)• The ASCE’s Roadmap to Sustainable

Development

Case Study:• The Needs of Hamilton, ON• ETP retrofits as a Solution• APE for ETPs• Shortcomings and Next Steps

(A FRACTION OF) THE WORLD’S TO-DO LIST

• IPCC 2018 Report• WWF 2018 Report• Population Growth• Urbanization predictions• Increasing Hunger %• Unbounded Water Pollution• $1 Trillion of Food Waste….

“an ear-splitting wake-up call to the world” that although “we have the tools to make our actions

effective”, what is still missing “is the leadership – from politicians, from business and scientists, and from the

public everywhere…and the ambition to do what is needed.” (IPCC 2018; Guterres 2018)

The Sustainable Development Goals (SDGs)

• 17 Global Goals for “peace and prosperity for people and the planet, now and in the future.”

• “An urgent Call for Action”

• Created and adopted by all members of the UN (including Canada) in 2015!

ASCE’s 5-Year Roadmap to Sustainable Development

Sustainability: “Economic, Environmental, Social conditions where all society is able to maintain and improve quality of life indefinitely without degrading the quantity, quality, or availability of economic, environmental, and social resources.”

The issues we are facing, “require serious re-evaluation of current professional practice and standards.”

Keys for Sustainable Development:

1. Do the Right Project

2. Do the Project Right

3. Transform the Profession

4. Communicate and Advocate

1. DOING THE RIGHT PROJECT

• Focus on NEEDS, not Product• Abandon old standards• Use available resources (natural

infrastructure and Nature-Based Systems)!

2. DOING THE PROJECT RIGHT

• Assume non-stationary conditions• Focus on Resilience• Reduce net ecological footprint• Climate-aware solutions

3. TRANSFORMING

THE PROFESSION

• Consider entire life-cycle cost and multi-dimensional impacts.

• Acknowledge risk of old standards• Expand abilities beyond “currently

accepted technical acumen”• Adopt an Integrated approach

4. COMMUNICATING AND ADVOCATING

• Responsibility to inspire Sustainable Development.

• Collaborate with diverse, cross-sectoral stakeholders.

• Promote environmentally, economically, and socially sustainable infrastructure

• “Align with UN’s SDGs to support global implementation and collaboration.”

THE ‘NEEDS’ OF HAMILTON, ONTARIO

Met with City officials and NGOs:• Establishing and maintaining a healthy Urban Forest a huge target.

• Trees Please Initiative (30% canopy coverage by 2030)

• Hamilton Harbour: 1 of 17 high-priority environmental areas• CSO management in context of climate change, increasing

population, and rapid upstream urbanization.

• Downtown revitalization

WHY ARE URBAN FORESTS SO IMPORTANT?

• Societal Efficacy + Pre-Development Hydrologic Cycle

• Peak Flowrates + Volumes

• Ground water Recharge

• Evapotranspiration

• Because our cities WERE forests

URBAN FORESTSEnvironmental:• Oxygen, Sequester Carbon, Air Quality,

Reduced urban heat island effect and UV radiation, reduce downstream erosion, protect downstream receiving waters,increase interception, infiltration, and evapotranspiration

Social:• Improved attitudes and responses to

stress, lower crime, superior cardiovascular health, less extreme temperatures, more pleasant urban experience, reduced flood risk

Economic:• Reduced energy costs• Greater consumer spending• Reduced Costs of Water-treatment

INTERCEPTION

• Water detained in canopy storage

• Water is evaporated, infiltrated, or delayed

• Dependent on several factors

Tree Species Interception valuesPear, Pyrus calleryana ‘Bradford’ (Deciduous)

15%

Eucalyptus pauciflora 0.178 mm/unit-leaf-areaCork oak, Quercus suber (Evergreen) 27% total rainfallEucalyptus maculata 0.032 mm/unit-leaf-areaBroadleaved native forest 14-37% annual

precipitationDouglas fir 22% over 26 months,

69% annualFagus sylvatica 16-23%Pseudotsuga menziesii 32-36%Pinus radiata 11-39%Conifers 34%Western Redcedar 75% annuallySmall Jacaranda mimosifolia 15.3% (0.8 m3/tree)Mature Tristania conferta 66.5% (20.8 m3/tree)Mature Platanus acerifolia 14.8% of 21.7 mm winter

79.5% of 20.3 mm summer

INFILTRATION

• Highly variable• Dependent on Soil

Compaction• Trees can reduce soil

compaction• Lowest values still

significant

Feature Studied

Uncompacted Compacted Study

Natural Forest 377 to 634 mm hr-1

8 to 175 mm hr-1

(Gregory et al. 2006)

Planted Forest

637 to 652 mm hr-1

160 to 188 mm hr-1

(Gregory et al. 2006)

Tree Pits 162 mm hr-1

(Guarded)36 mm hr-1

(Unguarded)(Alizadehtazi et al. 2016)

Pasture 225 mm hr-1 23 mm hr-1 (Gregory et al. 2006)

NYC Tree pits 60 to 4044 mm hr-1

N/A (Elliott et al. 2018)

EVAPOTRANSPIRATION

• Largest contributor of precipitation losses

• Variable and dependent on variety of parameters• Species

• Size

• Age

• Canopy

• Climatic factors

Species Setting ET Rate Study

Pinus canariensis

Urban 3.2 ± 2.3 𝑘𝑘𝑘𝑘 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡-1 d-1 (Pataki et al. 2011)

Platanus hybrida

Urban 176.9 ± 75.2 𝑘𝑘𝑘𝑘 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡-1

d-1(Pataki et al.

2011)

Brachychiton populneus

Urban < 5.0 𝑋𝑋 103 𝑘𝑘𝑘𝑘 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡-1 yr-

1

12.7 ± 10.4 𝑘𝑘𝑘𝑘 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡-1 d-1

(Pataki et al. 2011)

Gleditsia triacanthos

Urban (2.5 ±1) 𝑋𝑋 10^4 𝑘𝑘𝑘𝑘 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡-1 yr-1

89.9 ± 23.6 𝑘𝑘𝑘𝑘 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡-1 d-1

(Pataki et al. 2011)

Douglas Fir Forest 4.9 𝑡𝑡𝑡𝑡 23.6 𝑘𝑘𝑘𝑘 𝑡𝑡𝑡𝑡𝑡𝑡𝑡𝑡-1 d-1 (Black, Nnyamah, and

Tan 1980)

ROADBLOCKS TO URBAN FORESTS

• Economic Cost:• Natural land

reclamation near-impossible

• Street trees subjected to higher pollution, reduced infiltration, less water, and less rooting volume

• Street trees can be costly investments (average lifespan of 7-10 years)

Needs to be met:

1. Revitalize the downtown core

2. Cost-effectively promote Urban Forest Health

3. Reduce Runoff and protect downstream receiving waters

ASCE-inspired steps:

• An integrated approach:• Use ALL available data and engage stakeholders to

understand the best steps forward

• Use what’s available:• Retrofit Extended Tree Pits to already-established

street trees

• Utilize well-established Analytical Probabilistic Expression (APE) for bioretention systems

• Advocate and Collaborate:• Efficiently estimate Stormwater Management

Benefits of solution

• Meet with NGOs and recruit Highschool students to help with data collection

INTEGRATED SITE-SELECTION

Beasley and Landsdale neighborhoods selected:• Community Improvement Plan

Applications (CIPAs)

• Air Quality Issues

• Single-parent homes twice as likely

• Poverty rates of 40% and 60%

• 3.3yr shorter life-expectancy

• 2x more likely to visit emergency room

MODEL OPTIONS – USE WHAT’S AVAILABLE• Numerous deterministic models

• i-Tree suite• SWMM + PCSWMM• SWC• LID TTT• GIFMOD• ETC

• CVC demonstrated the adequacy of simplified “lay-user” models• Literature exposes variability of Nature-Based infrastructure• Perhaps an estimate is (preliminarily) good enough

APE FOR ETPs

• Assumes rainfall characteristics are exponential in nature• Rainfall volume• Rainfall event duration• Interevent time

• Produces average LID system performance metrics based on these rainfall characteristics

• Vastly reduced parameter requirements

• The concept of continuous sim without the data

Validated against SWMM

REQUIRED DATA

Parameter Value (units)

Average rainfall event volume (v) 9.3 (mm)*

Average rainfall event duration (t) 8*

Average interevent time (b) 128 (hrs)*

Catchment Imperviousness (h) 0.9

Fill media ultimate infiltration rate

(fc)

20 (mm hr-1)

Horton's infiltration decay constant

(k)

3 (n/a)

Drying time (D) 4 (Days)

Pervious Catchment Storage (Sdp) 5 (mm)

Impervious Catchment Storage (Sdi) 2 (mm)

Max infiltration rate of media (fm) 150 (mm hr-1)

Average ET rate (Ea) 10 (mm hr-1)*Toronto statistics adopted from (Zhang and Guo, 2014)

SENSITIVITY ANALYSIS: AREA RATIO

0

50

100

150

200

250

0 20 40 60

Ove

rflo

w (m

m)

Catchment to Pit Area Ratio (r)

Expected Overflow vs Area Ratio

Varying Catchment:Pit area ratio has very significant impact on SCE

CAPTURE EFFICIENCY VS AREA RATIO

0

0.2

0.4

0.6

0.8

1

1.2

0 10 20 30 40 50 60 70 80 90 100 110

Stor

mw

ater

Cap

ture

Effi

cien

cy

Area Ratio (r)

“Not worth it”

“Sweet Spot”

DESIGN STORAGE DEPTH

0.5

0.6

0.7

0.8

0.9

1

1.1

50 250 450 650 850 1050

Stor

mw

ater

Cap

ture

Eff

icie

ncy

(Ce)

Design Storage Depth (mm)

MAX INFILTRATION RATE

0.5

0.6

0.7

0.8

0.9

1

0 200 400 600 800 1000 1200

Stor

mw

ater

Cap

ture

Effi

cien

cy

Maximum infiltration rate (mm hr-1)

FINAL INFILTRATION (CAPACITY)

0.5

0.6

0.7

0.8

0.9

1

0 10 20 30 40 50 60 70 80 90 100

Capt

ure

Effic

ienc

y (S

CE)

Final Infiltration Rate (mm hr-1)

EVAPOTRANSPIRATION

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0 100 200 300 400 500 600

Capt

ure

Effic

ienc

y

Evapotranspiration Rate (mm hr-1)

BEASLEY STATISTICS

• 97 Roadways with adjacent trees

• Average area of 0.14 ha (1400 m2)

• Average of 9.9 trees/catchment

• 140 m2 DCIA per tree

• Literature suggests ideal ETP is 5 – 7% of total catchment area.

• ~9.8 m2 for each tree

EXAMPLE• r = 6.53

• ETP = 44.9 m2

• DCIA = 293 m2

CONCLUSIONS

• Following the ASCE’s advice takes TIME• Spatial proximity does not (necessarily) create close sectoral ties• Acknowledging the needs of an area can unveil potential solutions• The case for Retrofitted ETPs is well-established in Literature• APEs for Bioretention areas and ETP estimations more than suffice

for estimations

THANK YOU

REFERENCES

• Baek, Sang Soo, Dong Ho Choi, Jae Woon Jung, Hyung Jin Lee, Hyuk Lee, Kwang Sik Yoon, and Kyung Hwa Cho. 2015. “Optimizing Low Impact Development (LID) for Stormwater Runoff Treatment in Urban Area, Korea: Experimental and Modeling Approach.” Water Research 86: 122–131. doi:10.1016/j.watres.2015.08.038.

• Chandana, Damodaram, and Zechman Emily M. 2013. “Simulation-Optimization Approach to Design Low Impact Development for Managing Peak Flow Alterations in Urbanizing Watersheds.” Journal of Water Resources Planning and Management 139 (3). American Society of Civil Engineers: 290–298. doi:10.1061/(ASCE)WR.1943-5452.0000251.

• Chui, Ting Fong May, Xin Liu, and Wenting Zhan. 2016. “Assessing Cost-Effectiveness of Specific LID Practice Designs in Response to Large Storm Events.” Journal of Hydrology. doi:10.1016/j.jhydrol.2015.12.011.

• Fletcher, Tim D., William Shuster, William F. Hunt, Richard Ashley, David Butler, Scott Arthur, Sam Trowsdale, et al. 2015. “SUDS, LID, BMPs, WSUD and More – The Evolution and Application of Terminology Surrounding Urban Drainage.” Urban Water Journal 12 (7): 525–542. doi:10.1080/1573062X.2014.916314.

• Lee, Joong Gwang, Ariamalar Selvakumar, Khalid Alvi, John Riverson, Jenny X. Zhen, Leslie Shoemaker, and Fu hsiung Lai. 2012. “A Watershed-Scale Design Optimization Model for Stormwater Best Management Practices.” Environmental Modelling and Software 37 (November). Elsevier: 6–18. doi:10.1016/j.envsoft.2012.04.011.

• McGarity, Arthur, Fengwei Hung, Christina Rosan, Benjamin Hobbs, Megan Heckert, and Shandor Szalay. 2015. “Quantifying Benefits of Green Stormwater Infrastructure in Philadelphia.” World Environmental and Water Resources Congress 2015. doi:10.1061/9780784479162.037.

• Sebti, Anas, Musandji Fuamba, and Saad Bennis. 2016. “Optimization Model for BMP Selection and Placement in a Combined Sewer.” Journal of Water Resources Planning and Management 142 (3): 4015068. doi:10.1061/(ASCE)WR.1943-5452.0000620.

• http://images.huffingtonpost.com/2016-07-03-1467586459-9704184-SDGs.jpg (Slide 4 photo)

• https://www.conservationinstitute.org/what-is-urbanization/ (Slide 15 photo)