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The Case for Benefit Estimation of
WSUDAssela Pathirana
The benefit of assessing benefits –
why should we?
Assela PathiranaRichard
Ashley
Santiago Urrestarazu
Acknowledgements:
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Content
• Why seek multiple-values?
• Why assess?
Urban wetland in Taiwan
Detention pond retrofitted as a park, Japan
Sustainability ?
- Responding to ‘creeping’ disasters
• .. Endurance of systems
and processes.
• “Carrying capacity”
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Resilience
• Climate change
• Disaster risk
In the present discourse of urban development, sustainability concept alone does not respond adequately to some important needs.
- Responding to ‘Rare’ events
Sustainable, Resilient … and?
• Both long-term goals
• Homo-sapiens a short-term focused animal and usually not good at reckoning:
–Creeping phenomena with long-term impact
–Very low probability (but high consequence) events.
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Water Sensitive Cities
Three capacities
• Carrying Capacity
• Coping Capacity
• Comfort Capacity
: Sustainability
: Resilience
: Livability
Integrate Livability
• Sustainability, Resilience are essential, but
• Don’t forget immediate benefits – Livability.
People respond more readily to livability.
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IUWCM
Surface
Water Wastewater
Water Supply
Recycling
CSO/Flood
reduction
Demand
Management
recycling
Water Sen
sitive
Cities
IUWCM: Integrated Urban Water Cycle Management
The need to make an economic argument
• Inclusion of green infrastructure in urban areas
is usually for aesthetic, recreational or
biodiversity reasons not to do with water
• More apparent drivers, benefits & costs for
improved water management by WSUD will
strengthen the argument
• Policy makers will then listen
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Should we value benefits?
• Difficult to– Identify & link benefits to quantifiable outcomes
–Value quantified benefits (reliance on transfers)
–Aggregate (benefits, populations, time)
• Uncertainty
• Takes time and resources
• Moral concerns
If we don’t, they are zero
What is possible? How do we account
for the benefits and should we?
Provide amenity
and recreation
Improve
water quality
Limit flows
entering system
Use as a
resource
Improve health
and wellbeing
Provide
education
Increase
property value
Help manage
air quality
Improve thermal
comfort
Maximise
network capacity
Enhance quality
of urban space
Enhance
biodiversity
12
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Examples of multiple value from SuDS
(main objective: Storm-water management)
Evaluating the benefits unlocks the
potential for…• Fairer comparisons
• Better decision making
• Meeting funding requirements
• Enabling conversations
• Delivering WSUD14
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Case study
Upper Quitacalzones catchment
Montevideo, Uruguay
Case study
Upper Quitacalzones catchment
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Case study
Montevideo, Uruguay, South America
220 ha of urban residential area
Combined Sewer System starts to overflow for storms of Tr = 3 years
Around 610 houses are affected
Problem:
Current Proposed Solution:
3 Underground storages
Avoids flooding for storms up to Tr =10 years
Approximate Implementation cost = 10.000.000 US$
Approximate Cost of flooding = 18.000.000 US$ (30.000 US$ per house approx)
Model set up – SWMM 5.0 (US EPA)
SWMM Network & subcatchments
Synthetic rainfall
Tr of 5, 10, 20 and 50 years
Design rainfalls
0.00
50.00
100.00
150.00
200.00
250.00
00:00 01:00 02:00 03:00 04:00 05:00 06:01
Pre
cip
itat
ion
in
ten
sity
(m
m/h
r)
Duration (hours)
5 years
10 years
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SuDS - costs & ES benefitsC
osts
ES
ben
efi
ts
Present values
30 years lifespan
Installation & maintenance
600 litres
“treats” 40 m2 of roof
Extensive green roof
Soil depth = 90 mm300 US$/barrel
(7.5 US$/m2)
142 US$/m2
Present values
30 years lifespan
SWM benefits not considered here
125 US$/barrel
(3.1 US$/m2)
132 US$/m2
Green roofs & Rain Barrels
Approx 64% of the area is covered by roofs. 80% of that is suitable for green roofs
Analyzed Solution:
energy & carbon emissions saving (building isolation & less water treated), property value uplift, food production, increase of roof longevity, air pollution removal, aesthetics.
main water saving, energy & carbon emissions saving (less water treated);
Multi-objective optimization Scenarios
With ES Without ES
SuDS Scenario 1 Scenario 2
SuDS & storages Scenario 3 Scenario 4
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‘Value’ depends on how you look at it!
0.0E+00
5.0E+06
1.0E+07
1.5E+07
2.0E+07
2.5E+07
3.0E+07
3.5E+07
4.0E+07
4.5E+07
To
tal
ben
efit
s (U
S$
)
Total costs (US$)
SuDS & storages -with ES
SuDS & storages -
without ES
What others have done already to assess
multiple benefits
• Number of
examples from
around the world
22
– Ecosystem Services: • Mayesbrook Park• Flood & Coastal Erosion Risk Management
Eftec 2010
– Green Infrastructure:• Green Infrastructure North West Halewood
primary school SuDS
– Surface Water:• Centre for Neighborhood Technology:
Philadelphia CSO reduction SuDS
– Environmental• INFFER - Investment Framework for
Environmental Resources
– Planning• Integrated Valuation of Environmental
Sciences and Tradeoffs (InVEST)
– Many health economic benefit assessments
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(Marlow et al, in print, WERF)
Conclusion: Calculate (&
Talk) money!
• Never underestimate the business case.
• Think of multiple benefits.
• Focus on Livability too.
• Calculate cost/benefit.
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