The Case for Benefit Estimation of WSUD Assela Pathirana · The Case for Benefit Estimation of WSUD...

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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

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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.