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Apr 08, 2023 180 likes •280 views

A methodology to assess sustainability of urban stormwater management (USWM) Guido Petrucci www-yes 2009 27/10/2009 Plan Context Issues Methodology Conclusions From sewers to source control Why? Water quality concerns Urban

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A methodology to assess sustainability of urban stormwater management (USWM) Guido Petrucci

www-yes 2009 27/10/2009

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Plan

Context Issues Methodology Conclusions

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From sewers to source control

But, what is “better” to do?

Do sewer and source control be alternative or

complementary? Where? In which conditions?

Which is the good management level?

Why?

Water quality

concerns

Urban growth

 We need a tool to assess overall “sustainability” of USWM

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Sustainability assessment: issues

Local dependency on context
Variety of alternatives
Complexity of physical

phenomena

Non-technical complexity
Behaviour evolution over time

(in general: not enough feedbacks)

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USWM strategies Physical contexts Urban contexts

Alternatives to compare

Criterion m … Criterion 1 Sub-criterion n … Sub-criterion 2 Sub-criterion 1 Indicator 2 Indicator p … Indicator i … Indicator 1 Criterion m … Criterion 1 Sub-criterion n … Sub-criterion 2 Sub-criterion 1 Indicator 2 Indicator p … Indicator i … Indicator 1

Sustainability assessment: proposed methodology

1. A general framework to define

sustainability

2. Case studies
3. Generalization

We are here!

Criteria Sub-criteria Indicators Design storm return interval storage volume (m3/ha) Response rate for superimposed critical storm durations (m3/ha/hr) Ratio of storage to contributing drainage area (ratio) Number of floods per year within catchment (1...n) Overflow frequency and duration (1...n) Discharge or throttle rate (m3/s) Uniform flow distribution (H/M/L) Flood Control Storage and flood control Length of antecedent dry periods () Pollutant concentration probability exceedance for given target levels (% exceedance for given target level) First-flush capture potential (10/15mm effective runoff treatment for all storms) (mm runoff/av storm event) Pollution Control Water quality treatment %age pollution capture for given RI storms and retention times (% capture for given RI or retention time) Design freeboard for storage and water quality change (%; m3/lifetime) Ease of retrofitting and modification (H/M/L) Costs of retrofitting and add-on structures/features (Euro (av.cost)) Potential to recycle system components/waste (H/M/L) Reliability (H/M/L) System flexibility & potential for retrofitting Capability for change over time Durability (H/M/L) Flow reduction to STP and CSOs (%; m3) Integration with existing system Reduction in stormwater flows (%; m3/ha) Operational lifetime (Years) Technical Impact on drainage system Design life Sedimentation rates and storage volume (m3/yr; % reduction in storage volume/yr)

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Methodology (1/3): A framework for sustainability

From DSS: an
bjective approach to

sustainability

A general to local

approach: the Christmas tree

Test the framework by yourself: « if
ne system is better than another for

all the indicators, is it more sustainable? » (The entire list is available on: www.daywater.cz)

Criteria Sub-criteria Indicators Design storm return interval storage volume (m3/ha) Response rate for superimposed critical storm durations (m3/ha/hr) Ratio of storage to contributing drainage area (ratio) Number of floods per year within catchment (1...n) Overflow frequency and duration (1...n) Discharge or throttle rate (m3/s) Uniform flow distribution (H/M/L) Flood Control Storage and flood control Length of antecedent dry periods () Pollutant concentration probability exceedance for given target levels (% exceedance for given target level) First-flush capture potential (10/15mm effective runoff treatment for all storms) (mm runoff/av storm event) Pollution Control Water quality treatment %age pollution capture for given RI storms and retention times (% capture for given RI or retention time) Design freeboard for storage and water quality change (%; m3/lifetime) Ease of retrofitting and modification (H/M/L) Costs of retrofitting and add-on structures/features (Euro (av.cost)) Potential to recycle system components/waste (H/M/L) Reliability (H/M/L) ystem flexibility & potential for retrofitting apability for change over time Technical

...…

Criteria (general, 6) ... Indicators (local, 65)

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Methodology (2/3): Case studies

Three objectives :

– Validate framework – Find models and procedures to estimate indicators – Support the generalization phase – Answer to: “what happens, in reality?”

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Methodology (3/3): Generalization

Crossing of:

– Definitions of sustainability – Urban contexts – Physical contexts – USWM strategies

And then run models & compare

How to select?

USWM strategies Physical contexts Urban contexts

Alternatives to compare

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Conclusions & discussion

Issues:

Local dependency on context
Variety of alternatives
Complexity of physical

phenomena

Non-technical complexity
Behaviour evolution over time

(in general: not enough feedbacks) In our methodology: √ Tree structures √ Combination system ? Depends on models ? Depends on case studies X we have to wait further studies, uncertainties in scenarios We are still nel mezzo del cammin... … and the methodology needs fine tuning ... … but it solves some issues! What do you think about that?