1. Developing a New DSS for SuDS
Design and Flood Risk Management
Jo-fai Chow*, Dragan
Savić, David Fortune
and Zoran Kapelan

2. Introduction
jo-fai.chow@microdrainage.co.ukSlide (01/21)
• About this project
– STREAM Industrial
Doctorate Centre
• Cranfield, Exeter*,
Imperial, Newcastle &
Sheffield University
– Micro Drainage (an XP
Solutions Company)
– EPSRC funded
• Goal
– New features for
commercial drainage design
software
• About me
– Civil and Environmental
Engineering (BEng, MSc)
– Water Infrastructure
Asset Management
Consultant
• Data-driven Modelling
• Optimisation using
Genetic Algorithm
– PhD candidate in
Hydroinformatics

3. Towards Sustainability
jo-fai.chow@microdrainage.co.ukSlide (02/21)
Social
• What are covered in most
drainage design software
packages?
– Environmental
• Water quantity
• Water quality
– Economic
• Life cycle cost
• Not enough emphasis on
– social impact
– multiple benefits
Sustainability Circles

4. Research Objectives
jo-fai.chow@microdrainage.co.ukSlide (03/21)
• Maximising multiple benefits
– Identifying best trade-off
• Communication Platform
– Planners, engineers, architects,
landscape architects, developers, local
government, insurance companies,
water companies …
• Integration with existing
software
– Additional decision support

5. Sustainable Drainage Systems
Conventional Drainage Systems
How to Define a “Good” Drainage Design?
jo-fai.chow@microdrainage.co.ukSlide (04/21)
• In the past
– least cost design with
sufficient hydraulic
performance
• Now
– Market drivers: legislation,
best practice
– must consider the use of
SuDS first
• Challenge
– optimal combination?
Better use
of large
pipes ??
Das Park Hotel, Australia

6. SuDS Management Train
jo-fai.chow@microdrainage.co.ukSlide (05/21)
Source: CIRIA (2005) SuDS Management Train <http://www.ciria.com/suds/suds_management_train.htm>

7. SuDS in Drainage Network Model
jo-fai.chow@microdrainage.co.ukSlide (06/21)
Porous car park
Swale
Pond
A typical development site model

8. How many different options?
jo-fai.chow@microdrainage.co.ukSlide (07/21)
No. of options = No. of feasible SuDS techniques ^ No. of Location
= 51
= 5
Simple calculation example:
Say, after an initial analysis of a
development site, there is ONE suitable
location for SuDS. For this location, there
are FIVE feasible choices of SuDS.
How many different design options?

9. How many more options?
jo-fai.chow@microdrainage.co.ukSlide (08/21)
Second calculation example:
Now consider THREE suitable locations for
SuDS and FIVE feasible choices of SuDS.
How many different design options now?
No. of options = No. of feasible SuDS techniques ^ No. of Location
= 53
= 125

10. Can it get more complicated?
jo-fai.chow@microdrainage.co.ukSlide (09/21)
• Solution
– Brute Force?
– Optimisation
– Smart Rules
– Parallel Computing
• Yes! There are other
factors
– Sizing parameters
– Infiltration
parameters
– Multiple scenarios
• The search space is
HUGE!!

11. Prototype Framework
jo-fai.chow@microdrainage.co.ukSlide (10/21)
• Caveats:
– Simple Muskingum
Routing
– No backwater
– No flow control
– Simple Pollutant
Removal %
• Focus:
–Application
prototyping
–Simple and easy
to understand
–Graphical Outputs

12. Optimisation Framework
jo-fai.chow@microdrainage.co.ukSlide (11/21)
Prototype SuDS Treatment Train Optimisation Framework
Optimisation Parameters, Range and True Values SuDS Key Performance Indicators Graphical Outputs
Min. Max. Description of KPI Value
SuDS Technique 1 to 16 10 1 16 Infiltration Basin Peak Flow at Outlet (m3/s) 2.73
Physical Dimension 1 1 to 10 10 10 29 11.9 Total Storage Required (m3) 6187
Physical Dimension 2 1 to 10 34 19 26 21.4 Time to Reach Peak Flow (min) 238
Physical Dimension 3 1 to 10 62 2 5 3.7 Total Nitrogen 6.75
Inflitration % (Side) 1 to 10 67 0 25 16.8% Total Phosphorus 8.52
Inflitration % (Base) 1 to 10 16 0 25 4.0% Total Suspended Solids 5.70
SuDS Technique 1 to 16 1 1 16 Pervious Pavements Hydrocarbons 10.78
Physical Dimension 1 1 to 10 59 10 33 23.6 Heavy Metals 5.45
Physical Dimension 2 1 to 10 25 6 43 15.3 Faecal Coliforms 18.56
Physical Dimension 3 1 to 10 20 1 3 1.0 SuDS 1 WLC (£ at 2012 value) £175,620
Inflitration % (Side) 1 to 10 14 0 25 3.5% SuDS 2 WLC (£ at 2012 value) £225,519
Inflitration % (Base) 1 to 10 25 0 25 6.3% SuDS 3 WLC (£ at 2012 value) £317,955
SuDS Technique 1 to 16 13 1 16 Stormwater Wetlands Total WLC (£ at 2012 value) £719,093
Physical Dimension 1 1 to 10 95 19 26 25.7
Physical Dimension 2 1 to 10 74 9 36 29.0 Other Measurements
Physical Dimension 3 1 to 10 48 1 3 1.7
Inflitration % (Side) 1 to 10 94 0 25 23.5% Description of KPI Value
Inflitration % (Base) 1 to 10 91 0 25 22.8% SuDS 1 Total Surface Area (m2
) 254
SuDS 2 Total Surface Area (m2
) 359
Optimisation Objectives and Penalty Function SuDS 3 Total Surface Area (m2
) 743
Total Surface Area (m2
) 1,357
Type Objective Value SuDS 1 Land Value (£ at 2012 value) £31,803
Hydraulics Maximise -0.29% SuDS 2 Land Value (£ at 2012 value) £89,861
Costs Minimise 719,093 SuDS 3 Land Value (£ at 2012 value) £130,084
Penalty Cost Avoid 40,951,441,427.47 Total Land Value (£ at 2012 value) £251,747
Background Calculations - Optimisation Contraints and Penalty Costs Other Controls
Level Penalty Cost Description of KPI Settings
2.5 9,358,715,432.56 Hydraulics Flow Calculation Method (Choose) Muskingum
5000 23,744,725,994.91
180 0.00
10 0.00
10 0.00
10 0.00
10 7,848,000,000.00
10 0.00
No Constraint
50 0.00
50 0.00
50 0.00
100 0.00
100 0.00
100 0.00
40 0.00
40 0.00
40 0.00
allowed No Constraint
allowed No Constraint
allowed No Constraint
40,951,441,427.47
Hydraulics
Land Value
Pollutant
Concentration
at Outlet
(mg/L)
Whole Life
Cost
Location 1
True Value Range
Description
Optimsation
Range
Optimisation
Value
ContraintsDescription of KPI
True Value
SuDS 1 - Dimension 2 (m)
Total Suspended Solids
Hydrocarbons
SuDS 1 - Dimension 1 (m)
should be <=
should be <=
should be <=
should be <=
should be <=
should be <=
Faecal Coliforms
should be <=
Hydraulics
Peak Flow at Outlet (m3
/s)
Total Storage Required (m3
)
Time to Reach Peak Flow (min.)
SuDS 3 - Dimension 1 (m) should be <=
Use of infiltration at location 1 is
Location 2
Location 3
SuDS 1 - Dimension 3 (m)
SuDS 2 - Dimension 1 (m)
SuDS 2 - Dimension 1 (m)
should be <=
should be <=
should be <=
Heavy Metals
Description of Optimisation Objective
Positive if the performance is better than defined targets
Surface Area
Total Nitrogen
WLC (CAPEX, OPEX and Land Value)
Penalty as a results of contraints
should be <=
should be <=
should be >=
Total PhosphorusPollutant
Concentration
at Outlet
(mg/L)
Physical
Restrictions
Infiltration
Use of infiltration at location 3 is
TOTAL Penalty Cost:
isUse of infiltration at location 2
should be <=
should be <=
should be <=
SuDS 2 - Dimension 1 (m)
SuDS 3 - Dimension 1 (m)
SuDS 3 - Dimension 1 (m)
0
2
4
6
8
10
12
14
16
18
20
0 50 100 150 200 250 300
Flow(m3/s)
Duration (Minutes)
Flow Rate at Various Stages of SuDS TreatmentTrain
Inflow (Connection1)
Outflow (Connection 1) -> Inflow
(SuDS 1)
Outflow (SuDS1) -> Inflow
(Connection 2)
Outflow (Connection 2) -> Inflow
(SuDS 2)
Outflow (SuDS 2) -> Inflow
(Connection 3)
Outflow (Connection 3) -> Inflow
(SuDS 3)
Final Outflow at Outlet
Peak Flow Constraint
0
5
10
15
20
25
30
35
0 50 100 150 200 250 300
Volume(m3)
Duration (Minutes)
Storage Requiredat Various Stages of SuDS TreatmentTrain
Storage (Connection 1)
Storage (SuDS 1)
Storage (Connection 2)
Storage (SuDS 2)
Storage (Connection 3)
Storage (SuDS 3)
Storage (TOTAL)
0
5
10
15
20
25
30
35
Total
Nitrogen
Total
Phosphorus
Total
Suspended
Solids
Hydrocarbo
ns
Heavy
Metals
Pollutant Concentration (mg/L)
Concentration
(Inlet)
Concentration
(Regulation
Targets)
Concentration
(Outlet)
£0
£100,000
£200,000
£300,000
£400,000
£500,000
£600,000
SuDS1 SuDS2 SuDS3
Cost Summary
CAPEX OPEX (over 50 years) Land Value Whole Life Cost (over 50 years)
Prototyping using Spreadsheet
Parameters
Objectives
Performance
Measures
Optimisation
Constraints
Graphical
Outputs

13. Framework – Parameters
jo-fai.chow@microdrainage.co.ukSlide (12/21)
Choices of
SuDS Techniques
Sizing Parameters
(e.g. Width, Length,
Diameter, Depth etc)
Infiltration
Parameters
(side and base)

14. Framework – Constraints
jo-fai.chow@microdrainage.co.ukSlide (13/21)
• Hydraulic
Performance
• Water Quality
– Discharge Consent
• Physical limitations
• Infiltration suitability

15. Framework – Graphical Outputs
jo-fai.chow@microdrainage.co.ukSlide (14/21)
Final Outflow
Storage
Pollutant Concentration
(Inlet, Discharge Consent,
Final outlet)
Costs

16. Optimisation Objective 1 – Performance
jo-fai.chow@microdrainage.co.ukSlide (15/21)
0
2
4
6
8
10
12
14
16
18
20
0 50 100 150 200 250 300
Flow(m3/s)
Duration (Minutes)
Flow Rate at Various Stages of SuDS Treatment Train
Inflow (Connection1)
Outflow (Connection 1) -> Inflow
(SuDS 1)
Outflow (SuDS1) -> Inflow
(Connection 2)
Outflow (Connection 2) -> Inflow
(SuDS 2)
Outflow (SuDS 2) -> Inflow
(Connection 3)
Outflow (Connection 3) -> Inflow
(SuDS 3)
Final Outflow at Outlet
Peak Flow Constraint
0
2
4
6
8
10
12
14
16
18
20
0 50 100 150 200 250 300
Flow(m3/s)
Duration (Minutes)
Flow Rate at Various Stages of SuDS Treatment Train
Target Delay (i.e. Constraint)
Target Peak Outflow (m3/s)
Maximise
Minimise
Optimise

17. Optimisation Objective 2 – Costs
jo-fai.chow@microdrainage.co.ukSlide (16/21)
£0
£100,000
£200,000
£300,000
£400,000
£500,000
£600,000
SuDS1 SuDS2 SuDS3
Cost Summary
CAPEX OPEX (over 50 years) Land Value Whole Life Cost (over 50 years)
CAPEX (Construction Cost)
OPEX (Maintenance Cost over 50 years or 100 years)
Land Value (unit cost x surface area)
Whole Life Cost

18. GANetXL Video Demo
Savić, D.A., Bicik J. and Morley M.S. (2011). GANetXL: A DSS generator for multiobjective optimisation of
spreadsheet-based models, Environmental Modelling & Software, Vol. 26, 551-561.
jo-fai.chow@microdrainage.co.ukSlide (17/21)

19. Exploring the Trade-off
jo-fai.chow@microdrainage.co.ukSlide (18/21)
Least cost solution which
just satisfies the hydraulic
performance requirements
Solution with better
hydraulic performance
but a higher cost
Most relevant for
decision makers

20. Exploring the Trade-off
jo-fai.chow@microdrainage.co.ukSlide (19/21)
0
2
4
6
8
10
12
14
16
18
20
0 50 100 150 200 250 300
Flow(m3/s)
Duration (Minutes)
Flow Rate at Various Stages of SuDS TreatmentTrain
Inflow (Connection1)
Outflow (Connection 1) -> Inflow
(SuDS 1)
Outflow (SuDS1) -> Inflow
(Connection 2)
Outflow (Connection 2) -> Inflow
(SuDS 2)
Outflow (SuDS 2) -> Inflow
(Connection 3)
Outflow (Connection 3) -> Inflow
(SuDS 3)
Final Outflow at Outlet
Peak Flow Constraint
0
5
10
15
20
25
30
0 50 100 150 200 250 300
Volume(m3)
Duration (Minutes)
Storage Requiredat Various Stages of SuDS TreatmentTrain
Storage (Connection 1)
Storage (SuDS 1)
Storage (Connection 2)
Storage (SuDS 2)
Storage (Connection 3)
Storage (SuDS 3)
Storage (TOTAL)
0
5
10
15
20
25
30
35
Total
Nitrogen
Total
Phosphorus
Total
Suspended
Solids
Hydrocarbo
ns
Heavy
Metals
Pollutant Concentration (mg/L)
Concentration
(Inlet)
Concentration
(Regulation
Targets)
Concentration
(Outlet)
£0
£100,000
£200,000
£300,000
£400,000
£500,000
£600,000
SuDS1 SuDS2 SuDS3
Cost Summary
CAPEX OPEX (over 50 years) Land Value Whole Life Cost (over 50 years)
Final Outflow
Total Storage
Final Pollutant Conc.
Costs
0
2
4
6
8
10
12
14
16
18
20
0 50 100 150 200 250 300
Flow(m3/s)
Duration (Minutes)
Flow Rate at Various Stages of SuDS TreatmentTrain
Inflow (Connection1)
Outflow (Connection 1) -> Inflow
(SuDS 1)
Outflow (SuDS1) -> Inflow
(Connection 2)
Outflow (Connection 2) -> Inflow
(SuDS 2)
Outflow (SuDS 2) -> Inflow
(Connection 3)
Outflow (Connection 3) -> Inflow
(SuDS 3)
Final Outflow at Outlet
Peak Flow Constraint
0
5
10
15
20
25
30
0 50 100 150 200 250 300
Volume(m3)
Duration (Minutes)
Storage Requiredat Various Stages of SuDS TreatmentTrain
Storage (Connection 1)
Storage (SuDS 1)
Storage (Connection 2)
Storage (SuDS 2)
Storage (Connection 3)
Storage (SuDS 3)
Storage (TOTAL)
0
5
10
15
20
25
30
35
Total
Nitrogen
Total
Phosphorus
Total
Suspended
Solids
Hydrocarbo
ns
Heavy
Metals
Pollutant Concentration (mg/L)
Concentration
(Inlet)
Concentration
(Regulation
Targets)
Concentration
(Outlet)
£0
£100,000
£200,000
£300,000
£400,000
£500,000
£600,000
SuDS1 SuDS2 SuDS3
Cost Summary
CAPEX OPEX (over 50 years) Land Value Whole Life Cost (over 50 years)
Final Outflow
Total Storage
Final Pollutant Conc.
Costs
0
2
4
6
8
10
12
14
16
18
20
0 50 100 150 200 250 300
Flow(m3/s)
Duration (Minutes)
Flow Rate at Various Stages of SuDS TreatmentTrain
Inflow (Connection1)
Outflow (Connection 1) -> Inflow
(SuDS 1)
Outflow (SuDS1) -> Inflow
(Connection 2)
Outflow (Connection 2) -> Inflow
(SuDS 2)
Outflow (SuDS 2) -> Inflow
(Connection 3)
Outflow (Connection 3) -> Inflow
(SuDS 3)
Final Outflow at Outlet
Peak Flow Constraint
0
5
10
15
20
25
30
0 50 100 150 200 250 300
Volume(m3)
Duration (Minutes)
Storage Requiredat Various Stages of SuDS TreatmentTrain
Storage (Connection 1)
Storage (SuDS 1)
Storage (Connection 2)
Storage (SuDS 2)
Storage (Connection 3)
Storage (SuDS 3)
Storage (TOTAL)
0
5
10
15
20
25
30
35
Total
Nitrogen
Total
Phosphorus
Total
Suspended
Solids
Hydrocarbo
ns
Heavy
Metals
Pollutant Concentration (mg/L)
Concentration
(Inlet)
Concentration
(Regulation
Targets)
Concentration
(Outlet)
£0
£100,000
£200,000
£300,000
£400,000
£500,000
£600,000
SuDS1 SuDS2 SuDS3
Cost Summary
CAPEX OPEX (over 50 years) Land Value Whole Life Cost (over 50 years)
Final Outflow
Total Storage
Final Pollutant Conc.
Costs
Least Cost
Acceptable Performance
Most expensive
Best Performance

21. Exploring the Trade-off
jo-fai.chow@microdrainage.co.ukSlide (20/21)
• How about more objectives?
– Parallel coordinates
Cost
Performance
Social Impact
Risk etc …

22. Summary & Future Works
jo-fai.chow@microdrainage.co.ukSlide (21/21)
• Future Works
– More objectives and
trade-off
• Social Impact
• Potential Flood Risk &
Consequence
• Carbon Cost
– More real data
– More discussion with
practitioners
– Integration with
commercial software
• Summary
– Motivation
• Better decision
support for drainage
design
– Prototype DSS for
SuDS selection
– GANetXL Demo:
• Trade-off between
Hydraulic
Performance and
Whole Life Cost

23. The End
jo-fai.chow@microdrainage.co.uk
Danke!
STREAM: www.stream-idc.net
Twitter: @microdrainage
Blog: pipedup.wordpress.com
GANetXL:
http://emps.exeter.ac.uk/engineering/research/cws/resourc
es/ganetxl/

24. Supplementary Slides
jo-fai.chow@microdrainage.co.uk
• Percentage Removal Table (CIRIA)
Lower Upper Lower Upper Lower Upper Lower Upper Lower Upper Lower Upper
Pervious Pavements 60 95 70 90 50 80 65 80 60 95
Green Roofs 60 95 60 90
Bioretention 50 80 50 80 50 60 40 50 50 90
Sand and Organic Filters 80 90 50 80 50 80 25 40 40 50 50 80
Grassed Filter Strips 50 85 70 90 10 20 10 20 25 40
Grassed Swales (Dry) 70 90 70 90 30 80 50 90 80 90
Grassed Swales (Wet) 60 80 70 90 25 35 30 40 40 70
Infiltration Trench / Soakaway 70 80 60 80 25 60 60 90 60 90
Filter Drains 50 85 30 70 50 80
Infiltration Basin 45 75 60 70 55 60 85 90
Extended Detention Ponds 65 90 30 60 20 50 20 30 50 70 40 90
Wet Ponds 75 90 30 60 30 50 30 50 50 70 50 80
Stormwater Wetlands 80 90 50 80 30 40 30 60 50 70 50 60
On-/Off-line Storage 0 0 0 0 0 0 0 0 0 0 0 0
Oil Separator 0 40 40 90 0 5 0 5
Others (Product-specific)
SuDS Technique
Percentage removal of pollutants of concern
TSS Hydrocarbons Total Phosphorous Total Nitrogen Faecal coliforms Heavy Metals

25. Supplementary Slides
jo-fai.chow@microdrainage.co.uk
• Urban Stormwater Concentration