Optimisation of flood risk management strategies
- Developments in FRMRC
Michelle Woodward1,2, Ben Gouldby1 and Zoran Kapelan2
1
HR Wallingford
2 University
of Exeter
International workshop on the science of asset management
9th December 2011
Presentation Overview
- Decision Support system overview
- Description of each component
-
Flood risk management intervention strategies
Risk analysis model
Cost Model
Optimisation Algorithm
Decision support
- Case study on the Thames Estuary
Page 2
Decision Support System
Description of
flooding system
(Present day)
(S-P-R)
External constraints
and objective functions
(preferences)
Flood System Risk Analysis Tools
(e.g. simplified RASP)
External
futures
User input
Autonomous future change
(e.g. climate / socio-economic /
deterioration etc)
Optimisation Engine
Optimise flood risk management
options
Output
Expenditure / Option Cost Tools
(cost functions for improvement,
reconditioning and replacement,
channel and beach management etc)
Costs
Page 3
Optimal option
sets and
decision
support
Decision Support System INPUT
Intervention Strategy constraints:
- Length of intervention strategy (e.g. 10yrs, 15yrs, 20yrs…)
- Number of time steps (e.g. 1, 2, 3…)
- Length of time steps (e.g. 5yrs, 10yrs …)
- Types of intervention measures (e.g. Structural interventions, flood
proofing)
- Constraints between time steps (e.g. Account for previous epochs)
- Constraints to ensure realistic measures (e.g. max height increase)
Selection of Objective Functions
- Single objective (e.g. NPV, BCR)
- Multi objective (e.g. Benefit, Cost, Loss of life …)
Page 4
Decision Support System
Description of
flooding system
(Present day)
(S-P-R)
External constraints
and objective functions
(preferences)
Flood System Risk Analysis Tools
(e.g. simplified RASP)
External
futures
User input
Autonomous future change
(e.g. climate / socio-economic /
deterioration etc)
Optimisation Engine
Optimise flood risk management
options
Output
Expenditure / Option Cost Tools
(cost functions for improvement,
reconditioning and replacement,
channel and beach management etc)
Costs
Page 5
Optimal option
sets and
decision
support
Flood risk model
Utilises a structured definition of the flood system
(For a more detailed description see Hall et al 2003., and Gouldby et al 2008.)
Page 6
Intervention measures implemented in risk model
SOURCE
Climate Change Scenarios
Defence maintenance
Raise crest level of
defence
PATHWAY
Widen base of
defences
Set back defences
Flood warnings
Socio Economic Scenarios
RECEPTOR
Flood proof properties
Page 7
Simplified risk model
Strategies evaluated using simplified RASP
Page 8
EA
£3, D
900
EA
£2, D
000
5
6
7
8
9
10
11
12
13
14
15
1
0
0
0
0
0
0
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0
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0
0
0
0
0
2
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
3
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
4
0
0
0
0
0
0
0
0
0
0
0
0
0
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0
5
0
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0
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0
0
0
0
1
6
0
0
0
0
0
0
0
7
0
0
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0
0
0
0
8
0
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0
0
0
0
0
10
0
0
0
0
11
0
0
0
12
0
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13
0
14
15
97.97%
E
£60 AD
, 80
0
E
£26 AD
, 00
0
4
E
£71 AD
, 10
0
E
£70 AD
, 70
0
3
E
£46 AD
, 90
0
E
£60 AD
, 70
0
2
EA
£2, D
200
E
£ 1 4 AD
8,9
00
1
>20,000 goes to 5
E
£ 1 2 AD
8,8
00
E
£ 1 4 AD
2,6
00
Strategy
E
£73 AD
, 10
0
E
£ 1 4 AD
8,3
00
EAD
£33,700
EAD
£145,800
EAD
£141,300
EAD
£149,000
EAD
£60,400
EAD
£70,700
EAD
£26,500
EAD
£4,700
EAD
£1,200
EAD
£72,200
EAD
£125,900
EAD
£1,900
EAD
£43,300
EAD
£70,800
EAD
£60,100
E
£36 AD
, 40
0
Strategies evaluated using Full RASP
Model approximation – replaced Monte-Carlo
simulation with an average volume approach
Number of inundation simulations from:
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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0
0
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0
0
0
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0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
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0
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0
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0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
0
0
0
1
0
0
0
0
0
0
0
0
0
0
Ok For optimisation?
Decision Support System
Description of
flooding system
(Present day)
(S-P-R)
External constraints
and objective functions
(preferences)
Flood System Risk Analysis Tools
(e.g. simplified RASP)
External
futures
User input
Autonomous future change
(e.g. climate / socio-economic /
deterioration etc)
Optimisation Engine
Optimise flood risk management
options
Output
Expenditure / Option Cost Tools
(cost functions for improvement,
reconditioning and replacement,
channel and beach management etc)
Costs
Page 9
Optimal option
sets and
decision
support
Cost Model
Flood Defence
No
Fluvial Defence
Type 1 :
Vertical Wall
Type 2 :
Slope or
Embankment
Yes
Tidal?
Type 3 :
High Ground
Type 4 :
Culverts
Coastal Defence
Type 5 :
Vertical Seawall
Type 6 :
Sloping Seawall
General Costs (%)
Maintenance /
Construction Costs
(see Figure 4.2 for an
example)
Non Productive Site Salaries
Site Staff Expenses
Plant Maintenance
Transport Costs
Extra Labour Costs
Small Tools
Protective Equipment
Other
Page 10
Temporary Works
Type 7 :
Beach
General Costs (%)
Maintenance /
Construction Costs
Non Productive Site Salaries
Site Staff Expenses
Plant Maintenance
Transport Costs
Extra Labour Costs
Overheads / Mobilisation
Costs
Single Cost Items
Office
Subclass
Description
Office Furniture
10 Expenditure
FP
Office
11 KitchenFP
12
FP,Area
CP
Changing
/ Rest
13
FP,
CP, RP
Phones
/ email
/ fax
14 Water FP
15
FP, CP
16 Items perFP,
CP, RP
Cost
Gang
17 Equipment
FP(0.5/gang)
Surveying
18 Toilet FP, CP
19 Store FP, CP, RP
45
Generator / FP
Fuel
46
FP
Transformer
47
FP, CP
48
FP
Other
49
FP, CP
Heating / Lighting (1 per building)
50
FP
Local Rates
51
FP, CP
Temporary Hard Surfaces
Temporary Portable Surfaces
Plant Hire (2 per gang)
CG
1
2
3
4
5
Slight defect
0.0%
2.5%
12.5%
30.0%
0.0%
General Overheads
General Site Clearance
1.5% of total mobilisation costs
Other Costs
10% of total mobilisation costs
Materials
Turf
Rigid
Rigid
Rigid
Rip-rap
Rip-rap
Rip-rap
Flexible
Flexible
Flexible
Turf
Rigid
Rigid
Rip-rap
Rip-rap
Flexible
Flexible
Moderate defect
0.0%
0.0%
12.5%
30.0%
25.0%
Width
Narrow
Narrow
Narrow
Narrow
Narrow
Narrow
Narrow
Narrow
Narrow
Narrow
Wide
Wide
Wide
Wide
Wide
Wide
Wide
Extensive defect
0.0%
0.0%
0.0%
30.0%
75.0%
Small Tools
Protective Equipment
Other Levee Type 2:
Slopes and
Embankments
Temporary Works
Insurance
Employers Liability
Input defence
Vehicle
subtype
All Risks
Public Liability
Professional Indemnity
Loss of Money
Input current
Fidelity condition of
Other
defence
Security
Input defence
dimensions
Set levels of
work required
based on CG
Construction
Maintenance
Bonds (per annum)
Input additional works
based on height of
defence increase (m)
and defence
dimensions
Flood Defence
Output: quantity of
work required for
defence
Page 11
Cont…
CG
1
2
3
4
5
Decision Support System
Description of
flooding system
(Present day)
(S-P-R)
External constraints
and objective functions
(preferences)
Flood System Risk Analysis Tools
(e.g. simplified RASP)
External
futures
User input
Autonomous future change
(e.g. climate / socio-economic /
deterioration etc)
Optimisation Engine
Optimise flood risk management
options
Output
Expenditure / Option Cost Tools
(cost functions for improvement,
reconditioning and replacement,
channel and beach management etc)
Costs
Page 12
Optimal option
sets and
decision
support
Optimisation Algorithms
Optimisation techniques are beneficial in
flood risk management because
- they can handle a large portfolio of
possible intervention options at different
sequences through time
- they can give consideration to multiple
conflicting objectives
Page 13
Evolutionary Algorithms
- Powerful Search Process
- Based on Darwin’s Theory of Natural Selection
and survival of the fittest
- Methods include:
-
Page 14
Genetic Algorithms
Shuffled Complex Evolution
Ant Colony Optimisation
Multi-Objective Genetic Algorithm
Genetic Algorithm
Single Objective Optimisation: Maximise NPV or
Maximise BCR
START
Generate
initial
population
Multiobjective optimisation: Maximise Benefits and
Minimise Costs
Are
optimisation
criteria
met?
Evaluate
objective
function
Best
individual
Generate new population
RESULT
Mutation
Page 15
Crossover
Selection
Decision Support System
Description of
flooding system
(Present day)
(S-P-R)
External constraints
and objective functions
(preferences)
Flood System Risk Analysis Tools
(e.g. simplified RASP)
External
futures
User input
Autonomous future change
(e.g. climate / socio-economic /
deterioration etc)
Optimisation Engine
Optimise flood risk management
options
Output
Expenditure / Option Cost Tools
(cost functions for improvement,
reconditioning and replacement,
channel and beach management etc)
Costs
Page 16
Optimal option
sets and
decision
support
Decision Support OUTPUT
Single Objective Optimisation:
- Single Optimal Intervention strategy
- Optimised according to chosen objective
Multi Objective Optimisation:
- A trade off curve (Pareto Front) of the
conflicting criteria
- A set of optimal intervention
strategies to support decision makers
Page 17
Objective 2 (to be minimised)
The Pareto Front
Objectiv e 1 (to be minimised)
Page 18
Objective 2 (to be minimised)
The Pareto Front
Objectiv e 1 (to be minimised)
Page 19
Objective 2 (to be minimised)
The Pareto Front
Objectiv e 1 (to be minimised)
Page 20
Case Study on the Thames Estuary
Legend
Tidal flood risk area
Tidal flood defences
River Lee
River Roding
Westminster
Purfleet
Tilbury
Greenwich
Richmond
Gravesend
Page 21
Flood Defence Examples
1.
3.
2.
1. Concrete vertical wall
2. Embankment
3. Sheet-pile vertical wall
Page 22
Results
Strategy
A
B
C
D
E
Page 23
Benefit
£ 000’s
774.8
1211.1
1570.8
1622.8
1643.4
Cost
£ 000’s
67.8
95.8
231.5
327.3
1521.9
NPV
£ 000’s
304.7
1115.3
1339.3
1295.5
121.5
BCR
5.49
12.64
6.78
5.70
10.8
# of
people at
risk
940
24,710
18,860
5,435
785
Summary/conclusions
- Risk models are useful decision support tools
- These models can be simplified for use in optimisation analysis
- Multi-objective optimisation techniques can provide more information to
decision makers
- Multi-objective optimisation techniques are useful tools to automate the
search process given a large range of potential options
- Need to incorporate a greater range of consequences in risk models, loss
of life (hence benefits of flood warning), environmental impacts etc.
Page 24
Dissemination of work
Woodward, M., Gouldby, B., Kapelan, Z., Khu, S. T. & Townend, I.
(2011) Real Options in Flood Risk Management Decision
Making. Journal of Flood Risk Management, 4, 339-349.
Woodward, M., Gouldby, B., Kapelan, Z. & Hames, D. (2011)
Multiobjective Optimisation for Improved Management of Flood
Risk. ASCE Journal of Water Resources Planning and
Management, (In Review).
Woodward, M., Kapelan, Z. & Gouldby, B. (2011) Developing
Flexible and Adaptive Flood Risk Management Options Based
on a Real Options Decision Tree Approach. (In progress)
Page 25