thomas pettersson andreas lindhe and lars rosén identification and management of risks in water...

Thomas PetterssonAndreas Lindhe and Lars Rosén

Identification and management of risks in water safety planning

Decision support method using multi-criteria analysis for WSP

Water Safety Conference 2010

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

Presentation outline

Mainly present a stepwise (10 steps) procedure for evaluating and comparing risk-reduction options (providing decision support)

...but, also incorporate the other tools/methods developed within TECHNEAU

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Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

Background

WSP make water utilities to know/understand their system better

Awareness of hazards/hazardous events Prioritization of hazards Risk reduction options suggestions

But, how to compare different measures? Cost effectiveness? Health risk reduction vs. costs of implemented measures Other benefits... (multi-criteria analysis)

Need for applicable tools and method guidance to carry out WSP (provided from the TECHNEAU project)

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Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

Conceptual Structure of the Risk Management Framework and Toolbox in TECHNEAU

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Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

Decision support method in 10 steps

1) Perform a risk ranking (risk identification and estimation, P&C)

2) Identify severe risks (target risks)

3) Identify possible risk-reduction options4) Estimate risk reduction (new P and C values)

5) Define weights6) Calculate the benefit of risk reduction 7) Consider additional criteria (cost, environment etc.)

8) Determine the performance (of different criteria)

9) Calculate total performance score10)Evaluate and compare risk-reduction options

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Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 1: Perform risk ranking

Very high

High

Medium

Low

PR

OB

AB

ILIT

Y

CONSEQUENCE

Identify hazards and estimate the risk in a risk matrix (here 4x4)

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 1: Perform risk ranking

Classes representing relative;Likelihood ( P = 2(Pclass-1) )

Severity ( C = 2(Cclass-1) )

Calculate the risk as a priority number: R = P x C

8 8 16 32 64

4 4 8 16 32

2 2 4 8 16

1 1 2 4 8

1 2 4 8

Quality risk matrix

Consequence value

Pro

babi

lity

valu

e

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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TECHNEAU Hazard Database

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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12. Future risks

The structure of THDB – 12 subsystems

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 1: Perform risk ranking

Identified hazards are estimated (P and C) and added in the risk matrix

#5

#4

#2

#3

#1

Quality vs. Quantity Risks

P: Probability

C1: Quality consequencesC2: Quantity consequences

Risk (R = P x C):R1: Quality risk R2: Quantity risk

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 2: Identify target events

The severe events that must be reduced are called target events

(Here – Quality risks shown in the matrix)

#5

#4

#2

#3

#1

Event# Description P C1 C2 R1 R2

1 Pipe burst 4 4 2 16 8

2 Disinfection failure 8 4 1 32 8

3 Raw water contamination

2 8 2 16 4

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 3: Identify risk-reduction options

Pro

bab

ility

Consequence

Incr

ease

d risk

Preventive options for reduction of probability

Reduction of consequences

Combin

atio

n of p

reve

ntive

and

conse

quence

reduct

ion o

ptions

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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TECHNEAU Risk Reduction Option Database

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 4: Estimate risk reduction

Target

event

Risk Reduction option

P P’ C1C1’

C2C2’

R1R1’

R2R2’

ΔR1 ΔR2

1 1.1 4 4 4 1 2 1 16 4 8 4 12 4

1 1.2 4 1 4 1 2 1 16 1 8 1 15 7

1 1.3 4 2 4 4 2 2 16 8 8 2 8 6

'k k kR R R k = risk type (e.g. quality and quantity risk)

8 8 16 32 64

4 4 8 16 32

2 2 4 8 16

1 1 2 4 8

1 2 4 8

Risk matrix

Consequence value

Pro

babi

lity

valu

e

(Target event #1, with three different options)

New P and C values are estimated representing the situation after the options are implemented

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 5: Define weights

Are the different types of risk (quality vs. quantity) considered equally important or not?

Assign weights (v) to define the relative importance between: quality (health) risks and

quantity (interruption) risks For example:

Quality (1) and quantity (2) risk considered equally important,then v1 = v2 = 0.5

Quality risks considered more important then quantity risks,e.g. v1 = 0.7 and v2 = 0.3

Use v1 = v2 = 0.5 as default values

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 6: Calculate the benefit of risk reduction

Benefit - weigh together the two risk reductions

B = Benefit of each risk reduction option

i = # of risk-reduction

optionOption Bi

1.1 8 (=12· 0.5 + 4·0.5 = 8) 1.2 11 (=15· 0.5 + 7·0.5 =11) 1.3 7 (= 8· 0.5 + 6·0.5 = 7)

1 1 2 2 ...iB R v R v

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 7: Additional criteria

Additional criteria may be included in the analyses

Examples: Costs Environmental effects Goodwill Consumer trust Regulatory complaints ...

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 8: Determine the performance

Based on the calculated risk reduction, cost, etc., a performance score (s) is calculated by normalising the outcomes

Performance score gets a value between 0-1, where 1 is best

E.g. risk-reduction and cost (for the three options):

Option Bi si1 Costi si2

1.1 8 0.73 20 0.8 1.2 11 1 50 0.5 1.3 7 0.64 100 0

Risk reduction: si1 = Bi / max(Bi)

Cost: si2 = 1-Costi / max(Costi)

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 9: Calculate total performance score

Total performance score (si) of option i

i = risk-reduction option wm = Weight determining the relative

importance of criterion m (risk, cost, goodwill, etc...)

Assume w1 = w2 = 0.5 (i.e. risk and cost equally important)

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Step 10: Summarise results, evaluate and compare risk-reduction options

option Benefit, si1

Cost, si2 Score, si R1 R1’ R2 R2’

1.1 0.73 0.80 0.77

1.2 1 0.50 0.75

1.3 0.64 0 0.32

2.1

2.2

2.3

…

OK!

OK!

OK!

OK!

OK!

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Testing the decision support method

The method has been tested in a case study in Bergen

Method also tested in a training seminar in Pretoria (18-19 Oct 2010)

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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Summary and comments

Simple but quite powerful method to get an overview of the decision basis (for different control measures)

The overall aim is to structure the decision problem and provide transparency

This method provides support for a decision, not making decision

“Normally, I don’t believe in academic methods since it is too complicated – but this method I will test as soon as I come home (to my water utility)”

Stated by a South African water director attending the training seminar

Water Safety ConferenceNovember 2-4 2010, Kuching, Malaysia

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RA/RM Publications – TECHNEAU website

All publications are found on the TECHNEAU website

www.techneau.orgunder Publications

Thank you!