Vulnerability Assessment and Risk Reduction of Water Supply Systems

World Environmental and Water Resources Congress 2010: Challenges of Change. © 2010 ASCE

Vulnerability Assessment and Risk Reduction of Water Supply Systems Mohammad Karamouz F. ASCE1, Sara Saadati2, Azadeh Ahmadi3 1

Research Professor, Polytechnic Institute of NYU, Brooklyn, NY 11021 (at sabbatical from University of Tehran, Tehran, Iran) [email protected] 2 M.Sc., Natural Resources Engineering, Isfahan University of Technology, Isfahan, Iran 3 Department of Civil Engineering, Isfahan University of Technology, Isfahan, Iran

Abstract One of the concerns about future and existing dams is its safety and the possibility of serious accidents including the dam failure, chemical and biological terrorism and natural hazards. Vulnerability is a characteristic of a critical infrastructure’s design, implementation, or operation that renders the basis susceptible to destruction or incapacitation by a threat. Vulnerabilities may consist of flaws in security procedures, software, internal system controls, or installation of infrastructure that may affect the integrity, confidentiality, accountability, or availability of data or services. Vulnerability assessments provide a systematic analysis of the utility’s susceptibility to an attack and the means by which the utility can reduce its risk. This paper reviews categories of vulnerability of the water supply system, and discusses strategies for reducing them. Also, in order to assess the vulnerability, the actions/threats that an adversary could take to keep a wastewater utility from are identified. Then the specific assets (i.e., infrastructure, employees, information, or finances) that may be impacted by the identified threats are identified. After evaluating existing countermeasures, current risks associated with threats and assets are analyzed. Finally additional countermeasures and prioritize based on a risk-reduction analysis are recommended. Keywords: Vulnerability Assessment, Risk Reduction, Water Supply Systems, Threats, Hazards Introduction Water is a fundamental resource for human and economic welfare and modern society depends on complex, interconnected water infrastructure to provide reliable safe water supplies and to remove and treat wastewater. A general water supply system is composed of water sources, raw water transmission pipes, water treatment plants, and water distribution networks. However, these components and subsystems give the greatest opportunities for both natural and humanrelated influences because most of them are spatially diverse and accessible. With respect to this, researchers have identified the potential vulnerable areas during the process of 1 Downloaded 12 Oct 2010 to 128.233.85.20. Redistribution subject to ASCE license or copyright. Visithttp://www.ascelibrary.org

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delivering water from the sources to the customers as (see Figure 1): (1) water sources (e.g., river, reservoir, and wells); (2) water treatment plant that removes impurities and harmful agents and makes water suitable for domestic consumption and other uses; (3) water distribution pipelines that deliver clean water on demand to homes, commercial establishments, and industries; (4) storages (tanks); and (5) other facilities (Haestad et al., 2003)

Figure 1. Elements and vulnerable points in a general water supply system (Source: Haestad et al., 2003) Water supply systems are a combination of natural, technological and socioeconomic elements, which are coordinated adequate service to water users. Water supply systems are designed to get water from aquifers and rivers, store it and distribute if to users under a set of acceptable conditions regarding water quality and quantity. Reliability and vulnerability of water supply systems to water shortages are required parameters to design and operate the systems. Usually, these factors are evaluated with the help of water resources simulation and optimization models, which provide a framework to extract additional information that can be very useful for decision makers. Risk is understood as the probability of certain threats arising that cause damage or impact one or more social agents. Risk is a circumstance that Corresponds to each system under certain conditions. A general water supply system is composed of water sources, raw water transmission pipes, water treatment plants, and water distribution networks. However, these components and subsystems give the greatest opportunities for both natural and human-related influences because most of them are spatially diverse and accessible. Buckel (2000) contends that work must be done to clear up the definition of vulnerability with respect to risk. For example, Emergency Management Australia (1998) defines vulnerability as the degree of susceptibility and resilience of the community and environment to hazards. Blaike et al (1994) defines vulnerability as “the characteristics of a person or group in terms of their capacity to anticipate, cope with, resist, and recover from the impact of a natural hazard”. Vulnerability highlights the notion of susceptibility to a scenario whereas risk focuses on the severity of consequences to a scenario(Ezel, 2004). vulnerability is defined as a property associated with a component, a subsystem, or the overall water supply system to represent the possibility of being influenced by hazards/threats with given likelihoods and severities (Huipeng, 2007)

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2- Hazard and threat In water supply systems, threats/hazards do not necessarily have to be rare or extreme type events. Risk can be high even if hazard is moderate due to high vulnerabilities of components or the system. Therefore, the current study considers threats or hazards as hazardous events that can adversely affect the performance of a water supply system, which includes both natural hazards and human-related threats. Natural hazards and human related threats to a water supply system summarized in Table 1 and Figure 2. Table 1: Natural hazards and human related threats to a water supply system Threats and hazards Natural hazards Earthquake

Flooding Drought Wind

Water born diseases

Severe weather

Human-related threats Cyber threats

Physical threats

Chemical/Biological threats

Consequences Pipe breaks Loss of power Structure collapse Loss of treatment plant Contamination of distribution system Water shortages Water quality problem Flood-induced problems Structure damage Loss of power Sickness Death Loss of public confidence Frozen pipes Outages and leaks High water use Physical disruption of SCADA (supervisory control and data acquisition) network Attacks on central control system to create simultaneous failures Electronic attacks using worms and viruses Network flooding Jamming Disguising data to neutralize chlorine or add no disinfectant, allowing addition of microbes Physical destruction of system’s assets or disruption of water supply is more likely than contamination Loss of water pressure compromising firefighting capabilities and could lead to possible bacterial build-up in the system Potential for creating a water hammer effect by opening and closing major control valves and turning pumps on and off too quickly, which could result in simultaneous main breaks. Heath problems, or death of customers Panic Loss of public confidence

(Source: Grigg, 2003)


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Natural hazards may include earthquakes, floods, hurricanes, landslides, radiological spills, tornadoes, and other windstorms. Many of the problems presented by natural hazards occur because these phenomena are not considered during the conception, design, construction, and operation of the system. The vulnerability analysis described in this document is important for both existing and planned constructions. Evaluation of hazards in the zone or region under study is essential for estimating the vulnerability and possible damage to components. The history of disasters in the region is valuable for such an evaluation. Among the natural hazards, earthquakes, floods, and droughts are three most significant hazards that can cause water utilities damage and great losses (Grigg, 2003). For example, the Kobe’s earthquake of 1995 in Japan had caused over 5,000 deaths and $100 billion in damage with main breaks and damage to pumps and treatment plants. The flood of the 1993 Midwestern had caused more than $15 billion in damage and contaminated water at 250 drinking water treatment plants (Chung., 1996). In so insurance against floods, droughts and earthquakes is an important socioeconomic instrument that protects our communities from major social dislocation.

Figure 2: Hazards and threats to a water supply system


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3- Methods and Materials Systems that are highly exposed, sensitive and less adaptable, are highly vulnerable. The proposed algorithm for developing the strategies to system vulnerability reduction is shown in Figure 2. In order to develop adaptation strategies, at first the systems/elements that are vulnerable to change should be identified. The components of water sources systems should be identification and their vulnerability for natural hazards and threats should be determined. Developing guidelines and checklist to evaluate the system performance in disaster management is very useful. The system readiness could be a function of system performance indices including reliability, vulnerability and resiliency. Vulnerabilities may consist of flaws in security procedures, software, internal system controls, or installation of infrastructure that may affect the integrity, confidentiality, accountability, or availability of data or services. Vulnerability assessments provide a systematic analysis of the utility’s susceptibility to an attack and the means by which the utility can reduce its risk. 3-1-Vulnerability assessment to threats or hazards To give a risk analysis of municipal water distribution system, (Ezell et al .2000) proposed a method based on evaluation of component vulnerabilities which are assessed in terms of exposure and access control. Vulnerability of a water system is defined as V =

n

∑

i=1

(1)

vi

Where vi denotes the vulnerability of a component in the water system, which is determined by vi = α iγ i (2) Where α i is accessibility and subjectively scaled in [0, 1]; γ i is the degree of exposure and subjectively scaled in [0, 1]. A low vulnerability score for a component is an advantage. In this method, vulnerabilities for specific components are subjective (0 to 1) and constructed from an attribute scale. Then vulnerability of the subsystem or the overall system is calculated by Equation (1). With the values of vulnerabilities, a rank order is obtained for a water supply system. In this method only access and exposure are identified as the contributing factors to vulnerability, which makes it more suitable to analyze the vulnerability related to external hazards. However, for internal factors like deterioration of pipes due to changes of surrounding conditions, access and exposure might not be the proper indicators to value vulnerability. (Li et al, 2004) Vulnerability analysis meets five basic objectives: • • •

Identification and quantification of hazards that can affect the system, whether they are natural or derive from human activity; Estimation of the susceptibility to damage of components that are considered essential to providing water in case of disaster; Definition of measures to be included in the mitigation plan, such as: retrofitting projects, improvement of watersheds, and evaluation of foundations and structures.



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Identification components of

Distribution system

Treatment system

Supply system

Identification and analysis of disasters and threats Structural Natural Non-structural

Identification of threats

Identification of disaster

Man-made Quality

Service

Determination of system vulnerability

Structural

Operation Guidelines and checklist preparation

Vulnerability and risk assessment

Assessment and monitoring of system performance

Vulnerability

Resiliency

Reliability

Assessment of system readiness

Strategies for system vulnerability reduction

Figure 3: Proposed algorithm to develop strategies for a water supply system



•

These measures aim to decrease the physical vulnerability of a system’s components; Identification of measures and procedures for developing an emergency plan. This will assist the water service company to supplement services in emergency situations; Evaluation of the effectiveness of the mitigation and emergency plans, and implementation of training activities, such as simulations, seminars, and workshops.

• •

3-2-Vulnerability Assessment of Water Supply Systems The vulnerability assessment provides a framework for developing risk reduction options and associated costs. Water systems should review their vulnerability assessments periodically to account for changing threats or additions to the system to ensure that security objectives are being met. Calculating risk in this manner not only allows for a comparison of different threats based upon their risk score, but also provides a basis for evaluating countermeasures that would be considered for reducing risk. Risk reduction can be achieved by lowering either the probability of the event happening or the criticality of the event, or both. By estimating the reduction in the risk score with each countermeasure considered, and knowing the cost of implementing each countermeasure, a Cost - risk reduction analysis can be performed. The common elements of vulnerability assessment in water supply systems are viewed as follows:

Characterization of the water system, including its mission and objectives, Identification and prioritization of adverse consequences to avoid, Determination of critical assets that might be subject to malevolent acts that could Result in undesired consequences, Assessment of likelihood of such malevolent acts from adversaries, Evaluation of existing counter measures, and Analysis of current risk and development of a prioritized plan for risk reduction.

The complexity of vulnerability assessment ranges on the basis of the design and operation of the water systems. With respect to this, several methods have been developed to perform vulnerability assessment (Mays, 2004) 3-3- Risk Assessment in Water Supply Systems Risk indicates the potential damage or loss of an asset or a compromise in the function of an engineering system. Risk assessment of a water supply system is usually expressed as a process (Figure 4) of identifying threats/hazards, analyzing vulnerabilities of components and system, and evaluating risks of components and system ((Huipeng, 2007)). A risk assessment would be considered effective and comprehensive if this process was conducted completely. 3-4- The Relationship between Risk and Vulnerability Vulnerability is defined as a property associated with a component, a subsystem, or the overall water supply system to represent the possibility of being influenced by hazards/threats with given likelihoods and severities. Risk measure thus represents the


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Figure 4: General procedure of risk assessment in a water supply system (Source: Huipeng, 2007) cumulative effects of frequency and severity of a hazard/threat. Normally, this risk measure is represented as Risk=Likelihood × Severity

(3)

It is obvious that the above definition of risk only considers the influences of threats or hazards. Vulnerabilities of assets are also playing important roles in introducing risks into the water supply system. Therefore, a modified definition of risk is formed as Risk= (Likelihood × Severity) × Vulnerability (4) where likelihood and severity represent the characteristics of a hazard or threat; while vulnerability represents the property of an asset that is influenced by the hazard or threat. In this definition, both hazards/threats and assets are explicitly considered. To give a risk analysis of municipal water distribution system, ( Ezell et al, 2000) proposed a method based on evaluation of component vulnerabilities which are assessed in terms of exposure and access control. Risk assessment methodologies are often employed to help understand what can go wrong, estimate the likelihood and the consequences, and to develop risk mitigation strategies to counter risk. When undertaking risk reduction measures it is also necessary to define the location of a potential hazard, its severity, return period and the probability of expected levels of loss. It is necessary to differentiate between much localized events and national, regional and global impacts.



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4- Case study A water supply reservoir that serves a major city is selected. It supplies 200 cubic meters per year. A schematic of the water supply system is presented in Figure 5. The reservoir is a part of a water system supply that the vulnerability of its components is assessed based on different criteria using questionnaires from experts. The criteria are considered as the distribution, spread (the extend of a physical magnitude), visibility, exposure and recovery. In four levels of qualitative assessment, the components are marked as low, medium, high and very high. The linguistic marks are presented in Table 2. The economic and human losses are considered as the results and shown in Figure 6. The results show the losses from the dam are considerable and action plans are needed for dam vulnerability reduction. The risk reduction strategies for the reservoir include the increasing resistance of its structure, improving the warning systems and limiting of accessible roads to the dam.

Figure 5. A schematic of water transfer from the dam to the city Table 2. Vulnerability assessment of the water supply system components based on different criteria Components

Distribution

Spread

Visibility

Exposure

The river

High

High Low High Medium

Very high Low High High

Very high Medium Medium High

Groundwater dam Reservoirs

Medium Low Low

Transfer channel intake

Very high

High

Low

Pumping station

Low

Medium

Treatment plants

Low

Storage Reservoirs Distribution network

Medium Very high

Surface water resource Raw water reservoirs

Result Economic losses

Recovery

Human losses

Medium

Low

Medium

Medium Low Medium

Low High Low

Low Very high Low

Medium

High

Low

Medium

Medium

High

Medium

Low

Medium

Low

High

Medium

Medium

High

High

Low High

Medium Medium

High High

Low Medium

Low High

Low Medium



Figure 6 . Probable losses for faluier of water system components Figure 7 shows the vulnerability capability based on different criteria for each water supply system components. In order to generate the figures the numbers 1,2,3 and 4 are assigned as low, medium, high and very high as a degree of each criteria. High vulnerability is due to the extent of influence zone (Colored area). Figure 7 shows the dam and distribution network has high vulnerability capability and groundwater resources have low vulnerability capability. Therefore, groundwater is an alternative for water supply while system failure. Also the development of the online monitoring and warning system along the river and the distribution network are recommitted to reduce their risk. Monitoring systems enable continuous monitoring of water quality and quantity in order to control process and emissions just-on-time. Water quality monitoring helps link sources of pollution to a stream quality problem because it identifies specific problem pollutants. Since certain activities tend to generate certain pollutants (e.g., bacteria and nutrients are more likely to come from an animal feedlot than an automotive repair shop), a tentative link might be made that would warrant further investigation or monitoring. After measuring desired parameters the information will be transferred where it is needed e.g. internet, automation system or the use of personnel. It’s also possible to get alarms by SMS when some alarm limit exceeds. Early warning strategy is very important in vulnerability reduction. The objective is towards preventive concepts from responsive strategy which leads to maximize the operational response to an emergency by activating warning systems and using communication systems to minimize the loss of life, damage to housing and infrastructure.


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Recovery

Expose

Recovery

Expose

Distribution 4 3 2 1 0

Distribution 4 3 2 1 0

Area

Identification capability

Area

Identification capability

Figure 7. Vulnerability of water system components based on different criteria 11

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5- Summary and Conclusion This paper reviews categories of vulnerability of the water supply system for natural hazard and threats. The institutional and legal framework necessary for vulnerability reduction comprises several aspects. The cornerstone is a participatory system in which all sectors (government, private sector, civil society, etc.) take measures to prevent and mitigate vulnerability to natural disasters, and to respond when the event occurs. The required framework is two-dimensional. On one side, it must recognize different roles for the different sectors. The second dimension relates to different spheres of action at the time a disaster develops. The institutional framework has the following three basic objectives relating to vulnerability reduction: 1- Timely identification of potential hazards and threats. The objective is to maximize the ability to predict threats. This entails the strengthening and coordination of public and private institutions dealing with information management, telemetry and other forecasting tools. 2- Timely response to emergencies. The objective is to maximize the operational response to an emergency by activating warning systems and using communication systems to minimize the loss of life, damage to housing and infrastructure, etc. 3- Rehabilitation and reconstruction management. The objective is to make the most of all efforts oriented towards reconstruction and rehabilitation. The first step in mitigating hazards and threats– vulnerability reduction – is to recognize the importance of "preventive concepts" rather than "responsive strategy". In other words, addressing hazards and vulnerability "before" rather than "after" events occur. The vulnerability/reduction concept is proactive as it can reduce the probability of loss before it becomes a real threat or a real tragedy, and will minimize the magnitude of damages. REFERENCES Blaikie, P., Cannon, T., Davis, I., and Wisner, B., (1994). At Risk: Natural Hazards, People’s Vulnerability, and Disasters, Routledge, London, UK. Buckle, P. (2000). “Assessing Resilience and Vulnerability in the Context of Emergencies: Guidelines, Victorian Government Publishing Service”. Retrieved October 20, 2002 from www.anglia.ac.uk/geography/radix/ resources/buckleguidelines.pdf. Chung, R. (1996) The January 17, 1995 Hydrogoken-Nanbu., (Kobe) “ Earthquake: Performance of Structures, Lifelines, and Fire Protection Systems”, National Institute of Standards and Technology. Coburn, A.W., Spence, R.J.S., Pomois, A., (1994) “Vulnerability and Risk Assessment”, Second Edition, UNDP Disaster management training programme. Ezell, B.C., J.V. Farr., and I. Wiese., (2000) “Infrastructure Risk Analysis Model.” Journal of Infrastructure Systems, ASCE, Vol.6, No.3, pp.114-122. Ezell, B.C., (2004). Quantifying Vulnerability to Critical Infrastructure Systems, P.H.D Disseration, Department of Engineering Management, Old Dominion University, Norfolk, Va. Ghazizadeh, A., Jalili ghazizadeh, M.R., and A.A, Ghane ., (2008) “Assessment of water transfer system components aspect of passive defense”, 2nd National congress of water and wastewater , Tehran, 6-7 November. (In Persian)


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Grigg, N. S., (2003) “Water Security: Multiple Hazards and Multiple Barriers”, Journal of Infrastructure Systems ASCE, Vol. 9, No. 2, pp. 87. Haimes, Y. Y., (2009). “Risk Modeling, Assessment, and Management”, Wiley, Third Edition, New York, USA. Haimes, Y. Y., Matalas, N. C., Jackson, B. A .,James, F. R., (1998) “ Reducing Vulnerability of Water Supply Systems to Attack”, Journal of Infrastructure System ASCE, Vol. 4, No. 4, pp. 164-177. Haestad, M., Walski, T. M., Chase, D. V., Savic, D. A., Grayman, W., Backwith, S., Koelle, E., (2003) “Advanced Water Distribution Modeling and Management”, Haestad Press, Waterbury, CT USA. Huipeng, L., (2007). “Hierarchical Risk Assessment of Water Supply Systems.”, Ph .D. Disseration, Loughborough University, Leicestershire, Uk. Li, H. and Vairavamoorthy, K.., (2004). “An Object-Oriented Framework for Vulnerability and Risk Assessment of Water Supply Systems”, Proceedings of Decision Support in the Water Industry under Conditions of Uncertainty, EPSRC Research Network Seminar ACTUI2004, University of Exeter, UK, pp. 111-117. Mays, L.W., (2004). “ Water Supply Systems Security, McGraw-Hill Professional Engineering, New York”.


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