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Human systems vulnerability – exposure and susceptibility to suffer damage
The organization of human society was always linked to the cycle of water. One of the consequences of this is that the majority of civilisations settled near water-bodies. The first aspect of the vulnerability of assets to floods is their potential to be reached by floodwater, i.e. exposure. Unfortunately, great percentage of city areas is still located inside flood zones, increasing the exposure of people and goods to floods, e.g. Netherlands, Bangladesh. The concept of vulnerability is complex and controversial, and goes far beyond the simple concept of exposition of assets to floods. The vulnerability also represents the susceptibility of the assets to suffer consequences due to this exposition (Barroca et al., 2006; Green et al., 1994; Messner and Meyer, 2006). Furthermore, the impacts of the exposition of values to floodwater depend on the characteristics of both, the assets and the hazard. Even though each asset or system has its own characteristics, we can consider that the vulnerability concept is also intrinsically linked to the hazard characteristics. The terms of direct, material or physical vulnerability are used to define the probability or likelihood of assets to suffer consequences linked to the immediate contact with the hazardous phenomenon. Indirect and functional vulnerability are used to determine the likelihood of assets to be indirectly affected by a hazard or to induce other impacts. Both terms contain hazard and vulnerability characteristics. In this context, the flood risk is considered as the combination of hazard and vulnerability (Figure 1.1).
Flood effects, consequences and damage
Floods generate several effects in the environment reached by them, in a direct or indirect way. Torterotot (1993) introduced an interesting differentiation between flood effects, impacts and damage. Some of the effects of floods are “perceived” by men, others are not. In the same way, some effects are “felt” and others do not. The meaning of the words “perceive”, i.e. became aware or conscious of, and “feel”, i.e. be affected by, express the basic difference between “effect”, “impact” and “damage”. The effects of foods are defined as all objective changes generated by floods, on natural, human and economical systems. Impacts are the effects perceived by society, or effects that society attaches some importance. Damage is impacts with anthropogenic added values, in a monetary or subjective way. The following scheme represents these concepts (Figure 1.2).
Flooding is considered the first damaging natural hazard in the world (Messner et al., 2007). Damaging floods are floods that have adverse impacts on the social system, the natural system or the built environment (Merz et al., 2010a). Floods can also have positive consequences, like the fertilization of floodplains in non-controlled rural areas, the increase or maintenance of biodiversity in natural areas, the reinforcement of social links between affected people in urban or rural context, etc. The aggregation of values to consequences of floods includes a lot of subjectivity, especially when making the difference between positive and negative consequences of floods. They can be considered negative and positive at the same time, depending on the point of view. For example; dwelling structure material loss caused by a flood event is felt by the dwelling owner as a negative consequence of the flood once the owner will be supposed to expend monetary resources in order to repair or replace it; nevertheless, the civil engineering enterprise that will be in charge of the house repair or replacement works will perceive the consequence of flooding as a benefit once it will probably makes profit on it. Therefore, when using the term of flood damage, it is crucial to specify who suffer the damage and who pay for it.
Damaging processes and influencing factors
Assets exposed to floods can be damaged in three different ways (Green et al., 2011): (1) physical processes (e.g. mechanical damage as a result of impact); (2) chemical processes (e.g. corrosion) and (3) biological processes (e.g. mould). These processes depend on several characteristics of both, the flood hazard and the vulnerability of assets. In the context of flood analysis, several characteristics of floods can influence damage (Table 1.2). The characteristics of assets influencing damage in case of floods depend on the type of the asset exposed to the flood hazard. We present some examples in the following table (Table 1.3).
In addition to the three damaging processes elucidated, damage can occur on systems that are not directly exposed to floodwaters. This damage is therefore linked to the damage potential of structures touched by floodwater, their dysfunction and the degree of dependence on other elements to these structures (Narbonne, 2005).
Flood losses are commonly classified into four categories: direct tangible, indirect tangible, direct intangible and indirect intangible (Hubert and Ledoux, 1999; D4E, 2007; Penning-Rowsell and Chatterton, 1977; Merz et al., 2010b; Torterotot, 1993; Messner et al., 2007; DNRM , 2002). This classification is correlated to two aspects: the first one is the cause of the loss or “damaging way”, i.e. direct and indirect damage, and the second one is the possibility to associate a monetary value to the losses, i.e. tangible or intangible damage.
• Direct damage is due to all variety of effects caused by the immediate contact of floodwater with humans, goods or the environment. These impacts are easily felt by the society exposed by the event once it implies direct socio-economic losses.
• Indirect damage can have two different causes: (1) it is a consequence of direct damage that induced the dysfunction of systems, e.g. the interruption of gas or electricity delivery, traffic disruption etc; (2) it is linked to the measures adopted to reduce direct damage, e.g. rescue services. This damage cannot be felt and quantified immediately after the flood event.
• Tangible damage is losses “easily” expressed in monetary terms. It is therefore damage that the society is able to aggregate an economic value, e.g. the destruction of a building, the total loss of good, etc.
• Intangible damage is losses generated to non-marketable goods. This damage is hardly associated to a monetary value. The economic value of the loss is subjective and hard to evaluate. It is considered as a non-valuable cost, e.g. loss of life.
Human systems resilience to floods
The term resilience is originally employed in physical science to describe the return of a material to its original form after a deformation. The use of this term in the context of natural hazards and flood risk management is recent, and it merits a special attention (Berkes, 2007; Turner II, 2010; Dauphiné and Provitolo, 2007; Klein et al., 2003; Adam, 2007; Fuchs, 2009). Greenberg et al. (2007) defined resilience as the adaptations within an economy that speed recovery from a shock and avoid some losses. Therefore, the resilience of a system to floods refers to the potential of this system to recover from perturbations caused by flood hazard events reducing the long-term negative consequences of them. The understanding of this aspect of the risk is proving to be essential for flood management purposes. The work of Kuhlicke et al. (2012) makes a description of several aspects of this concept related to natural hazards. In this purpose, the flood risk could also be considered as a combination of hazard, vulnerability and resilience. This concept of risk can be used to include functional aspects of the human system exposed to floods and is extremely useful for appreciating indirect consequences of floods.
Flood risk management
The main goal of flood management is to mitigate global damage caused by floods of different natures, e.g. human loss, social disruption and economic damage. For more details, refer to Plate (2002). Flood control systems were developed for a long time in our society, e.g. in the Nil River, lots of instruments and professionals were exclusively employed for observing and measuring the risk (Viollet, 2004; Nordon, 1991). Basically, two alternatives were used with this purpose: (1) the construction of hydraulic structures in order to reduce hazard, e.g. Dutch dams, Rhine dikes, and (2) the adaptation of the assets in order to resist floods, e.g. Amazonian riverside residents build their habitats elevated by pillars, so that they can live near the rivers without being vulnerable to floodwater. Even though the measures to reduce vulnerability are currently preferred, the control of hazard was and is still the measure more frequently adopted in flood risk alleviation projects. The term of flood control has progressed as well as the techniques employed to deal with floods. It is recent that we started to replace the “flood control” approaches by “flood risk management” approaches (Merz et al., 2010b).
Types of flood management measures
Several measures are used in flood management plans are used to reduce damage induced by floods. In order to reduce the flood risk, these measures objective to reduce the flood probability or to reduce the flood losses (Green et al., 2011). Different kinds of intervention strategies can take place with this purpose. As described by Torterotot (1993), we can make the difference between “structural” and “non-structural” measures. Basically, structural measures concern interventions on the physical world and non-structural measures focus on the behaviour of individuals. Different strategies can be found in the work of Bouwer et al. (2011). Furthermore, these measures can be used to reduce the risk adopting actions that can take place in three distinct temporal contexts: (1) to reduce the damage potential acting before the flood event, (2) to concentrate on the actions in order to reduce damage during the event and (3) to repair the damage after the event.
Preventive measures can be used to reduce immediately the actual risk and/or to reduce the risk in a long-term perspective. In this type of measure, the objective is to reduce the risk by mitigating hazard and/or the vulnerability of assets to suffer damage. The reduction of flood hazards is the more often used in management schemes (Kreis, 2004). These strategies are structural measures because they pass by the construction of infrastructure, e.g. deviation and rectification of water-bodies, dikes, dams, retention basins, etc. These measures imply transformations on the natural environment. Another solution in terms of risk reduction in a preventive way is the reduction of the vulnerability of assets exposed hazards. In this context, structural measures on the buildings and infrastructure can be adopted in order to reduce their susceptibility to suffer damage; and/or non-structural measures can be employed in order to modify the behaviour of the users of buildings, e.g. information, education and regulation, so that they become able to reduce their own vulnerability. The control of urbanisation is one of the key strategies for flood risk management in a long-term perspective. In France, the PPRi10 (DDAF, 2006) is an example of this kind of strategy.
Crisis management serves to deal with the mitigation of damage through actions that take place just before, during and just after flood events. Rescue organization, evacuation plans and warning systems are the base of this management solution (Penning-Rowsell et al., 2000; Penning-Rowsell and Green, 2000b; Parker et al., 2007b; Kreibich and Merz, 2007; Parker et al., 2007a; Drobot and Parker, 2007).
Stakeholders, risk knowledge and decision-making process
Different sectors are involved with the management of flood risks. The public sector is expected to ensure the security of the population as well as the stability of the economy. Therefore, the public sector is the first sector linked to flood management processes. Different scales of management can be adopted, from the national one, passing by the basin to the local scales (Merz et al., 2010b; Messner and Meyer, 2006; Messner et al., 2007; Büchele et al., 2006; de Moel et al., 2009; Merz et al., 2007). Once the management of the flood risk involves restrictions concerning the land-use occupation, different levels of public interests are confronted. Furthermore, public interests are confronted with private ones. On the one hand, local authorities are interested in developing the local economy, which sometimes is contradictory with land-use restrictions for flood risk management purposes. On the other hand, at the national scale we are interested to reduce the vulnerability of the territory in order to reduce the global risk. Insurance companies also play an important role on flood risk management, acting on the interface of public and private interests. The flood risk can also strongly impacts real estate/property market as well as regulation urbanisation, both affecting private interests (Shilling et al., 1989; Daniel et al., 2009).
The management of this complex phenomenon, which has both natural and human origins and confounds several levels of interests, constitutes a great challenge in contemporary society. The understanding of the flood hazard, the knowledge about the vulnerability of the territory and the quantification of the risk are crucial to flood risk managers. “In order to have available an effective tool for information, as well as a valuable basis for priority setting and further technical, financial and political decisions regarding flood risk management, it is necessary to provide for the establishing of flood hazard maps and flood risk maps showing the potential adverse consequences associated with different flood scenarios” [L 288/28, statement 12] (European Parliament Council, 2007). Several scientific works and projects were developed during the last decades in order to better understand the flood risk for supporting flood managers (Begum et al., 2007; European Parliament Council, 2007; Handmer, 1987; Klein et al., 2003; Kreibich and Thieken, 2009; Kundzewicz et al., 2010; Merz et al., 2010a; NRC , 1995; Pender, 2006; Penning-Rowsell and Fordham, 1994; Plate, 2002; Schanze et al., 2006; Schumann, 2011).
The evaluations of flood consequences and reduction potential can be useful to improve budget allocation transparency, justifying public investments and demonstrating their appropriateness (Messner et al., 2007). These evaluations also make possible to compare and rank projects for budget allocation. As highlighted by the study of CEPRI (2008), requests of public funds for flood risk alleviation projects are increasing, which highlight that greater efforts should be done in order to prioritize the relevant ones. For a long time, flood alleviation projects in France have been built just after big catastrophes without considering solid economic evaluations for supporting flood management decision-making process (D4E, 2007). This scenario is still quite common, all over the world, however, this situation is changing, and cost-benefit analysis tends to be more frequently employed.
Table of contents :
PART I – STATE OF THE ART AND RESEARCH QUESTION
Chapter 1. Concepts related to risk management and flood damage estimations
2. Flood risk
2.1. Floods – natural hazards?
2.2. Human systems vulnerability – exposure and susceptibility to suffer damage
2.3. Flood effects, consequences and damage
2.4. Flood risk – conjunction of loss and probability
2.5. Human systems resilience to floods
3. Flood risk management
3.1. Types of flood management measures
3.2. Stakeholders, risk knowledge and decision-making process
4. The assessment of potential flood damage
4.1. Actual and potential damage assessments
4.2. Conceptual methods to estimate damage potential
4.3. Deterministic methods to estimate damage potential
5. The deterministic evaluation of potential flood damage
5.1. Economic evaluation principles
5.2. Flood damage evaluation process
5.3. Results of flood damage evaluations
6. Chapter summary
Chapter 2. Uncertainty on the ‘foundation’ of potential flood damage estimations
2. Modelling processes and uncertainties behind the evaluation
2.1. The “pillars” of flood damage assessments
2.2. The “foundation” of the evaluation, source of uncertainties
2.3. Role of uncertainty on the evaluation results
2.4. Scales of evaluation and the liability of the evaluation
3. Identification of the research question
3.1. Pre-study for flood damage evaluations
3.2. The liability of the evaluation – a feasibility issue?
4. Thesis question and research framework
4.1. Strategies of evaluation
4.2. Propagation of uncertainty through the evaluation
4.3. Measure results variability
4.4. Application of the framework
5. Chapter summary
Chapter 3. Development of a GIS-based method to evaluate potential flood damage
2. The role of GIS in flood risk assessments
2.1. Representation of data in a GIS
2.2. GIS in hazard modelling/mapping
2.3. GIS in vulnerability assessment/mapping
2.4. GIS in damage potential evaluation/mapping
3. General GIS-based method principles
3.1. Step 1: assessing the assets flooding potential
3.2. Step 2: calculation of assets damage potential
3.3. Step 3: calculation of expected annual damage
3.4. Implementation of the method in a GIS platform
4. Using the GIS-based method to estimate potential flood damage
4.2. Pre-processing functions
4.3. Model RUN parameters
5. Conclusions and perspectives
PART II – VARIABILITY OF POTENTIAL FLOOD DAMAGE ESTIMATIONS
Chapter 4. Case studies: the towns of Holtzheim and Fislis
1. Localization of case-studies
2. Holtzheim in the Bruche lower valley
3. Fislis in the Ill upper valley
Chapter 5. Hydrological analyses of flood discharges and frequencies
1.1. Flood frequency analyses and flood risk evaluation
1.2. Objective of this chapter
2. Uncertainty analysis method
2.1. Flood frequency analysis
2.2. Flood risk assessment
2.3. Case study and datasets
3.1. Impact of hydrological CI on hazard maps
3.2. Impact of hydrological CI on assets exposition and damage
3.3. Impact of hydrological CI on flood EAD and risk maps
3.4. Results general discussion
Chapter 6. Hydraulic modelling and flood mapping
1.1. Flood maps
1.2. Hydraulic modelling and hazard mapping
1.3. Uncertainty sources
2. Hydraulic uncertainty, flood maps and damage estimates
2.1. Case study and datasets used for the simulations
2.2. Differences between modelling scenarios
2.3. Flood modelling and hazard mapping
2.4. Damage estimation
3.1. Impact of hydraulic modelling choices on hazard maps
3.2. Impact of hydraulic modelling on damage estimates
3.3. Result discussions
Chapter 7. Asset exposure and vulnerability assessments
1.1. Damage-influencing factors
1.2. Assessment of the vulnerability assets
1.3. Uncertainties linked to vulnerability assessments
2. Variability direct damage estimations to buildings
2.1. Basis for damage estimations
2.2. Available datasets for vulnerability analyses
2.3. Interviews and field surveys
2.4. Different methods used to estimate the vulnerability of buildings to floods
2.5. Damage estimations
4. Results discussion and recommendations
4.1. Prioritization of areas for investments
4.2. Selection of flood risk alleviation measures
4.3. Estimation of global costs of damage for budget organization
5. Chapter conclusions
Chapter 8. Asset value estimations and susceptibility models
1.1. Susceptibility analyses
1.2. Damage models
1.3. Using existing damage functions
1.5. Validation of damage functions
2. Influence of methods on damage potential estimates
2.1. Selection of damage functions
2.2. Calibration of damage functions
2.3. Actual damage analysis
3. Cumulating uncertainty sources for uncertainty analyses
4. Chapter conclusions
Chapter 9. Cascade of uncertainties in flood damage estimations
2.1. Definition of evaluation strategies
2.2. Implementation of the different assessment strategies
2.3. Propagation of uncertainties
3.1. Global uncertainty of assessments
3.2. The role of the analysis scale
3.3. Discussion on the results
4. Conclusions and outlook
PART III – THE COMPLEXITY OF FLOOD INDIRECT DAMAGE AND RESILIENCY
Chapter 10. Estimation of potential damage and dysfunction to network infrastructures
1.2. Flood consequences evaluation
1.3. Resilience and network infrastructures
1.4. Objectives of this chapter
2. Method principles
2.1. STEP 1: Data collection and interviews organisation
2.2. STEP 2: Damage-dysfunction processes
2.3. STEP 3: Quantification of damage and dysfunctions
2.4. Case study
3.1. Damage-dysfunction matrices
3.2. Evaluation of damage and dysfunctions
4. Discussion of results
5. Conclusions and perspectives
LIST OF REFERENCES