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Flood vulnerability assessment of donstream area in Mono basin in Yoto district, south-eastern Togo

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par Abravi Essenam KISSI
University of Lome - Master 2014

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2.2. Flood Vulnerability Factors

The vulnerability of any system (at any scale) is a function of the exposure and susceptibility of that system to hazardous conditions and the ability, capacity or resilience of the system to cope, adapt and/or recover from the effects of those conditions (Smit and Wandel, 2006). Core factors of vulnerability encompass exposure, susceptibility or sensitivity and resilience or coping and adaptive capacities. Exposure generally refers to the extent to which a unit or a system of the assessment (community, city, building) falls within the geographical range of a hazard event (Birkman, 2013, p 25).

According to IPCC (2012a, p 559), exposure describes the presence of people, livelihoods, environmental services, resources and infrastructures or other valuable items in place that could be affected. Exposure to floods could be understood, then, as the presence of valuable items of human-environment, or socio-ecological systems that are present in floods-prone areas. The indicators for this component can be put in two categories; the first one covers the exposure of different elements at risk and the second one gives details on the general characteristics of the flood. While the first category of indicators supplies information about the location, elevation, population density, land-use, their proximity to the river, their closeness to inundation areas, the second category provides information about the frequency of floods in floodplains, their duration and magnitude (Balica, 2007, p 31).

Penning-Rowsell and Chatterton (1977) defines susceptibility as the relative damageability of property and materials during floods or other hazardous events. According to Turner et al. (2003), susceptibility is mainly defined by cross-scale interactions of multiple internal stresses and perturbations. The concept of susceptibility or sensitivity is the vulnerability factor that describes the human-environmental or socio-ecological conditions or current state that can worsen the hazard, or trigger an impact. So, flood susceptibility indicators evaluate the sensitivity of an element at risk before and during a flood event

"figure 3" .

Figure 2 Susceptibility framework

Source: Balica (2007, p 33)

Buckle (1998) defines resilience as "the capacity that people or groups may possess to withstand or recover from emergencies and which can stand as a counterbalance to vulnerability". According to UN/ISDR (2004), resilience is determined by the degree to which the social system is capable of organizing itself to increase its capacity for learning from past disasters for better future protection and to improve risk reduction measures.

For Turner et al (2003), resilience of the system is often evaluated in terms of the amount of change a given system can undergo and still remain within the set of natural or desirable states.

Based on the above definitions, flood resilience can be seen as the ability of a system or a community to mitigate or minimize threats of floods on itself. Resilience of a system to flood disasters can only be considered with past flood events as it focuses on elements encountered during and after the floods "figure 4"

Figure 3 Resilience framework

Source: Balica (2007, p 35)

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