**1. Introduction**

So far, there is no technique to accurately predict the occurrence of a volcanic eruption. Some of the phenomena presented by volcanoes such as seismic activity (tremors, etc.), soil deformation, gas emissions, or fumarolic activity and the chemical composition of water and its vapors help scientists to know when a volcano begins to activate. If changes in these phenomena can be detected, it is possible to establish some degree of probability of a volcanic eruption, although it is impossible to predict the day, time, and size of an eruption [1].

To detect these changes, volcanic observatories have been installed in various volcanoes around the world for several years, equipped with a series of equipment that has been collecting valuable information, allowing in some cases to predict at least the time when the activity would begin in the surface and the place where the materials would be emitted [2–4]. Anyway, volcanoes have individual behaviors,

so it is necessary to make a permanent and specific follow-up to each one, because although it is true there are some features common to all, there are others that individualize them [5–7].

It is also important to investigate the history of each volcano through the identification, petrographic analysis, and dating of its multiple pyroclastic deposits, to determine the characteristics that typify them [8, 9]. With this information and other knowledge, it is possible to elaborate, for example, maps of volcanic threats, which although they do not allow to determine when the next eruption will be, if they allow to determine an approximate order of the magnitude of the event and of the areas of affectation [10].

In fact, in the world, there are very few experiences of studies oriented to the integral evaluation of risk in the face of natural hazards. So much so that in the case of volcanic risk, most of the scientific-technical and economic efforts have been oriented mainly toward the evaluation of threats, with few methodological considerations for the evaluation of vulnerability and much less of the risk [11]. In other cases, the threat and vulnerability are evaluated independently, which logically presents many difficulties for the integral risk assessment. It is also easy to verify that many of the studies called "vulnerability assessments" are only physical and functional characterizations and diagnoses of vital infrastructure and population [12–14]. These characterizations can hardly be interpreted in terms of georeferenced indexes and/or maps of vulnerability that represent the spatial and temporal exposure of the elements exposed to each threat, much less that they represent the intrinsic and extrinsic response capacities of these elements compared to the threats.

What is required, then, is to define to whom and to what this event could affect, its degree of vulnerability to the threat, and the level of risk to which it is subjected, as basic inputs for decision-making and comprehensive risk management.

In this chapter of book, in light of the process of "Systemic Parametrization of the Environmental Dimension" [15], a summary of the conceptual and methodological approach developed by the undersigned is presented through the PIGA Group for Research in Politics, Information, and Management Environmental of the Universidad Nacional de Colombia, to carry out the studies and analysis of vulnerability and risk in a sector of the area of influence of the Cerro Machín volcano [16], taking as a starting point the study of the volcanic threat previously advanced by the former Colombian Institute of Geology and Mining [17].

Finally, some general conclusions and recommendations are presented with the hope that this new approach constitutes another grain of sand in the difficult task of protecting human beings and their environment from natural threats, particularly from volcanic threats, all through of an integral management of the risk that evaluates and anticipates the threats in a timely manner, that adequately plans and budgets the policies, strategies, instruments, and protocols to be followed in front of them, and that responds with effectiveness against the handling of emergencies and contingencies. In any case, it is expected to understand that "there are no natural disasters but political and management disasters."

### **2. New conceptual approach**

Traditionally, the definition of risk (R) refers to the probability that something harmful will happen on a given element [18]. The simplest conceptual expression to express the risk has been R = A. V, where A is the threat, understood as a latent condition derived from the probability of occurrence of a physical phenomenon of natural, socio-natural, or anthropic unintentional origin that it can cause damage to the element or group of exposed elements, and V is the vulnerability, understood as

**69**

**Table 1.**

*Valuation of the intrinsic threat index***.**

*Toward a New Conceptual and Methodological Approach for the Integral Evaluation…*

risk, based on the integral assessment of threats and vulnerabilities.

the susceptibility or characteristic of the element or group of elements to be totally

Consistent with [18, 19], the threat represents the potential for damage of a natural phenomenon and is calculated by quantifying the energy that is applied to a

Consequently, taking as reference, the equation model that calculates the intrinsic importance in environmental impacts [20], the intrinsic threat index (Å) is calculated for each threat j of each analysis scenario based on its main intrinsic

where Å is the intrinsic threat index, P is the probability of occurrence, I is the intensity of the threat, D is the duration of the threat, E is the extension of the

For the qualitative assessment of each of the characteristics that determine the intrinsic threat index, the environmental impact assessment model is taken as a reference [20], and **Table 1** is generated where the different assessment categories

*<sup>j</sup>* = P ( 0,6.*Ij* + 0, 2.*Dj* + 0, 1.*Ej* + 0, 1.*Aj* ) (1)

For the purposes of this study, it is assumed that the energy of a threat (as well as that of an environmental impact) can be represented qualitatively according to its intrinsic characteristics of probability of occurrence, intensity, duration, extension, accumulation, synergy, etc. [20], and, therefore, the quantification of this energy is done by means of an index that represents dimensionally and under the same scale the intrinsic characteristics of the different volcanic threats

In the development of this chapter of book, a new conceptual and methodological approach is proposed for the integral evaluation of volcanic risk, which includes the generation and adjustment of a new equation for the determination of volcanic

*DOI: http://dx.doi.org/10.5772/intechopen.84415*

particular site of interest or unit of analysis.

characteristics as shows in Eq. (1):

threat, and A is the accumulation of the threat.

Å

**2.1 Threat analysis**

considered.

are proposed.

or partially damaged by the impact of the threat [19].

#### *Toward a New Conceptual and Methodological Approach for the Integral Evaluation… DOI: http://dx.doi.org/10.5772/intechopen.84415*

the susceptibility or characteristic of the element or group of elements to be totally or partially damaged by the impact of the threat [19].

In the development of this chapter of book, a new conceptual and methodological approach is proposed for the integral evaluation of volcanic risk, which includes the generation and adjustment of a new equation for the determination of volcanic risk, based on the integral assessment of threats and vulnerabilities.
