**5. Application of the risk models to the cities of Iquique, Puerto Varas, and Puerto Montt**

To apply the metrics of each model on the three cities analyzed, the information of all the criteria or variables considered for each cell4 or block of the city was analyzed. 1500 cells for

<sup>4</sup> A cell is the territorial unit selected in the study where the four models are applied and for which DRI is calculated.

the city of Puerto Montt, and 3000 cells for all three cities were assessed. Each cell was assessed in absolute measurement at each terminal criterion or model indicator, using a specific cardinal scale (natural) to the terminal criterion or measurement model indicator. This was done systematically for each cell of each model.

Finally, the four models (H, E, PSV, and SR) were integrated using EQ1 and as a result, we obtained the comprehensive DRI of each cell.

It is important to remember that:

Socio‐demographic vulnerability

Socioeconomic vulnerability

dwelling

Number of families inside a

**Puerto Montt**

4

Degree of dependency Measures the degree of dependency in the block

182 Applications and Theory of Analytic Hierarchy Process - Decision Making for Strategic Decisions

intellectual disability

Overcrowding Vulnerability due to overcrowded house

**Table 5.** Criteria definition table for the model of social vulnerability.

strating its importance as factors that explain the PSV.

criteria or variables considered for each cell4

Age Age of people in the block

Degree of vulnerability due to socio‐demographic characteristic of people in the block

Degree of vulnerability due to socioeconomic characteristics of people in the block, it depends on number of: unemployed people, unemployed youth women acting as head of

Disability Different types of disability reported: hearing, and visual impairments, physical and

Educational level Level of formal education (differential, without formal education or elementary only)

Home ownership Vulnerability due to type of ownership: free housing, assigned housing, or leased

Vulnerability due to more than one family present inside one dwelling

Health Vulnerability due to level of health inside the residence, produced primarily by two issues: housing without current water and housing without bathroom.

The two most important criteria are residential vulnerability (42.3%) and socio‐demographic vulnerability (35.9%). On the other hand, the most relevant criteria or measuring indicators within socioeconomic vulnerability is unemployment (12.4%). Within residential vulnerabil‐ ity, it is the substandard housing (12%), the number of families per dwelling (10.3%), and overcrowding (8.2%), whereas in socio‐demographic vulnerability, the most relevant criteria include physical‐motor disability (9.5%) and intellectual disability (6.2%). These six indicators account for almost 60% of the total weight of the 20 indicators that make this model, demon‐

**5. Application of the risk models to the cities of Iquique, Puerto Varas, and**

To apply the metrics of each model on the three cities analyzed, the information of all the

A cell is the territorial unit selected in the study where the four models are applied and for which DRI is calculated.

or block of the city was analyzed. 1500 cells for

household, and retired (jubilee) people.

Residential vulnerability Degree of vulnerability due to the residential precariousness

Precarious property Vulnerability due to precarious level of property (shacks)


#### **5.1. DRI, city of Iquique**

The modeling considered the different variables or risk factors for the city of Iquique and applied the DRI index to the block level. The result of this graphical process (**Figure 2**) shows that medium‐low risk conditions is dominant in the city, while low‐risk areas, mostly near the civic center, are scarce. These results are consistent with the reality of a city that is, like many Chilean cities, exposed to different hazards like earthquakes, tsunamis, and landslides. Moreover, a distinct level of social vulnerability expressed through factors such as the precariousness in housing, overcrowding, poor education, disability, and unemployment, among others, increases the susceptibility to suffering damages and difficulties in recovering from a disaster event.

The Iquique waterfront shows a medium‐high level of risk, mainly due to the significant and growing population exposure to tsunamis in this area. Although a medium‐high level implies greater danger, the risk becomes somewhat lower when integrated with the hazard modeling and exposure to the PSV. This is justified because the Iquique waterfront is characterized by low PSV, as it is generally inhabited by people of medium‐high and high socioeconomic strata. Their economic capabilities allow them to prepare for emergencies and quickly recover post disasters events as seen after the earthquake in 2014. In addition, this population, with a strong support network, demonstrates independence in decision‐making, showing management capacity, and resilience which modulates or dampens the hazard and exposure present in the cells of this zone. These results indicate that the process of integration of the four models is not only interesting but also necessary for proper assessment and later qualification of the degree of disaster risk in a specific area.

**Figure 2.** Disaster Risk Index, Iquique City.

The northern coastal area, an industrial region, with a high probability of a tsunami, shows a low‐medium risk as it has virtually no residents (E = 0) and thus does not present values of social vulnerability (PSV = 0). However, this result could be questioned as a sizeable number of people work in this area during the day. The model, in the first instance, does not consider this floating working population due to lack of information about them. This could be remedied by performing a sensitivity analysis by incorporating this population and its characteristics, building a scenario where DRI values display the day index situation in the zone's cell.

There are zones with a medium‐high risk immediately south of the industrial area with values in the upper limit, that is, a slight deterioration in their condition can move the zones to the category of high or unacceptable risk. This area brings together several negative conditions that maximize each other: the exposure of large populations and critical facilities (health care) to tsunamis, along with vulnerable populations such as a large number of dependent people, people with cognitive disabilities, people with low education level, unemployed people, and a significant number of female as heads of households. This outcome is reflected in the comprehensive risk index at the cell level (as shown in the value of the integrated DRI index). The classification of cells by risk levels helps the prioritization of risk interventions and resources allocation.

The application of the EQ1 for Iquique is given in **Table 6**.


**Table 6.** Applying EQ1 equation to calculate[21] the DRI in block[22] 37 Iquique city.

DRI(37) = [2/3\*(0.5\*0.5243 + 0.5\*0.8650 + 0.5243\*0.8650) + 1/3\*(.4209)] \* [1 - 0.2676] = 0.6636 (Risk medium – high to high).

Notice: Block 37 has a DRI = 0.6636 ≈ 0.6832, is only 2.9% below the limit considered unac‐ ceptable (0.6832). Also, the exposure value for this block (0.8650) is far over the specific threshold for exposure (0.6003), this is about 44.1% over the upper limit.

The upper limit (threshold) of DRI calculated for Iquique is 0.6832. Anything above should be considered unacceptable level of risk disaster.

This analysis methodology (working with cardinal numbers) also allows analysis of an average cell or average block, for the city of Iquique. The average cell is representative of the average behavior of the city, as if this were all included in a single cell.

Below is a table with the behavior of the average cell in each model and its final value calculated using Eq. (1) (**Table 7**).


**Table 7.** Average block behavior Iquique.

**Figure 2.** Disaster Risk Index, Iquique City.

zone's cell.

The northern coastal area, an industrial region, with a high probability of a tsunami, shows a low‐medium risk as it has virtually no residents (E = 0) and thus does not present values of social vulnerability (PSV = 0). However, this result could be questioned as a sizeable number of people work in this area during the day. The model, in the first instance, does not consider this floating working population due to lack of information about them. This could be remedied by performing a sensitivity analysis by incorporating this population and its characteristics, building a scenario where DRI values display the day index situation in the

184 Applications and Theory of Analytic Hierarchy Process - Decision Making for Strategic Decisions

There are zones with a medium‐high risk immediately south of the industrial area with values in the upper limit, that is, a slight deterioration in their condition can move the zones to the category of high or unacceptable risk. This area brings together several negative conditions that maximize each other: the exposure of large populations and critical facilities (health care) to tsunamis, along with vulnerable populations such as a large number of dependent people, people with cognitive disabilities, people with low education level, unemployed people, and a significant number of female as heads of households. This outcome is reflected in the comprehensive risk index at the cell level (as shown in the value of the integrated DRI index).

Note: It is important to remember that the values obtained for Iquique DRI have a different rule of measurement than the cities of Puerto Montt and Puerto Varas, (since it has a different Hazard model). Therefore, they are not comparable values. This "non‐comparability" also applies for the outcome of the average cell.

#### **5.2. DRI, city of Puerto Varas**

The most populated area of Puerto Varas generally presents a low average risk; however, its expansion areas, such as the northwest area of the city, have a (medium‐high) risk. The lower‐ risk area is located in the city center, away from flood or landslide prone areas, and only presents the same risk level as the rest of the city for the hazards of volcanic ash fall and earthquakes. In contrast, some areas near the waterfront in the southern part of the city have very high exposure levels to landslides. The population here, with no formal or only basic education, is highly dependent because of the significant presence of seniors and to a lesser extent, people with hearing impairment.

These factors explain the level of risk in this zone which could be mitigated by infrastructure and territorial planning.

The south of Puerto Varas (an area furthest from the lake at a higher elevation) is associated with high overall risk mainly because of higher social vulnerability along with the high impact, low frequency hazards such as earthquakes and ash fall. The frequently recurring hazards like floods and landslides do not pose significant impacts.

#### **5.3. DRI, Puerto Montt City**

The city of Puerto Montt presents a medium‐high risk level virtually in its entire urban area (**Figure 4**). Overall, the risk in the city is associated with the escarpments of marine terraces and presence of areas prone to landslides. The landslides have led to the loss of homes, and a high risk for families who inhabit those neighborhoods and have already experienced damage

**Figure 3.** Disaster Risk Index (DRI), Puerto Varas.

and losses in dwellings and livelihoods. The local government is working on regulations to limit the use of areas at risk for residential purposes, and to relocate the existing population, designating this land as environmental protection zones. Another significant hazard is linked to the stream banks that cross through the city and cause flooding during heavy rainfall episodes. These areas are usually occupied by informal settlements characterized by precari‐ ous homes and utilities, resulting in medium‐high risk levels, very close to unacceptable risks.

The areas of future expansion present a medium‐low level of risk, as despite the low exposure of population and infrastructure, these are landslide prone and recurrent floodplain areas which require important investments in mitigation works to assure a sustainable future.

The recent expansion areas situated westward, toward the airport, exhibit the same precarious features mentioned above, and have been urbanized with densely populated plots and very few green areas, normally associated with populations with a high level of social vulnerability. However, there is a potential for risk reduction through improved infrastructure.

**Figure 4.** Disaster Risk Index (DRI), Puerto Montt City.

risk area is located in the city center, away from flood or landslide prone areas, and only presents the same risk level as the rest of the city for the hazards of volcanic ash fall and earthquakes. In contrast, some areas near the waterfront in the southern part of the city have very high exposure levels to landslides. The population here, with no formal or only basic education, is highly dependent because of the significant presence of seniors and to a lesser

186 Applications and Theory of Analytic Hierarchy Process - Decision Making for Strategic Decisions

These factors explain the level of risk in this zone which could be mitigated by infrastructure

The south of Puerto Varas (an area furthest from the lake at a higher elevation) is associated with high overall risk mainly because of higher social vulnerability along with the high impact, low frequency hazards such as earthquakes and ash fall. The frequently recurring hazards like

The city of Puerto Montt presents a medium‐high risk level virtually in its entire urban area (**Figure 4**). Overall, the risk in the city is associated with the escarpments of marine terraces and presence of areas prone to landslides. The landslides have led to the loss of homes, and a high risk for families who inhabit those neighborhoods and have already experienced damage

extent, people with hearing impairment.

floods and landslides do not pose significant impacts.

and territorial planning.

**5.3. DRI, Puerto Montt City**

**Figure 3.** Disaster Risk Index (DRI), Puerto Varas.

The city in general is exposed to seismic and volcanic hazards (volcanic ashes) and a low risk of tsunami. However, other recurring hazards of hydro‐meteorological type affect the inhabitants throughout the year, causing small but cumulative impact resulting in deteriora‐ tion of their health and quality of life.

#### **5.4. Comparative analysis of the two cities: Puerto Varas and Puerto Montt**

It is at the local level that risk is built and consequences of adverse events experienced. Hence our analysis recognizes the significance of conducting risk assessment at the local level, taking into account its main components (hazard, vulnerability, and exposure), to generate a signif‐ icant differentiation between and within cities.

The assessment at the block level helps to improve decision‐making regarding resource allocation for disaster risk reduction, as it identifies the most critical blocks for prioritization of intervention. At the same time, it is also possible to work on prospective risk management, addressing and seeking to avoid the construction of new or increased disaster risks, and defining the best options for the city expansion.

**Table 8** shows a comparative analysis between the two cities evaluated with the same model (Puerto Varas and Puerto Montt). An "average" block or representative of each model H, E, PSV, and SR was selected as the arithmetic average of the values of the cells of each city to calculate the representative DRI.


**Table 8.** Comparative analysis of the average behavior: Puerto Montt v/s Puerto Varas.

In analyzing the above table, it can be seen that the perceived DRI Puerto Varas is 9.0% higher than that of Puerto Montt. Even though it seems counterintuitive at first (it is the general perception that Puerto Varas has a lower risk than Puerto Montt), the result is considered reasonable. The hazard in Puerto Montt (0.4362) is rated 55% higher than in Puerto Varas (0.282) but at the same time, the SR in Puerto Montt (0.5120), 59% higher than Puerto Varas (0.3230), compensates for the hazard.

Note that both E as well as PSV are almost the same in both cities (9.5% and 0.2% difference), making the overall difference indecisive.

In an analysis by rating of cell, it can be said that there is only 9% difference in the overall perceived disaster risk between the two cities. Puerto Montt has more cells qualified in medium‐high risk than in Puerto Varas, but this is offset by the fact that Puerto Montt has several cells qualified as low risk cells, while Puerto Varas has none.

The perception that Puerto Varas' hazards have less potential impact compared with Puerto Montt holds true. However, a comprehensive risk assessment considering all the variables reveals that the level of overall risk of Puerto Varas is higher, mainly due to social and subjective factors.
