HOW CAN WE REDUCE VULNERABILITY?

"Disaster risk reduction is about choices"

UNISDR (The United Nations Office for Disaster Risk Reduction)

Disaster risk reduction is the concept and practice of reducing disaster risks through systematic efforts to analyse and reduce the causal factors of disasters (UNISDR, http://www.unisdr.org/who-we-are/what-is-drr). A disaster's severity depends on how much impact a hazard has on society and the environment. In its turn, impact depends on the inner structure of society and its interdependencies, including infrastructure and assets location, access to health and education. Each decision and action that governements take are contributing to make us more vulnerable to disasters or more resilient to them.

In the last decades, vulnerability has been recognized as a crucial factor that contributes to risk. In addition, many types of vulnerability have been introduced (Cutter et al., 2006; Galderisi et al., 2008; Tapsell et al., 2010). The main distinction, and common between all recent classifications, is between physical vulnerability (elements are vulnerabile due to their physical characteristics) and systemic vulnerability (elements are strategic for the whole system due to their interaction with other elements).

In particular, volcanic risk assessment, traditionally focused on physical vulnerability, includes nowadays different indicators of systemic and socio-economic vulnerability, extremely important to grasp the complex interactions that happen within human societies (Wilson et al., 2009; Wilson et al., 2011; Biass et al., 2012).

My research contributed to the development of new and comprehensive vulnerability assessment methodologies, valid for volcanic risk assessment but also, to some extent, for other natural hazards. The principles and methodologies developed during the reserach have been applied to three active volcanic areas: Tenerife Island (Spain), Nicaragua and Iceland. Results have been published on international journals (see "publications" section for details).

TENERIFE ISLAND

In this work, we developed a GIS-based methodology to estimate damages produced by volcanic eruptions. The methodology is constituted by four parts: definition and simulation of eruptive scenarios, exposure analysis, vulnerability assessment and estimation of expected damages.

The tool is applied to the Icod Valley (North of Tenerife Island) which is likely to be affected by volcanic phenomena in case of eruption from both the Teide–Pico Viejo volcanic complex and North-West basaltic rift. Multi-hazard eruptive scenarios are defined for the Teide–Pico Viejo active volcanic complex based on available volcanological studies (Araña et al., 2000; Marti et al., 2008; Marti et al, 2012), and simulated through the VORIS tool (Felpeto et al., 2007).

The exposure analysis identifies the elements exposed to the hazard at stake and focuses on the relevant assets for the study area. The vulnerability analysis is based on previous studies on the built environment (Spence et al., 2005; Marti et al., 2008) and complemented with the analysis of transportation and urban infrastructures.

Damage assessment is performed associating a qualitative damage rating to each combination of hazard and vulnerability. This operation consists in a GIS-based overlap, performed for each hazardous phenomenon considered and for each element. The methodology is then automated into a GIS-based tool using an ArcGIS® program. Given the eruptive scenarios and the characteristics of the exposed elements, the tool produces expected damage maps.

Results are thematic maps of vulnerability and damage that can be displayed at different levels of detail, depending on the user preferences. The aim of the tool is to facilitate territorial planning and risk management in active volcanic areas. These maps allow identifying "societal hotspots" that have high systemic vulnerability, and support the definition of intervention priorities both during the emergency and for preparedness. Outcomes of the vulnerability and impact assessment are available in the published article (Scaini et al., 2014; see "publications" section).

NICARAGUA

During this research, a first-level exposure and vulnerability assessment was performed at local level for Ometepe Island and at National level for the Nicaraguan country. Results allow assessing expected impacts of the high-magnitude eruptive scenario previously defined for Concepción volcano (Scaini et al., 2012). This analysis was presented to the GISRUK conference (Liverpool) and the paper was published in the GISRUK conference proceedings (Scaini and Folch, 2012). In addition, results were presented at the Cities on Volcanoes Conference (Colima, Mexico, November 2013). The GIS dataset to perform this analysis was provided by INETER (Instituto Nicaraguense de Estudios Territoriales, the National Territorial Protection Institute).

The first step of this analysis was the identification of exposed elements, i.e. the exposure analysis. Critical issues at local scale are the high vulnerability of buildings, the lack of redundancy of the road network (constituted by one main circumvention road and few unpaved secondary roads). The main exposed elements (strategic buildings such as schools and health care centers), activities (agriculture) and infrastructures (roads) of Ometepe Island are shown in the figure below. Buildings in Ometepe have a overall high vulnerability, due to poor construction typologies and low maintenance of buildings. From the socio-economic point of view, agriculture has a strategic role. The main product is plantain, a variety of banana, and the production can be strongly impacted by ash fallout. Finally, tourism activities are increasing in the area, also thanks to the new airport of La Paloma, built in 2013 in the Island.

One of the main activities from the National point of view are agriculture (19.6 % of GDP and employs a 30% of population), that can be strongly affected by tephra fallout in the central part of the country. Major Nicaraguan agricultural exports to US are coffee, spices, beef, sugar, peanuts, hardwood, shrimp and lobster, while Nicaragua imports from U.S. mainly cereals and oil. The most important industrial centers are Managua, León, Chinandega and Granada, and the main products are textile and leather products, processed food and beverage and chemical products. Most of the goods produced in the central part of the country are likely to be exported by road and air traffic. Thus, transportation network has a high relevance for the national economy.

Ash fallout from Concepción volcano can affect road traffic and disrupt road commerce. In particular, the main Nicaraguan trade vector is the Panamerican corridor. It is worth noticing that the presence of a railway would decrease systemic vulnerability by increasing redundancy of transportation system. Finally, tephra produced by a high-magnitude scenario at Concepci ́on volcano can affect substantially operations within the Nicaraguan airspace and main airports. The figure below shows the panamerican corridor and the location of the main airports. Note that primary roads (purple) are in some cases interrupted, suggesting a low quality road network in some areas.

The comparison of this map with the tephra fallout and dispersal hazard assessment performed for Concepción volcano (Scaini et al., 2012) allow identifying the main expected impacts on the National socio-economic system.

In case of occurrence of a high-magnitude eruption at Concepción volcano, new airports of La Paloma (Ometepe) and Greylands (San Juan del Norte) opened few years ago would also suffer strong disruptions (La Paloma airport may suffer disruptions even for low-magnitude events). Information an air traffic not available at the moment. A high-magnitude eruptive scenario at Concepción volcano is likely to cause the Managua Airport closure (probability around 50% for HSM scenario) and cause cancellation of approximately 20 flights per day. In addition, 2700 passengers and 135 freight tons per day would be stranded (averaged values obtained by the analysis of Managua airport activity).

Local direct impacts at Ometepe Island due to ash fallout would result in more than 30 strategical buildings damaged by 100 kg/m2 load at ground. Primary roads would be disrupted by 1 kg/m2 load (primary road network ~47 km, has 70% probability of being totally damaged). Crops would be damaged by 1 kg/m2 tephra load (total crops are ~145 km2 and have a 50% probability of being totally disrupted). In addition, abundant tephra deposition at volcano flanks could trigger lahars during the rainy season.

ICELAND

Given the strong impacts of tephra fallout at local scale, the vulnerability and impact assessment analysis has been also performed for tephra fallout in case of occurrence of eruptive scenarios at the Icelandic volcanoes considered in the previous hazard assessment (Biass et al., 2014).

Hazardous scenarios considered for the Icelandic case-study, and in particular at Hekla, Askja and Katla, are likely to produce impacts on strategic infrastructures (i.e. electricity network and power plants). The exposed elements identified in the exposure analysis are: population, strategic buildings (hospitals, local health care centers and schools, which can be used as ash shelters), electricity network, hydroelectric and geothermal power plants, economic activities (production sites, main cities, agricultural areas) and presence of water supplies.

The vulnerability analysis, developed from a systemic point of view, was applied only to the relevant indicators for the hazard at stake, and limited by the data availability. In particular, the vulnerability was analyzed for electric power plants and electricity network, road network and agricultural activities. In addition, we took into account the accessibility of main mobility nodes (airports and ports).

Eruptions at Hekla may be particularly problematic due to its proximity to most Icelandic power plants. Scenarios at Askja and Katla volcanoes can produce substantial impacts on agricultural activities (mainly pastures). Finally, road network can be disrupted by tephra fallout, in particular in the South-East of the country. Tephra fallout is not likely to impact main Icelandic airports (Keflav ́ık Reykjav ́ık and Akureiri) due to the dominating Eastwards winds.

Results of the national-scale analysis can support territorial planning and allow identifying critical areas and prioritize actions. Results are described in detail and discussed in Scaini et al., 2014 (see 'publications' section).