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Avaliação da exposição das comunidades locais a incêndios florestais: o caso de Alvares, Góis
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Orientador(es)
Resumo(s)
Os incêndios florestais são considerados um grave risco ambiental e social em Portugal. O ano
de 2017 foi o mais trágico até à data, devido aos elevados danos materiais que ocorreram e às
maiores perdas humanas desde que há registo. Neste contexto, avaliar o nível de exposição a
incêndios das comunidades locais é crucial para melhorar a sua proteção e capacidade de
resposta.
A freguesia de Alvares foi gravemente afetada pelos incêndios de junho de 2017, tendo ardido
cerca de 70% da sua área total, com elevados danos materiais. Esta dissertação focou-se na
avaliação da exposição a incêndios nesta freguesia, a uma escala detalhada ao nível da
povoação, a partir da identificação dos elementos expostos (população, edifícios e estradas).
Para cada elemento foi calculada a densidade para a povoação e foram atribuídas ponderações
diferentes consoante a função e necessidade de proteção. O valor normalizado (escala 0-100)
dos elementos expostos foi, depois, multiplicado pela probabilidade de arder, avaliada em três
vertentes: i) estática, assumindo um valor constante de probabilidade de arder; ii) estrutural,
baseada no histórico de incêndios da freguesia; iii) dinâmica, baseada em vários cenários
simulados de gestão de combustível: Business As Usual (BAU), com condições pré-fogo 2017;
abandono, com diminuição da gestão florestal; e implementação de faixas de gestão em
diferentes proporções. Os resultados demonstram que as povoações localizadas a norte,
nordeste e este estão mais expostas a incêndios, tanto na exposição estrutural como na
dinâmica. Considerando os cenários, a percentagem de povoações com exposição muito
elevada diminui consideravelmente (40%) com a aplicação de faixas de gestão de combustível,
em relação aos cenários BAU e abandono.
Os fatores de vulnerabilidade disponíveis para as 36 povoações da freguesia, que caracterizam
a população, como o nível de escolaridade, e os edifícios, como o ano de construção, foram
também analisados. As povoações foram classificadas em 5 classes de vulnerabilidade a partir
da análise hierárquica de clusters com o método de Ward. Verificou-se que 25% das povoações
se encontram em classe de vulnerabilidade muito alta, e 19% encontram-se na classe elevada.
Estes resultados mostram que a avaliação da exposição a incêndios à escala da povoação pode
contribuir para melhorar a caracterização das comunidades locais e definir uma hierarquia de
intervenções, de forma a melhorar a capacidade de resposta da comunidade e ajustar os
mecanismos de prevenção e proteção que esta pode implementar.
Wildfires are considered a serious environmental and social risk in Portugal. The year 2017 was the most tragic to date due to the high material losses that have occurred and the greatest human losses since records exist. In this context, assessing the level of fire exposure of local communities is crucial to improving their protection and response capacity. The Civil Parish of Alvares was severely affected by the fires of June 2017, having burned about 70% of its total area, with high material damages. This dissertation focused on the evaluation of fire exposure in this parish, on a detailed scale at the village level, based on the identification of the exposed elements (population, buildings and roads). For each element the density was calculated for the settlement and different weights were assigned depending on the function and need for protection. The normalized value (scale 0-100) of the exposed elements was then multiplied by the probability of burning, evaluated in three dimensions: i) static, assuming a constant probability of burning; ii) structural, based on fire history; iii) dynamic, based on several simulated fire propagation scenarios: Business As Usual (BAU), with conditions similar to pre-fire 2017; abandonment, with reduced forest management; and implementation of fuel management network in different proportions. The results show that settlements located in the north, northeast and east are more exposed to fires, both in the structural and dynamic exposure. Considering the scenarios, the percentage of villages with very high exposure decreases considerably (40%) with the implementation of the fuel management network, in relation to the BAU and abandonment scenarios. The vulnerability factors available for the 36 villages in the parish, which characterize the population, such as education level, and buildings, like the year of construction, were also analyzed. The settlements were classified into 5 classes of vulnerability based on hierarchical clustering with the Ward method. It was found that 25% of the villages are in a very high vulnerability class, and 19% are in the high class. These results show that the assessment of village-level fire exposure can contribute to improving the characterization of local communities and to defining a hierarchy of interventions, in order to improve the community's response capacity and possibly to adjust the prevention and protection mechanisms it can implement.
Wildfires are considered a serious environmental and social risk in Portugal. The year 2017 was the most tragic to date due to the high material losses that have occurred and the greatest human losses since records exist. In this context, assessing the level of fire exposure of local communities is crucial to improving their protection and response capacity. The Civil Parish of Alvares was severely affected by the fires of June 2017, having burned about 70% of its total area, with high material damages. This dissertation focused on the evaluation of fire exposure in this parish, on a detailed scale at the village level, based on the identification of the exposed elements (population, buildings and roads). For each element the density was calculated for the settlement and different weights were assigned depending on the function and need for protection. The normalized value (scale 0-100) of the exposed elements was then multiplied by the probability of burning, evaluated in three dimensions: i) static, assuming a constant probability of burning; ii) structural, based on fire history; iii) dynamic, based on several simulated fire propagation scenarios: Business As Usual (BAU), with conditions similar to pre-fire 2017; abandonment, with reduced forest management; and implementation of fuel management network in different proportions. The results show that settlements located in the north, northeast and east are more exposed to fires, both in the structural and dynamic exposure. Considering the scenarios, the percentage of villages with very high exposure decreases considerably (40%) with the implementation of the fuel management network, in relation to the BAU and abandonment scenarios. The vulnerability factors available for the 36 villages in the parish, which characterize the population, such as education level, and buildings, like the year of construction, were also analyzed. The settlements were classified into 5 classes of vulnerability based on hierarchical clustering with the Ward method. It was found that 25% of the villages are in a very high vulnerability class, and 19% are in the high class. These results show that the assessment of village-level fire exposure can contribute to improving the characterization of local communities and to defining a hierarchy of interventions, in order to improve the community's response capacity and possibly to adjust the prevention and protection mechanisms it can implement.
Descrição
Palavras-chave
Exposição a incêndios Elementos expostos Fatores de vulnerabilidade Povoação Alvares Góis