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- Landslide susceptibility assessment using different rainfall event-based landslide inventories: advantages and limitationsPublication . Oliveira, Sérgio; Zêzere, José; Garcia, Ricardo; Pereira, Susana; Vaz, Teresa; Melo, RaquelThe present work aims to evaluate potential sources of uncertainty associated with rainfalltriggered event-based landslide inventories within the framework of landslide susceptibility assessment. Therefore, this study addresses the following questions: (i) How representative is an event-based landslide inventory map of the total landslide activity and distribution in a study area?; (ii) How reliable is an event-based landslide susceptibility map?; (iii) How appropriate is an event-based landslide inventory map for independently validating a landslide susceptibility map? To address these questions, two independent and contrasting rainfall event-based landslide inventories were used, together with a historical landslide inventory, to assess landslide susceptibility for diferent types of landslides in a study area located north of Lisbon, Portugal. The results revealed the following fndings: (i) contrasting rainfall critical conditions for failure can trigger similar landslide types, although they may vary in size and be spatially constrained by diferent predisposing conditions, particularly lithology and soil type; (ii) landslide susceptibility models using event-based landslide inventories are not reliable in the study area, regardless of the landslide inventory map used for training and validation; and (iii) complementary sources of uncertainty results from using incomplete historical landslide inventories to assess landslide susceptibility and non-totally independent landslide inventories for modeling validation. The present study enhances the understanding of regional landslide susceptibility patterns based on contrasting rainfall-trigger conditions, providing valuable information to minimize exposure; to design regional landslide early warning systems for specifc rainfall-trigger landslide events; and to improve the response and preparedness of civil protection services.
- Flood susceptibility assessment through statistical models and HEC-RAS analysis for sustainable management in Essaouira Province, MoroccoPublication . Khouz, Abdellah; Trindade, Jorge; Santos, Pedro Pinto; Oliveira, Sérgio; El Bchari, Fatima; Bougadir, Blaid; Garcia, Ricardo; Reis, Eusébio; Jadoud, Mourad; Saouabe, Tarik; Rachidi, SaidFloods are natural disasters that often impact communities living in low-lying areas in the northern and central parts of Morocco. In this study, our aim was to create a flood susceptibility map using three methods; the hierarchy process (AHP) frequency ratio model (FR) and the weights of evidence (WoE) model. We extensively examined the area identified by these approaches using a hydraulic analysis software called HEC-RAS (version 6.3.1). Our analysis focused on the Essaouira watersheds in Morocco, where we identified around 197 flood locations. Out of these, we randomly selected 70% for modeling purposes while the remaining 30% were used for validation. Ten factors that influence floods were considered, such as slope, elevation, proximity to rivers, drainage density, stream order, land use patterns, rainfall data, lithology (permeability level) index (TWI), and curvature. We obtained these factors from data sources. Finally, we generated a flood susceptibility map and evaluated its accuracy by calculating the area under the curve (AUC). The validation results confirmed that all three models were robust and effective with an AUC of 90. Moreover, the research uncovered a trend of vulnerability with the most susceptible area being in close proximity to the city of Essaouira along the Oued Ksob. A detailed analysis using HEC-RAS was conducted at this identified location, pinpointing the village of Diabat as highly exposed. These findings hold significance for flood management, empowering decision makers, scholars, and urban planners to make informed choices and implement strategies that can minimize the impact of floods in susceptible regions while minimizing potential damages.
- On the Multi-hazard Risk Assessment of Urban Areas: Identification and Analysis of Exposure and Physical Vulnerability IndicatorsPublication . Xofi, Maria; Domingues, José Carlos; Santos, Pedro Pinto; Pereira, Susana; Oliveira, Sérgio; Reis, Eusébio; Zêzere, José; Garcia, Ricardo; Lourenço, Paulo B.; Ferreira, Tiago MiguelThe development of integrated decision-support tools, able to assess multiple hazards at the regional and local scales, is a fundamental step to enhance the preparedness of urban areas to mitigate present and future risks arising from climate change. Understanding multi-hazard risk can help prioritize resilience-increasing actions and disaster prevention measures and form the basis for exploring institutional adjustments that improve stakeholders’ capacities to manage risk. Within this framework, the present research work aims to identify and analyze a set of exposure and buildings’ vulnerability indicators to be used as input to a multi-hazard risk assessment methodology. Exposure is to be measured using a dimensionless score resulting from the quantitative identification of the elements at risk. Regarding the physical vulnerability of buildings, it is to be evaluated on a hazard-by-hazard basis using a large-scale parametric-based vulnerability assessment approach. Finally, the obtained exposure and physical vulnerability indicators are to be put together in order to create different data layers, which are then used to identify hotspot risk areas. The Metropolitan Area of Lisbon, Portugal, is used as a pilot study area to discuss the applicability and potential of the proposed indicators.
- Spatial correlates of COVID-19 first wave across continental PortugalPublication . Barbosa, Bruno; Silva, Melissa; Capinha, César; Garcia, Ricardo; Rocha, JorgeThe first case of COVID-19 in continental Portugal was documented on the 2nd of March 2020 and about seven months later more than 75 thousand infections had been reported. Although several factors correlate significantly with the spatial incidence of COVID-19 worldwide, the drivers of spatial incidence of this virus remain poorly known and need further exploration. In this study, we analyse the spatiotemporal patterns of COVID-19 incidence in the at the municipality level and test for significant relationships between these patterns and environmental, socioeconomic, demographic and human mobility factors to identify the mains drivers of COVID-19 incidence across time and space. We used a generalized liner mixed model, which accounts for zero inflated cases and spatial autocorrelation to identify significant relationships between the spatiotemporal incidence and the considered set of driving factors. Some of these relationships were particularly consistent across time, including the ‘percentage of employment in services’; ‘average time of commuting using individual transportation’; ‘percentage of employment in the agricultural sector’; and ‘average family size’. Comparing the preventive measures in Portugal (e.g., restrictions on mobility and crowd around) with the model results clearly show that COVID-19 incidence fluctuates as those measures are imposed or relieved. This shows that our model can be a useful tool to help decision-makers in defining prevention and/or mitigation policies.
- A New Soil Cartography at 1:100,000 scale for mainland PortugalPublication . Batista, Gonçalo; Conceição, Mariana; Garcia, Ricardo A. C.; Oliveira, S.C.; Trindade, André; Viana, Cláudia; Rocha, JorgePortugal does not have detailed and complete soil maps at a scale that is useful for environmental management. Existing data is: Inconsistent and spread across different organizations; Different in terms of scale, methods used and classification systems; Often old maps converted from paper to digital, with missing or incorrect information. The General Soil Map of Portugal (1:1,100,000) is still the only national tool for soil information. Create a new soil map for mainland Portugal at a 1:100,000 scale.
- Quando o turismo e o fogo se encontram: análise espacial preliminar para a criação de destinos resilientesPublication . Garcia, Ricardo; Oliveira, Sandra
- Exposure and physical vulnerability indicators to assess seismic risk in urban areas: a step towards a multi-hazard risk analysisPublication . Xofi, Maria; Domingues, José Carlos; Santos, Pedro; Pereira, Susana; Oliveira, Sérgio; Reis, Eusébio; Zêzere, José; Garcia, Ricardo A. C.; Lourenço, Paulo B.; Ferreira, Tiago MiguelUnderstanding the impacts of multi-hazard risk in urban areas is a fundamental step towards the adoption of resilience-enhancement and disaster prevention strategies, underpinning institutional adjustments aimed at improving the capacity of the authorities and stakeholders to manage risk. Within this framework, the work presented in this paper seeks to identify and analyze a set of exposure and buildings’ physical vulnerability indicators to be used as input to a parametric-based seismic vulnerability assessment methodology for the unreinforced masonry (URM) building stock of Lisbon Metropolitan Area (LMA). For this approach, data from the 2011 Census survey are used to define the parameters describing the building’s physical vulnerability and characterise the level of exposure in the study area. These results are then combined with the hazard component into a GIS tool. Seismic vulnerability results are presented for the URM building stock in LMA, and a more detailed analysis is conducted for the building stock of Set ubal municipality. Finally, risk outputs are presented and briefly discussed. Ultimately, understanding the impact and extent of multi-hazards can help prioritize resilienceincreasing actions and disaster prevention measures to mitigate and manage natural hazards.
- Does the updating of landslides inventories have a relevant impact on the landslide susceptibility assessment?Publication . Melo, Raquel; Oliveira, Sérgio; Garcia, Ricardo; Zêzere, JoséLandslide inventories are essential for developing an accurate susceptibility assessment. However, the complete and systematic updating of these inventories is a time-consuming and challenging task. Therefore, we aimed to verify if the temporal updating of historical inventories improves the susceptibility models and if the size of the study area plays a relevant role in the decision to update or not landslide inventories. To answer these questions, the work was carried out in two study areas with different sizes but with a similar geomorphological context. The landslide susceptibility modelling, developed using the Information Value method, was performed for distinct types of landslides and using three landslide inventories: one with landslides that occurred before 2012; a second with landslides that occurred during the event of 2010; and a third with landslides that occurred up to 2019. The results indicate no improvement or only a residual enhancement in the susceptibility models’ predictive capacity, regardless of the type of landslide or the study area’s size.
- Defining evacuation travel times and safety areas in a debris flow hazard scenarioPublication . Melo, Raquel; Zêzere, José; Oliveira, Sérgio; Garcia, Ricardo A C; Oliveira, Sandra; Pereira, Susana; Piedade, Aldina; Santos, Pedro Pinto; van Asch, TheoDebris flows are one of the most hazardous types of landslides in mountain regions. In the upper part of the Zêzere valley (Serra da Estrela, Portugal) several debris flows events occurred in the last 200 years, some of them causing loss of lives and material damages. In this work, a methodology for pedestrian evacuation modelling, in a debris flow hazard scenario, was implemented. A dynamic run-out model, developed in previous studies, was used to evaluate the debris flows velocities, thickness of the deposits and extent of the mobilized material. The buildings potentially affected by the impact of debris flows were identified and the potentially exposed population was estimated by applying a dasymetric distribution. The results lead to the conclusion that, in the study area, the elderly are those who are most exposed to debris flows. Furthermore, the time lapse between the debris flows initiation and the arrival at the buildings at risk was estimated, allowing to account for the overall number of buildings where the evacuation time takes longer than the debris flows arrival. Additionally, the safe areas within the study area were identified, and several safe public buildings with the capacity to gather a large number of persons were selected. Considering that the study area is located in a mountain region, characterized by steep slopes, the evacuation modelling was performed based on an anisotropic approach, in order to consider the influence of slope direction on travel costs. At the end, three pedestrian evacuation travel time scenarios, based on different walking speeds to accommodate residents with different ages in safer places, were compared and the results mapped. The implemented methodology is not local dependent, which allows its reproduction elsewhere.
- Avaliações multirrisco como abordagem para a construção de cidades resilientes e sustentáveisPublication . Santos, Pedro; Pereira, Susana; Lourenço, Paulo; Zêzere, José Luís; Reis, Eusébio; Oliveira, Sérgio; Garcia, Ricardo; Ferreira, Tiago MiguelO conhecimento integrado dos fatores de risco é um elemento-chave para o desenho e implementação de políticas, estratégias e medidas de redução de impactos. O presente trabalho procura contribuir para a definição de metodologias de avaliação do efeito combinado da manifestação de múltiplos fenómenos perigosos, tomando como exemplos os processos de inundação costeira, cheias, sismos, movimentos de massa em vertentes e incêndios urbanos, e como área de trabalho os 18 municípios da Área Metropolitana de Lisboa. A avaliação de risco considera os fatores de suscetibilidade/perigosidade, exposição e vulnerabilidade. Os resultados obtidos até ao momento identificaram os pares de fenómenos perigosos cujo efeito combinado se traduz nos cenários de risco mais elevado, com destaque para a relação entre sismicidade e incêndios urbanos.
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