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- A landslide risk index for municipal land use planning in PortugalPublication . Pereira, Susana; dos Santos, Pedro; Zêzere, José; Tavares, A. O.; Garcia, R.A.C.; Oliveira, S.In Portugal landslides caused 237 fatalities and >1600 displaced people in the period 1865-2015. Spatial distribution and temporal patterns of slope instability can be related with a complex set of natural and human factors responsible for generating damages. It is essential to develop new methodologies to synthetize risk dimensions to contribute to the landslide risk management at the municipal level. This work proposed a municipal landslide risk index (LRI) considering three risk dimensions: hazard, exposure and physical vulnerability of buildings. The hazard dimension includes the landslide susceptibility performed at the national scale, the probability of weather types associated with landslides and an extreme precipitation susceptibility index. The exposure dimension considered the population density and the number of buildings, whereas the average physical vulnerability of the buildings was computed using four statistical variables from the official census: (i) construction technique and construction materials; (ii) reinforced structure; (iii) number of floors; and (iv) conservation status. Each variable includes different classes that were empirically weighted. After evaluating the three risk dimensions and the LRI, a cluster analysis was performed in order to identify the most important landslide risk drivers in each municipality. Exposure is the main driving force of LRI in the metropolitan areas of Lisbon and Porto, while the hazard is more relevant in the NW municipalities and the physical vulnerability is the major driving force in the south of the country. This methodological approach contributes to a comprehensive and synthetized knowledge about the landslide risk driving forces within the 278 Portuguese municipalities. In addition, it contributes to the diversification and context-oriented strategies of landslide risk management that still lacks in most of the national-level risk governance processes. Finally, this methodology can be generalized to other geographical contexts, improving the risk management, land use planning and the disaster risk reduction.
- Assessing sea level rise exposure and social vulnerability scenarios for sustainable land use planningPublication . Trindade, Jorge; Zêzere, José; Reis, Eusébio; Rocha, Jorge; Santos, Pedro Pinto; Garcia, Ricardo; Oliveira, Sérgio; Pereira, SusanaThe climate change scenarios, with sea level rise and increased frequency of extreme hydro- meteorological events, associated with the growing pressure on the coastal zone, highlight the need to improve the ability to predict risk factors under future scenarios and assess impacts in these territories at global and national level. Starting from the current scenario, the High Waters research project intends to contribute to the definition of a roadmap of adaptation and mitigation measures for coastal risks in the medium and long term. Taking 2040, 2070 and 2100 as time stamps it aims at analysing the future hazard, exposure and vulnerability over Portuguese coastal areas. The project aims also to elaborate municipal risk profiles to support proposals of management strategies for coastal zones, using various methods, including fieldwork, statistical and remote sensing data processing and application of machine learning techniques.
- A comprehensive approach to understanding flood risk drivers at the municipal levelPublication . Santos, Pedro Pinto; Pereira, Susana; Zêzere, José; Tavares, Alexandre Oliveira; Reis, Eusébio; Garcia, Ricardo A C; Oliveira, SérgioDuring the period 1998–2017, floods were responsible for 11% of the loss of life and 23% of the economic loss caused by climate-related and geophysical-related disasters worldwide. An integrated and effective definition of flood risk management strategies therefore still requires synthesized and comprehensive knowledge about the driving forces of flood risk. In this study, 278 Portuguese municipalities are analyzed and classified according to flood hazard, exposure, and vulnerability. After evaluating the three components that describe risk, an index of the flood risk is calculated and a cluster analysis is further performed to understand the role of the risk drivers (hazard, exposure, and vulnerability) in each municipality. The proposed approach therefore provides flood risk indexes on a municipal basis, which are built upon different sources of both cell-by-cell data and an aggregation of municipal-level data that has been statistically validated. Municipalities both in the NW part of the country and along the valleys of major rivers demonstrate a significant superimposition of high levels of exposure and hazard, while vulnerability presents a disperse pattern throughout the country. The results obtained using this approach should contribute to the diversification of flood risk management strategies. This is still lacking in the majority of the national-level flood risk governance processes, namely those strategies that focus on the contingency of daily activities and those aiming at a long-term reduction of the exposure, vulnerability, and hazard components that shape flood disasters.
- Landslide quantitative risk analysis of buildings at the municipal scale based on a rainfall triggering scenarioPublication . da Silva Pereira, Susana; Garcia, Ricardo A C; Zêzere, José; Oliveira, Sérgio; Silva, MárcioA landslide quantitative risk analysis is applied the municipality of Santa Marta de Penagui~ao (N of Portugal) to evaluate the risk to which the buildings are exposed, using a vector data model in GIS. Two landslide subgroups were considered: landslide subgroup 1 (event inventory of landslides occurred on January 200)1; and landslide subgroup 2 (inventoried landslides occurred after the 2001 event until 2010). Seven landslide predisposing factors were weighted and integrated using the Information Value Method. The landslide susceptibility model was independently validated and the model performance was expressed by ROC curves. The probability of landslide size was estimated using a probability density function and the landslide hazard scenario was defined using the same landslide rainfall-triggering event. A vulnerability curve was constructed for each type of building considering its structural properties and the proxy of landslide magnitude. The economic value assigned for each building represents an approximated cadastral value. The landslide risk was computed for each building in vector format based on a rainfall triggering scenario and two landslide magnitudes. The probability of occurrence of small landslides is two orders of magnitude higher than the probability of occurrence for large landslides, which explains the higher risk generated by small landslides, despite of registering.
- Padrão de deformação de movimentos de vertente em áreas periurbanasPublication . Oliveira, Sérgio; Zêzere, José; Garcia, Ricardo A C; Pereira, SusanaThe occurrence of landslides triggered by intense or long-lasting rainfall events in the region north of Lisbon has produced considerable material losses related with the partial or full destruction of infrastructures, in particularly roads and buildings. This problem becomes more relevant in the peri-urban areas as it is the case of the Grande da Pipa River basin that registered a potential growth resulting from the proximity of the Lisbon city. As an exploratory approach, this study allowed to evaluate the damage pattern in buildings and roads as consequence of landslides occurrence. To achieve that goal the following topics were considered: the resistance of the exposed element, the intensity of the landslide, and the spatial relationship between the exposed element and the different sectors of the landslide that affect it. For buildings the lack of data did not allow to define any deformation pattern. In the case of roads three different deformation patterns can be inferred by the way roads relate with the landslide sector which originates the damage. When the landslide rupture surface is located above the road the damage level registered was negligible. When the road is located within the landslide area the degree of loss registered increased (slight loss or significant). When the road is affected by a landslide scarp or landslide flank, variable degrees of loss were observed which appear to be dependent on the vertical steps existing in the landslide scarp or flanks.