How complete should be the landslide inventory to generate a reliable landslide susceptibility model?

Historical landslide inventory maps are frequently incomplete and this is usually pointed out as a source of uncertainty affecting the predictive ability of data-driven landslide susceptibility models. Nevertheless, the concept of having a complete landslide inventory seems far from reaching a consensual definition, both from the theoretical and practical point of view. Landslide mapping over time depends on a wide range of factors, some of them as simple as the ambitious capability to regionally map all the landslide features/signatures, detectable by fieldwork or image interpretation, which are often lost in a short period due to erosion or man intervention, which erase the morphological signs of instability. Within this framework, the main goal of the present work is to assess to what extent a presumed complete shallow slides inventory map is necessary to consistently assess the susceptibility to shallow slides in a certain area. The working hypothesis is tested in the Grande da Pipa river (GPR) basin, which extends for 110 square kilometers in the north of Lisbon region, Portugal. To assess susceptibility to shallow slides occurrence, we apply a bivariate statistical method (the Information Value), using an inventory containing more than 500 shallow slides ranging in size from 10 to 8000 square meters; and a dataset of eight terrain predisposing factors (lithology, slope, aspect, plan curvature, slope area ratio, topographic position index, soil type and land use), supported by automated R routines. In a first moment, the modelling strategy encompasses the creation of three independent blocks of landslide cases to be used for training (70 % of the landslides) and validation (30 % of the landslides) based on a random partition of the shallow slides inventory. In a second phase, each training group, for the different blocks, is randomly split in 14 new landslide sample groups, through a progressive increment of 5 % in the number of landslide cases included, from sample group 1 (with only 5 % of the total landslides) to sample group 14 (with 70 % of the total landslides), to obtain the shallow slides susceptibility scores. The validation of each of the 14 susceptibility map, from the different blocks, is done independently with the validation group of shallow slides (30 %) previously set aside and not used for susceptibility modelling. To accomplish that, we graphically compute prediction rate curves and calculate the respective area under the curve.N/

Validation of 3-day rainfall forecast at the regional scale

Nearly half of the natural disasters in the world are due to hydro-geomorphological hazards. Therefore, rainfall forecast is a key parameter for the implementation of landslides and flash-floods early warning systems. In this work we developed a routine in R software that enables the validation of a 3-day rainfall forecast by comparison with the daily rainfall data recorded in 101 automatic meteorological stations available in mainland Portugal. The routine integrates the pre-processing of base data, the matching between the 3-day rainfall forecast and the daily rainfall registered in the automatic meteorological stations based on sequence of days, the estimation of the difference between the forecasted and the real rainfall values and the computation of error measures, such as the bias, the mean absolute error, the mean absolute percentage error and the root mean square error. The results from the error measures, estimated for the 101 automatic meteorological stations, are then exported to an excel file. The routine is implemented for mainland Portugal and tested using data from February 2015, however, the spatial and temporal data can be easily updated for other regions

Validation of 3-day rainfall forecast at the regional scale

Nearly half of the natural disasters in the world are due to hydro-geomorphological hazards. Therefore, rainfall forecast is a key parameter for the implementation of landslides and flash-floods early warning systems. In this work we developed a routine in R software that enables the validation of a 3-day rainfall forecast by comparison with the daily rainfall data recorded in 101 automatic meteorological stations available in mainland Portugal. The routine integrates the pre-processing of base data, the matching between the 3-day rainfall forecast and the daily rainfall registered in the automatic meteorological stations based on sequence of days, the estimation of the difference between the forecasted and the real rainfall values and the computation of error measures, such as the bias, the mean absolute error, the mean absolute percentage error and the root mean square error. The results from the error measures, estimated for the 101 automatic meteorological stations, are then exported to an excel file. The routine is implemented for mainland Portugal and tested using data from February 2015, however, the spatial and temporal data can be easily updated for other regions. • A routine to validate the rainfall forecast at the regional scale using R programming language is implemented. • The automated routine can be easily updated and adapted with different spatial and temporal scales

Integration of landslide susceptibility maps for land use planning and civil protection emergency management

Landslides are one of the most relevant geomorphological hazards in Portugal, by the high levels of people affected, destruction of assets and disruption of economic and social activities. Regarding the Portuguese territorial land use planning and emergency management, regulation, practice, prevention and risk management have been promoted in different ways. In Portugal, the areas susceptible to landslides are included in the 'National Ecological Reserve', which is a public utility restriction legal figure that rules the land use planning at the municipal level. In addition, the Municipal Emergency Plans include landslide susceptibility maps that are combined with the map of the exposed elements, allowing the assessment of exposure to landslides. This study is applied to the Loures municipality located to the north of Lisbon. In this municipality 621 landslides registered in a landslide inventory (rotational slides, deep-seated translational slides and shallow translational slides) that affected 1,469,577 m2 (0.87 %) of the Loures territory. The final landslide susceptibility map shows that in Loures municipality 1,347 ha are associated to a Very high landslide susceptibility and 2,372 ha to High landslide susceptibility, which corresponds both to 22.1 % of the entire municipality, and constitutes the larger fraction of the National Ecological Reserve, related to landslides. These areas do not present geomorphological and geotechnical suitability for building structures or infrastructures. From the civil protection and emergency management point of views 34 classes of exposed elements were identified in the municipality, with point, linear and polygonal representations. The elements at risk located in the Very High or High landslide susceptibility classes were summarized and correspond to: high voltage poles; wind turbines; transmission/reception antennas; industrial areas; water tanks; silo; gas station/tank; service area; buildings of educational institutions; worship buildings; buildings of electricity facilities; regular buildings; gas pipeline; motorways; national roads; and municipal roads.info:eu-repo/semantics/publishedVersio

Rainfall-triggered landslides in the Lisbon region over 2006 and relationships with the North Atlantic Oscillation

Landslides occurred in the Lisbon area during the last 50 years were almost always induced by rainfall and have been used to establish rainfall thresholds for regional landslide activity. In 2006, three new rainfall-triggered landslide events occurred in the study area, namely on the 20 March, the 25–27 October, and the 28 November. Landslide events occurred in March and October 2006 include shallow translational slides and few debris flows, and the corresponding absolute antecedent rainfall was found to be above the threshold for durations ranging from 4 to 10 days. These events also fit the combined threshold of daily precipitation and 5 days calibrated antecedent rainfall values. Likewise the landslide event that took place in late November 2006 includes some slope movements with deeper slip surfaces, when compared with landslides dating from March and October. Moreover, the corresponding absolute antecedent rainfall was also found to be above the 40-day period rainfall threshold. Here we characterize in detail the short and long-term atmospheric circulation conditions that were responsible for the intense rainfall episodes that have triggered the corresponding landslide events. It is shown that the three rainfall episodes correspond to considerably different synoptic atmospheric patterns, with the March episode being associated to an intense cut-off low system while the October and November episodes appear to be related to more typical Atlantic low pressure systems (and associated fronts) travelling eastwards. Finally, we analyse the role played by the North Atlantic Oscillation (NAO) during those months marked by landslide activity. It is shown that the NAO index was consistently negative (usually associated with above average precipitation) for the months prior to the landslide events, i.e. between October 2005 and March 2006, and again between August and October 2006.info:eu-repo/semantics/publishedVersio

Evaluation of antioxidant and antimicrobial properties of the Angolan Cymbopogon Citratus essential oil with a view to its utilization as food biopreservative

It was studied the chemical composition, antioxidant, antibacterial and antifungal properties of the essential oil obtained from the Cymbopogon citratus of Angolan origin. Its major constituents analyzed by GC-MS were α-citral (40.55%), β-citral (28.26%), myrcene (10.50%) and geraniol (3.37%). The essential oil antioxidant capacity was statistically identical to that of synthetic antioxidants (DPPH IC50 of 41.7 μg/ml) and superior to that of extracts obtained from fresh leaves of the plant (DPPH IC50 of 55.7 μg/ml). The oil also demonstrated to possess high antibacterial activity even against multidrug resistant strains of Staphylococcus aureus, Staphylococcus epidermidis, Escherichia coli and Klebsiella pneumoniae and antifungal activity against Candida albicans and Non-Candida albicans, Candida parapsilosis and Candida tropicalis. The results of this study, in conjunction with already published data on the properties of other Cymbopogon citratus oils, provide evidence that it could have a potential application as food preservative.info:eu-repo/semantics/publishedVersio

Damaging flood risk in the Portuguese municipalities

Modeling and understanding the impact of climate change on flooding processes in Mediterranean climate areas, namely in southern Europe, is a complex endeavor, which must also consider exposure and vulnerability patterns. Assuming that vulnerability plays a relevant role in explaining the degree of loss due to natural hazards, the present research compares a flood-susceptibility index with a social-vulnerability index and a historical record of flood losses, both aggregated at the municipal level. The purpose of this research is to define municipal flood risk profiles that would rank the 278 municipalities and contribute to the strategic allocation of resources and flood risk management [...]info:eu-repo/semantics/publishedVersio

Enhancement of biomethane production from the anaerobic co-digestion of sewage sludge and macroalgae by continuous and intermittent addition of glycerol

Anaerobic digestion(AD) is a multifunctional bioprocess that allows nutrient recycling and reduction, production of biogas, and a sustainable bioenergy carrier. AD of macroalgae presents a promising source of bioenergy in the future. Macroalgae have high concentration of carbohydrates, making it suitable for biogas production, not competing with food crops for arable land and irrigation water. This work aimed to enhance the methane (CH4) production from the anaerobic co- digestion of a mixture of sewage sludge (SS from a wastewater treatment plant) and Ulva sp. (Ulv macroalgae), with continuous and intermittent addition of crude glycerol (cGly from vegetable oils), in a semi-continuous system. Three 5 L stirred tank reactors (R1, R2 and R3) were fed with SS and Ulv (85/15 in total solids). The reactors were operated at 37 °C, with a 4 L working volume and inoculated with anaerobic granular sludge from a brewery industry. Until day 179, the reactors were fed only with SS, while the hydraulic retention time (HRT) has been continuously decreasing from 40 d to 20 d. After reaching stabilization at HRT of 20 d, Ulv and cGly were added to feed (until day 241). R1 was the control, without cGly. In R2, cGly was continuously supplemented, 2 % (w) of the mixture of SS and Ulv. In R3, pulses of cGly were applied once a week, with same amount introduced in R2 since the last pulse. The AD of SS with an organic loading rate (g of COD of substrate per L of reactor and time) of 3.33 g L-1 d-1 achieved a CH4 production (MP, expressed in L of CH4 produced per kg of chemical oxygen demand (COD) of substrate fed L kg-1)) of 166 L kg-1 with 39 % of volatile solid (VS) reduction. The addition of Ulv (R1) decreased the MP in 20%. The continuous introduction of cGly (R2) improved significantly the MP, reaching 204 L kg-1 (51 % of VS reduction). Noteworthy, the intermittent addition of cGly (R3) showed the best results in terms of MP, 251 L kg-1 achieving 56 % of VS reduction

Regional rainfall thresholds for landslide occurrence using a centenary database

This work proposes a comprehensive method to assess rainfall thresholds for landslide initiation using a centenary landslide database associated with a single centenary daily rainfall data set. The method is applied to the Lisbon region and includes the rainfall return period analysis that was used to identify the critical rainfall combination (cumulated rainfall duration) related to each landslide event. The spatial representativeness of the reference rain gauge is evaluated and the rainfall thresholds are assessed and calibrated using the receiver operating characteristic (ROC) metrics. Results show that landslide events located up to 10 km from the rain gauge can be used to calculate the rainfall thresholds in the study area; however, these thresholds may be used with acceptable confidence up to 50 km from the rain gauge. The rainfall thresholds obtained using linear and potential regression perform well in ROC metrics. However, the intermediate thresholds based on the probability of landslide events established in the zone between the lower-limit threshold and the upper-limit threshold are much more informative as they indicate the probability of landslide event occurrence given rainfall exceeding the threshold. This information can be easily included in landslide early warning systems, especially when combined with the probability of rainfall above each threshold.info:eu-repo/semantics/publishedVersio