A carregar...
Pessoa
Maria Neto Paixão Vazquez Fernandez Martins, Helena
10 resultados
Resultados da pesquisa
A mostrar 1 - 10 de 10
- Mapping the spatial variability of rainfall from a physiographic-based multilinear regression: model development and application to the Southwestern Iberian PeninsulaPublication . Ruiz-Ortiz, Verónica; G. P. Isidoro, Jorge M.; Fernandez, Helena Maria; Granja-Martins, Fernando M.; García-López, SantiagoA physiographic-based multilinear regression model supported by GIS was developed to estimate spatial rainfall variability in the Southwest Iberian Peninsula. The area study includes a wide diversity of landscape features and comprises four Portuguese regions and one Spanish province (totalizing 28,860 km(2)). The region suffers a very strong Mediterranean influence, with a major cleavage between winter and summer seasons. Thus, the analysis was carried out separately for the wet (October to March) and dry (April to September) semesters. From an initial set of 10 explanatory physiographic variables, five were selected to be used in the multilinear regression, as they allowed generating models by map algebra that fitted well with the last 40 years of monthly rainfall data records. These records were obtained from 163 weather stations, filtered from an initial set of 230 (142 stations in Portugal and 88 in Spain). The correlation between the physiographic-based multilinear regression model and a model obtained by interpolation from rainfall historical data showed to be good or very good in approximately 75% of the area under study. Results show that physiographic-based models can be effectively used to estimate rainfall where there is a lack of rain gauges, or to densify spatial resolution of rainfall between rain gauges.
- Propriedades hidráulicas de solos algarvios em cenário pós-incêndioPublication . Fernandez, Helena Maria; Costa, Rui; Lança, Rui; Almeida, Soraia; Da Silva, Elisa Maria De Jesus; Granja-Martins, Fernando M.; Matos Fernandes, M.; Topa Gomes, A.; Couto Marques, J.; Rios, S.; Ferreira, C.; Vieira, C.; Alves Costa, P.; Leitão Borges, J.; Menezes, J.A ocorrência de incêndios florestais tem implicações nas propriedades hidráulicas dos solos. (Pierce et al., 2004), devido ao aparecimento de uma camada superficial de cinzas por combustão da mata e arvoredo. A fim de caracterizar a modificação das propriedades hidráulicas do solo devido à presença de incêndios florestais, foi realizada uma campanha experimental em que se recolheram amostras de solo da Serra Algarvia e do litoral Algarvio, sob as quais foram realizados ensaios de simulação de incêndio. Foram de igual modo realizados ensaios para caracterização das propriedades físicas dos solos em questão e sua classificação. Na simulação dos ensaios de incêndio foram consideradas diferentes quantidades de material combustível. Em seguida, realizaram-se novos ensaios para determinar o teor em água no solo e realizaram-se também ensaios de infiltração, com infiltrómetro de duplo anel, de modo a determinar a condutividade hidráulica quase saturada (Ks) e a sorvidade (S) nas diferentes amostras.
- Análise dos Incêndios Florestais num período de 30 anos (1990-2017). Caso de estudo Concelho de Mação (Portugal)Publication . Fernandez, Helena Maria; Granja-Martins, Fernando M.; Fernandes, PatríciaAs mudanças climáticas globais são uma temática de grande destaque na nossa sociedade, surgindo, inevitavelmente, associado a esta preocupação, o aumento dos gases de efeito de estufa (GEE) presentes na atmosfera. Segundo Chuvieco et al. (2007) os incêndios florestais são responsáveis por quase 40% das emissões totais de CO2, aumentando significativamente na contribuição dos GEE na atmosfera. Uma forma de compreender os fluxos associados ao carbono é o estudo da quantificação da biomassa florestal, que atua como sumidouro. Ao ocorrer um incêndio florestal, esta dinâmica fica profundamente afetada (Celes et al., 2013).
- Comparison of ratioing and RCNA methods in the detection of flooded areas using Sentinel 2 Imagery (case study: Tulun, Russia)Publication . Fernandez, Helena Maria; Granja-Martins, Fernando M.; Dziuba, Olga; Pereira, David A. B.; Isidoro, Jorge M. G. P.Climate change and natural disasters caused by hydrological, meteorological, and climatic phenomena have a significant impact on cities. Russia, a continental country with a vast territory of complex geographic–ecological environments and highly variable climatic conditions, is subject to substantial and frequent natural disasters. On 29 June 2019, an extreme precipitation event occurred in the city of Tulun in the Irkutsk oblast, Russian Federation, which caused flooding due to the increase in the water level of the Iya River that passes through the city, leaving many infrastructures destroyed and thousands of people affected. This study aims to determine the flooded areas in the city of Tulun based on two change detection methods: Radiometric Rotation Controlled by No-change Axis (RCNA) and Ratioing, using Sentinel 2 images obtained before the event (19 June 2019) and during the flood peak (29 June 2019). The results obtained by the two methodologies were compared through cross-classification, and a 98% similarity was found in the classification of the areas. The study was validated based on photointerpretation of Google Earth images. The methodology presented proved to be useful for the automatic precession of flooded areas in a straightforward, but rigorous, manner. This allows stakeholders to efficiently manage areas that are buffeted by flooding episodes.
- An assessment of forest fires and CO2 gross primary production from 1991 to 2019 in Mação (Portugal)Publication . Fernandez, Helena Maria; Granja-Martins, Fernando M.; Pedras, Celestina M. G.; Fernandes, Patrícia; Isidoro, JorgeForest-fire rates have increased in Southern European landscapes. These fires damage forest ecosystems and alter their development. During the last few decades, an increase in fast-growing and highly fuel-bearing plant species such as bush, Eucalyptus globulus Labill., and Pinus pinaster Ait. has been observable in the interior of Portugal. This study aims to verify this assumption by the quantification of the biomass carbon sink in the forests of the Mação municipality. Maps of fire severity and forest biomass evolution after a wildfire event were produced for the period of 1991 to 2019. To quantify carbon retention in this region, this evolution was correlated with gross primary production (GPP) on the basis of satellite imagery from Landsat 5, Landsat 8, and MODIS MYD17A2H. Results show that wildfires in Mação increased in area and severity with each passing decade due to the large accumulation of biomass promoted by the abandonment of rural areas. Before the large fires of 2003, 2017, and 2019, carbon rates reached a daily maximum of 5.4, 5.3, and 4.7 gC/m2/day, respectively, showing a trend of forest-biomass accumulation in the Mação municipality.
- Mapping rainfall aggressiveness from physiographical data: application to the Grândola Mountain Range (Alentejo, Portugal)Publication . Fernandez, Helena Maria; Granja-Martins, Fernando M.; Isidoro, Jorge M. G. P.The South of the Iberian Peninsula is subject to long periods of drought followed by heavy rain events over shallow soils, promoting soil loss. The Modified Fournier Index (MFI) is a good indicator of this process; however, MFI is sometimes difficult to assess due to the scarcity of rainfall data. This study proposes a methodology using MFI and supported by a geographic information system (GIS) and geostatistics to map rainfall aggressiveness with scarce spatial rainfall data, where physiographic variables are used to overcome the lack of rainfall data. The Grândola Mountain Range in the Alentejo region, Portugal, is presented as a case study. This area is a CORINE biotope, currently under application to the Natura 2000 network, and should be considered as a priority for the conservation of the environment. The model allowed us to create a map of rainfall aggressiveness, classified according to CORINE-CEC, found to be Moderate in the mountains and Low in the coastal area of the Grândola Mountain Range. This cartography is an important tool for local and national stakeholders and authorities with responsibilities in planning and protection of the territory. The methodology can be used in regions with scarce spatial rainfall data to assess areas susceptible to rainfall-induced soil erosion.
- A multimethod interpolation approach for mapping the spatial distribution of rainfall in southwest Iberian PeninsulaPublication . Ruiz-Ortiz, Verónica; Maria Neto Paixão Vazquez Fernandez Martins, Helena; Granja Martins, Fernando Miguel; Vélez-Nicolás, Mercedes; Isidoro, Jorge; García-López, SantiagoEight spatial interpolation models were used to map the spatial distribution of precipitation in the southwestern sector of the Iberian Peninsula (22330 km2) over 40 years (1980/1981-2019/2020). Rainfall data from 103 meteorological stations were used to generate the interpolation models, namely inverse distance weight (IDW) with 6, 12 and 24 points, regression spline (RS), thin spline (TS), universal kriging with spherical and Gaussian variogram (UK_Sphe and UK_gauss, respectively) and multilinear regression (MR), based on physiographic and geographic variables. Furthermore, 32 rainfall stations were used to assess the performance of the previous methods through 7 statistical metrics Ordinary Least Squares (OLS), Root Mean Square Error (RMSE), Normalized root mean square error (NRMSE), Coefficient of determination (R2), Nash-Sutcliffe efficiency coefficient (NSE), Mean Absolute Error (Bias and MAE). Based on these metrics, UK_gauss and IDW_6 provided the best adjustments, whereas MR presented the highest errors. All methods were suitable to predict the spatial distribution of rainfall, but adjustments are conditioned by the features of the study area, gauge density and gauge spatial distribution.
- Geographic information system in the optimization of tourist routes in the city of Faro (Algarve, Portugal)Publication . Granja Martins, Fernando Miguel; Maria Neto Paixão Vazquez Fernandez Martins, HelenaThis work aims to map the optimal routes based on time and distance, via e-scooters and walking, to visit 54 historical heritage sites in Faro. Implementing these routes promotes environmental sustainability by reducing CO2 emissions and encouraging healthier, greener tourism. The route optimization was conducted in ArcGIS, utilizing the Network Analyst extension and vector data obtained from OpenStreetMap. The results showed that there are routes that can be completed in one or more days, depending on visitors' availability, physical capacity, or their chosen method of transportation. The optimal route to visit the 54 historical heritage sites forms a closed circuit spanning 17.35 km. If visits are split into two routes, one covering 31 monuments in the old city and the other 24 monuments in the exterior area of the urban center, the optimal closed-circuit routes measure 6.16 km and 11.31 km, respectively. This study is expected to enhance tourism promoted by the Faro municipality and make it more environmentally friendly.
- GIS-based site selection for agricultural water reservoirs: a case study of São Brás de Alportel, PortugalPublication . Dziuba, Olga; Custódio, Cláudia; Silva, Carlos Otero; Granja Martins, Fernando Miguel; Lança, Rui; Maria Neto Paixão Vazquez Fernandez Martins, HelenaIn the São Brás de Alportel municipality, water scarcity poses a significant constraint on agricultural activities. This study utilises Remote Sensing (RS) and Geographical Information Systems (GISs) to identify existing irrigated areas, delineate catchment basins, and select the most suitable sites for the installation of new surface water reservoirs. First, the principal territorial components were characterised, including physical elements (climate, geology, soils, and hydrography) and anthropogenic infrastructure (road network and high-voltage power lines). Summer Sentinel-2 satellite imagery was then analysed to calculate the Normalised Difference Vegetation Index (NDVI), enabling the identification and classification of irrigated agricultural parcels. Flow directions and accumulations derived from Digital Elevation Models (DEMs) facilitated the characterisation of 38 micro-catchments and the extraction of 758 km of the drainage network. The siting criteria required a minimum setback of 100 m from roads and high-voltage lines, excluded farmland currently in use, and favoured mountainous areas with low permeability. Only 18.65% (2854 ha) of the municipality is agricultural land, of which just 4% (112 ha) currently benefits from irrigation. The NDVI-based classification achieved a Kappa coefficient of 0.88, indicating high reliability. Three sites demonstrated adequate storage capacity, with embankments measuring 8 m, 10 m, and 12 m in height. At one of these sites, two reservoirs arranged in a cascade were selected as an alternative to a single structure exceeding 12 m in height, thereby reducing environmental and landscape impact. The reservoirs fill between October and November in an average rainfall year and between October and January in a dry year, maintaining a positive annual water balance and allowing downstream plots to be irrigated by gravity. The methodology proved to be objective, replicable, and essential for the sustainable expansion of irrigation within the municipality.
- Evaluation of the impact of sustainable drainage systems (SuDSs) on stormwater drainage network using giswater: a case study in the metropolitan area of Barcelona, SpainPublication . Araújo, Suelen; Lança, Rui; Silva, Carlos Otero; Torret, Xavier; Granja Martins, Fernando Miguel; Maria Neto Paixão Vazquez Fernandez Martins, HelenaTo mitigate the impacts of urbanisation and the attendant surface sealing, appropriate measures are required when adapting urban spaces and drainage infrastructure. In this context, the deployment of Sustainable Drainage Systems (SuDSs) has emerged as a viable alternative, delivering highly positive outcomes by enhancing hydrological, hydraulic and landscape performance while restoring ecosystem services to the community. This study evaluates the relative performance of five SuDS typologies, green roofs, bioretention cells, infiltration trenches, permeable pavements, and rain barrels, implemented in a 64 ha subbasin of the metropolitan area of Barcelona, Spain. Using Giswater integrated with the SWMM, the stormwater drainage network was modelled under multiple rainfall scenarios. Performance was assessed using two qualitative indicators, the junction index (Ij) and the conduit index (Ic), which measure surcharge levels in manholes and pipes, respectively. The results show that SuDS implementation affecting 42.8% of the drained area can enhance network performance by 35.6% and reduce flooded junctions by 67%. Among the typologies, rain barrels and bioretention cells were the most effective. The study concludes that SuDS construction, supported by open-source tools and performance-based indicators, constitutes a replicable and technically robust strategy for mitigating the effects of surface sealing and increasing urban resilience.