- Dept. of Geography, Geosciences Institute
Av. Athos da Silveira Ramos, 274, Bloco H1, sala 8,
Cidade Universitária, Rio de Janeiro, RJ, 21044-020
Brazil - ++ 55 21 998510394
Nelson F Fernandes
Universidade Federal do Rio de Janeiro (UFRJ), Geography, Faculty Member
- Slope Stability and Landslides, Hillslope hydrology, Landslide Modeling and Prediction, Soil Science, Modeling and Simulation, Ecosystem Services, and 5 moreSoil Erosion, Quantitative Geomorphology, Long-term landscape evolution, Isotope Hydrology, and Critical Zone Science(Soil Erosion, Quantitative Geomorphology, Long-term landscape evolution, Isotope Hydrology, and Critical Zone Science)edit
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<p>The river system plays a very important role in denudation processes and, consequently, in relief evolution in non-glacial landscapes. Several theoretical and empirical studies have contributed to a better understanding... more
<p>The river system plays a very important role in denudation processes and, consequently, in relief evolution in non-glacial landscapes. Several theoretical and empirical studies have contributed to a better understanding of how rivers change after modifications in their boundary conditions, such as tectonics or climate. The region of the Middle Valley of Paraíba do Sul (MVPS) has important records of recent drainage captures, which show a state of transition of the landscape and, consequently, a reorganization of the drainage networks. This region is in the Southeast of Brazil, topographically characterized as an area with escarpment of passive continental margin, where, close to the coast, the Serras do Mar and Serra da Mantiqueira stand out. The relief of the PSMV area and its respective drainage network had its evolution conditioned to the tectonic and climatic events that occurred during the Cenozoic. The oldest tectonic event is described as a NW-SE (E1) stretch, of Paleogenic age, followed by an E-W sinistral transcurrence (TS) event in the Neogene and a dextral transcurrence (DT) event, which occurred in the Pleistocene-Holocene. Finally, the extension event (E2) in the Holocene was associated with generalized reactivations of NE-SW structures, locally related to the generation of grabens, such as the Rio Bananal graben.Although of great importance in studies involving relief evolution, there are still few works that use river profiles and fluvial gradient indices such as χ and ksn to analyze the role of river captures in the reorganization of drainage networks and their relationship with neotectonics. Thus, the present study aims to investigate the causes of the reorganization of the drainage network in the MVPS region and its relationship with the evolution of the relief and its respective neotectonic activity. The E1 event was responsible for the consolidation of the hemi-graben configuration of the sedimentary basins in the MVPS. The normalized steepness index calculated for the main rivers demonstrates that this configuration possibly established a greater erosive power for the basins that drained the active fault, represented by the basins of the northern sector of the study area. During the Neogene, the TS event occurred, responsible for the inflections of the main channels to N-NW. These inflections are marked by knickpoints and sudden changes of χ and ksn in the fluvial profiles of the main channels. The paleotension analysis showed that structures associated with the TD event may be related to the filling and clogging of valleys with alluvium-colluvium ramps. The E2 event generated a system of normal transcurrent faults associated with a NW-SE Holocene extensional regime, responsible for captures oriented preferentially to SE and secondarily to NW. In the field, the relationship between TD and E2 was observed: the first related to NW-SE triangular facets and filling by valleys with alluvial-colluvium ramps and then, the fluvial capture promoted by E2. The Chi-z fluvial profiles and longitudinal profiles corroborate this model, indicating migration of the dividers compatible with the main capture directions observed.</p>
Research Interests: Geology, Paleontology, Tectonics, Holocene, Neogene, and 5 moreCenozoic, Fluvial, Denudation, Escarpment, and Drainage basin
<p>Hillslope hydrology is a major factor controlling the spatial and temporal distribution of landslides in the mountainous landscape of southeastern Brazil. Previous studies have attested that the movement of water through... more
<p>Hillslope hydrology is a major factor controlling the spatial and temporal distribution of landslides in the mountainous landscape of southeastern Brazil. Previous studies have attested that the movement of water through preferential soil paths and bedrock fractures contributes to the development of hydrologic conditions required to trigger landslides in the region. In Rio de Janeiro, the upper portions of many hillslopes are characterized by rocky outcrops of unweathered granites and gneisses, with thick talus deposits on the lower parts. Although most hydrological studies carried out in the region consider the surficial effects of the impermeable rocky surfaces, the effects of fractures on infiltration and exfiltration have not been extensively considered, as well as lateral flows at the soil-bedrock boundary. In this study, we monitor an experimental hillslope in the city of Petrópolis (Rio de Janeiro) to understand how the rocky outcrops, the fractures present in the bedrock and the talus deposit stratigraphy interact and define the hydrological behavior of this environment. Three matric potential nests were installed in a transect along the hillslope (upper, middle and lower portions), each one with 7 sensors installed from the soil surface to the soil-bedrock boundary (between 4.0 and 5.0 m depths), with readings every one hour. The main soil physical properties were characterized on the samples retrieved from the drillings and two geophysical methods were integrated, the GPR (Ground Penetrating Radar) to investigate soil depth and the VLF (Very Low Frequency) to map bedrock fractures. Our results suggest the occurrence of preferential subsurface flows conditioned by soil stratigraphy and the presence of fractures in the bedrock. The rocky outcrop causes an increase in soil moisture in the upper soil layers in the upper and middle positions of the hillslope, favoring the entrance of water into the upper parts and the generation of lateral and ascending subsurface flows along the soil-rock interface zone during heavy rains. Geophysical data suggests that the talus deposit has a higher concentration of boulders in the middle and upper portions of the hillslope and the presence of bedrock discontinuities that were interpreted as fractures that have the same NE-SW dip direction of the main regional trend. Our results suggest that both the rocky outcrop and the bedrock fractures control the development of subsurface flows and the generation of high positive pore-pressures along the hillslope profile.</p>
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<p>Landslides are natural phenomena that cause significant socioeconomic and environmental impacts in mountainous regions. Statistical models used to predict landslides frequently use Digital Terrain Models (DMTs) to... more
<p>Landslides are natural phenomena that cause significant socioeconomic and environmental impacts in mountainous regions. Statistical models used to predict landslides frequently use Digital Terrain Models (DMTs) to identify scars and to generate thematic maps representing relevant causative factors (e.g., slope, aspect, curvature).The topographical causative factors tell us how some morphometrical parameters control slope stability and the algebraical combination of weighted causative factors (the landslide susceptibility map) displays how the global relationship of the causative factors generates the landslides. However, these DTMs will no longer be representative of the topographical features that triggered landslides when obtained after the occurrence of this events (post-failure DTM) and using archetypal morphometric signatures of past landslides in statistical models will imply relevant conceptual mistakes. A possible solution to this problem is to assume that the pre-rupture topography can be inferred from undisturbed areas adjacent to scars. This work presents a topography reconstruction method using LIDAR elevation points to generate a pre-failure topography DTM from a post-failure topography DTM. The pre-failure topography was used in a bivariate statistical model (Weights of Evidence) to predict landslides in the Quitite and Papagaio basins, in the city of Rio de Janeiro (Brazil). Seven landslide susceptibility models were produced by combining eight conditionally independent causative factors and had their predictive capacity tested by calculating the area under curve (AUC). The final model (AAC = 0.77) highlights the direct topographic and hydrological controls and the indirect lithological and structural controls on the landslides. Landslides are mainly controlled by slopes between 26° and 52°, on North, Northeast and Northwest facing slopes, on concave curvatures with values of a contribution area between 1.8m² e 4.1m². The results take into account the model’s assumptions and provide a synthesized and robust view of the prone landslides areas in an environment of great geodiversity.</p>
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ABSTRACT Mass movements are recurrent phenomena in the whole Mountain Region of the State of Rio de Janeiro in Brazil. These events actively participate in the relief evolution and are also responsible for many damages and loss of human... more
ABSTRACT Mass movements are recurrent phenomena in the whole Mountain Region of the State of Rio de Janeiro in Brazil. These events actively participate in the relief evolution and are also responsible for many damages and loss of human lives. The triggering of these events depends on the natural environment and the preparatory and immediate action of the physical, biotic and human agents responsible for these processes. This work is based on the hypothesis in which the topographical conditions have a major effect on the spatial distribution of translational landslides caused by decreased of the internal resistance of the material mobilized. Therefore, the purpose of this study is to identify the topographical conditions favorable to landslide triggering based on morphometric analysis in a pilot watershed - D'antás watershed - located in the mountainous region of the State of Rio de Janeiro. The indices include the topographic wetness index (TWI), contributing area, slope angle and elevation and were derived from 5-m grid digital terrain model, computed on a Geographic Information System (GIS). The maps produced allowed the analysis of topographic influence on the landslides distribution from the indices of frequency classes (F), concentration of scars (CC) and potential of landslide (PL). The landscape sectors that are more likely to be affected by landslides were the ones where the elevation ranges from 1070m - 1187m, slope angle between 40.95° and 47.77°, contributing area between (log10) 1.32 m² - 1.95 m² and topographic wetness index between 7.11 to 9.59. This work provides important information which may help in the decision-making process, using fewer data and indices of easy application. Finally, the results obtained will subsidize of a landslide susceptibility map through the implementation of the conditional probability method aimed at predicting and mitigating of the damage caused by landslides.
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In the northwest part of Rio de Janeiro state water availability is one of the main limiting factors for human development and crop productivity. In the same way that shortage of freshwater is one of the main problems, the tomato... more
In the northwest part of Rio de Janeiro state water availability is one of the main limiting factors for human development and crop productivity. In the same way that shortage of freshwater is one of the main problems, the tomato production systems waste water and highly degrade the environment. The search for the water use efficiency is a challenge in
Research Interests: Irrigation, Human Development, Agriculture, Environmental Sustainability, Groundwater recharge, and 15 moreNo tillage, Atlantic Forest, Drip Irrigation, Land Use, Minimum Tillage, Crop Production, Human development index, Crop Residue Burning, Green Manure, Environmental Impact, Conventional tillage, Management Strategy, Production System, Crop Residue, and Environmental Problem
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<p>Both internal and external Earth’s dynamics are constantly changing the landscapes and one of the most influent external components are the fluvial processes, altering the relief through erosion and fluvial... more
<p>Both internal and external Earth’s dynamics are constantly changing the landscapes and one of the most influent external components are the fluvial processes, altering the relief through erosion and fluvial deposition, as well as through its respective drainage network’s reorganization. The drainage basins dynamics seeks to achieve a balance between tectonic uplift and river erosion. The use of parameter <em>Chi</em> (χ) allows a comparison of basins in different scales, erosion and uplift rates, making it possible to determinate its steady or transient state and comprehends the dynamics de divisor migration of basins. Although the great advances have been reached in last decades, there are still many questions without answer. For the accomplishment of this study, two areas in the Serra do Mar of São Paulo and Paraná were chosen due to the presence of important river captures, which generated significant reorganizations in the drainage network. Furthermore, cosmogenic isotopes (<sup>10</sup>Be) data from existent literature in Serra do Mar of Paraná allows the estimation of the denudation rate of these basins in the long term. In this study, these rates are analyzed combined with values of <em>Chi</em>, verifying the influence of the captured rivers, which contribute to the understanding of landscape evolution. This study uses the Digital Elevation Model (DEM) SRTM 30m. The DEM data were treated in ArcGIS and analyzed in MATLAB, where oceanic and continental basins were selected, considering sea level as the base level. The analysis was made through functions of <em>Topographic Analysis Kit</em> (TAK), integrated to <em>TopoToolBox</em>, to generate longitudinal and elevation-Chi profiles and <em>Chi</em> maps plotted with knickpoints data and, for the Paraná basins, the product obtained were simultaneously analyzed with <sup>10</sup>Be data. From the analysis of these data, was possible to notice the ocean basins are capturing the continental basins and, therefore, that these basins are in a transient state, which means that their divisor is migrating towards higher Chi values, thus, towards the interior of the continent. In Paraná basins, the retreating areas of the Serra do Mar escarpment directly related to places of high erosion rates on the oceanic slope. These results, although preliminary, attest the potential of analysis methods used, proving the influence of river captures in the disruption of the steady state between adjacent drainage basins located on the oceanic and continental slopes, as well as their influence on the differentiated retreat in the Serra do Mar escarpment.</p>
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<p>In the last few decades, many studies have focused on the hydrologic effects and sediment regulation by LULC changes. Besides, land degradation by soil erosion is a major problem in many tropical developing countries,... more
<p>In the last few decades, many studies have focused on the hydrologic effects and sediment regulation by LULC changes. Besides, land degradation by soil erosion is a major problem in many tropical developing countries, particularly when natural vegetation is converted to farmland. In Brazil, the MATOPIBA Region located in the Cerrado biome, has been considered the greatest national agricultural frontier, responsible for a large part of the Brazilian production of grains and fibers. The flat topography, the deep soils and the favorable climate for the cultivation of the main crops of grains favored the accelerated agricultural expansion in the last 30 years. In order to analyze and measure erosion and sediment regulation in the Rio Grande watershed were performed using two models: InVEST and ARIES. The aim of the InVEST model is to map and quantify the sediment delivery and retention services. It is a spatially-explicit model working with calculations at the pixel scale. The ARIES program works through ecosystem services modeling and calculations that, depending on the used module, considers both supply and demand. The mean sediment retention, in InVEST model, which is the difference in the amount of sediment delivered by the current watershed and a hypothetical watershed where all land use types have been converted to bare ground, was 42.76 ton/year/ha. These results should be taken as a good first estimate of the current scenario for the sediment retention service. This is due to some limitations of the SDR model. It uses the revised universal soil loss equation (RUSLE), which is limited in scope with regards to sediment source. ARIES model, for the Sediment Regulation analysis, used RUSLE to calculate soil loss and soil retention by vegetation in tons of sediments per hectare per year. The data of rain erosivity comes from the Global Rainfall Erosivity database (factor <em>R</em>) and the soil erodibility data (factor <em>K</em>) from Soil Grids. The sediment retention calculation is done through the application of RUSLE twice, first with the current land use and land cover and then with bare soil (Martínez-López et al., 2019). Then a subtraction is made between the two outputs, which determines the collaboration that current use and coverage has on sediment retention. The basin presents a mean value of 905.37, standard deviation of 1854.58 and maximum and minimum value of 39982.67 and 0, respectively. A limitation of the InVEST sediment model compared and ARIES is the temporal and spatial scale of its outputs. It is able to provide only average annual impacts under steady state conditions, limiting the model’s usability for ecosystem services in need of assessment via timescales shorter than one year.</p>
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Landslides are natural processes triggered by complex relationships between many conditioning factors. In Rio de Janeiro city, intense rainstorms combined with steep slopes, usually occupied by slums, create favourable conditions for... more
Landslides are natural processes triggered by complex relationships between many conditioning factors. In Rio de Janeiro city, intense rainstorms combined with steep slopes, usually occupied by slums, create favourable conditions for landslide generation. In general, slope failures are related to high positive pore‐pressures inside soil mantles, which are associated with topographic hollows and hydraulic discontinuities inside the deep weathered profile.This study aims to characterize the role played by spatial variations in saturated soil hydraulic conductivity Ksat on landsliding in the Papagaio Basin (2·5 km2), triggered by intense rainstorms (250 mm in less than 2 days) in February 1996. Field measurements, using the Guelph permeameter, were conducted along soil profiles (up to 5·0 m depth), around and inside landslide scars representing different geomorphological domains. Also, soil physical properties (grain size, total porosity, macroporosity, microporosity, etc.) were evaluated at the 87 sites where Ksat was measured.Despite the many geological and pedological variations inside the basin, including changes in lithology, fracture density, vegetation type and succession stage, soil characteristics and weathering stage, and human activities, 94% of the Ksat values varied by only two orders of magnitude (1·0 × 10−6–9·0 × 10−5 m s−1). However, abrupt changes in Ksat were observed along some of the soil profiles studied, e.g. an increase of two orders of magnitude in only 0·30 m. These hydraulic discontinuities may contribute locally to the development of high pore pressures during intense rainstorms, leading to landsliding. The results also suggest that different Ksat variation patterns coexist inside the basin, which should be considered in mathematical models of landslide prediction. Copyright © 2004 John Wiley & Sons, Ltd.
Research Interests: Environmental Engineering, Civil Engineering, Geology, Geomorphology, Hydraulics, and 15 moreGeotechnical Engineering, Fracture, Density, Lithology, Hydraulic conductivity, Mathematical Models, Grain size, Landslide, Mathematical Model, Human Activity, Pore Pressure, Condition Factor, Physical Properties, Hydrological Processes, and Field Measurement
Research Interests: Engineering, Civil Engineering, Geology, Engineering Geology, Topography, and 15 moreRio de Janeiro, Performance Model, DEM, Landslide, Digital Elevation Model, Comparative modeling, Parameterization, Soil Properties, Topographic, Physics based Modeling, Bulk Density, Laboratory Tests, Site Analysis, Model performance, and Model test
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Advances in smart grids and in communication networks allow the development of an interconnected system where information arising from different sources helps building a more reliable electrical network. Nevertheless, this interconnected... more
Advances in smart grids and in communication networks allow the development of an interconnected system where information arising from different sources helps building a more reliable electrical network. Nevertheless, this interconnected system also brings new security threats. In the past, communication networks for electrical systems were restrained to closed and secure areas, which guaranteed network physical security. Due to the integration with smart meters, clouds, and other information sources, physical security to network access is no longer available, which may compromise the electrical system. Besides smart grids bring a huge growth in data volume, which must be managed. In order to achieve a successful smart grid deployment, robust network communication to provide automation among devices is necessary. Therefore, outages caused by passive or active attacks become a real threat. This chapter describes the main architecture flaws that make the system vulnerable to attacks for creating energy disruptions, stealing energy, and breaking privacy.
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... Rio de Janeiro: A Metropolis Between Granite-Gneiss Massifs. by Nelson F Fernandes, Miguel Tupinambá, Claudio L Mello ... Abstract. The city of Rio de Janeiro is well-known for its outstanding landscape, particularly the several steep... more
... Rio de Janeiro: A Metropolis Between Granite-Gneiss Massifs. by Nelson F Fernandes, Miguel Tupinambá, Claudio L Mello ... Abstract. The city of Rio de Janeiro is well-known for its outstanding landscape, particularly the several steep rocky domes that emerge close to the coast. ...
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Mass movements are common phenomena especially during strong rainfall events that take place frequently in the summer season. These phenomena have been causing losses of lives and serious damage to roads, bridges, and properties. Among... more
Mass movements are common phenomena especially during strong rainfall events that take place frequently in the summer season. These phenomena have been causing losses of lives and serious damage to roads, bridges, and properties. Among them, stand out the landslides that many times produce debris flows. The aim of this study is develop a methodology, which combines a model to
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Uranium mining and processing constitute the front-end of the nuclear fuel-cycle and respond for most of its radiological impacts. For many years it has been accepted that the key driving force associated with these radiological impacts... more
Uranium mining and processing constitute the front-end of the nuclear fuel-cycle and respond for most of its radiological impacts. For many years it has been accepted that the key driving force associated with these radiological impacts was related with radon exhalation from mill tailings. However, evidences coming from other mining sites showed that impacts in superficial and ground waters could
Research Interests: Environmental Science, Environmental modeling, Environmental Monitoring, Groundwater modeling, Groundwater Management, and 15 moreImpact Assessment, Ground Water, Nuclear Fuel Cycle, Groundwater flow, Semi Arid Region, Three Dimensional, Water Quality, Water Level, Water Flow, Front end, Uranium Mining, Sustainability, Sulfuric Acid, Northeastern Brazil, and Driving force
Landslides are major processes controlling landscape evolution, especially in tropical environments, where thick talus and colluvial deposits are observed filling bedrock topographic hollows and larger valleys. Besides their... more
Landslides are major processes controlling landscape evolution, especially in tropical environments, where thick talus and colluvial deposits are observed filling bedrock topographic hollows and larger valleys. Besides their geomorphological meaning, they also represent an enormous danger to man when soil-mantled steep hillslopes are densely occupied in urban areas. In Brazil, especially in southern and southeastern portions, due to the steep
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Landslides are natural phenomena that model the terrain and cause great damage to humanity, both financially and in terms of loss of life. Therefore predicting this phenomenon is extremely important as it can lead to better city planning... more
Landslides are natural phenomena that model the terrain and cause great damage to humanity, both financially and in terms of loss of life. Therefore predicting this phenomenon is extremely important as it can lead to better city planning and a more effective preventative containment work. Of the various scientific models proposed to date, the SHALSTAB model stands out. It combines a hydrological model and a hillside instability model (based on the Infinite Slope equation). SHALSTAB has been obtaining very good results in areas of the western United States and also in tropical areas. The objective of this work is to define in the terrain, areas more sensitive to landslides and analyze the efficiency of the model using topographical data of different scales. To do this it is necessary to generate a digital elevation model and obtain geomorphologic parameters (such as slope and contribution area) in order to identify the risk areas in the terrain. A high-resolution photogrammetric enlarger was used to create a 1:10,000 scale map of landslide source areas, run off tracks, and deposits. This was then georeferenced to the high resolution DEM. The SHALSTAB performance was verified comparing the unstable pixel in the fall within landslide scat's. The results show that the 80% of the SHALSTAB performance from 1:10,000 scale topographic data was located in unstable classes. However, the model performance from 1:50,000 scale decreases to 50%. In addition, the performance from 1:10,000 scale just 1% of the scar fall at stable class on the other hand around 18% fall in this class when a 1:50,000 scale is used. Thus, we suggest that greater effort and emphasis should be placed on acquisition of high-resolution, high quality topographic. A 50,000 scale can be used in order to determine preliminary landslides hazard areas but it is necessary to have a 1:10,000 scale to increase model performance in critical areas.
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ABSTRACT