Nelson F Fernandes | Universidade Federal do Rio de Janeiro (UFRJ) (original) (raw)

Papers by Nelson F Fernandes

Journal of Earth System Science, 2020

Landslide is a normal geomorphic process that becomes hazardous when interfering with any develop... more Landslide is a normal geomorphic process that becomes hazardous when interfering with any development activity. It has been noted that *400 causalities occur in the Himalayan region every year due to this phenomenon. The frequency and magnitude of the landslides increase every year, particularly in the hilly townships. This demands the large scale landslide susceptibility, hazard, risk, and vulnerability assessment of the region to be carried out. In the present study, Mussoorie Township and its surrounding areas located in the Lesser Himalaya has been chosen for Landslide Susceptibility Mapping (LSM) that involved bivariate statistical Yule coefBcient (YC) method. It calculates the binary association between landslides and its various possible causative factors like lithology, land use-landcover (LULC), slope, aspect, curvature, elevation, road-cut, drainage, and lineament. The results indicate that *44% of the study area falls under very high, high and moderate landslide susceptible zones and *56% in the low and very low landslide susceptible zones. The dominant part of the area falling under high and moderate landslide susceptible zones lies in the area covered by highly fractured Krol limestone exhibiting slope ranging between 65°and 77°. The study would be useful to the planners for the land-use planning of the area.

Journal of South American Earth Sciences, Jul 1, 2023

This paper proposes a new mechanism to authenticate and monitor nodes in ad hoc networks (AMORA) ... more This paper proposes a new mechanism to authenticate and monitor nodes in ad hoc networks (AMORA) that carries out access control without the need for a central administration entity. AMORA uses delegation chains to specify in a distributive way which users can access the network and it proposes the use of delegate nodes to issue certificates and to monitor nodes, avoiding malicious nodes from remaining on the network. Besides, AMORA treats efficiently network initialization and partitions. The results of the analysis shows that the mechanism is robust to Sybil and Collusion attacks and that it reduces the monitoring control load in each node in comparison with other mechanisms. Resumo. Este artigo propõe um mecanismo para Autenticação e MOnitoração em Redes Ad hoc (AMORA) para realizar o controle de acesso sem a necessidade de uma entidade administradora centralizada. O AMORA utiliza cadeias de delegação para determinar, de forma distribuída, quais usuários podem acessar a rede e propõe o uso de nós delegados para emitir certificados e para monitorar os nós, impedindo a permanência de nós maliciosos na rede. Além disso, o AMORA trata a inicialização e as partições na rede. Os resultados da análise mostram que o mecanismoé robusto aos ataques conluio e Sybil, além de reduzir a carga de controle em cada nó, quando comparado a outros mecanismos.

EGU General Assembly Conference Abstracts, Apr 1, 2009

Royal Society Open Science, Mar 1, 2021

Soil ecosystem service (SES) approaches evidence the importance of soil for human well-being, con... more Soil ecosystem service (SES) approaches evidence the importance of soil for human well-being, contribute to improving dialogue between science and decision-making and encourage the translation of scientific results into public policies. Herein, through systematic review, we assess the state of the art of SES approaches in tropical regions. Through this review, 41 publications were identified; while most of these studies considered SES, a lack of a consistent framework to define SES was apparent. Most studies measured soil natural capital and processes, while only three studies undertook monetary valuation. Although the number of publications increased (from 1 to 41), between 2001 and 2019, the total number of publications for tropical regions is still small. Countries with the largest number of publications were Brazil (n = 8), Colombia (n = 6) and Mexico (n = 4). This observation emphasizes an important knowledge gap pertaining to SES approaches and their link to tropical regions. With global momentum behind SES approaches, there is an opportunity to integrate SES approaches into policy and practice in tropical regions. The use of SES evaluation tools in tropical regions could transform how land use decisions are informed, mitigating soil degradation and protecting the ecosystems that soil underpins.

<p>The river system plays a very important role in denudation processes and, conseq... 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>

<p>Hillslope hydrology is a major factor controlling the spatial and temporal distr... 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>

<p>Landslides are natural phenomena that cause significant socioeconomic and enviro... 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>

AGU Fall Meeting Abstracts, Dec 1, 2018

AGU Fall Meeting Abstracts, Dec 1, 2012

EGU General Assembly Conference Abstracts, Apr 1, 2013

ABSTRACT Mass movements are recurrent phenomena in the whole Mountain Region of the State of Rio ... 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.

EGU General Assembly Conference Abstracts, Apr 1, 2009

In the northwest part of Rio de Janeiro state water availability is one of the main limiting fact... 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

Revista Sociedade & Natureza, Aug 2, 2010

do mapa de uso e ocupação do solo com o cenário estabelecido no artigo 2º do CFB foi criada uma f... more do mapa de uso e ocupação do solo com o cenário estabelecido no artigo 2º do CFB foi criada uma faixa de entorno. Os resultados indicam que ocorreria conÀ ito entre a utilização do CFB e o uso atual para ás áreas a agricultura e pecuária, solo exposto e área urbana. No caso da agricultura e pecuária, o uso conÀ itante poderia ser amenizado com práticas de manejo e conservação adequadas. A aplicação do CFB contribuiria signi¿ cativamente para aumento das APP (À oresta), promovendo aumento da in¿ ltração de água no solo e recarga do sistema aquífero, diminuição do escoamento super¿ cial e da erosão dos solos. Palavras chave: Bacia hidrográ¿ ca. Código Florestal Brasileiro. Erosão dos solos.

Geomorphology, Sep 1, 2016

Long-term background denudation rates of southern and southeastern Brazilian watersheds estimated... more Long-term background denudation rates of southern and southeastern Brazilian watersheds estimated with cosmogenic 10 Be

Revista Brasileira de Geomorfologia, Dec 19, 2001

RESUMO Deslizamentos são episódios de extrema importância, resultantes da atuação de processos ge... more RESUMO Deslizamentos são episódios de extrema importância, resultantes da atuação de processos geomorfológicos nas mais diversas escalas temporais causando, em geral, enormes prejuízos à sociedade. Dentre os diversos fatores condicionantes destacam-se os parâmetros morfológicos do terreno, os quais controlam diretamente o equilíbrio das forças e, indiretamente, a dinâmica hidrológica dos solos. Embora muitos estudos tenham voltado a atenção para a descrição de eventos e para o monitoramento de campo, pouco ainda se sabe sobre a previsão de ocorrência destes fenômenos. Acredita-se aqui que a combinação de mapeamentos e monitoramentos de campo, através de modelos matemáticos baseados em processos, tenha muito a contribuir nessa direção. Neste sentido, diversos estudos de campo vêm sendo realizados nas bacias dos rios Quitite e Papagaio no sentido de caracterizar o papel desempenhado pelos diversos parâmetros topográficos no condicionamento dos deslizamentos ali ocorridos em 1996. A partir do modelo digital de terreno das bacias, com uma resolução de 4m 2 , combinado com vários mapeamentos ali realizados, foi definido o potencial de deslizamento para as diversas classes de cada atributo topográfico. Paralelamente, foram realizados ensaios de campo com o permeâmetro de Guelph e simulações com o modelo matemático SHALSTAB, voltado para a previsão de áreas instáveis, de modo a englobar os mais diferentes cenários. Os resultados atestam o importante papel desempenhado pelos parâmetros topográficos forma da encosta e área de contribuição, geralmente desprezados pelas metodologias de previsão de áreas susceptíveis a deslizamentos. Palavras chave: deslizamentos, hidrologia das encostas, modelagem matemática, instrumentação dos solos.

Social Science Research Network, 2023

<p>Both internal and external Earth’s dynamics are constantly changin... 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>

Resumo. A mineração não autorizada de criptomoedas implica o uso de valiosos recursos de computaç... more Resumo. A mineração não autorizada de criptomoedas implica o uso de valiosos recursos de computação e o alto consumo de energia. Este trabalho propõe o mecanismo MineCap, um mecanismo dinâmico e em linha para detectar e bloquear fluxos de mineração não autorizada de criptomoedas, usando o aprendizado de máquina e redes definidas por software. O MineCap desenvolve a técnica de super aprendizado incremental, uma variante do super learner aplicada ao aprendizado incremental. O super aprendizado incremental proporciona ao MineCap precisão para classificar os fluxos de mineração ao passo que o mecanismo aprende continuamente com os dados recebidos. Os resultados revelam que o mecanismo alcança 98% de acurácia, 99% de precisão, 97% de sensibilidade e 99,9% de especificidade e evita problemas relacionados ao desvio de conceito. Os resultados desse trabalho foram submetidos e aceitos em um congresso internacional, um congresso nacional, um minicurso, uma revista indexada e, ainda, há um artigo em processo de revisão em uma revista.

Journal of Earth System Science, 2020

Landslide is a normal geomorphic process that becomes hazardous when interfering with any develop... more Landslide is a normal geomorphic process that becomes hazardous when interfering with any development activity. It has been noted that *400 causalities occur in the Himalayan region every year due to this phenomenon. The frequency and magnitude of the landslides increase every year, particularly in the hilly townships. This demands the large scale landslide susceptibility, hazard, risk, and vulnerability assessment of the region to be carried out. In the present study, Mussoorie Township and its surrounding areas located in the Lesser Himalaya has been chosen for Landslide Susceptibility Mapping (LSM) that involved bivariate statistical Yule coefBcient (YC) method. It calculates the binary association between landslides and its various possible causative factors like lithology, land use-landcover (LULC), slope, aspect, curvature, elevation, road-cut, drainage, and lineament. The results indicate that *44% of the study area falls under very high, high and moderate landslide susceptible zones and *56% in the low and very low landslide susceptible zones. The dominant part of the area falling under high and moderate landslide susceptible zones lies in the area covered by highly fractured Krol limestone exhibiting slope ranging between 65°and 77°. The study would be useful to the planners for the land-use planning of the area.

Journal of South American Earth Sciences, Jul 1, 2023

This paper proposes a new mechanism to authenticate and monitor nodes in ad hoc networks (AMORA) ... more This paper proposes a new mechanism to authenticate and monitor nodes in ad hoc networks (AMORA) that carries out access control without the need for a central administration entity. AMORA uses delegation chains to specify in a distributive way which users can access the network and it proposes the use of delegate nodes to issue certificates and to monitor nodes, avoiding malicious nodes from remaining on the network. Besides, AMORA treats efficiently network initialization and partitions. The results of the analysis shows that the mechanism is robust to Sybil and Collusion attacks and that it reduces the monitoring control load in each node in comparison with other mechanisms. Resumo. Este artigo propõe um mecanismo para Autenticação e MOnitoração em Redes Ad hoc (AMORA) para realizar o controle de acesso sem a necessidade de uma entidade administradora centralizada. O AMORA utiliza cadeias de delegação para determinar, de forma distribuída, quais usuários podem acessar a rede e propõe o uso de nós delegados para emitir certificados e para monitorar os nós, impedindo a permanência de nós maliciosos na rede. Além disso, o AMORA trata a inicialização e as partições na rede. Os resultados da análise mostram que o mecanismoé robusto aos ataques conluio e Sybil, além de reduzir a carga de controle em cada nó, quando comparado a outros mecanismos.

EGU General Assembly Conference Abstracts, Apr 1, 2009

Royal Society Open Science, Mar 1, 2021

Soil ecosystem service (SES) approaches evidence the importance of soil for human well-being, con... more Soil ecosystem service (SES) approaches evidence the importance of soil for human well-being, contribute to improving dialogue between science and decision-making and encourage the translation of scientific results into public policies. Herein, through systematic review, we assess the state of the art of SES approaches in tropical regions. Through this review, 41 publications were identified; while most of these studies considered SES, a lack of a consistent framework to define SES was apparent. Most studies measured soil natural capital and processes, while only three studies undertook monetary valuation. Although the number of publications increased (from 1 to 41), between 2001 and 2019, the total number of publications for tropical regions is still small. Countries with the largest number of publications were Brazil (n = 8), Colombia (n = 6) and Mexico (n = 4). This observation emphasizes an important knowledge gap pertaining to SES approaches and their link to tropical regions. With global momentum behind SES approaches, there is an opportunity to integrate SES approaches into policy and practice in tropical regions. The use of SES evaluation tools in tropical regions could transform how land use decisions are informed, mitigating soil degradation and protecting the ecosystems that soil underpins.

<p>The river system plays a very important role in denudation processes and, conseq... 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>

<p>Hillslope hydrology is a major factor controlling the spatial and temporal distr... 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>

<p>Landslides are natural phenomena that cause significant socioeconomic and enviro... 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>

AGU Fall Meeting Abstracts, Dec 1, 2018

AGU Fall Meeting Abstracts, Dec 1, 2012

EGU General Assembly Conference Abstracts, Apr 1, 2013

ABSTRACT Mass movements are recurrent phenomena in the whole Mountain Region of the State of Rio ... 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.

EGU General Assembly Conference Abstracts, Apr 1, 2009

In the northwest part of Rio de Janeiro state water availability is one of the main limiting fact... 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

Revista Sociedade & Natureza, Aug 2, 2010

do mapa de uso e ocupação do solo com o cenário estabelecido no artigo 2º do CFB foi criada uma f... more do mapa de uso e ocupação do solo com o cenário estabelecido no artigo 2º do CFB foi criada uma faixa de entorno. Os resultados indicam que ocorreria conÀ ito entre a utilização do CFB e o uso atual para ás áreas a agricultura e pecuária, solo exposto e área urbana. No caso da agricultura e pecuária, o uso conÀ itante poderia ser amenizado com práticas de manejo e conservação adequadas. A aplicação do CFB contribuiria signi¿ cativamente para aumento das APP (À oresta), promovendo aumento da in¿ ltração de água no solo e recarga do sistema aquífero, diminuição do escoamento super¿ cial e da erosão dos solos. Palavras chave: Bacia hidrográ¿ ca. Código Florestal Brasileiro. Erosão dos solos.

Geomorphology, Sep 1, 2016

Long-term background denudation rates of southern and southeastern Brazilian watersheds estimated... more Long-term background denudation rates of southern and southeastern Brazilian watersheds estimated with cosmogenic 10 Be

Revista Brasileira de Geomorfologia, Dec 19, 2001

RESUMO Deslizamentos são episódios de extrema importância, resultantes da atuação de processos ge... more RESUMO Deslizamentos são episódios de extrema importância, resultantes da atuação de processos geomorfológicos nas mais diversas escalas temporais causando, em geral, enormes prejuízos à sociedade. Dentre os diversos fatores condicionantes destacam-se os parâmetros morfológicos do terreno, os quais controlam diretamente o equilíbrio das forças e, indiretamente, a dinâmica hidrológica dos solos. Embora muitos estudos tenham voltado a atenção para a descrição de eventos e para o monitoramento de campo, pouco ainda se sabe sobre a previsão de ocorrência destes fenômenos. Acredita-se aqui que a combinação de mapeamentos e monitoramentos de campo, através de modelos matemáticos baseados em processos, tenha muito a contribuir nessa direção. Neste sentido, diversos estudos de campo vêm sendo realizados nas bacias dos rios Quitite e Papagaio no sentido de caracterizar o papel desempenhado pelos diversos parâmetros topográficos no condicionamento dos deslizamentos ali ocorridos em 1996. A partir do modelo digital de terreno das bacias, com uma resolução de 4m 2 , combinado com vários mapeamentos ali realizados, foi definido o potencial de deslizamento para as diversas classes de cada atributo topográfico. Paralelamente, foram realizados ensaios de campo com o permeâmetro de Guelph e simulações com o modelo matemático SHALSTAB, voltado para a previsão de áreas instáveis, de modo a englobar os mais diferentes cenários. Os resultados atestam o importante papel desempenhado pelos parâmetros topográficos forma da encosta e área de contribuição, geralmente desprezados pelas metodologias de previsão de áreas susceptíveis a deslizamentos. Palavras chave: deslizamentos, hidrologia das encostas, modelagem matemática, instrumentação dos solos.

Social Science Research Network, 2023

<p>Both internal and external Earth’s dynamics are constantly changin... 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>

Resumo. A mineração não autorizada de criptomoedas implica o uso de valiosos recursos de computaç... more Resumo. A mineração não autorizada de criptomoedas implica o uso de valiosos recursos de computação e o alto consumo de energia. Este trabalho propõe o mecanismo MineCap, um mecanismo dinâmico e em linha para detectar e bloquear fluxos de mineração não autorizada de criptomoedas, usando o aprendizado de máquina e redes definidas por software. O MineCap desenvolve a técnica de super aprendizado incremental, uma variante do super learner aplicada ao aprendizado incremental. O super aprendizado incremental proporciona ao MineCap precisão para classificar os fluxos de mineração ao passo que o mecanismo aprende continuamente com os dados recebidos. Os resultados revelam que o mecanismo alcança 98% de acurácia, 99% de precisão, 97% de sensibilidade e 99,9% de especificidade e evita problemas relacionados ao desvio de conceito. Os resultados desse trabalho foram submetidos e aceitos em um congresso internacional, um congresso nacional, um minicurso, uma revista indexada e, ainda, há um artigo em processo de revisão em uma revista.