Rogerio Uagoda
@pesquisar.unb.br/professor
Associate Professor, Geography departament
University of Brasilia
RESEARCH, TEACHING, or OTHER INTERESTS
Geology, General Agricultural and Biological Sciences
Scopus Publications
Scholar Citations
Scholar h-index
Scholar i10-index
Scopus Publications
Adivane Morais Nogueira, Dandara Caldeira, Rogério Uagoda, Leonardo Chaves Mendes, and Fabiano N. Pupim
Elsevier BV
Maria Rita S. Fonseca, Henrique M. L. Chaves, and Rogério E. S. Uagoda
Wiley
Yawar Hussain, Helena Seivane, Qiangshan Gao, Susanne Maciel, Omar Hamza, Rogério Uagoda, and Welitom Borges
Springer Science and Business Media LLC
Cristiano Fernandes Ferreira, Yawar Hussain, Rogério Uagoda, Tiago Castro Silva, and Rejane Ennes Cicerelli
Walter de Gruyter GmbH
Abstract Dolines are depressions in the soluble ground that indicates the degree of karstification. They may also act as connection points (vulnerability spots) between the surface and underground for the transmission of runoff, sediments, and pollutants. The delineation of these spots (dolines) is a crucial step in environmental management through land use planning to protect the karst underground, which is rich in flora and fauna. This requirement can benefit from a cost-effective, accessible, and non-invasion high-resolution investigation generating digital elevation models (DEMs) from unmanned aerial vehicle (UAV) imagery and automated object detection techniques. This study examines the capabilities of UAV-based DEM in detecting dolines across 50 km2 in the environmentally protected area of river Vermelho (APANRV – Área de Proteção Ambiental das Nascentes do Rio Vermelho). Initially, an automatic objects (doline and no-doline) detection algorithm was applied to the DEM, followed by a visual inspection to differentiate doline from possible dolines in orthomosaic photos, topographic profiles, and shaded UAV-based relief (digital terrain model; DTM and DSM). For the redundancy checking, a cluster analysis with four tests was conducted. The objects generated from the best clusters and morphological analysis were gathered in the same base for visual inspection. Out of a total of 933 objects identified, 41% were obtained from the DSM base, 25% from the perimeter-to-area ratio, and 34% through convergence between the two-analyses. Subsequently, the resulting doline typologies are discussed in reference to their proximity to hydrogeological features and their impacts on underground vulnerability. The findings aligned with the previous research as dolines were highly concentrated near sites where carbonates come in contact with siliciclastic sediments.
Cristiano Fernandes Ferreira, Yawar Hussain, and Rogério Uagoda
The Research Center of the Slovenian Academy of Sciences and Arts (ZRC SAZU)
Doline mapping is paramount in the vulnerability and risk assessment of the underground karst environment by identifying cave-ground connectivity points at the surface. However, manual mapping is labour-intensive, slow and subjective, especially on a large scale. Therefore, the present study adopted a GIS-based semi-automatic approach for mapping large and medium-sized depressions/dolines in the Corrente river basin in Brazil, with a particular focus on the environmentally preserved areas of river Vermelho (APANRV Portuguese abbreviation) using remote sensing (DEM and Google Earth imagery) and field-based observations. Seven typical dolines forms (e.g., cockpit with drain insertion, collapse, collapse with river capture, suffosion, solution, cover collapse, and buried) are found from extensive field surveys. As an outcome of the proposed approach, two hundred and thirty-two medium to large-sized dolines have been identified and categorised into three main groups based on the cave density and local geology G1, G2, and G3. The high density of identified dolines (164 known caves) in G1 provides reconnaissance for future speleological works in the preserved areas. Additionally, the presence of a considerable number of dolines in the adjoining areas (G2 and G3) stresses the need to revise the existing boundaries of the APANRV. Results correlate well with the dolines sites marked using field surveys and Google Earth images. This doline mapping may help researchers in the groundwater vulnerability assessment and the protection of speleological heritage preserved in the caves.
Renan Smith Penido Louzada, André Silva Tavares, and Rogério Uagoda
Revista Brasileira de Geomorfologia
A carga sedimentar fluvial pode indicar alterações na dinâmica ambiental em bacias hidrográficas, como processos intensificados de erosão, assoreamentos e diminuição de oxigênio disponível em rios e lagos, entre outros fatores. O objetivo desse estudo foi monitorar a vazão e a carga sólida em suspensão durante eventos pluviais de diferentes magnitudes próximo à foz do Ribeirão do Gama, em Brasília, Distrito Federal, e avaliar qual o nível de contribuição da produção de sedimentos ao lago Paranoá, entre dezembro de 2015 e março de 2016. Para isso, a vazão foi estimada por meio de medições discretas a vau com auxílio de molinete e método acústico. O nível foi obtido com linígrafo digital, permitindo estabelecer uma curva-chave a partir da equação exponencial. Amostradores manuais integradores e amostrador automático pontual foram utilizados para obter dados de descarga sólida. O tempo de concentração pluvial foi calculado para onze eventos monitorados, e testadas as correlações entre chuva, vazão, carga sólida e turbidez. Os resultados indicaram histereses com dois comportamentos: laço em oito e laço no sentido anti-horário. É possível inferir que a à produção de sedimentos na bacia do Ribeirão do Gama possui uma resposta direta relacionada ao escoamento superficial e infiltração de água no solo.
Ana Camila da Silva, Isabela Resende, Rodrigo Cintra da Costa, Rogério Elias Soares Uagoda, and André de Souza Avelar
Elsevier BV
Yawar Hussain, José Eloi Guimarães Campos, Welitom Rodrigues Borges, Rogério Elias Soares Uagoda, Omar Hamza, and Hans-Balder Havenith
MDPI AG
The present study applies a geophysical approach to the Federal district of Brazil, a challenging hydrogeologic setting that requires improved investigation to enhance groundwater prospecting to meet the rising water demand. The geophysical characterization of a complex hard-rock aquifer sub-system was conducted using direct current (DC) electrical resistivity tomography (ERT) integrated with surface geological information. With a total of twenty-seven ERT profiles, the resistivity acquisition was carried out using a dipole-dipole array of electrodes with an inter-electrode spacing of 10 m. Based on resistivity ranges, the interpretation of the inverted resistivity values indicated a ground profile consisting of upper dry soil, saprolite, weathered, and fresh bedrock. Along with this layered subsurface stratigraphy, the approach allowed us to map the presence of significant hydrogeological features sharp contrasting anomalies that may suggest structural controls separating high-resistivity (≥7000 Ω m) and low-resistivity (<7000 Ω m) conducting zones in the uppermost 10 m of the ground. The assumed impacts of these features on groundwater development are discussed in light of the Brasilia aquifer settings.
Maria Rita Souza Fonseca, Rogério Uagoda, and Henrique Marinho Leite Chaves
Wiley
Due to the high rainfall erosivity and highly erodible soils, water erosion is severe in Brazil. Soil and ecosystem degradation occurs when erosion exceeds on‐ and off‐site soil loss tolerances, with significant socioeconomic and environmental impacts. In the last 50 years, the Brazilian Cerrado had 53% of its original vegetation converted to agriculture and pastureland. Although erosion plot studies exist in the region, the data are fragmented and unexplored, hindering the development of soil conservation policies. The objective of the present research was to compile, systematize, and statistically analyze the existing erosion plot data in the Brazilian Cerrado, correlating the observed results with different environmental and management factors, and with the corresponding soil loss tolerances. Twenty runoff plot datasets of the Brazilian Cerrado, encompassing 5 states, 10 sites, 108 plots, and 360 plot·years were compiled and thoroughly analyzed. Mean annual rainfall, runoff, and soil loss were 1443.5 mm year−1, 83.1 mm year−1, and 8.9 Mg ha−1 year−1, respectively. After the data were normalized with respect to plot length, steepness, and climate, runoff and soil loss were found to be significantly higher in soils with impermeable horizons and in land uses without permanent soil cover (p < 0.05). Erosion under permanently covered plots was below the on‐ and off‐site soil loss tolerances. A power equation provided the best fit between plot runoff and soil loss (R2 = 0.71; p < 0.05), indicating that runoff volume, easier to estimate, could be used as a proxy for upslope erosion. Although erosion plot data cannot be extrapolated to the whole landscape, the research results provide useful elements for the development of sound conservation policies in the Cerrado and in other similar savannas of the world.
Olavo Amancio Oliveria, Drielly Souza Rodrigues, José Eloi Guimarães Campos, and Rogério Uagoda
Revista Brasileira de Geografia Fisica
O mapeamento da superfície potenciométrica em aquíferos cársticos e físsuro-cársticos, em muitos casos, pode ser complexo em função da anisotropia e heterogeneidade destes sistemas, que comumente ocorrem de forma compartimentada. O presente trabalho apresenta um método para a confecção de mapas de isopiezas em aquíferos hospedados em rochas carbonáticas, incluindo os seguintes passos: i) caracterização do modelo conceitual do aquífero e enquadramento das condições de contorno; ii) extração dos lineamentos estruturais regionais e locais; iii) avaliação dos dados potenciométricos pontuais e verificação de contrastes em poços situados em diferentes compartimentos; iv) interpolação dos dados de poços separadamente em cada compartimento e v) união dos diferentes blocos para recomposição da área original. O método foi testado em uma área de aquífero cárstico situada no alto curso da bacia do Rio Corrente na região nordeste do estado de Goiás. O produto final mostra diferentes comportamentos do fluxo hídrico subterrâneo quando se considera o mapa confeccionado como um sistema único e o mapa potenciométrico resultante da união dos diferentes blocos. Como resultado final da proposta, é possível afirmar que a confecção dos mapas a partir da separação dos blocos pode resultar em um produto mais coerente com a realidade e com maiores possibilidades de aplicação para os diferentes fins (estudo de divisores de bacias hidrogeológicas, comportamento de plumas de contaminação, direções regionais de fluxo etc.).Palavras-chave: fluxo subterrâneo, carga hidráulica, interpolação. Methodology for Drawing Potentiometric Maps in Karstic and Fissure-Karstic Aquifers: Case Study in the Upper Current River Basin, Mambaí, GO ABSTRACTThe mapping of the potentiometric surface in karstic and fissure-karstic aquifers, in many cases, can be complex due to the anisotropy and heterogeneity of these systems, which commonly occur compartmentally. The present work presents a method for the preparation of potenciometric maps in aquifers hosted in carbonate rocks, including the following steps: i) characterization of the conceptual model of the aquifer and framing of the boundary conditions; (ii) extraction of regional and local structural lineaments; iii) evaluation of single point potentiometric data and verification of contrasts in wells located in different compartments; iv) interpolation of the well data separately in each compartment and v) union of the different blocks for composition of the original area. The method was tested in an area of karstic aquifer located in the high course of the Corrente River watershed in the northeastern region of Goiás State, Central Brazil. The final product shows different behaviors of the groundwater flow when considering the map made as a single system and the potentiometric map resulting from the union of the different blocks. As a final result of the proposal, it is possible to affirm that the mapping from the separation of blocks can result in a product more coherent with reality and with greater possibilities of application for the different purposes (study of hydrogeological basin dividers, behavior of contamination plumes, regional flow directions, etc.).Keywords: groundwater flow, hydraulic head, interpolation.
Dandara Caldeira, Rogério Uagoda, Adivane Morais Nogueira, Jeremie Garnier, André Oliveira Sawakuchi, and Yawar Hussain
Quaternary International Elsevier BV
Yawar Hussain, Welitom Borges, Rogerio Uagoda, Cristiane Moura, Susanne Maciel, Omar Hamza, and Hans-Balder Havenith
Walter de Gruyter GmbH
Abstract In the Federal District of Brazil, groundwater extraction is challenged by fractured aquifers with difficulty in identification of hydraulic traps and significant uncertainty in the estimation of recharge potential. This study aims to optimize the demarcation of new locations of tubular wells by the aid of geophysical investigation. In the first stage of this study, the total exploitable amount of groundwater were calculated from the information of the physical environment and the existing wells. Second, electrical resistivity tomography (ERT) method was carried out on the selected sites – based on their surficial characteristics. The possible hydraulic traps (where groundwater might exist) were identified from the inversion of the resistivity measured by the dipole–dipole array and from the delineation of the resultant conducting zones (including the weathered rocks and fractures). Using this approach, we predicted the position and number of tubular wells required and ranked them according to their potential productivity. The study provides a promising framework for investigating groundwater in fractured aquifers.
Saeed YOUSEFZADEH, Mohsen JANMOHAMMADI, and Naser SABAGHNIA
Journal Agriculture and Forestry
Yawar Hussain, Rogerio Uagoda, Welitom Borges, Renato Prado, Omar Hamza, Martín Cárdenas-Soto, Hans-Balder Havenith, and Jie Dou
Water (Switzerland) MDPI AG
Reliable characterization of the karst system is essential for risk assessment where many associated hazards (e.g., cover-collapse dolines and groundwater pollution) can affect natural and built environments, threatening public safety. The use of multiple geophysical approaches may offer an improved way to investigate such cover-collapse sinkholes and aid in geohazard risk assessments. In this paper, covered karst, which has two types of shallow caves (vadose and fluvial) located in Tarimba (Goias, Brazil), was investigated using various geophysical methods to evaluate their efficiency in the delineation of the geometry of sediments filled sinkhole. The methods used for the investigation were Electrical Resistivity Tomography (ERT), Seismic Refraction Survey (SRS), Seismic Refraction Tomography (SRT) and the Very Low Frequency Electromagnetic (VLF-EM) method. The study developed several (2D) sections of the measured physical properties, including P-wave velocity and electrical resistivity, as well as the induced current (because of local bodies). For the analysis and processing of the data obtained from these methods, the following approaches were adopted: ERT inversion using a least-square scheme, Karous-Hjelt filter for VLF-EM data and time-distance curves and Vp cross-sections for the SRS. The refraction data analysis showed three-layered stratigraphy topsoil, claystone and carbonate bedrock, respectively. The findings obtained from ERT (three-layered stratigraphy and sediment-filled doline), as well as VLF-EM (fractured or filled caves as a positive anomaly), were found to be consistent with the actual field conditions. However, the SRS and SRT methods did not show the collapsed material and reached the limited the depth because of shorter profile lengths. The study provides a reasonable basis for the development of an integrated geophysical approach for site characterization of karst systems, particularly the perched tank and collapse doline.
Cristiano Fernandes Ferreira and Rogério Elias Soares Uagoda
Revista Brasileira de Geomorfologia
As dolinas são feições indicadoras do sistema cárstico e além de atestarem processos evolutivos, também apresentam importância no contexto das dinâmicas hídricas e ambientais. O mapeamento dessas feições serve como base para diversas análises da paisagem e exige grande dispêndio de tempo e recursos, com significativa subjetividade inerente à técnica de aquisição ou à problemas de escala. A melhoria da resolução espacial nas bases de dados permitiu maior precisão nos mapeamentos de dolinas com o uso de modelos digitais de elevação e técnicas de geoprocessamento, automatizadas ou manuais. Entretanto, as dificuldades de detecção dos pontos de absorção que individualizam as dolinas, e os limites estabelecidos para seu perímetro dificultam a comparação entre estudos, agregando incertezas nos atributos espaciais como área, profundidade e eixo principal. Neste artigo são discutidas as principais metodologias de mapeamento de dolinas e sintetizadas as estratégias mais utilizadas para superar erros de omissão de feições verdadeiras, problemas com a detecção de falsos positivos e a delimitação mais precisa das depressões cársticas.
Yawar Hussain, Rogerio Uagoda, Welitom Borges, José Nunes, Omar Hamza, Cristobal Condori, Khurram Aslam, Jie Dou, and Martín Cárdenas-Soto
MDPI AG
The use of geophysical characterization of karst systems can provide an economical and non-invasive alternative for extracting information about cavities, sinkholes, pathways for water infiltration as well as the degree of karstification of underlying carbonate rocks. In the present study, three geophysical techniques, namely, Ground Penetrating Radar (GPR), Electrical Resistivity Tomography (ERT) and Very Low Frequency Electromagnetic (VLFEM) methods were applied at three different locations in relation to fluvial karst, which is listed as an environmentally sensitive area in Rio Vermelho, Mambaí, Goiás, Brazil. In the data acquisition phase, the GPR, direct-current (DC) resistivity and VLFEM profiles were obtained at the three locations in the area. Data were analyzed using commonly adopted processing workflows. The GPR results showed a well-defined lithology of the site based on the amplitude of the signal and radar typologies. On the other hand, the inverted resistivity cross-sections showed a three-layered stratigraphy, pathways of water infiltration and the weathered structures in carbonate (Bambui group). The interpretation of VLFEM as contours of current density resulted from Fraser and Karous–Hjelt filters, indicated the presence of conductive structures (high apparent current density) that might be linked to the weathered carbonate and other conductive and resistive anomalies associated with the water-filled and dry cavities (cave), respectively. The results encourage the integrated application of geophysical techniques such as the reconnaissance for further detailed characterization of the karst areas.
Yawar Hussain, Omar Hamza, Xinghui Huang, André Carlos Silva, Cristobal Condori, Rogério Uagoda, and André Luís Brasil Cavalcante
FapUNIFESP (SciELO)
Mudflow is often associated with seismic activities. The present study applied a seismic based detection of the surface waves generated by the mudflow of Brumadinho dam collapse using records of Brazilian Seismographic Network. The signal envelope and time-frequency spectrograms of the mudflow signals were used in the analysis. As a result, the mudflow signals were successfully detected from the data recorded at a nearby seismic station. The findings of this study provide a good basis for future research to develop a flood early warning system based on cost-effective, remote and contentious seismic monitoring approaches.
José Gustavo Da Silva Nunes and Rogério Uagoda
Revista Brasileira de Geografia Fisica
Este trabalho teve como objetivo reunir informações sobre comportamento pedogenético e hidrológico em áreas de rochas carbonáticas de clima tropical. A execução desta pesquisa foi embasada em artigos científicos indexados, nacionais e internacionais, como também em livros, teses e dissertações relevantes para o tema proposto. O solo é um sistema multifásico, e os seus aspectos morfológicos e constitucionais atuam facilitando ou dificultando a permeabilidade da água, assim cada horizonte pedológico funciona como um mecanismo em um mesmo perfil de solo. Os fatores físicos/químicos da água também atuarão contribuindo para a classificação dos grupos hidrológicos de solo. No Brasil, a Embrapa realizou classificações dos horizontes diagnósticos, dos grupos hidrológicos e dos tipos de solos, baseada em autores internacionais, adaptadas às condições tropicais. Mas as áreas cársticas, que representam um percentual de 20% da superfície terrestre, podem apresentar condições particulares para a formação de solo e para o comportamento hidrológico, podendo incluir zonas locais de alta permeabilidade, fuga de água subterrânea e eliminação de resíduos insatisfatórios. Solos de ambientes cársticos são mal desenvolvidos, apresentam argilas avermelhadas de baixa atividade normalmente. No Brasil os estudos deste tipo de ambiente são escassos, mas alguns trabalhos desenvolvidos em áreas cársticas trazem algumas informações básicas sobre os solos. As pesquisas encontradas que trouxeram informações dos solos em carstes, foram plotadas no mapa brasileiro. A pesquisa demonstrou que há um gap de informações para o desenvolvimento pedológico em áreas cársticas, mas é possível fazer associações entre estas classes de solo a outros ambientes, incluindo o comportamento hidrológico.Soils In Tropical Karst, Pedogenetic Development And Hydrological Behavior: A Theoretical Review A B S T R A C TThis work aimed to gather information on pedogenetic and hydrological behavior in carbonate rock areas of tropical climate. The execution of this research was based on indexed scientific articles, national and international, as well as on books, theses and dissertations relevant to the proposed theme. The soil is a multiphase system, and its morphological and constitutional aspects act to facilitate or hinder water permeability, so each pedological horizon works as a mechanism in the same soil profile. The physical / chemical factors of the water will also act contributing to the classification of soil hydrological groups. In Brazil, Embrapa carried out classifications of diagnostic horizons, hydrological groups and soil types, based on international authors, adapted to tropical conditions. However, karst areas, which represent a percentage of 20% of the earth's surface, may present particular conditions for soil formation and hydrological behavior, and may include local areas of high permeability, groundwater leakage and unsatisfactory waste disposal. Soils in karst environments are poorly developed, with reddish clays of low activity normally. In Brazil, studies of this type of environment are scarce, but some studies carried out in karst areas bring some basic information about the soils. The researchers found that brought information on soils in carstes, were plotted on the Brazilian map. Research has shown that there is an information gap for pedological development in karst areas, but it is possible to make associations between these soil classes and other environments, including hydrological behavior.Keywords: Soil Hydrological Groups; Tropical Soil; Karst.
José Gustavo Da Silva Nunes and Rogério Uagoda
Revista Brasileira de Geografia Fisica
Este artigo se trata de uma revisão metodológica de técnicas indiretas de mapeamento pedológico, envolvendo ensaios granulométricos, SIG e sensoriamento remoto dentro do mapeamento digital de solos, espectrorradiometria e Georadar (GPR), comparados e/ou associados às técnicas diretas como coleta, descrição de trincheiras ou perfis, análise da paisagem. O mapeamento digital de solos (MDS) vem se provando com uma ferramenta eficiente desde o início do ano 2000, associadas a outros métodos como o sensoriamento remoto e análises laboratoriais, o MDS forneceu ao mundo mapas que representam bem a realidade dos solos. Mas as técnicas diretas ainda são usuais e eficientes, e podem ser associadas aos métodos indiretos, para que o mapeamento de uma pequena área possa ser espalhado regionalmente. A busca por técnicas de baixo custo, eficiência e praticidade tem levado pesquisadores a buscarem técnicas como o Georradar para verificar a profundidade do solo, sem que seja necessário a destruição de perfis por meio da abertura de trincheiras, como também ao uso de imagens de radar capaz de oferecer um produto de alta resolução espacial, independentemente da altitude da plataforma, e que tem auxiliado na extração de diversas informações da paisagem diretamente ligadas à pedogênese. Esta pesquisa tem o intuito de buscar a evolução do mapeamento pedológico através das diversas técnicas citadas, e bem como a associação entre os diversos métodos para gerar um mapa de solos de alta precisão. Efficiency analysis of indirect methods for soil mapping against direct techniques, and their possible associations: A methodological reviewA B S T R A C TThis article is a methodological review of indirect techniques of pedological mapping, GIS and remote sensing within digital soil mapping, spectroradiometry and Georadar (GPR), compared to landscape analysis. Research has shown that digital soil mapping (MDS) has been an efficient tool since the beginning of the year 2000, combined with other methods such as remote sensing and laboratory analysis, MDS has provided the world with maps that represent the reality of soils well. But direct techniques are still common and efficient, and can be associated with indirect methods, so that local mapping information can be dispersed regionally. The search for low-cost, efficient and practical techniques has led researchers to look for techniques such as Georadar to check the depth of the soil, without the need to destroy profiles by opening trenches, as well as using radar images. which provide a high spatial resolution product, regardless of the platform's altitude, and which has helped in the extraction of various landscape information directly linked to pedogenesis. Spectroradiometry is a methodology that works with the measurement of radiant electromagnetic energy, and allows for quick associations between targets and spectral curves, allowing the creation of global libraries of these curves. Radiometry in turn has been widely used in systems that operate in the microwave frequency range, ranging from 1mm to 1m in length, and allow you to locate objects. This research aims to seek the evolution of pedological mapping through the various techniques mentioned, as well as the association between the various methods to generate a highly accurate soil map.Keywords: Soil Mapping; GPR; Spectroradiometry; Orbital Sensors
Cristiano Fernandes Ferreira and Rogério Elias Soares Uagoda
Revista Brasileira de Geografia Fisica
O carste se desenvolve sobretudo pela ação da dissolução em subsuperfície, na interação da água com rochas solúveis, especialmente as carbonáticas. Apesar do processo de carstificação nem sempre se apresentar em superfície, a ocorrência de dolinas, feições consideradas características, indica maior proeminência desse fenômeno. Muitos trabalhos internacionais se dedicaram ao mapeamento de dolinas com objetivos diversos, como comparar o nível de carstificação e evolução dos ambientes onde estão inseridas, relacionar o desenvolvimento destas feições com estruturas geológicas ou realizar análises hidrológicas de caráter ambiental. Por outro lado, são poucos os trabalhos com esta temática realizados no Brasil, parte concentrada em regiões cársticas tradicionais, como o Vale do Ribeira-SP, Chapada Diamantina-BA e nos carbonatos de Minas Gerais, e os demais dispersos pelo país, muitos em rochas não carbonáticas. Neste sentido o objetivo deste artigo é realizar uma revisão dos trabalhos sobre mapeamento de dolinas, com enfoque nos aspectos morfométricos e quantificação, visando especialmente elaborar um primeiro panorama sobre como o tema é abordado no Brasil. Observou-se que a maior parte dos estudos nacionais alcançou resultados de frequência (nº/km²) bastante inferiores aos identificados em estudos internacionais. Essa discrepância foi atribuída a alguns aspectos, como a adoção de fontes de dados inadequadas em escala abrangente, a escolha de áreas muito extensas para a análise ou de fato a investigação em áreas pouco propícias a ocorrência de dolinas. An Overview of Doline Mappings in Brazil, Karst's Elemental Features A B S T R A C TKarst develops mainly by the action of dissolution in subsurface, in the interaction of water with soluble rocks, especially carbonates. Although the karsification process does not always appear on the surface, the occurrence of dolines, features considered characteristic, indicates a greater prominence of this phenomenon. Many international works have been devoted to the mapping of dolines with different objectives, such as comparing the level of karsification and evolution of the environments in which they are inserted, to relate the development of these features to geological structures or to perform environmental hydrological analyzes. On the other hand, there are few studies on this subject in Brazil, concentrated part in traditional karst regions such as Vale do Ribeira-SP, Chapada Diamantina-BA and carbonates of Minas Gerais, and the others scattered around the country, many in non-carbonate rocks. In this respect, the objective of this article is to review the work on doline mapping, with a focus on morphometric aspects and quantification, aiming in particular to elaborate a first overview about how the theme is approached in Brazil. It was observed that most of the national studies reached frequency results (n°/km²) much lower than those identified in international studies. This discrepancy was attributed to some aspects, such as the adoption of inadequate data sources in a wide scale, the choice of very extensive areas for analysis or indeed the investigation in areas less favorable to the occurrence of dolines.Keywords: karst; doline; density.
Yawar Hussain, Martin Cardenas-Soto, Salvatore Martino, Cesar Moreira, Welitom Borges, Omar Hamza, Renato Prado, Rogerio Uagoda, Juan Rodríguez-Rebolledo, Rafeal Silva,et al.
MDPI AG
Geophysical methods have a varying degree of potential for detailed characterization of landslides and their dynamics. In this study, the application of four well-established seismic-based geophysical techniques, namely Ambient Noise Interferometry (ANI), Horizontal to Vertical Spectral Ratio (HVSR), Multi-Channel Analysis of Surface Waves (MASW) and Nanoseismic Monitoring (NM), were considered to examine their suitability for landslide characterization and monitoring the effect of seasonal variation on slope mass. Furthermore, other methods such as Ground Penetrating Radar (GPR) and DC Resistivity through Electrical Resistivity Tomography (ERT) were also used for comparison purpose. The advantages and limitations of these multiple techniques were exemplified by a case study conducted on Sobradinho landslide in Brazil. The study revealed that the geophysical characterization of the landslide using traditional techniques (i.e., GPR, ERT and MASW) were successful in (i) the differentiation between landslide debris and other Quaternary deposits, and (ii) the delineation of the landslide sliding surface. However, the innovative seismic based techniques, particularly ambient noise based (HVSR and ANI) and emitted seismic based (NM), were not very effective for the dynamic monitoring of landslide, which might be attributed to the short-time duration of the data acquisition campaigns. The HVSR was also unsuccessful in landslide site characterization i.e., identification of geometry and sliding surface. In particular, there was no clear evidence of the light seasonal variations, which could have been potentially detected from the physical parameters during the (short-time) ambient noise and microseismic acquisition campaigns. Nevertheless, the experienced integration of these geophysical techniques may provide a promising tool for future applications.
Yawar Hussain, Sehar M. Hussain, Salvatore Martino, Martin Cardenas-Soto, Omar Hamza, Juan F. Rodriguez-Rebolledo, Rogério Uagoda, and Hernan Martinez-Carvajal
FapUNIFESP (SciELO)
Reactivation of a landslide is usually accompanied by microseismic signals emitted from the deforming soil mass. The reproduction of similar signals in a physical model test conducted under control conditions can allow researchers to explore and test such complicated signals to improve the prediction of full-scale failure. The present study investigates the similarity between the slidequakes (microseismicity) naturally emitted from an existing colluvial landslide (Sobradinho, Brazil) in response to rainfalls and the emissions generated by a pullout test of an expander body (EB) pile in tropical soil under controlled conditions. The microseismic signals emitted from both experimental sites (i.e. the landslide and the EB pile test) were recorded and compared. Data were acquired by mini-arrays of four short-period seismometers. For the signal nomenclature, a typological scheme was adopted, in which sonograms/spectral contents of the signals were used. As a result, short duration microseismic signals were observed during the pullout test. In contrast, at the Sobradinho landslide, the testing detected signals of different characteristics whose source mechanisms have remained ambiguous, mainly because of the short duration of the data campaigns. However, at the landslide, propagating events were observed that might be attributed to the energies generated by the river bedload during the heavy rains. The present study offers some insight into the pre-collapse dynamic behavior of unstable slopes in clayey formations.
Y. HUSSAIN, M. CARDENAS-SOTO, R. UAGODA, S. MARTINO, N. P. SANCHEZ, C. A. MOREIRA, and H. MARTINEZ-CARVAJAL
Instituto de Geociencias - UFRJ
Brazilian landslides are characterized as shallow, clay rich and are commonly triggered by the summer rainfalls. Therefore, the landslide geological information, such as shear surface location, has a paramount importance in their mechanism comprehension. The most adapted methods for the estimation of shear wave velocity profile are borehole stratigraphic logs or Standard Penetration Test (SPT) and Cone Penetration Test (CPT). However, the present study applied shear wave velocity estimation of Sobradinho landslide (SLS) by a joint inversion of horizontal to vertical spectral ratio (HVSR) curve and dispersion curve (DC) extracted from frequency-wavenumber (f-k) analysis of ambient noise records. HVSR curves at all the stations in the area exhibit the ubiquitous resonance frequency peak at 2 Hz indicates that at these stations the substratum is common. The f-k results for E-W component let us obtain an acceptable DC between 5 and 7 Hz range. Finally, joint inversion was interpreted based on the diffuse field assumption. The initial model was proposed to be a three-layered over a half-space. Results of joint inversion indicate that the substratum is at 24 m depth, with Vs values close to 1500 m/s. DC defines two layers overlaying the substratum: superficial layer with velocities near to 200 m/s (7m thick), and the second layer with Vs value of 1000 m/s. We think that abrupt rheology (stiffness) change between the first and the second layer could provide an evidence of the landslide re-activation during moderate to strong rainfall events. The proposed methodology will prove a reconnaissance survey for the detailed geotechnical investigations that will confirm the obtained results.
José Gustavo da Silva Nunes, Rogério Uagoda, Dandara Caldeira, Ligier Modesto Braga, Yawar Hussain, and Hernán Martinez Carvajal
Revista Brasileira de Geomorfologia
O presente estudo tem por objetivo fazer uso de tecnologia GPR (Ground Penetration Radar), também conhecido como Georadar, para distinguir os materiais aluvionares, coluvionares e eluvionares depositados nas encostas e planícies da fazenda Vão do Buraco, calha do Contagem, porção leste do Planalto Central, na região do Distrito Federal. Foram definidas três encostas: côncava fechada (E1), côncava aberta (E2) e convexa (E3), para a aquisição de dados dos perfis de GPR, onde já se tinham descrições prévias dos materiais depositados, apresentando elúvio no topo, colúvio na média encosta e colúvio/aluvião na planície com formação de um leque aluvial. Fez-se uso de uma antena de 400 MHz para a sondagem, resultando em radargramas com informações de refletância. Devido às diferenças de composição entre o aluvião e o coluvião, seus contatos são abruptos. O alúvio, por apresentar cascalhos em sua composição, é definido por um número maior de alvos e alta refletância. Já o colúvio é constituído por materiais de granulometria mais fina (silte e argila), apresentando baixa refletância com alvos difusos.
Yawar Hussain, Martin Cardenas-Soto, Rogerio Uagoda, Salvatore Martino, Juan Rodriguez-Rebolledo, Omar Hamza, and Hernan Martinez-Carvajal
FapUNIFESP (SciELO)
The application of geophysical monitoring technologies may offer an opportunity to understand the dynamic of slopes in response to factors triggering their instability. In this study, Ambient Noise Interferometry was used as a monitoring approach on a man-made reduced-scale vertical slope and on a natural-scale landslide in Sobradinho (Brazil), under the influence of mechanical stress and rainfall, respectively. For both experiments, we adopted similar data acquisition system and processing workflow. After preprocessing of ambient seismic noise, the time-lapse changes were determined in terms of relative velocity changes using the moving window cross spectral technique. For the vertical slope, terrestrial laser scanning was also performed to detect crack or fissure generation. The prototype experiment results showed a decreasing trend of relative velocity changes and reached a minimum value of -0.6% at the end of the experiment. No change was detected on the digital elevation model that was computed from terrestrial laser scanning images, due to the absence of centimeter scale superficial fissures. At natural scale (Sobradinho landslide), no significant variation in relative velocity changes was detected for the rainy and non-rainy days, mainly because of the inadequate change in the degree of saturation, which was found within a relatively short period of data acquisition.