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This paper presents the relationship between environmental and anthropic factors, long-term dunefield migration, as well as sediment budget and overpassing process at Santinhos-Ingleses dunefield, in Southern Brazil. The study is based on two-decade (2002–2023) topographic data, meteorological and satellite images (for vegetation, urbanization and dune migration assessment). An analysis of historical rainfall data reveals a consistent rise in annual average precipitation, the events often correlated with north winds, which had lower average speeds compared to the stronger south winds. This, as the primary force driving the northward migration of the dunefield, has decreased, and the drift potential diminished. During rainy days, aeolian transport is limited as the sand becomes moistened, facilitating vegetation growth (approximately 10% between 2014 and 2023). The PDO average index (2002–2023) highlighting two distinct patterns: positive periods accounting for 18% and negative periods for 82%. These patterns have significant implications for sediment volume and rainfall variability in the region. Urban expansion, estimated at around 12% during this interval, emerges as a significant factor in the system. The northern part of Santinho's embayment features a flatter, wider, and more stable compared to the southern part. The higher energy levels in the surf zone facilitate aeolian sediment transport to the beach, which is crucial for the initiation of the transgressive dunefield. Additionally, the lower topography behind the foredune, contrasting with the higher elevation further inland, increases sediment accumulation and transport. The topography data shows consistent sediment input values over the last decade (2014–2023), ranging from 6000 to 7000 m³/year. In contrast, sediment supply values during the same period average around 8000 m³/year. Consequently, the sediment overpassing Santinho's foredune towards Ingleses beach results in a negative sediment balance in the dunefield system. • Topography decadal data collected with DGPS. • Relationship between environmental and anthropic factors with dunefield migration. • Sediment budget and overpassing at Santinho and Ingleses beach, southern of Brazil. • Negative sediment balance in the dunefield system. [ABSTRACT FROM AUTHOR]

The near-field glacial record of the late Paleozoic Ice Age in Gondwanan basins is widely used in global paleogeographic and paleoclimatic models. Nevertheless, several late Paleozoic glacial successions still lack a detailed depositional history or reassessment of their genesis under modern glacial sedimentology concepts. One such example is the Aquidauana Formation in the western Paraná Basin, Brazil, which corresponds to about 65 % of the total outcrop area of the late Paleozoic glacial strata (Itararé Group) within the basin. Yet, the stratigraphic architecture and depositional environments are full of uncertainties as the strata are very poorly exposed. This study brings new insights on the depositional history and stratigraphic architecture for the upper half of the Aquidauana Formation by describing a 290-m-thick section cropping out along a recently developed highway in the Mato Grosso do Sul state. A subaqueous slope and glaciated outer shelf depositional setting is interpreted for the upper half of the Aquidauana Formation, which differs considerably from the glacioterrestrial and postglacial arid context traditionally proposed. More specifically, deposition chiefly took place under ice-free conditions on a subaqueous slope within an erosionally-confined channel–levee complex through sediment density flows and subaqueous landslides. Episodic glacial influence on sedimentation is recorded within the uppermost portion of the section by glacially-modified and iceberg-rafted debris as well as a deglacial trace fossil assemblage within proglacial deposits. Sediment transport toward the southeast into the basin indicates a glacial source placed westward of the Paraná Basin, reinforcing the hypothesis of ice-spreading centers located westward of the basin. The outcomes of this study also emphasize the relevance of subaqueous gravity-driven resedimentation in emplacing the late Paleozoic glacial record. [ABSTRACT FROM AUTHOR]

An approach involving data on wave-induced sediment transport estimates is essential for managing coastal environments. Numerical models are powerful tools to understand and investigate many processes responsible for longshore sediment transport (LST) in a systematic way, since direct measurement of LST is a difficult task. This paper presents estimates of longshore sediment transport through numerical modeling of wave-induced sediment dispersion patterns in the Formosa Bay, State of Rio de Janeiro - Southeast Brazil. The analysis was conducted using the computational package Coastal Modeling System/SMC-Brazil and mathematical formulations proposed by Cerc (1984). The results suggest average residual solid discharge (Qsr avg) in the order of 131,442.745 m3/yr in northern sector, −151,908.32 m3/yr in central sector, and 71,987.69 m3/yr in southern sector of investigated area. In addition, it is important to highlight that minor variations in the wave incidence angle may cause changes in the longshore sediment drift, promoting the convergence and divergence zones throughout the investigated area. The results presented contribute to the advancement of knowledge on the topic addressed here and will be useful in future engineering projects related to beach nourishment and the management of coastal areas subject to erosion processes. • Data are presented on simulations of wave-induced longshore sediment transport rates in Baia Formosa Bay, southeastern Brazil. • The Coastal Modeling System SMC/Brazil were used. • Results suggest different solid outflow rates for each sector of investigated area. • The model may provide a basis for planning actions and environmental management in coastal zones. [ABSTRACT FROM AUTHOR]

Accuracy of geological modeling and understanding of the controlling parameters in sedimentary systems evolution are challenges in both academy and industry. Uncertainty in the prediction of spatial and temporal facies distributions and difficulties in quantitative analysis of controlling parameters are current challenges. To increase geological model certainty and sedimentary process understanding, computational modeling has evolved exponentially during the last 50 years. In this study, 3D stratigraphic forward modeling technique is used to simulate an ancient transgressive barrier system of southern Brazil, deposited during the Lower Permian in the Paraná Basin, upper part of the Rio Bonito Formation. In the study area, the depositional systems are part of a large transgressive cycle that includes fluvial-estuarine facies at the base and barrier-lagoon deposits (associated with the development of salt marshes) at the top. Throughout the region, offshore strata cover the barrier-lagoon facies. The simulation successfully represented the retrograde evolution of the coastal barrier system, with longshore currents as the main transport mechanism of sediments. The evolution of the barrier system started with upper shoreface deposits overlying the lagoon system facies in the south. Later, lower shoreface sediments covered upper shoreface deposits. Then, shoreline migration continued landward. Finally, offshore transition deposits covered all previous deposits. Simulations and tests of controlling parameters allowed an adjustment to actual thickness and lithologies up to 83%. These simulations allowed for the analysis of model sensitivity, in particular to the influence of parameters that control sedimentary evolution. The main controlling parameter was sediment supply (volume and composition), followed by time step. Initial bathymetry and sediment velocity had less of an impact. • Retrogradation of a barrier system was simulated by 3D stratigraphic forward modeling. • Parameter tests increased similarity between simulated and conceptual model. • Best-fit model reached up to 83% of similarity with the conceptual model. • The most influential parameter in the barrier system simulation was sediment supply. [ABSTRACT FROM AUTHOR]

This study aims to employ a combination of numerical models to simulate bed evolution under various operational strategies within two navigation channels in Mirim Lagoon, Brazil. The model simulations accurately represent the water levels within the lagoon. These findings suggest that river discharge plays a pivotal role in shaping the temporal patterns of sediment transport within the system. The morphodynamic model reveals that sediment transport and bed evolution primarily occur in a southwest-to-northeast direction, following the flow of water. The greatest sediment accumulation is observed in the central and southern regions of the lagoon. Our results confirm that channel dredging induces significant variations in lagoon physical parameters, such as current velocity. The bed evolution results indicate that rapid siltation of the channel follows dredging, suggesting a substantial increase in bottom evolution within the navigation channels compared to the unaltered scenario. Our findings highlight that the utilization of hydromorphodynamic modeling, with a particular emphasis on dredge-and-dump strategies, can serve as a precise methodology to enhance natural mechanisms that positively influence channel depth and stability. This approach also enables us to predict unfavorable changes in physical parameters over both the medium and long term. • The TELEMAC-MASCARET system coupled is used to simulate sediment transport and dredging/dumping process for five years. • The tributaries' discharges mainly control the temporal patterns of sediment transport in the system. • The sediment transport occurred in the southwest to northeast direction, following the main flow direction. • The sediments mainly accumulate in the central and southern regions of the lagoon. • The results affirm that dredging of the channels causes significant variations in the lagoon's physical parameters. [ABSTRACT FROM AUTHOR]

[Display omitted] • Longitudinal influences of low-water crossing on sedimentological connectivity. • Sedimentologic and morphologic modifications due to different rainfall patterns. • Destruction and deposition of sediments and the channel morphology were analyzed. • Low-water crossings mainly interrupt coarser sediments. • Low-water crossings function similarly to check dams, weirs, and sand dams. This study evaluated the longitudinal influences of low-water crossing on the river system and sedimentological connectivity in a Brazilian semiarid basin. The Lower Piancó River basin was chosen as the study area, and four low-water crossings along the catchment were identified and selected for analysis and diagnosis. The effective catchment areas of each structure were delimited, and their impacts assessed over time. Rainfall data from three gauges were used to analyze precipitation events capable of causing significant sedimentological and morphological modifications. These events were classified into three types according to their magnitudes: high, moderate, and low. Sediment samples were collected at each low-water crossing, and lateral profiles were drawn upstream and downstream of the structures to analyze the destruction and deposition of sediments and channel morphology. The analysis showed that the low-water crossings could act as barriers to sediment flow, especially for coarser sediments, and favor the incision of the downstream channel. However, during exceptional flows, the low-water crossings allowed the transmission of sediments due to the clogging of the upstream channel riverbed. This highlighted a unique interaction between the river system and the low-water crossings over time. The results of the connectivity analyses revealed that low-water crossings have a unique impact on the fluvial system compared to other structures, particularly due to their role in the sedimentological connectivity of coarse sediments. Specifically, sediment transport downstream of the crossing emerged as a significant factor in understanding its influence on the surrounding environment. Compared to other types of small longitudinal fluvial interventions, the stage model and low-water crossings displayed structural and aesthetic similarities with floodways and fords. However, functionally, the low-water crossings had strong similarities with check dams, weirs, and sand dams due to their roles in retaining sediments and altering the morphology of the channels in which they are installed. [ABSTRACT FROM AUTHOR]

The Ouricuri do Ouro Formation represents sedimentary deposits of the Statherian period in São Francisco Craton. Previous works have focused just on the Formation mapping, interpreting the depositional system only in general aspects. However, this study focuses on detailed facies analysis and geochronological investigations of the Ouricuri do Ouro Formation in the central area of São Francisco Craton, Brazil. Four facies associations are recognized: i) Proximal deposits dominated by non-cohesive debris flow; ii) Proximal sheetfloods; iii) Intermediate sheetfloods; and iv) Sandy plains of distal floods. Paleocurrent directions derived from cross-bedding indicate a radial pattern to NE-N. The vertical stacking of distal deposits overlying the proximal facies association suggests a retrogradation of the alluvial fan system, indicating a change in the dynamic of the depositional system. Retrogradation might have been caused by a decrease in the regional gradient declining of the tectonic activity or the retreat of the basin's margin faults system. Furthermore, the presence of higher frequency fining-upward cycles also suggests a climatic control in those deposits. These cycles could be results of the progressive decrease in flow capacity and competence, associated with a decrease of superficial runoff over time. Allied with the dominant paleocurrent, the geochronological data of four tuffaceous sandstones reveal the contribution of Rhyacian to Mesoarchean zircons, suggesting that they came with sediments transported from SW and S of the studied area during the Statherian. The transported sediments came from the southern portion of Gavião Paleoplate. The contribution of volcanic zircons recognized in the tuffaceous sandstones is related to syndepositional magmatism of Statherian Rift of Espinhaço Supergroup. The tuff layer at the base of drill hole (Sample FLV-61 A) contains a zircon age with dominant fraction represented by Statherian zircons defining the syn-sedimentary age of 1722 ± 13 Ma at the basal section of the Ouricuri do Ouro Formation. The present results and available geochronological data constraints the depositional interval of Lower Espinhaço Basin or Megasequence (in sense of Chemale et al., 2012; Guadagnin et al., 2015a, b) between <1.80 and >1.68 Ga in the Chapada Diamantina Region. • The Ouricuri do Ouro Formation constitutes a retrogradational alluvial fan system. • The higher frequency fining-upward cycles suggests a climatic control during deposition. • The geochronological data constraints the depositional interval between <1.80 and >1.68 Ga. [ABSTRACT FROM AUTHOR]

Piston core GL-77 was collected in the lower slope of the northern Campos Basin, Brazil, and consists essentially of muds that have been deposited in turbiditic currents over the last 130 ka, at least, which corresponds to the Upper Pleistocene-Holocene interval. The identified ascidian spicules belong to the Didemnidae Family and are represented by species Micrascidites vulgaris , Bonetia brevis , Rigaudia multiradiata and Monniotia fasciculata. These species have irregular abundance and distribution, with Micrascidites vulgaris being the most common. Their occurrence is interpreted as resulting from transport to the depositional site in response to climate fluctuations (glacial and interglacial periods). The transport of ascidian spicules from a shallow-water sea is supported by the presence of terrestrial organic matter, mainly phytoclasts, sporomorphs and microphytoplankton, which were transported to the slope by the river systems. The results found in this study show that the relative frequency distribution pattern of didemnid spicules is a useful tool for monitoring sediment transport in the slope. [ABSTRACT FROM AUTHOR]

Erosion processes can be exacerbated when inappropriate soil conservation practices are implemented. In Brazil, very few measurements are available to quantify the impact of conservation practices on erosion processes in agricultural catchments. The objective of this study is to quantify the impact of different conservation measures on soil erosion and sediment dynamics in an agricultural catchment under no-till of southern Brazil, and to simulate conservation scenarios using a model calibrated with sediment data measured at the catchment outlet. Monitoring was carried out in a large agricultural catchment (800 km 2 ) of southern Brazil affected by extensive soil erosion and runoff despite the widespread use of no-till. Rainfall, river water discharges and suspended sediment concentrations were monitored during a five-year period (2011–2015). The WaTEM/SEDEM model was then calibrated. Then, four scenarios including a Business-As-Usual (BAU) scenario and the implementation of alternative conservation strategies were simulated, and their impact on erosion, sediment deposition and sediment yield was quantified. All four scenarios were simulated twice, using either rainfall measured during a dry year or during a humid year. All the scenarios including alternative conservation measures drastically reduced erosion and sediment yields, with reductions reaching up to 400% when compared to the BAU scenario. The implementation of mechanical conservation measures such as crop levelling and terracing had the highest impact on soil erosion, and the most effective scenario included the implementation of crop rotation, crop levelling, terracing and the creation of forest protected areas. Model simulations indicated that no-till alone has a low impact on erosion processes and that additional measures increasing the vegetation cover/density of the soil are necessary to significantly reduce sediment transfers in these agricultural areas. The simulations also demonstrate that during wet years, erosion processes increase on average by 33.9% for all scenarios. This study demonstrates that soil losses due to erosion processes remain significant and unsustainable in agricultural catchments of southern Brazil. Soil erosion is exacerbated by the lack of information provided to the farmers and the use of isolated conservation measures without coordination at the catchment scale. Farmers’ and local communities’ awareness should be raised to reduce soil degradation and sediment transfer to river systems. [ABSTRACT FROM AUTHOR]

The correct determination of sedimentation processes in caves is often complicated by the unique characteristics of cave environments and their relationship to surface soil. A study at Cuvieri Cave has allowed new insights into the dynamics and evolution of these types of sedimentary facies and their relation to the nearby landscape. The cave is located in the Lagoa Santa Karst, eastern Brazil, and contains fossiliferous deposits of Pleistocene–Holocene age at the base of three vertical pits near the cave entrance. Facies analysis was applied to sediments to understand sedimentation process, and sediments were described according to their morphology, grain-size, micromorphology, chemical composition, paleontological content and age. Results indicate that all deposits present a soil-like aspect and although they record several depositional conditions, sedimentary structures and textures are similar among different facies. As such, facies were defined by a combination of matrix color, degree of cementation and sedimentological characteristics. Additionally, abundance of fauna remains, their taxonomic composition (extant vs extinct), completeness, and degree of individuals' articulation was evaluated. Differences between facies were produced by two main factors: (i) change in source area and transport route (from the epikarst to doline colluviation and back to epikarst) and (ii) change in type of sediment cover injected, from doline fed soils, followed by talus debris and finally soils from modern epikarst. The change in both factors is related to the landscape evolution, mainly with the development and progressive enlargement and deepening of the nearby doline. Additionally, the change in the type of sediment cover injected could also be related to climatic evolution. The complex evolution of Cuvieri Cave sediments occurred over at least the last 300 kyr and is marked by periods in which entrance opening allowed the incorporation of vertebrate (both extinct and extant) remains into the sediment. Detailed multidisciplinary field and laboratory analyses are essential in unraveling the long history of sedimentation in caves, providing a framework in which multiple events of sediment input and erosion can be correctly interpreted and related to the evolution of the landscape. [ABSTRACT FROM AUTHOR]

Brazil has abundant surface water resources, huge aquatic biodiversity and is home to 213 million people. Genotoxicity assays are sensitive tools to detect the effects of contaminants in surface waters and wastewaters, as well as to determine potential risks of contaminated waters to aquatic organisms and human health. This work aimed to survey the articles published in 2000–2021 that evaluated the genotoxicity of surface waters within Brazilian territory to unveil the profile and trends of this topic over time. In our searches, we considered articles focused on assessing aquatic biota, articles that conducted experiments with caged organisms or standardized tests in the aquatic sites, as well as articles that transported water or sediment samples from aquatic sites to the laboratory, where exposures were performed with organisms or standardized tests. We retrieved geographical information on the aquatic sites evaluated, the genotoxicity assays used, the percentage of genotoxicity detected, and, when possible, the causative agent of aquatic pollution. A total of 248 articles were identified. There was a trend of increase in the number of publications and annual diversity of hydrographic regions evaluated over time. Most articles focused on rivers from large metropolises. A very low number of articles were conducted on coastal and marine ecosystems. Water genotoxicity was detected in most articles, regardless of methodological approach, even in little-studied hydrographic regions. The micronucleus test and the alkaline comet assay were widely applied with blood samples, mainly derived from fish. Allium and Salmonella tests were the most frequently used standard protocols. Despite most articles did not confirm polluting sources and genotoxic agents, the detection of genotoxicity provides useful information for the management of water pollution. We discuss key points to be assessed to reach a more complete picture of the genotoxicity of surface waters in Brazil. • We reviewed the genotoxicity studies of Brazilian surface waters that used bioindicator organisms or standardized tests. • Marine and coastal aquatic ecosystems, as well as other continental waters than rivers, were little evaluated. • 79 % of articles evaluated waters from 3 out of the 12 Brazilian hydrographic regions. • Methodological approaches and assays were efficient to detect genotoxicity. • Most articles did not confirm polluting sources and genotoxic agents. [ABSTRACT FROM AUTHOR]

Riparian forest and wetlands act as a barrier that can reduce sediment transfer from crop fields to the water bodies. The present study investigated the sediment source contribution in two paired agricultural catchments with different proportions of riparian vegetation and wetlands, and similar proportion of crop fields, by using the fingerprinting approach. This study was carried out in two catchments from an agrarian reform settlement in Southern Brazil (JC80 – 80.2 ha, and JC140 - 142.6 ha). Sediment sources evaluated were crop fields, streambanks, unpaved roads, and grasslands. Suspended sediments samples were collected during nine storm-events from April 2011 to October 2013. The average contribution of sediment sources in JC80 was 16 ± 19% crop fields, 49 ± 26% streambanks, 15 ± 14% unpaved roads, and 20 ± 22% grasslands, while in JC140 it was 11 ± 12% crop fields, 23 ± 14% streambanks, 41 ± 19% unpaved roads, and 25 ± 14% grasslands. Preserved riparian vegetation, wetlands, and artificial ponds promote sediment trapping and reduce connectivity between cropland and streams, decreasing the amount of sediments transferred to the water bodies. Moreover, the findings from this work also suggest that unpaved road contributions depend on the number of junctions between roads and the stream network. [ABSTRACT FROM AUTHOR]

Confluences are important environments within the drainage system for exchanges in energy, sediments, water, and the control of local ecology. Despite the significant advances in the understanding of confluences, the study of the junction of small rivers with very large rivers is still incipient. We present a case study of a confluence bar with an extremely low discharge ratio (Qr = 0.0002) and a high obtuse confluence angle (145°) just downstream of the Porto Primavera Dam, in the Upper Paraná River, Brazil. Our analysis includes bathymetric and sedimentological data from surveys prior to dam closure (1997), and after dam closure (2006, 2018), spanning a total of 21 years. Dam closure reduced the mean water level and suspended sediment load in the Paraná River, as well as controlling the occurrence of natural floods. Although the São Pedro Creek confluence bar has reduced, in terms of spatial area and sediment input, its morphology, sedimentation zones, and hydrodynamics has been preserved during this time frame (1997–2018). The stability of the confluence bar is probably mainly due to the high confluence angle (structural control) that causes high resistance in the Paraná River flow, allowing the generation of a large stagnation flow zone (depositional area). The Upper Paraná River, which is one of the most dammed watersheds in the world, has the São Pedro Creek and other small tributaries as important sediment sources for suspended load, mainly after the Porto Primavera dam construction. The results indicate that the stability of the São Pedro confluence bar is due to the association of the systems involved in the supply of sandy sediment, but mainly due to the obtuse angle, that imposes local conditions of flow and sedimentary circulation necessary for its formation and morphological maintenance. • Bottom and suspended sediment transport from the Upper Paraná River has reduced due to the dams concentration. • The Upper Paraná River reduction sediment transport affected the area and height original of the channel bed forms. • The obtuse angle helps to preserve the sedimentology and geomorphology of confluence bars of dammed systems. • Small obtuse-angled tributaries are important in preserving flow, sedimentation, vegetation, and confluence ecology. [ABSTRACT FROM AUTHOR]

[Display omitted] • The SWAT model supports better management of erosion processes. • Computational models can be used with methods of visual recording erosion. • Simple statistical models aligned to SWAT is adequate to analyze erosive processes. • The spatially distributed erosion identifies the susceptible areas to water erosion. Water-driven erosion associated with the transport and deposition of sediments in watersheds may lead to contamination problems causing significant damage to land and infrastructure. The key factors that influence erosive processes are well known and include the precipitation rate, terrain topography, soil type, and vegetation cover. The soil and water assessment tool (SWAT) considers these factors and may be used to identify areas susceptible to soil erosion and to estimate soil loss and sediment transport and deposition. To corroborate this assumption, real data on rill erosion and sediment transport from the Mogi Guaçu River Basin in southeastern Brazil were used to validate SWAT estimates. The study shows that the model is able to identify soil-eroded areas and replicate the scale and variation patterns of sediment production, although not with great precision. Hence, it can successfully be used for prioritizing areas that require action and for evaluating alternative soil management and conservation practices to mitigate erosive processes. [ABSTRACT FROM AUTHOR]

Due to the low preservation potential of their multi-elemental endoskeletons, fossil ophiuroids can be used as a proxy for exceptional preservation conditions. Following this principle, this study investigates the taphonomic history of ophiuroid beds across three sites in southern Brazil, where Devonian epicontinental sequences from the Ponta Grossa Formation are well-represented. Through fieldwork, tomographic analysis, and description of 218 samples, five taphonomic grades were listed to represent the paleoecological and sedimentological histories of these ophiuroid beds. Three high-order taphonomic grades symbolize articulated ophiuroids suddenly buried in life, comprising sparse skeletons parallel to bedding planes, skeletal clusters oriented on specific horizons, or skeletons in escape postures inclined at low angles on bedding planes. Two low-order taphonomic grades include ophiuroids buried between hours to a few days after death, reflecting skeletons disarticulated in a normal sequence of microbial decay or skeletons selectively disarticulated by macrobenthic groups. These records suggest that fluvial discharges were the main burial mechanisms for ophiuroids, since they may transport freshwater-rich sediments, favoring the mass numbing of vagrant echinoderms. In contrast, storms were probably only a subordinate burial process, considering that they remobilize sediments without a key anesthetic for these echinoderms. Furthermore, carbonaceous compressions were recorded for the first time in fossil echinoderms through kerogenization of visceral organs in the disk of ophiuroids, apparently with associated pyritization. Considering the studied data, these ophiuroids probably thrived in different seafloors, although they have been preserved mainly in distal marine regions free from intense interference from waves, currents, and bioturbators. Due to the presence of well-articulated echinoderms and the exceptional preservation potential of other associated fossil groups, the Ponta Grossa Formation can be classified as a Konservat-Lagerstätte of the Devonian of Brazil. [Display omitted] • First evidence of kerogenization in fossil echinoderms. • A new echinoderm Lagerstätte in the Devonian of Brazil. • Evidence of macrobenthic disturbance of ophiuroid carcasses. • Escape postures in different burial conditions, sometimes with associated autotomy. • River discharges were more able than storms to numb and bury errant echinoderms. [ABSTRACT FROM AUTHOR]

The migration of transgressive coastal dunes over urban and farming areas is commonly observed in the semi-arid northern coast of the Brazilian northeast. However, it is unusual in the humid tropical coast of southeastern Brazil. This paper aims to investigate the aeolian dynamics and the drivers of the burial process over the Itaúnas District, Espírito Santo State landscape, by transgressive coastal dunes. Methodological procedures consist of remote sensing techniques, geoprocessing, wind regime simulations, and mathematical calculations of migration rate parameters. Satellite images were georeferenced using ArcGIS 10.3 software and wind regime information was simulated using HYSPLIT software using wind reanalysis data. The results suggest a sediment transport rate of 44.98 kg/m/s, wind drift potential of 123.96 v.u. and dune migration rate estimated at 4.0 m/yr. It was found that the northern and western sectors of the studied dunefield have the highest migration rates towards the main access road, water resources and urban area. The values obtained are considered significant because it is a coastal segment subjected to a humid tropical climate. • New data on the burial process by moving dunes over Itaúnas District, Brazilian Southeast, are presented. • It is suggested that the cause of the burial process is associated with deforestation of beach ridge by human activity. • Obtained results suggest a dune mobility rate of 4.0 m/year. • Results obtained suggest a sediment transport rate in the order of 44.98 kg/m/s and a wind drift potential of 123.96 v.u. [ABSTRACT FROM AUTHOR]

A coastal inflection of ∼45 km in the extreme south of Brazil demonstrates differences in coastline behavior with areas of deposition towards north and areas of severe erosion towards south, threatening coastal occupation. These areas are believed to be controlled by the sand wave behavior of the coastline with adjacent erosion and progradation areas that have relevant alongshore sediment transport imposed by S quadrant waves. In this study, we quantified the rates of change of coastline and described the erosion and deposition controls behind it, using ultra-high-resolution orbital images and UAV (unmanned aerial vehicle) orthomosaics obtained between 2005 and 2020 for three urbanized beach sectors within the area, i.e., the São Simão, Mostardense, and Lighthouse Beaches. The rates of change of coastline were calculated using the change polygon method. The results indicated total recession values > 40 m at the Mostardense and Lighthouse beaches corresponding to a rate of ∼3 m/y. Such values characterized the coastal erosive hotspots that have not been previously identified in the area. Future coastlines were projected from the estimated annual variation rates. Buildings previously destroyed or threatened by marine/wind processes were also mapped. A continuous high-resolution and high-frequency coastal monitoring approach for the area is essential for planning the future development of these beaches to minimize and possibly avoid environmental degradation. • New erosive hotspots under discussion in extreme south of Brazilian Coast. • Drone surveys applied for coastal management in sand beaches. • Socio-environmental impacts of unplanned urbanization in Brazilian Coast. [ABSTRACT FROM AUTHOR]

The Meaípe-Maimbá embayed beach (MMEB) on the south-east coast of Brazil has been subject to anthropogenic pressures since the 70's. In this study we discuss the adequacy and contribution of the parabolic planform model to determine the planform and variability of the MMEB, taking into consideration variation in wave conditions. The role of different controlling conditions on the planform variability is analyzed, as well as the morphological and planform mobility. MMEB exhibited a new configuration in response to the construction of a harbor, which interrupted the longshore sediment transport. After four decades, three particular morphodynamic sectors have been recognized along the beach. The central sector is more exposed to normal wave incidence and cross-shore processes predominate. The northern and southern sectors are influenced by wave diffraction processes around the headlands and port, respectively. In the northern sector, the presence of secondary headlands and inner islands imposed a geomorphological control on beach morphology and coastal processes. The use of the parabolic planform model provided useful insights for the assessment of potential planform mobility, since the decadal shoreline evolution combined with beach profiles and sediment characteristics allowed understanding of the beach mobility processes and supported the interpretation of modeling results. [ABSTRACT FROM AUTHOR]

This paper presents transport of a mixture of cohesive sediments and sand in the Paranagua Estuarine Complex in the south of Brazil. The estuary houses a navigation channel from the Atlantic Ocean to a busy harbour. The channel requires frequent dredging owing to sediment deposition to maintain navigable depth for vessels. A three-dimensional process-based model for sediment transport coupled with wave-current models based on the Delft3D modelling system is constructed for the estuary. Extensive field data concerning current velocity, water level, salinity and suspended sediment concentration were collected. The flow model that is necessary to run the sediment transport model was calibrated and validated using field measurements. In this paper only the results concerning the sediment motion are presented. Calibration and validation of the numerical model show that the results of sediment transport represent the field conditions well. Additional support for the validity of the computed results is provided by field data pertaining to bathymetry acquired in 2005 and 2006. The present study gives insight into the motion of cohesive sediments and the morphological behaviour of the estuary, and should help operators maintain the channel for navigation. [ABSTRACT FROM AUTHOR]

River confluences are sites that operate with complex interactions between material and energy, provided by the combination of different flow patterns that present continuous changes in flow structure and sediment transport. In addition, river confluences have intrinsic ecological value, where biophysical processes and ecosystem services may be concentrated. This study aimed to analyze the morphology, flow structure, and hydrosedimentary interaction along tributary-trunk river confluences in a bedrock-alluvial plateau basin. The study included a field investigation into the mixed bedrock-alluvial basin of morphology, bed sediments, and hydrologic condition (including the flow structure) of 29 confluences to identify and analyze the similarities and differences between these confluences at the basin scale. For example, we considered the Ivaí River Basin, a medium-sized dam-free river that exhibits a mixed bedrock-alluvial bed and heterogeneity in both geology and longitudinal profile. Our findings show that the flow structure and morphology are conditioned by geological aspects, and the composition of the flow is extremely affected by the Ivaí River. In general, our results presented distinct differences from field-based data described in the literature for alluvial river confluences. • Study of flow structure, morphology, and bed sediments in river confluences based on field measurements. • Influence of physiographic properties on hydro-sedimentary aspects in river confluences. • The characteristics of river confluences in mixed bedrock-alluvial channels. [ABSTRACT FROM AUTHOR]

At wave-dominated coasts, it is common the presence of coastal barriers that can be of different typologies and whose dynamics can influence the formation of lagoon systems. Along southeastern and south Brazil the dynamics involving barrier-lagoon evolution is related to wave and aeolian process associated with sea-level behavior. For a better understanding about the relationship regarding to coastal process, barriers, and lagoons the application of geophysical techniques enables to identify morphostratigraphic characteristics improving the acknowledgment of the main processes forming these morphologies. In this study, a 1.4 km long common-offset GPR profile, in cross-shore direction, was surveyed in order to obtain the internal depositional architecture of the sandy coastal barrier to the east of Salgada lagoon, located in the wave-dominated Paraiba do Sul river delta, in southeastern Brazil. The GPR allows to describe morphostratigraphic characteristics imprinted by sediment dynamics and how it is related to the lagoon system formation. Eight radarfacies were identified, grouped according to the coastal barrier pattern, divided in barrier spit and beach ridge, and sediment transport characteristics. Five radarfacies comprise the barrier spit environment and three the beach ridge environment. The barrier spit environment radarfacies showed different characteristics of the portions of the spit sequence (initial, medium or distal), and along with its subsurface imaging angle (parallel, oblique or transversal to the spit growth direction) providing highly detailed data regarding those barrier types. This recognition allowed the interpretation of a previous spit, approximately 3 m deep, located under another one that overlapped it. Also, spit accretion records were found, which occur due to the seaward exposure to high-angle wave action. Meanwhile, the beach ridge environment radarfacies revealed the typical pattern of progradation due to swash processes, and also the occurrence of berm ridge accretion and overtopping/overwashing processes. The integrated analyses using the subsurface data indicated that the evolution of the targeted coastal barriers and the lagoon can be divided into four stages. The first stage is the most landward barrier spits growth, where Salgada lagoon was beginning its closing process. This is followed by the second stage with the continuity of barrier spits growth but with changes in spits orientation. The third stage represents an erosive phase, with a major erosive truncation that probably eroded a significant area of the spits. At the last stage suggested there was a subsequent accumulation phase, marked by the formation beach ridges. Besides that, it is also important to recognize that the development of coastal barriers of different types at the site showed an alignment variability of paleocoastlines. While barrier spits revealed variation in their orientation, beach ridges have kept their alignment more constant. This fact occurred independently of erosive episodes. Furthermore, the GPR profile acquisition strategy made it possible to investigate the spit from different perspectives, which helped with the interpretation of deeper radarfacies. • Different morphostratigraphic patterns observed from barrier spit to subsequent beach ridges formation identified using GPR. • Lagoon enclosing related to the regressive barrier spit development; barrier spit set erosion; and beach ridges set formation. • Landscape evolution proposal with four main phases in a highly dynamic coastal area in a wave-dominated deltaic context. • Understanding lagoon and coastal barriers evolution contributes to sedimentary capes developed during Holocene knowledge. [ABSTRACT FROM AUTHOR]

Abstract: Water and suspended sediment fluxes are considered during the period 2000–2008 in a region including the full Amazon River from the confluence of the Negro River to Santarém, the end part of the Solimões River, and the lower part of the Madeira River. Three types of data are used: water discharge estimated from field measurements, and suspended sediment obtained from field measurements and derived from MODIS satellite data. A generalized least square method including a propagating term is developed in order to propagate the signal upward and downward the river. The approach is introduced and tested. Several experiments are considered in order, first, to estimate the ability to propagate the signal from stations located before the confluences of Negro and Madeira Rivers to stations located on the Amazon River; second to investigate the possibility to propagate the signal along the Amazon River which dynamics is coupled with floodplains dynamics; and third to produce optimal solutions of water and sediment fluxes. For each experiment, the influence of field and satellite data is compared. The approach is efficient in the upper part of the region of study where the Solimões, the Negro and the Madeira Rivers meet and fails in the lower part of the region where interactions between Amazon River and floodplains play an important role on the fluxes’ dynamics. The optimal experiment includes in situ and satellite data from all the stations available and is used to analyse the recent evolution of suspended sediment flux along the Amazon River and its interaction with the large coupled floodplains. A high accumulation rate is observed during the 2000–2002 period, followed by decreasing rates until 2005 and by increasing values in 2006 and 2007. Our results suggest that floodplains extending along a river reach of 390km-long between Itacoatiara and Óbidos trap about 15% of the suspended sediment flux passing at Óbidos. The simulated deposition rate is of about 0.3Mtkm−1 yr−1 corresponding to an accretion rate of about 27mmyr−1. [Copyright &y& Elsevier]

Abstract: Natural cycles of irradiation during burial and bleaching due to solar exposure during transport increase the Optically Stimulated Luminescence (OSL) sensitivity of quartz sand grains. The relationship between the OSL sensitivity and sediment transport allows to discriminate quartz sand grains with different depositional histories. In this paper, we evaluate the variation of OSL sensitivity in quartz grains deposited during the progradation of the Ilha Comprida barrier on the southern Brazilian, coast. Changes in sand sensitivity recorded by barrier growth since 6 ka ago are controlled by the variation in the proportion of low versus high sensitivity quartz grains. Low sensitivity grains with short sedimentary history are supplied by the Ribeira de Iguape River and reach the barrier through southward alongshore currents during fair weather conditions. Storm conditions shift the alongshore currents to northeast and permit the transport of high sensitivity grains with long sedimentary history from distal southern coastal sectors to the barrier. Therefore, the input of distal sediments for the Ilha Comprida barrier depends on the frequency and intensity of storms. Thus, the OSL sensitivity can be used as proxy for storm activity. The variation of OSL sensitivity through time indicates that the Ilha Comprida barrier changed from a relatively stable to an unstable storm pattern around 2 ka ago. Periods with increased storm activity peaked around AD 500, AD 1500 and AD 1850, approximately on the boundaries of the Medieval Climate Anomaly and the Little Ice Age. [Copyright &y& Elsevier]

Abstract: This paper presents a comprehensive study of wave refraction, wave and wind driven sediment transport, foredune development and Holocene barrier evolution over a variety of time scales at Moçambique Beach, Santa Catarina State, Southern Brazil. The motivation for this study was to examine the relationships between estimated wave driven sediment transport, medium and long term aeolian transport, foredune development, and Holocene barrier volumes and morphology. An analysis of 2years of wave rider data for the region shows two well defined peaks of frequencies: one of swell waves from the south with a period of 12s, and another peak of sea waves from east-northeast with a period of 7s. Longshore sediment transport rates were calculated using high resolution hindcast wave data for the South Atlantic Ocean, which was calibrated by the measured buoy data. The dominant southerly waves drive a longshore gradient in wave energy from south to north, and nearshore/surf zone sediment transport increases from south to north. Beach grain size is fine in both the south and north, and medium in the center. The combination of grain size and wave energy variations creates a marked alongshore variation in surf zone beach types ranging from low energy dissipative in the south, moderate energy intermediate in the central area to moderate to high energy dissipative in the north. Estimates of aeolian sediment transport, volumetric changes in foredune deposition and total Holocene dunefield volumes were also calculated. Results indicate that the morphological behavior of the foredune profiles reflects the gradients of longshore sediment transport and the exposure to wind energy and aeolian sediment delivery, with a maximum of sediment volume and transport towards, and in the central part and northern end of the barrier. Holocene (0–7000years) barrier volumes vary along the embayment, mimicking the trends in both calculated wave and wind driven sediment transport. The Short and Hesp (1982) model was more suitable in predicting the long term (Holocene) barrier evolution than the size and volume of the foredune. The combination of wide beach, high energy dissipation, maximum sediment supply, and high exposure to strong onshore winds is found in the northern end of the embayment where Holocene subaerial barrier volumes are at a maximum. Overall, this study proves that foredune development is closely related to wind exposure, wave energy and gradients of longshore sediment transport, and that dunefield development reflects the increase downdrift in potential sediment supply from the southern to the northern end of the beach, and the change alongshore from low energy dissipative, through intermediate, to high energy dissipative beach-surf zone environments. This paper significantly extends previous models of beach and dune interactions in that it (i) actually determines wave driven sediment transport for various sections of a long embayment, (ii) relates those transport patterns to surf zone/beach morphodynamic types and variations in alongshore sediment patterns, and (iii) correlates foredune volumes and Holocene barrier volumes (which reflect proxy Holocene onshore transport rates) with wave driven sediment transport rates. [Copyright &y& Elsevier]

Abstract: Natural gamma radiation of beach sand deposits was measured along the south coast of Rio de Janeiro State, Brazil, with the aim of studying the provenance and transport processes of sediments in this area. Concentrations of thorium, uranium and potassium were evaluated using γ-ray spectrometry and a behavioral study of eTh/eU and eTh/K cross plots was performed, reflecting the mineralogical properties of beach sands, as well as their history of transport and sorting processes. The results show that such technique can be efficiently used to map heavy mineral distributions and to distinguish the different origins of coastal sediments disclosing the influence of nearby rivers. [ABSTRACT FROM AUTHOR]

Abstract: Ilha Comprida is a regressive barrier island located in southeastern Brazil that was formed essentially by Quaternary sandy sediments. Ilha Comprida sediments were analyzed to assess heavy mineral indices and grain size variables. The spatial variation of heavy minerals and grain size was interpreted in terms of the present barrier dynamics and the barrier’s evolution since the Middle Holocene. These analyses allowed for the identification of the main factors and processes that control the variation of heavy minerals and grain size on the barrier. Rutile and zircon (RZi) and tourmaline and hornblende (THi) are significantly sensitive to provenance and exhibit the contributions of the Ribeira de Iguape River sediments, which reach the coast next to the northeastern end of Ilha Comprida. In addition to the influence of provenance, TZi responds mainly to hydraulic sorting processes. This agrees with a sediment transport pattern characterized by a divergence of two resultant net alongshore drifts southwest of the barrier. The sediments from the Ribeira de Iguape River reach the barrier directly through the river mouth and indirectly after temporary storage in the inner shelf. The combination of grain size and heavy mineral analyses is a reliable method for determining sediment transport patterns and provenance. [ABSTRACT FROM AUTHOR]

Abstract: This paper examines the role of coastline orientation on foredune and dunefield development at Moçambique Beach, Southern Brazil. The beach displays significant alongshore variations in exposure to the prevailing winds and waves, grain size, beach/surfzone morphodynamic type, foredune volume, and type and dimensions of the Holocene dune systems. Two wind analyses and calculation of aeolian drift potentials were carried out, one based on 1year of wind record and another based on a record of 34years. Monthly topographic surveys of beach and foredunes on 5 profiles along Moçambique beach were conducted over one year to obtain data on beach mobility and width, aeolian sediment transport and foredune development. Southerly winds dominate, and aeolian sediment supply is minimal in the south, moderate in the central portion and high in the northern portion of the embayment. The relationship between actual sediment supply, foredune building and potential sediment supply is relatively poor over one year due to factors such as beach type and mobility, beach moisture levels, rainfall, storm surge and wave scarping. The intermediate term (34year) record indicates a strong relationship between foredune size and volume, winds and shoreline orientation: foredune volume is minimum in the southern part of the beach and greatest in the northern part of the beach. The Holocene barrier and dunefield development also reflects the long term control of shoreline orientation and increasing longshore gradient in exposure to southerly winds: for the last 6000–7000years a small foredune developed in the southern portion, parabolics and small transgressive dunes in the central portion, and a large-scale transgressive dunefield in the northern portion. [Copyright &y& Elsevier]

Abstract: Natural gamma radiation measurements of sand deposits were carried out in order to study the chronology of prehistoric colonization of the Brazilian coast during the Holocene. The method employs thorium, uranium and potassium as tracers of the geological provenance of Quaternary deposits, where artificial shellmounds are found. The so-called sambaquis are archaeological settlements, characteristic of fisher–gatherers, specialized in the exploitation of shellfish. Our results show a considerable positive correlation between the formation of coastal deposits, based on cross plots of eTh/eU and eTh/K, and the antiquity of its prehistoric human occupation. [Copyright &y& Elsevier]

Abstract: Caves associated with doline slopes in the tectonically stable area of eastern Brazil display remarkable sequences of clastic sediment intercalated with calcite layers. Sediment erosion has also occurred allowing access to formerly sediment-filled passages. The palaeoenvironmental meaning and chronology of these three processes (i.e. clastic sediment input, clastic sediment erosion, and speleothem precipitation) were studied in both semi-arid Campo Formoso and sub-humid Lagoa Santa areas through 230Th dating and stratigraphical analyses. The dry climate of the Campo Formoso area prevents speleothem deposition at present, but soil erosion results in valley aggradation and cave infilling. Growth periods of speleothems and travertines in this area have allowed the recognition of recurrent past phases of increased humidity correlated with wet conditions recorded in southeastern Brazil speleothem calcite. At the Lagoa Santa area there is limited speleothem precipitation and sediment input at present. However, sediment entrainment is actively exhuming speleothems and exposing cave passages. Sediment erosion inside caves in the area is interpreted as being due to intermediate climatic conditions, not wet enough to favour speleothem deposition and not too dry to allow doline slope erosion and sediment transport into caves. Due to the low rates of denudation and isostatic rebound inherent to tectonically stable areas, cave passages will remain within the range of sediment infill and erosion for a much longer time than in tectonically active areas spanning, in average, at least three full glacial–interglacial cycles. As uplift proceeds, cave passages will be decoupled from the doline bottom and no longer will be affected by erosion or infilling episodes. Sediment filled passages in many caves in the Lagoa Santa region are relict features that display ancient clastic and chemical precipitation. The three processes described above have occurred throughout the life history of the caves, resulting in complex sediment assemblages that can, however, show significant intra- and inter-site variations. [Copyright &y& Elsevier]

Abstract: This paper proposes an explanation of the mud deposits on the inner Shelf of Cassino Beach, South Brazil, by using computational modeling. These mud deposits are mainly formed by sediments delivered from Patos Lagoon, a coastal lagoon connected to the Shelf, next to Cassino Beach. The deposits are characterized by (soft) mud layers of about 1m thick and are found between the −5 and −20 isobaths. Two hydrodynamic models of the larger Patos Lagoon–Cassino Beach system were calibrated against water elevation measured for a 5 months period, and against currents and salinity measured for a week period. The circulation patterns and water exchange through the mouth were analyzed as a function of local and remote wind effects, and river discharges. The remote wind effect mainly governs the quantity of water exchange with the Lagoon through its effect on mean sea level as a result of Ekman dynamics, while river discharges are important for the salinity of the exchanged water masses. Local winds augment the export–import rates by set-up and set-down within the Lagoon, but their effects are much smaller than those of the remote wind. Currents patterns on the inner Shelf during water outflow revealed a recirculation zone south of the Lagoon, induced by the local geometry and bathymetry of the system. This recirculation zone coincides with observed locations of mud deposition. Water, hence suspended sediment export occurs when remote and local winds are from the N–E, which explains why fine sediment deposits are mainly found south of the Lagoon''s breakwater. A sensitivity analysis with the numerical model quantified the contribution of the various mechanisms driving the transport and fate of the fine suspended sediments, i.e. the effects of remote and local wind, of the astronomical tide, of river discharge and fresh–salt water-induced density currents, and of earth rotation. It is concluded that gravitational circulation and earth rotation affects the further dispersion of the deposits largely, whereas the remote wind effect has the largest influence on the amount of sediment released from the Lagoon. It is noted that this paper analyzes the initial deposition patterns induced by current effects only. However, in reality, these deposits are further redistributed over the Shelf by wave effects—these are subject of a next study on the sediment dynamics of the larger Patos Lagoon–Cassino Beach system. [Copyright &y& Elsevier]

Abstract: Neodymium and lead isotope values in sediment samples were used to interpret sediment transport and source rocks on the Southeastern South American upper margin. The sediments of the Argentinian margin exhibit an average ɛ Nd value of −1.9, indicating the influence of the Andean rocks as sediment sources. Sediments from the Río de La Plata estuary show an average ɛ Nd value of −9.6 which is similar to that of the Southern Brazilian Upper Margin. Finally, sediments of Southeastern Brazil, which are associated with the transport of the Brazil Current exhibit an average ɛ Nd of −13.0. The Pb isotope signatures also confirm the differentiation of source rocks in the sedimentation of the study area. In addition, Pb isotopes helped to establish the extent of the influence of the Río de La Plata on the sedimentation of the Southern Brazilian margin. In terms of Pb isotopes the sediments from the Río de La Plata estuary and Southern Brazil are more radiogenic than those of Southeastern Brazil and the Argentinian margin. [Copyright &y& Elsevier]

Summary: Empirical relationships coupled with the field measurements were used to assess water discharge and sediment load from an anthropogenically-altered drainage basin into Sepetiba Bay in southeastern Brazil. Discharge into Sepetiba Bay is modified by large-scale water diversion from the Paraíba do Sul River, which is one of the more important and impacted rivers in Brazil. The discharge into Sepetiba Bay has increased threefold, from 41 to 129m3/s on average, since the water redistribution began. Sediment budget calculations indicate retention of a large fraction of the sediment load by five reservoirs within the drainage system but with highly variable infilling rates. As a consequence the water diversion scheme has lead to a 28% increase in sediment delivery to Sepetiba Bay or 270×103 t/yr. The Paraíba do Sul River contributes most of the freshwater input into Sepetiba Bay, whereas the sediment load to the bay is mainly contributed by the local drainage basins. [Copyright &y& Elsevier]

U–Pb and Lu–Hf data obtained from detrital zircon of 21 samples from four wells were used to determine the source terrains of the Cretaceous sedimentary rocks of the Pendência, Pescada and Alagamar Formations (rift and post-rift sections) of Potiguar Basin, northeast Brazil. More than 1500 U–Pb concordant ages allowed the determination of the main age peaks in Paleoproterozoic (ca. 2.2–2.0 Ga and 1.9–1.7 Ga) and Neoproterozoic (ca. 0.62–0.55 Ga), matching the ages of rocks from the basement adjacent to the basin (northern portion of Borborema Province). εHf values obtained from 61 zircon grains range from −0.53 to −8.86 for Paleoproterozoic and from 7.67 to −25.43 for Neoproterozoic zircons, consistent with published data from rocks of the adjacent basement. Neoproterozoic zircons shows εHf values more negative from bottom to top, and presents a trend in U–Pb age vs εHf where the older grains show juvenile signature and the younger, continental crustal signature. This trend mimics the evolution of granitoid generation in the basement adjacent to the Potiguar Basin during the Neoproterozoic orogeny. The age pattern varies vertically in most wells, reflecting the contribution of distinct source areas following the rift evolution. Furthermore, the age pattern in the wells located at southeast of the grabens and horsts system of the onshore Potiguar Basin show Paleoproterozoic zircons concentrated in a single peak age, few or no zircon grains of 1.8–1.6 Ga and lesser amount of 0.6–0.7 Ga zircons, in contrast with the wells located at northwest, with Paleoproterozoic ages distributed in more than one peak, significant presence of 1.8–1.6 Ga zircons and proportionally more 0.6–0.7 Ga zircon grains. It suggests that this system acted as a barrier to sediment transport, delimiting the basin in two sectors fed by two different sources, one being the northeast portion of Borborema Province and the other, the northwest portion, both in the rift and post-rift sections. Such differences can result in distinct quality for the potential reservoirs in these sectors and would be an important guide for hydrocarbon exploration in Potiguar basin. • Zircon U–Pb ages and Lu–Hf isotopic analyses revealed provenance on Potiguar Basin rift and post-rift sections. • Northern portion of Borborema Province acted as sediment source. • Zircon indicates two distinct sectors in the basin in terms of provenance. • Lu–Hf data reflects the evolution of Neoproterozoic granitoid generation in the adjacent basement. [ABSTRACT FROM AUTHOR]

• Bedload transport rate was measured in a mixed bedrock–alluvial stream. • Patch classes were mapped to consider the effects of macro-roughness. • Equation predictions are improved by including the macro-roughness. • Equations predictions are also improved by including limited sediment mobility. • Flow resistance equations understate energy loss in mixed bedrock–alluvial streams. Mixed bedrock–alluvial channel beds are common in mountain rivers. It is well-known that in such system the balance between sediment supply and transport capacity defines either the level of the exposure of bedrock (in the riverbed) or its coverage by alluvial material. We investigate whether applying the representation of the energy losses (caused by macro-roughness) developed for alluvial channels improve the capacity of bedload transport equations to predict the bedload transport in a mixed bedrock–alluvial stream. Therefore, the purpose of this study was to evaluate the performances of five bedload equations against field measurements, while considering the effects of macro-roughness on the equations and the limited availability of mobile sediment. We analyzed the data collected in a stream located in southern Brazil, which has a 2.3% gradient and mixed bed conditions. Optimal results in estimating the bedload transport rate were obtained when using the reduced shear stress τ ' and reduction factor of the available bed material (Frm) together in the five tested equations. Analyzing the two approaches separately, the implementation of τ ' proved to be more critical for improving the performance of the equations than using Frm alone. Among all the equations, Recking (2013) presented the best result for the case in which 85.2% of the estimates fell within one order of magnitude of the measured transport rates (0.1 < r > 10.0); this was followed by the Recking (2010) (70.4% of estimates within one order of magnitude) and Meyer-Peter and Müller (1948) (37% of estimates within one order of magnitude) equations. In conclusion, we observed that even by implementing flow resistance and with the limited availability of mobile sediment, the equations overestimated the bedload transport rate in the studied river reach, indicating an underestimation of energy loss in the flow resistance equations of mixed bedrock–alluvial channels. [ABSTRACT FROM AUTHOR]

• Nonoccurrence samples acquisition is relevant to resulting susceptibility maps. • ANN models can lose generalization ability if training set is too easy to classify. • Using only easy-to-classify nonoccurrence samples affects maps negatively. Landslide susceptibility assessment using Artificial Neural Networks (ANNs) requires occurrence (landslide) and nonoccurrence (not prone to landslide) samples for ANN training. We present empirical evidence that a priori intervention on the nonoccurrence samples can produce models that are improper for generalization. Thirteen nonoccurrence cases based on GIS data from Rolante River basin (828.26 km2) in Brazil are studied, divided in three groups. The first group was based on six combinations of buffers with different minimum and maximum distances from the mapped scars (BO). The second group (RO) acquired nonoccurrence only from a rectangle in the lowlands, known for not being susceptible to landslides. For BR, six alternatives respectively to BO were presented, with the inclusion of nonoccurrence samples acquired from the same rectangle used for RO. Accuracy (acc) and the Area Under Receiving Operating Characteristic Curve (AUC) were calculated. RO resulted in perfect discrimination between susceptible and not susceptible to landslides (acc = 1 e AUC = 1). This occurred because the model simply provided susceptible classification to points in which attributes are different from those in the rectangle, harming the classification of nonoccurrence sampling points outside the rectangle. RO map shows large areas classified as susceptible which are known to be non-susceptible. In BR, sampling points from the rectangle, which are easy to classify, were added to the verification sample of BR. Average acc for BO 00 m (minimum buffer distance to scars of 0 m): 89.45%, average acc for BR 00 m: 92.33%, average AUC for BO 00 m: 0.9409, average AUC for BR 00 m: 0.9616. Maps of groups BO and BR were alike. This indicates that metrics can be artificially risen if biased samples are added, although the final map is not visibly affected. To avoid this effect, the employment of easily classifiable samples, generated based on expert knowledge, should be made carefully. [ABSTRACT FROM AUTHOR]

• The Bruun method was adapted for assessing tidal inlet short term morphodynamics. • Instantaneous tidal prism/marine drift ratio is used for tidal inlet assessment. • Shoaling occurs when the tidal prism/marine drift ratio decreases under 20. • Annual total longshore transport rate at Praia Seca (RJ - Brazil) is calculated. • Morphodynamics of an alternative inlet channel in the Araruama Lagoon is studied. Longshore sediment transport and tidal prism are key factors in analyzing the stability and morphodynamics of a tidal inlet. Stablished by the Bruun theory, the ratio between the maximum spring tidal prism (P) and the annual total littoral drift (M T) is a parameter widely used to diagnose the stability condition of tidal inlets and to validate inlet morphological modeling results. However, the P / M T relationship is adequate for mid-term and long-term analysis only (i.e. weeks, months, years or decades). Depending on the wave climate, one may observe intense accretion in a tidal inlet in a time scale of hours to few days during storm events. No empirical criterion is yet known to be applicable for supporting analysis in such a short time scale. This work presents a modified approach of the traditional Bruun criterion, adapted for assessing short-term (i.e. hours or days) morphological evolution of tidal inlets. Instead of P and M T , the method here addressed considers the ratio between the tidal prism (P i) and the longshore transport volume (M T i ) integrated both over the flood period of every tidal cycle. This methodology was applied in the analysis of storm and post-storm induced morphodynamic response of a projected tidal channel, proposed to improve water quality in the Araruama Lagoon, Rio de Janeiro, Brazil. Hydro-sedimentological numerical modeling was used to simulate a scenario which encompassed three cycles of storm induced accretion and post-storm induced inlet development. Correlation was noticed between the patterns of short-term morphodynamic response and the temporal variations of the instantaneous P i / M T i ratio. This research also presents calculations on the longshore sediment transport rate during the four seasons for the studied region. [ABSTRACT FROM AUTHOR]

Vegetation is one of the main factors that compose the alluvial dynamic of the semiarid environment. The determination of the hydraulic roughness generated by the plant in the alluvial environment is essential to understand the behavior of the forces that describe the flow, the processes associated with the loss of energy and the sediment transport rates. The objective of this study is the characterization of the flow resistance imposed by an aquatic vegetation patch in an intermittent stream, located in Pernambuco's hinterland, Brazil, in the emerged and submerged conditions, through the parameters of vegetal drag coefficient (C D) and vegetal drag stress (τ veg) of the different intrinsic species of this alluvial environment. The sampling took place in the Cachoeira intermittent stream to monitor the channel geometry, vegetative parameters, and liquid and solid discharges. Based on the submergence ratio, the flux was divided into two distinct layers that allowed the understanding of hydro-sedimentological dynamics, the first one of direct contact with the vegetation and the second one the free flow zone. The average values of C D to the aquatic vegetation patch (composed by Senna obtusifolia , Ipomoea pes-caprae and Cynodon dactylon (L.) Pers.), according to the methodologies adopted in this study, were 10.97 and 3.73 m−1. The generated physical forces were in opposition to the flow and, consequently, in the condition of increase of the vegetal density, they promoted the higher values of vegetal drag stress, and retarded the flow velocity, reducing the transport rate of suspended sediment. [ABSTRACT FROM AUTHOR]

• The mixing layer dynamics at the Negro/Solimões confluence was studied using the dimensionless stability number. • The role of the discharge ratio between the merging rivers on the location of the tilted mixing interface was identified. • The effect on mixing of differences in velocity/density, friction and change in channel width was studied using a timescales analysis. Confluences are common components of all riverine systems, and characterized by converging streamlines and potential mixing of separate flows. The fluid dynamics of confluences possess a highly complex structure with several common types of flow features observed. An investigation was carried out in both low and relatively high flow conditions at the confluence of the Negro and Solimões Rivers, Brazil, which ranks among the largest river junctions on Earth. During this field research, acoustic Doppler velocity profiling (ADCP) and water quality sampling were applied to investigate hydrodynamics, sediment transport and mixing characteristics at this confluence. It was found that the location and the width of the mixing interface were closely related to changes of the discharge ratio between the tributaries due to both seasonal and annual variations. Second, a timescales analysis was applied to comparatively identify the contribution to mixing at the Negro/Solimões confluence of four processes: difference in (1) velocity and (2) density between the rivers, (3) bed friction, including form drag, and (4) change in channel width. The analysis demonstrated that adjustments of confluence hydrodynamics and morphodynamics can modify the relative importance of each contribution. Immediately downstream of the junction the effects of differences in velocity and density were comparable, while farther downstream the latter was predominant and the role of bed friction was significant. At the end, this study suggests that mixing at the Negro/Solimões confluence can be explained as a combination of the four hydrologic and morphologic processes. [ABSTRACT FROM AUTHOR]

Many estuaries present natural harbor conditions with relatively calm and shallow waters that provide a connection between the ocean and continental waterways. The increase in the demand for goods by the constant growing of the world population has forced estuaries to be altered by human activities, such as dredging, in order to maintain a safe navigation system. The development of sophisticated morphological and hydrodynamic models opened a new perspective of assisting dredging operations inside different estuaries. Thus, the aim of this study is to apply a hydromorphodynamic model to simulate the bed evolution of the Patos Lagoon estuary, southern Brazil. The results of the simulation were applied in a dredge operation model to simulate dredging inside the waterway of the Rio Grande harbor, located inside the Patos Lagoon estuary. The salinity and current velocities inside the estuary were well represented by the model simulations. An annual mean discharge of 3 407 ms3 s−1 was calculated for the lagoon for the year 2004. The morphodynamic model successfully represented the silted and eroded scenarios for the estuarine channel. The dredge operation model results affirm that dredging of the channel causes significant variations in estuarine physical parameters such as salinity, current velocity and suspended sediment concentration. The bed evolution results indicate that a fast siltation of the channel occurs right after dredging stops, stabilizing the variations after a 60-day period. • Silted areas were identified by the morphodynamic model. • Dredge polygons were defined over the silted areas. • The dredging model was applied on the dredge sectors defined. • Current velocities presented considerable reduction on a dredged scenario. • The results indicate intense siltation of the dredged areas until 60 days after the end of the operations. [ABSTRACT FROM AUTHOR]