Confluence Region Research Articles

Tailoring macrostructure and texture in bobbin-tool friction stir weld via manipulation of deformation behaviour of plasticised metal during welding enabled by modifying tool profile

Bobbin-tool friction stir welding is a variant of friction stir welding with high process flexibility that has garnered considerable attention from the community. The reliability of the weld is sensitive to the macrostructure and texture of the stir zone, which must be carefully tailored. The macrostructure of the stir zone is governed by the refill behaviour of the plasticised metal associated with the bobbin-tool; refill occurs preferentially near the upper and lower shoulders, creating a triangular gap at the mid-thickness level that is subsequently closed by the confluence of the layered refilling plasticised metal from the upper and lower levels. Volumetric defects easily develop in this triangular confluence region because the symmetrical confluence of the layered refilling metal has the inherent characteristic of limited intermixing. The visual appearance of the triangular region, featuring limited voiding, was improved by tapering the stirring probe. This modification reduced the volume of displaced metal, leaving a smaller gap to be refilled during welding. Concurrently, the symmetrical confluence pattern was altered to an asymmetrical pattern, which enhanced the intermixing of the layered refilling metal from the upper and lower levels and promoted gap closure. For defect-free welds, macroscopic deformation inhomogeneity under tensile loading was observed due to the presence of a strong basal texture in the stir zone. The texture was scattered by disrupting the regular shear deformation pattern in the stir zone, which was achieved by modifying the tool profile. The activation capability of both basal slip and extension twinning among various local regions across the stir zone was substantially reduced through texture tailoring, resulting in more homogeneous tensile deformation. Consequently, elongation was enhanced by 66 %. This study highlights an easy-to-perform and generic strategy that can improve the quality of bobbin-tool friction stir welds.

Spatiotemporal variations in vertical profiles of Fukushima-derived 137Cs in the Kuroshio-Oyashio confluence region from 2011 to 2018: Implications for local water mass dynamics and basin-scale circulations

Tracking the processes of the spread of Fukushima-derived 137Cs (137CsF) contributes to a better understanding of North Pacific water dynamics. In this study, the vertical distributions of 137Cs and 90Sr in the Kuroshio-Oyashio confluence region were investigated in May 2018, and 137CsF was separated from the background 137Cs by exploiting the constant global fallout 137Cs/90Sr ratio. To the north of 35°N, 137CsF peaked in the upper 100 m layer, whereas in and just south of the Kuroshio Extension (KE), 137CsF exhibited subsurface peaks at depths of 300–500 m. The T/S diagram indicated that the 137CsF maxima were distributed mainly within the range of lighter central mode water (L-CMW) during May 2018, even in and just south of the KE. We found that anticyclonic (cyclonic) eddies can promote (prevent) the intrusion of 137CsF into the ocean interior. In addition, the high activity of regional anticyclonic eddies in the upstream KE resulted in the modification of 137CsF-rich subtropical mode water (STMW) to L-CMW. Temporal changes in the 137CsF vertical profiles and inventories revealed that 137CsF in transitional and subarctic regions has increased since July 2014, implying the existence of additional sources of 137CsF after July 2014, whereas 137CsF in and just south of the KE has remained constant since July 2014, indicating that the 137CsF entrained by STMW has recirculated in the western subtropical gyre. The comparison between surface 137CsF concentrations in transitional and subarctic regions and those observed in Oyashio waters during 2018 did not support the return of 137CsF to our study area via the western or whole subarctic gyre by May 2018. In contrast, the sea surface height distributions from 2016 to 2017 provide clear evidence that the warm-core rings and quasistationary Isoguchi western jet generated from the Kuroshio Current and KE intruded into the transitional region and even into the subarctic region. Therefore, we concluded that a portion of the 137CsF that subducted into the subtropical western North Pacific during 2011–2012 have entered the transition zone and even the subarctic region since 2016. These results not only enhance our understanding of the protracted spread and fate of 137CsF in the North Pacific but also provide important insights into North Pacific water mass circulation and mixing patterns.

Satellite and in situ measurements of water vapour in the Brazil‐Malvinas Confluence region

AbstractThis decade‐long study from the INTERCONF programme addresses the data gap on ocean dynamics in the Southern Hemisphere. Focusing on the Brazil‐Malvinas Confluence (BMC), we investigated the effect of temperature differences between the warm Brazil Current (BC) and the cold Malvinas Current (MC) on water vapour in the marine atmospheric boundary layer (MABL). Our results show a clear distinction: warmer BMC waters have 32% more water vapour (2 kg·m−2 on average) compared to the MC. This highlights the direct link between ocean temperatures and atmospheric processes. Analysis of radiosonde data alongside satellite measurements showed better agreement over cooler waters with lower water vapour, leading to lower variability. This suggests less atmospheric turbulence and improved data compatibility, especially for satellite retrievals such as AIRS. Comparisons between reanalysis data (CFSR), satellite sounders (AIRS) and radiosondes (RS) showed consistent air temperature profiles, with average errors within the 10% threshold for satellite measurements. While capturing humidity variations remains a challenge, especially at high concentrations (indicated by higher mean squared error values), our study highlights the reliability of satellite data, particularly over the cold BMC region. This research highlights the importance of studying the interactions between ocean fronts and atmospheric phenomena for a complete picture of Southern Hemisphere ocean dynamics. It offers valuable insights for scientists across disciplines, providing a broad perspective on the results and their significance in different contexts.

NATURAL COURSE OF AGE-RELATED RETENTIONAL AVASCULAR PIGMENT EPITHELIAL DETACHMENT: Support For The Lipid Barrier Hypothesis.

Retentional pigment epithelial detachment (PED) associated with age-related scattered hypofluorescent spots on late-phase indocyanine green angiography (ASHS-LIA) is hypothesized to be caused by Bruch membrane's lipid barrier. This study aimed to report the natural course of retentional PED and evaluate the relationship between retentional PED evolution and ASHS-LIA. Patients with treatment-naïve retentional PED were enrolled and observed every 3 months for at least 12 months. Treatment was not performed except for secondary macular neovascularization. In 55 studied eyes with a median follow-up of 18.0 (range: 12-36) months, 87.3% (48/55) of the retentional PEDs persisted, 7.3% (4/55) resolved, and 5.5% (3/55) progressed to polypoidal choroidal vasculopathy. The mean PED area significantly increased during the follow-up ( P < 0.001) and with the ASHS-LIA grade at each follow-up point (all P <0.05), especially during the first 6 months before approaching the edge of confluent ASHS-LIA. Persistent PEDs were mostly stable (52.1%) or enlarged (45.8%) but reduced in only 1 case (2.1%) because of retinal pigment epithelium microrip at the edge of PED. The persistent PEDs were all within the ASHS-LIA region, especially the macular confluence region. The resolved PEDs all had grade 1 ASHS-LIA and resolved after gradual expansion of PED beyond the confluent ASHS-LIA region. Pigment epithelial detachments that progressed to macular neovascularization all had confluent grade 2 or 3 ASHS-LIA. Retinal pigment epithelium microrips or apertures within PED did not affect the progression of the PED. The natural course of retentional PED is closely related to the features of ASHS-LIA and supports its lipid-barrier hypothesis.

Studies on the Venation Pattern in Ferns I. Anastomoses and, other Features in &lt;i&gt;Adiantum incisum&lt;/i&gt; forsk. (A. Caudatum Sensu Bedd., Non Linn. Pro Parte)

Anastomoses, though infrequent, occur in the dichotomous venation of Adiantum incisum Forsk. Generally more than one anastomosis does not occur in 2 single leaflet, but in three leaflets there were two anastomoses each. The anastomoses are classified into seven types. In Type I two branches of a single vein-dichotomy unite and the branches separate immediately after fusion. Type II anastomosis is similar to Type I but the branches do not separate after confluence. In Type III adjacent branches of two vein-dichotomies unite and separate after a short area of confluence. In Type IV two closely adjacent branches of two vein-dichotomies ale interconnected by a very short transverse commissural vein. Type V is similar to Type IV but the commissural vein is obliquely oriented. Type VI is characterized by the formation of an areole by the union of an unbranched arcuate vein and one of the branches of its sister vein lying above it. The region of confluence is very short and the branches again separate. Type VII is similar to Type VI but the branches do not divide after fusion. Vein approximations have been observed in addition to blind vein-endings, sinus vein-dichotomy, detached vein and marginal blind vein-dichotomy. It has been considered that the separation of Hewurdia to a distinct genus is unjustified. Certain phylogenetic aspects of vein-approximations and anastomoses are discussed.

Experimental construction of eddy real-time structure based on gradient-dependent OI in the Kuroshio-Oyashio confluence region

The internal structures of mesoscale eddies are variable due to different generation mechanism, spatiotemporal scale, and movement characteristics. Based on the principle of data assimilation, this study provided a new approach for constructing the eddy real-time internal structure using the gradient-dependent optimal interpolation (OI) method. Three eddy cases with different types and locations were selected to validate the construction results. The reliability of construction was evaluated by satellite observation, in-situ comparisons, and contrast with the numerical output. The results showed that the real-time geostrophic current characters were basically consistent with the surface and deep current (observed by satellite and acoustic doppler current profiler, ADCP). The density features exhibited by constructed results (eddy centers, mean radii, and variation tendency) were similar to the expendable conductivity-temperature-depth (XCTD) survey data and numerical output. Compared to the composite structure, the real-time structures represented more small or mesoscale fluctuations. During eddy cases evolution, the mean radii at the same depth first increased and then decreased. The horizontal scale, influence depth, and internal stability of an anticyclonic eddy with low-latitude were more powerful than the other two eddy cases owing to the domination of warm water in the Kuroshio extension region. The results indicated that the gradient-dependent OI was a hopeful technique for representing the real-time internal features during eddy evolution.

A Global Assessment of Eddy‐Induced Salinity Anomalies and Salt Transport by Eddy Movement

AbstractEddy‐induced salt transport is essential in maintaining the oceanic salinity balance and global climate. However, the paucity of in situ measurements poses challenges in obtaining the spatial structure of the eddy salt transport globally. Here, we conduct a global estimation of eddy‐induced salinity anomalies and salt transport by eddy movement using 2 million historical hydrographic profile measurements and satellite‐based eddy observations spanning from 1993 to 2019. The results demonstrate rich geographic and vertical variability in the salinity anomalies induced by eddies across the global ocean. Vertical sign switches of salinity anomalies within eddies are observed in the tropical and subtropical oceans, as well as in the Kuroshio Extension region. Additionally, meridional sign switches of eddy‐induced salinity anomalies are observed in the Antarctic Circumpolar Current region. By integrating eddy occurrence probability, we refine the methodology for estimating eddy‐induced salt transport, and provide global spatial patterns of both meridional and zonal salt transport induced by eddy movement at each 2° × 2° grid. Significant salt transport by meridional eddy movement is observed in the mid‐latitude oceans, with the peak zonal‐depth integrated salt transport reaching 106 kg·s−1 in the mid‐latitudes of the southern hemisphere. Specifically, the Brazil‐Malvinas Confluence region is identified as a highly efficient pathway for meridional salt transport, with a magnitude of −1.28 × 106 kg·s−1, significantly surpassing other regions in the global ocean. These findings may provide important references for the understanding and simulation of global oceanic salinity transport.

Decadal mapping of flood inundation and damage assessment in the confluence region of Rivers Niger and Benue using multi-sensor data and Google Earth Engine

Abstract Climate change has made weather patterns more extreme, causing floods in Nigeria. Flooding is the most frequent and serious natural hazard in the confluence region of Rivers Niger and Benue, impacting lives, agriculture, and socio-economic activities significantly. Advancements in satellite technology and computational capabilities have enhanced rapid information about flood extent for monitoring, mitigation, and planning. However, there is a dearth of information based on time series analysis of flood inundation and monitoring in the confluence region. In this study, Sentinel-1 Synthetic Aperture Radar, Sentinel-2, and Landsat-7 and Landsat-8 data were used to extract flood inundation for 10 years (2012–2022) in the confluence region of Rivers Niger and Benue. Flood extent/surface waterbodies were extracted using the Google Earth Engine platform, modified normalized difference water index, and normalized difference water index methods. The findings revealed that within 10 years, four significant flooding incidents occurred in 2012, 2018, 2020, and 2022, inundating 60.57, 48.24, 39.98, and 84.39 km2 of the area, respectively. The study underscores the need for the establishment of a decision support system for monitoring flood inundation and providing decision-makers necessary information for flood disaster preparedness, mitigation, and adaptation.

Application of data-driven mixing parameterization scheme in a regional ocean model

In this study, based on the data-driven parameterization proposed in previous studies, we implemented a data-driven vertical turbulence parameterization scheme (backpropagation neural network, BPNN) into a regional ocean model and compared the simulation results with those obtained using the traditional physics-driven scheme (K-profile parameterization, KPP). The Kuroshio-Oyashio Confluence Region (KOCR) with rich ocean dynamics was selected as the study region. Comparisons of modeled temperature, salinity, and velocity outputs show that the two parameterization schemes produce similar spatial and temporal distribution characteristics. For the sea temperature, the maximum difference appeared at the subsurface layer (3.6 °C) while the maximum mean difference appeared at the surface layer (0.1 °C). Overall, sea temperature in the surface layer simulated by the model adopting the BPNN parameterization scheme was warmer. For the salinity, the maximum difference (0.28 psu) and maximum mean difference (1 × 10−3 psu) appeared in the subsurface layer. In the surface layer, when the model adopting BPNN parameterization scheme overestimated sea temperature compared to the KPP scheme, the result was usually accompanied by overestimated salinity. In the bottom layer, when the model adopting the BPNN parameterization scheme simulated temperature overestimation, the result corresponded to underestimated salinity. For the velocity, the maximum difference (0.31 m/s) and maximum mean difference (-3 × 10−3 m/s) between the two parameterization schemes appeared in the surface layer, and the high values of velocity difference generally occurred in sea areas with energetic dynamic processes. The KPP scheme and the model adopting BPNN parameterization produced similar mixed layer depth (MLD) spatial distribution and ocean fronts spatial distribution, but the latter parameterization scheme simulated an overall shallower mixed layer. For the ocean fronts, the differences between the two parameterization schemes (O∼10−5) is smaller than the intensity of the fronts (O∼10−4). This study presents a new attempt to apply the data-driven parameterization scheme in ocean numerical models.

Fires in the valley? (Abridged version)

The many combustion structures for heating stones recorded in the Seine-Eure confluence region (Normandy) are used here as a guiding thread in a study of the Neolithic occupations of riverbanks and valley bottoms. In these settings, preventive archaeology has revealed sites with features unknown in settlements, over a wide spatial and temporal scale. Most of the data presented here come from the excavations at Louviers “Avenue Winston Churchill” and Alizay “Le Postel”. These two sites comprise hundreds of stone-heating structures, also found in a wide variety of contexts in north-western France: settlements, riverbanks, coastlines, megaliths, etc. Data from these structures are often considered to be of limited value (variable conservation, few or no artefacts). However, the study of the different components of these structures reveals forms of Neolithic social organisation that are rare or unknown in settlements. These environments provide a glimpse of an entire section of the Neolithic technical system that developed at the crossroads of a global territorial management macroeconomic model, and a complex interplay of social and environmental interactions.

Application of Gradient-Dependent Optimal Interpolation in Fishery Analysis of Neon Flying Squid (Ommastrephes bartramii) in the Kuroshio–Oyashio Confluence Region

A key issue in fishery forecasting is the collection of high-precision subsurface environmental data. A data assimilation method, named gradient-dependent optimal interpolation, was used to construct the near-real-time vertical temperature and salinity structure of a squid fishery ground based on Argo observations. The results were verified by truth-finding comparisons and applied to analyze the relationship between neon flying squid and the subsurface environment in the Kuroshio–Oyashio Confluence Region. The temperature and salinity differences between the constructed results and survey data were less than ±0.5 °C and ±0.02, respectively. Most of the relative analysis errors were less than the observational errors. Statistical analysis revealed that the most suitable temperature for squid was 18–24 °C at the near-surface (&lt;5 m), although the squid can endure a temperature range from 11 to 12 °C at a depth of 300 m. There was an obvious thermocline in the fishery ground, with a thermocline depth of 65 m and a mean strength of approximately 0.10 °C/m. The regressive relationship between vertical temperature (thermocline parameters) and squid catch per unit effort (CPUE) followed the exponential (Gaussian) function. The most suitable salinity was 33.0–34.2 at depths shallower than 300 m.

Water mass mixing contributes dynamics of dissolved organic matter in Kuroshio-Oyashio confluence region

The Kuroshio-Oyashio confluence region (K/O region) plays a significant role in the global carbon cycle and climate change. In this study, we examined the concentration and composition of dissolved organic matter (DOM) in water samples collected from depths of 0 to 1000 meters between 2019 and 2021. The concentration of dissolved organic carbon (DOC) ranged from 30.54 to 113.21 μmol L-1, with higher concentrations observed in surface waters. The biological index (BIX) decreases with increasing depth, indicating decreasing in-situ production of plankton downwards. Additionally, the humification index (HIX) increased with depth, suggesting the transformation of labile to refractory DOC by bacteria. Using parallel factor analysis, we identified two humic-like (C1, C3) and one protein-like (C2) fluorescent components in 467 water samples. Water samples collected in 2020 exhibited significantly higher specific ultraviolet absorbance at 254 nm (SUVA254) (0.5 ± 0.2 L mg-1 m-1) and higher intensities of C1 (8.2 ± 2.69 *10-3 R.U.) and C3 (9.22 ± 4.39 *10-3 R.U.) compared to samples from 2019 and 2021. We found that water temperature had a positive correlation with C2 intensity (r = 0.33; p&amp;lt; 0.01), but negative correlations with C1 (r = −0.72; p&amp;lt; 0.01) and C3 intensity (r = −0.55; p&amp;lt; 0.01). Comparison of measured and theoretical values using a conservative physical mixing model revealed active biogeochemical processes of DOM during water mixing of the Kuroshio, Oyashio, and North Pacific Intermediate Water that change concentration and composition of DOM. Since the hydrology in the K/O region is sensitive for the ongoing climate warming, further investigation is needed to understand water mass mixing and associated DOM dynamics.

Stability mechanisms and air temperature advection on the marine atmospheric boundary layer modulation at the southwestern Atlantic Ocean

AbstractHydrostatic adjustment and vertical mixing are the two main mechanisms used to describe the stability of the marine atmospheric boundary layer (MABL) in oceanic regions with intense horizontal temperature gradients. To analyze the occurrence of these mechanisms, we performed simulations using an active coupled regional ocean–atmosphere numerical model in the southwestern Atlantic Ocean (SWA) region in October 2014 in the presence of an atmospheric frontal system. A novel in‐situ dataset was sampled by radiosondes in the Brazil–Malvinas Confluence (BMC) region and used with the model dataset. The vertical mixing mechanism and a prefrontal warm‐air temperature advection were identified, which modulated the shallower and more stable MABL. The hydrostatic adjustment mechanism was not evident because of the near‐surface wind convergence field modification caused by the large‐scale atmospheric system observed in our experiment. The coupled model simulation presented good agreement compared to in‐situ and satellite data. This contribution to the knowledge of the ocean–atmosphere interaction processes at the SWA reinforced that coupled models can be a helpful tool to investigate the air–sea interactions and physical mechanisms that explain MABL stability.

Effects of discharge-to-submergence ratio on evolution of air-core vortex

An air-core vortex is generated in a tidal power station when the discharge increases or the submergence decreases at the intake. To better understand the complex evolution of the air-core vortex, we conduct high-fidelity coupled level-set and volume-of-fluid and wall-modeled large-eddy simulations for various ratios of discharge and submergence. We characterize the air-core vortex evolution process into two stages: the inception stage and the propagation stage. Our results show that the streamwise and spanwise velocity fluctuations exhibit similar distributions and temporal evolutions and are responsible for generating asymmetrical flow transitioned from a completely symmetrical pattern in the inception stage. The turbulence quadrant decomposition analysis in the confluence region quantifies the velocity fluctuation signal and Reynolds shear stress distribution. Under a specific Reynolds shear stress distribution, eddies converge and evolve into a main vortex. We introduce a vortex burst index to quantitatively characterize the contribution of the Reynolds shear stress to the main vortex evolution. The vortex burst index is positively correlated with the discharge-to-submergence ratio. In the propagation stage, the enstrophy stretching mechanism dominates the air-vortex evolution. The tilting terms nearly cancel each other because of the similar tangential velocity distribution in the axial direction. The results show that the increase in the discharge-to-submergence ratio accelerates the formation of the air-core vortex, owing to the increase in the vertical velocity gradient and the enhancement of the stretching effect.

Evaluation of Water Quality at the Confluence Region of Diyala and Tigris Rivers Based on the Weighted Arithmetic Method

This study is conducted to assess the water quality index (WQI) of the Diyala and Tigris River confluence region south of Baghdad (Al-Tuwaitha), based on the Weighted Arithmetic method. Sixteen samples of water were collected from different location in the region through two periods 5/11/2021 and 13/3/2022. Water quality parameters such as (PH, EC, TDS, TH, Ca, Mg, Cl, Turbidity, ALK, SO4, HCO3, Na, and K) were used to evaluate WQI in the study area. The final results showed that the water was not suitable for drinking due to the high concentration of water quality parameters. In the 5 November 2021, the water quality in the study area was classified into (good, poor, very poor, and polluted) where the percentages of the above classes were 4%, 6%, 39%, and 51% respectively, while the percentages for the season 13thMarch 2022 were 1%, 41%, and 58% with very poor, polluted, and very polluted class, respectively. The water was not suitable for drinking due to the high concentration of water quality parameters in most locations in the study area. There are many sources of pollution in the region that dump their harmful waste into the river, which led to increase the concentrations of water quality parameters in most locations of study area.

Iron Age sites in northern Botswana’s Okavango Delta 3: Lotshitshi, a Later Stone Age/Bambata/Recent site on the Delta margin

ABSTRACT Lotshitshi is a small site on the edge of the Thamalakane River floodplain on the southern margin of the Okavango Delta, Botswana. A component with Later Stone Age lithic artefacts radiocarbon-dated to the second/third millennia BC is overlain by a component with the same kind of stone tools, but with the addition of Bambata pottery and domestic cattle radiocarbon-dated to the earlier decades of the first century AD. A component with Recent pottery is at the top of this sequence. Although modest in size and content, Lotshitshi adds valuable details to our knowledge of Bambata pottery-making peoples with cattle and provides additional evidence for the movement of peoples during this time from the Chobe-Zambezi confluence region to western Botswana, thus supplementing efforts to understand Early Iron Age population dynamics in southern Africa as a whole.

フローフロント合流部の樹脂流動挙動による繊維配向メカニズムの検証

フローフロント合流部の樹脂流動挙動による繊維配向メカニズムの検証

Anterior superior pancreaticoduodenal artery pseudoaneurysm after distal pancreatectomy with en bloc celiac axis resection successfully treated with balloon-assisted coil embolization

Bleeding is a fatal complication after pancreatectomy. Although coil embolization is a widely accepted treatment option, ischemia of the remaining organs should be prevented. This study reports the successful treatment of intra-abdominal hemorrhage following distal pancreatectomy with en bloc celiac axis resection (DP-CAR) using balloon-assisted coil embolization (BACE). A 59-year-old man was diagnosed with locally advanced pancreatic cancer. The tumor involves the common hepatic artery, splenic artery, and celiac artery. After four cycles of treatment with gemcitabine/nab-paclitaxel, the soft-density masses, surrounding the artery, shrunk. DP-CAR and R0 resections were performed. A minor postoperative pancreatic fistula occurred. Six months postoperatively, the computed tomography showed delayed asymptomatic bleeding from an anterior superior pancreaticoduodenal artery (ASPDA) pseudoaneurysm located near the gastroduodenal artery confluence. BACE was performed by placing a microballoon catheter in the region of confluence of the ASPDA and posterior superior pancreaticoduodenal artery (PSPDA) to prevent coil migration. After inserting the microballoon catheter, coil embolization was performed in the ASPDA. Hepatic blood flow was maintained from the PSPDA. BACE is a useful technique to preserve blood flow to the remnant organs when performing coil embolization for bleeding following a distal pancreatectomy, especially following a DP-CAR.

Seasonal modulation of mixed-layer temperature anomaly in Kuroshio–Oyashio confluence region by bimodal Kuroshio extension

Seasonal modulation of mixed-layer temperature anomaly in Kuroshio–Oyashio confluence region by bimodal Kuroshio extension

Riverbed morphology and hydrodynamics in the confluence of complex mega rivers - A study in the Branco and Negro rivers, Amazon basin

The study of the morphology and hydrodynamics of large rivers has advanced in recent decades. Nonetheless, there are a few studies with surveyed data carried out at the confluences of the mega rivers (Q > 17,000 m³s−1), especially those from the Amazon basin. The Negro River is the main river in the northwestern Amazon and is considered the sixth-largest in the world in terms of water discharge, has a complex multichannel pattern and a peculiar geological configuration. This article aims at analyzing the bed morphology and hydrological processes in the confluence region between the Branco and Negro rivers. Field surveys with echo-sounding and Acoustic Doppler Current Profiler were carried out over an area of 31 km2 during the low water period of 2021 year. The results of this survey made it possible to identify the main morphological characteristics of the riverbed in the confluence hydrodynamic zone between Branco and Negro River, as well as the dynamics of the velocity, streamflow, and transport of suspended sediment of these important northwestern Amazonian rivers. Analysis of bed morphology and their neotectonic control are also discussed. These results presented in this work contribute to expanding the knowledge about the confluence of large tropical rivers with significant bed discordance and differences in the density of flows.