River Course Research Articles

Delayed response of the coastal sedimentary record to the southward shift of the Huanghe (Yellow River) course during AD1128–1855

The sediment source-to-sink process is an important topic in marine sedimentology. However, how sedimentary signals evolve along source-to-sink path remains less clear. This study focuses on the southward shift of the Huanghe River course between AD 1128 and 1855, and the manifestation and variation of sedimentary signals in a natural diffusion system were investigated through sedimentological analysis of three spatially adjacent regions, the abandoned Huanghe Delta, the central coast of Jiangsu, and the Changjiang Delta. Laboratory analyses including Optically Stimulated Luminescence (OSL), geochemical element analysis, and grain size analysis, were conducted. The results show that sedimentary signals manifest in various forms, primarily manifested in two ways: grain size refinement and sedimentation rate acceleration. The fining of grain size is most pronounced in the abandoned Huanghe delta, followed by the central coast of Jiangsu, and is least pronounced in the Changjiang subaqueous delta. The response of the coastal system to the event was delayed by approximately 0–100, 100–300, and 300–500 years for the abandoned Huanghe Delta, the central coast of Jiangsu, and the Changjiang River Delta, respectively. These findings indicate that sediment transport processes exhibit sedimentary signal attenuation and response lag. This study not only highlights the variation along the source-sink path of coastal sedimentary signals but also illuminates the sedimentary record of drastic changes in sediment flux, which will help study the source-to-sink process given the variable changes in sedimentary fluxes.

Identification of Subsurface Geological Structures from Gravity Data by Modelling Techniques in Kalak-Bardarash Area, West of Erbil City Iraqi Kurdistan Region

A quantitative interpretation of gravity anomalies in the Kalak-Bardarash area, west of Erbil City in the Kurdistan Region of Iraq, was performed using two-dimensional analysis techniques. These techniques modeled geological structures identified from a previously created Bouguer anomaly map of the area. Five profiles were selected for the analysis, resulting in eight models constructed for both deep and shallow-seated rock units. The deep-seated rocks are represented by the basement rocks, with models constructed in the NNE-SSW, WNW-ESE, and NW-SE directions using the regional anomaly component. The depth of the basement rocks ranges from five to nine kilometers and is affected by numerous faults in the form of graben and step structures. The basement rock surface slopes towards the NE and ESE at a gradient of 110 m/km. The shallow-seated rocks are represented by the sedimentary cover, which includes Neogene, Paleogene, and Cretaceous-aged groups of formations. The residual component of the anomalies of the five profiles were interpreted. Three profiles, oriented NNE-SSW and nearly perpendicular to the main anticlinal structure, revealed that the Bardarash anticline is influenced by two faults striking both limbs and extending in the NNW-SSE direction, with an estimated throw of 200 meters on each side. The southern fault is believed to extend down to the basement rocks. The other two profiles, oriented NW-SE and nearly perpendicular to the Zab River, indicated the presence of two additional faults with a throw of approximately 600 meters in the deeper parts striking the basement rocks, dipping towards the southeast. The throw of these faults gradually decreases upward in the sedimentary cover, reaching about 200 meters. These faults directly influence the course of the Zab River, directing it in a NE-SW direction at this district.

Geomorphological Changes of the Terrestrial Features of the Euphrates River between the Cities of Al-Kifl and Al-Mishkhab Using Geographic Information Systems (GIS)

The study area occupies part of the southwestern part of the sedimentary plain from the city of Al-Kifl and Najaf to the city of Al-Mashkhab, which is predominantly characterized by extraversion, which made the study area a low topographical variation. However, this variation contributed significantly to determining the geomorphological forms of the Euphrates River course as well as the direction of the course, which was consistent with the direction of the surface slope from the northwest towards the southeast. Thus, the natural characteristics of the study area vary from geological structure, surface, climate, soil and natural vegetation. When taking into account the true longitudinal extension of the Euphrates River course of (59) km, we find that these characteristics have a prominent impact in causing geomorphological changes in the study area.

1D-2D hydrodynamic and sediment transport modelling using MIKE models

A comprehensive modeling framework utilizing hydrodynamic and sediment transport models (MIKE Hydro River, MIKE 21 FM, MIKE 21C) was applied to the 33.57 km stretch of the Banshadhara River from Banshadhara bridge, Gunupur to Kashinagar town. Daily discharge, water levels, and sediment data from 2013 to 2022 of Gunupur and Kashinagar gauge stations was used as model input, and calibration–validation of models. Additionally, satellite remote sensing data used for determined Manning’s roughness (n) values as well compared the model outputs. Calibration procedures ensured high accuracy, with MIKE Hydro River achieving 98.3% agreement between observed and simulated water levels. 1D sediment transport model showing significant variability in total bed load values ranging from 0.3 to 3.83 m^3/s. The Wilcock & Crowe gravel bed load formula accurately predicted bed load transport within the expected magnitude, albeit tending to overestimate transport, indicative of supply-limited conditions. 2D MIKE 21 FM simulations highlighted flow dynamics, with rapid flood arrival at Kashinagar and varying current speeds along the river, especially at bends. MIKE 21C, focused on the central portion, indicated erosion processes at river bends with high discharge. Sediment transport model accuracy was approximately 86.7%, capturing general trends despite occasional discrepancies. Over a 10-year simulation, erosion trends and potential river course shifting were observed, particularly near bends. The analysis provides valuable insights for river management, flood risk mitigation, water resource management, infrastructure planning, and environmental preservation in the Banshadhara River basin and similar environments.

Hotter Temperatures Reduce the Diversity and Alter the Composition of Woody Plants in an Amazonian Forest.

Rapid warming and high temperatures are an immediate threat to global ecosystems, but the threat may be especially pronounced in the tropics. Although low-latitude tree species are widely predicted to be vulnerable to warming, information about how tropical tree diversity and community composition respond to elevated temperatures remains sparse. Here, we study long-term responses of tree diversity and composition to increased soil and air temperatures at the Boiling River-an exceptional and unique "natural warming experiment" in the central Peruvian Amazon. Along the Boiling River's course, geothermally heated water joins the river, gradually increasing water temperature and subsequently warming the surrounding forest. In the riparian forests along the Boiling River, mean annual and maximum air temperatures span gradients of 4°C and 11°C, respectively, over extremely short distances (< 1 km), with the hottest temperatures matching those predicted for much of the Amazon under future global warming scenarios. Using a new network of 70 woody plant inventory plots situated along the Boiling River's thermal gradient, we observed a ca. 11% decline in tree α-diversity per 1°C increase in mean annual temperature. We also found that the tree communities growing under elevated temperatures were generally more thermophilic (i.e., included greater relative abundances of species from hotter parts of the Amazon) than the communities in cooler parts of the gradient. Based on patterns at the Boiling River, we hypothesize that global warming will lead to dramatic shifts in tree diversity and composition in the lowland Amazon, including local extinctions and biotic attrition.

32 years of changes in river paths and coastal landscape in Bangladesh, Bengal Basin

This study examines the geomorphological changes and environmental impacts on the coastline and the evolution of major river systems in Bangladesh over the past 32 years using remote sensing and GIS analyses. The central coastal area, characterized by fine sediments, has experienced significant land erosion due to the dynamics of the Meghna Estuary and its depositional patterns. In contrast, the southwestern Sundarbans Forest coast has remained relatively stable, aided by mangrove root stabilization despite anthropogenic threats. Channel migration analysis revealed the Brahmaputra River’s persistent braided configuration, while its tributaries, Teesta and Dharla, increased meandering nature due to reduced water availability and human interventions. The Ganges-Padma system displayed a shift towards a more sinuous channel pattern driven by reduced water discharge due to the Farakka Barrage construction in the upstream and a minor decrease in precipitation. The Upper Meghna River maintained moderate sinuosity with stable anastomosed patterns, whereas the lower Meghna River’s convergence with the Jamuna and Padma Rivers increased its susceptibility to erosion. These findings highlight the interplay of natural processes and human activities in shaping the coastal and fluvial landscapes of Bangladesh and the Bengal Basin, emphasizing the need for sustainable land-use practices and adaptive management strategies to mitigate future risks associated with sea-level rise and river course changes.

Riparian vegetation entraps macroplastics along the entire river course: Implications for eco-safety activities and mitigation strategies

Macroplastic litter causes detrimental effects on freshwater biota affecting human health. Despite the significant role of rivers in transporting plastic waste, most plastics remain in fluvial ecosystems, accumulating in infrastructure, river sediment, and (riverbank) vegetated areas. However, the entrapment of plastics by riparian vegetation was overlooked, particularly in upper and middle river courses. For the first time, we aimed to quantify the entrapment of plastics by riparian vegetation along the entire river course. Sampling riparian areas in the upper, middle, and lower river courses in central Italy, we found 1548 macrolitter items, with vegetation entrapping 93.9% of total litter. Riverbank and riparian plastics acted as long-term indicators of river plastics. We emphasized the trapping efficiency at the species level highlighting that the best plastic trapper species were trees, shrubs and reeds (Populus spp., Salix spp., Rubus ulmifolius, Phragmites australis, and Ficus carica), blocking 85.4% of the total macrolitter entrapped by plants. Plastic pieces, bags, bandages, sanitary items, and packaging were among the most trapped types. Furthermore, vegetation in the lower river course exhibited greater plastic entrapment compared to the upper and middle courses, following the fact that all the river courses contribute to plastic pollution. Recognizing the potential of riparian vegetation as a valuable ecosystem service in trapping macroplastics, further research should explore the characteristics and structures of riparian communities involved in this process. By developing eco-safe practices and mitigation strategies based on these findings, we might contribute significantly to managing, conserving, and restoring riverine ecosystems.

Metal tolerance of Río Tinto fungi.

Southwest Spain's Río Tinto is a stressful acidic microbial habitat with a noticeably high concentration of toxic heavy metals. Nevertheless, it has an unexpected degree of eukaryotic diversity in its basin, with a high diversity of fungal saprotrophs. Although some studies on the eukaryotic diversity in Rio Tinto have been published, none of them used molecular methodologies to describe the fungal diversity and taxonomic affiliations that emerge along the river in different seasons. The aim of the present study was to isolate and describe the seasonal diversity of the fungal community in the Río Tinto basin and its correlation with the physicochemical parameters existing along the river's course. The taxonomic affiliation of 359 fungal isolates, based on the complete internal transcribed spacer DNA sequences, revealed a high degree of diversity, identifying species belonging primarily to the phylum Ascomycota, but representatives of the Basidiomycota and Mucoromycota phyla were also present. In total, 40 representative isolates along the river were evaluated for their tolerance to toxic heavy metals. Some of the isolates were able to grow in the presence of 1000 mM of Cu2+, 750 mM of As5+ and Cd2+, and 100 mM of Co2+, Ni2+, and Pb2+.

Assessing the relationship between river water pollution and the LULC composition of a basin in the Isthmus of Tehuantepec in Oaxaca, Mexico

Water pollution originating from land use and land cover (LULC) can disrupt river ecosystems, posing a threat to public health, safety, and socioeconomic sustainability. Although the interactions between terrestrial and aquatic systems have been investigated for decades, the scale at which land use practices, whether in the entire basin or separately in parts, significantly impact water quality still needs to be determined. In this research, we used multitemporal data (field measurements, Sentinel 2 images, and elevation data) to investigate how the LULC composition in the catchment area (CA) of each water pollution measurement station located in the river course of the Los Perros Basin affects water pollution indicators (WPIs). We examined whether the CAs form a sequential runoff aggregation system for certain pollutants from the highest to the lowest part of the basin. Our research applied statistical (correlation, time series analysis, and canonical correspondence analysis) and geo-visual analyses to identify relationships at the CA level between satellite-based LULC composition and WPI concentrations. We observed that pollutants such as nitrogen, phosphorus, coliforms, and water temperature form a sequential runoff aggregation system from the highest to the lowest part of the basin. We concluded that the observed decrease in natural cover and increase in built-up and agricultural cover in the upper CAs of the study basin between the study period (2016 to 2020) are related to elevated WPI values for suspended solids and coliforms, which exceeded the allowed limits on all CAs and measured dates.

Assessment and pre-assessment of compound hot and drought events over Yangtze River Basin

Abstract The severe compound hot and drought event (CHDE) in 2022 had serious impacts on water resources, agriculture, power supply, and ecosystems in the Yangtze River Basin (YRB). Have similar spatiotemporally overlapping compound events, like the one observed in 2022, occurred historically in the basin? How can we pre-assess the impacts of such potential events on subseasonal timescales? To address these, regional CHDEs in the YRB since 1961 were systematically identified and comprehensively assessed using a modified Intensity-Area-Duration (IAD) technique and hazard assessment method. Additionally, the subseasonal pre-assessment capability for CHDEs in the YRB using the China Meteorological Administration's third-generation climate model prediction system (CPSv3-S2S) was demonstrated. A total of 140 CHDEs occurred during 1961 to 2022, with the 21st century showing a remarkably high risk of such events. Among these, 2022 was the most intense year, with the event from July 26th to August 30th being unprecedented in severity. CPSv3-S2S effectively forecast this event’s occurrence within a 1-25 lead days, particularly in pre-assessing its extensively impacted area and high-hazard centers in the upper and middle reaches of the main river course. This pre-assessment method serves as a valuable reference in decision-making to anticipate and mitigate risks of hydropower supply shortages and heightened electricity demand during extremely high temperatures in the upstream area.

Exploring the impact of urban pollution on ciliate diversity along the Sapucaí River (Minas Gerais, Brazil) via DNA metabarcoding.

Protists are diverse single-celled eukaryotes found in various habitats. They exhibit a wide range of forms and functions, representing a significant portion of the eukaryotic tree of life, which also includes animals, plants, and fungi. Due to their high sensitivity to environmental changes, these organisms are widely used as biological indicators of organic pollution. We investigated the molecular diversity of ciliate protists at seven strategic points along the Sapucaí River (Itajubá, Minas Gerais State, Brazil), to assess the impact of urban pollution on the richness, abundance, and diversity indexes of these communities. For each sampling point, values of physicochemical parameters were also recorded. DNA sequences were obtained by high-throughput sequencing (HTS) and analyzed using the V4 18S-rRNA molecular marker, employing the DNA metabarcoding method. We recorded 125 ciliate taxonomic units (OTUs), with nearly 80% corresponding to the classes Spirotrichea, Oligohymenophorea, and Litostomatea. At the genus level, 54 OTUs (43.2%) were identified, spanning 28 genera. The composition of ciliates varied significantly along the river's course, from upstream to downstream of Itajubá city. Samples collected from the urban area displayed the lowest richness and diversity, corroborating the influence of the pollution gradient on these communities. The physicochemical parameters showed little variation among the samples and were not linked to the observed changes in ciliate communities, revealing that these organisms are strongly affected by environmental changes and respond more sensitively to these disturbances than physicochemical parameters, emphasizing their potential as bioindicators.

Monitoring and predicting spatio-temporal dynamics of river bankline movements: a case study for land use risk management in the lower Ganga River, India.

Changing the river course in the alluvial plain region is a common phenomenon that may have disastrous consequences. The risk of river bank erosion has increased dramatically during the last few decades. As a result, assessing the river bankline alteration is necessary. The study aims to determine the changes in the bankline in the lower Ganga River. This research presents a novel approach by using the digital shoreline analysis system (DSAS) in conjunction with geospatial data to monitor and predict long-term changes in river banks from 1965 to 2017, providing a comprehensive temporal analysis that is unprecedented in this study area. The study analyzes the bankline change along the river Ganga using DSAS using during the elapsed period. An erosion and accretion zonation was conducted based on the rate of bankline change of the river Ganga in the study area. The rate of bankline shifting was quantified using the endpoint rate (EPR) and linear regression rate (LRR) statistics computed using the DSAS model. The east bank of the Ganga in the study area experienced an average erosion of - 41.17m/year according to the LRR model. Whereas, the west bank eroded an average of - 2.32m/year between 1965 and 2017. 90.54% of the transect lines recorded erosion at the east bank and 53.69% of the transect lines at the west bank recorded erosion computed with LRR. For the assessment of the impact of river bankline change on the LULC of the study area, the future river banklines for 2027 and 2037 were forecasted. The result shows that by 2027 and 2037 about 133.24 and 147 km2 of agricultural land and 7.19 and 11.47 km2 of the built-up area may be affected by river bank erosion respectively. By extending the applications of DSAS and geospatial analytics to encompass predictive and impact assessment capabilities, this study significantly enriches the literature on the management of riverbank erosion and associated land use risks. This research provides important insights that improve river management and planning and enable the formulation of robust strategies to mitigate erosion risks on river banks.

Revealing the distribution characteristics and key driving factors of dissolved organic matter in Baiyangdian Lake inflow rivers from different seasons and sources

The river course is a transitional area connecting the source and receiving water bodies. The dissolved organic matter (DOM) in the river course is an important factor affecting the aquatic environment and ecological health. However, there are shortcomings in studying the differences and quantitative contributions of river DOM in different seasons and sources. In this study, ultraviolet-visible (UV–vis) and three-dimensional fluorescence spectra were used to characterize the optical properties, analyze the spatiotemporal changes, and establish the quantitative relationship between environmental factors and DOM in the inflow rivers of Baiyangdian Lake. The results showed that the relative DOM concentrations in summer and autumn were significantly higher than those in the other seasons (P < 0.001) and that the DOM source (SR < 1) was mainly exogenous. The fluorescence abundance of protein-like substances (C1 + C2 + C3) was the highest in spring, whereas that of humus C4 was the highest in autumn. Moreover, the inflow rivers exhibited strong autogenetic characteristics (BIX > 1) throughout the year. Self-organizing maps (SOM) indicated that the main driving factors of water quality were NO3−-N in spring, autumn, and winter and DO, pH, and chemical oxygen demand (COD) in summer. Random forest analysis showed that the fluorescent components (C1–C4) were closely related to the migration and transformation of nitrogen, and pH and nitrogen were the main predictors of each component. The Mantel test and structural equation model (SEM) showed that temperature and NO3−-N significantly influenced the DOM concentration, components, and molecular properties in different seasons. Moreover, the river source also affected the distribution mechanism of DOM in the water body. Our study comprehensively analyzed the response of DOM in inflow rivers in different seasons and water sources, providing a basis for further understanding the driving mechanisms of water quality.

Mouth bars’ development along the West Pearl River main course

River mouth bars’ formation is a key process of the delta development and river bifurcation, but details of the long-term developmental history of mouth bars and their role in the delta evolution are substantially less well documented. To characterize deltaic mouth bars’ development, this study investigated the Sixianjiao, Jun’an, Da’aosha and Denglongsha mouth bars formed successively along the main course of the West Pearl River. The detailed lithological analyses of sediment cores indicate that the mouth bar sediment is characterized by its sandy nature with mud laminations or lenses and poorly preserved foraminifera. The onset of mouth bar sedimentation is affected by water depth. The Sixianjiao and Jun’an mouth bars initiated at shallower water depth (8.0 m and 11.0 m, respectively) due to the restrictions of higher basement landforms. In an area where water is deeper, the mouth bar development would begin only with the site being elevated up to about 16.0 m water depth, such as a case in Da’aosha. The duration between their onset and end of vertical growth varies between 2000 and 2800 years, which is inversely related to their sedimentation rates between 2.7 and 5.7 mm/a, indicating the importance of sediment supply. In addition, the locations of the four mouth bars were to some extent determined by the antecedent landscapes. Finally, the ages of these four mouth bars show a chronological order from land to sea, reflecting seaward delta progradation, contrary to previous morpho-dynamical numerical model’s predictions. Our reconstruction of the West Pearl River mouth bars’ developmental history provides a new insight into the geomorphological evolution of the Pearl River delta, a special delta developed within a complex estuarine bay.

Innovative design and construction of a closure joint for inland-river immersed tunnels via dry-land construction methods: A case study of the Yuliangzhou tunnel in China

Closure joints constructed to fill the spaces between immersed tunnel elements or between the tunnel elements and adjacent cut-and-cover tunnels are crucial for the longitudinal stability of immersed tunnels and affect the overall cost and duration of tunnel construction. To avoid the obstruction of navigation and reduce the difficulty of constructing closure joints, dry-land construction methods have been widely applied to construct closure joints for inland-river immersed tunnels, in particular using procedures involving axial dry docks. However, the traditional dry-land construction method has many inherent drawbacks. For example, the construction of underwater large-scale reinforced concrete antiretreat structures involves many underwater works, complicated construction processes, long operation time spans and high costs. Based on the Yuliangzhou immersed tunnel in China, a new dry-land construction method for closure joints of inland-river immersed tunnels based on tunnel–soil interface friction was developed to address the abovementioned problems. Considering the adverse influences of back-silting sediment on tunnel–soil interface friction, large-scale laboratory and onsite shear tests were carried out to derive the interface friction coefficients between the tunnel element base slabs and prelaid pebble foundation beds. A composite concrete steel sandwich (CCSS) water-retaining system was designed and assembled to separate the water in the dry dock from the river course. A simplified analysis method based on numerical simulations for the determination of the equivalent horizontal thrust P applied to element ES caused by the dewatering of the axial dry dock was proposed. Based on horizontal antisliding stability analyses of the tunnel elements during the axial dry dock dewatering stage, equations for the key design parameters of the new dry-land construction method were established. Through examination of the static equilibrium of the tunnel elements in the tunnel longitudinal direction, temporary longitudinal displacement constraint (LDC) structures at the immersion joints were designed. Furthermore, the following key construction techniques for the new dry-land construction method were systematically designed: installation of a CCSS water-retaining system at the entrance of the axial dry dock, water sealing at contact gaps, installation of finish-rolled screw-thread (FRST) steel bars as the LDC structures at the immersion joints, and construction of rigid connections between tunnel element ES and the cut-and-cover tunnel. Finally, onsite observation of the deformation states of Gina gaskets and monitoring of the tensile forces of FRST steel bars at the immersion joints verified the successful implementation of the new dry-land construction method, supporting the use of these techniques in closure joint design and construction for inland-river immersed tunnels.

Fish size structures in lakes of the Lower Mississippi River floodplain

Abstract The Lower Mississippi River has a floodplain that includes &gt;1350 perennial lakes carved by shifts in river courses and other hydro‐fluvial processes over eons. Notwithstanding their similar provenances, these waterbodies exhibit an immense variety of morphologies and successional stages that illustrate their natural trajectory from aquatic to forested wetlands. A result of this geographical, morphological and temporal diversity is dynamic and varied fish communities. We examined how size structures of fish communities in these floodplain lakes were associated with key in‐lake and off‐lake environmental drivers. Fish lengths were collected with standardised procedures in a sample of 30 of these lakes to construct a lake‐by‐length group matrix. Likewise, in‐lake and off‐lake environmental descriptors were collected to construct a lake‐by‐covariate matrix. Distance‐based linear models were used to assess associations between fish size structure and environmental descriptors. Smaller fish were typically associated with increasing levels of turbidity, chlorophyll‐a, phycocyanin and surrounding agriculture. Shallow, hypereutrophic floodplain lakes associated with agricultural landscapes and reduced connectivity experience harsh physicochemical environments. These conditions appeared to hinder the formation of sustained fish communities but may confer a survival advantage to juveniles or small short‐lived species. Conversely, larger fish were associated with increasing lake depth, water clarity, connectivity, and extent of surrounding forests‐wetlands. Enhanced stability and size structure were observed in communities residing in deeper and clearer lakes, suggesting that these conditions facilitated the development of longer‐lived species spanning multiple age groups. The enhanced connectivity that facilitated this increased stability also permitted the presence of larger itinerant species. Size‐structure assessments can serve as a valuable ecological and biodiversity indicator in floodplain lakes. Size‐structure assessments could supplement and, depending on objectives, even supplant conventional taxonomic analyses, and enhance surveillance of this vast and important natural resource.

Human‐initiated autocyclic delta failures

ABSTRACTRiver regulations have resulted in changes in the hydrology and particle budgets of fluvial systems. Since the 19th century, many rivers have been significantly modified to control flood hazards, to gain land from swamp areas for agricultural purposes, and to stabilize river‐levels and lake‐levels to facilitate navigation. These dramatic changes of the river courses have impacted the sediment budgets and grain‐size dissemination along them as well as the sediment distribution at the delta mouths in the downstream lakes, which could lead to slope instabilities. Deposits of such catastrophic lacustrine mass movements caused by delta collapses have been, for instance, observed in Lake Brienz (Switzerland), where relatively thick (0.5 to 1.3 m) and voluminous (&gt;1 million m3) megaturbidites are stacked in the deep basin witnessing these processes. This study uses sediment cores and seismic data to reconstruct the megaturbidites' history in Lake Brienz. Data reveal that mass‐movement deposits, originating from the Aare Delta, one of the two main inflows, have mean ages of 1853, 1905, 1942 and 1996 ce and that they were unprecedented in, at least, half a millennium. The fact that the numbers of floods and earthquakes have not changed radically over this time period implies that human impact is the most likely explanation for these failure events. Therefore, the recurrent delta collapses are attributed to the focused sediment accumulation at the front of the channelized inflow in the proximal delta region, caused by the modification of the Aare River through its straightening and channelization during the late 19th century. These findings indicate that river regulation can affect delta sedimentation, leading to autocyclic delta collapses. Those collapses, in turn, can potentially generate tsunami waves, representing an additional natural hazard for shoreline communities.

Material characteristic of Vetvisty creek placer gold and prospects for atypical-source deposits in the middle course of the Selennyakh river (Momsky and Abyisky district, Yakutia)

Background. The lower-middle course of the Selennyakh River in the Momsky and Abyisky districts of the Republic of Sakha, Yakutia, is characterized by a wide distribution of alluvial gold placers. The absence of obvious potential primary sources of these placers raises the question of their identification. Aim. To identify sources of gold placers found in interfluve area of the Selennyakh and Indigirka rivers, as well as to assess the gold-bearing potential of this area.Materials and methods. The data on the studied area obtained in previous works was analyzed. Microprobe analysis (CSRF IGEM RAS) was used to study the composition of alluvial gold grains sampled during field works in the Vetvisty Creek, the right tributary of the Selennyakh River, conducted in 2020–2021. The mineral composition of heavy concentrate was also studied.Results. The source of the gold placer under study was established to be an intermediate reservoir, i.e., Neogene coarse sand and gravel. Possible paths of gold transit within the placer were revealed. Theoretically, this allows enriched layers in the sediments feeding the placer to be localized.Conclusion. In order to replenish the gold mineral base of the country, including in such hard-toreach regions as the Arctic zone of the Russian Federation, regional research projects should be resumed. In addition, new models should be developed for forecasting and prospecting of atypical placer deposits, with gold sources from Tertiary sediments filling large Cenozoic depressions in the western rim of the Yano-Indigirskaya lowland).

Testing the Feasibility of an Agent-Based Model for Hydrologic Flow Simulation

Modeling streamflow is essential for understanding flow inundation. Traditionally, this involves hydrologic and numerical models. This research introduces a framework using agent-based modeling (ABM) combined with data-driven modeling (DDM) and Artificial Intelligence (AI). An agent-driven model simulates streamflow and its interactions with river courses and surroundings, considering hydrologic phenomena related to precipitation, water level, and discharge as well as channel and basin characteristics causing increased water levels in the Medio River. A five-year dataset of hourly precipitation, water level, and discharge measurements was used to simulate streamflow. The model’s accuracy was evaluated using statistical metrics like correlation coefficient (r), coefficient of determination (R2), root mean squared error (RMSE), and percentage error in peak discharge (Qpk). The ABM’s simulated peak discharge (Qpk) was compared with the measured peak discharge across four experimental scenarios. The best simulations occurred in scenario 3, using only rainfall and streamflow data. Data management and visualization facilitated input, output, and analysis. This study’s ABM combined with DDM and AI offers a novel approach for simulating streamflow and predicting floods. Future studies could extend this framework to other river basins and incorporate advanced sensor data to enhance the accuracy and responsiveness of flood forecasting.

Microplastics and heavy metal contamination along a land-use gradient in a Himalayan foothill river: Prevalence and controlling factors

The co-occurrence of microplastics (MPs) and heavy metals in aquatic systems has raised significant concerns, yet their relationship in freshwater ecosystems remains poorly understood. This study aims to evaluate the prevalence of MPs and factors controlling their distribution in both water and sediment in the Markanda River, Northwest India. MPs were extracted from sediment and water samples using density separation and classified through fluorescence microscopy and Raman spectroscopy. Metal concentrations in river water samples were analyzed using ICP-MS, and their correlation with MP abundance was explored. The results indicated the widespread occurrence of MP pollution across the Markanda River basin, with particle concentrations ranging from 10 to 530 particles L−1 in surface water and 1330–4330 particles kg−1 dry weight (dw) in sediment samples. The variability in MP abundance at sampling sites along the Markanda River courses results from factors such as the proximity of industrial establishments and human habitation, while the influence of grain size on MP distribution appears to be limited. Pellets (88.5 %) and fragments (8.5 %) were the most abundant types of MPs, with polyethylene (45.45 %) and polystyrene (30.9 %) being the dominant forms in water samples. The ICP-MS analysis of heavy metals in water samples indicated elevated levels of As (1.67 to 32.31 ppb) in downstream areas of the river system, influenced by human activities. While metals exhibited correlation with each other, there was a weak association, except for As, with the levels of MPs in the Markanda River. The SEM-EDX analyses to characterize chemical elements absorbed onto the surface of MP showed distinct variations in upstream and downstream sites, with the presence of elements such as Mn, Ni, Cr, Zn, As, Se, and Cu found in downstream areas. We conclude that MPs contaminated with heavy metals potentially threaten the ecological security of freshwater aquatic systems and highlight the importance of management action to reduce plastic pollution worldwide.