Channel Pattern Research Articles

Channel changes during and after extreme floods in two catchments of the Northern Apennines (Italy)

The Nure and Trebbia catchments were affected by an extreme flood event on 13-14th September 2015. This study investigates the morphological responses to the flood of the Nure and Trebbia rivers and 18 tributaries with the aims to: i) quantify channel changes in width and pattern; (ii) identify the morphological and hydrological factors which might have driven channel response; (iii) quantify channel changes which have occurred after the flood event.Channel changes were characterized by field surveys and geomorphological analysis of multi-temporal orthophotos acquired before (2011), immediately after the flood (2015) and in 2020.In the tributaries, reach-scale channel widths after the flood reached up to 15 times their pre-flood values, whereas in the main channels the post/pre-flood width ratio attained a maximum value of 4. Augmented channel width in the main rivers was mostly associated with banks and islands erosion, whereas in the tributaries it was also due to deposition of coarse sediments onto the former floodplains. Islands were swept away in the main channels while both island erosion and formation occurred in the tributaries. In terms of channel pattern, pre-flood single-thread reaches displayed mainly multi-thread morphologies after the flood, mostly in response to a sudden input of coarse sediment supply. In the 5 yr following the flood, channels slightly narrowed but still remained wider than in 2011. The narrower reaches before the flood resulted to be the most sensitive to changes even some years after the flood.Statistical analyses between the channel width changes and a series of variables showed significant positive correlations with confinement index, channel slope, and the local storm rainfall depth. This study confirms how channel widening during large floods – usually neglected in flood hazard mapping and river basin management – is a very important process which must be considered in flood hazard assessment in mountain rivers.

Decoding the complex fluvial-lacustrine sedimentary interactions: Insights from the Neogene Guantao Formation in the Bohai Bay Basin and Modern Poyang Lake, China

Small-scale lake level variations lead to significant landward/basinward shifts in the depositional system, thereby facilitating the widespread development of fluvial-lacustrine interaction sedimentary systems. Such systems are commonly found in low-gradient shallow-water continental down-warped lacustrine basins, which are favorable for the formation of composite reservoir-caprock assemblages. Nevertheless, our understanding of the sedimentary stratigraphy of the Neogene Guantao Formation remains limited due to the complex and variable spatial and temporal associations between fluvial and lacustrine deposits. Integrated analysis of the geomorphology and stratigraphy of the modern Poyang Lake Basin and ancient Bohai Bay Basin (BBB) allows us to develop a process-based fluvial-lacustrine interaction model of shallow-water depositional system. Three physiographic zones are identified based on seasonal lake shoreline migration during a certain geological sequence unit, namely fluvial-dominated zone (FDZ), fluvial-lacustrine interaction zone (FLIZ) and lacustrine-dominated zone (LDZ), respectively. The FDZ is always above the maximum lake shoreline without affection by lake basin water body and is characterized by channelized dendritic pattern of distributary channels with positive rhythmic cycles. The FLIZ is a dynamic interaction region between the maximum lake shoreline and the lowest lake shoreline. Reticular distributary channels, delta front and prodelta/lake deposits vertically superimpose and dominate the system that is featured by complex sandbody, stacked positive and negative rhythms and strong water body segmentation. The LDZ, away from the fluvial effect, was identified below the lowest lake shoreline exhibiting polycentric sheet water body, dominated by lacustrine mudstone interspersed with thin sheet-like sandstone. These results shed light on the spatial and temporal sedimentary heterogeneity in such dynamic fluvial-lacustrine interaction systems. The proposed fluvial-lacustrine interaction model may serve as a valuable analogue for identifying sedimentary types and predicting sandstone reservoirs in similar shallow-water settings ranging from continental down-warped lacustrine basins to cratonic basins, and fault-depression basin gentle-slope belts.

Hydromorphological degradation modifies long-term macroinvertebrate responses to water quality and climate changes in lowland rivers

Due to decades of persistent anthropogenic pressures, lowland rivers represent one of the most severely impaired habitats in Europe. Despite improved water quality, novel stressors, particularly climate change, are emerging with most lowland rivers suffering from past hydromorphological degradation. We aim to elucidate how such degradation alters the biological response in multiple-stressor environments, as this has rarely been considered in studies documenting long-term development of anthropogenically impacted rivers. Here, benthic macroinvertebrates, water quality and hydroclimatic variables were monitored over a period of two decades in nine of the largest Czech rivers. Detailed data on hydromorphological degradation allowed us to track distinct patterns in rivers with high and low levels of degradation. Temporal changes in environmental variables showed similar patterns in both site groups, characterised by reduced organic and nutrient pollution but increased hydroclimatic and salinity stress. 150 % increase in total abundance, especially in abundance and richness of sediment-dwelling and non-native taxa was found in both site groups. While the increase in abundance was due to improved water quality and rising water temperature, the longer duration of minimal flows had a negative effect on species richness, hampering species gain particularly at highly degraded sites. Our results provide novel evidence that degree of hydromorphological degradation modifies long-term macroinvertebrate responses to anthropogenic pressures. Less degraded sites displayed several favourable changes, such as 27 % increase in total and 23 % increase in potamal indicator richness, and stabilisation of the assemblages with few functional changes. In contrast, highly degraded sites experienced 9 % reduction in evenness, 235 % increase in proportion of non-native taxa and functional reorganisation, changes congruent with continuous deterioration. While overall water quality at studied sites has improved, consequences of climate change and high degree of hydromorphological degradation limit biotic recovery in multiple-stressor lowland rivers.

Changes in the meander belt and channel pattern in the middle-low segment of the Cuarto river. Córdoba. Argentina

The Cuarto River is an important watercourse in the Córdoba Province, Argentina. Its middle-low segment crosses the eastern plains of this province, one of the most populated and (agricultural-livestock) productive regions of the country. In this segment, the channel and fluvial belt morphometric parameters exhibit notable changes downstream. Understanding the morphodynamics of the Cuarto River allows the characterization and definition of channel reach with tendencies towards migration, aggradation and overflow. In this way, it is possible to identify critical channel reaches, a fundamental aspect for effective planning. This work aims to characterize the downstream changes in the fluvial belt, meanders geometry, channel pattern and channel slope, along the middle-low segment of the Cuarto River and link these modifications with authigenic (sediment supply and transport regime) and allogenic controls. Five channel reaches (R1-R5) were selected according to geological-geomorphological criteria and different geometric parameters (channel width, channel slope, braided index, meander geometry, confinement degree) were determined for each of them. Empirical equations were used to establish relationships between these geometric parameters. Although most parameters showed a generally downward trend towards downstream reaches, marked changes were observed. Particularly, in the R1-R2 reaches, the fluvial belt widens and is unconfined, and the channel width and braided index also increases. The relationship between meander length/channel width (Lm/w) and radius of curvature/channel width (rc/w) obtained were within the ranges for free meanders (8–14) and high mobility (2–3), respectively. These parameter values are associated with alluvial channels and suggest limitations in transport and conditions for sedimentation. However, in R3, R4 and R5, the fluvial belt narrows and becomes confined, with high sinuosity, a reduction in the width of the channel and the braiding index. This pattern is expected for reaches characterized by predominance of transport and a tendency to a mixed or suspensive load. Moreover, both groups of reaches also exhibit an abrupt contrast in bedload size (from very coarse sand/gravel in R1 and R2 to fine/very fine sand in R3, R4, and R5). The similarity between the exponents of the predictive functions (Lm/w, rc/w, and Lm/rc) and those obtained for the Cuarto River, in addition to the satisfactory regression coefficients of the measured parameters suggest an acceptable balance between meander geometry and channel width regime of sediment transport. The middle-low reach of the Cuarto River shows notable changes, which can be linked to regional-scale allogenic factors such as morphostructures and lithology (R1-R2 with elevated morphostructure, R3-R4 are transitional reaches towards depressed plains, while R5 with subsidence environments). Nonetheless, the river demonstrates the capacity to regulate these factors at the reach level through authigenic processes. Thus the variability of channel width, channel slope, braiding index, meander geometry and degree of confinement are explained mainly by downstream changes in sediment supply and transport regime (authigenic controls) and secondarily by changes in regional slope and banks lithology (allogeneic controls).

3D numerical model of a concentrated photovoltaic thermal (CPV/T) system for thermal and electrical performance optimization

Concentrated Photovoltaic Thermal systems, integrating both photovoltaic and thermal technologies, have gained significant attention as a sustainable and efficient means of harnessing solar energy. This research paper investigates the performance of CPV/T systems by analysing four different collectors under diverse operating conditions. The collectors under scrutiny include Rectangular Channels, Trapezoidal Channel, Hexagonal honeycomb, and Chevron Pattern absorbers, each subjected to distinct parameter variations to comprehensively evaluate their efficiency and potential for integration into renewable energy systems. The study systematically examines the collectors' performance under varying environmental conditions, including 6 kWh/m2 solar irradiance, 24 °C ambient temperature, and 3 m/s wind speed. The impact of changing parameters such as velocity and fluid flow rate ranges from 20 to 30 kg/h on the overall system efficiency is thoroughly analysed. Through numerical simulations and experimental validations, the paper aims to provide insights into the dynamic behaviour of each collector type and their suitability for different applications and geographical locations. The analytical result correlates with the numerical mathematical models to provide more convincing evidence that the acquired data is accurate. At a flow rate of 30 kg/h, the overall efficiency is determined to be 49.3 % for the rectangular channel absorber, outperforming hexagonal honeycomb (41.2 %), chevron pattern (41.1 %), and Trapezoidal channel (40.9 %) absorbers. The simplicity and cost-effectiveness of the fabrication process for rectangular channel absorbers, achievable through standard manufacturing techniques such as etching or pressing into materials like copper, aluminium, or stainless steel, emerge as primary advantages.

An enhanced and expanded Toolbox for River Velocimetry using Images from Aircraft (TRiVIA)

AbstractDetailed, accurate information on flow patterns in river channels can improve understanding of habitat conditions, geomorphic processes, and potential hazards to help inform water management. Data describing flow patterns in river channels can be obtained efficiently via image‐based techniques that have become more widely used in recent years as the number of platforms for acquiring images has expanded and the number of algorithms for inferring velocities has grown. Image‐based techniques have been incorporated into various software packages, including the Toolbox for River Velocimetry using Images from Aircraft (TRiVIA). TRiVIA is a freely available, standalone computer program that provides a comprehensive workflow for performing particle image velocimetry (PIV)‐based analyses within a graphical interface. This paper summarizes major enhancements incorporated into the latest release of TRiVIA, version 2.1. For example, a new Tool for Input Parameter Selection (TIPS) provides guidance for specifying key inputs to the PIV algorithm by allowing users to explore relationships between flow velocity, pixel size, output vector spacing, and frame interval. Improved visualization capabilities include the ability to create streamlines and display PIV output on an interactive web map. The program now provides greater flexibility for importing field data in various formats and selecting which observations to use for accuracy assessment. The most substantial additions to TRiVIA 2.1 are the ability to integrate bathymetric information with image‐derived velocity estimates to calculate river discharge and to use images acquired from moving aircraft to efficiently map long segments of large rivers to support habitat assessment, contaminant transport studies, and a range of other applications.

Structural characteristics and spatiotemporal changes of a reticular river network based on complex network theory

eticular river networks, characterized by a dense pattern of rivers and loop structures, are primarily found in lower river delta plains and are being modified due to rapid population growth and urbanization. This change impacts the distribution of water resources and could result in more frequent and severe floods. Therefore, accurately characterizing the structure of river networks is crucial. In this study, the structure and its changes of a typical plain reticular river network in the Lixia River hinterland area (LRHA), China, were evaluated in the 1960s, 1970s, 1980s, 2009, and 2016 using complex network theory tools at global and local scales. First, we constructed a complex network model by generalizing river sources, outlets, and confluences as nodes and channels as edges. By comparing with the equivalent random networks, it is found that the river networks of LRHA have large clustering coefficients and short characteristic path lengths. These characteristics classify it as a small-world network within complex networks, which is notably efficient for water and material transportation. Second, at the global scale, the global efficiency in complex network theory considers the interconnectivity between nodes and assesses the potential paths between them, effectively reflecting the connectivity status of the river network. At the local scale, the betweenness centrality of a complex network can reflect the control ability of water and material transportation at river nodes. After the 1970s, constructing several new mainstem rivers gradually shifted nodes with high betweenness centrality towards the north–south flowing rivers. In addition, we used Moran’s I to quantify the spatial clustering of the network’s indicators and found that degree and betweenness centrality exhibited higher spatial clustering, with mean Moran’s I values of 0.398 and 0.300, respectively. Finally, we compared the structure of river networks in urban versus rural areas and the mainstem versus tributary streams. We found that urban river networks and mainstem rivers exhibit a higher degree of betweenness centrality, resulting in a greater capacity to regulate water and material cycles within the river network. According to the research findings, complex network theory has been proven to effectively evaluate the structure of reticular river networks at various scales. It enhances our comprehension of the river network’s structure and assists managers in gaining a deeper understanding of how the river network structure influences the distribution of water resources.

Rare earth elements and yttrium (REY) in fjord waters: Comparison between seawater in the Trondheimfjord (Norway), its local riverine REY sources and the North Atlantic

The rare earth elements and yttrium (REY) are critical resources increasingly released into the environment due to their pivotal role for an ever-growing number of high-tech products and processes. Fjords, worldwide and particularly in Norway, are not only of high importance for biodiversity but they also have great economic value. Knowledge on the distribution of REY in Norwegian coastal and riverine waters is, however, surprisingly scarce. We here report REY data for water samples from depth profiles from ten stations in the Trondheimfjord, one of Norway’s largest fjords, several Norwegian rivers, and two wastewater treatment plants in Trondheim.Our results show that water from different locations in the Trondheimfjord yield similar REY concentrations that correlate well with dissolved organic carbon. The deepest sample at each station shows the lowest REY concentrations. The shale-normalised (SN) REY patterns of the fjord waters resemble those of North Atlantic seawater, but can be distinguished from open-ocean water by the smaller fractionation between light and middle REY (PrSN/TbSN ≥ 0.5). Stations in the vicinity of a river mouth show considerably higher REY concentrations at shallow depths. The respective REYSN patterns resemble the typically flat patterns of boreal rivers that are often rich in nanoparticles and colloids (NPCs). The REYSN patterns of the four rivers investigated (Nidelva, Orkla, Gaula, Stjørdalselva) show the features of the shallow(er) fjord water samples but have even higher REY concentrations. Ultrafiltration (< 1 kDa) data for the Nidelva corroborate that the typical “REYSN seawater signature” is in fact already present in freshwater where it is, however, usually hidden by the REY associated with NPCs. The local wastewater treatment plants release anthropogenic Gd (from contrast agents used in magnetic resonance imaging) into the Trondheimfjord, but this signal is immediately diluted and thus is not observed in the REYSN patterns of the fjord water. However, our results in general suggest that the slightly elevated Gd/Tb ratios observed in almost all fjord waters relative to North Atlantic marine water may rather be due to the presence of anthropogenic Gd in the southern North Sea and the Baltic Sea, corroborating that anthropogenic Gd can be applied as a sensitive far-field watermass tracer.

Analysis of Marketing Channels And Marketing Efficiency of Corn Farmers (Zea Mays L) Tanjung Morawa

Purpose: This study aims to (1) identify the corn marketing channels, (2) determine the corn marketing margins, and (3) evaluate the efficiency of corn marketing in Tanjung Morawa District. Methodology: A sample of 30 corn farmers from three villages with corn farming areas was selected. A quantitative descriptive analysis was used to examine marketing channel patterns and analyze marketing costs and margins. Results: The study found that Marketing Channel I is widely used by farmers, who prefer selling corn directly to collectors. The marketing efficiency values for the first (I) and second (II) marketing channels are 10% and 16.6%, respectively. Findings: Both marketing channels are efficient. This indicates that the marketing channels involved in the marketing of shelled corn in the study area do not involve lengthy marketing institutions, resulting in low marketing costs and margins, and the selling price received by the final consumer is not much higher than the price received by the farmers. Novelty: This research provides insights into the efficiency of corn marketing channels, highlighting the benefits of shorter marketing pathways. Originality: The study offers a detailed analysis of marketing channel efficiency for corn, contributing to the understanding of effective agricultural product marketing. Conclusions: The corn marketing channels in Tanjung Morawa District are efficient, benefiting both farmers and consumers. Type of Paper: Empirical Research Article

Comparison of the Impact of Different Economic Patterns on Population Inflows: Evidence from China’s Guangdong, Jiangsu, and Zhejiang Provinces

Between 2000 and 2022, China’s top three highest GDP provinces, Guangdong, Zhejiang, and Jiangsu, each having distinct economic structures, displayed different paths of development in their net population inflows. This prompts us to ponder how the economic patterns of the most economically developed regions impact population inflows. To answer the question, we first examine each economic pattern and use the entropy weight method to construct a comprehensive index to capture the features of each economic pattern in different regions. Then, we employ a two-way fixed effects model with panel data from the three provinces to conduct the empirical analysis. Moving forward, we expand the sample size to 10 provinces, including China’s eastern metropolitan areas, to extend the analysis beyond the previously selected regions and corroborate the consistency and robustness of our model. The results show that the Wenzhou pattern, featured primarily by the private sector, has the most impact on population inflows, followed by the Pearl River pattern, driven by an export-oriented economy. In contrast, the Sunan pattern, characterized by the collective economy, has an insignificant impact. We further dissect and determine the essential factors influencing population inflows within the three economic patterns and estimate the sustainability of the economic pattern via net population inflows. Our findings can provide insights for policy-makers to understand and utilize economic patterns in order to impact population inflows effectively. Specifically, we propose that the observable net population inflows can serve as an indicator to evaluate the sustainability of local economic patterns, thus providing another perspective on assessing the region’s economic development.

Distinctive hydrodynamic properties and ecological responses of multi-thread rivers under different degrees of multiplicity in the Upper Yellow River

Alluvial rivers that exhibit multi-thread patterns are common in nature and can be the dominant channel morphology in large rivers. However, their ecological properties in response to diverse and dynamic channel morphology has gained limited attention and remained poorly understood. In this study, we adopted an eco-hydraulic model by integrating a hydrodynamic, a sediment-transport, and a habitat-suitability model to assess habitat quality for fish species (Schizopygopsis pylzovi and Platypharodon extremus) in three anabranching reaches with each exhibiting a distinct anabranching morphology in the Upper Yellow River, eastern Qinghai-Tibet Plateau. Based on the hydrologic data and actual channel morphology, we modeled the hydrodynamic and sediment-transport conditions for a period spanning ten years, and simulated habitat conditions under a potentially changing environment with different flow magnitudes and frequencies. The results indicated that the average flow velocity in the low and mid-order anabranching reaches is higher than that in the high-order, complex anabranching reaches. Meanwhile, the bedload transport rate was higher in the high and mid-order anabranching reaches than that in the low-order anabranching reach, demonstrating a greater transport efficiency of multi-thread systems with a greater multiplicity. Consequently, the habitat suitability shows a deteriorating trend over the ten-year modeling period and Schizopygopsis pylzovi shows better habitat status than Platypharodon extremus. The flow magnitudes and frequency also have a significant impact on the distribution of high habitat suitability index among the different river patterns in Upper Yellow River. This study can provide valuable information to optimize ecological outcomes and provide valuable insights for future dam operation strategies and consideration efforts aimed at preserving and restoring riverine ecosystems.

An iterative method for synthesizing the antenna array of a logical interference compensator

An iterative method has been developed for synthesizing the antenna array of a logical interference compensator according to the requirements for the radiation pattern of the compensation channel. An objective function is proposed that allows reducing the problem of multi-criteria synthesis of a compensation channel to the problem of scalar optimization. The objective function can be divided into three particular objective functions. Optimization of the first private function is carried out during an iterative process. The optimal values of the remaining two partial objective functions correspond to the known solution of the synthesis problem. The results of numerical studies have confirmed the universality of the method with respect to the shape of the antenna array opening boundary. This allows you to search for the optimal set of parameters taking into account one particular objective function. For other particular target functions, the optimal solution is found according to the formulas of matrix synthesis of antennas.

Cross-shore parallel tidal channel systems formed by alongshore currents

Parallel tidal channel systems, characterized by commonly cross-shore orientation and regular spacing, represent a distinct class of tidal channel networks in coastal environments worldwide. Intriguingly, these cross-shore oriented channel systems can develop in environments dominated by alongshore tidal currents, for which the mechanisms remain elusive. Here, we combine remote sensing imagery analysis and morphodynamic simulations to demonstrate that the deflection of alongshore tidal currents at transitions in bed elevation determines the characteristic orientation of the parallel tidal channels. Numerical results reveal that sharp changes in bed elevation lead to nearly 90-degree intersection angles, while smoother transitions in bed profiles result in less perpendicular channel alignments. These findings shed light on the potential manipulation of tidal channel patterns in coastal wetlands, thus equipping coastal managers with a broader range of strategies for the sustainable management of these vital ecosystems in the face of climate change and sea level rise.

Analisis Margin Pemasaran Sayuran Selada Hidroponik di Stekaifarm Kelurahan Wailan Kecamatan Tomohon Utara

This study aims to analyze the marketing margin of Stekaifarm hydroponic lettuce vegetables in Tomohon city, Wailan Village, North Tomohon District.This study uses primary data types and secondary data. Primary data obtained by themselves from observations that have been carried out directly at the research location as well as from interviews with respondents. Meanwhile, secondary data is data sourced from data that has been issued by Stekaifarm Sampling is carried out by interviewing farmers to find out other sample sources (Snowball Sampling). The number of research samples was 1 corn farmer and 3 retailers. The results of the study were analyzed using marketing margin analysis. The results of the study were analyzed using marketing margin analysis. Based on the results of the research that has been done, it can be concluded that there are only 2 levels of Stekaifarm lettuce marketing with 1 zero-level marketing pattern and 3 one-level marketing patterns. From the results of the study, the margin obtained by each institution varies in pattern I marketing level one margin obtained IDR30,000 with a profit margin of IDR19,925, pattern channel II level one IDR25,000 with profit margin IDR16,499 and pattern channel III level one IDR25,000 with profit margin of IDR23,525. The largest margin is found in the channel I pattern while the largest profit margin is in the channel III pattern. There is a difference in profit margin in each institution because the costs incurred are also different from the pattern of the first channel which has the largest marketing costs because the marketing channel is the longest.

Margin Pemasaran Komoditi Kentang Di Kecamatan Modoinding Kabupaten Minahasa Selatan

The objectives of this study were to map market actors, calculate marketing margins for potato crops, and describe the potato marketing channels in Modoinding Sub-district. The research took place in May 2023 and was conducted in Modoinding District, South Minahasa Regency. Data were collected through primary data by conducting interviews with owners or farmers who cultivate potato crops using a list of questions (questionnaires) that have been prepared. Secondary data were obtained through literature searches from literature, articles, journals, previous research and relevant data and reports from relevant agencies such as the Department of Agriculture, BPS and district, sub-district and village governments to support primary data. Samples were taken from 30 people in 10 villages using simple random sampling and for traders using snowball sampling. The data obtained were analyzed descriptively, and using tables, and described in the form of surveys obtained through direct interaction with research subjects or test subjects using questionnaire techniques. The marketing channels obtained can be described as a whole pattern and level of marketing channels. The results of this study show that the potato marketing margin of each institution in Modoinding sub-district is different between Manado, Bitung, and Kotamobagu channels. Farmer's share received by farmers in the Bitung channel is higher than farmer's share in the Manado and Kotamobagu channels, but farmers still get the same purchase price. Channel (farmer - intermediary - retailer - consumer). Farmers still get the same price and the costs of labor and transportation are borne by buyers, namely collectors and retailers.

Pola Komunikasi Organisasi Alumni Syubanul Wathon (Aswa) Balapan dalam Meningkatkan Ukhuwah Islamiyah

Organizational communication patterns in the Aswa Balapan organization are related to the implementation of improving the intertwined ukhuwah islamiyah. This communication pattern is intended to understand that every organization must have its own communication pattern for the continuity of its members. So it is necessary to have the right communication pattern in Aswa Balapan. This study intends to examine the extent to which the communication patterns of the Aswa Balapan organization as an effort to increase the sense of ukhuwah islamiyah among members based on the analysis of the interactive model of the Miles and Huberman theory with descriptive qualitative methods and data collection techniques in the form of interviews, observation and documentation. The results of the study, namely, communication patterns in the Balapan Syubanul Wathon Alumni (Aswa) organization are supported by various types of communication patterns ranging from chain, circle, wheel, and total channel patterns. The existence of symbolic interaction and the right communication flow in Aswa Balapan through various activities, such as makrab, open together, competition workshop, Aswa Balapan bersholawat. Symbolic interaction also plays an important role in building ukhuwah islamiyah bonds among Aswa Balapan members.

Late glacial to Holocene fluvial dynamics in the Upper Rhine alluvial plain, France

AbstractHigh-resolution sedimentological and geochronological investigations of paleochannel systems in the Ried Central d'Alsace (northeastern France) allow for the reconstruction of the late glacial and Holocene fluvial evolution of this section of the Upper Rhine alluvial plain. During the Oldest Dryas, the landscape featured a dominant braided Rhine system and, to a lesser extent, a braided Fecht system. The shift to the Bølling-Allerød saw a narrowing of the Rhine's active channel belt, the development of a complex channel pattern, and the genesis of the Ill River. The river channel patterns remained unchanged during the Younger Dryas. In the Early Holocene, the Rhine's active belt narrowed further, and the Rhine and Ill Rivers developed braided-anastomosing and anastomosing channel patterns, respectively. Throughout the Holocene, both rivers maintained their channel patterns while migrating east and west across the alluvial plain, respectively. In the late glacial, fluvial dynamics in this section of the Upper Rhine plain were primarily influenced by climate-related environmental and hydrogeomorphological changes. Conversely, during the Holocene, the evolution of the fluvial hydrosystems was driven by a complex interaction of climatic and non-climatic factors, including human activity at the catchment scale, alluvial plain architecture, and local neotectonics.

Geomatics-enabled Interdisciplinary Approach Based on Geospatial Data Processing for Hydrogeological Risk-analysis

Hydrogeological risks that are associated with rivers have emerged as a significant concern worldwide, impacting both natural ecosystems and human settlements. This contribution presents an interdisciplinary project that leverages many technologies for data-acquisition and modeling to comprehensively analyze and manage risks in riverine environments. The project integrates geomatics, geological, and hydrological techniques to provide a holistic understanding of river dynamics and their associated hazards. As a central component of this project, geomatics plays a pivotal role in instrumental field surveying through the deployment of photogrammetry and LiDAR instruments. Remote-sensing data from satellite imagery further enriches the project’s temporal analysis capabilities. By analyzing this data over time, researchers can monitor changes in river patterns, land use, and climate-related variables; this helps identify trends and potential triggers for hydrological events. To manage and integrate the vast amount of geospatial information that is generated, a geodatabase within a geographic information system (GIS) has been established. It enables efficient data storage, retrieval, and analysis, fostering collaboration among multidisciplinary researcher teams. This system offers tools for risk-assessment, modeling, and scenario planning; these allow for proactive measures for mitigating hydrological risks.

What controls river widening? Comparing large and extreme flood events

AbstractExtreme (i.e., centennial‐scale) floods are by definition rare and can therefore be difficult to study. As a result, case studies of response to extreme floods can provide unique insights. On 15 November 2021, the Nicola River in British Columbia, Canada, experienced a 200‐year flood that increased the average width of the Nicola River by more than 50% (35 m), leaving the only highway in the region impassable for nearly 12 months. This research assesses the spatial variability of erosion along a 71‐km‐long segment of the Nicola River during a period with a large flood (2015–2018) and a second period containing the extreme flood in 2021 (2018–2021). We use a random forest statistical analysis to explore the most important valley and channel characteristics affecting relative widening during both periods. Unit stream power, gradient and valley confinement were the primary determinants of erosion during the extreme flood, whereas vegetation cover, channel pattern and surficial material were less important. Erosion during the large flood event was not related to these variables, with channel pattern providing a better indication of widening potential. As the Nicola River is flanked by erodible glacial deposits, this work provides important insight into river response in the paraglacial environments that are common throughout much of Canada and the northern United States, as well as Europe and Asia, but less intensely studied. In these settings, the geomorphic response to large floods may not be representative of the potential erosion (and infrastructure impacts) that can occur during extreme events, which destabilize glacial terraces in confined reaches. Historical observations should therefore be used with caution in paraglacial settings as extreme events may not be captured in available data, creating a perception of stability in confined reaches that may have the potential to erode dramatically during extreme events.

Fluviomorphic trajectories for dryland ephemeral stream channels following extreme flash floods

AbstractEphemeral alluvial streams pose globally significant flood hazards to human habitation in drylands, but sparse data for these regions limit understanding of the character and impacts of extreme flooding. In this study, we document decadal changes in dryland ephemeral channel patterns at two sites in the lower Colorado River Basin (southwestern United States) that were ravaged by extraordinary flash floods in the 1970s: Bronco Creek, Arizona (1971), and Eldorado Canyon, Nevada (1974). We refer to these two floods as ‘fluviomorphic erasure events’, because they produced blank slates for the channels that were gradually moulded by more frequent but much smaller flood events. We studied georectified aerial photos that span ~60 years at each site to show that both study sites recovered to their pre‐flood condition after ~25 years. We employ channel network metrics: stream‐link area (SLA), geometric braiding index and junction‐node density. Each metric decreased during the short‐duration extreme flood erasure events. Subsequently, a fluviomorphic trajectory at a decadal tempo returned the channels to pre‐flood values. The SLA decreased at rates of 3.6%–4.1% per year in the decade following the floods. The extreme flood events decreased the pre‐flood geometric braiding index at the two sites by 56%–68%, and it took 15–24 years for this index to recover to pre‐flood values. In contrast, it took 30–35 years for the channels to recover to a uniform pre‐flood channel form, as indicated by the spatial distribution of bars and junction nodes. Our results document baseline examples of ephemeral stream channel evolution trajectories, as future climatic change will likely accelerate increases in the magnitudes and frequencies of extreme floods and geomorphic erasure events.