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This study used a physical model to investigate the internal dynamics and external effects of upstream incoming sediment concentration and downstream lake level on channel morphology evolution in a laboratory-scale shallow lacustrine delta under the background of Poyang Lake Delta (China). The results show that the channels exhibit straight, braided, and no-channel patterns. Sediment deposition in the downstream channel causes rising topography, backwater pressure, and deposition lobes, leading to periodic channel switching. Higher incoming sediment concentration and lake level can result in a shorter evolution period, larger swing angle, and higher swing point position for the main channel in the delta. Furthermore, the delta topography is more likely to change from a distributary to a radial pattern with higher incoming sediment concentration, and this factor appears to play a more important role than the downstream lake level in fundamentally influencing the deltaic channel patterns. [ABSTRACT FROM AUTHOR]

Due to the movement of waves, a backwater or dock is primarily affected by two types of external forces: horizontal and uplift forces. Because of wind and waves, port and harbor structures are subjected to high lateral stress and enormous uplift loads. However, limited experimental investigations are reported on piles subjected to uplift-lateral loading, which is investigated in the present work. Specifically, the effects of the relative density of sand on the combined loading behavior of the pile are a focus to cover the wide range of conditions of sand. According to the findings, coupled loading significantly impacted the pile capacity in both lateral and uplift modes. The effect is pronounced for piles of shorter length embedded in loose to medium dense sand conditions and found to diminish for very dense conditions because of the initially mobilized high resistance on piles subjected to independent loading. Equations are developed for estimating the capacity of piles under combined loading. [ABSTRACT FROM AUTHOR]

Solid material sources, such as sediment, large wood, and vehicles, intensify flash flood hazards. This paper provides a detailed review of processes involving the recruitment, entrainment, transport, and blockage dynamics of various solid material sources. Results indicate that sediment supplied by processes like landslides and debris flows can obstruct river channels, leading to a sudden increase in flash flood levels. The failure of a barrier dam results in an expansion of downstream inundation areas. Large wood and floating vehicles transported by flash floods and debris flows may directly impact and destroy built structures or form blockages at built structures. Blockages lead to a backwater rise, and the sudden amplification of flow during the failure of these blockages causes more severe disasters. Based on these analyses, the paper proposes future research directions primarily focusing on the changes in sediment burial processes caused by the sheltering effects of building groups. Furthermore, the study aims to investigate the flow amplification effects of large wood and vehicle blockage. [ABSTRACT FROM AUTHOR]

Reliable flood hazard mapping is crucial for enhancing flood preparedness, especially in poorly gauged and vulnerable areas. Yet, current flood models are either highly detailed and computationally intensive or oversimplified, failing to capture important flow dynamics. Here, we present the Rapid Estimation of FLood EXtent (REFLEX), a hydro‐geomorphological model for flood hazard mapping at multiple scales that improves upon the existing Height Above the Nearest Drainage model by constraining flood extent using physically‐coherent flood volumes. Input volume is distributed from channel to hillslope cells by using an iterative optimization based on the Manning's equation, bypassing the need for accurate rating curves. The model improves the accuracy of inundation extent in flat areas by accounting for backwater effects, and in coastal zones by extending the calculation boundaries beyond the direct watershed area. REFLEX was tested over five areas with different climatic conditions, including flash‐flood prone catchments in Italy and large floodplains in the Zambezi river basin. Results denote skillful representation of flooded areas in the Italian catchments, with critical success index (CSI) up to 0.62. In the African cases, REFLEX produced the best estimates of the flood extent and CSI comparable with two state of the art global inundation models. REFLEX is a competitive flood modelling tool for large scale and high resolution applications thanks to its limited input requirements and computing times two orders of magnitude shorter than equivalent hydraulic simulations. [ABSTRACT FROM AUTHOR]

This paper explores different methods of computing backwater depth for open-channel flow, such as one- to multi-dimensional models, finite difference approaches, and artificial intelligence methods. This paper primarily focuses on one-dimensional methods and states the implication, advantages, and disadvantages, verification process, and performance of each method. This paper discusses different parameters that influence backwater and their impact. Additionally, this paper compares the discussed one-dimensional methods with each other due to their common usage of experimental and field datasets as well as their popularity in implementation. It was concluded that while the WSPRO method significantly overestimated and the Yarnell's method underestimated the afflux value, the measured afflux values are closest to the values computed by the energy and momentum methods. [ABSTRACT FROM AUTHOR]

Interdisciplinary teams investigating the origins of agriculture in the Eastern Fertile Crescent in the 1950s through 1970s considered the region a primary center of initial domestication and agricultural emergence. Political events then shifted the focus of archaeological investigation on agricultural origins to the Western Fertile Crescent. Decades of subsequent research appeared to indicate that the west was the earliest and most important center of agricultural origins in Southwest Asia, with the Eastern Fertile Crescent portrayed as a backwater that lagged behind transformative innovations from the west. The resumption of investigations in the east in the early 2000s, coupled with new scientific methods for documenting agricultural emergence, has reestablished the region as a heartland of domestication of both crop and livestock species. This broad topic is covered in two papers, beginning here with the history of this work from the 1950s through the early 2000s. The second paper will present a synthesis of recent work in the east, evaluating the continued relevance of early work in light of recent explanatory models for agricultural origins. [ABSTRACT FROM AUTHOR]

An analytical solution for the non-inertia wave model is presented for a lateral inflow that is uniformly distributed between any two locations. The model is solved by using the Laplace transform. A stage-discharge relation is taken at downstream boundary, and the upstream boundary is either water-depth based or flow rate based. The flow rate responses for the positions between the lateral inflow boundaries are found to be dependent on the location of observation, which is not the case for the positions downstream and upstream of the lateral inflow boundaries. The backwater effect induced by the lateral inflow is observed in the flow rate as well as the water depth, irrespective of the type of upstream boundary. For a flow rate hydrograph imposed at the upstream section, the flow rate and water-depth responses for the locations downstream to the location of lateral inflow are independent to the location of lateral inflow in contrast to the case of a water-depth hydrograph at the upstream section. [ABSTRACT FROM AUTHOR]

Flooding in urban communities is an increasingly prevalent issue that causes significant financial loss, property damage, and long-term adverse health effects. Backwater valves can reduce the risk of basement flooding during sewer surcharge events at the lot-level scale. However, guidelines for installation and maintenance can be limited or inconsistent, with little underlying literature or research. Without proper installation and ongoing maintenance, solids can accumulate, resulting in the valve failing to close or being unable to form a watertight seal during a sewer surcharge event. This research provides insights to inform future design iterations or updates to best practices guidelines by characterizing flow patterns and velocities within the Mainline Fullport backwater valve. A series of laboratory experiments are described at two common flow rates (0.1 and 0.3 L/s) and various slopes (−2% , 0%, 2%, 5%, and 10%) using fluorescent particle tracers as a novel replacement for more traditional laser-based particle image velocimetry. Results revealed a complex flow environment influenced by slope, flow rate, initial water level conditions, and the fluid properties of water. Regions for potential solids accumulation leading to mechanisms of potential failure occurred near the inlet, at the downstream edge of the closing gate, and along the side channels. Increased slopes generally improved flow conditions, with least favorable outcomes below a 2% slope and diminishing returns above a 5% slope. Between 2% and 5% slope, conditions were the most complex but improved with increased flow rates. Fluorescent particle velocimetry shows promise as a powerful, affordable, and reliable tool to visualize flow and measure velocities in complex, shallow flow environments where other methods are unsuitable. Practical Applications: Floods are an increasingly common and highly damaging problem, during which wastewater can back up in sewage pipes into basements. A backwater valve reduces the risk of sewer back-up and basement flooding. The valve closes when sewage flows backward and seals shut until the event ends. A backwater valve must be properly installed and maintained to ensure intended performance, but the associated guidelines can be unclear. To help improve those guidelines, this paper clarifies performance for various flow patterns and slopes in a backwater valve at different flow rates using laboratory experiments. Faster-moving water flushes debris and helps keep the valve clean, but raising slopes to achieve that may be difficult or expensive. Experiments used particles glowing under a black light to visualize water movement. Results reveal complicated flow patterns, with the worst conditions for flushing debris developing below 2% slope (2-cm drop per 100-cm of length) and the best conditions at 5% or above. Between 2% and 5% slope, the benefits of increasing slope were complex and depended on other factors. Methods used in these experiments can be adapted for different applications because they are relatively inexpensive and can work in shallow-water environments. [ABSTRACT FROM AUTHOR]

The ICESat-2 and SWOT satellite earth observation missions have provided highly accurate water surface slope (WSS) observations in global rivers for the first time. While water surface slope is expected to remain constant in time for approximately uniform flow conditions, we observe time varying water surface slope in many river reaches around the globe in the ICESat-2 record. Here, we investigate the causes of time variability of WSSs using simplified river hydraulic models based on the theory of steady, gradually varied flow. We identify bed slope or cross section shape changes, river confluences, flood waves, and backwater effects from lakes, reservoirs, or the ocean as the main non-uniform hydraulic situations in natural rivers that cause time changes of WSSs. We illustrate these phenomena at selected river sites around the world, using ICESat-2 data and river discharge estimates. The analysis shows that WSS observations from space can provide new insights into river hydraulics and can enable the estimation of river discharge from combined observations of water surface elevation and WSSs at sites with complex hydraulic characteristics. [ABSTRACT FROM AUTHOR]

Water‐choice experiments were conducted using glass eels of Anguilla japonica and A. marmorata, which coexist in subtropical East Asian rivers. The results of the present study, together with those of previous water‐choice experiments, suggest that salinity enhances the odor preferences of glass eels. Compared to A. marmorata glass eels, A. japonica glass eels were more strongly attracted to water collected from a leaf detritus‐accumulating backwater area than to normal river water under the same salinity conditions. These results suggest that interspecific differences in odor preferences may facilitate their habitat segregation. [ABSTRACT FROM AUTHOR]

An analytical solution for the diffusive wave model with a concentrated lateral inflow for a finite channel is presented. Flow depth and flow discharge are taken as the upstream boundary, whereas the downstream end is subjected to a stage–discharge relationship. The focus is on analyzing the impact of the lateral inflow concentrated at different locations on the flow discharge and flow depth. Unit-step responses for all the impulse responses for the lateral inflow are also presented and compared with the corresponding results of a semi-infinite channel where the downstream boundary is ignored. For higher Peclet numbers, the semi-infinite channel responses are found to be a satisfactory substitute for the finite channel responses to predict flow discharge, when a flow discharge is imposed at the upstream boundary, and a steady uniform condition is applied at the downstream boundary. However, for lower values of Peclet number, the same is not replicated. Furthermore, for the flow depth responses, the semi-infinite channel results are not appropriate approximations for finite length channel responses since the flow depth is observed to be sensitive to the backwater effect induced by the downstream boundary. [ABSTRACT FROM AUTHOR]

Water quality assessment is crucial for evaluating its sustainable use by dependent biota. The present study investigates physico-chemical parameters and primary productivity of the Anchuthengu - Akathumuri backwater (8° 39' to 8° 44"N latitude and 76° 45' to 76° 47"E longitude) located in southern Kerala from March to August 2022. Significant spatial and temporal fluctuations were observed in temperature, salinity, phosphate-phosphorus, nitrate-nitrogen, and nitrite-nitrogen. Dissolved CO2, alkalinity, BOD, DO, and pH levels remained within optimal ranges. Reduced transparency during monsoon months was attributed to turbidity and low solar radiation, accompanied by decreased salinity (0-5). Fluctuating levels of sulphate (10-25 mg/l), nitrate nitrogen (4-5 mg/l), nitrite nitrogen (0.1-0.2 mg/l), and phosphate (0.2-0.3 mg/l) were likely influenced by irregular monsoons and anthropogenic activities. Seasonal analysis of Gross Primary Productivity (GPP) and Net Primary Productivity (NPP) indicated significant variation among sampling stations. This study provides insights that can guide the implementation of mitigating measures to preserve the health of the backwater ecosystem. [ABSTRACT FROM AUTHOR]

Logjams create an upstream backwater of deepened, slower water, locally reducing bed shear stress. We compared hydraulic impact of logjam series across 37 geomorphically diverse reaches of mountain streams observed over 11 years in the US Southern Rockies. To enable reach‐scale comparison of logjam structure and spacing, we identified the modeled best‐fit effective resistance coefficient minimizing difference between outflow exiting a 1D channel with logjams present, and the same model channel with elevated channel resistance. Effective resistance increased with ratio of jam upstream depth to depth without a logjam, ratio of backwater length to average spacing, and decreased for randomly distributed jams due to close spacing, which reduced backwater impact. An analytic approximation and boundaries for region of relative spacing with steepest increase in effective resistance are provided. Our results can assist in targeting interventions to areas where hydraulic impact is greatest, providing value for money in nature‐based solution design. Plain Language Summary: In a river channel, logjams created by wood pieces create upstream backwater regions with slower, deepened water. By creating a backwater, logjams increase heterogeneity of habitat and sediment transport and increase connection between river channel and floodplain. We compared logjams in 37 reaches of mountain streams in the US Southern Rockies. The sites studied had high variation in logjam density, channel steepness, channel width, and floodplain width. To compare between reaches and identify the ability of logjam backwaters to slow water within a river channel, we found an effective channel resistance coefficient that produced similar model output as a reach containing a series of logjams. The effective resistance increased with ratio of jam upstream depth to flow depth without a logjam, and ratio of backwater length to average spacing. The highest rate of increase in effective resistance with more logjams in the river reach occurs for an intermediate range of inter‐jam spacing relative to backwater length. Engineered logjam and wood addition projects could target this range to provide the most benefit per intervention. Key Points: We compared the hydraulic impact of logjams, identified by effective resistance, across 37 reaches and 11 years in the Colorado RockiesEffective resistance increases with decreasing stream power, analytically linked to dependence on jam structure and spacingObserved random jam distribution reduces effective resistance compared to uniform distribution, due to backwater truncation [ABSTRACT FROM AUTHOR]

Copyright of Journal of Drainage & Irrigation Machinery Engineering / Paiguan Jixie Gongcheng Xuebao is the property of Editorial Department of Drainage & Irrigation Machinery Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Journal of Nanchang University (Engineering & Technology) is the property of Nanchang University and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The backwater lowland habitats of large rivers, like the Mississippi River in North America, present complex and often inaccessible environments for traditional capture-based fish biodiversity sampling. Our knowledge of the assemblages of the fishes that occupy such habitats is often incomplete, and this can compromise management efforts. We employed environmental DNA (eDNA) metabarcoding methods to sample a Mississippi River bottom wetland system to assess the ichthyofaunal diversity and the assemblage structure across habitat types, and we compared our results with capture-based survey records for the same habitats. We collected water samples in the spring and fall of 2022 from slough, ditch, shallow lake, and bayou habitats that varied in depth, vegetation, seasonal variability, and connectivity to the Mississippi River channel. We detected a diverse array of fish species that included 51 taxa. Nearly all the species previously documented in the habitats were detected using eDNA metabarcoding, and we increased the number of documented species by more than a third. Most of the species were ubiquitous across the range of habitats, but there was also a substantial assemblage structure, with some species exhibiting clear habitat specificity. Fall sampling was limited to the deeper bayou habitats where seasonal variation between the spring and fall was minimal. eDNA metabarcode sampling was demonstrated to be effective at detecting invasive species as well as uncommon species, which included several species of conservation concern. [ABSTRACT FROM AUTHOR]

Tributary- mouth channels of mountain rivers are affected by the game between the tributary and main stream, the water and sediment characteristics of which are characterized by both natural rivers and the reach affected by backwater from the main stream. Analyzing the water and sediment conditions of the tributary and main stream, the confluence characteristics, the backwater effects is of great significance for studying the tributary- mouth channel regulation. Taking mouth of Minjiang River as an example, a joint distribution function model of daily mean discharge during the recession period of Jinsha River and Minjiang River was constructed based on the Copula function theory and a function for the low water tributary- mouth channel formation was established using measured hydrologic and sediment data of Jinsha River and Minjiang River during 1960—2020. A quantitative method for determining the shoal-regulation stage of tributary-mouth channel was proposed. The study produced some important results: ① The annual runoff and sediment runoff showed significant decreasing trends, whereas the runoff during the dry season showed significant increasing trends in the Lower Minjiang River affected both by the large- scale development and construction of reservoirs in the upper reaches and human activities. ② The backwater effect of the Jinsha River on the mouth of Minjiang River was generally stronger during the flood season than that during the dry season which provided favorable conditions for scouring the channel during the period from the end of the flood season to the dry season and maintaining the mouth channel depth of Minjiang River. ③ The backwater height at mouth of Minjiang River increased with the increase of the confluence ratio, and there was a significant positive linear correlation between them. ④ The regulation stage should follow the principle of being 1. 5 meters above the designed minimum navigable stage in the fluctuant backwater zone upstream of Yangjiaoshi, and should gradually increase from 1. 5 to 2. 0 meters above the designed minimum navigable stage in the reach between Yangjiaoshi and Yangjiatan. [ABSTRACT FROM AUTHOR]

The piano key weir has been successfully used to address discharge deficiencies and site limitations for run-of-river structures and new and existing spillways, serving as an economical alternative to traditional weirs. In addition to upstream sedimentation, weirs may also be exposed to floating driftwood mobilized by hydrologic events. Driftwood accumulation immediately upstream of or on a weir crest can decrease hydraulic performance, potentially increasing upstream flooding and altering hydrodynamic forces on the weir that may cause structural or foundational concerns. It is unclear if floating driftwood accumulation might also influence the sediment self-cleaning characteristics of piano key weirs. Thus, this study used physical experiments to systematically investigate the sediment self-cleaning ability of a Type A piano key weir with driftwood accumulation in a run-of-river setting. The simulated substrate was an alluvial sand bed and the driftwood was naturally shaped. Experiments included combinations of discharge and different driftwood volumes. Results indicate that driftwood accumulations can have a significant influence on the flow field upstream of a piano key weir and positively affect the self-cleaning of sediment. For the conditions considered herein, the cleaning capacity was a function of driftwood volume, accumulation surface area or its extent in the upstream reach, and discharge. Higher flow rates and increased driftwood volume increased and extended upstream scour, resulting in higher sediment transport and self-cleaning without causing a significant backwater or increase in upstream water elevation. With sufficient flow depths at the piano key weir, driftwood would also be anticipated to pass downstream. Based on the results, driftwood accumulation can positively affect the ability of a piano key weir to remove adjacent upstream noncohesive sediment deposits. [ABSTRACT FROM AUTHOR]

Natural accumulations of wood, as well as engineered logjams, are relevant for river ecosystems. These structures, by interacting with the flow, can lead to significant backwater effects and morphological changes. Research on engineered logjams has so far mainly relied on physical modeling, which may impede the study of different flow conditions or logjam designs and configurations. Here, a simple approach for the simulation of logjams in two-dimensional depth-averaged hydrodynamic solvers is explored, building on widely available modeling options. The effect of logjams is included by combining a local contraction and an increase in local frictional losses based on the logjam characteristics, thereby reflecting the main physical flow processes in the region near a logjam. More than 350 modeling tests were used to calibrate and validate the proposed approach. For all tests, backwater rise due to channel- and partial-spanning logjams can be estimated with ±30% prediction range. Given its simple design, the calibrated model is not universal and requires careful evaluation when applying it to different setups. Nevertheless, a clear advantage of the proposed approach is that it uses tools that can be adopted in most of the standard two-dimensional hydrodynamic solvers. [ABSTRACT FROM AUTHOR]

The seasonal variation of physico-chemical parameters of backwater from Yashwant Sagar reservoir were investigated during 3rd January 2023 to 25th December 2023 by using standardised parameters to determine its quality. Seasonal values of water colour, odor, turbity, temperature, pH, total alkalinity, total hardness, dissolved oxygen, free CO2 were observed from 5 different stations of Yashwant Sagar dam backwater area of Karjat and Shrigonda are presented in this paper. It was found that physicochemical parameters of water were almost at optimum level. [ABSTRACT FROM AUTHOR]

Silver carp, Hypophthalmichthys molitrix, escaped into the Lower Mississippi River (LMR) over 50 years ago, established reproductive populations, and spread across much of the Mississippi River Basin. Demographic rates of silver carp are needed to inform decisions on control and management of this invasive species, but have not been published for the LMR. The purpose of this paper is to report silver carp age and growth estimates from fish collected in riverine (mainstem) and backwater (lake) habitats in the LMR during the period 2011-2019, to compare our results with populations from other geographic areas in the Upper Mississippi River drainage, and to evaluate latitudinal and habitat differences in demographic parameters. Silver carp gained weight with increasing length similarly throughout the lower and upper basin. However, annual growth rates were higher in the LMR compared to northern rivers including the Illinois, Wabash, Missouri, and Middle Mississippi rivers. In the LMR, regression analyses demonstrated that females were heavier in lakes than males or females in the mainstem and that females in lakes had the lowest instantaneous mortality (-0.186). Maximum age was 8 and 10 years for females and males, respectively. The largest male weighed 13.8 kg with a total length of 1022 mm, and was 7 years old. The largest female weighed 16.0 kg with a total length of 1034 mm TL, and was 7 years old. Rapid growth rates, larger sizes, and lower mortality in the LMR, in combination with limited commercial fishing, extensive river-floodplain connectivity, and vast amounts of spawning areas, ensure that LMR silver carp will continue to act as a source of fast-growing invasive individuals for other reaches and other rivers throughout the Mississippi River Basin. [ABSTRACT FROM AUTHOR]

Copyright of Nonferrous Metals (Mineral Processing Section) is the property of Beijing Research Institute of Mining & Metallurgy Technology Group and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Changes in fish habitat induced by dam construction in the downstream river have been well documented in an increasing body of literature. Fish habitats in the backwater zone of dams have undergone dramatic changes, which have still remained poorly understood. This study aims to provide a more complete understanding of fish habitat distribution and clarify fish habitat utilization patterns in the upstream dam in order to adopt effective remediation activities. This study was conducted in the Three Gorges Dam (TGD) as it is the world's largest installed capacity hydropower station, with a backwater zone length of about 660 km. Four major Chinese carp (FMCC) were selected as target fish species, and fish habitat distribution upstream of TGD was assessed by integrating the swimming ability and environmental preference of different fish species into their critical life stages. Assessment results at different life stages of the target fish species showed that June was a critical period for spawning activities FMCC in the fluctuating backwater zone of TGD. The riverbank was an important feeding habitat for FMCC, and the high‐velocity flow in the centre of the channel exceeded the limits of the swimming ability of target fish. The fish habitat distribution in the fluctuating backwater zone of TGD was heavily affected by runoff from April to September and by dam operation from October to March of the next year. This work provide valuable information about river conservation and management in the upstream of TGD. [ABSTRACT FROM AUTHOR]

Microplastics (MPs) are gaining global attention in recent years due to its widespread distribution and potential health impacts. The present study focuses on the distribution and characterisation of microplastics in the sediments and its transfer into the organisms living in Kavvayi and Kumbla backwaters of Northern Malabar region, Kerala, India. MP isolation procedures including density separation, organic matter digestion, and membrane filtration followed by visual and spectral analyses using optical microscope and confocal Raman spectroscopy have been utilised for the microplastic evaluation. Microplastics of size range up to 1 μm was analysed, and the presence of MPs was detected in all samples with an average abundance of 99.5 ± 69.43 particles/kg and 96.57 ± 29.96 particles/kg in Kavvayi and Kumbla backwaters respectively. Raman spectral analysis confirmed that almost 50% of MPs to be synthetic elastomers with the remaining half encompassed by polyamide, polyethylene, polyester, polyurethane, and polypropylene. Higher abundance of MPs in the edible aquatic organisms like clams, prawns, and fishes confirmed the transfer of MP from the environment into living organisms envisages the need of further investigation on toxicological impacts and management strategies. [ABSTRACT FROM AUTHOR]

Etheostoma fonticola (Fountain Darter) is federally listed as endangered and endemic to a single river basin in Texas, occupying stenothermal headwaters (22–23°C) of the spring-influenced San Marcos River and Comal River. Reported distribution is limited to the upper 6.4 river kilometers (rkm) of the San Marcos River, but a collection of a Fountain Darters farther downstream (11.5 rkm from the headwaters) in August 2022, along with visual observations of other small percids in the immediate area, prompted a preliminary assessment to document extent of the Fountain Darter's downstream distribution. Using seines to target mesohabitats (i.e., riffle, run, pool, backwaters) likely to contain Fountain Darters, we resampled the same site as the 2022 collection in April 2023 to assess overwinter survival. In June 2023, we sampled 5 sites located 10.2–19.0 rkm downstream from the headwaters. Between both sampling dates, we collected 243 Fountain Darters among 13 mesohabitats at 3 sites located 10.2–16.0 rkm downstream from the headwaters, including a mesohabitat with water temperatures reaching 29 °C. The occurrence and abundance of Fountain Darters in a reach of the San Marcos River within a more eurythermal environment offer a unique opportunity to assess population viability of Fountain Darters outside of a stenothermal environment, which in the past was considered to be a primary limiting factor in wider distributions of Fountain Darters. [ABSTRACT FROM AUTHOR]

Anthropogenically driven flow intermittency is increasing in freshwater streams, with important implications for the management and conservation of aquatic ecosystems. Because most freshwater fishes are mobile, they are expected to emigrate from intermittent reaches, but this may not be true in streams transitioning from perennial to intermittent. Here, we attempt to determine if riverine fishes vacate drying reaches before intermittency or remain in local refuges.We implemented a controlled, in situ experimental flow reduction resulting in intermittency, reducing flows from ~1.0 to 0 m3/s over a 3‐week period. We monitored fish and fish‐habitat changes over a 5‐week period before, during and after flow reductions.During flow reductions, total wetted habitat was ultimately reduced by 91%. Habitat loss over time was not equal among habitat types: pool habitat increased slightly as run habit was lost, and backwater and isolated pool habitats were not strongly related to discharge. Likewise, water depth in run habitats decreased faster than other habitats.Only the river carpsucker Carpiodes carpio appeared to move upstream during flow recession; seven other species remained within drying sites. Habitat loss negatively affected fish populations, but at a lower rate than that at which habitat was lost, until sites dried completely. Overall, two species, red shiner Cyprinella lutrensis and western mosquitofish Gambusia affinis, had increased population growth during the study, whereas the remaining species had population declines.Fishes were able to find transient local refuges during flow reductions but did not vacate sites before intermittent conditions. Accounting for lack of emigration from anthropogenic flow‐intermittent reaches will be important for designing conservation actions for fishes threatened by increasing flow intermittency. Creation of refuge habitats may not be effective for widely dispersed species that do not actively seek refuge habitats, unless those habitats support enough individuals to maintain resilience following the intermittent conditions. [ABSTRACT FROM AUTHOR]

The computation of hydrographs in large watersheds necessitates utilizing channel routing, which calculates the movement of hydrographs along channel branches. Routing methods rely on an implicit scheme to facilitate numerical resolution, which requires more computational time than the explicit scheme. This study presents an explicit scheme channel routing model that offers a versatile approach to open channel flow analysis. The model is based on mass conservation principles and Manning equations, and it can accommodate varying bed slopes, making it highly adaptable to diverse hydraulic scenarios. In addition, the proposed model considers backwater effects, which enhances its applicability in practical scenarios. The model was tested in a practical application on a rectangular channel with a width of 7 m, and the results showed that it can accurately predict outflow hydrographs and handle different flow conditions. Comparative analyses with existing models revealed that the proposed model's performance in generating water flow oscillations was competitive. Moreover, sensitivity analyses were performed, which showed that the model is highly responsive to parameter variations, such as Manning's coefficient, bed slope, and channel width. The comparison of peak flows and peak times between the proposed model and existing methods further emphasized the model's reliability and efficiency in simulating channel routing processes. This research introduces a valuable addition to the field of hydrology by proposing a practical and effective channel routing model that integrates essential hydraulic principles and parameters. The results of the proposed model (lumped routing) are comparable with the solution provided by the Muskingum–Cunge method (distributed routing). It is of utmost importance to note that the proposed model applies to channel branches with bed slopes below 6°. [ABSTRACT FROM AUTHOR]

Using a phenomenological approach, we analyse the voices of entrepreneurs living in the peripheral ecosystems of Newcastle Upon Tyne (UK), Palermo (Italy) and Perth (Australia). These ecosystems are defined by the considerable physical distance between their geographical location and the location of a larger, more established 'core' ecosystem in their nation. The purpose of our paper is to examine how distance from the core is perceived to both enable and constrain entrepreneurship in peripheral contexts. We introduce 'distance from the core' as a significant hitherto unexplored theme to consider when exploring the lived experiences of entrepreneurs in peripheral contexts. Empirically, we present data that affirms and expands extant findings revealing how entrepreneurs rooted in peripheral contexts react to the structural conditions around them. Methodologically, we demonstrate the value of phenomenological research in revealing the subjective ways entrepreneurial agency, structure and distance intersect. We highlight that policymakers must take the voices of entrepreneurs in a peripheral ecosystem into account when designing and implementing enterprise policies that aim to develop entrepreneurship in peripheral contexts. [ABSTRACT FROM AUTHOR]

This paper explores different methods of computing backwater depth for open-channel flow, such as one- to multi-dimensional models, finite difference approaches, and artificial intelligence methods. This paper primarily focuses on one-dimensional methods and states the implication, advantages, and disadvantages, verification process, and performance of each method. This paper discusses different parameters that influence backwater and their impact. Additionally, this paper compares the discussed one-dimensional methods with each other due to their common usage of experimental and field datasets as well as their popularity in implementation. It was concluded that while the WSPRO method significantly overestimated and the Yarnell’s method underestimated the afflux value, the measured afflux values are closest to the values computed by the energy and momentum methods.

The Jingjiang reach (JR) has experienced continuous and significant channel degradation after the Three Gorges Project operation. It is urgent to quantify the backwater effect caused by the confluence of the Dongting Lake, and the consequent impact of incoming flow- sediment regime on the channel degradation in the JR. Based on the measured hydrological data and data for channel degradation from 2003 to 2020, an empirical function for clarifying the relationship between the cumulative channel evolution amount and boundary conditions for the upstream and downstream of the studied JR reach has been established. In addition, the contribution of the backwater effect to the cumulative channel evolution amount was investigated. The results indicate that: ① The cumulative channel evolution amount in JR was positively correlated with the fluvial erosion intensity at the inlet, and it was inversely with the corresponding difference between the average water stages at the inlet and outlet. Therefore, the channel degradation in JR is the result of these two influencing factors. ② The empirical function derived could effectively represent the impact of the fluvial erosion intensity and differences between the average water stages of channel inlet and outlet on the cumulative channel evolution amount in JR (R 2 > 0. 92). ③ The cumulative channel evolution amount of the JR section from 2003 to 2020 was 1. 23 billion cubic meters. Under hypothetical conditions for the absence of the backwater effect caused by the Dongting Lake confluence, the cumulative channel evolution volume would increase by 67 million cubic meters. This indicated that a potential reduction in the cumulative channel evolution amount of nearly 5% was attributable to the backwater effect. At the same circumstance, the cumulative channel evolution volume in the upstream and downstream JR was 0. 73 and 0. 5 billion cubic meters, respectively. The backwater effect caused a reduction of the two values by about 1% and 16%, respectively. Therefore, the backwater effect decreased the channel evolution volume in JR and its influence on the channel degradation was more obvious in the downstream than that in the upstream. [ABSTRACT FROM AUTHOR]

The high contrast degraded underwater images often demand extensive pre-processing to attain reliable information for object detection and pipeline tracking. The prototype system developed employs CLAHE, a variant of adaptive histogram equalization, with an adaptive clip limit based on entropy. To yield an enhanced image, CLAHE is applied to the L* channel alone, resulting in improved L- CLAHE and better results. Validation of the improved L-CLAHE method is carried out using real-life underwater images captured using DTG2 Pro ROV from Kochi backwaters based on PSNR, SSIM, EPI, and PFOM quality measures and outperforms the conventional histogram equalization and adaptive histogram equalization techniques. These images are subjected to intensification and filtering for further enhancement as well as object detection and pipeline tracking applications. The proposed algorithm is compared with CLAHE, MSRCR, and L-CIF methods. The improved L-CIF algorithm has a high entropy value compared to the existing algorithms while the EME metric has been evaluated close to unity indicating the improved performance of the fast-guided filter. The method developed also helps in improving the average pixel intensity of the input images. [ABSTRACT FROM AUTHOR]

This paper presents the results of excavations at Glover Drive, Edmonton, at a site located on the west side of the Lea Valley. In the past the valley comprised a spread of shifting channels, most of which are now silted and buried. Excavations within the floodplain revealed a sequence of deposits relating to former channels. These provided evidence for the past environment, anthropogenic activities and management of the landscape from the Mesolithic period to the present. An unusual timber platform and two roundwood stake-built structures, dated by dendrochronology to shortly after AD 472, were found within a small channel on the edge of a sand bank in a backwater fen area. A series of ditches on the higher ground to the west of the structures were also tentatively dated to the Early Saxon period. The timber structures were probably short-lived as the site became inundated, leading to the wooden structures and ditches being buried beneath thick alluvial clay. The Early Saxon wooden platform is the first of its kind to be excavated, recorded and dated in England and the article discusses its possible function, placing it into its temporal and spatial context. [ABSTRACT FROM AUTHOR]

The main purpose of the construction of weirs is to raise the water level and control it in front of the weir. It is important to know the longitudinal section of the variable flow behind the weir in the open channels. A total of 30 experiments were conducted in a horizontal laboratory channel with a length of 12 m, a width of 0.5 m, and a depth of 0.45 m. The longitudinal flow section was evaluated follow a step-by-step process under the influence of five different slopes of the channel bottom with five different flow discharges (0.035, 0.028, 0.022, 0.016 and 0.012 m³/ sec), for each slope. After that, a Matlab simulation model was built in order to evaluate the longitudinal section of water surface, which is a plot of the water level along the length of the structure. The MATLAB Simulink gave more accurate results at speed that does not exceed seconds, as long mathematical equations. [ABSTRACT FROM AUTHOR]

Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) developed an analytical model to predict backwater rise by log jams, using the size and packing density of logs and the jam length, as well as river slope and bed roughness. We show that the model formulas can be rewritten using the Froude number instead of river slope and roughness, thus improving their applicability in engineering practice. The equation terms and results of Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) are found to be similar to those of the empirically derived formula by Schalko et al. (2018, https://doi.org/10.1061/(asce)hy.1943‐7900.0001501). However, some differences are identified, calling for further study. Most notably, these distinctions pertain to the effect of accumulation porosity, with additional minor differences in the exponent of the Froude number. Lastly, model implications for some broader applications are explored, showing a methodology to calculate the representative log size for log mixtures, and the expected effect of log orientation on backwater rise. Plain Language Summary: Accumulations of wood in rivers (log jams) can block the flow and thereby cause water level rise. Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) developed a theoretical model to predict how this water level rise depends on log jam properties and local river conditions. For the local river conditions, they used the river slope and bottom roughness. In this comment, we show that the Froude number can be used instead, with exactly the same result. The Froude number is a dimensionless number that depends directly on the local river conditions, making the adapted formula easier to apply in practice. The resulting formula shows good agreement with an earlier one based on experimental work by Schalko et al. (2018, https://doi.org/10.1061/(asce)hy.1943‐7900.0001501). Still, some differences were found that raise questions. Most notably, the formulas differ for the effect of accumulation porosity. This becomes especially clear when logs are packed closely together. Next, model implications for slightly different settings than those studied by Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) were explored. This showed how to determine the average log size for a mixture of logs with different sizes, and how the expected water level rise changes with log orientation. Key Points: Follett et al. (2020a, https://doi.org/10.1029/2020gl089346) predicted backwater rise by log jams using river slope and roughness. We show the Froude number can be used insteadBy using the Froude number, the link to the local river conditions becomes stronger, improving formula applicability in engineering practiceThe resulting formula is shown to be similar to earlier empirical work. But differences in jam porosity effects call for further study [ABSTRACT FROM AUTHOR]

Follett et al. (2020, https://doi.org/10.1029/2020gl089346) demonstrated that a large wood jam can be modeled as a porous obstruction with momentum loss proportional to the number, size, and packing density of the logs and jam length. Poppema and Wüthrich (2024, https://doi.org/10.1029/2023gl106348) incorporated uniform flow Froude number, broadening the scope of our work. Here, we demonstrate that Froude number can be directly introduced to equations in the main body of Follett et al. (2020, https://doi.org/10.1029/2020gl089346), without requiring uniform flow. Based on this, we show that a managed increase in upstream depth is possible for conditions below a critical discharge, in which equilibrium upstream depth over uniformly distributed jams can be adjusted with inter‐jam spacing. This design could retain water in low flow conditions, allowing jams to act independently above critical discharge. Finally, we suggest that log orientation can be included in our model by varying both drag coefficient and frontal area perpendicular to the flow. Plain Language Summary: Logjams can increase upstream water surface elevation, creating an upstream pool with slower, deeper water. We demonstrated that the increase in water depth upstream of a logjam is related to the number, size, and packing density of the logs and the jam length. In this Reply to a Comment by Poppema and Wüthrich (2024, https://doi.org/10.1029/2023gl106348), we clarify that our prediction of upstream water depth does not depend on river steepness and sediment size. We go on to show that a progressive increase in upstream depth is possible under some low flow conditions, if logjams are spaced closely enough so that each logjam is impacted by its downstream neighbor. This arrangement could be used to design nature‐based solutions for water retention during drought. In response to Poppema and Wüthrich (2024, https://doi.org/10.1029/2023gl106348), we clarify the observed agreement between our model and a similar model by Schalko et al. (2018, https://doi.org/10.1061/(asce)hy.1943‐7900.0001501) and suggest that the effect of log orientation can be included in our model by varying the drag coefficient in addition to the frontal area perpendicular to the flow. Key Points: Response to Comment by Poppema and Wüthrich (2024, https://doi.org/10.1029/2023gl106348), which re‐writes backwater rise equations in Follett et al. (2020, https://doi.org/10.1029/2020gl089346) using Froude numberFollett et al. (2020, https://doi.org/10.1029/2020gl089346) does not require river slope & roughness, as implied in Comment. We show use of Froude number with main text equationsA series of jams can generate a progressive increase in water depth, allowing for water storage during low flows below a critical discharge [ABSTRACT FROM AUTHOR]

Since the impoundment of the Three Gorges Project, the downstream hydrology and river dynamics have been modified. The Yichang–Chenglingji Reach (YCR), as a part of the mainstream of the Middle Yangtze River, has consequently been significantly scoured, which has resulted in stream trenching and section enlargements, without showing any obvious trend in flood level variation, however. This phenomenon can be caused by the increase in riverbed resistance due to river geomorphological change and bottomland vegetation development and the backwater effect of Dongting Lake. To investigate how these factors influence the flood water levels, this study analyzed the variations in the influencing factors based on observational data, theoretical analysis and mathematical modelling, including river channel scouring, riverbed resistance, and the influence of Dongting Lake backwater. Then, the impact of these factors on flood levels was evaluated, followed by a comparative analysis of the effects of various factors. The results show that both the flood backwater height (ΔZ) and the backwater influence range (L) are positively correlated with the outflow intensity (T) at the Chenglingji station. The backwater effect decreases gradually with increasing upstream distance, and the influence on the upstream reach can extend up to Shashi city. It was also indicated that the increase in riverbed resistance due to bottomland vegetation development and river geomorphology are dominant factors in inhibiting flood level declines in the YCR, while the backwater of Dongting Lake just affects local regions. This study can provide a better understanding of the flood level changes of the YCR and thus contribute to flood control and riverbank protection of the Yangtze River in the future. [ABSTRACT FROM AUTHOR]

Freshwater habitats display a high degree of heterogeneity in both space and time. This heterogeneity is a result of the hierarchical interplay of hydrology and geomorphology, producing the physical habitat template to which biological communities respond and interact. Thus, it follows that any effort to fully understand the complexity of these systems requires a spatial and temporal perspective of heterogeneity at multiple scales within a hierarchical framework. In this study we 1) test if fish assemblage structure differs between hydrogeomorphically distinct, off-channel patches of the Upper Mississippi River, USA, 2) identify which species are driving differences in assemblages between patch types and, 3) assess which hydrogeomorphic variables are associated with fish assemblages and if these are the same suite of variables responsible for the physical differentiation of patches. Different fish assemblages were associated with hydrogeomorphically distinct patches, importantly, sub-groups of backwaters. Species including the Bluegill Lepomis macrochirus Rafinesque, 1819, the Black Crappie Pomoxis nigromaculatus (Lesueur in Cuvier and Valenciennes, 1829), and the Gizzard Shad Dorosoma cepedianum (Lesueur, 1818) were influential in driving differences in assemblages. Fish assemblages did not respond to the same suite of hydrogeomorphic variables responsible for the physical character of patches, although there was some overlap. Instead, they responded to patch-scale characteristics and long-term hydrology and, in the case of backwaters, which navigation pool they were located in. We suggest that classification of hydrogeomorphic character across multiple spatio-temporal scales is critical. This classification should be done prior to sampling so patches can be targeted based on their physical character to draw out key habitat-assemblage relationships. We also contend that broad classification of habitats (e.g., floodplain lake vs backwater) may be too simplistic. Instead, individual characteristics defining the physical nature of a habitat need to be linked to biological responses across scales. A more nuanced understanding of these relationships is needed to improve restoration and management outcomes with respect to increasing or maintaining heterogeneity in the landscape. [ABSTRACT FROM AUTHOR]

Despite the widespread application of spur dikes in river training projects, the performance of the structure during flood events and its impacts on unsteady flow conditions have rarely been studied. In this experimental investigation, the influences of twelve unsubmerged unilateral and bilateral spur dike layouts on upstream flow conditions during flood movements were examined. Three hydrographs with varying unsteadiness intensities were generated and applied to all layout tests, including the no-spur condition for comparison purposes. The results revealed that discharge directly affected changes in flow depth upstream of the spur dike, while the flow rate trend exerted inverse influences. The Keulegan-Carpenter number was modified to assess the impact of unsteadiness intensity on the rating curve loop. Stage hysteresis analysis demonstrated an increase of more than thirty times compared to the no-spur scenario, highlighting the elevated risk of flooding in the upstream reach while delaying peak flood arrival time. This has implications for flood risk management and warning programs. The results underscore the significance of considering not only peak discharge but also unsteadiness intensity in spur dike design. [ABSTRACT FROM AUTHOR]

This is an article in the field of mining engineering. Ca2+ and Mg2+ are easily dissolved from fluorapatite and dolomite in the acid medium of reverse flotation, and there is a "cumulative effect" in the process of backwater circulation, which has an adverse effect on the flotation indexes. Taking fluorapatite, dolomite and quartz as the research objects, the effect of different recycle times of backwater on the flotation recovery of three single minerals was studied. The results showed that when pH value was 5, the recovery difference between dolomite and fluorapatite decreased from 72.21% to 64.19%, and the recovery of quartz maintained at about 10%; When the number of cycles reached 5, the recovery difference between dolomite and fluorapatite slightly increased to 69.74%, and the recovery of quartz slightly decreased to 11.22%. In this study, the mechanism of dissolved ions in backwater for three kinds of single minerals was revealed by measuring the number of dissolved ions, zeta potential of mineral surface and ions adsorption capacity of mineral surface under backwater circulation system.

This study evaluates the scenario of the flood backwater impacts on upstream of the Sunkoshi-Marin headworks. The design flood and hydrological analysis were carried out based on the stream flow data from 1968 to 2015 of Khurkot station. Probabilistic method was used to estimate design flood discharge and check flood values for 1000 and 10,000 years return periods frequency. Estimated design floods and check floods were 12,328 and 15,630 m3/s discharge respectively. Numerical simulation of backwater effects was carried out in three different cases- (i) headworks without affecting existing road (ii) headworks affecting existing road and (iii) headworks with inline structures using HEC-RAS. Water surface profiles estimation and backwater innundation map was generated for 1000 years return period flood. In the case (i) scenario simulated upstream and downstream water surface were 478.10 m and 477.22 m respectively. In the case (ii) those values were found 471.75m and 470.64 m respectively. Like wise, in the case (iii) scenario upstream and downstream water surface were found 475.79 m and 471.39 m respectively. The total inundated area including the river waterway was 340.89 ha with the extension up to 6 km in the Tamakoshi side and 8 km in the Sunkoshi side. The net inundation area excluding the river waterway was estimated 216.92 ha. The inundated areas lie within three rural municipalities, namely; Sunkoshi, Khadadevi and Manthali. Due to backwater innundation recommended length of the realigned section of the BP highway is about 1.3 kms.

Owing to extensive construction of dams, the impact of backwater on flow may lead to navigation or flood control issues in curved channels. To date, the impact of backwater on the water surface profile in curved channels remains unknown and requires investigation. In this study, experiments were conducted in a glass-walled recirculating flume with a length of 19.4 m, a width of 0.6 m, and a depth of 0.8 m, and the impact of backwater on the water surface profile in a 90° channel bend was investigated. The experimental results showed that the backwater degree had a significant impact on the transverse and longitudinal flow depth distributions in the bend. The transverse slope of the flow (Jr) increased linearly with an increase in the Froude number of the approach flow upstream of the bend. Jr increased with the longitudinal location parameter ξ when −0.2

In this study, a new empirical equation was established to predict the sedimentation volume resulting from the construction of a multi-purpose weir or low-head dam using experimental approaches. Applying the 1-D numerical model (STAFF), which is based on Exner's equation, 2545 cases were simulated and laboratory experiments were conducted with various sediment particle sizes, channel slopes, inlet discharge, and outlet water elevation. Short-term predictions were conducted through laboratory experiments with movable bed, and the results indicated that dimensionless unit stream power and the Shields parameter exhibited the most significant correlation with dimensionless deposition volume. In particular, we analyzed the phenomenon in which the backwater effect and reservoir delta. Using a multiple regression approach, the developed empirical equation was validated for predicting sedimentation in the upstream reservoir of the weir. [ABSTRACT FROM AUTHOR]

After the construction of reservoir, the uplift of the water level leads to changes in flow rate, water depth and sediment movement, which may also affect the habitat of fish and other organisms. In order to demonstrate the influences of reservoir construction on the siltation and hydrodynamic conditions of the spawning site area and by taking a power station in LC Basin as an example, this paper establishes 1D and planar 2D nested water and sand mathematical model to study the form and position of siltation in the spawning ground, the changes of the reservoir backwater, and the hydrodynamic conditions based on the recommended normal storage level and the operating water levels during the flood season. The results show that the distribution of sediment in the spawning area under the recommended scheme is basically the same as in nature, there is no mutation area in the sediment content, and the construction of reservoir has little effect on siltation in the area. After construction, the area of spawning ground with "flow rate meeting 1.0-2.0 m/s, water depth meeting 0.5-1.0 m" increases in each month from April to July, and the change rate ranges from 8.74% to 317.36%. Under the recommended scheme, the construction of the reservoir has little impact on the habitat and hydrodynamic conditions of the spawning site area at the end of the reservoir, and can still meet the demand of fish. The research results can provide a technical reference for similar engineering planning and design. [ABSTRACT FROM AUTHOR]

In the process of coal mining, the residual goaf will destroy the stress balance state of the overlying strata, which will result in a large number of fractures. The development of overburden fractures not only affects the movement of strata and the subsidence of surface, but also determines the dominant channel of gas, groundwater and other fluid migration. Therefore, this paper uses 3DEC software to simulate the temporal and spatial evolution of fractures in overlying strata during the mining of coal seam #15 in Pingshu Coal Mine, Qinshui Coalfield, and studies the fractal characteristics of mining overburden fissure development, then we use the drilling hole backwater method to verify the development height of mining-induced fractures. The results show that the overlying strata bend and collapse obviously with the advance of the working face. The development of overburden fractures shows very regular fractal characteristics, and the fractal dimension can be divided into four stages in time and two stages in space. The research results have guiding significance for mastering the law of overburden movement, accurately identifying groundwater and gas enrichment areas, and strengthening the prevention and control of mine water hazards and the effect of gas drainage. [ABSTRACT FROM AUTHOR]