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The Three Outlets Channel (TOC) consisting of three anabranching rivers formed due to natural avulsion by extremely high floods, is the primary water–sediment channel connecting the Jingjiang in the middle Yangtze River and Dongting Lake (the second largest freshwater lake in China). Since the impoundment of the Three Gorges Reservoir (TGR) in 2003, the decreasing diversion of runoff and sediment load of the TOC has an impact on the hydrological connectivity of the river–lake relation. Nonetheless, it lacks complete understanding on the diversion of runoff and sediment load, erosion and deposition amount, and the calculation method of diversion runoff in the TOC. We used remote sensing images, hydrological data, and channel topography to analyze the change in runoff and sediment load, channel morphology, local erosion and deposition amounts. The main results show that: (i) Meander cutoffs of the Lower Jingjiang accelerated the reduction process of the Ouchi River’s runoff and sediment load and the increase in the number of dry days. After the impoundment of the TGR, the diversion of sediment load of the TOC was greatly affected, but the decreasing trend of the runoff diversion slowed down. (ii) The morphological change of the inlet zone of Ouchi River is larger than that of Songzi River and Hudu River. The morphological evolution of the inlet area led to the change in the diversion of runoff and sediment load of the TOC. (iii) In the dry season, the water level drop in the inlet zone of the TOC leads to a decrease in the diversion discharge. Therefore, considering the water level drop and channel width adjustment in the inlet zone, five empirical formulae for the diversion discharge of the five hydrological stations in the TOC are proposed. These empirical formulae can be used as a short-term forecast for future changes in the hydrologic regime and the dynamics of the Jingjiang–Dongting Lake relation.

The distal reach of the Lower Jingjiang River (LJR) in the middle of the Yangtze River consists of five adjacent bends, among which the Qigongling Bend is a Ω-shaped meander with a mean sinuosity of 2.2 and the narrowest neck 525 m in width. This bend is slowly approaching neck cutoff owing to progressive bank erosion. An abnormal phenomenon has occurred in this bend since the Three Gorges Reservoir (TGR) began to operate in 2003 which is erosion in the inner bank zone and deposition in the outer bank zone. This problem has not been fully understood because of the interplay of changes in water-sediment, bank erosion, and artificial bank revetment. In this study, aerial and remote sensing images, hydrological data, channel topography, and an existing bank erosion model are used to reveal channel morphodynamics of this bend and the trend of the potential neck cutoff induced by bank erosion. The study results show that the clear water released from the TGR has provided by forcefully eroded the point bar of inner bank but failed to scour the outer bank due to the protection of bank revetment since the 1990s. Thus far, the outer bank zone near the bend apex has increasingly widened in conjunction with the formation of 2 emerging sand bars. Consequently, the thalweg of the main channel has laterally shifted toward the inner bank by roughly 800 m. More severely, the rate of bank retreat on the upstream side of the bend neck was about 4.5 m/yr in 2010–2019, but the downstream side of this neck was experienced slight deposition. Bank erosion could be accelerated by progressively increasing erosion and eventually trigger the occurrence of neck cutoff in the next few decades, thereby significantly altering the quasi-equilibrium regime of channel morphodynamics in the LJR. • Differentiated artificial revetments lead to inner bank erosion and two sand bars formation in outer bank zone. • Cross-section hydraulic geometry at the apex adjusted by lateral shift of the thalweg and progressive retreat of inner bank. • Neck cutoff of this bend may occur in the next 30–50 years without bank revetments. [ABSTRACT FROM AUTHOR]

Strong wind events frequently result in creating large areas of windthrow, which causes abrupt environmental changes. Bare soil surfaces within pits and root plates potentially expose soil to erosion. Absence of forest may alter the dynamics of water circulation. In this study we attempt to answer the question of whether extensive windthrows influence the magnitude of geomorphic processes in 6 small second- to third-order catchments with area ranging from 0.09 km2 to 0.8 km2. Three of the catchments were significantly affected by a windthrow which occurred in December 2013 in the Polish part of the Tatra Mountains, and the other three catchments were mostly forested and served as control catchments. We mapped the pits created by the windthrow and the linear scars created by salvage logging operations in search of any signs of erosion within them. We also mapped all post-windthrow landslides created in the windthrow-affected catchments. The impact of the windthrow on the fluvial system was investigated by measuring a set of channel characteristics and determining bedload transport intensity using painted tracers in all the windthrow-affected and control catchments. Both pits and linear scars created by harvesting tend to become overgrown by vegetation in the first several years after the windthrow. The only signs of erosion were observed in 10% of the pits located on convergent slopes. During the period from the windthrow event in 2013 until 2019, 5 very small (total area <100 m2) shallow landslides were created. The mean distance of bedload transport was similar (t-test, p=0.05) in most of the windthrow-affected and control catchments. The mapping of channels revealed many cases of root plates fallen into a channel and pits created near a channel. A significant amount of woody debris delivered into the channels influenced the activity of fluvial processes by creating alternating zones of erosion and accumulation. [ABSTRACT FROM AUTHOR]

Transverse drainages are prominent landscape features in active foreland thrust-and-fold belts. Understanding their response to folding processes is pivotal for comprehending landscape evolution and erosion-deformation interactions within the foreland. Here, we focus on the extensively developed transverse drainages across the Tugerming anticline in the southern Tian Shan foreland. Based on fold topography, drainage patterns, and various morphometric indices, we conducted a detailed geomorphological analysis of the Tugerming anticline. Our results suggest that the Tugerming fold laterally grows towards both ends, exhibiting notable segmentation along its strike. The westward lateral fold growth is characterized by interactions between the Tugerming anticline and two adjacent anticlines (Yiqikelike and Tuziluoke). At its eastern termination, lacking nearby folds, the Tugerming anticline laterally propagates without other adjacent folds, resulting in an elongated, gentle termination. Additionally, the hinterland catchment controls sediment and water flux of foreland transverse rivers, and its size has a significant influence on both channel morphology and river-fold interactions of the Tugerming anticline. Among the transverse rivers studied, those with large hinterland catchments (>80 km2) were dominated by braided river channels. In these cases, rivers respond to changes in channel gradient due to fold growth primarily through aggradation and degradation processes. Conversely, rivers with limited hinterland catchments (<80 km2) or originating within the fold, show a prevalence of incised meander channels. Moreover, channels accommodate gradient changes induced by the growing fold, primarily altering channel morphology, including channel sinuosity, slope, and width-to-height ratio. Our study reveals the significance of considering the hinterland catchment size in interpreting river-fold interactions and associated channel morphology within foreland transverse drainages. • We study transverse drainages in the Tugerming anticline in South Tian Shan foreland. • Geomorphic indices suggest lateral growth of the Tugerming fold towards both ends. • The lateral fold growth exhibits significant along-strike segmentation characters. • Hinterland catchment sizes affect channel morphology and river-fold interaction. [ABSTRACT FROM AUTHOR]

The formation of wetland channel networks on coastal river floodplains is affected by spatial transitions in tidal‐fluvial processes. This study evaluated sedimentation patterns in tidal marshes on the 147‐km tidal Columbia River and its 87‐km estuary and characterized the cross‐sectional geometry and planform morphometry of tidal wetlands along the estuarine to riverine gradient. Tidal marshes were predominantly depositional (median 0.7 cm yr−1, primarily silt), consistent with late‐Holocene rates. Marsh sediment accretion rate increased with annual maximum 7‐day average daily maximum water depth. Elevation was negatively correlated with accretion rate in the tidal river and positively correlated with total organic carbon (TOC%) in the tidal river and estuary. TOC% was greater in the estuary and, like percent fines, greater farther from the main‐channel Columbia River. For four single‐channel and six channel‐network planforms of tidal marsh, shrub‐dominated, and forested wetlands: (1) Spatial patterns of cross‐sectional morphology conformed to typical coastal wetland morphology in estuarine reaches up to the tidal river. (2) Reach‐based and common slope linear models for channel perimeter on wetland area were predictive in the estuary (R2 > 0.81) and differed between island (n = 144) and mainland (n = 164) wetlands. No planform linear models were predictive for the entire study area or the tidal river. No models for channel outlets were acceptable. (3) Channel perimeter, surface area, and outlets were all highly variable within and among estuarine–riverine reaches. Analyses of sediment, cross‐section, and planform support the use of a "natural network paradigm" for wetland‐restoration design on tidal river floodplains. Key Points: A new metric, the annual maximum of the 7‐day average daily maximum water depth, explains much variability of tidal river floodplain sedimentation rateIn the estuary, up to the tidal river, cross‐sectional morphology and planform channel network perimeter tend to conform to coastal processesOrganic carbon is positively correlated with elevation and with distance from the main river channel. It is highest in the estuary [ABSTRACT FROM AUTHOR]

Barak River is highly meandering rivers flowing through the alluvial plains of Assam in India. However, due to dynamic system, it is found that channel being subjected to regular shifting which creates uncertainty to the habitants residing nearby the river. Therefore, it is anticipated to carry out a study regarding changes in channel morphology and prediction of centerline channel migration during 1984–2030, using multiperiod Landsat remote sensing images along with autoregressive integrated moving average model (ARIMA). From morphometric analysis, it was found that the mean value of meander length (ML), meander width (MB), and meander ratio (MR) indicates an increasing trend, while sinuosity (C), wavelength (λ), and radius of curvature (RC) show a decreasing trend. The outcome of ARIMA model specifies that channel shifting of mid-line is going to change suddenly either to rightward or leftward directions. Throughout the whole alluvial part of the Barak River, rightward side is recognized as major concern. Observed and predicted values have shown a good R2 value (R2 = 0.89 and R2 = 0.88) at CS-30 and CS-18 respectively. Also, lowest RMSE is observed at CS-12 and highest RMSE is observed at CS-21. Finally predicted values were generated for the estimation of centerline channel shifting between two time intervals (2017–2023 and 2023–2030), which shows that the channel shifting of the river basin will occur at many regions particularly at critical sections. Overall, the findings of this study could be used further in river training works and in understanding the future dynamics of channel. [ABSTRACT FROM AUTHOR]

This paper uses flume experiments to investigate the influence of lateral width confinement on channel morphology, sediment sorting, and bedload transport. Three runs of about 60 hr were carried out under constant feeding rate equal to 0.6 l/s and 8 g/s, with a bimodal mixture of natural sediments, a fixed flume slope of 3%, and width imposed by lateral walls from 0.12 to 0.50 m in order to model three different flow confinement configurations. Despite the three runs transporting at the same rate on average, they presented different gravel‐bed river morphologies and different degrees of bed complexity. The three runs also presented differences in bedload transport rate fluctuations associated with different magnitude and mechanisms of bed storage and release of sediments. The intermediate width configuration (Run 2) was found to have a minimum storage and release of sediments compared with both the wider configuration (Run 1) and the narrower configuration (Run 3). Runs 1 and 3 were characterized by a significant storage and release of sediments resulting in a highly fluctuating bedload transport rate; however, while Run 1 (braiding morphology) stored and released sediments through lateral deposits and bed variations with planimetric sorting, Run 3 (single‐thread channel) stored and released sediments through variations in bed elevation accompanied by vertical sorting. We extrapolated this concept to the full set of gravel‐bed river morphologies, thus speculating about the channel morphology for optimal sediment transfer. Key Points: We perform flume experiments to represent poorly‐sorted gravel‐bed rivers with the same active channel width but different extents of lateral confinementChannel morphologies, geometries, sorting patterns, and bedload transport rates are strongly influenced by lateral width constraintsAmong the three configurations tested, the one with intermediate width confinement promotes a single‐thread to braided pattern and presents less variation in sediment transport rate [ABSTRACT FROM AUTHOR]

Redwood Creek is located in Sonoma County, California.  Redwood Creek is a tributary of Maacama Creek, a tributary to the Russian River.  The reach of Redwood Creek addressed in this study is on an alluvial fan.  In summer of 2001 the California Department of Fish and Game conducted a stream inventory to determine the presence of anadromous fish in the watershed and recommended Redwood Creek be managed as an anadromous, natural production stream.  Two restoration projects have been completed in recent years, the first in 2005 and the second in 2010.  In this study we investigated the newly constructed reach to determine how the channel morphology has responded after the first water year.  We conducted cross-sectional surveys  at 4 locations along the restoration project.  Survey results show that vertical channel adjustment is occurring, and that the channel is still in the process of finding geomorphic equilibrium.  It is likely that the channel will continue to adjust in future storm events.  Cross-section monitoring should proceed into the future to determine whether channel adjustments continue, and as a basis to determine the need for adaptive management.

AbstractPutah Creek (drainage area = 2,000 km2) drains the slopes of Cobb Mountain in Lake County, flowing 137 km southeastward into the Yolo Bypass near Davis, California. Lower Putah Creek, the 37km reach from the Solano Diversion Dam to the Yolo Bypass, is confined within a flood control channel.  Dry Creek (drainage area = 44km2) joins Putah Creek near Winters, California.  Putah Creek is regulated by water releases from Monticello Dam at Lake Berryessa.  Dry Creek flows only part of the year and has no dams. Southward channel migration of Putah Creek from the 1990’s was threatening Putah Creek Rd., a paved county road following the south bank of the evaluated stream-section.  The new location of the Putah Creek channel also reduced the amount of gravels entering Putah Creek from Dry Creek.  This was significant because dams reduced the amount of course sediment available from upstream, leaving Dry Creek as one of the only natural sources of the gravels important to the ecology of Putah Creek. In 2005, the Lower Putah Creek Coordinating Committee implemented a project to move the channel of Putah Creek northward to its approximate historical course.  The project included the removal of invasive giant reed (Arundo donax), in part because Arundo appeared to have contributed to the unwanted channel avulsion.  We evaluated the project performance towards the goals of 1. protecting Putah Creek Road, 2. keeping invasive plant species out of the area, 3. facilitating natural transport of Dry Creek gravels into Putah Creek, and 4. improving salmonid habitat.  Our evaluation found that 1. Putah Creek has stayed within the general path of the design channel and is not returning to the southern pre-1997 channel which threatened the road, 2. there is a mix of native plant species (e.g. willow, cottonwood) and invasives (e.g. Arundo, blackberry) in the floodplain, 3. There is no physical barrier separating Putah and Dry Creek, 4.  the channel and floodplain provide good habitat complexity for native fish, but fine sediments cover most of the potential spawning gravels.

Livestock grazing in the western United States has lead to riparian ecosystem and stream channel degradation. Establishing fenced-off exclosures is a common management strategy that aims to passively restore these areas, however, relatively few studies have assessed the evolution of exclosed reaches over time. We evaluated temporal trends in channel form and riparian vegetation along a 4.2 km reach of Long Creek (drainage area of 180 km2), a tributary to Sycan Marsh in western Lake County, Oregon. The Nature Conservancy implemented reduced livestock grazing along this reach in 1996 and complete exclosure in 1999. Based on previous studies that documented vegetation establishment and subsequent sediment accumulation on channel banks, we hypothesized that the channel would have narrowed and vegetation would have re-established after eleven years of cattle exclosure.   In October 2011, we surveyed seven previously-established cross sections and compared channel geometry in 2011 to surveys conducted since 1990. We also took photos at these locations and compared them to historical images. We found no consistent trend in channel morphology, but two cross sections demonstrated narrowing, one of which was likely driven by reduced flow velocity from a downstream beaver dam. Vegetation had successfully established along the streambanks, but in addition to the riparian species, upland lodgepole pines were also abundant along the channel and on the floodplain.  Our results suggest that beavers should be encouraged so their dams will increase overbank flow and discourage the invasion of upland plant species. We also propose improvements in monitoring methods to ensure repeatability of cross-sections over an extended monitoring period.

Wood accumulations are important morphological agents forming the character of high-gradient streams in the Moravskoslezské Beskydy Mts. The aim of the research is to define both the extent and character of the impact of wood accumulations on the streams. A total of 126 accumulations have been identified of the total wood volume of 503 m3 that is unevenly distributed within the studied streambeds. The wood volume in the studied streambeds is particularly dependent on the age and species composition of vegetation, channel morphology, and the geological bedrock resistance to the action of the stream, especially in forced alluvial reaches. The research revealed the deposition of fine-grained material immediately upstream of the wood accumulations, creating gravel bars and capturing fine organic debris. On the other hand, immediately downstream of the accumulations fine-grained fractions are carried away and coarser material is deposited, creating pools and plunge pools, evorsion potholes and bank scours. The research further showed a low intensity of the transport of woody material through the streambeds. The accumulations usually occur in the place where the stream has been dammed by a fallen tree member or in structurally predisposed streambed segments. As a result, discontinuities in energy and material flow occur that help to increase the streambed heterogeneity.

Summary: Tracer studies are a commonly used tool to develop and test Einstein‐type stochastic bedload transport models. The movements of these tracers are controlled by many factors including grain characteristics, hydrologic forcing, and channel morphology. Although the influence of these sediment storage zones related to morphological features (e.g., bars, pools, riffles) have long been observed to "trap" bedload particles in transport, this influence has not been adequately quantified. In this paper we explore the influence of channel morphology on particle travel distances through the development of a Bayesian survival process model. This model simulates particle path length distributions using a location‐specific "trapping probability" parameter (pi), which is estimated using the starting and ending locations of bedload tracers. We test this model using a field tracer study from Halfmoon Creek, Colorado. We find that (1) the model is able to adequately recreate the observed multi‐modal path length distributions, (2) particles tend to accumulate in trapping zones, especially during large floods, and (3) particles entrained near a trapping zone will travel a shorter distance than one that is further away. Particle starting positions can affect path lengths by as much as a factor of two, which we confirm by modelling "starting‐location‐specific" path length probability distributions. This study highlights the importance of considering both tracer locations and channel topography in examinations of field tracer studies. © 2020 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Patch‐burn grazing (PBG) can promote terrestrial heterogeneity and biodiversity, but can temporarily increase stream nutrients and ecosystem metabolism, and alter macroinvertebrate assemblages. The impacts of grazing on stream channel morphology and post‐PBG recovery patterns are unclear.We assessed the influence of grazing in PBG managed grassland streams in Missouri, USA, and subsequent recovery when grazing ceased for 2 years. We hypothesized that grazing would degrade water quality, stream biotic integrity and channel morphology, but that riparian fencing would mitigate these effects. We predicted that biological and chemical variables in unfenced streams would return to pre‐PBG levels within 2 years after grazing ceased, but channel morphology would not.Six small headwater streams (two in ungrazed control watersheds, two in PBG watersheds with 10 m fenced riparian zones and two in PBG unfenced) were sampled over 7 years; 2 years before PBG, 3 years during PBG and 2 years post‐PBG. We sampled macroinvertebrates and water chemistry monthly when water was present and surveyed channel morphology at least once each study period.During grazing, unfenced watersheds showed the greatest changes in channel width, depth and area. During the post‐PBG period, one of the two unfenced watersheds showed partial recovery of channel morphology. Although grazing increased concentrations of nutrients and chlorophyll‐a, concentrations returned to pre‐PBG conditions after grazing ceased, indicating recovery. Very fine organic sediments increased in the unfenced watersheds compared to the control during grazing but recovered afterwards. Contributions of Chironomidae to total invertebrate abundance increased in the unfenced watersheds during grazing, and then decreased during the post‐PBG period.Riparian fencing mostly mitigated effects of grazing on the streams. Unfenced streams were resilient to effects of grazing in a PBG managed grassland, with most metrics recovering within 2 years after grazing ceased, except for channel morphology.Synthesis and applications. Grazing in a patch‐burn grazed managed grassland coupled with riparian fencing could be an effective conservation tool for land managers of prairies, with relatively modest influences on stream water quality and biotic integrity. Persistent changes in stream channel morphology and effects of longer periods of grazing deserve further research. [ABSTRACT FROM AUTHOR]

We describe the joint dynamics of bedload transport and bed elevation changes with a stochastic population model, and we analyze (1) the dependence of bedload flux statistics on local bed elevations and (2) resting time distributions for sediment undergoing burial in the fluctuating sedimentary bed. The model involves entrainment and deposition in a control volume characterized by elevation‐dependent rates, and it exhibits a statistical regulation effect, whereby bed aggradation suppresses the variance of the bedload flux while degradation enhances it. This variance regulation effect is contingent on collective entrainment, whereby moving grains destabilize stationary grains in a positive feedback. When collective entrainment is turned off,bedload transport fluctuations become independent of the bed elevation. Return times from above in the bed elevation time series provide heavy‐tailed power law distributions of resting times with tail behavior characterized by the mean erosion rate and the active layer depth. These results imply bedload statistics measurements on relatively short timescales can be strongly biased by bed elevation changes when collective entrainment occurs, and they support the growing consensus that sediment burial generates heavy‐tailed sediment resting times that ultimately generate anomalous bedload diffusion. Key Points: Two‐species stochastic population model describes fluvial bedload particle activity and local bed elevationsModel predicts elevation‐dependent transport statistics and power law distributed resting times for sediment undergoing burialBed elevation changes modify particle activity fluctuations by up to 90%, and sediment burial generates anomalous bedload diffusion [ABSTRACT FROM AUTHOR]

Neck cutoffs and their resultant oxbow lakes are important and prominent features of riverine landscapes. Detailed field‐based research focusing on the morphologic evolution of neck cutoffs is currently insufficient to fully characterize cutoff evolution. High‐resolution bathymetric data were collected over 3 years for the purpose of determining channel morphology and morphologic change on three actively evolving neck cutoffs. Results indicate the following general trends in morphologic adjustment: (1) a longitudinal bar in the upstream meander limb that develops near the entrance to the abandoned bend; (2) a deep scour hole in the downstream meander limb immediately downstream of the cutoff channel; (3) erosion of the bank opposite the cutoff in the downstream meander limb; (4) a cutoff bar in the downstream meander limb at the junction corner of the cutoff channel and the downstream meander limb; and (5) perching of the exit of the abandoned bend above the cutoff channel due to channel bed incision. The results presented herein were used to develop a conceptual model that depicts the morphologic evolution of highly curving neck cutoffs. The findings of this research are combined with recent analyses of the three‐dimensional flow structure through neck cutoffs to provide a mechanistic explanation for the morphodynamics of neck cutoffs. © 2019 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

The area between the river and its surrounding vegetation constitutes the riparian zone which produces woody debris (WD) that modifies the fluvial dynamics. The WD is constituted by branches and trunks deposited in the river channel. One of the ways that WD can modify the geomorphology of the river is to form steps and pools (step-pool system). In this way, the objective of the present study was to perform a literature review on woody debris in rivers and, to identify the main focus used in research on the occurrence and monitoring of these materials. It was observed that the WD can be found as individual pieces or forming accumulations, and that there is a tendency among the researchers to analyze the diameter and length of the pieces, obtaining the total volume in length of river. There is a gap regarding the woody debris management in Brazil, because only one biome (Atlantic Forest) was included in the few researches carried out. The knowledge of WD dynamics can be surely used in the future in the watersheds management and for rivers renaturalization. [ABSTRACT FROM AUTHOR]

This paper presents insights from a flume experiment investigating the relationship between rate of bedload transport exiting a reach of a braided, sand-bed channel and the channel's braid intensity. The self-forming nature of the anabranches (sub-channels forming the braided channel) meant there was little direct control over the morphology of the braided channel. A comprehensive dataset was obtained relating rate of bedload transport and a braiding parameter, W/B, used to characterize braid intensity; W = width of actual water flow, and B = flume width. As W/B increased, the rate of bed-sediment transport decreased. However, spatial and temporal variations in sediment transport rate and channel morphology complicate this relationship. The clarity of the relationship improved when values of W/B were determined closer to the location where sediment transport was measured. Local morphologic features, such as sheet flow and antidunes, are shown to influence braid formation and thereby affect bedload transport. [ABSTRACT FROM AUTHOR]

A recent study reported considerable sediment trapping by three large channel bars downstream 18–28 km of the Mississippi–Atchafalaya River diversion (commonly known as the Old River Control Structure, ORCS) during the 2011 Mississippi River flood. In this study, we analyzed 3-decadal morphological changes of the 10-km river channel and the three bars to elucidate the long-term effects of river engineering including diversion, revetment and dike constructions. Satellite images captured between 1985 and 2015 in approximate 5-year intervals were selected to estimate the change of channel morphology and bar surface area. The images were chosen based on river stage heights at the time when they were captured to exclude the temporal water height effect on channel and bar morphology. Using a set of the satellite images captured during the period of 1984–1986 and of 2013–2014, we developed rating curves of emerged bar surface area with the corresponding river stage height for determining the change in bar volume from 1985 to 2013. Two of the three bars have grown substantially in the past 30 years, while one bar has become braided and its surface area has shrunken. As a whole, there were a net gain of 4,107,000 m2 in surface area and a net gain of 30,271,000 m3 in volume, an equivalent of approximately 36 million metric tons of sediment assuming a bulk density of 1.2 t/m3. Sediment trapping on the bars was prevalent during the spring floods, especially during the period of 1990–1995 and of 2007–2011 when large floods occurred. The results suggest that although revetments and dikes have largely changed the morphology of the channel and the bars, they seem to have a limited impact on the overwhelming trend of sediment deposition caused by the river diversion.

It is necessary to understand the evolution of a river channel when reconstructing its evolution process and analyzing the controlling factors essential for river management and ecological restoration. In the past 50 years, the ecological environment around the Yongding River has deteriorated considerably, and the downstream has been completely cut off. Despite this, few have studied its morphology. In this study, we analyze the morphology of the Yongding River (Beijing, China) stretching for 92 km in four different periods between 1964 and 2018. A data treatment is carried out based on GIS, and the morphological evolution trajectory of the river channel at the overall and reach scales is reconstructed. The results show that the river morphology has undergone significant changes: the channel width has narrowed by 31%, and the temporal and spatial patterns show significant differences. By analyzing the impacts of human activities and climate change in various periods, we find human intervention to be the most important controlling factor. Based on our results, we proposed a set of river restoration strategies and protection measures for the Yongding River to guide watershed management and land planning.

A history of land clearance and riparian tree and wood management has resulted in limited riparian woodland and wood along British rivers. However, river management approaches are now being promoted that 'work with natural processes' to reduce flood risk through measures intended to restore, protect and emulate the natural function of catchments, rivers, estuaries and coasts. Wood has started to be reintroduced into river channels during river restoration and natural flood management activities, but this needs to be undertaken using appropriate quantities, locations and designs that mimic natural tree‐wood features. This paper reviews the knowledge that is needed to support wood reintroduction activities including (i) the characteristics of the riparian tree species and wood that are present; (ii) the importance of river size relative to that of trees and wood pieces; and (iii) the way trees, wood and geomorphic processes interact across rivers and floodplains of different energy and style. [ABSTRACT FROM AUTHOR]

The Paraguay River is one of the main modeling agents of the Pantanal environment, its hydromorphological changes are linked to its water regime its river dynamics and anthropic activities. The present study aimed to evaluate the hydrosedimentological aspects and the level of environmental degradation from the application of protocols for the rapid evaluation of rivers - Pars, between the Bay of Palha and Sadao in the river corridor Paraguay. For the development of the research was used some steps. Office work, fieldwork and laboratory work. At the cabinet stage, bibliographical research, cross-sectional profiles and data organization were carried out in the field work, observation; implementation of rapid river assessment protocols; bathymetry and flow velocity, water and sediment sample collection. In the laboratory analysis Analyzes were carried out: granulometric (total dispersion and sieving method), evaporation method (sediment concentration). The Rapid Assessment Protocols indicated regular situations for the left margin of sections 1 and 5. In the cross sections on the Paraguay River, flow velocity ranged from 0.30 to 0.71 m / s, the mean depth of the water sheet between 3.5 to 8.16 m, the flow rate was between 141.90 to 865.57 m³ / s, the solid discharge varied from 245.20 to 1496, t / day. In the sections located in Palha bay flow velocity ranged from 0.09 to 0.97 m / s, the mean depth of the water slide was between 0.46 and 7.06 m, the flow rate was between 0.29 and 673, 95 m³ / s, and the solid discharge ranged from 53.74 to 2.329,17 t / day. The anthropic use directly influenced changes in the study area in question, but the dynamics of changes in the Paraguay River occur naturally disfiguring their features through sedimentological depositions. [ABSTRACT FROM AUTHOR]

Abstract Low-tech rock check dams are widely used to address land degradation; however, assessments of their impacts on runoff and sediment are lacking and are often limited to the first few years after construction. In 2008, two small (4.0 and 3.1 ha) instrumented watersheds located 300 m apart on an alluvial fan on the Santa Rita Experimental Range in southern Arizona were treated with 37 porous, loose rock check dams. Ten years after construction, the watersheds are experiencing contrasting responses to treatment. The ratio of runoff to precipitation was higher after check dam construction on one watershed and lower on the other, but not significantly in either case. Statistically significant changes in peak runoff rate are not detectable 10 years after construction at either watershed. However, a statistically significant reduction in sediment concentration was found on one watershed and no change was found at the other. The check dams have altered channel grades. However, backfilling of the dams is nearly complete on one watershed and the other has remaining capacity. The alluvial fan setting poses a complex restoration environment due to high sediment loads that deposit in response to vegetated areas of accumulated sediment creating conditions for channel avulsion and new incising concentrated flow paths. Check dams have a lesser impact on watershed outlet runoff and sediment than on internal watershed channel morphology and vegetation establishment. With monitoring and maintenance, check dams can be an effective tool for grade stabilization, but watershed restoration requires additional practices to address degraded interfluve areas. Graphical abstract Unlabelled Image Highlights • Proximal watersheds treated with check dams experience differing process responses. • Watershed outlet measurements may not represent internal watershed response. • Check dams may create new concentrated flow paths and incision on alluvial fans. • Watershed restoration must address both channel and interfluve degradation. [ABSTRACT FROM AUTHOR]

Five field tracer experiments and relevant detailed investigations of physical characterizations were conducted to investigate the effects of channel geomorphic settings on nitrate uptake efficiency on a 310-m long geomorphically distinct stream reach in a headwater agricultural stream in Hefei District, Lake Chaohu Basin. The model-fitted parameters from the one-dimensional transport with inflow and storage model were used to estimate the transient storage metric ( F med 200 ) and determine the total nitrate uptake coefficient (k) for the study reach. And then, a nutrient spiraling approach was applied to reach-scale nitrate uptake estimates (Sw, Vf, and U). The results showed that the main channel was the major contributor to nitrate uptake retention, and the higher geomorphic complexity might result in better nitrate uptake efficiency. The partial least squares regression (PLSR) analysis showed strong correlations between the independent variables as geomorphic settings, Reynolds number and transient storage, and the dependent variables as nitrate uptake metrics, which further underscored the importance of stream physical characteristics on measurement of stream nitrate uptake. [ABSTRACT FROM AUTHOR]

Abstract Along their fluvial to marine transition zone, tide-dominated river deltas show upstream to downstream trends in channel width, sinuosity, and depth, which at present have been only partially reported. This review article aims to describe these morphological trends from five modern tide-dominated river deltas using original data collected from satellite images and bathymetric maps and published data from field surveys. All the studied channels show similar trends with two distinct tracts separated by areas of morphological changes. The upstream tracts are characterized by constant width, relatively high sinuosity, and seaward-increasing depth, and are mainly controlled by the fluvial dynamics. The downstream tracts are characterized by seaward-increasing width, relatively low sinuosity, and seaward-decreasing depth, and are mainly controlled by the tidal dynamics. The delineation of this morphological configuration of the channels is crucial to understand the responses of deltas to the interacting riverine and marine processes. Additionally, this has important implications for depositional and hydraulic models, and for the long-term evolution and the assessment of human-induced versus natural modifications of these systems. [ABSTRACT FROM AUTHOR]

Hydrologic exchange flows (HEFs) across the river‐aquifer interface have important implications for biogeochemical processes and contaminant plume migration in the river corridor, yet little is known about the hydrogeomorphic factors that control HEFs dynamics under dynamic flow conditions. Here, we developed a 3‐D numerical model for a large regulated river corridor along the Columbia River to study how HEFs are controlled by the interplays between dam‐regulated flow conditions and hydrogeomorphic features of such river corridor system. Our results revealed highly variable intra‐annual spatiotemporal patterns in HEFs along the 75‐km river reach, as well as strong interannual variability with larger exchange volumes in wet years than dry years. In general, the river was losing during late spring to early summer when the river stage was high, and river was gaining in fall and winter when river stage was low. The magnitude and timing of river stage fluctuations controlled the timing of high exchange rates. Both river channel geomorphology and the thickness of a highly permeable river bank geologic layer controlled the locations of exchange hot spots, while the latter played a dominant role. Dam‐induced, subdaily to daily river stage fluctuations drove high‐frequency variations in HEFs across the river‐aquifer interfaces, resulting in greater overall exchange volumes as compared to the case without high‐frequency flows. Our results demonstrated that upstream dam operations enhanced the exchange between river water and groundwater with strong potential influence on the associated biogeochemical processes and on the fate and transport of groundwater contaminant plumes in such river corridors. Plain Language Summary: River stage fluctuations due to upstream dam operations enhance water exchange between rivers and aquifers. These exchange flows can stimulate biogeochemical processes in the subsurface. Here, we developed a 3‐D numerical model to simulate the flow and transport in a flood plain aquifer within the Hanford Reach, a free‐flowing section of Columbia River (WA). Our simulations revealed large spatial and temporal variability in exchange flow magnitude and direction in response to different river flow conditions. Furthermore, river channel morphology and subsurface geology together controlled the locations of high exchange flow rates. Our study provides important insights on the behavior of groundwater contaminant plumes in the river corridors of large regulated river systems. Key Points: Hydrologic exchange flows across the riverbed show strong intra‐annual spatiotemporal patterns as well as interannual variabilitiesHot moments of HEFs are controlled by magnitude and timing of river stage fluctuationsHot spots of HEFs are primarily controlled by the thickness of the underlying highly permeable sediment layer [ABSTRACT FROM AUTHOR]

Abstract In mountainous torrents of the Mediterranean environment the riparian vegetation is strongly influenced by the presence of engineering control works, since these structures bring heavy modifications in channel geometry, hydraulic regime and bed sediment size. Previous investigations have shown high linear correlations between physical (section shape, profile slope, specific discharge, surface and subsurface size of the channel bed) and vegetation (development, structure and biodiversity) indicators in headwater channels with check dams of Calabrian (Southern Italy) torrents. Based on these findings, this study applies multivariate statistical techniques (Principal Component Analysis and Partial Least Square Regression) to identify in the same study headwaters new synthetic explanatory variables, representative of the different transects (upstream, downstream or intermediate, compared to the check dam location) and develop predictive models of riparian vegetation characteristics. The Principal Component Analysis has provided a simple parameter (the first Principal Component, explaining about 60% of the total variance), which is able to discriminate the physical and vegetal characteristics of the different transects close to check dams, thus reducing the large number of factors influencing the fluvial processes. Moreover, cover, height and transversal variability of riparian vegetation have a very high influence (loadings over 0.73) on this component, while its biodiversity is correlated to the second Principal Component (loadings over 0.63). The Partial Least Square Regression has shown that it is possible to estimate with fair accuracy (minimum r2 of 0.70) the development, structure as well as transversal variability of the riparian vegetation, starting from the physical features of the channel. These models may be important in the planning steps of new check dams, since their effects on the development and growth of vegetation upstream and downstream can be forecasted before their installation, at least for the quantification of the order of magnitude of the check dam impacts on torrent ecology. Graphical abstract Unlabelled Image Highlights • Synthetic indicators identify physical and vegetation characteristics close to check dams. • Channel geometry, bed sediment size and riparian vegetation depend on transect location. • Changes in physical and vegetal parameters are less significant among torrents. • PCA identifies a new synthetic indicator of physical and vegetation characteristics. • PLSR provides predictions of the vegetation characteristics close to check dams. [ABSTRACT FROM AUTHOR]

We used space-for-time substitution, correlation, and regression analyses to study the effects of urbanization age on stream channel variables from 19 low-order urban watersheds in the southern Piedmont of the United States. The results are used to address questions regarding which variables are most responsive to urbanization age, the duration of response relative to system size, and changes in adjustment rate over time. Few morphological variables were found to be well correlated with metrics of urbanization age. The maximum-width/maximum-depth ratio (Wmax/Dmax) exhibited the best correlations to multiple metrics of urbanization age, with all correlations positive. A dearth of young urbanization ages in our dataset makes mathematically derived response times and end states for Wmax/Dmax highly uncertain. Inferences from the age range that is better represented suggest that the period of major response has occurred within the first three decades following urbanization. Subsequently, gradual increase in Wmax/Dmax appears to continue over 40 or more years. Response of channel form to urbanization and time elapsed in these low-order Piedmont streams is constrained by the presence of resistant bedrock below streambeds, a circumstance addressed by recent channel evolution models. [ABSTRACT FROM AUTHOR]

Injection molding is one of the main techniques for manufacturing microfluidic chips. As an important stage, the demolding process in injection molding will directly affect the quality of the functional unit of microfluidic chips (polymer microchannels), thus limiting the realization of its functions. In this study, molecular dynamics (MD) simulations on the demolding process were carried out to investigate the influence of diamond-like carbon (DLC) coating on the channel deformation. The channel qualities of polystyrene (PS), polymethyl methacrylate (PMMA), cyclic olefin copolymer (COC) and polycarbonate (PC) were analyzed after demolding with nickel (Ni) and DLC-coated mold inserts, respectively. In particular, the non-bonded interfacial interaction energy, elastic recovery and gyration radius of polymer molecular chains were further studied. The results showed that the non-bonded interfacial interaction energies could be significantly reduced by DLC-coating treatment on the mold insert. Moreover, common channel defects such as molecular chain separation, surface burrs and necking did not occur. The treatment of DLC coating could also significantly reduce the change in the gyration radius of polymer molecular chains, so the morphology of the polymer channel could be maintained well. However, the change in the elastic recovery of the polymer channel was increased, and the opening width became larger. In a word, DLC-coating treatment on the mold insert has great application potential for improving the demolding quality of injection-molded microfluidic chips.

The impacts of channel morphology on the residues and ecological risks of 14 polychlorinated biphenyl (PCB) congeners in water and sediment were investigated in summer (July) and autumn (September) in the Chahe River, in Nanjing, China. The residual concentrations of tri-chlorobiphenyls (tri-CBs, PCB 18) and tetra-CBs (PCB 52) in water were significantly higher than those of penta-CBs to deca-CBs, and the average residual concentration of ∑PCBs (sum of 14 PCB congeners) in summer was about six times higher than in autumn. However, the residues in sediment did not change significantly. Redundancy analysis (RDA) indicated that channel morphology and the corresponding environmental indices had significant impacts on PCB residues and their composition profiles in water and sediment. The overflow weir and lake-type watercourse may remarkably reduce the residual concentration and ecological risks of PCBs in water. The highest reduction percentages of the residual concentration and ecological risks of ∑PCBs induced by an overflow weir were 78% and 67%, respectively, and those induced by a lake-type watercourse were 36% and 70%, respectively. The watercourses with different channel morphologies were ranked by residual ∑PCBs concentrations in the following descending order: the natural ecological watercourse, vertical concrete watercourse, and vegetation-type riprap watercourse. However, they were ranked by residual ∑PCBs concentrations in sediment in the following descending order: the vertical concrete watercourse, vegetation-type riprap watercourse, and natural ecological watercourse.

Study area is situated 8 km south of the Bakkhali Island, West Bengal of India and its subaqueous environment influenced by the fluvial processes such as Hooghly River in west and its distributary like Muri Ganga in the centre and Saptamukhi River in the east. To understand the submarine behavior of these channels and associated meiobenthos, total of 28 sediment samples have been studied in detail. The study reveal that a total of fifteen species of recent benthic foraminifera belonging to 13 genera under 11 families were present and their distribution mainly controlled by channel morphology and sediment character. Based on the distribution of these benthic foraminiferal species, two assemblages have been identified. First assemblage, observed within the Hooghly and Muri Ganga channel, where salinity is comparatively low and sediment is mainly dominated by silt and clay. The most dominating benthic foraminifers of this assemblage are Ammobaculites agglutinans, Cribrostomoides jeffreysii and Asterorotalia trispinosa. Whereas, second assemblage mainly comprise of A. trispinosa, Ammonia beccarii, Asterorotalia spp., Elphidium excavatum, Elphidium crispum and Ammonia tepida noticed over the sand bars and adjoining shallow area. Keywords: channel morphology, Muri Ganga, Hooghly, sand bar

In mountain streams possible negative impacts of check dams on soil, water and riparian vegetation due to check dam installation can be noticed. In spite of the ample literature on the qualitative effects of engineering works on channel hydrology, morphology, sedimentary effects and riparian vegetation characteristics, quantitative evaluations of the changes induced by check dams on headwater characteristics are rare. In order to fill this gap, this study has evaluated the effects of check dams located in headwaters of Calabria (Southern Italy) on hydrological and geomorphological processes and on the response of riparian vegetation to these actions. The analysis has compared physical and vegetation indicators in transects identified around check dams (upstream and downstream) and far from their direct influence (control transects). Check dams were found to influence significantly unit discharge, surface and subsurface sediments (both upstream and downstream), channel shape and transverse distribution of riparian vegetation (upstream) as well as cover and structure of riparian complexes (downstream). The actions of the structures on torrent longitudinal slope and biodiversity of vegetation were less significant. The differences on bed profile slope were significant only between upstream and downstream transects. The results of the Agglomerative Hierarchical Cluster analysis confirmed the substantial similarity between upstream and control transects, thus highlighting that the construction of check dams, needed to mitigate the hydro-geological risks, has not strongly influenced the torrent functioning and ecology before check dam construction. Moreover, simple and quantitative linkages between torrent hydraulics, geomorphology and vegetation characteristics exist in the analysed headwaters; these relationships among physical adjustments of channels and most of the resulting characteristics of the riparian vegetation are specific for the transect locations with respect of check dams. Conversely, the biodiversity of the riparian vegetation basically eludes any quantitative relations with the physical and other vegetal characteristics of the torrent transects. [ABSTRACT FROM AUTHOR]

The present paper utilizes entropy to investigate variability in the surface areas of sandbars distribution of the Brahmaputra River, India. The intensity entropy disorder index (IDI) was computed for the dry and the post‐monsoon season for a selected reach of the river. The planform disorder index (PDI) was computed to represent the annual scale planform change due to seasonal flood. Finally, annual monsoon and peak flood stream power were evaluated and related to PDI. The results showed that the intensity disorder index followed a decreasing trend in dry and post‐monsoon seasons; tending towards lower deviation from a uniform distribution. It was noted that except for extreme flood years the PDI trend correlated well with monsoonal stream power. Distinctive trends in stream power were also observed in the present study. © 2018 John Wiley & Sons, Ltd. The present study utilizes entropy method to investigate variability in sandbars distribution of the Brahmaputra River, India. [ABSTRACT FROM AUTHOR]

Abstract Large ice blocks containing enough sediment to be denser than sea water form in the Minas Basin of the Bay of Fundy, Canada. Ice block composition and the timing of ice block formation were monitored to improve understanding of the potential threat to tidal power generators posed by collision with ice blocks. Field studies were carried out in 2012 and 2013 in the Kennetcook River, which is a tributary of the Minas Basin of the Bay of Fundy. In 2012, the cross-sectional area of the channel at the study site decreased by 21% due to the formation of ice walls. In 2013, it decreased by 24%. Large ice blocks separated from the ice walls during spring tides following a time lag of the minimum air temperature. The time lag was 20 days in 2012 and 21 days in 2013. Eleven percent of samples from ice blocks were denser than sea water. Highlights • Ice block composition and formation were monitored in Canada's Bay of Fundy. • In 2012 ice walls caused a channel's cross-sectional area to decrease by 21%. • Ice walls collapsed into ice blocks lagging spring tide and air temperature minimum. • 11% of ice block samples were denser than sea water due to sediment content. [ABSTRACT FROM AUTHOR]

The Alaknanda River is the most significant parental river of Ganga and forms an 11.5 km long and 2.5 km wide valley, locally known as the Srinagar Valley. The purpose of the present study is to highlight the recent landform changes in the Alaknanda channel course after the Kedarnath disaster, 2013. The Kedarnath flood completely changed the channel morphology of the Alaknanda river. The river changed its course at Srikot, SSB and Sriyantra Tapu with lower terraces being silted by sands at Ranihat, SSB, Bhaktiyana and Sriyantra Tapu. A new depositional terrace also formed opposite to Sriyantra Tapu. New lateral channel bars, braided channels, back swamp, rapids, pools and river souls were identified in the channel course of the river. Shifting of the channel course at Chauras still remains a serious problem for the Garhwal University Chauras Campus. About 2-5 m silt was deposited on the lower terrace at SSB, and ITI. The Srikot river bed was appended to 4.60 m. Shifting of channel course remains a serious threat to the Srinagar valley. Urbanization, sand and boulders mining, construction of dam, hydrological canal, road and settlements are the prominent example of anthropogenic activities which affect the shifting channel. [ABSTRACT FROM AUTHOR]

Abstract: Understanding large wood (LW; ≥1 m long and ≥10 cm in diameter) dynamics in rivers is critical for many disciplines including those assessing flood hazard and risk. However, our understanding of wood entrainment and deposition is still limited, mainly because of the lack of long‐term monitoring of wood‐related processes. The dataset presented here was obtained from more than 8 years of monitoring of 1,264 tagged wood pieces placed in 4 low‐order streams of the Chilean mountain ranges and was used to further our understanding of key factors controlling LW dynamics. We show that LW displacement lengths were longer during periods when peak‐flow water depths (Hmax) exceeded the bankfull stage (HBk) than in periods with Hmax ≤ HBk and that these differences were significantly higher for smaller wood pieces. LW length and length relative to channel dimensions were the main factors governing LW entrainment; LW displacement lengths were inversely related to the ratio of piece length to H15% (i.e., the level above which the flow remains for 15% of the time) and to the ratio of H15% to bankfull width. Unrooted logs and LW pieces located at the bankfull stage travelled significantly longer distances than logs with attached rootwads and those located in other positions within the bankfull channel. A few large logjams were broken during the period of observation, and in all occasions, LW from these broken logjams did not travel over longer distances than other pieces of LW moved in the same periods and in the same stream segments. Most importantly, our work reveals that LW dynamics tend to be concentrated within a few reaches in each stream and that reaches exhibiting high wood dynamics (extensive entrainment, deposition, or repositioning of LW) are significantly wider and less steep than less dynamic reaches. [ABSTRACT FROM AUTHOR]

Based on the foundation of the channel form evolution process in the lower Yellow River and the analysis on the cause of formation of first-level and secondary-level suspended rivers, aiming at the issues of wide river dike fixation, narrow river dike fixation and protective embankment, the sediment dispose is the key to manage the downstream of the Yellow River. The beach area in downstream of the Yellow River still need to detent the flood and desilting for a long period. Narrow river dike fixation and protective embankment could cause the worse situation of the secondary-level suspended river which jeopardizes the safety of the Yellow River. In order to achieve the objectives of flood control and design by grades, sedimentation in separated areas and the water and sediments can be freely exchanged between beach and channel in the floodplain area, guarantee the flood control safety in the downstream of the Yellow River, build the ecological space of the cities along the river, promote the development of floodplain area and achieve the success both in river management and the people's benefits, on the base of absorption of the results from the management of the river, a new method of the ecological management in downstream was proposed, which was to divide the floodplain area into different functions, such as resettlement area for the ecological immigrant, effective agriculture area and resources development and utilization area, with the methods of sediment elimination and dredging the river, to improve the main channel into high beach, second beach and tender beach with diverse flood control standards. [ABSTRACT FROM AUTHOR]

Bankfull discharges play a pivotal but underappreciated role in determining submarine channel morphometrics and architecture. This hypothesis is suggested by the power law relationship between channel morphometrics and discharge and the logarithmic relationship between channel architecture and discharge. We apply this relationship to the Rio Muni deep-water channels of Equatorial Guinea in three ways. Firstly, relatively dilute turbidity currents with a relatively low discharge of ca. 1.1 × 10 4 to 6.9 × 10 4  m 3 /s tended to enhance channel confinement and thalweg deposition, but to discourage lateral spreading of the flow. This, in turn, reduced depth and sinuosity ( SI ) of the channel form as the fill aggraded, as previously reported for younger channels on this slope. These vertically aggraded channel belts [represented by relative angles of channel trajectories ( T c ) ranging from 47.2° to 81.0°] are narrower (averaging 634 m), thinner (averaging 23 m), and straighter (mean value of SI  = 1.17) than their laterally migrated counterparts. Secondly, turbidity flows with a relatively high discharge of ca. 4.1 × 10 4 to 15.8 × 10 4  m 3 /s appear to have reduced channel confinement, but to promote thalweg erosion and lateral spreading of the flow. This, in turn, increased depth and sinuosity of the channel form as it laterally migrated, forming laterally migrated channel belts (represented by a relatively low T c of 21.8° to 49.0°) that are wider (1.5×), thicker (2×), and more sinuous (1.2×) than their vertically aggraded counterparts. Thirdly, a gradual decrease of discharge through time likely drove an architectural transition from lateral migration to vertical aggradation and associated migrating-to-aggrading channel trajectories. [ABSTRACT FROM AUTHOR]

Freshwater mussels of the order Unionida provide important ecosystem functions and services. Unfortunately, some previously widespread species are now seriously endangered. To restore the historical range of the population of Unio crassus in the Biała River, southern Poland, the species was reintroduced into a series of ‘stepping stones’ joining two remnant populations. During the first phase of the study, the relationships between the abundance of U . crassus , physical habitat, and water quality were studied to assess reintroduction potential. In general, chemical water quality improved upstream from the existing population, favouring the decision for reintroduction, whereas morphological variables worsened. Mussel abundance was correlated negatively with the elevation and slope of channel, organic matter contents, and pH (exceeding 8.0), but positively with silt presence, water conductivity, and concentrations of HCO 3 − , Ca 2 + , and NO 3 − . During the second phase, adult individuals were introduced into one type of functional habitat—marginal channel sectors with still water and fine sediment. Despite the initial very high rate of reproduction in some parts of the upper reach of the river, the juveniles were ultimately recruited only in the lower part of the restored range, resulting in a very rapid change in recruitment at a channel slope of 1.8‰. Recruitment was positively related to silt content, conductivity, and Ca 2 + and HCO 3 – ions, negatively to channel elevation and slope, and water pH. The host fish species showed no correlation with abiotic habitat features within the studied reach. These results imply that most of the habitat traits related to U . crassus occurrence depended on the river's longitudinal profile, not on the chemical water quality, and that final success of introduction should be evaluated after several years. [ABSTRACT FROM AUTHOR]