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Changes in river cross-section morphology have decisive influences on the flood discharge and sand transport capacity of rivers; thus, these changes strongly reflect the vitality of a river. In this paper, based on the river cross-section and water and sediment data of two different periods (1974–1987 and 2007–2021), the trend analysis, change-point analysis and sediment rating curve method were used to analyze the change process of river cross-section morphology and its response to streamflow and sediment changes in the main river stream of the Yellow River at the Longmen hydrological station. From 1974 to 1987 (except in 1977), the riverbed experienced siltation, and the riverbed elevation rose. Conversely, from 2007 to 2021, the riverbed experienced scouring, and the riverbed elevation gradually decreased. The cross-section shape changed from rectangular to U-shaped (deeper on the right side) at the Longmen cross-section. The changes in streamflow and sediment processes significantly impacted the evolution of river cross-section. Streamflow (P < 0.05), sediment discharge (P < 0.01), and the sediment load coefficients (P < 0.01) decreased significantly. The relationship between the water depth and sediment load coefficients followed a power function. The decreasing trend in sediment discharge was significantly stronger than that in streamflow. Suspended sediment particles tended to become finer. The sediment rating curve indicates that the sediment supply from upstream decreased while the erosive power in the river channel increased, leading to a gradual decline in riverbed elevation at the Longmen cross-section from 2007 to 2021. These findings help us better understand the impacts of ecological restoration on changes in river streamflow and sediment during river evolution. [ABSTRACT FROM AUTHOR]

Engineers, geomorphologists, and ecologists acknowledge the need for temporally and spatially resolved measurements of sediment clogging (also known as colmation) in permeable gravel-bed rivers due to its adverse impacts on water and habitat quality. In this paper, we present a novel method for non-destructive, real-time measurements of pore-scale sediment deposition and monitoring of clogging by using wire-mesh sensors (WMSs) embedded in spheres, forming a smart gravel bed (GravelSens). The measuring principle is based on one-by-one voltage excitation of transmitter electrodes, followed by simultaneous measurements of the resulting current by receiver electrodes at each crossing measuring pores. The currents are then linked to the conductive component of fluid impedance. The measurement performance of the developed sensor is validated by applying the Maxwell Garnett and parallel models to sensor data and comparing the results to data obtained by gamma ray computed tomography (CT). GravelSens is tested and validated under varying filling conditions of different particle sizes ranging from sand to fine gravel. The close agreement between GravelSens and CT measurements indicates the technology's applicability in sediment–water research while also suggesting its potential for other solid–liquid two-phase flows. This pore-scale measurement and visualization system offers the capability to monitor clogging and de-clogging dynamics within pore spaces up to 10,000 Hz, making it the first laboratory equipment capable of performing such in situ measurements without radiation. Thus, GravelSens is a major improvement over existing methods and holds promise for advancing the understanding of flow–sediment–ecology interactions. [ABSTRACT FROM AUTHOR]

The article discusses the transformation of Quarantine Bay in Louisiana due to the growth of a channel connecting the river to the bay, leading to the creation of a new delta. Scientists are studying the sediment flow and land-building process in the area, with differing perspectives on the source of sediment. Conservation groups welcome the new land formation, while shipping companies are concerned about the impact on river currents. The article also highlights the decline of Phragmites reeds in the Bird's Foot delta due to environmental changes, posing challenges for local communities and wildlife. [Extracted from the article]

This study is the first to quantify the migration processes of riverine microplastics under different connectivity contexts based on the spatial variation characteristics of microplastic loads. Microplastics in multidammed, single-dammed, and nondammed rivers are significantly different in three categories: abundance, flux, and inventory. Artificial damming can lead to multicategory reorganization of riverine microplastics, including size, polymer type, shape, and color. Artificial damming has led to the formation of microplastic hotspots in river waters and sediments due to reduced river mobility. Notably, low-velocity regions in non-dammed rivers are high hotspot for microplastic deposition, and their inventories may even be 10.63–12.71 times higher than those of other riverbeds. Additionally, results based on microplastic abundance differ significantly from those based on microplastic loads, which in some cases even showed contradictory results. Therefore, future studies must incorporate microplastic loads into the assessment to enhance our understanding of the fate of microplastics in river systems. [ABSTRACT FROM AUTHOR]

Sediment entrainment formulations developed for noncohesive materials have been widely applied to determine suspended loads in fluvial environments. Most relations were developed based on laboratory experiments and field measurements taken in sand-rich environments. Due to the accidental discharge of mine tailings in riverine systems, it is imperative to develop new approaches to predict sediment entrainment and resulting near-bed concentrations, as field observations show that the primary mode of transport for tailings once they are eroded is in suspension. Based on laboratory experiments conducted with poorly sorted iron tailings samples in an annular flume, we found that existing sand-based relations predict relatively well equilibrium near-bed concentrations when treated as well-sorted material. However, to predict entrainment rates into suspension for the tested poorly sorted iron tailings samples, sand-based entrainment relations require adding two functions accounting for the relative roughness of the bed material and the Reynolds particle number for the effect of viscous sublayer thickness on entraining fine grains. This innovative approach, combining dimensional analysis, similarity parameters, and experimental observations in an annular flume, provides a general framework for developing formulations to estimate the flow conditions necessary to entrain into suspension and then transport tailings either accidentally released into riverine environments or resuspended during dredging operations in watercourses. [ABSTRACT FROM AUTHOR]

Levee setbacks can create space for side channels, reduce flood impacts, and provide environmental benefits. Guidance is needed on how side channel design affects geomorphic changes over time. This paper explores application of existing research on natural and forced side channels to a levee setback with side channel on the White River (Washington). The side channel maintained a high bifurcation angle into the setback for 2 years. High flows then reset the bifurcation to a lower angle. Flow and sediment volumes and deposition patterns from each 2-year period matched results from existing studies for either a high or low angle. Application of existing research insight into expected flows and sediment patterns was dependent on a static bifurcation angle. In this case study, because the entrance area did not restrict the bifurcation angle and the flow regime included high flows, the bifurcation angle could adjust to maintain the side channel. Designing a large setback entrance enabled the channel to self-adjust to maintain flow and sediment transport into the side channel without the need for engineering intervention. [ABSTRACT FROM AUTHOR]

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Summary The Ségognole 3 shelter lies within a quartzitic sandstone megaclast in a lag deposit in the Paris Basin. It displays a female sexual configuration associated with a horse engraving, stylistically attributed to the Upper Palaeolithic. Recent studies have demonstrated that modifications to the natural features of the shelter had been undertaken to cause water to flow through what is seen as the vulva. New investigations reported here describe additional modifications to natural features in the shelter to direct rainwater infiltration to a network of channels engraved onto the shelter floor to form a functioning representation of watercourses. The carved motifs and their relationship with natural features in the sandstone of the shelter can be compared with major geomorphological features in the surrounding landscape. The engraved floor is not quite a map but more like a model in miniature of the surrounding landscape, potentially a world‐first 3D‐model of a Palaeolithic territory. [ABSTRACT FROM AUTHOR]

Constructed levees are designed to protect anthropogenic developments from destructive flooding events, but their construction has reduced groundwater recharge, increased flood risk severity under levee failure, increased the incision of river channels, and deteriorated riparian habitat. To reverse these impacts, levee setbacks are often designed to reduce flood risk and provide the opportunity to restore ecohydrological function, while groundwater recharge is rarely considered because it may require relatively detailed groundwater system analysis. In this study, we evaluated 100 heterogeneous hydrogeology realizations to estimate recharge with high-conductivity pathways (HCPs) under varying flood flows for a range of levee setback distances to identify the trade-offs in groundwater recharge and floodplain habitat. We find that on a regional scale, total recharge potential increases with setback distance, with the largest gains up to 1,400 m where there are outcropping HCPs and sufficient flow to inundate more of the setback area. In contrast, the recharge per unit area (i.e., the average daily recharge divided by setback area) generally decreases as levee setback increases, but there are local increases in the recharge per unit area at 1,400 m where HCP recharge may sufficiently offset the larger area. There is a median 10%–40% reduction in peak streamflow with increasing setback distance, which would aid flood risk reduction, but the increased area leads to decreasing depth due to flow losses and increased spreading of flood water. Ultimately, the decision for levee setback distance will depend on local conditions and management goals, as we find that increasing recharge will reduce the floodplain depth necessary for ecosystem function. Our results highlight the opportunity to consider groundwater recharge benefits in levee setback feasibility studies in semi-arid regions impacted by floods and groundwater overdrafts so that setback distance designs can achieve integration of flood risk reduction, riparian habitat, and groundwater recharge. [ABSTRACT FROM AUTHOR]

The paper presents a historical overview of the development of hydrological models in the former USSR and Russia since the 1930s. An overwhelming number of hydrological papers were published in Russian, and they are not sufficiently well known to the world hydrological community. The purpose of the review is to fill the gap and present the main achievements, some of which were pioneering for their time. The period under consideration is divided into three sub-periods. Pre-computer, the 1930–1950s were associated, first of all, with the development of models of unsteady water flow in river channels and linear flood-routing models; in the 1960–1980s, many theoretical and practical foundations for modelling the processes of the hydrological cycle and the formation of river runoff were developed; and in the Russian era, following 1991, several notable advancements in the considered field were also made. [ABSTRACT FROM AUTHOR]

From 2021 to 2022, extensive excavations at the Hebosuo site uncovered large building foundations, roads, river channels, ash pits, wells, and tombs. A vast array of artifacts including numerous slips and boards, stamp seals, and objects made of bronze, iron, bone, and stone or jade were unearthed. The site's timeline predominantly spans from the Western to the Eastern Han dynasties. These findings substantiate the historical establishment of the Yizhou Commandery during the Western Han period. Particularly significant are the stamp seals and slips and boards, which reveal the administrative structure and operations of the Yizhou Commandery. These discoveries are crucial for understanding governance and ethnic integration in the southwest frontier during the Western and Eastern Han dynasties. [ABSTRACT FROM AUTHOR]

Recent observations document increased abundance of algae in the headwater streams of Hubbard Brook Experimental Forest (HBEF). It is possible that this “greening up” of HBEF streams may be due to climate change, with rising temperatures, altering terrestrial phenology, and shifting hydrologic regimes. Alternatively, stream “greening” could be from the slow recovery of stream chemistry after decades of acid rain, which has led to rising pH, declining concentrations of toxic Al3+, and low solute concentrations. Four years of weekly algal measurements on artificial moss and ceramic tiles, along with six nutrient enrichment experiments, revealed new insights about the interactions between these two autotrophs. We found that in protected weir ponds and in stream channels, algal biomass was higher on artificial moss substrates than on tiles—with this effect amplified in the stream channels. These results suggest that bryophytes can provide physical protection from flood scour or may trap nutrients to support algal growth. In stream channels, algal biomass was higher in well‐lit habitats and time periods indicating strong light limitation. We only measured nitrogen and phosphorus limitation of algal biomass in nutrient enrichment experiments conducted within weir ponds, with higher light availability and lower flow. By comparison, results from the remaining four instream experiments provided little evidence for nutrient limitation, with only one trial showing increased algal growth in response to nutrient addition. The most striking implication of our study is the role of bryophytes in providing refugia, and potentially nutrients, to algae in shaded and oligotrophic headwater streams. [ABSTRACT FROM AUTHOR]

The editorial reviews ten articles on water resource management, hydrological modeling, cycles, and prediction. The papers address water balance, hydrological modeling, prediction, and the impact of human activity on river flow changes. The articles provide insights into implementing new water management methods, supported by case studies from various regions. The research highlights the importance of understanding hydrological cycles and forecasting for effective water management in the face of climate change and human impact. [Extracted from the article]

Flooding of water, sediment, and driftwood and its associated landform changes often occurs downstream of debris-flow deposition zones in small, mountainous river basins. This type of flooding occurs due to a sudden decrease in the sediment transport capacity of river channels, resulting in considerable damage. Despite the significant need for appropriate countermeasures to mitigate damage, it has been a challenge to plan and implement these across all river basins at risk of these hazards. However, if a simple but reliable tool is available to identify hazardous areas in advance, this would be extremely useful for prioritizing such areas and designing and implementing the required measures. To this end, this paper examines the geomorphic characteristics of recent flood events in Japan and proposes a method for identifying hazardous areas due to inundation by flood flows with sediment. We first explain the occurrence of sediment inundation by focusing on longitudinal changes in sediment transport capacity using the geomorphic indicator defined as the product of the drainage area A and bed slope i. In addition, we investigate the longitudinal profiles of the sediment transport capacity along the study channels using a one-dimensional governing equation for flood flows and, based on the results, discuss that finding that the computed longitudinal profiles of the sediment transport capacity are consistent with the longitudinal distribution of the A i . Our findings indicate that the A i is an effective indicator for identifying areas prone to inundation by flood flows with sediment. [ABSTRACT FROM AUTHOR]

The article begins with a test of the assumption that the size of the total catchment area of watercourses of the same order (according to Horton–Strahler) is a constant part of the study area, this size is the same for all orders. This assumption follows from Horton ratios, and Horton law proposed earlier gives the size of this part. Our GIS measurements on the DEM of the Far East confirmed this assumption. A hypothesis is proposed about the uniform distribution of watercourses between watercourses of higher orders. This hypothesis, combined with the established constancy of the catchment area, made it possible to formally describe how watercourses are distributed among watercourses of higher orders. The obtained formulas made it possible to analytically describe: Tokunaga coefficients; distribution of the catchment area of watercourses of one order between catchment areas of subsequent orders; formation of the catchment area of watercourses of one order from catchment areas of previous orders; the total catchment area of direct runoff into watercourses of each order. Our direct measurements, as well as the experimental data of other researchers, confirmed the results obtained analytically. It has been suggested that these patterns—both the constancy of the total catchment area and the distribution of this area over larger catchment areas—are not related to the ordinal organization of watercourses, but are dictated by the scale of watercourses. We obtained very close experimental results by distributing watercourses into sections of the same scale not with the help of a system of orders, but directly according to their catchment area, on the basis of whether it falls within a given range of values. It is likely that the hypothesis of a uniform distribution of watercourses between watercourses of a larger scale can be formulated without mentioning orders. The statements in the article are of a statistical nature; they are carried out in the measurements over large areas and for scales with a large number of watercourses. [ABSTRACT FROM AUTHOR]

Lowland rivers flowing through the loess rocks carry large quantities of suspended materials and experience active processes of channel deformation (meandering). A large number of shoals, as a result of sediment deposition, exist in the riverbeds. Shoals often change, especially during the period of high water. Such rivers do not have stable hydrological profiles, and so satellite estimates of their water content are of great practical interest. During the period of low water, the morphology of the riverbed is relatively stable and the shoals are in a semisubmerged state. Under these conditions, the proportion of flooding of shoals is very sensitive to the river water level, which creates favorable conditions for the development of satellite methods for assessing water levels. The study examined the Ili River in Central Asia with an annual outflow of about 12 km3, which is main tributary of the large Lake Balkhash. The informative value of Sentinel-2 data (resolution 10 m) in the task of assessing water level in the river in conditions of relative low water was shown. 179 cloudless Sentinel-2 satellite images were selected for the period from April to November 2018–2022. An additional criterion for choosing the image was the water level at the Ili-Dobyn hydropost of Kazhydromet less than 280 cm. This water level was typical for about 80% of the time of the low-water period of 2018–2022. The Ili riverbed on the border of China and Kazakhstan with a length of about 40 km was used to create the shoal (sediments) mask with a total area above 4 km2. The MNDWI1 (Modified Normalized Difference Water Index) water index and its threshold value of +0.25 were used to identify the "water" class on the shoal mask. The proportion of flooded shoals was compared with ground data from the Ili-Dobyn hydrographic station on the water level during the satellite's flight. For the April–November period, linear dependences were obtained between the proportion of shoals flooding and the river water level. The reliability of the linear approximation for seasonal data was high and varied from R2 = 0.83 (2022) to 0.96 (2020). The entire period (2018–2022) of the analysis was characterized by R2 = 0.93. The use of the linear regression equation as a model for predicting the water level in the river based on the proportion of flooding of test shoals provided a sufficiently high value (0.74) of the Nash–Sutcliffe hydrological forecasting efficiency parameter, which indicates the practical significance of the developed methodology. [ABSTRACT FROM AUTHOR]

Coastal infrastructure projects, particularly the modification of coastal river channels, are becoming increasingly significant to economic activities worldwide as a response to climate-driven changes and urbanization. The benefits of channel modification projects can be realized quickly, but the altered movement of sediments in the river channel can lead to unintended geomorphic changes years or decades later. An example of this is the closure of the San Bernard River mouth, located on the central coast of Texas, which was clogged with sediments by the 1990s as a result of two major projects in the area: the diversion of the Brazos River channel (1929) and the construction of the Gulf Intracoastal Waterway (GIWW) (1940s). The objective of this study was to a) document the delayed geomorphic response to the projects using a GIS analysis of historical maps and aerial imagery, and b) provide a snapshot of altered flow pathways in the area using measurements collected in situ. Results showed that the GIWW was the main conduit for river flow as it bisects the San Bernard River 2 km inland of its river mouth, reducing discharge in the terminal limb of the river. Due to reduced flow, the river mouth became clogged with wave-transported sediment supplied by the still-adjusting Brazos River which had been diverted to within 6 km of the San Bernard River. With a limited connection to the sea, altered sediment and flow pathways have led to numerous hazards and costly corrective dredging projects surpassing $12 million to date. Optimizing the cost-effectiveness of channel modification projects requires considering their long-term impact as managers continue to adapt to ever-changing coastal zones. [ABSTRACT FROM AUTHOR]

Energy utilization is increasingly significant for heterogeneous wireless multi-hop systems. Energy utilization models are progressively powerful in giving the usefulness of convention. The ECRTA model offers the chance to look at the effect of different physical layers and MAC layer parameters. To accomplish energy utilization in heterogeneous multi-hop networks, an energy utilization model that portrays the performance of the hubs is required. The ECRTA model for heterogeneous multi-hop networks conveys upgrading highlights, for example, giving dependable information transmission, expended energy for information packet transmission and measure of received information packets. The model has now become progressively well known in wireless communication environment. The performance of novel ECRTA model is examined and the outcomes are simulated utilizing Riverbed modeler 17.5 test system device. The presentation of the proposed ECRTA model is compared with Energy Aware Power Aware Multi-Access with Signaling (PAMAS) Protocol, Maximum Residual Packet Capacity (MRPC) and Minimum Total Transmission Energy Routing (MTTPR) by changing the size of information packets and mean Received Signal Strength Indicator (RSSI). [ABSTRACT FROM AUTHOR]

The riverbed and riparian zone are the hotspots of nitrogen removal in rivers. Denitrification plays an important role in the process of nitrogen removal. In this study, sediments from the straight channel riverbed and point bars were examined using indoor culture and acetylene inhibition techniques. The primary focus was to investigate the differences in denitrification rates between these sediments. The secondary focus was on the effects of temperature and carbon-nitrogen (C/N) ratios on the denitrification process. The results showed that denitrification rates were higher in point bar sediments compared to those in the straight channel bed. Denitrification rates were also higher in the near water area of the point bar than in the near bank area. Denitrification rates at 30 °C were significantly higher than at 10 °C for each sediment group as well as in samples having carbon and nitrogen amendments. Notably, when the C/N ratio was 2.5, the denitrification rate for samples with carbon and nitrogen additions was significantly higher than for samples without them. On average, denitrification rates increased by 2.56 times, 2.73 times and 2.87 times for sediments from the straight channel, inner part of the point bar, and near bank of the point bar, respectively. At the same time, the number of denitrifying bacteria was found to be higher in the point bar than in the straight channel. These findings highlight the beneficial role of point bars in accelerating sediment denitrification rates and emphasize the potential for increasing nitrogen removal capacity in rivers by optimizing temperature and C/N ratios. Changing the diversity of riverbed geomorphology, temperature and C/N can effectively enhance the nitrogen removal capacity of river ecosystems. [ABSTRACT FROM AUTHOR]

This paper describes the rehabilitation of Daly's (Shakey) Bridge, an existing single-span suspension bridge crossing the northern channel of the River Lee in Cork city. The bridge was opened in 1927 to replace an earlier ferry crossing at the same location. Daly's Bridge is included on the Record of Protected Structures and the National Inventory of Architectural Heritage. It remains the only suspension bridge in Cork city and is the only surviving bridge of its kind in Ireland. It is a significant contributor to the architectural heritage of the city. This paper describes the special inspections and structural assessments, site investigations and material testing, detailed design of repair works and particular aspects of construction and monitoring. The bridge is a well-known local landmark and its colloquial name 'Shakey Bridge' derives from the lively movement of the deck under pedestrian loading. A key aspect of the project included modelling and measurement of the dynamic response of the structure prior to and following repair works to confirm that the signature shake was retained. The project also incorporated approach upgrades and ancillary works, including new approach parapets, the repair of existing cast-iron railings, lighting, landscaping, surfacing and invasive species removal. [ABSTRACT FROM AUTHOR]

River width is a crucial parameter that correlates and reflects the hydrological, geomorphological, and ecological characteristics of the channel. However, the width data with high spatial resolution is limited owing to the difficulties in extracting channel width under complex and variable riverine surroundings. To address this issue, we aimed to develop an automatic framework specifically for delineating river channels and measuring the bankfull widths at small spatial intervals along the channel. The DeepLabV3+ Convolutional Neural Network (CNN) model was employed to accurately delineate channel boundaries and a Voronoi Diagram approach was complemented as the river width algorithm (RWA) to calculate river bankfull widths. The CNN model was trained by images across four river types and performed well with all the evaluating metrics (mIoU, Accuracy, F1-score, and Recall) higher than 0.97, referring to the accuracy over 97% in prediction. The RWA outperformed other existing river width calculation methods by showing lower errors. The application of the framework in the Lillooet River, Canada, presented the capacity of this methodology to obtain detailed distributions of hydraulic and hydrological parameters, including flow resistance, flow energy, and sediment transport capacity, based on high-resolution channel widths. Our work highlights the significant potential of the newly developed framework in acquiring high-resolution channel width information and characterizing fluvial dynamics based on these widths along river channels, which contributes to facilitating cost-effective integrated river management. [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]

While the past of terrain cannot be known precisely because an effect can result from many different causes, exploring these possible pasts opens the way to numerous applications ranging from movies and games to paleogeography. We introduce unerosion, an attempt to recover plausible past topographies from an input terrain represented as a height field. Our solution relies on novel algorithms for the backward simulation of different processes: fluvial erosion, sedimentation, and thermal erosion. This is achieved by re‐formulating the equations of erosion and sedimentation so that they can be simulated back in time. These algorithms can be combined to account for a succession of climate changes backward in time, while the possible ambiguities provide editing options to the user. Results show that our solution can approximately reverse different types of erosion while enabling users to explore a variety of alternative pasts. Using a chronology of climatic periods to inform us about the main erosion phenomena, we also went back in time using real measured terrain data. We checked the consistency with geological findings, namely the height of river beds hundreds of thousands of years ago. [ABSTRACT FROM AUTHOR]

River network connectivity (RC) describes the hydrologic exchange of water, nutrients, sediments, and pollutants between the river channel and other "sites" via heterogenous flowpaths along the river corridor. As water moves downstream it carries these constituents, creating a stream‐to‐ocean continuum of connectivity that regulates global water, carbon, and nutrient cycling. River network connectivity models have developed over many decades, culminating in recent years with network‐scale RC models that explicitly simulate the transport and exchange of water and elements from headwaters to coasts, sometimes requiring models to contain tens of millions of river reaches. These advances provide transformative insights into the aggregate effects of RC on water and material transport across scales from local to global. Yet, recent reviews have pointed to several challenges that need to be overcome to continue advancing network‐scale RC modeling. In service of these goals, I summarize recent network‐scale RC maps and models to identify similarities and differences across the large‐scale RC modeling landscape. Although our computational and upscaling abilities have significantly improved and have revealed new insights, current models are still limited by the quantity, quality, resolution, and lack of standardization of the available in situ databases and source data maps necessary for the modeling. This suggests that we can extend recent advances if we keep improving these source datasets, while continuously revisiting our physics and theory to explain those new data. In doing so, we will continue to expand the role of network‐scale RC models in informing water quality modeling and management into the future. [ABSTRACT FROM AUTHOR]

We conducted a phytosociological survey of pioneer shrub and shrub-wood (brushwood) communities on river banks at the contact of gravel bars and rockfall, slope debris or colluvium in the spring area of the Nadiža River, in the gorge of the Soča River between Srpenica and Kobarid (Log Čezsoški and Magozd), in the Tolminka valley, and in certain other locations in the hills of western Slovenia. We identified a successional sequence of two grey willow and hop hornbeam communities, which we classify into the associations Salicetum eleagno-appendiculatae (Salicion eleagno-daphnoidis) and Peucedano verticillari-Ostryetum carpinifoliae (Fraxino orni-Ostryion). Both are indicators of natural river banks that have not been artificially stabilized. We expanded the knowledge of hop hornbeam communities in the pre-Alpine–northern-Dinaric part of Slovenia with a description of a new association Scopolio carniolicae-Ostryetum carpinifoliae. Its sites are characterised by slightly moist soil, and its stands by a higher proportion of species of the alliance Tilio-Acerion. [ABSTRACT FROM AUTHOR]

Restoration of urban rivers must simultaneously design for ecological habitat while accounting for altered flow regimes associated with urban runoff, flood protection, and industrial/wastewater discharge. The goal of this study was to use ecological flow targets to guide channel restoration of the Los Angeles (LA) River across potential future flow regimes. Using a one‐dimensional hydraulic model, we simulated a range of channel cross section configurations subject to different flow management decisions (wastewater reuse, low‐flow [LF] treatment, and baseflow augmentation). Hydraulic results were assessed relative to ecohydraulic targets for desirable aquatic species in the LA River (willow, steelhead trout, and Santa Ana sucker). Results suggest that, along the mainstem of the LA River, restoration designs that include narrow LF channels may support Santa Ana sucker habitat and steelhead migration if management decisions decrease instream flows (e.g., by reusing treated wastewater). However, the same channel design and management decisions may not provide conditions needed to propagate floodplain vegetation such as willows. In tributary reaches, flows are too low to support habitat conditions for Santa Ana sucker or steelhead but may be able to support riparian habitat if a soft‐bottom LF channel and active floodplain are present. In general, results illustrate the trade‐offs between water management goals and habitat requirements for target species. [ABSTRACT FROM AUTHOR]

Baseflow is one of the major pathways of runoff in hilly areas, and its contributions to surface water resources and pollutant loads cannot be ignored. In this study, based on water quantity and quality data from 1988 to 2019 in hilly and low rainfall watersheds, we focused on the impact of long-term baseflow on nitrogen load using the load allocation based on the baseflow separation method. We also constructed a nitrogen balance model for the Chaohe River Basin of China from 2012 to 2021 to analyze the nitrogen accumulation in the basin. We used the baseflow nitrogen load lag analysis method to study the lag characteristics of the baseflow discharge process and analyzed the response and periodicity of baseflow nitrogen to precipitation and soil accumulation using time delay analysis. The results showed that the contribution rate of baseflow nitrogen reached 69% and showed a slight increasing trend from 1988 to 2019. The effects of changes in precipitation and nitrogen accumulation on the baseflow contribution was observed after 1–2 and 2 yr, respectively. After nitrogen accumulation, it entered the river channel through baseflow, which was already the main and continuous source of nitrogen in rivers in hilly areas. [ABSTRACT FROM AUTHOR]

The Mid-route of South-to-North Water Transfer Project mainly uses open channels for water transportation, with long distances and large spans along the route, and significant differences in climate between the ends of the channels. Low temperature can cause ice to appear in the channel, posing great challenges to the operation and scheduling of the channel. The bottom layer warm water of the Xiong an res- ervoir near the Xiheishan check gate is diverted into the channel to increase the channel water temperature, bringing new ideas for regulating the channel ice condition. This article establishes a one-dimensional channel ice hydraulic simulation model considering the inflow of warm water from the side, and conducts simulation research on the changes in water temperature and ice conditions inside the channel after warm water flow into the channel. The channel model was constructed based on the main canal of the Beijing-Shijiazhuang section as the prototype. By setting different inflow ratios, inflow temperatures, mixed discharges, and inflow times, the variation patterns of water temperature and ice cover thickness along the channel under different inflow conditions were explored. The results indicate that: (T) the idea of using offline reservoir charging to alleviate channel ice conditions is basically feasible, but the impact of the inflow from the regulating reservoir on the water temperature of the main channel is mainly within the downstream 20km channel. The closer the channel is to the downstream, the less affected it is, and the longer the delay time of water temperature rise. (2) The higher the proportion of incoming water from the reservoir, the more significant the impact on the water temperature of the canal. (3) The higher the temperature of the inflow water from the reservoir, the more significant the effect of improving the water temperature of the downstream channel pool, and the duration of the ice cover is significantly shortened, but the range of ice formation is not significantly reduced. (4) The larger the mixed discharge, the slower the water temperature decreases, and the closer the section with ice is to the downstream. (5) In actual scheduling, it is necessary to combine meteorological forecasts and start adding warm water to the channel before the winter cools down, and continue throughout the entire low-temperature period to achieve the best ice relief effect. The research results of this article can provide data support for the determination of alleviating the ice condition by water inflow, serve as a reasonable reference for the feasibility of engineering, and also provide reference for the calculation and simulation of other similar temperature mixing problems. [ABSTRACT FROM AUTHOR]

The rational layout of spur dikes has a significant impact on the flow structure, patterns of fluvial erosion and deposition. In addition to serving as a protective measure for riverbanks, these dikes also play a role in promoting the formation of various riverbed features, such as deep pools and shallow shoals nearby. These unique characteristics create a rich habitat for aquatic organisms, thereby enhancing ecological sustainability and development. Using the computational fluid dynamics (CFD) technique and the RNG k--ε model for parameter calibration and verification, this study undertakes a rigorous investigation into the hydrodynamic properties and the fluvial erosion-deposition processes occurring in the vicinity of spur dike units with diverse deflection angles situated at the concave bank of a 180° bend. The results indicated that, in relation to energy dissipation and water level fluctuations, the spur dike with a 90° deflection angle exhibited the most prominent characteristics, yielding the greatest water level disparities and the most significant energy losses. The spur dike exhibiting an upward deflection angle occupied a secondary position, whereas the spur dike with a downward deflection angle demonstrated the least notewor- thy effects. Furthermore, a positive correlation was identified between vortex intensity and the degree of riverbed erosion and deposition. Counterclockwise vortices contributed to deposition, whereas clockwise vortices were prone to cause erosion. In terms of the distribution of shear stress, the scope and magnitude of the intense shear stress zones formed at the head of the spur dike and on the opposite bank exhibit a distinct pattern where the spur dike with a 90° deflection angle shows the largest impact, followed by the upward deflection spur dike, and the downward deflection spur dike demonstrates the smallest impact. So, the selection of deflection angles for spur dikes significantly influences riverbed scouring and deposition, water flow characteristics, and ecological outcomes. It is crucial to scientifically and rationally design and arrange spur dikes to achieve a balance between controlling riverbed scouring and deposition, preserving ecological balance in river channels, and ensuring the safety of engineering projects. [ABSTRACT FROM AUTHOR]

Hydraulic modelling of culverts relating to the flood risk posed by debris in watercourses has previously only assessed the impact of fixed culvert blockage levels, without analysing the change in flooding as blockage levels increase. With increasing flow rates in rivers during flood events, there is concern that existing culverts may be undersized and therefore already posing a substantial flood risk regardless of them becoming blocked by debris. In this article, two‐dimensional (2D) flood modelling is used to produce flood maps detailing the change in flood area and property flooding as culverts become increasingly blocked at several sites in the Northwest of England. The results show a clear distinction between sites where the accumulation of blockage is the key contributing factor towards local flood risk, and sites where the presence of the culvert itself is the predominant flood risk factor. The blockage induced flood risk metric is introduced to characterise the contribution of culvert blockage to the overall flood risk. [ABSTRACT FROM AUTHOR]

Frazil ice is the foundation for all other ice phenomena, and its spatiotemporal evolution is critical for regulating ice conditions in rivers and channels, as well as for preventing and controlling ice damage. This paper investigates the dynamic transport pattern of frazil ice during the early stages of winter freezing in water conveyance channels based on a CFD-DEM coupled numerical model, and derives predictive formulae for the spatiotemporal evolution of frazil ice and floating ice. First, static repose angle simulations and slope sliding simulations were used to calibrate the contact parameters between frazil ice particles and between frazil ice and the channel bed, ensuring the accurate calculation of contact forces in the model. On this basis, the processes of frazil ice transport, aggregation, and upward movement in water transfer channels were simulated, and the influence of contact parameters on simulation results was analyzed, showing a significant effect when the ice concentration was high. Numerical results indicate that the amount of suspended frazil ice is positively correlated with the frazil ice generation rate and water depth, with minimal influence from the flow velocity; the amount of floating ice increases linearly along the channel, with growth positively correlated with the frazil ice generation rate and water depth, and negatively correlated with the flow velocity. Predictive formulae correlating frazil ice and floating ice amounts with the flow velocity, water depth, and other factors were proposed based on numerical results. There is good agreement between the predictive and numerical results: the maximum APE between the predicted and simulated values of suspended frazil ice is 13.24%, and the MAPE is 6.32%; the maximum APE between the predicted and simulated values of floating ice increment is 7.80%, and the MAPE is 2.89%. The proposed prediction formulae can provide a theoretical basis for accurately predicting ice conditions during the early stages of winter freezing in rivers and channels. [ABSTRACT FROM AUTHOR]

Sediment management is fundamental for managing mountain watercourses and their upslope catchment. A multidisciplinary approach—not limited to the discipline of hydraulics—is necessary for investigating the alterations in sediment transport along the watercourse by detecting those reaches dominated by erosion and deposition processes, by quantifying the sediment volume change, by assessing the functionality of the existing torrent control structures, and by delimitating the riparian vegetation patches. To pursue these goals, specific continuous monitoring is essential, despite being extremely rare in mountain catchments. The present study proposed an integrated approach to determine the hydro-morphological–sedimentological–ecological state of a mountain watercourse though field- and desk-based analyses. Such an integral approach includes a rainfall–runoff model, a morphological change analysis and the application of empirical formulations for estimating peak discharge, mobilizable sediment/large wood volume and watercourse hydraulic capacity, at reach and catchment scales. The procedure was tested on the Upper Adda River catchment (North Italy). The results identified where and with what priority maintenance and monitoring activities must be carried out, considering sediment regime, torrent control structures and vegetation. This study is an example of how it is possible to enhance all existing information through successive qualitative and quantitative approximations and to concentrate new resources (human and economic) on specific gaps, for drafting a scientifically robust and practical sediment management plan. [ABSTRACT FROM AUTHOR]

Post‐fire debris flows alter impacted fluvial systems, but few studies quantify the magnitude and timing of reach‐scale channel response to these events. In August 2020, the Big Creek watershed along California's central coast burned in the Dolan Fire; in January 2021, an atmospheric river event triggered post‐fire debris flows in steep tributaries to the Big Creek. Here, we characterize the evolution of fluvial morphology and grain size in Big Creek, a cascade and step‐pool channel downstream of tributaries in which post‐fire debris flows initiated, using pre‐ and post‐fire structure from motion (SfM) and airborne lidar surveys. We also make comparisons to Devil's Creek, an adjacent basin which burned but did not experience post‐fire debris flows. We observe grain size fining following debris flows in Big Creek, but the coarsest 40% of the grain size distribution remained essentially unchanged despite reorganization of channel structure. Changes in grain size and elevated post‐fire peak flows account for approximately equal portions of a substantial increase in modeled bedload transport capacity one year post‐fire. In Big Creek, geomorphic recovery is well underway just two years post‐fire. A valley‐spanning log jam, which formed during debris flows, acts as a sediment trap upstream of our Big Creek study reach, and is partially responsible for accelerating recovery processes. In contrast, Devil's Creek exhibited little change in morphology or grain size despite elevated post‐fire peak flows. This period of geomorphic dynamism following the Dolan Fire has complex ecological impacts, notably for the threatened anadromous salmonid spawning habitat in Big Creek. Plain Language Summary: Wildfires destroy vegetation and impair soils' ability to absorb rainfall. Fast‐moving mixtures of water and sediment (called debris flows) often flow through steep stream channels during storms following wildfires. Debris flows alter the form of affected streams and introduce large volumes of sediment to channels downstream. We document changes in the form and behavior of Big Creek, a stream in Big Sur, California which experienced debris flows after the 2020 Dolan Fire. We make comparisons to Devil's Creek, an adjacent stream which did not experience debris flows. Debris flows introduced additional fine sediment to Big Creek. Computer modeling indicates that this decrease in average grain size, coupled with increases in streamflow, led to an increase in the volume of sediment transported in Big Creek one year after the wildfire. Two years after the wildfire, the grain size in Big Creek had coarsened. We interpret coarsening as recovery toward pre‐fire conditions, and suggest that a newly formed log jam upstream of our study area acts to trap sediment supplied from upstream, accelerating recovery toward pre‐fire conditions. In contrast, grain size in Devil's Creek remained relatively consistent throughout our study period. Post‐fire changes in Big Creek have implications for threatened fish habitats. Key Points: Debris flows reorganized the step structure in Big Creek and triggered substantial grain size finingModeling indicates that grain size fining and discharge increases led to an increase in bedload transport in Big Creek 1 year post‐fireDebris flows formed a log jam upstream of our Big Creek study reach, which spurred grain size recovery 2 years post‐fire [ABSTRACT FROM AUTHOR]

Gravel bed rivers often display pool‐riffle morphology. Downstream changes in channel width are often correlated with pool‐riffle topography. Considering self‐formed, alluvial, straight and single‐thread gravel‐bed rivers, here we provide an analytical solution for their equilibrium pool‐riffle morphology in the presence of spatially varying widths. Our analytical model, based on mass and energy conservation for water flow, shows how bed level perturbations are closely linked to downstream width variations under the influence of water discharge. The analytical model is validated against experimental data and applied to reconstruct the natural pool‐riffle bed profile. The validated model shows how increasing water discharge (i.e., water depth and flow velocity) enhances the amplitude of pool‐riffle sequences. The proposed model can provide valuable guidance for river restoration projects. Plain Language Summary: Gravel bed rivers frequently show spatial width variations. Accompanying these variations, the riverbed presents topographic lows and highs, such as pools and riffles. We have developed an analytical model to quantify pool‐riffle topography in relation to specific width configurations. For gravel bed rivers, this model requires various estimable parameters, including water discharge, flow resistance, riverbed slope, and spatial width variation. River restoration projects often aim to restore rivers to their natural state. Our proposed model can provide crucial insights for comprehending and replicating the natural state of rivers. Key Points: The analytical model linking bed level perturbations with width variations is based on the conservation of mass and energy in water flowThe model demonstrates that bed level perturbations are positive when local width exceeds the average, and negative when it is lessWith larger water discharge, the height of riverbed perturbation increases [ABSTRACT FROM AUTHOR]

Aquatic vegetation is an important component of natural river ecosystem, usually growing in riverine, marsh, and coastal areas, interacting with water flow to form complex flow structure, which has an important impact on bank slope stability and flood discharge capacity of river channels. Four sets of indoor flume vegetation‐flow experiments were conducted using a typical beach trough structure in the lower section of the Yangtze River. The compound channel was divided into the main channel, side slope and side beach zones, and simulated vegetation such as reeds, sedges and dwarf grass were used. The emphasis was on the hydrodynamic properties under semi‐covered emergent rigid vegetation and semi‐covered non‐submerged rigid vegetation. In this study, the Shiono and Knight equation (SKM model) was used to elucidate the distribution characteristics of 'the depth‐averaged velocity Ud' and 'equivalent diameter D' of vegetation in water gradient, and the Taylor method was used to demonstrate that the proposed 'equivalent diameter D' of vegetation has a certain level of accuracy within a reasonable threshold range. In addition, a new secondary flow model was proposed using a genetic algorithm that considers many hydraulic and vegetation parameters. Further, a new secondary flow model was proposed using a genetic algorithm that considers many hydraulic and vegetation parameters. Finally, 'the depth‐averaged velocity Ud' of the compound channel was accurately predicted by combining the experimental data with the new SKM model. In this study, we investigated the water‐blocking ability of gradient vegetation in river water. A method in which the secondary flow law and formula are difficult to determine was solved, which could provide technical support for the design of complex vegetated rivers and the evaluation of the flood discharge capacity of rivers. [ABSTRACT FROM AUTHOR]

Purpose: The aims of this research were to assess the sources of variability of particulate FRNs (7Be, 210Pbex and 137Cs) in river channels, the influence of sediment properties such as particle size distribution (PSD) and organic matter (OM) on FRN distributions, and to discuss the implications for sediment tracing in rivers. Methods: Suspended and channel bed sediment samples were collected in the River Avon (Devon, UK) during five strategic surveys involving a wide variation of river flows, including flood conditions. Particulate matter was analysed for 7Be, 210Pbex and 137Cs by gamma spectrometry, PSD by laser diffraction, and organic constituents, total organic carbon (TOC) and total nitrogen (TN) by elemental analysis. Results: FRNs activity concentrations vary significantly both spatially, characterised by changes in activity concentrations within and between locations, and temporally, with changes during the storm hydrograph and between seasons. Variability was attributed to changes in sediment sources and, on some occasions, to significant correlation of activity concentrations with sediment properties. The results also highlighted the influence of changes in channel characteristics and the magnitude and frequency of floods on FRN distributions. Conclusion: In the context of sediment tracing, attention should be given to seasonal changes in riverine conditions that have the potential to affect 7Be and 137Cs conservativeness. Application of FRNs in sediment fingerprinting studies should be accompanied by appropriate temporal characterisation of potential sediment sources. Finally, potential contribution of 7Be-depleted sediment from channel resuspension to the suspended load should also be considered. [ABSTRACT FROM AUTHOR]

Waterfall retreat transmits base‐level perturbations upstream, thereby providing markers of changing climate and tectonics. In homogeneous rock, waterfalls often retreat either by direct waterfall‐face erosion or incision from repeating ('cyclic') steps formed above waterfalls. We lack knowledge on the conditions driving these different erosion styles, limiting our ability to predict waterfall retreat. We address this knowledge gap through flume experiments assessing how changing flow hydraulics modulates bedrock erosion. We show that, under large discharges, changes in flow hydraulics cause spatial variability in particle impact velocity, leading to cyclic step formation. As discharge decreases, both the magnitude and spatial variability of particle impact velocity decreases, causing more uniform erosion, limiting cyclic step development and potentially allowing direct erosion of the waterfall face to become the dominant retreat mechanism. These results suggest climate change and water‐resource management can alter the rate and style of waterfall retreat. Plain Language Summary: Waterfalls retreat upstream as they erode and, due to their rapid erosion, waterfalls can set erosion rates within landscapes. Waterfall retreat rates depend, in part, on the physical processes driving waterfall erosion. Waterfalls typically retreat either via direct waterfall‐face erosion or via forming smaller steps (called 'cyclic steps') which form immediately upstream of waterfalls and erode vertically. However, the conditions that cause one of these erosion mechanisms to dominate over the other are not well known. We performed laboratory experiments simulating waterfall erosion under variable water discharge while measuring changes in flow velocity and the velocity of sediment impacting the bedrock river bed. We pay particular attention to particle impacts because, like sandblasting, it is the impacts from sediment that drive bedrock erosion. Our experiments show that sediment impact velocity is sensitive to water discharge, and that this should lead to waterfalls retreating via cyclic step formation for rivers for relatively large floods, whereas for relatively small floods, waterfalls are more likely to retreat via direct erosion of the waterfall face. Key Points: The spatial distribution of particle impact velocity above waterfalls is sensitive to flow hydraulicsAt large discharges, increased spatial variability in particle impact velocity drives cyclic step formation above waterfallsAt low discharges, reduced variability in impact velocity limits cyclic step formation and promotes retreat via waterfall‐face erosion [ABSTRACT FROM AUTHOR]

Microplastic contamination of river sediments has been found to be pervasive at the global scale and responsive to plastic and sediment bed properties, the flow regime and the river morphology. The physical controls governing the storage, remobilization and pathways of transfer in sand bed rivers remain unquantified. This means it is not currently possible to determine the risks posed by microplastic contamination within these globally significant river systems. Using controlled flume experiments we show that sand bed rivers can store up to 40% of their microplastic load within the sediment bed indicating that these environments can act as resilient sinks of microplastics. By linking bedform dynamics with microplastic transport characteristics we show that similarities exist between granular transport phenomena and the behavior, and hence predictability, of microplastic flux. Specifically, we demonstrate the inverse relationship between bedform celerity and microplastic retention within the bed can be used to predict microplastic flux. Further, we show that, in these environments, microplastic shape is more important than previously thought in controlling the fate of microplastics. Together, these findings are significant since they have important implications for the prediction and hence management of microplastic contamination in sand bed environments. [ABSTRACT FROM AUTHOR]

AbstractGeological action is one of the main forces in the formation of topography, especially in the southeastern part of the Qinghai-Tibet Plateau. Collapse, landslide, mud-rock flow and other geological actions are the main factors affecting the evolution of river valley landforms. However, existing inference methods primarily rely on theoretical calculations and multi-temporal remote sensing image interpretation, lacking direct analysis and validation through geological exploration techniques. In response, this study employed geological engineering and geotechnical exploration techniques to investigate the impact of debris flows, landslides, and collapses on the evolution of topography and geomorphology in a 5.0 km section of the Yigong Zangbo Basin. Through drilling and geophysical exploration, 6 geological profiles were constructed, identifying the distribution range and development characteristics of the geological phenomena within this section of the river valley, revealing the distribution positions of both the new and old river channels, and inferring the evolution of the river bedrock based on the original topography. The study found that when geological phenomena occur, substantial material is transported into the river channel, altering its original shape and influencing the river’s erosion process. Additionally, the occurrence of geological phenomena is closely correlated with the evolution of river valley morphology. When the river valley is wide, material accumulation on one side causes the river to flow along a lower position on the opposite side, primarily resulting in the river’s bending on the plane. In contrast, in narrow river valleys, material accumulation on the sides can fill the entire river channel, leading to a rise in the riverbed. These research findings provide a critical theoretical basis for understanding river valley morphological evolution and informing basin engineering construction. [ABSTRACT FROM AUTHOR]

The Eastern Tianshan region, influenced by the far-field effect of northward compression and expansion of the Qinghai-Xizang block, features highly developed Late Quaternary active faults that exhibit significant neotectonic activity. Historically, the Barkol-Yiwu Basin, located to the north of the Eastern Tianshan, experienced two major earthquakes in 1842 and 1914, each with a magnitude of M71/2. In contrast, the Hami Basin on the southern margin of the Eastern Tianshan has no historical records of any major earthquakes, and its seismic potential, mechanisms, and future earthquake hazards remain unclear. Based on satellite image interpretation and field surveys, this study identified a relatively recent and well-preserved seismic surface rupture zone with good continuity in the Liushugou area of the western segment of the Northern Margin Fault of the Hami Basin (HMNF), which is the seismogenic structure responsible for the rupture. The surface rupture zone originates at Kekejin in the east, extends intermittently westward through Daipuseke Bulake and Liushugou, and terminates at Wuzun Bulake, with a total length of approximately 21 km. The rupture zone traverses the youngest geomorphic surface units, such as river beds or floodplains and first-order terraces (platforms), and is characterized by a series of single or multiple reverse fault scarps. The morphology of fault scarps is clear, presenting a light soil color with heights ranging from 0.15 m to 2.13 m and an average displacement of 0.56 m, suggesting that this surface rupture zone likely represents the most recent seismic event. Comparison with historical earthquake records in the Eastern Tianshan region suggests that the rupture zone may have been formed simultaneously with the Xiongkuer rupture zone by the 1842 M71/2 earthquake along the boundary faults on both sides of the Barkol Mountains, exhibiting a flower-like structural pattern. Alternatively, it might represent a separate, unrecorded seismic event occurring shortly after the 1842 earthquake. The estimated magnitude of the associated earthquake is about 6.6~6.9. Given that surface-rupturing earthquakes have already occurred in the western segment, the study indicates that the Erdaogou–Nanshankou section of the HMNF has surpassed the average recurrence interval for major earthquakes, indicating a potential future earthquake hazard. [ABSTRACT FROM AUTHOR]

Being tidal-sensitive, the river channel in the Longjin Yangqi area of Cangshan, Fuzhou City, is challenged further because of rapid urbanization. Thus, resultant remediation efforts are crucial. This study aims analyzes hydrodynamic characteristics of the area and, secondly, proposes an ecological dispatch solution with evaluation of its effectiveness through the Storm Water Management Model (SWMM). The chief tasks cover imitating rainfall runoff, optimizing sluice gate activities, reorganizing pump management, and reshaping river morphology to bolster flood control and water quality. Improvements were shown through ecological dispatch strategies, which suggested increasing the channel width for the river and deepening the riverbed, thereby increasing the flood duration, lowering water levels, and less frequent flood occurrences. Optimizing sluice gate settings improved efficiency in the regulation of water flow and reduced scour or siltation problems. Various adjustments to pumping operations scattered over various times were based on live-data analysis, therefore enhancing water flow and the self-purification capacity of the water body. The SWMM was directly applied in this tidal river for urban water resource management with data processing from over 100,000 points in simulations. Wherever needed, changes to model parameters were made to improve its capability and enhance its appropriate use in future urban settings. As a whole, this study presents a plan for sustainable water resource management paired with environmental conditions for the benefit of over 500,000 urban residents in the Longjin Yangqi area. [ABSTRACT FROM AUTHOR]

After the breach of a landslide dam, the sediment in the breach opening will be carried downstream by the breach flood. The river channel will also be eroded by the flood, resulting in bed load transport. Three large-scale dam breach tests were conducted to investigate the sediment transport behavior after a dam breach. The topography data of the creek channel were measured before and after the dam breach tests to understand the sediment transport behavior. The sediment transport simulations of the dam breach tests were conducted using the iRIC Nays2DH software. The simulations focused on three types of test setups: the single dam, single dam with a spur dike, and double dam models. The terrain (DEM) for the numerical model input was designated based on the LiDAR results, and a flow hydrograph during the dam breach tests was applied. The accuracy of the simulations was assessed using the "coverage index" and "mean absolute percentage error". A numerical parametrical study was performed to find the major parameters that influenced the simulations. The results showed that the dynamic behavior of water flow and sediment during the dam breach processes were effectively captured by the iRIC Nays2DH simulation, but with limitations. The average flow velocity of the flood in the single dam case was the fastest among the three types of dam breaches. Due to the contraction of the creek channel caused by the spur dike, severe erosion occurred locally, and the flow rate increased in the narrowed section. Water impoundment between the two dams after the first dam breach and the consequent breach of the second dam were also well-simulated for the double dam breach. The findings and simulations in this study help explain dam breaches better and can guide researchers working on sediment transport during dam-breach floods. [ABSTRACT FROM AUTHOR]

The paper studied the parameters used by the International Court of Justice in the Silala water case between Chile and Bolivia. For this purpose, the principles of International Water Law were used, as well as those developed by this high court of justice with respect to international watercourses. The role played by international custom in the resolution of the controversy was determined, as well as the need for further development of the principles derived from international custom for similar cases in the future, all of which will allow for greater optimization and preservation of transboundary basins. [ABSTRACT FROM AUTHOR]

River cross-section characteristics are not available for many regions of the world, and they are generally expressed as hydraulic geometry (HG) relationships. These relationships usually represent average characteristics of a region, which can generate biased estimates in smaller basins. Therefore, to improve the representation of river channel geomorphological characteristics, the objective of this study was to use a large database of river cross-section geometries to refine HG relationships for five river basins in Brazil. HG relationships were developed for the entire basins and for hydraulically homogeneous regions, obtained through a geographical convenience method. The relationship between the coefficients of the geometric relationships and morphoclimatic characteristics was assessed, showing a trend between precipitation and slope and the coefficients of the depth relationships. The estimated bankfull width and depth values were also compared to observed data and global datasets, showing an improvement in estimates with the more refined HG relationships. [ABSTRACT FROM AUTHOR]

A filter unit (FU) is a structure installed with the aim of protecting the foundation of an embankment revetment from riverbed scouring, and there are cases in which sediment is deposited in the surrounding area after installation. Vegetation growth in sediment can improve the environment and protect revetments. Hydraulic experiments and numerical calculations were conducted to investigate how suspended sediments are deposited around FUs over a large area within a short period of time. We performed suspended sediment deposition experiments using FU models and confirmed that sediment deposition can be calculated accurately using a two-dimensional planar model. We also analyzed FU placement and its impact on topographical changes in an actual river in which FUs were installed. The results showed that (1) the continuous placement of FUs inhibits sediment deposition on the downstream side; (2) arranging FUs at intervals facilitates sediment deposition even under small-scale floods; and (3) employing an interval of half the FU width for every three or more FUs can effectively promote suspended sediment deposition at intervals. [ABSTRACT FROM AUTHOR]

In recent years, the population of white-spotted charr (Salvelinus leucomaenis) has been declining in the upper reaches of the Daiya River, Nikko City, Tochigi Prefecture. One of the causes is the deterioration of the river environment due to an influx of sediment and construction work. Among the studies investigating the habitat preferences of charr, there are few examples of habitat assessment of stream channels severely altered by artificial structures, such as dams, revetments and concrete riverbeds. For this reason, this study investigated the presence/absence of charr in a reach with sequential low-head dams in the Daiya River that has all those structures. The results indicate that the presence of charr in the altered reach was associated with the abundance of rocks or greater water depth (>20 cm). Based on these results, we conclude that when trying to create a habitat for charr in a stream reach with sequential low-head dams, one should consider adding complexity in terms of rocks and water depth. [ABSTRACT FROM AUTHOR]

Urbanization transforms natural river channels, and surface water of some rivers disappeared over time. How and whether the subsurface domains of the original waterways and aquifers connecting them (a phantom of historical landscape) are functional is not known. This study examined the effects of tributary groundwater inflow on the response of river–riparian organisms in an alluvial mainstem river in northern Japan, where the tributary disappeared over the course of urban landscape transformation.A 2.8‐km lowland segment of the mainstem gravel‐bed river was examined for water properties and the river–riparian food web. In addition, watershed‐wide water sampling was conducted to isotopically distinguish several types of groundwater that contributed to the hyporheic water in the study segment. Altitude had a clear effect on the hydrogen/oxygen stable isotope ratios in the river water collected across the watershed.Groundwater unique both in chemical and isotopic signatures occurred in several spots within the study segment, and its properties resembled and its upwelling locations matched groundwater from a tributary river whose surface channel disappeared 60 years ago. Positive numerical increases in abundance and/or a sign of nitrogen transfer in river–riparian communities (algae, invertebrates and riparian trees) originating from groundwater high in nitrate with elevated nitrogen stable isotope ratios were found.We demonstrated that tributary groundwater with unique chemical properties manifested by an urban watershed river network continued to have trophic effects on biota across the river–riparian boundary in the mainstem river, even after urbanization transformed the tributary into a phantom river. We highlighted the legacy effects of landscape transformation in the subsurface domain and the significance of scrutinizing the past landscape and hydrological connectivity at the watershed scale in urban environments. [ABSTRACT FROM AUTHOR]

Climate change is causing stream flow regimes to change in many regions globally, including southwestern Australia (SWA) where many perennial streams have switched to intermittent flow regimes. In drier landscapes, ecological refuges and evolutionary refugia will become critical for conserving freshwater biodiversity. This study aimed to determine the contribution of dry season refuges to species persistence and community recovery in a forested headwater catchment where perennial streams have been exposed to severe permanent drying, causing them to become intermittent. That is, in streams where formerly no drought refuges were present.Macroinvertebrate assemblages were sampled in dry season refuges within recently intermittent streams. Refuges included small spring‐fed pools, perched pools and subterranean refuges associated with granite inselbergs. Dry streambeds were searched for organisms aestivating in situ, and sediments were collected from each intermittent stream for rehydration.Mantel tests were used to compare the contribution of refuges to species assemblages in the early wet season when intermittent streams had begun to flow. Analysis of similarities was used to compare patterns between dry and wet season assemblages of intermittent streams and the single remaining perennial stream in the catchment, to infer the contribution of the perennial stream to community recovery in intermittent streams.Refuge types had very different assemblages: spring‐fed refuges supported several locally endemic species, but perched pools were dominated by opportunistic colonists. Several taxa were found aestivating in dry sediments, primarily adult Coleoptera and larval Chironomidae. Inselberg springs supported small populations of endemic Trichoptera and Ephemeroptera and provided subterranean refuge for an endemic amphipod. However, dry season refuges did not significantly contribute to community recovery. Rather, assemblages in early winter flows were similar to those inhabiting the perennial stream, showing that recolonisation from perennial streams is likely the primary process of community recovery in these recently intermittent streams.Newly formed dry season refuges supported some locally endemic species, but also colonising species that were formerly absent (or rare) when all streams were perennial. However, continued loss of perennial streams in SWA will result in landscape‐wide reductions in diversity (as colonisation sources are lost), because there are no known evolutionary refugia in this landscape for relictual species to retreat into. Granite inselbergs may become evolutionary refugia for a few species, as perennial streams are lost.Refuges will likely play a pivotal role in persistence of species able to use them; however, the existence of refuges is also under threat from prolonged climatic drying, including refuges newly formed by stream dry. Thus, identification and protection of future evolutionary refugia is a matter of urgency in regions facing drier climates, as it is ultimately evolutionary refugia that will become critical reservoirs of freshwater biodiversity as perennial streams and refuges are lost. [ABSTRACT FROM AUTHOR]

Analytical and semi‐analytical models for stream depletion with transient stream stage drawdown induced by groundwater pumping are developed to address a deficiency in existing models, namely, the use of a fixed stream stage condition at the stream–aquifer interface. Field data are presented to demonstrate that stream stage drawdown does indeed occur in response to groundwater pumping near aquifer‐connected streams. A model that predicts stream depletion with transient stream drawdown is developed based on stream channel mass conservation and finite stream channel storage. The resulting models are shown to reduce to existing fixed‐stage models in the limit as stream channel storage becomes infinitely large, and to the confined aquifer flow with a no‐flow boundary at the streambed in the limit as stream storage becomes vanishingly small. The model is applied to field measurements of aquifer and stream drawdown, giving estimates of aquifer hydraulic parameters, streambed conductance, and a measure of stream channel storage. The results of the modeling and data analysis presented herein have implications for sustainable groundwater management. [ABSTRACT FROM AUTHOR]

To comprehensively realize the effects of reservoir sediment flushing on fluvial processes and downstream flood control, this study examines flood routing and sediment transport, as well as changes in erosion and sediment patterns within the bottle-neck reach of flood conveyance and the widened reach in the Lower Yellow River (LYR). This analysis employs measured data from the reservoir and river course collected from 2018 to 2020 and allows for assessing changes in the water—sediment relationship before and after flood events. The obtained results reveal that the total sediment load of 6 floods discharged by Xiaolangdi Reservoir (XLD) amounted to 1.09 billion tons. The ratios of the deposition to incoming sediment load in the LYR ranged from 58.0% to 84.2%, significantly higher than those observed in flood events with similar incoming sediment ratios from 1965 to 1999. Coarse sediments accounted for the largest share with 44.4%, followed by medium sediments at 29.0%, and fine sediments at 26.6%. Most of the deposition, 79.1%, occurred upstream of Huayuankou (HYK), with HYK —Gaocun and Gaocun —Aisan accounting for 15.9% and 3.5% of the deposition respectively. The channel storage upstream of HYK played a role in temporarily detaining the sediment. The deposition that occurs during flood periods can be washed away within 1 to 2 years after the flood, without adversely affecting the floodcarrying capacity of the channel. The exchange of suspended sediment with bed materials led to the refining of suspended particles along the river course. After the flood, significant bed material refinement was observed at the HYK station. Sediment flushing of the reservoir during flood period improves the water—sediment relationship post-flood and increases the efficiency of water resource utilization. The findings of this study advance the scientific understanding of the impacts of reservoirs on sediment-laden rivers and their downstream fluvial processes also provides technical support results for channel flood control and water-sediment regulation in reservoirs. [ABSTRACT FROM AUTHOR]