Transport In Streams Research Articles

Correction to: Evaluation of Sediment Transport in Ephemeral Streams: A Case Study in the Southwestern Saudi Arabia

Correction to: Evaluation of Sediment Transport in Ephemeral Streams: A Case Study in the Southwestern Saudi Arabia

Control of Surface Plastic Transport in Natural Streams

Control of Surface Plastic Transport in Natural Streams

Hyporheic Reaction Potential: A Framework for Predicting Reach Scale Solute Fate and Transport.

We develop a new framework, hyporheic reaction potential (HRP), to predict the influence of oxidation-reduction reactions on metal fate and transport in streams using data from tracer studies and geochemical sampling. HRP, with energy flux units [KJ m-2 s-1], is a metric calculated from both the physical and chemical properties of the hyporheic zone. We apply the HRP framework for iron reactions, using existing geochemical and geophysical data from two metal-impacted alpine streams at high and low flow. In these two systems, HRP delineates contrasting controls on iron fate and transport with biogeochemical controls in Mineral Creek and physical controls in Cement Creek. In both systems, HRP scales with discharge and hyporheic-zone extent as flows change seasonally, which demonstrates the ability of HRP to capture physical aspects of chemical reactions in the hyporheic zone. This paper provides a foundation on which HRP can be expanded to other solutes where chemical gradients in the hyporheic zone control reaction networks, making it broadly applicable to redox cycling in stream systems. This framework is useful in quantifying the role of the hyporheic zone in sourcing and storing metal(loid)s under varying hydrologic conditions with implications for water quality, mine remediation, and regional watershed management.

DTM resolution controls the accuracy of estimating surface runoff indicators in flat, lowland landscapes

AbstractSurface runoff plays an important role in contaminant transport, nutrient loss, soil erosion and peak discharges in streams and rivers. Because it is the result of a variety of complex hydrological processes, estimating surface runoff using physically based hydrological models is challenging. Upscaling of physical soil properties is necessary to cope with the limits of computational power in surface runoff modelling. In flat landscapes, the (micro)topographic surface controls the onset and progression of surface runoff on saturated soils during rain events. Therefore, its proper representation is crucial when attempting to model and predict surface runoff. In this study, the influence of microtopography (centimetre scale) on estimations of maximum depression storage (MDS), random roughness (RR) and the connectivity threshold (CT) is explored. These properties are selected because they often serve as surface runoff indicators in hydrological modelling. To characterize microtopography, a terrestrial laser scanner (TLS) is used to generate a digital terrain model (DTM) of the study site with a horizontal spatial resolution of 5 cm. MDS, RR and CT are then calculated and compared to the values generated from the publicly available Dutch national DTM dataset with a resolution of 50 cm. Our results show considerable differences in MDS, RR and CT when calculated for the different input resolution datasets. Using DTMs that do not sufficiently capture microtopography leads to underestimation of MDS and RR, and to overestimation of CT. Our findings indicate that surface runoff indicators, and thereby the surface runoff response of a saturated surface to rainfall events, are defined at scales smaller than the scales of typically available DTMs. Understanding surface runoff through modelling studies therefore requires a framework that accounts for this lack of information arising from using coarser resolution DTMs. We demonstrate a linear relationship between MDS values generated from the different resolution DTMs. This opens the possibility of using empirical scaling relationships between high‐ and lower‐resolution DTMs to account for microtopography. Repetition of our measurements on similar surfaces would contribute to establishing such empirical scaling relationships. Our results should be seen as indicative of flat landscapes and surfaces where centimetre scale microtopography is relevant.

Evaluation of Sediment Transport in Ephemeral Streams: A Case Study in the Southwestern Saudi Arabia

Evaluation of Sediment Transport in Ephemeral Streams: A Case Study in the Southwestern Saudi Arabia

Application of Machine Learning Approaches in Particle Tracking Model to Estimate Sediment Transport in Natural Streams

Application of Machine Learning Approaches in Particle Tracking Model to Estimate Sediment Transport in Natural Streams

A comprehensive assessment and comparison of the impacts of storage parameters on solute transport in streams using a novel framework

Researchers must determine the storage parameter values to understand the storage processes and compare them across streams. These parameters are highly variable in time and space, making them challenging to measure. Individual studies of a single stream cannot characterize the interrelations among the processes involved in solute transport, hydraulic variables, and physical stream characteristics. Despite decades of research, a comprehensive framework is lacking. This study uses a simple and effective Monte Carlo approach to propose a general framework within which most solute transport models can undergo sensitivity analysis. This framework provides a comprehensive depiction of model performance under various scenarios, such as flow properties, stream geomorphology, and solute status. The relative and absolute sensitivities of three solute transport models, namely, the modified advection–dispersion equation (MADE), transient storage model (TSM), and variable residence time (VART), were evaluated and compared within the proposed framework. The main findings can be summarized as follows. In most conditions, storage models are more sensitive to the ratio of the storage zone cross-section to the stream cross-section than other parameters. Increasing the exchange rate between the stream and storage zones reduces the sensitivity to its indicative parameter and, consequently, its impact on the concentration time series. MADE's capability to identify modification parameters is higher for streams where dispersion dominates over advection, and their estimates have lower uncertainty. On the other hand, as advection becomes more dominant over dispersion in TSM and VART, estimated storage parameters have lower uncertainty.“

Assessment of the impact of land cover changes on sediment yield: a case study

Abstract Land use is one of the most important variables impacting river basin water and land resource planning and management. Sediment transport in streams is an important issue in the assessment of sediment deposition in dam reservoirs and its impact on operational activities. Evaluation of sediment yield contributes to decision-makers for effective water management and protection of the dam body and its elements. In this study, land use cover changes, in particular in forest areas, agricultural areas, arable lands, permanent crops, heterogeneous agricultural areas, and pastures in the Çakıt and Körkün sub-basins of the Seyhan River basin were examined between 1990 and 2018 using CORINE land use cover (CLC) data. The effect of land use/land cover (LULC) modifications on sediment yield was studied using suspended sediment observation data and CLC data. It was determined that the forest area in the Çakıt sub-basin drainage area increased between 1990 and 2018, and decreased in the Körkün sub-basin. It was determined that the increase in forest area in the Çakıt sub-basin drainage region until 2018 helped to reduce sediment movement. The regression values between forest area and suspended sediment concentration in Çakıt and Körkün sub-basins were found to be 0.9521 and 0.4431, respectively.

Large wood recruitment, retention and mobilization in low-order streams of the Brazilian Savanna

The delivery of wood to streams varies in space and time and may occur continuously or episodically. Once in a stream, wood may be retained or transported due to the balance between driving (water flow) and resisting forces (channel features and wood characteristics). Despite there being few studies directly measuring wood mobility, notable variations in annual transport rates and mean travelled distances have already been detected worldwide. In the tropics, due to wetter and warmer conditions and consequently higher decay rates and peak discharge, wood is believed that more readily degraded and transported downstream. However, there exists a knowledge gap regarding wood dynamics in tropical streams and even more considering tropical non-forested environments. In the present study, we aimed to document large wood (LW) recruitment, retention, and mobilization over a period of one year in eight low-order streams of the Cerrado (the South American Savanna) by tagging and tracing LW pieces. We detected high LW transport and recruitment rates in Cerrado streams, such that the total wood amounts remained constant over time. However, there were important differences between streams due to their distinct channel morphologies and the occurrence of episodic events. The LW length and diameter, original location and orientation were the most important factors in the prediction of the LW travelled distance, which ranged from zero to almost 100 m in one year. Our findings provide unprecedented information regarding wood mobility in tropical savanna streams in South America. To further advance knowledge about the dynamics of wood in Cerrado streams, future studies should characterize the great diversity of wood, especially with regard to densities that may strongly affect wood mobility. Furthermore, it is essential to perform long-term studies to document the dynamics of wood over years in these environments.

Influence of Sediment Supply Timing on Bedload Transport and Bed Surface Texture During a Single Experimental Hydrograph in Gravel Bed Rivers

AbstractChannel stability and sediment transport in gravel bed streams depend on temporally and spatially variable fluid forces, bed surface structures, armoring, and sediment supply/storage. Of particular interest here is the influence of sediment supply timing on bedload transport rate and grain size distribution, bed surface composition and channel morphology. We conducted flume experiments in a sediment feed flume with poorly sorted sediment. A symmetrical, identical stepped hydrograph was used with five different sediment feeding schemes: no feed, constant feed, rising‐limb only feed, falling‐limb only feed, and variable feed. The same sediment mass of 800 kg was fed during each experiment. Sediment transport rates ranged over five orders of magnitude regardless of feeding scheme. Clockwise hysteresis was observed for bedload transport rate and bedload grain size, that is, the transport rate was larger and coarser during the rising limb. Counterclockwise hysteresis was observed for the grain size distribution of the bed surface, that is, the bed surface was finest during the rising limb. In all experiments sediment yield during the rising was higher than during the falling limb, indicating that the rising limb is more capable to transport the supplied sediment. Our study provides insight on how timing of sediment supply influences sediment transport and bed surface during a single hydrograph, essential information for artificial sediment supply projects to restore and habilitate gravel bed streams.

Transport and evaporation of exhaled respiratory droplets: An analytical model

An important vector for host-to-host infectious disease transmission is given by the transport of tiny pathogen-laden droplets. These are commonly exhaled by individuals while breathing, speaking, coughing, or sneezing. Depending on their size and ambient conditions, they may follow different paths, either settling on surfaces where the pathogen can be further transmitted by contact, or remaining airborne after evaporation where the pathogen can be inhaled. Our understanding of pathogen transmission from the fluid mechanics perspective is still somewhat limited, especially in quantitative terms. In the current work, starting from the fundamental laws of fluid mechanics and diffusion, a detailed analytical model of droplet transport and evaporation in humid air streams is presented and successfully validated against available data in the literature finding remarkable agreement. The model implements closed-form analytical solutions of the equations of transport, evaporation, and energy balance, and an algebraic model to account for the droplet chemical composition. It also features an analytical model of droplet transport within the buoyant exhaled breath cloud based on momentum conservation addressing both jet and puff phases and is able to handle periodic respiratory events. Turbulent dispersion is modeled with a discrete random walk approach. A simple inhalation model is also proposed. Such a model may help in better understanding droplets' fluid dynamic behavior and may be used to assess the risks associated with pathogen transmission under different scenarios for any type of respiratory event. Overall, the computational cost is relatively low, allowing extensive simulation campaigns to be performed easily.

Effects of near-bed turbulence on microplastics fate and transport in streams

Quantifying the impact of hyporheic exchange is crucial for understanding the transport and fate of microplastics in streams. In this study, we conducted several Computational Fluid Dynamics (CFD) simulations to investigate near-bed turbulence and analyze vertical hyporheic exchange. Different arranged spheres were used to represent rough and permeable sediment beds in natural rivers. The velocities associated with vertical hyporheic flux and the gravitational force were compared to quantify the susceptibility of microplastics to hyporheic exchange. Four scenario cases representing different channel characteristics were studied and their effects on microplastics movements through hyporheic exchange were quantitatively studied. Results show that hyporheic exchange flow can significantly influence the fate and transport of microplastics of small and light-weighted microplastics. Under certain conditions, hyporheic exchange flow can dominate the behavior of microplastics with sizes up to around 800 μm. This dominance is particularly evident near the sediment-water interface, especially at the top layer of sediments. Higher bed porosity enhances the exchange of microplastics between water and sediment, while increased flow conditions extend the vertical exchange zone into deeper layers of the bed. Changes in the bedform lead to the most pronounced vertical hyporheic exchange, emphasizing the control of morphological features on microplastics transport. Furthermore, it is found that sweep-ejection events are prevailing near the bed surface, serving as a mechanism for microplastics transport in rivers. As moving from the water column to deeper layers in the sediment bed, there's a shift from sweeps dominance to ejections dominance, indicating changes of direction in microplastics movement at different locations.

Geomorphic complexity influences coarse particulate organic matter transport and storage in headwater streams

Coarse particulate organic matter (CPOM; organic matter 1–100 mm in diameter, excluding small wood) stored in streams provides an important energy source for aquatic ecosystems, and CPOM transport provides downstream energy subsidies and is a pathway for watershed carbon export. However, we lack understanding of the magnitude of and processes influencing CPOM storage and transport in headwater streams. We assessed how geomorphic complexity and hydrologic regime influence CPOM transport and storage in the Colorado Front Range, USA. We compared CPOM transport during snowmelt in a stream reach with high retentive feature (e.g., wood, cobbles, and other features) frequency to a reach with low retentive feature frequency, assessing how within-a-reach geomorphic context influences CPOM transport. We also compared CPOM transport in reaches with differing valley geometry (two confined reaches versus a wide, multi-thread river bead) to assess the influence of geomorphic variations occurring over larger spatial extents. Additionally, we compared CPOM storage in accumulations in reaches (n = 14) with flowing water or dry conditions in late summer and investigated how small pieces of organic matter [e.g., woody CPOM and small wood (>1 min length and 0.05–1 min diameter or 0.5–1 min length and >0.1 min diameter)] influence CPOM storage. We found that within-a-reach retentive feature frequency did not influence CPOM transport. However, valley geometry influenced CPOM transport, with a higher CPOM transport rate (median: 1.53 g min−1) downstream of a confined stream reach and a lower CPOM transport rate (median: 0.13 g min−1) downstream of a low gradient, multi-thread river bead. Additionally, we found that particulate organic carbon (POC) export (0.063 Mg C) in the form of CPOM was substantially lower than dissolved organic carbon (DOC) export (12.3 Mg C) in one of these headwater streams during the 2022 water year. Dry reaches stored a higher volume of CPOM (mean = 29.18 m3 ha−1) compared to reaches with flowing water (15.75 m3 ha−1), and woody CPOM pieces trapped 37% of CPOM accumulations. Our results demonstrate that the influence of geomorphic context on CPOM transport depends on the scale and type of geomorphic complexity, POC may be lower than DOC export in some headwater streams, and small woody organic material is important for trapping CPOM small streams.

Advances in Monitoring and Understanding the Dynamics of Suspended-Sediment Transport in the River Drava, Slovenia: An Analysis More than a Decade-Long

Managing sediment transport in streams is crucial to the surface water resource development strategy and has several implications for flood risk and water management, hydropower use, and balancing river morphology. This paper summarises the movement and behaviour of suspended sediment within the Slovenian portion of the River Drava, covering a span of thirteen years from 2005 to 2018. An analysis of relevant data collected during this period is also presented. Suspended-sediment dynamics strongly depend on flow velocity, seasonal variations in sediment sources, and human interventions in the riverbed. The transportation of material in the River Drava results in the accumulation of sediments in reservoirs and riverbeds, consequently impeding the natural hydrological cycle by reducing the outflow into aquifers. The 2018 high-water event is analysed in terms of the dependence of concentration of suspended sediments on discharge, where counterclockwise hysteresis was observed, providing an essential clue to the origin of sediment. Sediments from the River Drava in Slovenia are managed with some conventional processes and are mainly deposited or reintegrated into rivers and aquatic ecosystems. Some additional sediment management strategies with long-term solutions for efficient and comprehensive water management, hydropower, and ecological problems are proposed.

Suspended Sediment Transport in Mediterranean Streams: Monitoring and Load Estimation

The suspended sediment (SS) load provides valuable insights into soil loss magnitude, requiring comprehensive monitoring of streamflow (Q) and SS concentrations (SSC) across various hydrological conditions. The primary aim of this paper was to quantify SS loads in two mountainous river basins: the Carapelle (506 km2) and the Celone (72 km2) located in Apulia (Southeast Italy) where different monitoring strategies were adopted (i.e., continuous and discrete). The specific objective was to develop sediment rating curves to address gaps in the SSC time series. An optical probe was used to continuously monitor the SSC during 2007 to 2011 in a river section of the Carapelle river, while Q was measured with the ultrasonic method. A comprehensive dataset comprising continuous Q measurements and discrete SSC measurements was systematically acquired for the Celone river over the period of 2010 to 2011. Distinct sediment rating curves were formulated for three specific subsets of data delineated by discernible hydrological conditions (i.e., high, normal, and low flow) and SSCs were computed for the missing daily records. The annual specific sediment load exhibited a range of 2.4 to 6.06 t ha−1 yr−1 for the Celone river, while the Carapelle river displayed a range of 0.9 to 7.45 t ha−1 yr−1. A significant majority of the SS load was transported during high-flow conditions, accounting for over 80% of the total load. In contrast, during low-flow conditions, the SS load constituted less than 1% of the total load. The findings of this study highlight the significance of the hydrological regime as a critical factor influencing sediment transport in mountainous Mediterranean rivers. Furthermore, it demonstrates that the duration of the sampling period, along with its specific characteristics, such as dry or wet conditions, can have a substantial impact on the accurate quantification of the sediment load.

Discharge, Groundwater Gradients, and Streambed Micro-Topography Control the Temporal Dynamics of Transient Storage in a Headwater Reach.

Contradictory interpretations of transient storage modeling (TSM) results of past studies hamper the understanding of how hydrologic conditions control solute transport in streams. To address this issue, we conduct 30 instantaneous tracer experiments in the Weierbach stream, Luxembourg. Using an iterative modeling approach, we calibrate TSM parameters and assess their identifiability across various hydrologic conditions. Near-stream groundwater monitoring wells and LIDAR scans of the streambed are used to evaluate the area of the hyporheic zone and of the submerged sediments for each experiment. Our findings show that increasing discharge enhances parameters interaction requiring more samples of TSM parameters to obtain identifiable results. Our results also indicate that transient storage at the study site is influenced by in-stream and hyporheic exchange processes during low discharge, likely due to the hyporheic zone's large extent and the relatively low water level compared to the size of slate fragments on the streambed. However, as discharge increases, in-stream storage zones become part of the advective channel and the lower localized stream water losses to the adjacent groundwater suggests a decrease of the hyporheic exchange on transient storage. The results obtained were utilized to generate a hydrograph for the study site illustrating the dynamic evolution of in-stream and hyporheic storage with varying discharge, providing insights into the expected influence of different transient storage processes prior to tracer experiments. Overall, our study enhances the understanding of the role of the hyporheic area and in-stream storage zones in transient storage and helps estimate TSM parameters more accurately.

Master equation model for solute transport in river basins: part I channel fluvial scale

Normal and anomalous diffusion are ubiquitous in many physical complex systems. Here we define a system of diffusion equations generalized in time and space, using the conservation principles of mass and momentum at channel scale by a master equation. A numerical model for describing the steady one-dimensional advection-dispersion equation for solute transport in streams and channels imposed with point-loading is presented. We find the numerical model parameter as the solution of this system by estimating the transition probability that characterizes the physical phenomenon in the diffusion regime. The results presented (Part I) refer to the channel scale and represent the first part of a research project that has been extended to the basin scale.

Development of a model for radionuclide transport in streams for biosphere assessment purpose

As a part of the overall safety assessment for a geological disposal of radioactive waste, models for different ecosystems are used to evaluate doses to humans and biota from possible radionuclide discharges to the biosphere. In previous safety assessments, transport modelling of radionuclides in running waters such as streams has been much simplified to the extent that only dilution of the inflow of radionuclides has been considered with no regard of any other interactions.Hyporheic exchange flow (HEF) is the flow of surface water in streams that enters the subsurface zone and, after some time, returns to the surface. HEF has been studied for decades. Hyporheic exchange and the residence time in the hyporheic zone are key parameters controlling the transport of radionuclides in a stream. Furthermore, recent studies have shown that HEF can reduce the groundwater upwelling area and increase the upwelling velocity in areas closest to the streambed water interface.In this paper, the development of an assessment model describing radionuclide transport with consideration of HEF and deep groundwater upwelling along streams is presented. An approach to parameterising the hyporheic exchange processes into an assessment model is based on a comprehensive study that has been performed in five different Swedish catchments. Sensitivity analyses are performed to explore the effect with consideration of the inflow of radionuclides with regard to HEF and deep groundwater upwelling in a safety assessment perspective. Finally, we include some suggestions for the application of the assessment model to long-term radiological safety assessments.

An Explicit Solution for Characterizing Non-Fickian Solute Transport in Natural Streams

One-dimensional solute transport modeling is fundamental to enhance understanding of river mixing mechanisms, and is useful in predicting solute concentration variation and fate in rivers. Motivated by the need of more adaptive and efficient model, an exact and efficient solution for simulating breakthrough curves that vary with non-Fickian transport in natural streams was presented, which was based on an existing implicit advection-dispersion equation that incorporates the storage effect. The solution for the Gaussian approximation with a shape-free boundary condition was derived using a routing procedure, and the storage effect was incorporated using a stochastic concept with a memory function. The proposed solution was validated by comparison with analytical and numerical solutions, and the results were efficient and exact. Its performance in simulating non-Fickian transport in streams was validated using field tracer data, and good agreement was achieved with 0.990 of R2. Despite the accurate reproduction of the overall breakthrough curves, considerable errors in their late-time behaviors were found depending upon the memory function formulae. One of the key results was that the proper formula for the memory function is inconsistent according to the data and optimal parameters. Therefore, to gain a deeper understanding of non-Fickian transport in natural streams, identifying the true memory function from the tracer data is required.

Regime Channel Bedload Transport Equation

Numerous theories have been presented over the years for quantifying bedload transport in streams and rivers. These theories have been derived using physical processes, statistical methods, and semiempirical and empirical methods and rely on a variety of hydraulic, boundary, and bed material properties. Most of these equations represent instantaneous bedload transport related to temporal hydraulic and bed conditions and are not well-suited to estimate long-term average bedload over a broad range of channels. Using a pure empirical analysis, the author has developed a dimensionally homogeneous regime channel bedload transport equation not requiring bedload measurements for calibration or verification. The new equation was developed using 45 data sets and verified using 29 additional data sets encompassing a very broad range of channel conditions and was found to rely solely on stream power and bank-full stream power or, for practical applications, flow and bank-full flow. Statistical metrics indicated better performance by the new equation than by other bedload transport equations evaluated using the same source data and statistical methods.