Cohesive sediment erosion and transport

A local scour is the removal of bed material from around the pier of the bridge. This bed removal is considered a big problem and is of great concern for hydraulic engineers. They should find economic solutions for this problem. The exaggerated local scour around bridge piers leads to many problems for the whole bridge structure, such as stability problems that may lead to the bridge's destruction. This paper aims to verify the scour depth around different shapes of uniform bridge piers for different flow conditions than those done by previous researchers using different prediction models. Where the consistency of previous experimental investigations is verified by multiple nonlinear regression analysis (MNLR), Gene Expression Programming (GEP) and Artificial Neural Network (ANN) models. In the comparison of values that were measured and predicted by the four models (CFD, MNLR, ANN, and Gene), it is seen that the ANN model has the ability to predict the Ys/b values higher than other models used in relation to the measured values. This makes the ANN model superior in predicting the Ys/b value over the other used models, followed by the Gene model. In comparison, the values of the R 2 and RMSE for the four models that were used in this study, for the Ys/b model using the ANN had a value of 0.9978 and 0.0147, respectively, while those for the Ys/b model using the Gene model were 0.9800 and 0.0375, respectively.

The significance of fines on the cohesive behavior of mine tailings has been investigated by examining the incipient motion of the tailings. Sixteen laboratory experiments were performed in a Plexiglas laboratory annular column on reconstituted mine tailings under a 50 cm water cover. Re-suspension was produced by a Teflon stirrer and the velocity field in the column was characterized using a laser Doppler velocimeter (LDV). The pressure change in the boundary layer was also measured with a Preston tube. It was observed that the nondimensional critical shear stresses showed deviation from those of the noncohesive model results at a fines content greater than 50%-55%. An empirical relation that shows the relation between the boundary shear stress deviation and the percent fines in the tailings was proposed. Regression analysis of the experimental results showed that a power law relationship could reasonably be used to describe the relation between the measured nondimensional excess bed shear stress and the erosion rate. It is proposed that the value of b (the erosion rate constant) could be taken as 1 for mine tailings that show cohesive behavior.

The significance of fines on the cohesive behavior of mine tailings has been investigated by examining the incipient motion of the tailings. Sixteen laboratory experiments were performed in a Plexiglas laboratory annular column on re-constituted mine tailings under a 50 cm water cover. Re-suspension was produced by a Teflon stirrer and the velocity field in the column was characterized using a laser Doppler velocimeter (LDV). The pressure change in the boundary layer was also measured with a Preston tube. It was observed that the nondimensional critical shear stresses showed deviation from those of the noncohesive model results at a fines content greater than 50%–55%. An empirical relation that shows the relation between the boundary shear stress deviation and the percent fines in the tailings was proposed. Regression analysis of the experimental results showed that a power law relationship could reasonably be used to describe the relation between the measured nondimensional excess ...

A morphodynamic model for the Jadebusen basin based on the current DELFT3D model is established. With morphological information such as qualitative measurements of SPM-concentration (Suspended Particular Matter) and bottom change estimates as well as detailed surveys of a sand pit refilling process the model parameters for cohesive transport (Partheniades 1965) are calibrated. Within a period of 8 month, which is condensed to a representative period of 28 days for the modeling, almost 45 % of the initial pit volume was refilled with mud. Despite the lack of specific field measurements a setup of mud transport parameters can be defined, which allows further investigations of sand pit locations in the Jadebusen basin. On major outcome is that critical erosion shear stresses for mud should be spatially varied in order to account for the different consolidation states of the mud fraction. Furthermore the paper addresses the problem of the initial grain size distribution for graded sedim...

Storage of fine-grained (<63 µm) sediment and associated contaminants within river channels frequently represents an important component of a catchment's suspended sediment and geochemical budget. It has also been increasingly identified as a cause of degradation of aquatic habitats. Such problems are particularly evident in lowland permeable catchments in the UK, where the groundwater dominated hydrological regimes with a lack of high magnitude flows are conducive to sediment accumulation. In-channel storage of fine-grained sediment and a range of sediment-associated contaminants (C, Cd, Co, Cr, Cu, N, total P, Pb, Zn) has been documented for a total of 45 sampling sites using the findings of a regular bimonthly field sampling campaign in three contrasting lowland permeable catchments. The data demonstrate the spatial and temporal variability of both sediment storage and its contaminant content and provide a means of estimating the total storage of fine-grained sediment and associated contaminants within the main channel system of each study area.

Sediment Transport Model For Storm Sewer Networks To wards the Operational Risks.Sediment transport in sewer networks can be critical in economical and safety point of view. To improve the operation of the sewer networks we are presenting a model, which is capable of numerical simulations of the sediment transport in storm water network. The developed model is calculating the change of the particle distribution of the sediment fractions including the effects of settling and mixing up processes. The results of the model calculations in a simplified network are also presented. We are also planning to apply the developed sediment transport module by coupling to a hydrodynamic simulation for practical tasks supporting the design and operation of sewers networks. Key-words: sediment transport, storm water network, hydrodynamic simulation, sewer design and operation

Morphological modelling aims to explain and predict the changes in rivers, seas and estuaries due to these interaction. In recent history, a lot of progress has been made, especially with stability analysis approaches. However, so far only the physical interactions have been taken into account. It is known however, that biological factors are important to the dynamics of the water systems. In this paper a first step is made in the inclusion of biology into the morphodynamic models. This inclusion is based on the effect that benthic organisms have on the erodibility of the bed. This can easily be included by a change of the critical bed shear stress. These changes in the critical bed shear stress then influence the morphology. This idea has been applied to two cases. The results of the first case indicate that this approach can reproduce the influence of benthic organisms on the mud content of the bed in estuaries. The second case shows that even low numbers of organisms can influenc...

Morphological modelling aims to explain and predict the changes in rivers, seas and estuaries due to these interaction. In recent history, a lot of progress has been made, especially with stability analysis approaches. However, so far only the physical interactions have been taken into account. It is known however, that biological factors are important to the dynamics of the water systems. In this paper a first step is made in the inclusion of biology into the morphodynamic models. This inclusion is based on the effect that benthic organisms have on the erodibility of the bed. This can easily be included by a change of the critical bed shear stress. These changes in the critical bed shear stress then influence the morphology. This idea has been applied to two cases. The results of the first case indicate that this approach can reproduce the influence of benthic organisms on the mud content of the bed in estuaries. The second case shows that even low numbers of organisms can influenc...

ASSESSING ENERGY REGIME EFFECTS ON PATHOGEN-PARTICLE INTERACTIONS LINKING WATER QUALITY TO ECOSYSTEMS AND PUBLIC HEALTH Sandra M. Tirado. Advisors: University of Guelph , 2012 Dr. S.N. Liss Dr. I.G. Droppo Dr. S.M. Glasauer Dr. M. Habash Floc-pathogen interactions are important determinants of the fate of pathogens in aquatic systems. The dissociation of bacteria from particles due to shear stress can significantly increase the presence of free-floating pathogenic bacteria in the aqueous phase. This has implications for pathogen transport and water quality. This study evaluated the interactions of water-borne pathogens with particles in selected aquatic ecosystems. Three experimental chapters and one concluding chapter is presented. Chapter 3 assesses the strength of the floc-microorganism association under different energy levels in relation to the physico-chemical properties and the bioorganic content of flocs from six different aquatic environments (SB, CSO, RF, AG, ML, MN); Chap...

The problem of estimating entrainment rates for cohesive bed sediments has been approached. An analysis procedure was developed for characterizing entrainment of cohesive bed sediments using a device called a Particle Entrainment Simulator (PES), which simulates bed shear effects on sediment entrainment. While most of the available techniques to calculate entrainment rates are based on theoretical parameterizations using the flow field, the PES technique and its method of analysis provide a tool to directly measure entrainment, under controlled laboratory settings, representative of existing or predicted conditions of bed stress, sediment compaction and cohesion, and (if any) bioturbation. The analysis procedure calculates entrainment rates using data generated from experiments conducted on sediment cores with the PES. The procedure was applied to determine entrainment rates for two different marine sites. The first, in Puget Sound, was used to validate the procedure with field data for a tidally-dominated period of time. Entrainment rates were calculated at a second site on Hudson Shelf Valley where storm generated wave and current effects are important. Suspended sediment concentration distributions in the water column were calculated at both sites using PES-generated entrainment-stress functions. Good agreement was reached between the calculated and observed suspended sediment concentrations at 5 m above the bed for the Puget Sound application. Observations were not available for suspended sediment concentration comparisons for the Hudson Shelf Valley application.

A hydrodynamic-ecological model is used for the numerical study of coastal pollution in the Thermaikos Gulf. It is composed by a wind-induced circulation component, and by an advection-dispersion module of ten different quality parameters. These parameters are: chlorophyll-a, organic nitrogen, ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, organic and inorganic phosphorus, BOD, dissolved oxygen, and coliforms. The study of the results obtained for different conditions revealed the influence of the wind direction on the distribution of pollution loads in the Thermaikos Gulf.

have limited widths and lengths. The flow and the hydraulic properties of the meandering river, the amount of sand moving along the bed, and the rate of bank erosion determine these limits. When a bend reaches this width, a chute forms and a new bend develops farther downstream. Distorted bends and natural cutoffs are caused by local changes in the character of bank materials. Several hypotheses have been brought forward to explain meandering. Meandering has been attributed to the earth's rotation; to the excessive slope and energy of a river (

Intertidal flats regularly emerge and submerge in accordance with changes to the water level occurring over tidal cycles. The alteration between wet and drained states may affect the sediment water content, and so the erosion properties of intertidal sediments. This study examined the influence of ambient temperature on the erodibility of exposed cohesive sediment from an intertidal mudflat in the Firth of Thames, New Zealand, in December 2017 and March 2018. The EROMES device was used to measure the erosion potential of sediment (erosion threshold, τ cr N m −2 , and erosion rate, ER g m −2 s −1). Samples were drained and exposed to temperatures of 0, 8, 25 and 40°C, chosen to mimic natural exposed conditions, while submerged samples simulated natural flooded conditions. Results showed that the cohesive sediment became more resistant to erosion when exposed to air compared with submerged samples as a consequence of decreased water content. The water content of exposed sediments decreased by 1.01-1.78 times, a rate which was a function of increasing temperature. The τ cr of exposed experiments was 1.2 to 2.2 times higher, whereas ER decreased 1.2 to 6.2 times. Both the December 2017 and March 2018 sampling dates showed a similar pattern of increasing resistance to erosion (higher τ cr and lower ER), which corresponded to depleted water content of the exposed sediment at higher temperatures.

Studies on suspended sediment concentrations at a seasonal scale play a vital role in understanding coastal hydrodynamic processes in an area. Assessment of spatiotemporal changes in suspended sediments in nearshore areas has gained complexity due to the utilization of conventional methods; this issue can be successfully solved nowadays using multi-temporal remotely sensed images with the help of advanced image processing techniques. The present study is an attempt to demonstrate the model algorithm used to extract suspended sediment concentrations using Landsat 8 OLI (Operational Land Imager) sensor images. The study was executed in a near-offshore area of the Thiruvananthapuram coast, southern India, and focused on the extraction of suspended sediment concentrations and their seasonal variability during pre-monsoon and post-monsoon periods. The OLI images were pre-processed to obtain the actual reflectance using the FLASSH module of the ENVI v5.5 software. The generic model developed herein is designed to compute the spectral reflectance variability between coastal water and suspended sediments and to differentiate the spatial accumulation of the suspended sediment concentrations from the coastal water at the pixel scale. Maximum (0.8 % in near-infrared bands) and minimum (0.6 % in blue bands) spectral reflectance indicates the occurrence of suspended sediments in the coastal water. The model-derived results revealed that the suspended sediment concentration gradually decreased with increasing depth and distance from the shoreline. Higher sediment concentrations accumulated at lower depths in coastal water due to wave and current action that seasonally circulated the sediments. This higher concentration of the suspended sediment load was estimated to be 0.92 mg L −1 at the shallow depths (< 10 m) of the coastal waters and 0.30 mg L −1 at a depth of 30 m. Seasonal variability of suspended sediments was observed in a north-south direction during the pre-monsoon; the reverse was noted during the post-monsoon period. The spatial variability of suspended sediments was indirectly proportional to the depth and distance from the shoreline, and directly proportional to offshore wave and littoral current activity. This study proves that the developed model coupled with the provided computational algorithm can be used as an effective tool for the estimation of suspended sediment concentrations using multitemporal OLI images; furthermore, the output may be helpful for coastal zone management and conservation planning and development.

Land degradation (LD) is a complex process affected by both anthropogenic and natural driving variables, and its prevention has become an essential task globally. The aim of the present study was to develop a new quantitative LD mapping approach using machine learning techniques, benchmark models, and human-induced and socio-environmental variables. We employed four machine learning algorithms [Support Vector Machine (SVM), Multivariate Adaptive Regression Splines (MARS), Generalized Linear Model (GLM), and Dragonfly Algorithm (DA)] for LD risk mapping, based on topographic (n = 7), human-induced (n = 5), and geo-environmental (n = 6) variables, and field measurements of degradation in the Pole-Doab watershed, Iran. We assessed the performance of different algorithms using receiver operating characteristic, Kappa index, and Taylor diagram. The results revealed that the main topographic, geoenvironmental, and human-induced variable was slope, geology, and land use change, respectively. Assessments of model performance indicated that DA had the highest accuracy and efficiency, with the greatest learning and prediction power in LD risk mapping. In LD risk maps produced using SVM, GLM, MARS, and DA, 19.16%, 19.29%, 21.76%, and 22.40%, respectively, of total area in the Pole-Doab watershed had a very high degradation risk. The results of this study demonstrate that in LD risk mapping for a region, topographic, and geological factors (static conditions) and human activities (dynamic conditions, e.g., residential and industrial area expansion) should be considered together, for best protection at watershed scale. These findings can help policymakers prioritize land and water conservation efforts.

According to the United Nations Environmental Program, sand is the second most exploited resource on the planet after water, and local knowledge about the effects of sand mining has been little addressed in international studies. In the case of rivers, the sand and gravel used in the construction industry are part of the fluvial sediments, and the effects are different at each exploitation site. In this article, we propose a theoretical–methodological framework of the sandy field of forces for the study of the socioenvironmental aspects related to the extraction of sand and gravel at the site known as La Isla, located in the Usumacinta River Basin in Mexico. This site has specific environmental and social characteristics. Based on the results of our participation in a research project and, subsequently, on the theoretical, conceptual, and methodological thinking for the social analysis of this site, our model demonstrates how the environmental and anthropic systems converge upon the...

Particle aggregation modifies sediment dynamics, which is a determining factor for morphodynamic and ecological processes in deltaic plains. Here, we investigated the link between intra-annual hydrodynamics variability and flocculation in the Grijalva-Usumacinta system. Monthly (2016–2017) and seasonal (2021–2022) river data was processed using analytical methods and the simplified sonar equation. Flocs were reformed and characterized in the laboratory, validating the in situ settling velocities (0.5–3.8 mm/s) and the existence of large low-density macro-flocs (&gt;300 μm). We verified that flocculation prevailed, exhibiting seasonal patterns; (1) the highest aggregation rates matched the increase in total suspended solids at rising-flow (&gt;100 mg/L), (2) periods of high-flow showed stable aggregation rates, and (3) an influence of marine conditions occurred at low-flow. Particulate phosphorous and organic fraction showed seasonal patterns linked to flocculation. Due to damming, t...

The prediction of the erosion of mudflats is hampered by inaccurate estimates of the erodibility distribution of the sediment bed. To investigate how erodibility varies in space and what the vertical distribution over the sediment depth is, comprehensive observations of the sediment properties, hydrodynamics and bed-level changes were conducted on an intertidal flat in the Western Scheldt Estuary, the Netherlands. The erosion potential on a mudflat is determined by the critical shear stress for erosion (τ e), erosion rate coefficient (M) and local hydrodynamic conditions. A clear difference in hydrodynamic forcing was observed, leading to significant bed level variations at the low water line, where erosion often occurs during very shallow water condition, and a nearly constant bed level at the upper part. The erosion parameters τ e and M could be determined over a sediment bed of 12 cm at the low water line. The erosion coefficient M can be considered constant with depth, although there is a large spreading. A clear vertical variation of τ e was found: τ e increased significantly downward from 0.10 Pa at the sediment surface to 1.13 Pa at 12 cm below the surface. Additionally, there was a strong indication that the presence of diatoms enhanced τ e in the upper 2 mm of sediment by five times of the abiotic τ e (from 0.09 Pa to 0.46 Pa). These findings lead to the following improvement for predicting morphological changes of tidal mudflats: (1) very shallow conditions should be better simulated, (2) the vertical distribution of τ e should be considered. Otherwise, erosion rates can be overestimated, especially during extreme events, because exposure of the deeper well-consolidated layer likely occurs; and (3) an appropriate description of the effect of diatoms should be considered as part of the bottom boundary condition.

River sedimentation is an important indicator for ecological and geomorphological assessments of soil erosion within any watershed region. Sediment transport in a river basin is therefore a multifaceted field yet being a dynamic task in nature. It is characterized by high stochasticity, non-linearity, non-stationarity, and feature redundancy. Various artificial intelligence (AI) modeling frameworks have been introduced to solve river sediment problems. The present survey is designed to provide an updated account of the latest and most relevant AI-based applications for modeling the sediment transport in river basin systems. The review is established to capture the subsequent developments in the advanced AI models applied for river sediment transport prediction. Also, several hydrological and environmental aspects are identified and analyzed according to the results produced in those studies. The merits and constraints of the well-established AI models are further discussed in much detail, particularly considering state-of-the art, modeling frameworks and their application-specific appraisal, and some of the key proposed future research directions. Together with the synthesis of such information to drive a new understanding of models and methodologies related to suspended river sediment prediction, this review provides a future research vision for hydrologists, water scientists, water resource engineers, oceanography and environmental planners.

The estimation of critical shear stress is actually based on the measurement of the corresponding critical water discharge. Incipient motion was recorded by a video camera and the recorded pictures were treated by an automatic image processing system. The measurement results were compared with data taken from the literature. A good agreement between measurements and literature data was obtained. The automatic image processing contributes to a more objective quanti®cation of the sediment transport initiation.

This work reports the results of four ensemble approaches with the M5 model tree as the base regression model to anticipate Sodium Adsorption Ratio (SAR). Ensemble methods that combine the output of multiple regression models have been found to be more accurate than any of the individual models making up the ensemble. In this study additive boosting, bagging, rotation forest and random subspace methods are used. The dataset, which consisted of 488 samples with nine input parameters were obtained from the Barandoozchay River in West Azerbaijan province, Iran. Three evaluation criteria: correlation coefficient, root mean square error and mean absolute error were used to judge the accuracy of different ensemble models. In addition to the use of M5 model tree to predict the SAR values, a wrapper-based variable selection approach using a M5 model tree as the learning algorithm and a genetic algorithm, was also used to select useful input variables. The encouraging performance motivates t...

THE PROCESSES OF EROSION OF COHESIVE SOIL ARE EXAMINED THROUGH A STUDY OF BASIC SOIL INDEX PROPERTIES, SOIL STRUCTURE AND FABRIC, AND PHYSICOCHEMICAL INTERACTION OF SOIL AND WATER. REPORTED STUDIES ARE EVALUATED TO DETERMINE THE FACTORS THAT INITIATE AND SUSTAIN EROSION. A WIDE VARIETY OF TEST PROCEDURES ARE STUDIED, INCLUDING JETS, ROTATING CYLINDERS, TUBE FLOW, FLUMES, AND FIELD DATA. IT IS FOUND THAT GENERALLLY USED SOIL CLASSIFICATION INDEXES HAVE NOT PROVED USEFUL AS EROSION PREDICTORS. STRUCTURAL INDEXES AND INDEXES DESCRIBING THE QUALITY OF THE PORE FLUID AND ERODING FLUID MUST BE ESTABLISHED FOR EACH CASE. INTERNAL AND EXTERNAL FORCE SYSTEMS ARE DEFINED TO ESTABLISH THE RATE AND INITIATION OF EROSION. THE PAPER CONCLUDES WITH A BRIEF STUDY OF SOME CURRENT METHODS USED TO STABILIZE ERODIBLE SOILS IN THE FIELD. /AUTHOR/

Wright et al. Controls on Sediment Bed Erodibility FIGURE 2 | Total suspended solids (TSS) collected 1-m below the surface and 1-m above the bottom (top panels) and salinity contours (bottom panels) along the York River estuary during low river discharge (left panels) and high river discharge (right panels) Adapted by permission from Springer Nature, Estuaries (Lin and Kuo, 2001), copyright 2001.

Laboratory experiments performed in a recirculating flume were designed to quantify the bioturbation influence of the mud snail Hydrobia ulvae, one of the most abundant deposit feeders on European intertidal mudflats. Variations in sediment moisture content that occur between bedforms in shorenormal, ridge and runnel systems of intertidal mudflats were added to the model definition. Sediment erosion thresholds, erosion rates and the microalgal pigment composition of resuspended material were quantified for different H. ulvae densities (0, 1000, 5000, 10 000 and 50 000 snails m− 2) and applied bed shear stresses. Two different sediment moisture contents were tested. In the absence of macrofauna, recorded turbidities increased up to the maximum applied value of 1.6 Pa and the addition of snails increased the resuspended mass at all bed shear stresses tested. The amount of resuspended mass depended on snail density; the amount of resuspended material was highest in sediment test beds that had the highest moisture contents (ridge-type sediments) and snail density. Resuspended and bioturbated sediment was characterised by an enrichment in phaeopigments compared to the underlying sediment. A nine-parameter model, which included sediment moisture content as a new variable, gave a reasonably good estimate of the resuspension of ridge-and runneltype sediments for the range of snail densities. An eight-parameter version of the model was adequate for quantifying erosion rates on intertidal mudflats not characterised by a ridge/runnel geomorphology.

Accurate Suspended Sediment Load (SSL) estimation is very important for water resources quantity and quality studies. In this regard, Sediment Rating Curve (SRC) is a common regression model in predicting SSL of discharge. Studies in this field have shown that the data log-transformation in SRC model causing a bias which underestimates SSL prediction. In this study, using data from the daily flow discharge and suspended sediment discharge of Karaj Dam watershed at Siera station, a 30-year period (1981 to 2011), SRC equation derived, and then, using meta-heuristic algorithms (genetic algorithm and particle swarm optimization algorithm) it was calibrated again. Before modeling to increase the generalization power of the models, using fuzzy clustering method, the data were clustered and then by doing data sampling, they were classified into two homogeneous groups (calibration and test data set). The results show that meta-heuristic algorithms are appropriate methods for optimizing coefficients of SRC model and their results are much more favorable than those of the conventional SRC models or SRC models corrected by correction factors. In this relation, the sediment rating curve models calibrated with meta-heuristic algorithms, by reducing the RMSE of the test data set of 3718.87 ton/day (in the initial SRC model) to 2615/119 ton/day (in the calibrated models by meta-heuristic algorithms) increased the accuracy of suspended sediment load estimation at a rate of 1103.68 ton/day. However, the SRC model corrected by FAO factor decreased the efficiency of initial SRC model by increasing the RMSE of the test data set to 4128/73 ton/day. Using meta-heuristic algorithms in calibrating SRC models also prevents data log-transformation and use of correction factors and increases the accuracy of results.

A particle model to describe and predict sediment transport in shallow water is developed with the use of random walk models. The model is developed by showing consistency between the Fokker-Plank equation and the Advection diffusion equations. Erosion and deposition process in the model are developed probabilistically where the erosion term is considered to be a constant and deposition term is taken as a function by relating sediment settling velocity and diffusion coefficient. Eventually, we simulated the particle model by considering three environment tests. In each environment test the simulations show the distribution of particle and the position of each particle at any given time t. The simulations also show the particles that will finally remain in suspension state and the particles that will be deposited during the transport process following the deployment of 10,000 particles. It was also established that there is uniform distribution of particles in test environment I and III and a linear dependence between the number of particles in different grid cell and the water depth in test environment II.

Suspended sediment load (SSL) time series have three principal inherent components (autoregressive trend, seasonality and stochastic terms) and the overall performance of an SSL modeling tool is associated with the correct estimation of these components. In this study, novel developments of artificial neural network (ANN) models, emotional ANN (EANN) and hybrid wavelet-EANN (WEANN), are employed to estimate the daily and monthly SSL of two rivers (Upper Rio Grande and Lighvanchai) with different hydro-geomorphological conditions. The overall results obtained via autoregressive models, the ANN and EANN, specify the supremacy of EANN (with a few hormonal parameters) against ANN due to the EANN better training the model versus extreme conditions. Also, the obtained results exhibit that the WEANN model could improve the SSL modeling up to 42% and 14% for daily modeling and up to 141% and 87% for monthly modeling in the Upper Rio Grande and Lighvanchai Rivers, respectively.

Studies on suspended sediment concentrations at a seasonal scale play a vital role in understanding coastal hydrodynamic processes in an area. Assessment of spatiotemporal changes in suspended sediments in nearshore areas has gained complexity due to the utilization of conventional methods; this issue can be successfully solved nowadays using multi-temporal remotely sensed images with the help of advanced image processing techniques. The present study is an attempt to demonstrate the model algorithm used to extract suspended sediment concentrations using Landsat 8 OLI (Operational Land Imager) sensor images. The study was executed in a near-offshore area of the Thiruvananthapuram coast, southern India, and focused on the extraction of suspended sediment concentrations and their seasonal variability during pre-monsoon and post-monsoon periods. The OLI images were pre-processed to obtain the actual reflectance using the FLASSH module of the ENVI v5.5 software. The generic model developed herein is designed to compute the spectral reflectance variability between coastal water and suspended sediments and to differentiate the spatial accumulation of the suspended sediment concentrations from the coastal water at the pixel scale. Maximum (0.8 % in near-infrared bands) and minimum (0.6 % in blue bands) spectral reflectance indicates the occurrence of suspended sediments in the coastal water. The model-derived results revealed that the suspended sediment concentration gradually decreased with increasing depth and distance from the shoreline. Higher sediment concentrations accumulated at lower depths in coastal water due to wave and current action that seasonally circulated the sediments. This higher concentration of the suspended sediment load was estimated to be 0.92 mg L −1 at the shallow depths (< 10 m) of the coastal waters and 0.30 mg L −1 at a depth of 30 m. Seasonal variability of suspended sediments was observed in a north-south direction during the pre-monsoon; the reverse was noted during the post-monsoon period. The spatial variability of suspended sediments was indirectly proportional to the depth and distance from the shoreline, and directly proportional to offshore wave and littoral current activity. This study proves that the developed model coupled with the provided computational algorithm can be used as an effective tool for the estimation of suspended sediment concentrations using multitemporal OLI images; furthermore, the output may be helpful for coastal zone management and conservation planning and development.

A particle model to describe and predict sediment transport in shallow water is developed with the use of random walk models. The model is developed by showing consistency between the Fokker-Plank equation and the Advection diffusion equations. Erosion and deposition process in the model are developed probabilistically where the erosion term is considered to be a constant and deposition term is taken as a function by relating sediment settling velocity and diffusion coefficient. Eventually, we simulated the particle model by considering three environment tests. In each environment test the simulations show the distribution of particle and the position of each particle at any given time t. The simulations also show the particles that will finally remain in suspension state and the particles that will be deposited during the transport process following the deployment of 10,000 particles. It was also established that there is uniform distribution of particles in test environment I and III and a linear dependence between the number of particles in different grid cell and the water depth in test environment II.

Sediment motion initiation experiments were performed in a glass rectangular channel, with a loose bed in the central part. The main goal is to obtain the critical hydrodynamic characteristics that causes sediment bed motion initiation, for different cohesionless sediment grain sizes. The optical technique of Particle Tracking Velocimetry (PTV) was used in order to determine the critical velocity profiles for sediment initiation of motion. Between the parameters that define this critical velocity profile is the one known as bed rugosity which represents the height of asperities in the bed. For conditions near bed motion initiation experimental velocity profiles were obtained and they allowed us also to define fluctuating velocities u´, v´ and a value of bed rugosity ks related to a representative grain size of the bed. It was shown that obtained critical velocity profiles are in good agreement with other works in the scientific literature provided an appropriate definition of bed rugosity is made.

Understanding and estimating the distribution and transport of microplastics in marine environments has been recognized as a major global research issue. Most of the existing research on transport modelling has focused on lowdensity particles floating in surface waters, using a 2-D Lagrangian approach and ignoring the vertical displacement of particles. In this work, we evaluate to what extent the vertical movement of particles within surface waters by mixing processes may affect the horizontal transport and fate of microplastics. The aim is to determine whether a 2-D approach is sufficient for the accurate modelling of neusticmicroplastics transport or whether a 3-D approach is necessary. For this purpose, we compare visually and statistically the microplastics transport patterns of three simulations in a coastal system: one using a 2-D approach; and two using a 3-D approach with weak and strong vertical turbulence, respectively. The 2-D simulation roughly reproduced the transport and accumulation patterns, but accurate results required a 3-D approach. This was particularly important for strong vertical turbulence and regions characterized by strong vertical current shear. Moreover, a 2-D approach can lead to errors in the results even with negligible turbulence due to simplifications in the velocity field. A 3-D modelling approach is therefore key to an accurate estimation and prediction of microplastics distribution in coastal systems and consequently for planning mitigation and cleaning programmes.

Storage of fine-grained (<63 µm) sediment and associated contaminants within river channels frequently represents an important component of a catchment's suspended sediment and geochemical budget. It has also been increasingly identified as a cause of degradation of aquatic habitats. Such problems are particularly evident in lowland permeable catchments in the UK, where the groundwater dominated hydrological regimes with a lack of high magnitude flows are conducive to sediment accumulation. In-channel storage of fine-grained sediment and a range of sediment-associated contaminants (C, Cd, Co, Cr, Cu, N, total P, Pb, Zn) has been documented for a total of 45 sampling sites using the findings of a regular bimonthly field sampling campaign in three contrasting lowland permeable catchments. The data demonstrate the spatial and temporal variability of both sediment storage and its contaminant content and provide a means of estimating the total storage of fine-grained sediment and associated contaminants within the main channel system of each study area.

Erosion of cohesive sediment is a complex phenomena and involves various factors comprising effective gravity, dry unit weight, sediment microstructure, particle size distribution, mineralogy, organic content and water chemical condition. The response of cohesive sediment to flow of water has received little attention. In light of this, a study is conducted in the hydraulics laboratory of National Institute of Technology, Kurukshetra. The objective of the study, besides filling up gaps in information, is to make an attempt to establish the effect of certain parameters of cohesive sediment on the erosion process in general and on the incipient motion in particular. The present paper, which is a part of the bigger study, compiles a review of the works by various researchers on the basis of parameters such as shear strength, consolidation pressure, plasticity index, clay content, salinity, compaction water content etc

At the foundations of biogeomorphological processes in the sea lie interactions between the activities of marine benthic animals and the geotechnical properties of their sedimentary environments. The potential significance of these interactions, which take place at a microscale level of millimetres to metres, for the large-scale geomorphology of the seabed has rarely been appreciated. In the context of this review, large-scale is defined as greater than 50 m to hundreds of kilometres. The present review addresses this link, drawing examples from a wide range of marine environments, including estuaries, the intertidal zone, continental shelves and slopes, and the deep sea. It firstly considers sediment stabilisation, slope failure, sediment mixing, biodeposition, sediment compaction, and hydrodynamic effects. This is followed by a consideration of two extremes of the ecological pyramid-the effects of marine meiofauna and marine vertebrates. The final section draws attention to the central role of faunal mucus and extracellular polymeric material (ECPM) in many of the microscale interactions that we describe. The implications of these microscale biological processes and features are discussed in terms of their influence on and control of the large-scale geomorphology of the seabed.

Particle aggregation modifies sediment dynamics, which is a determining factor for morphodynamic and ecological processes in deltaic plains. Here, we investigated the link between intra-annual hydrodynamics variability and flocculation in the Grijalva-Usumacinta system. Monthly (2016–2017) and seasonal (2021–2022) river data was processed using analytical methods and the simplified sonar equation. Flocs were reformed and characterized in the laboratory, validating the in situ settling velocities (0.5–3.8 mm/s) and the existence of large low-density macro-flocs (&gt;300 μm). We verified that flocculation prevailed, exhibiting seasonal patterns; (1) the highest aggregation rates matched the increase in total suspended solids at rising-flow (&gt;100 mg/L), (2) periods of high-flow showed stable aggregation rates, and (3) an influence of marine conditions occurred at low-flow. Particulate phosphorous and organic fraction showed seasonal patterns linked to flocculation. Due to damming, t...

Deposition and storage of fine sediment on channel beds represents an important component of a catchment's sediment budget and can have important implications for sedimentassociated P fluxes, due to storage and remobilisation, and for P concentrations through watersediment interactions. Spatial and temporal variations in P content and storage in fine bed sediment have been studied in two UK lowland catchments, the Rivers Frome and Piddle in Dorset. Fine bed sediment was sampled in representative reaches on a bimonthly basis using a re-suspension cylinder, and the resulting samples were analysed for total P, a range of P fractions and particle size. The results demonstrate significant spatial and temporal variability in PP concentrations and storage, with maximum and minimum P concentrations and storage occurring in late summer and winter, respectively. Temporal variations in concentrations reflect residence times of the sediment and ambient P concentrations, while variations in storage are mainly due to hydrological regimes. Spatial variations reflect catchment characteristics, the location of inputs and local variations in hydrological and channel bed conditions.

Using an erosion chamber, erodibility experiments on two different deep-sea sediments (mainly clayey silt) acquired in the western Pacific Ocean have been conducted to estimate the erosion rate and its potential controlling factors. Overall, the erosion rates of both deep-sea sediments were in the range of 10 −7-10 −5 kg m −2 s −1 which was two or three orders of magnitude lower than that of sediments in shallow environments. Such erodibility, however, exhibited two contrasting patterns depending on the carbonate compensation depth (CCD), which determines carbonate contents in sediments. At one site (MC1), above the CCD, the sediments (carbonate content 18.32 ± 1.00 wt%) were easily resuspended by surface erosion, resulting in a high eroded mass (2.49 × 10 −2 kg m −2 at shear stress of 0.6 Pa). At another site (MC4), below the CCD, the sediments (carbonate content 0.06 ± 0.04 wt%) were less resuspended by floc erosion, resulting in a low eroded mass (3.70 × 10 −3 kg m −2 at shear stress of 0.6 Pa). Over the entire range of bed shear stress, the erosion rate above the CCD was about 1-6 times higher than that below the CCD. The difference in carbonate content between two sites caused different variations in the bed resistance with depth. The erodibility above the CCD was enhanced, probably due to the particle roughness and low bulk density. Once the bed shear stress exceeded about 0.39 Pa, the erosion type of MC1 shifted from depth-limited to transitional erosion. However, the erosion type of MC4 always remained depth-limited over the entire range of bed shear stress. These results underline the effect of calcium carbonate on resuspension and erosion behaviors of the deep-sea sediments.

Although the Korean tidal flats in the Yellow Sea have been highlighted as a typical macrotidal system, so far, there have been no measurements of the sediment erodibility and critical shear stress for erosion (τ). Using the Gust erosion microcosm system, a series of field experiments has been conducted in the Ganghwa tidal flat to investigate quantitatively the effects of biogenic materials on the erodibility of intertidal cohesive sediments. Four representative sediment cores with different surficial conditions were analyzed to estimate the τ and eroded mass. Results show that τ of the &quot;free&quot; sediment bed not covered by any biogenic material on the Ganghwa tidal flat was in the range of 0.1-0.2 Pa, whereas the sediment bed partially covered by vegetation (Phragmites communis) or fecal pellets had enhanced τ up to 0.45-0.6 Pa. The physical presence of vegetation or fecal pellets contributed to protection of the sediment bed by blocking the turbulent energy. An inverse rel...

Erosion of cohesive sediments is a ubiquitous phenomenon in estuarine and intertidal environments. Several methods have been proposed to determine the surface erosion threshold (τc0), which are still debatable because of the numerous and uncertain definitions. Based on erosion microcosm experiments, we have compared three different methods using (1) eroded mass (EM), (2) erosion rate (ER), and (3) suspended sediment concentration (SSC), and suggested a suitable method for revealing the variation of erodibility in intertidal sediments. Erosion experiments using a microcosm system were carried out in the Muuido tidal flat, west coast of South Korea. The mean values of τc0 for three methods were: 0.20 ± 0.08 Pa (EM); 0.18 ± 0.07 Pa (ER); and (3) 0.17 ± 0.09 Pa (SSC). The SSC method yielded the lowest τc0, due to the outflow of suspended sediment from the erosion chamber of the microcosm. This was because SSC gradually decreased with time after depleting the erodible sediment at a given...

The aim of the paper is to investigate in detail the sensitivity of particles displacement based on method of Lagrangian particle tracking in combination with a 3D Eulerian numerical model that was developed by the first author, namely FSUM. The characteristic parameters used for this research include the possibilities of random movement, settling velocity of solid particle, horizontal and vertical diffusion coefficients and condition of particle fixed with a constant distance under water surface. The first part is on the fluid flow model. It includes 3D Navier-Stokes equations together with the initial and boundary conditions that were numerically solved with the finite difference method and coded with FORTRAN 90/95 using parallel technique with OpenMP. A semi-Lagrangian treatment of the advective terms was used. The second part is related to Lagrangian particle tracking model and was solved with the fourth Runge-Kutta method. Model was applied for Strait of Johor and has been calibrated by using measured data on water level and velocity at one station. Eight cases of simulations with many different options were carried out. Through computed cases it shows that random term and settling velocity are very important factors for the behavior of particle trajectory. Although the random diffusion is minor in comparison with flow velocity, but it can rearrange the initial distribution of particles then the cluster of particles become more dispersive during the process of movement. In addition, introducing settling velocity of particle makes a big change on the trajectory of particle that becomes more suitable to sediment transport. The study gave a comprehensive picture on particle movement. The model also showed its possibilities of multiform applications in simulation and prediction for the different problems in practice.

The coastal area of Chalastra (NW Thessaloniki's Gulf, Northern Greece) features prominent mussel farming activity as well as fishing activity. These activities are closely related to the hydrodynamics of the basin's seawaters. The prevailing hydrodynamic force for the circulation of coastal waters of Chalastra is wind stresses. The hydrodynamics of this coastal region may be further influenced by three rivers outflowing to the southwestern part of the basin; however, this runoff has dramatically decreased during the last few decades. Concerning the wind forcing regime, this is distinguished by two characteristic regimes. The first one is realized in winter and the other mainly in summer. Systematic field studies were conducted during one year for current and density measurements. Seawater samples were collected and chemically analyzed for dissolved oxygen, chlorophyll α and nutrients. Data revealed some cases of flow currents of opposite direction between the upper and the lower water layer, and a characteristic captured downwelling which seemed to evolve periodically on a diurnal time scale, especially in summer. Furthermore, a two layer mathematical model was developed and applied for the study of the water circulation and the investigation of downwelling processes under specific conditions; the tracing as well as the temporal and spatial evolution of these hydrodynamic processes in the mussels' culture study area constituted the main aim of the present work. The formation of such events, which were observed mainly during summer periods, may affect the mussels' development and has to be considered when designing farming practices in the area.

The stability of cohesive sediments from Venice lagoon has been measured in situ using the benthic flume Sea Carousel. Twenty four stations were occupied during summertime, and a subset of 13 stations was re-occupied during the following winter. Erosion thresholds and first-order erosion rates were estimated and showed a distinct difference between inter-tidal and sub-tidal stations. The higher values for inter-tidal stations are the result of exposure that influences consolidation, density, and organic adhesion. The thresholds for each state of sediment motion are well established. However, the rate of erosion once the erosion threshold has been exceeded has been poorly treated. This is because normally a time-series of sediment concentration (C) and bed shear stress (t 0 (t)) is used to define threshold stress or cohesion (t crit,z) and erosion rate (E). Whilst solution of the onset of erosion, t crit,0 , is often reported, the evaluation of the erosion threshold variation through the process of erosion (eroded depth) is usually omitted or not estimated. This usually leads to assumptions on the strength profile of the bed which invariably has no credibility within the topmost mm of the bed where most erosion takes place. It is possible to extract this information from a time-series through the addition of a step in data processing. This paper describes how this is done, and the impact of this on the accuracy of estimates of the excess stress (t 0 (t)-t crit,z) on E.

Forest fires present one of the main causes of environmental hazards that have many negative results in different aspect of life. Therefore, early prediction, fast detection and rapid action are the key elements for controlling such phenomenon and saving lives. Through this work, 517 different entries were selected at different times for montesinho natural park (MNP) in Portugal to determine the best predictor that has the ability to detect forest fires, The principle component analysis (PCA) was applied to find the critical patterns and particle swarm optimization (PSO) technique was used to segment the fire regions (clusters).In the next stage, five soft computing (SC) Techniques based on neural network were used in parallel to identify the best technique that would potentially give more accurate and optimum results in predicting of forest fires, these techniques namely; cascade correlation network (CCN), multilayer perceptron neural network (MPNN), polynomial neural network (PNN), radial basis function (RBF) and support vector machine (SVM) In the final stage, the predictors and their performance were evaluated based on five quality measures including root mean squared error (RMSE), mean squared error (MSE), relative absolute error (RAE), mean absolute error (MAE) and information gain (IG). The results indicate that SVM technique was more effective and efficient than the RBF, MPNN, PNN and CCN predictors. The results also show that the SVM algorithm provides more precise predictions compared with other predictors with small estimation error. The obtained results confirm that the SVM improves the prediction accuracy and suitable for forest fires prediction compared to other methods.

According to the United Nations Environmental Program, sand is the second most exploited resource on the planet after water, and local knowledge about the effects of sand mining has been little addressed in international studies. In the case of rivers, the sand and gravel used in the construction industry are part of the fluvial sediments, and the effects are different at each exploitation site. In this article, we propose a theoretical–methodological framework of the sandy field of forces for the study of the socioenvironmental aspects related to the extraction of sand and gravel at the site known as La Isla, located in the Usumacinta River Basin in Mexico. This site has specific environmental and social characteristics. Based on the results of our participation in a research project and, subsequently, on the theoretical, conceptual, and methodological thinking for the social analysis of this site, our model demonstrates how the environmental and anthropic systems converge upon the...

The presence of clay-sized particles and clay minerals in modern sands and ancient sandstones has long presented an interesting problem, because primary depositional processes tend to lead to physical separation of fine-and coarse-grained materials. Numerous processes have been invoked to explain the common presence of clay minerals in sandstones, including infiltration, the codeposition of flocculated muds, and bioturbation-induced sediment mixing. How and why clay minerals form as grain coats at the site of deposition remains uncertain, despite clay-coated sand grains being of paramount importance for subsequent diagenetic sandstone properties. We have identified a new biofilm mechanism that explains clay material attachment to sand grain surfaces that leads to the production of detrital clay coats. This study focuses on a modern estuary using a combination of field work, scanning electron microscopy, petrography, biomarker analysis, and Raman spectroscopy to provide evidence of the pivotal role that biofilms play in the formation of clay-coated sand grains. This study shows that within modern marginal marine systems, clay coats primarily result from adhesive biofilms. This bio-mineral interaction potentially revolutionizes the understanding of clay-coated sand grains and offers a first step to enhanced reservoir quality prediction in ancient and deeply buried sandstones.

The future reliance on water supply and flood control reservoirs across the globe will continue to expand, especially under a variable climate. Construction of additional reservoirs is less likely compared to simultaneous flow and sediment management in existing reservoirs. One aspect of this sediment management is related to the control of upstream sediment sources. However, key research questions remain regarding upstream sediment loading rates. Highlighted in this article are research needs relative to measuring sediment transport rates and loading due to streambank and gully erosion within a watershed. For example, additional in-stream sediment transport and reservoir sedimentation rate measurements are needed across a range of watershed conditions, reservoir sizes, and geographical locations. More research is needed to understand the intricate linkage between upland practices and in-stream response. A need still exists to clarify the benefit of restoration or stabilization of a small-reach within a channel system or maturing gully on total watershed sediment load. We need a better understanding of the intricate interactions between hydrological and erosion processes to improve prediction, location, and timing of streambank erosion and failure and gully formation. Also, improved process-based measurement and prediction techniques are needed that balance data requirements regarding cohesive soil erodibility and stability as compared to simpler topographic indices for gullies or stream classification systems. Such techniques will allow the research community to address the benefit of various conservation and/or stabilization practices at targeted locations within watersheds.

River sedimentation is a global concern evidenced by a number of studies conducted. Now, that climate change is being experienced the rapid changes on the river landscape is manifestly observed. As unveiled, natural evolution of landscape and human activities are the two main factors affecting this phenomenon. Different methods of determination of the volume of sediments transported some are employed. Some studies used classic methods utilizing sophisticated apparatus while others artificial intelligence mode of sediment transport prediction.

The aim of the paper is to investigate in detail the sensitivity of particles displacement based on method of Lagrangian particle tracking in combination with a 3D Eulerian numerical model that was developed by the first author, namely FSUM. The characteristic parameters used for this research include the possibilities of random movement, settling velocity of solid particle, horizontal and vertical diffusion coefficients and condition of particle fixed with a constant distance under water surface. The first part is on the fluid flow model. It includes 3D Navier-Stokes equations together with the initial and boundary conditions that were numerically solved with the finite difference method and coded with FORTRAN 90/95 using parallel technique with OpenMP. A semi-Lagrangian treatment of the advective terms was used. The second part is related to Lagrangian particle tracking model and was solved with the fourth Runge-Kutta method. Model was applied for Strait of Johor and has been calibrated by using measured data on water level and velocity at one station. Eight cases of simulations with many different options were carried out. Through computed cases it shows that random term and settling velocity are very important factors for the behavior of particle trajectory. Although the random diffusion is minor in comparison with flow velocity, but it can rearrange the initial distribution of particles then the cluster of particles become more dispersive during the process of movement. In addition, introducing settling velocity of particle makes a big change on the trajectory of particle that becomes more suitable to sediment transport. The study gave a comprehensive picture on particle movement. The model also showed its possibilities of multiform applications in simulation and prediction for the different problems in practice.

Chacao channel bridge is located in a tidal channel with highly-energetic hydrodynamics conditions and significant erodibility potential. Once finished, this 2.5 km long cable-stayed bridge will be the largest in South-America. Here we report an integrated procedure to estimate scour around two of its three towers, both located on a relatively complex but different soil matrices. A high-resolution hydrodynamic model based on the Reynolds-averaged Navier–Stokes equations (RANS), physical tests of in situ soil samples in a Rotating Erosion Testing Apparatus (RETA) and empirical formulas for scour estimation are combined to provide a reliable estimation of scour depth under a periodic tidal ebb-flow regime. The relatively homogeneous soil material at the North Tower shows a high susceptibility to hydrodynamic erosion, which is estimated with SRICOS methodology. The Central Tower, in contrast, needs a combined approach based on the current state of the rock, information collected from u...