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A Simulation Model for the Infiltration of Sediment Into Spawning Gravel
Abstract
Thesis (M.S.)--Humboldt State University, 1991. Includes bibliographical references (leaves 24-25). Typescript (photocopy).
... Notwithstanding, there is little understanding of the conditions that favour saturation when fine material percolates in the bed, driven only by gravitational forces. Different authors have developed theoretical (Sakthivadivel & Einstein, 1970;Lauck, 1991;Cui et al., 2008), numerical and empirical models to describe the vertical distribution of percolated fines. Some of these models require an a priori definition of the saturation conditions to attain stability. ...
... A number of empirical and semiempirical models have been published that determine the volume fraction of solids in granular materials (e.g. Westman, 1936;Yu & Standish, 1988, 1991Finkers & Hoffmann, 1998;Liu & Ha, 2002). These models were developed mostly for the chemical industry, where packing efficiency affects various processes, and maximization of the packing density of granular material products is a major factor in reducing transportation costs. ...
... The Yu & Standish multifractional packing porosity model Yu & Standish (1988, 1991 developed a multifractional porosity model, based on a detailed empirical description of the interaction between binary mixtures, which was then extended to arbitrary mixtures. The applicability of this model to any arbitrary number of size fractions makes it highly valuable to sedimentology, where extremely bimodal sediments are rare (Frings et al., 2008). ...
Fine particles may infiltrate through coarse alluvial beds and eventually saturate the subsurface pore space. It is essential to understand the conditions that lead to bed saturation, and to forecast the packing characteristics of saturated beds to assess the effect of excess fine sediment supply on a number of processes that occur in the stream-sediment boundary. To address this problem, in this study, a new method is introduced to predict the grain-size distribution for the saturated condition, and the resulting porosity decrease, given the characteristics of the bed and the supplied sediments. The new method consists of the numerical aggregation of infilling fines in a finite bed volume, during which the bed properties change to affect further infilling. An existing semi-empirical, particle packing model is implemented to identify these properties. It is shown that these types of models are adequate to describe regimes of natural sediment fabric quantitatively, and are thus useful tools in the analysis of sediment infiltration processes. Unlike previous developments to quantify saturated bed conditions, which assume that the supplied material is uniform and finer than the bed pore openings, the method developed herein considers poorly sorted fines, and can identify size fractions that are able to ingress into the bed due to being smaller than the particles that form the bed structure. Application of the new method to published experimental data showed that the final content of infiltrated fines is strongly sensitive to the initial bed packing density, highlighting the need to measure and understand open-work gravel deposits. In addition, the new method was shown to be suitable for assessing the degree of bed saturation, when it was applied to a published data set of field samples.
... Theoretical and modelling approaches were developed following the early laboratory investigations of clogging (Lauck, 1991;Sakthivadivel and Einstein, 1970). For instance, Lauck (1991) developed a model to predict the infiltration of fine sediments in coarser streambed and demonstrated that fine sediments penetrate only to a limited depth, however, it also justified Einstein's result and regarded it as a special case where size of bed particles is substantially greater than infiltrating particles. ...
... Theoretical and modelling approaches were developed following the early laboratory investigations of clogging (Lauck, 1991;Sakthivadivel and Einstein, 1970). For instance, Lauck (1991) developed a model to predict the infiltration of fine sediments in coarser streambed and demonstrated that fine sediments penetrate only to a limited depth, however, it also justified Einstein's result and regarded it as a special case where size of bed particles is substantially greater than infiltrating particles. Over the years, these models have been modified and more realistic theory of fine sediment infiltration has been developed . ...
... In addition to laboratories and field tests, Sakthivadivel and Einstein [11] established a model to characterize the infiltration process of fine sediment through a porous column due to intra-gravel flow, following the conservation of mass for fine sediment and through correlating the probability that fine sediment particles lodge in place as a result of intra-gravel flow velocity. Lauck [12] built a model that describes the infiltration process, assuming sediment infiltration occurs as a stochastic process of particles falling into a predefined space. Einstein [9] developed models for simulating the infiltration process with several assumptions, where a fine particle is classified when its pore size is smaller than that of a clean coarse particle. ...
... These studies were based on the mass conservation for fine fraction transported through gravel matrix. According to the theory of Cui et al. [3], developed from Lauck [12], the amount of the transported fine sediment trapped in immobile gravel is dependent on the riverbed characteristics, which include porosity, grain size ratio, and the fine fraction contained in the bed. Thus, the trapping coefficient was introduced, which depends on the ratio of fraction of fine sediment and the maximum amount of fine sediment that can be contained in gravel (saturation state). ...
Large amounts of fine sediment infiltration into void spaces of coarse bed material have the ability to alter the morphodynamics of rivers and their aquatic ecosystems. Modelling the mechanisms of fine sediment infiltration in gravel-bed is therefore of high significance. We proposed a framework for calculating the sediment exchange in two layers. On the basis of the conventional approaches, we derived a two-layer fine sediment sorting, which considers the transportation of fine sediment in the form of infiltration into the void spaces of the gravel-bed. The relationship between the fine sediment exchange and the affected factors was obtained by using the discrete element method (DEM) in combination with feedforward neural networks (FNN). The DEM model was validated and applied for gravel-bed flumes with different sizes of fine sediments. Further, we developed algorithms for extracting information in terms of gravel-bed packing, grain size distribution, and porosity variation. On the basis of the DEM results with this extracted information, we developed an FNN model for fine sediment sorting. Analyzing the calculated results and comparing them with the available measurements showed that our framework can successfully simulate the exchange of fine sediment in gravel-bed rivers.
... wires.wiley.com/water in clarifying the mechanisms under different combinations of suspended particles, bed sediments, and hydrodynamic conditions, 4 and researchers have also developed theoretical, mathematical, and probabilistic models, e.g., the models by Lauck 64 and Herrero and Berni. 58 The process of colmation encompasses the entry of finer material into the coarser matrix of the bed (normally sands, silts, and clays moving into gravels and/or cobbles; or silts and clays entering a sand substrate); its filtration to the hyporheic zone below; and the formation of a layer which reduces the permeability of a streambed compared to the initial conditions. ...
... The Lauck 64 model has also reproduced the key observations from other studies 38,43,65,66,69 that fine sediment can only infiltrate to a finite depth if the bed material is sufficiently thick. Subsequently, Cui et al. 56 developed a theory to describe the processes of colmation based on Lauck, 64 and this states that the highest possible fine sediment fraction resulting from fine sediment infiltrating an immobile clean gravel deposit is an exponential decay function with depth into the bed material. Thus, well-sorted gravels with large pores are conducive to deeper colmation, whereas in poorly-sorted streambed sediments with smaller pore sizes the colmation depth is relatively shallow, although the presence of macropores can enable the movement of fines through poorly sorted sediments to deeper layers. ...
The accumulation of fine sediments in rivers is a pernicious problem with wide-ranging consequences for the healthy functioning of rivers throughout the world. It is linked to a range of landuse changes and human activities that have increased sediment inputs leading to elevated fine sediment loads that exceed the sediment transport capacities of rivers. Surficial deposits of fine material can also create the conditions for fine sediment to move into and accumulate within the coarser bed substrate, a process known as colmation and the focus of this review. Colmation, also referred to as clogging, fine sediment infiltration, fine sediment deposition, ingress, infilling, intrusion of fines, siltation, and the surface–subsurface exchange of particles, is particularly damaging to river habitats and ecosystems. It causes degradation through the physical effects of reduced porosity and flow connectivity and the biogeochemical changes arising from the hydraulic and hydrological impacts and the effects of sediment-bound contaminants, all of which can impact on river ecology. Different aspects of the phenomenon of colmation have been studied across a number of disciplines and over several decades and this paper synthesizes this wide literature to provide a multidisciplinary perspective on the mechanisms, causes, and impacts of colmation and discusses some key management challenges. For further resources related to this article, please visit the WIREs website.
... Infiltration of sediment, on the other hand, has an influence on the development of the stratigraphic record; preservation of fine-grained laminae, formed by deposition from suspension downstream of the leeside of sediment waves, is enhanced by infiltration of fine grains in the upper parts of underlying laminae [Frostick et al., 1984;Bridge and Best, 1997;Lunt and Bridge, 2007]. Concerning riverbed morphological adjustments, sediment infiltrated through the bed framework, before the surface layer is saturated with fines, should not be considered for computation of bed level changes, inasmuch as this material fills the bed pores without disturbing the skeleton of large grains [Frings et al., 2008[Frings et al., ]. et al., 2013, by field measurements [Frostick et al., 1984;Lisle, 1989;Sear, 1993] and theoretically [Sakthivadivel and Einstein, 1970;Lauck, 1991;Cui et al., 2008;N uñez-Gonz alez et al., 2016]. Field and experimental observations for an initially clean gravel deposit have shown that for very fine intruding sediment in relation to the bed material, fines penetrate deep and fill the bed from underlying layers up (a process called unimpeded static percolation by Kleinhans [2002] and Gibson et al. [2009]); conversely, for coarser intruding particles, there is a rapid decrease in depth of infiltrated fines, so that bed filling proceeds from the surface down. ...
Percolation of fine sediment is a common process in gravel-bed rivers, which often exhibit extended and overlapping grain size distributions of the bed and the supplied fine sediment. Yet, existing sediment infiltration theory assumes well-sorted fine material with smaller grain size than the bed pores, and as such, is not suitable for many situations encountered in gravel-bed streams. Previous developments for infiltration of uniform material are here generalized to consider poorly-sorted sediment mixtures. Governing equations and a numerical solution to model the vertical distribution of infiltrating sediment are presented. The equations are solved as a function of a trapping coefficient, dependent on the relative size of infiltrating fines in relation to bed material. A method is developed to generate equivalent grain size distributions to calculate the trapping coefficient, when grain sizes of the infiltrating and bed materials overlap. Moreover, a bed cutoff size is defined and computed with a semi-empirical packing-porosity model, to distinguish particles smaller than the bed pores. Published experimental data are used to test the new model and calibrate the trapping coefficient. It is shown that this coefficient is highly sensible to the fine and coarse tails of fine and coarse materials grain size distributions. Accordingly, calibrated values of the coefficient are set as a function of a mean size ratio, computed from the geometric mean of the tails of the size distributions. Incorporating this relation, the model performed well in reproducing indirect observations of sediment infiltration from experiments reported in the literature. This article is protected by copyright. All rights reserved.
... It is also possible that top layers will fill while bottom layers will remain untouched by sediment. For further details, and more sample runs see Lauck (1991). For top layers, the first layer accumulated the most sediment with layer two containing a lighter load of finer sediment. ...
Salmonid embryos depend on the adequate flow of oxygenated water to survive and in- terstitial passageways to emerge from the gravel bed. Spawning gravels are initially cleaned by the spawning female, but sediment transported during subsequent high-runoff events can nfiltrate the porous substrate. In many gravel-bed channels used for spawning, most of the infiltrating sediment consists of sand and fine gravel that fall by the force of gravity through the framework of bed particles once the sediment enters the streambed. The sediment comes to rest on the tops of large particles or lodges in pores created by bed particles in mutual contact. We present a model that simulates the descent and deposition of heterogeneous spheres (sediment) into successive layers of a bed of heterogeneous spheres. Individual sedimentary particles may lodge or pass through a pore depending on its diameter relative to those of the bed particles creating the pore. As sediment lodges in each layer, the particle-size distribution of the layer is updated to give a new population of pores through which the next group of sedimentary particles attempts to infiltrate. Transformations of percentile-by-weight distribu- tions are used in the simulation both to generate random sediment particles and to simulate pores in the bed. Results using particle-size distributions from a natural channel show vertical variations in amount and particle size of infiltrating sediment. Top layers accumulate large amounts of relatively coarse sediment, middle layers accumulate little sediment, and bottom layers accumulate large amounts of fine sediment. This agrees qualitatively with direct measurements of sediment infiltration in this channel. Simulations using other arbitrary distributions show that the total volume, depth, and particle-size distribution of infiltrating sediment vary with the particle-size distribution of the sediment and streambed.
... However, for cases of silt particles infiltrating a gravel bed already saturated with sand, the downward movement of silt particles could be driven by a combination of gravity and downward intra-gravel flow. Despite the differences in the driving forces for the downward movement of fine sediment particles, because particle lodging is a function of geometric fitting [Lauck, 1991], the mechanisms and processes affecting fine sediment particles clogging the pores of the deposit and forming a surface seal impeding further infiltration do not change. This hypothesis is supported by the theory presented by Cui et al. [2008], who found that the partial differential equations describing gravity driven and intro-gravel flow driven fine sediment infiltration processes behave similarly. ...
We present results and analyses from flume experiments investigating the infiltration of sand into immobile clean gravel deposits. Three runs were conducted, each successive run with the same total sediment feed volume, but a 10-fold increase in sand feed rate. The highest sand feed rate produced less sand infiltration into the subsurface deposits than the other two runs, which had approximately equivalent amounts of sand infiltration. Experimental data, combined with simple geometric relations and physical principles, are used to derive two relations describing the saturated fine sediment fraction in a gravel deposit and the vertical fine sediment fraction profile resulting from fine sediment infiltration. The vertical fine sediment fraction profile relation suggests that significant sand infiltration occurs only to a depth equivalent to a few median grain diameters of the bed material.
The permeability of sediments at the sediment–water interface is an important control on several stream ecosystem services. It is well known that streambed permeability varies over several orders of magnitude, however, the environmental processes influencing this variation have received little attention. This review synthesizes the state-of-art knowledge and gaps in our understanding of the key physical and biological processes which can potentially modify the streambed permeability. These processes include—(a) physical clogging due to fine sediments, (b) biological clogging due to microbial biomass, and (c) sediment reworking by in-stream fauna. We highlight that the role of biotic processes (bioclogging and sediment reworking processes) in modifying the streambed permeability has not been investigated in detail. We emphasize that complex feedback mechanisms exist between these abiotic and biotic processes, and an interdisciplinary framework is necessary to achieve a holistic understanding of the spatio-temporal variability in streambed permeability. To this end, we propose to develop a conceptual model for streambed evolution after a disturbance (e.g. floods) as this model could be valuable in comprehending the dynamics of permeability. We also outline the challenges associated with developing a widely applicable streambed evolution model. Nonetheless, as a way forward, we present a possible scenario for the evolution of a streambed following a high flow event based on the trajectory of responses of the above-mentioned environmental processes. Finally, we suggest future research directions that could assist in improving the fundamental understanding of the clogging and sediment reworking processes and consequently of the dynamics of streambed permeability.
Fine sediment infiltration into a river bed is a physical process affected by different human actions and has several environmental, socioeconomic, and river morphology consequences. A theoretical model is proposed herein aiming to reproduce the fine sediment content depth profile resulting from the infiltration of fine sediment into an initially clean gravel bed. The model is based on the probability of infiltrating particles to be trapped in a pore throat formed by three bed particles. The model is tested against previous experimental results and is found to reproduce adequately the occurrence of the two infiltration mechanisms reported by previous studies: bridging and unimpeded static percolation. Theoretical depth profiles are found to underestimate fine sediment content at the bed subsurface (below 2–3 gravel diameter depth) compared to the laboratory results. This may be due to hyporheic flow that is not taken into account in our model. In flow experiments, the particles previously infiltrated and deposited might be destabilized by pore water flow and their fall down to the bed might be magnified.
A theoretical model is developed to describe the process of fine sediment infiltration into immobile coarse sediment deposits. The governing equations are derived from mass conservation and the assumption that the amount of fine sediment deposition per unit vertical travel distance into the deposit is either constant or increases with increasing fine sediment fraction. Model results demonstrate that fine sediment accumulation decreases rapidly with depth into coarse substrate initially void of fine sediment, which is consistent with experimental observations that significant fine sediment infiltration occurs to only a shallow depth. Comparisons of the theory with flume data indicate that the model adequately reproduced the weighted-averaged fine sediment fraction values from experiments. An early model developed by Sakthivadivel and Einstein for fine sediment infiltration is in part based on the generally incorrect assumption that intragravel flow remains constant following fine sediment infiltration. Applying a correction to the Sakthivadivel and Einstein model based on alternate hypothesis that introgravel flow is driven by a constant head gives similar results as the proposed model.
A simulation model [Salmonid Spawning Analysis Model (SSAM)] was developed as a management tool to evaluate the relative impacts of stream sediment load and water temperature on salmonid egg survival. The model is useful for estimating acceptable sediment loads to spawning habitat that may result from upland development, such as logging and agriculture. Software in common use in the USA were adapted for use in gravel bedded rivers and linked to simulate water temperature (the USFWS Instream Water Temperature, SNTEMP model) and water and sediment routing (the USAE Scour and Deposition in Rivers and Reservoirs, HEC-6 model, version 3.2). These models drive the redd (spawning nest) model (the USDA-ABS Sediment Intrusion Dissolved Oxygen SIDO model) which simulates sediment intrusion and dissolved oxygen concentration in the redd environment. The SSAM model predictions of dissolved oxygen and water temperature compared favorably with field data from artificial redds containing hatchery chinook salmon eggs.
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