International Journal of Sediment Research最新文献

The seafloor environment is prone to rapid changes caused by landslides, which can result in significant human, financial, and environmental consequences. Previous research efforts have primarily focused on studying rigid submerged landslides using physical experiments and mesh-based numerical simulations. However, there is a need to investigate deformable soil masses due to their inherent complexity. In the current study, a smoothed particle hydrodynamics (SPH) method was developed to examine the behavior of submerged landslides. Three rheological models, namely Bingham, Herschel–Bulkley (H–B), and μ(I), were applied to characterize the properties of the sediment materials. The SPH governing equations were modified at the interface between the water and sediment phases to account for the density discontinuity between them. The viscosity term at this interface was determined using the Owens equation. The effective pressure, a crucial parameter in rheological models, was appropriately modified to reflect the influence of the water column on the sediment particles, utilizing a simple algorithm. For the μ(I) rheology, separate equations were applied to describe the behavior of dry and saturated conditions. Additionally, the Mohr–Coulomb criteria were utilized in the Bingham and H–B models to determine the yield stress. To validate the effectiveness of the proposed modeling approach, a column failure scenario was first simulated. Subsequently, a rigid submerged landslide was investigated to assess the capability and validity of the proposed framework in accurately capturing surge wave generation and calibrating the boundary friction factor. Finally, two deformable submerged landslides involving different materials, namely sand and glass beads, were simulated and compared with previous experimental and numerical studies at different time steps. Through these comprehensive investigations, the current understanding of the complex behavior exhibited by submerged landslides is enhanced, and valuable insight into landslide dynamics is provided.

A root system is an important factor to increase soil resistance to detachment of soil particles. However, due to the large number of species, there is a need for studying the impacts of native plant species on soil quality and soil erodibility. This investigation did flume experiments at various soil slopes (9.2%, 18.1%, 25.1%, and 32.5%) and different water flow rates (0.56, 0.67, 0.74, 0.81, and 0.94 L/(m·s)), to evaluate sediment detachment capacity caused by rills (D_c) and rill erodibility (K_r) as well as the soil quality of hillslopes with three common species including Carpinus betulus (as a natural tree species), Alnus glutinosa (as a planted tree species) and Mespilus germanica (as a shrub species) in forestland of northern Iran. The variability of D_c has been associated with soil properties and root characteristics of Carpinus betulus. D_c was significantly lower (average, −45%) for soils under Carpinus betulus compared to soils with the two other plant species (p < 0.01). This was due to the higher values of soil properties including medium weight diameter of soil aggregates (MWD), organic carbon (OC), total nitrogen (TN), total phosphorous (TP), potassium (K), calcium (Ca), magnesium (Mg) as well as to the more extended root system, as confirmed by the negative correlations between D_c and the studied variables. K_r also was different among the studied soils and plant species. The root system of Carpinus betulus also played a useful role for increasing soil resistance to rill erosion yielding a safety factor (1.61) in the studied forest ecosystem. Overall, the current study supports a broader use of native species (such as Carpinus betulus) in areas exposed to surface erosion and instability, as an effective eco-engineering conservation technique and an alternative technology instead of utilizing artificial and expensive management practices.

This paper presents a model to characterize the distribution of non-uniform sediment in suspension above erodible sediment beds in turbulent flow under non-equilibrium conditions. The modeling process incorporates three crucial features of sediment-laden flow: mixing length, stratification, and settling velocity. The advection–diffusion equation for the $k$-th grain-size class is modified accordingly. The model's calculations encompass the determination of reference height and reference concentration, accounting for the presence of different-sized particles in the flow. The numerical solution of the model effectively captures concentration variations for distinct particle sizes in streamwise and vertical directions, as well as temporal changes. As experimental data under non-equilibrium conditions with different sediment sizes are unavailable, the study focuses on specific experiments involving various sediment beds with a mixture of different grain sizes under equilibrium conditions. The current findings reveal that the concentration magnitude decreases downstream with time for all grain sizes, eventually reaching an equilibrium state. This behavior is consistent with variations in downstream distance at a specific time. The mixing length which is concentration-dependent, first increases the suspension concentration for all grain sizes at smaller downstream distance and then the effect reverses for all grain sizes at larger downstream distance. A similar trend is observed when considering both stratification and mixing length. An error analysis evaluates the model's performance, indicating that the least error corresponds to datasets incorporating all considered effects.

Sediment control in watersheds requires information about soil erosion and sediment yield hotspot areas. Sediment connectivity is an emerging concept contributing to this field and structural sediment connectivity is a concept derived from sediment connectivity. Determining structural sediment connectivity in a watershed can yield a comprehensive image of sediment management possibilities applicable at the watershed scale. However, in most studies, the validity of extracted sediment connectivity maps has not been evaluated holistically. The current study is, therefore, designed to determine a valid structural sediment connectivity map and to use it to validate findings of sediment fingerprinting of the Idelo watershed in Zanjan province, Iran. Digital elevation model (DEM), slope, vegetation cover, and flow accumulative layers have been used in compiling the structural sediment connectivity map. Field observations were made to calculate the field connectivity index. The results showed that the mean structural sediment connectivity index of the target watershed is −6.18. Moreover, areas in the downslope section near the outlet and the narrow strips around the watershed boundaries have moderate to high structural connectivity. The results of field validation showed there is an acceptable agreement between the field connectivity index and the structural connectivity map. Also, these results confirmed previous findings of sediment fingerprinting in the study area. Based on the findings of the current study, determining the structural sediment connectivity index is an efficient method to make management and conservation decisions and control erosion and sediment in the watershed.

Settling basins are one of the structures required for removing excess sediment entering irrigation or power canals diverting water from a river. A numerical model is needed to simulate the flow and sedimentation pattern in settling basins. In the current research, a depth-averaged two-dimensional numerical model of flow and sediment is developed using the finite volume method and based on the time-splitting scheme, which also allows for simulating sediment in a non-equilibrium state. The simulation of flow and sedimentation is done by the numerical model in a decoupled method. Sensitivity analysis was applied to estimate the effects of non-equilibrium parameters and the settling velocity on the numerical results. The results revealed that Maleki and Khan's formula and Zhang and Xie's formula are suitable for estimating the suspended load adaptation coefficient and the sediment settling velocity in the numerical simulations. Investigation of the formulas for the bed adaptation length indicated that all three methods considered in the current research had almost equal accuracy in predicting the sediment concentration distribution in the settling basin. The developed model has been verified against two experimental tests, showing a good fit between observed data and the simulated results.

Severe socio-environmental pressures and land degradation are substantially impacting Ethiopia, eventually leading to low agricultural productivity, with a consequent very high rate of poverty and food insecurity. The current study investigates the future effect of four management practices on reducing sediment yield in the Fincha sub-watershed, Ethiopia, by developing a soil and water assessment tool (SWAT) model over the next three decades (2019–2050). Four best management practices (BMPs) largely applied in the region were considered here. It was found that filter strips can decrease the sediment yield by 65.64 and 58.77, soil or stone bund by 76.37 and 73.07, contour farming by 79.79 and 75.86, and terracing by 84.9% and 76.32% for the years 2019 and 2050, respectively. The impact of these BMPs on various hydrological processes also was evaluated using SWAT. It was found that BMPs are effective in reducing surface runoff and water yield and in increasing groundwater and lateral flows, while they have a reduced effect on evapotranspiration, lateral flow and water yield. The findings presented here point out that all the simulated management practices significantly lower surface runoff and consequently sediment yield across the watershed, but they are not effective enough to reduce soil erosion below a critical threshold that assures crop production. Therefore, to achieve tolerable soil loss, additional soil and land management strategies, such as biological measures and a combination of BMPs are needed and should be considered in future investigations. In summary, the current study offers evidence for managing river basins in semi-arid regions, and can help in ensuring sustainable management of natural resources.

Climate change accelerated by anthropogenic activities has led to the shrinkage and eventually disappearance of salt lakes all over the world. Gradual desiccation of Lake Urmia (LU) in northwestern Iran, as one example of desiccating lakes, has led to the exposure of the lakebed sediment with enormous dust emission potential in some parts. Sand sheets of western LU are identified as one of the major contributors to aerosols in this region. Yet, dust blown from this area is not well characterized. The aims of the current study were, therefore, to comprehensively investigate the origin of dust from sand sheets; the characteristics of dust and temporal variability of the aerosol and to test the effectiveness of the application of sodium alginate (SA) on soil crusting and stabilization. Soil samples were collected from the two prevailing soil types from sand sheets in August 2020. Dust samples were also collected during four time periods: July and August (the beginning of the dry season); October and November (the beginning of the wet season). Using SA with varying concentrations and different methods of application, the effectiveness of the induced crusts was investigated. Authigenic aragonite minerals with elongated needle shapes were found to be the major constituent of the soil and dust samples. Temporal variability of the dust characteristics and their elemental correlation to dust sources revealed that while dust source 1 (DS₁) with higher clay, salt, and silt contents contribute more to the dust composition from July to August (R² > 0.75 for DS₁ versus R² > 0.58 for DS₂), dust source 2 (DS₂) with less salinity and higher sand content becomes the major contributor to dust composition from October to November (R² > 0.91 for DS₂ versus R² > 0.75 for DS₁). Results of stabilizing both DS₁ and DS₂ showed that SA-induced crusts on DS₁ are more stable than DS₂ due to the presence of higher clay, silt, salt, organic matter, and lower aragonite minerals. SA-induced crusts by a compaction method significantly performed better than a spray of SA on either dry (DSp) or soil at its optimum water content (WSp) at all concentrations. Nevertheless, spray methods are more feasible at the field scale and in both DSp and WSp methods, SA_0.5 improved the crust thickness. Scanning electron microscope-energy dispersive X-ray spectroscopy (SEM-EDX) along with thermogravimetric analysis (TGA) confirmed the remaining SA on the soil surface three months after its application indicating the effective performance of the SA solution in sand sheets stabilization. Hence, its application at the field scale could possibly reduce aerosol release and transport to surrounding areas.