Abstract Little is known about compost (C) and zeolite (Z) effects on hydrodynamic properties of near-saturated coarse-textured soils. These effects were tested for a sandy-loam soil by a mini-disk infiltrometer at three pressure heads ( h 0 = -6, -3 and -1 cm) and a wide range of amendment percentages, pa (0-40%). Soil hydraulic conductivity, K -6 , K -3 and K -1 , depending on h 0 , was determined 3.5 and 8.0 months after the treatment with C and 5.0 and 10.5 months after that with Z. With the C, more amendment determined smaller K -6 (by 1.7-3.0 times), stable K -3 and larger K -1 (3.4-4.4 times) values on both sampling dates. With the Z, the most frequent result was that the soil hydrodynamic parameters did not change with pa . Time effects were more appreciable with the C (means for the two sampling dates differing by 2.1-3.8 times, depending on h 0 ) than the Z (means differing by 1.1-1.7 times). The soil treated with Z was more permeable than that treated with C in the first sampling date (percentage differences, Δ, between corresponding means = 38% - 103%, depending on h 0 ) but not in the second date (Δ values varying from -61% to 4%). In the first year after the treatment, near-saturated soil hydrodynamic behaviour can change appreciably following C addition but the same effect is not expected for the Z. Future investigations should include independent determination of soil pore and particle size distributions.
Abstract The suitability of conservation tillage in maize–wheat interrow farming in a young plum orchard in Croatia to control runoff, soil, and element loss under natural rainfall was evaluated. Paired runoff plots (20 m 2 size) comparing conventional (ploughing and discing) and conservation (chisel and harrow) tillage were implemented in triplicate across Stagnosols (11° slope). Soil physical (bulk density, penetration resistance, mean weight diameter, water stable aggregates) and chemical properties (carbon, nitrogen, phosphorous, potassium and copper) were assessed alongside event-based overland flow formation monitoring. After two years, conservation tillage maintained or improved soil structure, with significantly higher aggregate stability and soil carbon at 0–10 cm depth. Moreover, no clear increase in compaction was documented during the shift to conservation tillage. Conservation tillage exhibited a clear and significant mitigation effect on surface flows of water, sediment, and chemical elements. Sediment concentration decreased from 8.95 to 3.11 g L –1 , runoff was 40.5% lower, and cumulative soil loss declined from 8.57 to 2.97 t ha –1 over the two years. Importantly, reduced sediment export translated into markedly lower off-site losses. Conventional tillage increased losses of phosphorus (~3.4×), potassium (~3.2×), copper (~2.6×) and nitrogen (~1.7×) relative to conservation tillage. Overall, non-inversion loosening in orchard inter-rows proved an effective conservation practice for reducing runoff, soil erosion, and chemical export under natural rainfall, supporting on-site soil health and reducing off-site pollution.
Abstract Biological soil crusts (BSCs) play a crucial role in regulating water infiltration into surface substrates; however, their exact hydrological effects remain a subject of ongoing debate. This study quantitatively investigates the kinetics of water immobilization through sorption and the swelling behavior of extracellular polymeric substances (EPS) during the wetting of dry BSCs on recultivated temperate dunes in Brandenburg. Crust samples dominated by the green alga Zygogonium ericetorum were collected from an inland dune in the Lusatian post-mining area. Following a multi-week drying phase, rehydration experiments were conducted using deuterium oxide (D 2 O) to avoid spectral interference with the O–H groups of the EPS. Using diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), the time-dependent shift of the O–D stretching vibrations was analyzed to determine the sorption kinetics of the biological crusts relative to an undisturbed mineral control. In parallel, gravimetric measurements monitored evaporation, while the EPS composition was characterized via ATR-FTIR spectroscopy. Spectroscopic analysis identified alginate as the primary organic component of the crust EPS. While the uncoated mineral control showed almost immediate water infiltration, the BSC samples exhibited a pronounced plateau in OD vibrations during the first three minutes, indicating an initial phase of free water at the surface. Between the 3rd and 12th minutes, a distinct redshift toward lower wavenumbers followed, reflecting the ongoing functional group reorganization, hydration, and EPS swelling, until thermodynamic equilibrium was reached after approximately 12 minutes. Gravimetric data also revealed a significantly higher and faster evaporation rate for the BSCs compared to the control. These results demonstrate that the alginate and EPS matrix of the biological soil crust acts as a water reservoir that hydrologically seals the surface, drastically limiting vertical infiltration into deeper soil layers while retaining water in a highly accessible surface pool. Furthermore, it is conceivable that this delayed water immobilization by the swelling EPS matrix provides a vital ecological benefit by buffering the crust microbiome against severe hypo-osmotic shock during rapid rewetting. However, direct microbial analyses are required to confirm this effect. By moving beyond conventional visual assessments or indirect macro-hydraulic inferences, this approach provides unprecedented molecular-scale insights into the rapid physicochemical transition from free to matrix-bound water during EPS hydration. To our knowledge, this study represents the first application of time-resolved diffuse reflectance infrared spectroscopy (DRIFTS) combined with deuterium oxide (D 2 O) rehydration to directly track water immobilization kinetics in biological soil crusts. By eliminating spectral interference from biopolymer hydroxyl groups, this approach provides unprecedented insights into the rapid physicochemical transition from free to matrix-bound water.
Abstract Microclimatic buffering is a key process that determines the regeneration potential and ecosystem stability in disturbed mountain spruce forests. Retention of standing and downed deadwood alters the balance of radiation, temperature, and humidity near the surface; however, quantitative evidence from exposed slopes in the Carpathians has been scarce. We therefore compared intact forest, deadwood-dominated forest, and open area on steep southeastern slopes of the Western Tatras (Slovakia) using continuous measurements from 2021 to 2025. Micrometeorological stations recorded global solar radiation, air and soil temperature, and humidity at multiple heights and depths; vapour pressure deficit (VPD) was calculated at 5 cm above ground. Differences among sites were assessed using non-parametric tests. Open areas received the highest radiation loads, resulting in extreme warming of the air near the ground (up to 34 °C at 5 cm) and intense soil heating (absolute maximum of 49 °C at – 2 cm). Intact forest reduced incoming radiation and maintained the most stable conditions. Deadwood-dominated stands represented an intermediate type but repeatedly buffered extremes: summer soil maxima remained below 26 °C, and air temperatures near the ground were several degrees cooler than in the open area. In winter, snow cover largely equalised conditions, while during snow-free episodes intact forest showed stronger nocturnal cooling, whereas deadwood stands preserved milder soil minima. VPD patterns followed the same gradient, with the shortest daily duration above the threshold of 1.5 kPa in intact forest, the longest in open area, and intermediate values in deadwood stands. Overall, deadwood-dominated forest approximates, and under certain circumstances even exceeds, the buffering capacity of intact spruce stands. We conclude that retention of deadwood-dominated forests mitigates heat and drought stress, reduces thermal extremes, and provides a low-cost, ecologically grounded adaptation strategy for mountain forest management in the context of climate change.
Abstract No studies have explored how much ageing of rice husk, used as substrate for nanosilica production, alters apparent particle size distribution in this substrate, and therefore modifies nanosilica-soil interactions. To fill this gap, this study has investigated the effects of nanosilica derived from fresh and aged rice husk on soil physical properties and particle detachment ( D c ) in paddy soils through flume experiments on samples collected in Northern Iran. Nanosilica obtained from aged husk showed an increase in mean apparent particle size by 96% compared to the soil amendment derived from fresh residues. Soil treated with fresh husk nanosilica exhibited significantly higher (+106%) water-stable aggregates and lower (–7.4%) bulk density compared to the control, while the differences from aged husk treatments were +86 % and –6.3%, also in this case significant. Flume experiments revealed a significant reduction (–21%) in D c following application of nanosilica from fresh rice husk, while no effect was found for the soil amendment derived from the aged biomass. Compared to the control, D c decreased by 8.1% with aged husk and by approximately 21% with fresh husk. D c can be accurately estimated by hydraulic predictors (shear stress, stream power, and unit stream power) using a shifted power function ( R² = 0.80–0.96). These models show that, across treatments, the effective hydraulic threshold parameter generally increases from control to amended soils, indicating enhanced resistance to detachment initiation.
Abstract Previous studies have shown that silica nanomaterials produced from rice residues, such as husk, can influence several soil properties. However, their effects on soil detachment capacity and structural characteristics in rice paddy fields remain poorly quantified. This study evaluated the effects of nanosilica derived from rice husk on wet aggregate stability, plasticity index, and detachment capacity in paddy soils of Northern Iran under different flow discharges simulated in a hydraulic flume. The nanosilica used in this study was produced by acid extraction followed by controlled heating, and was incorporated into field plots at a 2% amendment level. Results showed that wet aggregate stability and plasticity index significantly increased by 32% and 27%, respectively, in the nanosilica-treated soils compared with the untreated control. Conversely, the average soil detachment capacity decreased by 49%, also in this case significantly. Multivariate analysis indicated strong interrelations among the measured properties and distinctly separated the amended soils from the control group. Linear regressions between detachment capacity and shear stress or stream power showed that nanosilica reduced soil erodibility and increased the threshold resistance to particle detachment under increasing flow power. Overall, the findings demonstrate that rice-husk-derived nanosilica enhances aggregate cohesion and substantially reduces soil vulnerability to concentrated flow erosion in paddy systems.
Abstract High-magnitude floods characterize deserts, commonly explained by the high rain intensities coupled with the low vegetation cover, surface smoothness and the sealing capability of biocrusts. Nevertheless, runoff generation and the subsequent high-magnitude floods stand out when considering the high evaporation, the relatively dry desert surfaces and the high stoniness that characterize many of the surfaces. Also, the rain amount that stems from high intensity (convective) rains is not necessarily higher than in subhumid regions, and indeed, based on a study of runoff dynamics over biocrusted sand dunes in the Negev Desert, runoff was generated already at low to medium intensities of 9-12 mm/h, explained by the high-water absorbance of the extracellular polymeric substances (EPS) that is excreted by the variable microorganisms inhabiting the biocrust. In the Negev, convective intensities were found to primarily result from unstable daily atmospheric conditions following by daytime surface heating. Daytime heating, coupled with cool/cold nighttime temperatures, were also found responsible for the occurrence of temperature-induced vapor flux (TIVF) and the subsequent occurrence of wet-dry cycles that may last for up to 1-2 weeks following a rain event. We hypothesize that the wet cycles which stem from an upward vapor movement from the warm subsurface soil towards the cool soil surface during the night result in biocrust saturation, triggering in turn runoff generation. By wetting the surface (commonly already during the late afternoon), TIVF may trigger runoff in deserts. This is supported hereafter following a thorough four year-long analysis (1990-1994) of rain-runoff relationship that took place on a pair of biocrusted plots covering dunes in the Negev. Albeit the ~20% higher intensities measured during daytime that should have resulted in higher runoff, nighttime runoff amount, runoff flow duration, runoff yield per average rain intensities and runoff yield per the average intensity of each event were 1.8-, 1.5-, 1.5- and 3.1-fold higher during nighttime in comparison to daytime. It is suggested that in addition to the role played by runoff intensity and the surface properties, TIVF provides an additional mechanism that explains the high runoff generation already at low- to medium-intensities, also explaining, at least partially, the relatively high runoff yield and potent floods in the Negev and other arid regions.
Abstract Soil water repellency (SWR) relates to plant species such as conifers and Eucalyptus with high amounts of hydrophobic substances such as resins, waxes, and other oily substances, and are highly vulnerable to wildfires. The heat generated through fire can influence SWR, although the changes can deviate based on soil, climatic, and environmental conditions. This study aims to examine the impact of heating temperature and duration of exposure to heat on the severity and persistence of SWR in eucalyptus and pine forest soils in Sri Lankan highlands. Soils collected from three depths (0–5, 5–10, 10–15 cm) were air dried, passed through a 2 mm sieve, and exposed to six heating temperatures (50, 70, 100, 150, 200, 250°C) and five durations of exposure (20, 40, 60, 90, 120 min). SWR was determined using water drop penetration time (WDPT) and soil-water contact angle. Both eucalyptus and pine soils showed water repellent conditions at the field and at air-dried conditions. Both soils reached completely wettable level (WDPT < 5 s) with very low contact angles when exposed to 200–250°C for 90–120 min, except for the contact angle of the eucalyptus 0–5 cm layer that decreased to a minimum of 40°. SWR showed fluctuations with increasing temperature between 28 and 150°C at all durations of exposure. SWR showed significant positive linear correlation with soil organic matter (SOM) content, of which the strength was moderate (R 2 = 0.64 and 0.50, respectively, for eucalyptus and pine), indicating that the heat-induced change in SWR was not strongly dependent on SOM content. Contrasting transitions in SOM due to removal via various processes and structural and molecular rearrangements might explain fluctuations of SWR at lower temperatures (28–150°C). The findings would be useful for understanding the impacts of various heating dynamics that might occur during forest fires. Further research considering the other important factors, such as molecular-level variations in organic substances as well as mineralogical and climatic aspects, would be important for a better understanding of hydrological responses on burnt forest floors.
Abstract Soil water availability influence plant growth, vegetation, particularly trees, can in turn substantially alter soil properties affecting soil water availability. This study investigates whether tree species with higher transpiration rates promote the development of soils with a higher water-holding capacity using common garden experiment in post-mining heap in northwest Czechia, where several tree species were planted directly into bare overburden. We focused on three monocultures of alder ( Alnus glutinosa ), oak ( Quercus robur ), and spruce ( Picea omorica ). Tree sap flow was measured and used to estimate transpiration at both individual and stand levels. At the same time, soil moisture and water-holding capacity were assessed in each stand. Alder and oak showed similarly high transpiration rates, significantly exceeding those of spruce. The alder stand exhibited the highest average annual soil moisture as well as the highest moisture during the vegetation and dormant season, significantly differing from oak and spruce, while oak soils had a significantly higher moisture than spruce. Water-holding capacity was the highest in oak soils, significantly exceeding that of alder and spruce. These results support the hypothesis that tree species with a higher water demand foster the development of soils with an enhanced water retention capacity.
Abstract Wildland fires affect physical and chemical properties of forest soils, and the magnitude of their effects depends on the soil temperature achieved during a fire. Laboratory heating of soil samples in muffle furnace was used to simulate a natural fire heating of forest soils, although it does not completely reproduce natural fire conditions. The effect of heating temperature of 100–900°C on particle size distribution, soil water repellency (SWR), soil organic carbon content (SOC) and pH was estimated in three soils differing in texture (sandy soil, silty-clay soil, and clay soil) sampled in coniferous and deciduous forests at Gbely (Areni-Gleyic Umbrisol), Hviezdoslavov (Fluvisol) and Gabčíkovo (Fluvisol), respectively. Decrease in the clay content and increase in the sand content was large in silty-clay and clay soils, but not as large in sandy soils. Surprisingly, heating the soil to 100°C, commonly used in soil moisture measurement, caused a decrease in clay content by half (the average value for all soils). This finding should be confirmed by further measurements on the soils from other regions, because the degree of aggregation depends also on the type of clay and other minerals. The persistence of SWR gradually increased in the heating temperature range 100–300°C in all three soils from coniferous forests and sandy soil from deciduous forest, and was absent in the remaining two soils. The SOC decreased and pH increased with increasing heating temperature.
Achieving optimal flow characteristics while handling a complex slurry system in the pipeline needs greater attention. This study aims to demonstrate the role of iron ore concentration and size distribution on slurry rheology and their subsequent effect on slurry pipeline transportation. The concentrated iron ore slurries are sheared in the shear rate range between 0.1 - 500 s-1, where the experimental data is well-represented by the Bingham-plastic model. The model parameters are employed to calculate pressure drop and energy consumption. A thorough investigation through rheomicroscopy analysis reinforces the validity of the rheological hypothesis. The rheological analysis reveals the yieldpseudoplastic flow behaviour of iron ore slurries irrespective of particle concentrations and coarse particle addition. The slurry containing iron ore fines contributes to an increase in viscosity, mitigated by introducing coarse particles. Rheomicroscopy suggests that the viscosity reduction is attributed to the obstruction of floc formation and disintegration of the slurry structure. The pressure drop and energy consumption escalate with increasing slurry velocity regardless of pipe diameters. However, these entities decrease by including coarse iron ore particles in slurries. This work advocates optimizing rheology to reduce pipeline transportation costs while handling bulk iron ore with minimum environmental repercussions.
Catastrophic floods triggered by a dam-break pose significant hazards to infrastructure due to transient flows and concentrated structural loads. These hazards are intensified where in-channel structures or variable topography redirect momentum and magnify impacts on downstream infrastructures. This study aimed to numerically predict the dam-break transient flow characteristics around a bed depression, as a specific topographic condition, in the downstream channel. The numerical model was optimized and validated against experimental results reported in the literature. Subsequently, the effects of bed depression dimensions and location along the channel on transient flow were examined in twelve cases. The validation results demonstrated that the model accurately reproduced the evolution of the free surface, flow velocity, formation of the impact jet, and impact loads. The bed depression has increased plunge-pool dissipation and reduced the peak force to 16.6-18.6 N. Accordingly, the supercritical flow was characterized by a maximum Froude number (Fr) of approximately 5.4 around this depression. Increasing the depression distance attenuated the wave front and decreased the post-depression flow depth from 0.16 m to 0.03 m within approximately 2 seconds. Overall, the framework captured sharp interfaces and transient regime shifts, enabling the prediction of jetting, nappe stabilization and impact-load envelopes. The study has implications for evaluating in-channel structures and the effects of channel topography on rapid flood hazard screening and emergency planning.
This study investigates the role of symmetric wart-type baffles in facilitating fish passage under supercritical flow conditions in an open-channel flume. Experiments were conducted in a 7 m long, 0.5 m wide flume with a 2% bed slope at the Ujigawa Hydraulic Laboratory, Kyoto University. The impact of two baffle spacings (20 cm and 30 cm) on hydraulic characteristics was assessed and compared to a smooth channel. Velocity profiles, flow depth, and turbulence intensity were measured across ten longitudinal points to evaluate flow heterogeneity and energy dissipation. Results indicate that baffles significantly reduce flow velocity and create low-velocity resting zones critical for fish migration. The 20 cm spacing configuration proved most effective, offering a balance of reduced velocities (0.5-0.9 m/s) and sufficient hydraulic diversity to support energy-efficient fish passage. In contrast, the 30 cm spacing resulted in higher velocities and reduced low-velocity zones, potentially challenging weaker swimmers. Turbulence intensity was lowest with 30 cm spacing (TImean= 0.053), indicating smoother flow but fewer refuges compared to 20 cm spacing (TImean= 0.069). The smooth channel exhibited uniform, high velocities, unfavorable for most fish species. These findings highlight the importance of optimized baffle spacing in fishway design to enhance river connectivity and support aquatic biodiversity.
Local scour at bridge piers is a critical phenomenon jeopardizing structural integrity worldwide. This study presents a comprehensive physical modelling investigation into the evolution of local scour in the presence of a protective armor layer, considering both steady and unsteady (hydrograph) flow regimes. A systematic parametric analysis evaluated the effects of pier diameter, flow velocity, and sediment characteristics, the latter comprising three distinct sizes for both the underlying bed material and the armor layer. Experimental observations elucidate the initial scour mechanism: the formation of strong horseshoe vortices that first accumulate armor material upstream of the pier. Subsequent vortex strengthening induces flow instability, leading to the entrainment and downstream transport of bed sediments. Under steady-flow conditions, the maximum equilibrium scour depth shows a strong positive correlation with pier diameter. A 33.3% increase in diameter resulted in a 31.2% increase in scour depth, while a 47.6% increase led to a 46.3% increase. Conversely, the maximum scour depth is inversely proportional to the size of both the armor layer particles and the underlying bed material. For unsteady flows, the peak scour depth was determined to be independent of the sequence of hydrograph events, converging to a value equivalent to the equilibrium scour depth of a steady flow at the hydrograph's peak discharge. However, the temporal evolution of scour depth varied significantly between the flow regimes. A dimensional analysis of the experimental data identified the governing dimensionless parameters. This analysis formed the foundation for deriving new predictive equations to estimate the maximum scour depth at bridge piers protected by an armor layer under both steady and unsteady flow conditions. The proposed relationships provide practical tools for the design and risk assessment of bridge piers.
For the first time a comprehensive analysis for steady and unsteady flow conditions was performed of timedependent scour processes in non-cohesive sediment downstream of a Type A piano key weir. The evolution and progression of scour of large-scale laboratory experiments were interpreted using an empirical approach and adapting a theoretical model based on the phenomenological theory of turbulence developed elsewhere. The results were within 30% of experimental with the R-squared values of 0.972 for the theoretical model and 0.993 for a calibrated empirical model. Results of this study demonstrate consistent scour evolution kinetics between steady and unsteady flow cases, although in the latter, the maximum scour features were smaller than their steady-state counterparts. This study highlights the novelty of integrating experimental and theoretical frameworks to validate and enhance the design of complex hydraulic structures. Quantitative findings confirm the robustness of first principles-based approaches, offering practical insights and design parameters critical for addressing scour challenges in non-cohesive sediment environments.
This paper presents an improved version of the Spalding two-fluid turbulence model developed by Malikov. The model is applied to numerically simulate turbulent flows past one and two square cylinders at a Reynolds number of Re = 47,000. The SIMPLE algorithm with a semi-implicit scheme and second-order accuracy is used to solve the equations. The code developed by the authors was tested on a two-dimensional benchmark problem of flow past a single square cylinder and then applied to crossflow past two square cylinders located side by side. The ratio of the distance between the cylinders, T/d, varied from 0 to 5, which allowed us to identify three characteristic flow regimes: single, slot (interference), and antiphase synchronous. The simulation results were compared with experimental data and showed good agreement in terms of pressure distribution, vortex wake structure, and aerodynamic force coefficients. Comparison with RANS and LES models confirmed that Malikov’s model provides comparable accuracy with significantly lower computational costs.
The study compares changes in annual maximum (AM) discharge occurrence at 33 gauging stations in Slovenia for the period 1961-2023. The entire period was divided into two sub-periods, namely the period 1961-1990 and the period 1991-2023. The frequency of AM occurrence per day of the year was calculated for all stations under consideration, and the kernel density estimate was calculated for the two periods. The findings reveal that, except for one gauging station, the AM discharge has occurred later during the recent three decades (1991-2023) than during the first 30-year period (1961-1990). The shift ranged from one to 35 days. This shift could be mainly attributed to higher air temperatures in the spring and summer months, which intensify precipitation events. At four stations, the day of maximum density shifted from spring to autumn and, at one station, from autumn to spring. All of these stations are located in the eastern part of the country. In contrast, gauging stations in Alpine regions of the western part of the country show smaller shifts, attributed to reduced snow accumulation and earlier snowmelt.
This study introduces a novel machine learning framework to accurately predict the discharge coefficient (Cd) of elliptical side orifices (ESOs). A cleaned experimental dataset consisting of 575 entries, refined using the Interquartile Range (IQR) method to remove outliers was employed. Five key dimensionless input variables were used to predict Cd: relative crest height (W/B), relative orifice width (a/B), relative orifice height (b/B), relative upstream height (y1/B), and upstream Froude number (F1). Four advanced Bayesian-optimized base models: Extreme Gradient Boosting (BO-XGB), LightGBM (BO-LGB), CatBoost (BO-CGB), and Histogram-based Gradient Boosting (BO-HGB) were integrated within a stacked ensemble architecture. A meta-learner based on Multiple Linear Regression (MLR) linearly combined these predictions to form the final Stacked Model (SM-MLR). Among the base models, the BO-CGB model achieved the best validation performance, with R2=0.8884, RMSE=0.0100, and MARE=0.0155. The final SM-MLR model outperformed all base learners and prior models, reaching R2=0.920, RMSE=0.0086, and MARE=0.0122. Model interpretation using Shapley Additive Explanations (SHAP) and Partial Dependence Plots (PDPs) revealed that a/B and b/B were the most influential. PDP analysis highlighted a consistently positive influence of a/B and a nonlinear but stabilizing trend for b/B. In contrast, W/B exhibited a strong negative linear effect on Cd, while y1/B and F1 showed more complex, nonlinear behaviors. These nonlinear and geometry-dependent relationships reinforce the fact that the hydraulic behavior of ESOs is not adequately captured by classical side-orifice theory. Accordingly, this study provides a comprehensive ML-based framework tailored to this geometry, and the analysis offers new theoretical insight into how ESO geometric ratios govern lateral outflow mechanics, addressing a key gap in hydraulic modeling of non-rectangular side orifice. To support practical application, a user-friendly graphical user interface (GUI) was developed, enabling engineers to estimate Cd in real time based on the input parameters. Overall, the proposed stacked ensemble approach significantly advances both the theoretical understanding and predictive accuracy of ESO discharge behavior, offering a robust and practical tool for modern hydraulic design.
Scouring around bridge piers is one of the major reasons for bridge failure. A total of 20 experiments of scour around tandem piers were conducted in an open channel, at a subcritical inflow velocity (U/Uc=0.67) by placing an equal or smaller diameter circular bridge pier downstream of an existing pier with relative diameters in the range 1.00 to 0.67, at varied normalized spacings in the range 4 to 9.33, and detailed measurements of the equilibrium scour beds were taken. Separate scour holes with distinct deposition between the piers was observed in the majority of cases. Highest reinforcement effects were observed for pier combinations with Dd/Du=0.90 and 0.80, resulting in larger scour hole dimensions at the upstream pier, compared to isolated condition. The spacing corresponding to the minimum scour hole dimensions at the downstream pier was observed in the range L/Du=4 to 9.33 for each pier combination and it decreased with the decrease in diameter of the downstream pier. Variations for the normalized equilibrium scour depth, lateral and longitudinal extents of the scour hole, scour surface area, and scour hole volume as a function of normalized spacing for different ratios of downstream and upstream pier diameters, are presented in the form of graphs and equations.
This study evaluated efficiency of bucket lysimeters for measuring water fluxes and ion transport in four hydrologically isolated experimental catchments representing reclaimed (levelled and planted by alder) and unreclaimed (wave like topography, unvegetated) post-mining sites near Sokolov, Czech Republic. Weekly measurements of leachate from lysimeters and surface/subsurface runoff from experimental catchments, in which lysimeters were installed, were collected from 2021 to 2024. Ion concentrations (Ca2+, Na+, Li+, NH4+, K+) were quantified using ion-selective electrodes. Upscaled estimates showed higher accuracy at the unreclaimed site (R2 = 0.81 for total runoff, R2 = 0.88 for evapotranspiration) than at the reclaimed site (R2 = 0.72 and R2 = 0.77). Lysimeter leachate explained surface runoff variance at unreclaimed (R2 = 0.75) and reclaimed (R2 = 0.47) sites, but was not predictive for subsurface flow. Among ions, Li+ showed the highest predictive capacity (R2 = 0.44 - 0.56), while NH4+ showed consistent patterns across sites. K+, Na+, and Ca2+ showed variable transport influenced by soil and vegetation development. Lysimeters captured surface water fluxes and evapotranspiration but did not represent subsurface flow or solute transport well. Better lysimeter performance at the unreclaimed site suggests that vegetation development reduces hydrological predictability during ecosystem recovery.
