rss_2.0Journal of Hydrology and Hydromechanics FeedSciendo RSS Feed for Journal of Hydrology and Hydromechanics of Hydrology and Hydromechanics 's Cover study of flow type dynamics at pedon scale via morphometric parameter analysis of dye-pattern profiles<abstract><title style='display:none'>Abstract</title><p>The application of Brilliant Blue FCF tracer enables to identify flow types in multi-domain porous systems of soils via analyses of morphologic parameters of stained objects occurring in dye pattern profiles, as they represent the footprint of flow processes which occurred in soil during both the infiltration and the redistribution of dye solution. We analysed the vertical dye pattern profiles exposed for different time lengths, and revealed temporal evolution of dye solution redistribution leading to changes in flow types. The field experiment was performed with the Brilliant Blue tracer (the 10 g l<sup>−1</sup> concentration) applied on 1m x 1m surface of the Dystric Cambisol. The top litter horizon had been removed before 100 l of the tracer was applied. Four vertical profiles were excavated on the experimental plot (always 20 cm apart) at different times after the irrigation had been finished: 2 hours (CUT 2), 24 hours (CUT 24), 27 hours (CUT 27) and 504 hours (CUT 504). The analyses of the dyed patterns profiles showed the spatio-temporal changes in the dye coverage, surface area density, average BB concentration, and stained path width, which allowed us to specify three stages of dye solution redistribution history: (i) a stage of preferential macropore flow, (ii) a stage of strong interaction between macropore-domain and soil matrix leading to the generation of heterogeneous matrix flow and fingering flow types, and (iii) a final stage of dye redistribution within the soil body connected with leaching of BB caused by meteoric water. With increasing time, the macropore flow types convert to mostly matrix-dominated FTs in the upper part of the soil profile. These results were supported by soil hydrological modelling, which implied that more than 70% of the soil moisture profiles variability among CUT 2–CUT 504 could be explained by the time factor.</p></abstract>ARTICLE2018-10-29T00:00:00.000+00:0065 Anniversary of the Institute of Hydrology, Slovak Academy of Sciences controlling alterations in the performance of a runoff model in changing climate conditions<abstract><title style='display:none'>Abstract</title><p>In many Austrian catchments in recent decades an increase in the mean annual air temperature and precipitation has been observed, but only a small change in the mean annual runoff. The main objective of this paper is (1) to analyze alterations in the performance of a conceptual hydrological model when applied in changing climate conditions and (2) to assess the factors and model parameters that control these changes. A conceptual rainfall-runoff model (the TUW model) was calibrated and validated in 213 Austrian basins from 1981–2010. The changes in the runoff model’s efficiency have been compared with changes in the mean annual precipitation and air temperature and stratified for basins with dominant snowmelt and soil moisture processes. The results indicate that while the model’s efficiency in the calibration period has not changed over the decades, the values of the model’s parameters and hence the model’s performance (i.e., the volume error and the runoff model’s efficiency) in the validation period have changed. The changes in the model’s performance are greater in basins with a dominant soil moisture regime. For these basins, the average volume error which was not used in calibration has increased from 0% (in the calibration periods 1981–1990 or 2001–2010) to 9% (validation period 2001–2010) or –8% (validation period 1981–1990), respectively. In the snow-dominated basins, the model tends to slightly underestimate runoff volumes during its calibration (average volume error = –4%), but the changes in the validation periods are very small (i.e., the changes in the volume error are typically less than 1–2%). The model calibrated in a colder decade (e.g., 1981–1990) tends to overestimate the runoff in a warmer and wetter decade (e.g., 2001–2010), particularly in flatland basins. The opposite case (i.e., the use of parameters calibrated in a warmer decade for a colder, drier decade) indicates a tendency to underestimate runoff. A multidimensional analysis by regression trees showed that the change in the simulated runoff volume is clearly related to the change in precipitation, but the relationship is not linear in flatland basins. The main controlling factor of changes in simulated runoff volumes is the magnitude of the change in precipitation for both groups of basins. For basins with a dominant snowmelt runoff regime, the controlling factors are also the wetness of the basins and the mean annual precipitation. For basins with a soil moisture regime, landcover (forest) plays an important role.</p></abstract>ARTICLE2018-10-29T00:00:00.000+00:00Response of soil organic carbon and water-stable aggregates to different biochar treatments including nitrogen fertilization<abstract><title style='display:none'>Abstract</title><p>Recent studies show that biochar improves physical properties of soils and contributes to the carbon sequestration. In contrast to most other studies on biochar, the present study comprise a long-term field experiment with a special focus on the simultaneous impact of N-fertilizer to soil structure parameters and content of soil organic carbon (SOC) since SOC has been linked to improved aggregate stability. However, the question remains: how does the content of water-stable aggregates change with the content of organic matter? In this paper we investigate the effects of biochar alone and in a combination with N-fertilizer (i) on the content of water-stable macro- (<italic>WSA<sub>ma</sub></italic>) and micro-aggregates (<italic>WSA<sub>mi</sub></italic>) as well as soil structure parameters; and (ii) on the contents of SOC and labile carbon (C<sub>L</sub>) in water-stable aggregates (WSA).</p><p>A field experiment was conducted with different biochar application rates: B0 control (0 t ha<sup>−1</sup>), B10 (10 t ha<sup>−1</sup>) and B20 (20 t ha<sup>−1</sup>) and 0 (no N), 1<sup>st</sup> and 2<sup>nd</sup> level of nitrogen fertilization. The doses of level 1 were calculated on required average crop production using the balance method. The level 2 included an application of additional 100% of N in 2014 and additional 50% of N in the years 2015–2016 on silty loam Haplic Luvisol at the study site located at Dolná Malanta (Slovakia). The effects were investigated after the growing season of spring barley, maize and spring wheat in 2014, 2015 and 2016, respectively.</p><p>The results indicate that the B10N0 treatment significantly decreased the structure vulnerability by 25% compared to B0N0. Overall, the lower level of N combined with lower doses of biochar and the higher level of N showed positive effects on the average contents of higher classes of <italic>WSA<sub>ma</sub></italic> and other soil structure parameters. The content of SOC in WSA in all size classes and the content of C<sub>L</sub> in <italic>WSA<sub>ma</sub></italic> 3–1 mm significantly increased after applying 20 t ha–1 of biochar compared to B0N0. In the case of the B20N1 treatment, the content of SOC in <italic>WSA<sub>ma</sub></italic> within the size classes &gt;5 mm (8%), 5–3 mm (19%), 3–2 mm (12%), 2–1 mm (16%), 1–0.5 mm (14%), 0.5–0.25 mm (9%) and <italic>WSA<sub>mi</sub></italic> (12%) was higher than in B0N1. We also observed a considerably higher content of SOC in <italic>WSA<sub>ma</sub></italic> 5–0.5 mm and <italic>WSA<sub>mi</sub></italic> with the B10N1 treatment as compared to B0N1. Doses of 20 t biochar ha<sup>−1</sup> combined with second level of N fertilization had significant effect on the increase of <italic>WSA<sub>ma</sub></italic> and <italic>WSA<sub>mi</sub></italic> compared to the B0N2 treatment. A significant increase of CL in WSA was determined for size classes of 2–0.25 mm and <italic>WSA<sub>mi</sub></italic> in the B20N2 treatment. Our findings showed that biochar might have beneficial effects on soil structure parameters, SOC, C<sub>L</sub> in WSA and carbon sequestration, depending on the applied amounts of biochar and nitrogen.</p></abstract>ARTICLE2018-10-29T00:00:00.000+00:00An approximate method for 1-D simulation of pollution transport in streams with dead zones<abstract><title style='display:none'>Abstract</title><p>Analytical solutions describing the 1D substance transport in streams have many limitations and factors, which determine their accuracy. One of the very important factors is the presence of the transient storage (dead zones), that deform the concentration distribution of the transported substance. For better adaptation to such real conditions, a simple 1D approximation method is presented in this paper. The proposed approximate method is based on the asymmetric probability distribution (Gumbel’s distribution) and was verified on three streams in southern Slovakia. Tracer experiments on these streams confirmed the presence of dead zones to various extents, depending mainly on the vegetation extent in each stream. Statistical evaluation confirms that the proposed method approximates the measured concentrations significantly better than methods based upon the Gaussian distribution. The results achieved by this novel method are also comparable with the solution of the 1D advection-diffusion equation (ADE), whereas the proposed method is faster and easier to apply and thus suitable for iterative (inverse) tasks.</p></abstract>ARTICLE2018-10-29T00:00:00.000+00:00Shape of the Nappe During Free Overfall from a Rectangular Channel with Zero Bed Slope<abstract><title style='display:none'>Abstract</title><p>The paper deals with selected procedures used to calculate the shape of compact nappe during free overfall from a smooth horizontal channel with rectangular cross section. Calculated and measured water surface and velocity conditions in the end section, the level of water surface upstream in front of the end section and the shape of the compact part of an overfall nappe are described for a particular compared case.</p></abstract>ARTICLE2013-08-24T00:00:00.000+00:00Integrated Flood Management for Beiyun River, China<abstract><title style='display:none'>Abstract</title><p>Beiyun River Basin is holistically suffering a water shortage and relatively concentrated flood risk. The current operation (level-control) of dams and floodgates, which is in passive defense mode, cannot meet the demands of both flood control and storm water resources. An integrated flood forecasting and management system is developed by the connecting of the hydrological model and hydrodynamic model and coupling of the hydrodynamic model and hydraulic model for dams and floodgates. Based upon the forecasted runoff processes, a discharge-control operation mode of dams and floodgates is proposed to be utilized in order to well regulate the flood routing in channels. The simulated water level, discharge, and water storage volume under different design conditions of rainfall return periods and floodgates operation modes are compared. The results show that: (1) for small floods, current operation modes can satisfy the objectives, but discharge-control operation can do better; (2) for medium size floods, since pre-storing of the floods affects the discharge of follow-up floods by floodgates, the requirement of flood control cannot be satisfied under current operations, but the discharge-control operation can; (3) for large floods, neither operation can meet the requirement because of the limited storage of these dams. Then, the gravel pits, wetlands, ecological lakes and flood detention basins around the river must be used for excess flood waters. Using the flood forecasting and management system can change passive defense to active defense mode, solving the water resources problem of Beijing city and Beiyun River Basin to a certain extent.</p></abstract>ARTICLE2013-08-24T00:00:00.000+00:00Exact Analytical Solutions for Contaminant Transport in Rivers<abstract><title style='display:none'>Abstract</title><p>Contaminant transport processes in streams, rivers, and other surface water bodies can be analyzed or predicted using the advection-dispersion equation and related transport models. In part 1 of this two-part series we presented a large number of one- and multi-dimensional analytical solutions of the standard equilibrium advection-dispersion equation (ADE) with and without terms accounting for zero-order production and first-order decay. The solutions are extended in the current part 2 to advective-dispersive transport with simultaneous first-order mass exchange between the stream or river and zones with dead water (transient storage models), and to problems involving longitudinal advectivedispersive transport with simultaneous diffusion in fluvial sediments or near-stream subsurface regions comprising a hyporheic zone. Part 2 also provides solutions for one-dimensional advective-dispersive transport of contaminants subject to consecutive decay chain reactions.</p></abstract>ARTICLE2013-08-24T00:00:00.000+00:00Temporal and spatial patterns of the river flow and water temperature relations in Poland<abstract><title style='display:none'>Abstract</title><p>Main aim of the study was to determine the temporal and spatial patterns of relations between monthly and annual average river flow (RF) and water temperature (WT) for 53 rivers in Poland. The research made use of monthly and annual WT and RF for 88 water gauges for the period 1971–2015. Correlations were established using the Spearman’s rank correlation coefficient and the similarity of RF–WT relations was determined using the Ward’s hierarchical grouping. It was demonstrated that correlations between average annual RF and WT were negative (for &gt;85% of water gauges) and statistically significant (p&lt;0.05) only for 30% of water gauges. It was confirmed that the studied RF–WT relations underwent seasonal changes. Positive correlations were clearly predominant in the winter months, while from April to September these relations were negative and statistically significant. The RF–WT relations were also characterized by spatial differences and this had been confirmed by separation of seven groups of water gauge profiles distinguished with the help of the Ward’s hierarchical grouping method. The strongest RF–WT relations were apparent in the case of mountainous rivers, for which snow melt supply and summer rainfall supply were predominant, and lakeland rivers, which had a considerable share of groundwater supply. These were classified as cold rivers, as opposed to the cool rivers in the lowland belt, for which the RF–WT relations were the weakest. The results obtained may contribute to the elaboration of an appropriate management strategy for river ecosystems, which are assigned important economic and environmental functions.</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:00Effect of slope position on soil properties and soil moisture regime of Stagnosol in the vineyard<abstract><title style='display:none'>Abstract</title><p>Hillslope hydrology in agricultural landscapes is complex due to a variety of hydropedological processes and field management possibilities. The aim was to test if there are any differences in soil properties and water regime along the hillslope and to compare vineyard rows (vine) with inter-rows (grass) area for those properties. The study determined that there are significant differences in the contents of soil particle fractions, pH, and humus content along the slope (<italic>P</italic> &lt; 0.0001), with lower confidence level in bulk density <italic>(P</italic> &lt; 0.05). Differences between row and inter-row space were significant for the pH, humus, and silt content, but for sand and clay content, and bulk density differences were not determined. The study determined differences in soil water content among five slope positions (<italic>P</italic> &lt; 0.0001), and between row and inter-row vineyard space (all with <italic>P</italic> &lt; 0.05). Where in the upper slope positions (e. g., P1) soil water content was higher than on lower slope positions. Higher soil water content was observed at higher slope positions, associated with clay content. However, it can be concluded that the retention of moisture on the slope is more influenced by local-scale soil properties (primarily soil texture) and variability of the crop (row/inter-row) than the position on the slope.</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:00Short-term effects of compost amendments to soil on soil structure, hydraulic properties, and water regime<abstract><title style='display:none'>Abstract</title><p>Despite the increasing interest in applying composts as soil amendments worldwide, there is a lack of knowledge on short-term effects of compost amendments on soil structural and hydraulic properties. Our goal was to study the effect of compost and vermicompost-based soil amendments on soil structure, soil water retention characteristics, aggregate stability and plant water use efficiency compared to that of mineral fertilizers and food-waste digestate and examine if these effects are evident within a short time after application. We set up a pot experiment with spring wheat using a sandy and a loamy soil receiving either mineral fertilizer (MF); dewatered digestate from anaerobic digestion of food waste (DG), vermicomposted digestate (VC_DG); sewage sludge-based compost (C_SS) and sewage sludge-based vermicompost (VC_SS). We then monitored and calculated the soil water balance components (irrigation, outflow, evaporation, transpiration, and soil water content). At harvest, we measured shoot biomass, soil texture, bulk density, water retention characteristics and aggregate stability. The irrigation use efficiency (IE) and the plant water use efficiency (WUE) were calculated for each treatment by dividing the transpiration and the dry shoot biomass with the amount of water used for irrigation, respectively. For the sandy soil, we used X-Ray computed tomography to visualise the pore system after applying organic amendments and to derive metrics of the pore-network such as its fractal dimension, imaged macroporosity and critical pore diameter. X-Ray tomography indicated that composting and vermicomposting resulted in more complex and diverse porous system and increased soil macroporosity. The increased fractal dimensions also indicated that compost and vermicompost can contribute to structure formation and stabilization within a short time after their application. Despite the small application rate and short incubation time, the application of organic amendments to the two different soil types resulted in improved soil water holding capacity and water use efficiency. Composting and vermicomposting appeared to have the best effect at reducing the irrigation demand and evaporation losses and increasing the water use efficiency of the plant, likely through their effect on soil structure and the pore-size distribution.</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:00Effects of bed-material gradation on clear water scour at single and group of piles<abstract><title style='display:none'>Abstract</title><p>This study presents the results of 32 laboratory experiments on local scour at a single pile and a 1 × 4 pile group for both uniform and non-uniform sediments under clear water conditions. The present study aims to evaluate the effects of different sediment beds made up of mixtures of sand and gravel (four-bed configurations) in <italic>d</italic><sub>50</sub> (1–3.5 mm) and gradation (1.4–3) ranges on scour depth for different flow discharges and flow depths. Further, the findings of the experiments are deployed to describe the effects of pile spacing and flow conditions on the local pier scour for both uniform and non-uniform bed granulometries. In addition, this study addresses the performance of some existing scour-depth predictors. Also, the corresponding results are suitable for validating the numerical models in local pier scour prediction importantly with non-uniform sediments. In summary, the results show that effects of sediment gradation dampen with increasing flow shallowness. Furthermore, the maximum scour depth at pile groups generally increases as pile spacing decreases for uniform sediments, whereas the mentioned trend was not observed for non-uniform sediments for the same flow and sediment conditions. Moreover, the experimental results revealed that bed sediment gradation is a controlling factor in the pile’s scour. Thus, the existing scour depth predictions could be highly improved by considering sediment gradation in the predictions. Finally, the conclusions drawn from this study provide crucial evidence for the protection of bridge foundations not only at the front pile but also at rear piles.</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:00Warming Vistula River – the effects of climate and local conditions on water temperature in one of the largest rivers in Europe<abstract><title style='display:none'>Abstract</title><p>The paper evaluates changes in the water temperature of the Vistula River – one of the longest rivers in Europe. Mean monthly and annual water temperatures from the period 1971–2017 for 11 stations along the entire length of the river revealed the increasing trends. The mean increase in water temperature in the analysed multi-annual period was 0.31 °C dec<sup>–1</sup>. In the majority of analysed stations, the key factor determining changes in the water temperature of the river was air temperature. The observed water warming in the Vistula River should be considered an exceptionally unfavourable situation in the context of importance of water temperature for a number of processes and phenomena occurring in river ecosystems. Given the scale of changes, fast measures should be undertaken to slow down the warming.</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:00Evolution of local scour downstream of Type A PK weir in non-cohesive sediments<abstract><title style='display:none'>Abstract</title><p>A large-scale piano key weir laboratory study was conducted to investigate the evolution of the scour process occurring in the downstream basin for two non-cohesive granular bed materials, including the analysis of scour-hole geometry and patterns at equilibrium. It was observed that hydraulic conditions, particularly tailwater level, significantly affect the scour mechanisms and equilibrium morphology, eventually resulting in scour depths that exceeded the weir height. Unprecedented insights on the scour dynamics are also provided, along with tools to estimate the time evolution and maximum scour depth, its location in the streamwise direction, and the maximum scour length.</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:00Performance of experimental bioretention cells during the first year of operation<abstract><title style='display:none'>Abstract</title><p>Detailed data on the long-term performance of bioretention cells (BC) for stormwater management are sparse. This research aimed at setting up and testing an infrastructure that will provide the data on hydrologic and chemical performance of BC. Two identical experimental BC’s were built. The monitoring methodology monitoring was developed and tested during a first growing season with the first BC supplied with natural rainfall, while the second BC was used for ponding experiments. Key layer of the BCs, a biofilter, was composed of sand, compost and topsoil. Both BCs are equipped with sensors monitoring the components of water balance and the water potential of the biofilter. High levels of total suspended solids were detected in the outflow. The runoff coefficient for the entire period of the growing season was 0.72 in the first BC and 0.86 in the second BC, while the peak outflow reduction for individual rainfall episodes ranged between 75% to 95% for the first BC and 19% to 30% for the second BC. Saturated hydraulic conductivity of the biofilter in the first BC decreased by two orders of magnitudes after the first year of operation. Retention curves of the biofilter changed due to material consolidation.</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:00Spatial particle size distribution at intact sample surfaces of a Dystric Cambisol under forest use<abstract><title style='display:none'>Abstract</title><p>The idea of the present study is to describe the spatially varying particle size distribution (PSD) along intact aggregate surfaces with the laser diffraction method (LDM) of four silty-loamy and OC enriched horizons of a Dystric Cambisol from the Uhlířská catchment (Czech Republic) with the laser diffraction method (LDM). Besides, the comparability of the LDM with the sieve and pipette method (SPM), the reproducibility, and the effect of pretreatment on the particle size distribution derived by LDM were analysed.</p><p>The laser diffraction method enables rapid and continuous particle size distribution measurements with required sample amounts of 0.1–0.2 g for each measurement compared to 5–20 g for SPM. The LDM-derived PSD’s can be directly compared with the standardised SPM-derived PSD’s by using regression analysis with coefficients of determination (r<sup>2</sup>) between 0.83 and 0.93. Sample pretreatment following standardised proceedings indicates a better comparability between the particle size distributions of both methods. Besides, the highest coefficients of variation of up to 78.6 and therefore the lowest reproducibility were found for the unpretreated PSD of the AE and Bs horizon. Thus, limited evaluability and reproducibility of soil material enriched in organic carbon (OC), used in the current study, needs further analysis.</p><p>For spatial analysis of PSD’s along intact surfaces of soil aggregates and profiles, spatial data interpolation by inverse distance weighting (IDW), kriging, and triangulated irregular networks (TIN) can be used for detailed measuring, mapping, and spatial extension of the sand, silt, and clay fractions at unsampled locations using a set of samples of known locations. The information offers the possibility of comparing and verifying data obtained by non-invasive mid-infrared spectroscopy and Vis–NIR spectroscopy by spatial extension for given soil aggregates and profiles.</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:003D numerical modeling of flow characteristics in an open channel having in-line circular vegetation patches with varying density under submerged and emergent flow conditions<abstract><title style='display:none'>Abstract</title><p>In the marine ecological system, the prime role of water management and durability of an ecosystem is being played by the vegetation patches. The vegetation patches in open channels can significantly affect the flow velocity, discharge capacity and hinder energy fluxes, which ultimately helps in controlling catastrophic floods. In this study, the numerical simulation for turbulent flow properties, i.e. velocity distribution, Reynolds stresses and Turbulent Intensities (TI) near the circular vegetation patches with progressively increasing density, were performed using the computational fluid dynamics (CFD) code ANSYS FLUENT. For examination of the turbulent flow features in the presence of circular patches with variable densities, Reynolds averaged Navier-Stokes equations, and Reynolds stress model (RSM) were employed. The numerical investigation was performed in the presence of in-line emergent and submerged patches having variable vegetation density in the downstream direction. Two of the cases were investigated with three circular patches having a clear gap to patch diameter ratio of <italic>La</italic>/<italic>D</italic> = 1 (where <italic>La</italic> is the clear spacing between the vegetation patches and <italic>D</italic> is the diameter of the circular patch), and the other two cases were analyzed with two patches having a clear gap ratio of <italic>La</italic>/<italic>D</italic> = 3. The case with a clear gap ratio (<italic>La</italic>/<italic>D</italic> = 3) showed 10.6% and 153% inflation in the magnitude of longitudinal velocity at the downstream of the sparse patch (<italic>aD</italic> = 0.8) and upstream of the dense patch (<italic>aD</italic> = 3.54), respectively (where <italic>aD</italic> is the flow blockage, in which “<italic>a</italic>” represents the patch frontal area and “<italic>D</italic>” represents the patch diameter). The velocity was reduced to 94% for emergent and 99% for submerged vegetation due to successive increase in vegetation density made by introducing a middle patch which reduced the clear gap ratio (<italic>La</italic>/<italic>D</italic> = 1). For <italic>La</italic>/<italic>D</italic> = 1, the longitudinal velocities at depth <italic>z</italic> = 15cm were increased by 319% than at depth <italic>z</italic> = 6cm at the downstream of the dense patch (<italic>aD</italic> = 3.54). Whereas it was observed to 365% higher in the case of <italic>La</italic>/<italic>D</italic> = 3. The magnitude of turbulent characteristics was observed 36% higher for submerged vegetation cases having a clear gap ratio of <italic>La</italic>/<italic>D</italic> = 1. The successive increase in the patch density reduced the Reynolds stresses, turbulent kinetic energy and turbulent intensities significantly within the gap region. The major reduction in the flow velocities and turbulent properties in the gaps provides a stable environment for aquatic ecosystems nourishment and fosters sediment deposition, and supports further vegetation growth.</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:00Incipient motion of sediment particles in the presence of bed forms under decelerating and accelerating flows<abstract><title style='display:none'>Abstract</title><p>This paper investigates the incipient motion of sediment particles under non-uniform flow in river and laboratory. In rivers, the non-uniform flow is often observed due to the presence of various bed forms. Threshold condition has been examined by using the Shields diagram based on the uniform flow assumption, however, this approach can be led to fallacious results for non-uniform flows where the effect of pressure gradient is significant due to bed forms. This study investigates the chronological order of incipient motion of the particles, the average threshold velocity (<italic>U<sub>cr</sub></italic>), and Shields parameter for non-uniform flows. River data collection with gravel is used for investigating the incipient motion of surface layer of river bed and the laboratory data collection is considered studying the incipient motion of sub-surface layer of river. Both river and laboratory data collections are conducted in the presence of bed forms. Results reveal that the Shields diagram underestimates the particle incipient motion under accelerating and decelerating flows for the both case of laboratory and river. In both weak and general motion in the laboratory, the values of the critical Shields parameter are located below the Shields diagram, showing no particle motion. Our analysis shows that the incipient motion in river is affected by the presence of bed forms, river width changes, and flow non-uniformity conditions. The results show that in the accelerating flow (the bed form exit with a negative slope), the incipient motion is greater than the decelerating flow (the bed form entrance with a positive slope).</p></abstract>ARTICLE2022-02-12T00:00:00.000+00:00Bedload Equation Analysis Using Bed Load-Material Grain Size<abstract><title style='display:none'>Abstract</title><p>Twelve predictive bedload sediment transport equations are rated against 14 sets of gravel-bed river field data collected by handheld bedload sampler in Narmab River, northeastern Iran. To evaluate these formulas two types of grain size namely bedload and bed material were used. The results show that the equations of Engelund and Hansen, Van Rijn and Einstein perform well with bed material grain size, while Shocklitsch, Meyer-Peter and Mueller, and Frijlink yield the best results using the bedload grain size.</p></abstract>ARTICLE2013-08-24T00:00:00.000+00:00Comparison of an Automated and Manual Method for Calculating Storm Runoff Response in Ungauged Catchments in Serbia<abstract><title style='display:none'>Abstract</title><p>Estimation of discharge from ungauged catchments based on rainfall-runoff analysis is a very frequent task in engineering hydrology. Very often, design discharges are needed for streams or small rivers where no streamflow data is available (river training works, culverts, small hydropower plants, etc). This study uses a well established lumped hydrologic rainfall-runoff model to compare two different approaches in data preparation. The traditional method of manual obtainment of catchment parameters was compared to a more contemporary methodology using automation with geographic information systems, digital terrain models and available datasets, with an emphasis on open-source tools and freely available datasets. Both techniques were implemented on more than 100 catchments in Serbia to calculate storm runoff response. The results show minor differences that are insignificant compared to the time and resources saved with the automated techniques. The use of such automated methods enables the hydrologist to direct more attention to other factors that influence discharge even more than catchment parameters, such as rainfall, soil and land use data.</p></abstract>ARTICLE2013-08-24T00:00:00.000+00:00en-us-1