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Evaluation of hydraulic parameters in an open channel plays a pivotal role in the design and estimation of different hydraulic characteristics; therefore, an experimental-based research study was conducted on different canals tertiary in the command of three distributaries falling in the hydraulic boundaries of the Jamrao canal. Keeping in the view objectives of the study, the recorded data of hydraulic characteristics (discharge, wetted perimeter, roughness coefficient, and bed slope) were determined and correlated using simple linear regression analysis for earthen watercourses to develop the empirical equations for important hydraulic characteristics. An empirical equation for the roughness coefficient has developed which is simple and explicit for computing the value of the roughness coefficient as compared to Universal Manning's formula. The comparison of observed values of important hydraulic characteristics and roughness coefficient computed from empirical equations for the watercourse has yielded satisfactory results. The mean absolute error of important hydraulic parameters viz. discharge, wetted perimeter, roughness coefficient, and bed slope is in the order of ±10.23%, ±4.25%, ±9.9%, and ±3.2% respectively. The value of the coefficient of determination (R2) for the set of these equations is within the range of 78 to 96% which is the indicator of an excellent correlation within the variables. The general empirical equations developed from this study can fairly be used in determining the flow variables particularly discharge in the tertiary canals without using a cumbersome method that is a cut-throat flume and associated monographs. [ABSTRACT FROM AUTHOR]

Purpose: to determine the roughness coefficient of a protective coating consisting of Enkamat 7225 geomat filled with small crushed stone from 6 to 10 mm and soil seeded with perennial ryegrass. Materials and methods. The hydraulic studies conducted by the authors were aimed at determining the roughness coefficient of the studied coating made of composite material (geomat). This study was carried out on an experimental setup of trapezoidal cross-section with vertical right (m = 0) and inclined left (m = 1) slopes. The total length of the section with the coating was 8.6 m. The slope of the flume bottom was i = 0.010...0.03. Results. The article presents the results of experimental studies devoted to determining the roughness coefficient of a composite coating made of geomat filled with crushed stone and reinforced with ryegrass. The average value of the roughness coefficient is derived and the analysis of the obtained results is performed. Based on the analysis conducted and after calculating the roughness coefficients by three formulas: Manning, Gangulyer-Kutter and N. N. Pavlovsky, it is possible to recommend for the studied coating the value of the roughness coefficient n = 0.0301, calculated using the Manning formula. Conclusions. The conducted studies, which are devoted to the roughness coefficient assessment for the investigated anti-erosion protective coating, have shown the possibilities of using such lining in practice. The use of this coating gives a natural look without losing the protective properties to the soil structure slope, the watercourse bed and banks.

The Al-Musayyab Canal, a vital irrigation infrastructure in the Babil Governorate of Iraq, serves numerous cultivated areas. However, it has faced frequent flooding in recent years due to increased flow rates and changes in land use. This study aims to define the hydraulic characteristics of the 49.5 km-long Al-Musayyab Canal, which extends from the head regulator at Al-Musayyab City to Jabla City and includes 13 branches that distribute water to agricultural areas. To simulate both steady and unsteady flow conditions, HEC-RAS version 6.3 software was used, incorporating 175 cross-sections distributed along the canal. Calibration and verification with flow rates ranging from 25 to 45 m³/s revealed that the optimal Manning roughness coefficient is 0.025, which minimizes the error ratio between observed and calculated water surface elevations for both steady and unsteady states. Various scenarios with gate openings ranging from quarter to fully open were simulated. The results indicated that, for the steady flow model, the water surface elevation ranged from 26.32 to 31.78 meters, and velocities ranged from 0.2 to 0.98 meters per second. For the unsteady flow condition, these values ranged from 26.58 to 33.12 meters and 0.22 to 0.89 meters per second, respectively. Risk areas were identified between stations 6750 and 24750 km, which require either cross-section training or embankment heightening to enhance the canal's discharge capacity and mitigate flooding during high flow rates. [ABSTRACT FROM AUTHOR]

Method of numerical analysis of the influence of initial depression depth coupled with absolute surface roughness and with Manning's roughness coefficient onto the key hydraulic parameters of the stormwater runoff is proposed. Small highly urbanized catchment with 100% impervious cover was used in stormwater management model numerical simulations for climatic conditions of the Lviv City (Ukraine) at the return period of 1 year. An increase in depression depth from 1 to 5 mm causes reduction in the specific maximum peak runoff from 5.13∙10−3 L/(s∙m2) to 3.29∙10−3 L/(s∙m2), while the critical duration of rainfall increase from 17 min to 56 min. The dimensionless maximum peak flow rate is expressed as a two-parameter exponent function of the initial depression depth, allowing the estimation of the lower limit of this discharge for the practically significant range of the depression depth. [ABSTRACT FROM AUTHOR]

This study compares samples of erosion resistant coatings made of geomat filled with crushed stone with bituminous and bitumen-polymer binders. The comparison was made several years after the production of the coatings under study. The article provides conclusions about the coating durability and the specific features of its application, as well as recommendations for using roughness coefficient. [ABSTRACT FROM AUTHOR]

Copyright of Przegląd Elektrotechniczny is the property of Przeglad Elektrotechniczny and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Calibrating hydraulic models for water distribution systems (WDS) is crucial during model-building, particularly in determining the roughness coefficients of pipes. However, using a single roughness coefficient based solely on pipe material can lead to significant variations in frictional head losses. To address this issue and enhance computational efficiency, a genetic algorithm (GA) for optimizing roughness coefficients is presented With the Environmental Protection Agency Network Evaluation Tool (EPANET) hydraulic model. EPANET-GA further considers the spatial characteristics of pipes. We incorporated an automated calibration process and a user graphic interface to analyze the water head pressures of WDS nodes for the Zhonghe-Yonghe Division. The results reveal that the optimized roughness coefficient produces a high correlation coefficient (0.90) with the measured data in a time slot. In addition, a low standard error (8.93%) was achieved for 24-hour predictions. Furthermore, in the Shelin-Beitou Division, spatial characteristics were incorporated as constraints during the calibration process. The EPANET-GA has the potential to serve as an excellent tool for designing, operating, and optimizing water supply networks. It can become an advanced operational solution for administrations, aiding in tasks such as leakage detection and pump energy optimization. [ABSTRACT FROM AUTHOR]

ABSTRACTUnderstanding flow and velocity distributions in open channels is important for designing various hydraulic structures. This study focuses on modeling the flow and velocity distributions along with different open channel roughness (steel and concrete) and slopes from 0.0–4.7%, using an ultrasonic flowmeter and 3D scanner. Comprehensive Kriging and Linear Regression Models were developed to simulate flow behavior, considering the effects of surface roughness and channel slope. The models utilized appropriate boundary conditions by varying the roughness values. The concrete channel had an average centreline flow and velocity of 0.21 m3/s and 0.64 m/s, respectively, while the average flow and velocity for the steel channel was 0.33 m3/s and 0.97 m/s, respectively. The model’s accuracy and reliability were assessed by Pearson correlation and standard error of the estimate (SEE). According to the Pearson correlation, there is a significant relationship between the slope and flow on steel and concrete, with an average r equal to 0.75. The standard error of the estimates between observed and measured velocity and flow were 0.164 and 0.001, respectively.

Efforts for getting the maximum efficiency from the existing water resources and to implement new projects are getting more attention these days. Determining the flow resistance for the project design and control process in open channels requires sophisticated applications. It is usually essential to be aware of the characteristics of the channel and flow to determine the hydraulic roughness, which represents the resistance of the flow. Hence, empirical calculation and evaluation of the hydraulic roughness will support future design and planning processes. In this study, four different particle sizes (d50= 28mm, 17.5mm, 4mm, and 1.75mm) that were fixed on blocks were used. These particle sizes were then used as the bed covering together with, three different horizontal bed slopes, and flow rates in the experiments to determine the associated Manning roughness, n. During the experiment, Froude number values were examined and it was determined that, in 32 experiments the flow regime can be considered as subcritical. Alternatively, the Lotter method was used to confirm the roughness values obtained by the Manning equation. It was concluded that the roughness values obtained by the selected methods have good concordance with each other.

Accurate prediction of the roughness coefficient of sediment-containing drainage pipes can help engineers optimize urban drainage systems. In this paper, the variation of the roughness coefficient of circular drainage pipes containing different thicknesses of sediments under different flows and slopes was studied by experimental measurements. Back Propagation Neural Network (BPNN) and Genetic Algorithm-Back Propagation Neural Network (GA-BPNN) were used to predict the roughness coefficient. To explore the potential of artificial neural networks to predict the roughness coefficient, a formula based on drag segmentation was established to calculate the roughness coefficient. The results show that the variation trend of the roughness coefficient with flow, hydraulic radius, and Reynolds number is consistent. With the increase of the three parameters, the roughness coefficient decreases overall. Compared to the traditional empirical formula, the BPNN model and the GA-BPNN model increased the determination factors in the testing stage by 3.47 and 3.99%, respectively, and reduced the mean absolute errors by 41.18 and 47.06%, respectively. The study provides an intelligent method for accurate prediction of sediment-containing drainage pipes roughness coefficient. HIGHLIGHTS The relationship between the roughness coefficient and related hydraulic factors is analyzed.; Two intelligent methods (BPNN and GA-BPNN) are used to predict the roughness coefficient.; Based on the concept of drag segmentation, the roughness coefficient calculation formula is established.;

Context: The natural spatial and temporal variability (uncertainty) of the inputs involved in hydrodynamic modeling for hazard assessment and delineation of potentially flood-prone areas is propagated in the output variables of the models. In normal practice, only natural temporal variability in terms of return period is usually considered, but the propagation of spatial uncertainty is unknown. Methodoly: This paper presents the analysis of uncertainty propagation using the first order second moment method of Manning’s roughness coefficient in the depth, velocity and flow intensity output variables of the numerical shallow water model implemented in HEC RAS 2D. A simulated flash flood in the municipality of Mocoa (Putumayo) and the corresponding probability of reaching a damage level for different return periods were analyzed, regarding the events occurred in March 2017. Results: A procedure applicable to flood hazard assessment is obtained where the temporal natural variability associated to hydrographs with different return periods and the spatial natural variability associated to the Manning’s roughness coefficient are integrated. Conclusions: The propagation of uncertainty was able to establish a direct relationship between the increase of flow (return periods) and the increase of uncertainty in the evaluation of the flood hazard indicator.

The current research is focused on investigating the influence of bearing irregularities like eccentricities (e), non-circularities (G), L/D ratio (ß), surface roughness coefficient (Y) on hydrodynamic performance of journal bearing such as load bearing capacity, friction force, lubricating oil flow. The performance is evaluated through finite difference method technique implementing a Newton-Raphson method of error convergence. The simulation outputs were than designed using an optimization tool entitled as Design of Experiment (DoE) on basis of response surface methodology (RSM). The outputs of RSM models were meant to forecast the response parameters like, load bearing capacity, friction force, flow of lubricant and further required to identify the noticeable interdependencies within the input parameters while evaluating the lubrication performance. The optimization of the bearing irregularities is done considering desirability approach of the response surface methodology in identifying proper combination of parameters.

The helical flow leads to the redistribution of the bed shear stress and roughness coefficient in open-channel bends, influencing the transport of sediment and riverbed evolution process. To explore the mechanisms underlying this redistribution, a 3D numerical simulation of a 180° sharp bend was performed by solving the Reynolds-averaged Navier–Stokes (RANS) equations using the Reynolds stress equation model (RSM) as the anisotropic turbulence closure approach. The results indicate that the high bed shear stress zone appeared in the inner bank region from the 50° to 110° sections, and the section maximum bed shear stress gradually shifted outwards, owing to the advective momentum transport by the circulation cells. The quantitative analyses of the terms in depthaveraged Navier-Stokes equations indicate that the contributions of the crossstream circulation and cross-flow to the downstream bed shear stress were of the same order of magnitude, and the overall contribution rate of the cross-stream circulation was 20%. The contribution rates of the cross-flow, cross-stream circulation, turbulence, and pressure gradient to the transverse bed shear stress were approximately 30%, 7%, 3%, and 60%, respectively, indicating that the pressure gradient term arising from the transverse water surface slope played a dominant role. The Chezy resistance coefficient showed an overall decreasing trend along the bend. Therefore, an effective expression considering the streamwise variation along the centreline and transverse variation was successfully established to predict the uneven distribution of the Chezy resistance coefficient. [ABSTRACT FROM AUTHOR]

The roughness coefficient is a comprehensive parameter reflecting river resistance, which is widely used in the planning and design of river regulation and flood control projects. In recent years, as the upstream water conservancy and hydro-power projects have been put into operation, the frequency of low flow in the middle and lower reaches has increased, and the frequency of flood flow has decreased. All kinds of vegetation in the river floodplain grow luxuriantly, which causes a change in the river resistance and roughness coefficient. The present study was carried out with theoretical analysis and laboratory tests. A formula for the roughness coefficient calculation was derived based on the momentum equilibrium equation and momentum exchange between the vegetation layer and upper layer. The relationship between the depth-averaged velocity within the vegetation layer and depth-averaged velocity of the whole flow was analyzed. The reliability of the formula was verified by a large amount of previous experimental data. Based on the derived formula, the variation law of the roughness coefficient with vegetation density, vegetation height, and water depth were obtained. For the emerged vegetation flow, the Manning coefficient tended to increase with the increase in the vegetation density and water depth. For the submerged vegetation flow, the Manning coefficient showed a trend of decreasing with the increase in the water depth and increased with the increase in the vegetation height. Finally, the derived formula was applied in the Yueyang reach of the Yangtze River and the Duliujian River. The study can be applied in the fields of water level-flow discharge relationship analysis and the water surface line calculation of vegetated rivers. [ABSTRACT FROM AUTHOR]

Copyright of Tecnura is the property of Tecnura and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Nature-like fish passes are commonly designed as a preferred way to overcome barriers in rivers. However, meeting the recommended hydraulic parameters for these passes can be challenging. As a result, boulders or sills are often incorporated to supplement their structure. From a hydraulic standpoint, the crucial parameters under investigation are the depths and velocities (or the corresponding velocity field). In this study, a comprehensive analysis was conducted on a full-width rock-ramp fish pass constructed in a river, specifically targeting the barbel zone. The achieved parameters were assessed through direct field measurements, complemented by mathematical modeling using 1D and 2D HEC-RAS models (version 6.3.1). For the assessment of model accuracy, the error indices root mean square error (RMSE) and mean absolute error (MAE) were used. Based on their evaluation, the 1D model provides more precise results in the assessed profiles (the RMSE for depths (m) was 0.0663 (for velocities (m∙s−1) 0.293) compared to the 2D model, where the RMSE for depths (m) was 0.070 (for velocities (m∙s−1) 0.398), the MAE for the 1D model for depths (m) was 0.0350 (for velocities (m∙s−1) 0.185) compared to the 2D model, where the MAE for depths (m) was 0.0375 (for velocities (m∙s−1) 0.274)). The findings highlight the differences in the problem-solving approaches between the models as well as the potential for simplifications in practical applications. [ABSTRACT FROM AUTHOR]

The aim of the study was to assess the possibility of using the empirical formulas to determine the roughness coefficient in gravel-bed streams, the bed slopes of which range from 0.006 to 0.047. Another aim was to determine the impact of taking into account the conditions of non-uniform flow on the application of these formulas and to develop the correlation relationships between the roughness coefficient and water surface slope and also between the roughness coefficient and friction slope in order to estimate the roughness coefficient n in gravel-bed streams.

IntroductionThe world population has grown rapidly over the last 150 years and continues to do so, resulting in impacts on hydrologic resources at both a local and global scale (Yang et al., 2012). The competition for water between humans and ecosystems leads to complex interactions between hydrologic and social systems (liu et al., 2015). From the beginning of human history, it is located in floodplains. Floods can have large societal impacts, such as severe damage to urban areas, which are expected to grow around the world (Alfieriet al., 2018). In traditional hydrology, humans are either conceptualized as an external force to the system under study or taken into account as boundary conditions (Peel and Blöschl, 2011). Sivapalan et al. (2012) proposed a new model for investigating the interactions of the hydrological system and the social system. It explores the procedure coupled human-water system evolves and possible trajectories of its co-evolution, including the possibility of generating emergent, even unexpected, behaviors. Socio-hydrology must strive to be a quantitative science. There are several methods to control and mitigate flood risk, one of these methods is flood zoning (Jha et al., 2012). In last two decates, The Kalat city is flooded almost every year and many houses and historical sites in the city are damaged. Therefore, the main purpose of thisWe paper is to show investigated how changing human behavior with nature can affect the behavior of the natural system.Method and MaterialsKalat city located in 59° 43' 23" to 59° 47' 41" northern latitude and 36° 59' 35" to 37° 00' 05" eastern longitude. The city is divided into 11 sub-basins. The city has experienced fast and inappropriate urbanization over the past few years. To collect our data, the annual reports of the Regional Water Organization and the Environment Organization of Khorasan Province were used.SCS method was used to estimate the runoff peak discharge. Precipitation has been estimated for seven return periods: 2, 5, 10, 25, 50, 100, and 200 years. In this study, to analyze the sensitivity of runoff, we considered precipitation and curves number from 20% less to 20% more than the actual values in the study basin (at intervals of 5 %). We used the Cowan method to determine the roughness coefficient in this study. HEC-RAS model has been used for flood zoning. To determine the impact of various factors on the intensification of floods in Kalat city, we obtained questionnaires from relevant authorities. Likert scale was used to measure the results of the questionnaires. We prepared two questionnaires; first one is related to the inner city zone and includes the factors that intensify the occurrence of floods inside the city of Kalat, and it was classified into the following parts: 1) Local community 2) Managerial 3) Physical; and the second one includes the factors that intensify the flood in the upper part of Kalat city. We classified these factors into three parts: 1) Non-local community 2) Managerial 3) Environmental .Results and DiscussionResults of sensitivity analyzes demonstrated that land-use and land cover change had a further effect on peak discharge. In sub-basin 1, by 20% increase in the curve number, the level of peak dumping increased by more than 111%, with a return period of 2 year; while a 20% increase in precipitation, in the same return period, rises the peak discharge only 3%. The peak discharge time in some sub-basins was brief due to the presence of impermeable surfaces, so that in sub-basins 4, 6, 7, and 8, the peak discharge time was less than 30 minutes. These results highlight the dangers of these floods and the need for proper flood planning and management in these sub-basins. The results of the Manning coefficient demonstrated that we can reduce flood damage by applying management measures in the future, as well as paying attention to the feedback between urbanization and the flood zone. Roughness control by applying management programs can reduce the area of flood zones to 0.1 square kilometers. In this case, buildings should be removed from the river, and there should be no structure in the path of the river. According to the questionnaires in the inner city part, the most fundamental factor in intensifying the flood damage was related to “activities of local people” with the average of 3.59. In the upper part of the city, the most influential factors were ascribed to “managerial factors” with the average of 3.79.ConclusionIn a general conclusion, it can be concluded that the role of human factors in the occurrence and intensification of floods was much greater than rainfall. Therefore, in order to manage and control floods, it is necessary to prevent the change of land use and the reduction of permeability. And management programs should be aimed at increasing surface permeability. We suggest that more research be done on the role of economic and social factors in increasing flood risk in other climate zones.

The failure of rock mass is mainly due to the failure of the structural plane, which is an important factor to reduce the mechanical properties and stability of rock mass. The shear strength of rock mass is one of the parameters for the stability calculation of large-scale rock mass engineering. The shear strength of a rock structural plane is strongly influenced by surface morphology. Considerable research has been conducted regarding the correlation between two-dimensional structural plane morphology and shear strength. However, quantitative research on three-dimensional (3D) morphology is relatively limited. In this study, 3D printing technology was used to create molds. Using cement and sand as the main materials, additives such as early strength and water-reducing agents were added, and test samples of irregular surface topography were created. The 3D roughness was quantified by formula calculation. Using a ZScanner® 800 hand-held 3D laser scanner to perform scanning on the structural surface, the parameter curve was analysed by generating 3D coordinate information and a 3D image of the fracture surface, and the quantitative parameter Mp3D{M}_{\text{p}}^{3\text{D}} describing the 3D morphology of the structural surface was constructed. The change rule of Rp3D{R}_{\text{p}}^{3\text{D}} and joint roughness coefficient (JRC) were analysed under different scanning resolutions, Δ(r), the scanning precision was suggested, and the functional relationship between JRC and Mp3D{M}_{\text{p}}^{3\text{D}} was established. Finally, a formula for shear strength parameters considering the 3D characteristics of a structural plane surface was established. The model validation results show that the experimental data were within the 95% confidence band of the model curve, the average error of the shear strength was 10.4%, the errors of friction angle and cohesion, C, were 3.4 and 9.4%, and the reliability was fine.

Soil–rock mixture (S–RM) deposits are encountered quite often in most of the landslide sites, especially in the lower Shivalik region of the Indian Himalayas. The assessment of shear strength of such deposits is difficult due to complex interaction of rock particles with sand fines matrix. Limited studies are available in the literature which deals with shear strength response of S–RM. As a result, very few approaches are available in the literature that can be applied to assess the shear strength of S–RM. The present study makes an attempt in the direction of solving this problem through an extensive laboratory study. Laboratory tests were performed on samples of soil–rock mixture derived from four origins. The tests involved usual index tests to characterize the S–RM, Point Load Strength Index tests on rock particles to get rock strength and direct shear tests (small (i.e. conventional) and large size) on S–RM samples having different gradations. The results are analysed and existing approaches are evaluated for their applicability to S–RM. The analysis indicates that in general the existing approaches do not adequately capture the shear strength response of S–RM. Conceptually Barton–Kjaernsli approach which was originally suggested for rockfill materials was found to the most promising approach. Modifications have been suggested to Barton–Kjaernsli approach to make it applicable to S–RM. [ABSTRACT FROM AUTHOR]

Efforts for getting the maximum efficiency from the existing water resources and to implement new projects are getting more attention these days. Determining the flow resistance for the project design and control process in open channels requires sophisticated applications. It is usually essential to be aware of the characteristics of the channel and flow to determine the hydraulic roughness, which represents the resistance of the flow. Hence, empirical calculation and evaluation of the hydraulic roughness will support future design and planning processes. In this study, four different particle sizes (d50= 28mm, 17.5mm, 4mm, and 1.75mm) that were fixed on blocks were used. These particle sizes were then used as the bed covering together with, three different horizontal bed slopes, and flow rates in the experiments to determine the associated Manning roughness, n. During the experiment, Froude number values were examined and it was determined that, in 32 experiments the flow regime can be considered as subcritical. Alternatively, the Lotter method was used to confirm the roughness values obtained by the Manning equation. It was concluded that the roughness values obtained by the selected methods have good concordance with each other. [ABSTRACT FROM AUTHOR]

This study aims to fully explore the influence of rock joint roughness in the slope stability analysis of an open mine. Therefore, based on the least squares parameter estimation method, a generalized shear strength parameter coupling roughness, which is used to evaluate a slope design, was established by a matching formula reflecting the relationship between the roughness coefficient and the shear strength parameter. Firstly, to verify and calibrate the model, physical direct shear tests were conducted on serrated rock joints, and the effect of roughness was analyzed qualitatively. The results show that an increase in tooth height increases the internal friction angle but decreases cohesion. Therefore, the rock joint direct shear test numerical model by PFC-2D was established and compared with the physical test curve, effectively verifying its correctness. The relationship between cohesion c and internal friction angle φ with roughness coefficient JRC was further quantified, and the new model was then fitted to characterize the relationship between roughness and shear strength parameters. This method is applied to the design optimization of an open pit mine slope. The new parameters are input to GeoSMA-3D, which is used to search for the key block of a bedding slope on an open-pit mine, to optimize the design of the slope. [ABSTRACT FROM AUTHOR]

The current research is focused on investigating the influence of bearing irregularities like eccentricities (e), non-circularities (G), L/D ratio (ß), surface roughness coefficient (Y) on hydrodynamic performance of journal bearing such as load bearing capacity, friction force, lubricating oil flow. The performance is evaluated through finite difference method technique implementing a Newton-Raphson method of error convergence. The simulation outputs were than designed using an optimization tool entitled as Design of Experiment (DoE) on basis of response surface methodology (RSM). The outputs of RSM models were meant to forecast the response parameters like, load bearing capacity, friction force, flow of lubricant and further required to identify the noticeable interdependencies within the input parameters while evaluating the lubrication performance. The optimization of the bearing irregularities is done considering desirability approach of the response surface methodology in identifying proper combination of parameters. [ABSTRACT FROM AUTHOR]

The weighting factor of the sediment connectivity index (IC) is a challenging component of this index and must be properly explicated for different situations. The aim of this study is to develop a proper weighting factor for calculating IC based on experiments on three tilled soils from dry-farming fields in Kouheen, Sararud, and Gachsaran regions under a 111 mm/h rainfall simulation using a 5.8 m2 laboratory flume with a slope of 12%. For each soil sample, two rain events (R1 and R2) were simulated with an interval of 4 hours, and the soil losses were measured. In addition, a digital elevation model with a pixel size of 2 mm was prepared by accurate photography after each rain followed by calculating the IC based on roughness coefficient (RI) as the weighting factor. Measured soil losses of two rainfalls were 4796 and 3909 g for Gachsaran soil, 3465 and 2464 g for Kouheen soil, and 2679 and 2105 g for Sararud soil, respectively. The result shows that with increasing IC based-RI, soil loss was decreased which indicates the inadequacy of RI alone as a weighting factor. To develop a new weighting factor, several physical and chemical characteristics of soils were used in combination with RI. A comparison of the results showed that the IC based on a weighting factor obtained from the combination of mean weighted aggregate diameter, penetration resistance, and RI, has the highest coefficient of correlation with soil losses (0.92, P

Open conduit modeling of cave stream floods can yield useful information about water velocities and shear stresses, which can in turn be used to estimate sediment transport capabilities. All such calculations require roughness coefficients for estimating energy losses and a priori knowledge of either discharge or flow depths to set model boundary conditions. However, the difficulties associated with observing in-cave floods generally preclude measuring discharge; roughness coefficients must be assumed based on channel properties. To overcome these challenges, we monitored stream flow depths in Fullers Cave, Greenbrier County, West Virginia using pressure transducers, and simultaneously measured stage and discharge in a karst window immediately upstream of the cave. Five pressure transducers were deployed opportunistically along a 93-meter-long reach in a 10+ meter high canyon averaging 1.5 to 3 meters wide. Stage-discharge relationships were determined for the karst window using an electromagnetic flow meter for floods with peak discharges of 1.66 m3 s-1 or less. The collected data was used to obtain the empirical Manning's n roughness values, head losses, and energy gradients. Calculated floodwater velocities are comparable to values obtained from scallops on passage walls. Major energy losses were observed where breakdown partially occludes the passage. At peak flow, Manning n values average 0.053 for reaches typified as cobble-floored canyons, but n was 0.069 in the breakdown reach. Roughness values declined exponentially with increasing discharge, but friction slopes calculated using head losses show more complex relationships with discharge. Notably, n values back calculated using bed gradients differ from those calculated using measured head losses by as little as 12%, so the use of bed gradients in roughness estimations will generally yield reasonable approximations of flow conditions. Fullers Cave experiences significantly larger open conduit floods than we observed, so additional work is needed to estimate roughness coefficients for higher discharges. Our empirical roughness coefficients can be applied to similar cave passages in other caves and contexts, including modeling slot canyon-like channels, and our methods demonstrate a technique for measuring hard to obtain data. The addition of data for open conduit conduits significantly expands the range of environments that can be modeled using empirical data beyond pipe-full caves. Applications include studying flooding, sediment transport, and bedrock erosion process. All of these topics will be addressed in Fullers in the future.

The roughness coefficients of erosion-control coatings based on geomats are studied. The roughness coefficients were calculated following an analysis of relevant publications. The process of determining the roughness coefficient of geomats filled with crushed stone and bitumen-polymer binder is described. Existing formulas for calculating the roughness coefficient of geomats are analyzed to identify the most optimal approaches. The obtained roughness coefficient values are compared with those reported in other studies on similar coatings. [ABSTRACT FROM AUTHOR]

Over the past few years, the concentration of fine particulate matter (PM2.5) in Delhi's atmosphere has progressively increased, resulting in smog episodes and affecting people's health. Therefore, accurate and reliable forecasting of PM2.5 concentration is essential to guide effective precautions before and during extreme pollution events. In this work, soft computing techniques, including Artificial Neural Network and Gaussian Process Regression are employed to predict PM2.5 concentrations in Delhi. Four models, namely, multi-layer feed-forward neural network (MLFFNN), General regression neural network, Gaussian process regression with ARD squared exponential kernel (GPARD_sqexp) and Gaussian process regression with ARD rational quadratic kernel (GPARD_rat_quad) are built using meteorological and air quality data corresponding to a two-year period (2015–2016). The results of the study suggested that MLFFNN showed the best prediction performance among the four models, with testing correlation coefficient (R) 0.949, Root mean square error 30.193, Nash–Sutcliffe efficiency index 0.892 and Mean absolute error 18.388. Moreover, sensitivity analysis performed to understand the importance of different input variables reported that PM10, wind speed, air quality index and aerodynamic roughness coefficient (Z0) are the most critical parameters influencing MLFFNN model forecasts. On the whole, the work has demonstrated that the artificial neural network model is more capable of dealing with PM2.5 forecasting in Delhi urban area than the Gaussian process regression model. [ABSTRACT FROM AUTHOR]

Input data, parameters, and the structure of mathematical models introduce uncertainty in the results; thus, sensitivity analysis is required when implementing a model or as a preliminary step. This study evaluated the sensitivity of Manning's coefficient based on landcover types in the floodplains and the main channel, for calculating water levels and defining flood extent. The mike 11 one-dimensional [1-d] model was used in this study on a five-kilometer stretch of the Santa Barbara River in southern Ecuador. Six hundred Monte Carlo simulations were run for each flood event, and the results were used to assess the robustness of the 1-d model. This analysis revealed that Manning's coefficient was sensitive to changes: there was a difference of up to 1.02 m between maximum and minimum water levels. The resulting flood maps, however, revealed almost imperceptible differences in flood extent. These findings demonstrate that the recommended Manning's mean value is reliable for flood hazard mapping of Mountain Rivers in the inter-Andean region. [ABSTRACT FROM AUTHOR]

The present study intends to use machine learning (ML) and deep learning (DL) models to forecast PM2.5 concentration at a location in Delhi. For this purpose, multi-layer feed-forward neural network (MLFFNN), support vector machine (SVM), random forest (RF) and long short-term memory networks (LSTM) have been applied. The air pollutants, e.g., CO, Ozone, PM10, NO, NO2, NOx, NH3, SO2, benzene, toluene, as well as meteorological parameters (temperature, wind speed, wind direction, rainfall, evaporation, humidity, pressure, etc.), have been used as inputs in the present study. Moreover, this is one of the first papers that employ aerodynamic roughness coefficient as an input parameter for the prediction of PM2.5 concentration. The result of the study shows that the LSTM model with index of agreement (IA) 0.986, root mean square error (RMSE) 21.510, Nash–Sutcliffe efficiency index (NSE) 0.945, (coefficient of determination)R2 0.945, and (correlation coefficient)R 0.972 is the best performing technique for the prediction of PM2.5 followed by MLFFNN, SVM, and RF models. The sensitivity analysis for the LSTM model reported that PM10, wind speed, NH3, and benzene are the key influencing parameters for the estimation of PM2.5. The findings in this work suggest that the LSTM could advance in PM2.5 forecasting and thus would be useful for developing fine-scale, state-of-the-art air pollution forecasting models. [ABSTRACT FROM AUTHOR]

River channel deflectors are environmentally friendly low head hydraulic structures constructed from wood, stones and coarse gravel Their aim is to protect river banks against erosion, to change the direction of river flow making the river course naturally meandrous instead of artificially straight, to provide natural refugia for fish and invertebrates and finally to improve hydraulic discharge conditions. However, from the designing point of view they are difficult to represent in hydrodynamic models since they are constructed and fixed in the river bed differently. For this reason, in hydraulic models' deflectors may be treated as modifications to the value of the watercourse bed roughness or reduction in the active part of the cross-section. Thus, to test the suitability of one-dimensional models for river restoration involving river deflectors, a 1-D numerical model of the lower section of the Flinta river (Wielkopolska Province, Poland) was prepared. To do that, firstly three channel flow deflectors were constructed and installed in the lower section of the Flinta river. Secondly, hydrometric measurements were continued systematically over three years. Next, based on field studies and field data, calculations were made using the HEC-RAS 1-D software. Several variants of the shape and the effect of deflectors were tested. On this basis, the variability of the roughness coefficient value for the Flinta riverbed after the implementation of deflectors was analyzed. The novelty of the research is that the obtained results show that river channel deflectors have a significant influence on the processes of morphological changes (such as: velocity distribution, grain size changes, tendency towards channel meandering, channel slope) of the riverbed and thus also on changes in hydromorphological parameters of river flow. The presented case study confirmed the potential for effective deflector operation for the velocity range of 0.10 – 0.30 m·s−1. The maximum changes of the river bed elevation after the deflectors had been introduced reached 0.10 m. It was also found that the effect of deflectors on roughness at high water levels was non-significant and did not increase the risk of flooding. For Q1% flow, the implementation of flow deflectors had no significant effect on the capacity of the studied river section. Only slight subduction of 0.02 – 0.03 m of the water surface in the vicinity of the deflectors could be observed compared to the model from before the restoration activities. The greatest impact of the channel deflectors is seen at low water levels and low flows that do not exceed average flow values. Finally, it was shown that the best solution to implement deflectors into a one-dimensional model is to consider their influence as a change in the value of Manning's coefficient. The obtained results can be considered universal in relation to typical transformed small lowland watercourses that have been straightened and regulated and are to be subjectedto the process of river restoration. [ABSTRACT FROM AUTHOR]

The stepped spillway is a cost-effective hydraulic structure to dissipate the energy of large water flow over the spillway of a dam. In this study, the focus was placed on the effects of triangular prismatic elements (TPEs) on the hydraulic performance of a stepped spillway. Nine stepped spillway models were experimentally and numerically investigated with different shapes and layouts of TPEs. To adopt a proper turbulent model, RNG k-ε and standard k-ε models were utilized. The computational model results satisfactorily simulated the complex flow over the stepped spillway of experiment cases, including velocity distributions and pressure profiles on the step surfaces. The results indicated that the installation of TPEs on stepped spillways can be an effective way to reduce cavitation effects. Installing TPEs on stepped spillways increased the energy dissipation rate up to 54%. The performance of stepped spillways was improved when TPEs were spaced more closely together. Furthermore, the relationships between the roughness coefficient (f) and the ratio of the critical depth to the step roughness (yc/k) were obtained with high accuracy using the experimental data. HIGHLIGHTS The Flow-3D model was applied to examine the effects of triangular prismatic elements (TPEs) on the hydraulic performance and energy dissipation of stepped spillways.; Two types of TPEs with different spacing were experimentally investigated for varied flow rates.; Stepped spillways with TPEs are more efficient in terms of energy dissipation.;

Aim of the study: The aim of the study was to determine the applicability of the Colebrook-White equation with modifications to its constants K1, K2 and K3, proposed by various authors of the research on water flow resistance in open channels, taking into account the influence of the grain roughness of the mountain stream bottom. Material and methods: Based on the field measurements of the water flow velocity, the water flow rate Q was calculated, and then the average Manning roughness coefficient was calculated using the formula developed by Barnes. This coefficient made it possible to calculate the roughness coefficient determined from the transformed Chézy-Maninng equation. The calculated drag coefficient was compared with the results of the calculations from the Colebrook-White equation with the constants K1, K2 and K3. Results and conclusions: As a result of the measurements, the calculated roughness coefficient for this stream is 0.044 m-1/3∙s. It was found that from the Colebrook-White equation with the constants K1, K2 and K3, determined by Keulegan and by Rouse, for the absolute roughness value (ks) in the range 0.063 – 0.066 m, which was calculated by the Thompson and Campbell formula and the Irmay formula, it is possible to obtain the value of the resistance coefficient for which the roughness coefficient is the closest to that obtained from the measurements. The roughness coefficient of the tested section of the Racławka stream, calculated using this modification of the Colebrook-White equation, is within the range of 0.040 - 0.048 m-1/3∙s.

Flow resistance is a critical calculation parameter in hydraulic engineering. In this study, the roughness coefficient of a circular drainage pipe with sedimentation was investigated under open-channel flow conditions using experimental measurements and numerical calculations. The ratio of the height of the sediment placed in the pipe to the diameter was defined as the sedimentation degree. The Manning roughness coefficient (n) was determined for pipes with different sedimentation degrees. Moreover, numerical simulations were performed for circular pipes with diameters of 0.152 m and a slope of 0.003, with discharges varying between 1 and 8 L/s. The results of the numerical calculations were validated in terms of the water surface and Manning's n using the corresponding experimental data. Accordingly, an equation in the form of the Moody formula was proposed to estimate the roughness coefficient. Subsequently, the predicted Manning roughness coefficient obtained through the proposed equation was compared with independent experimental results. The results indicate that the equation accurately predicts Manning's n in a pipe with sedimentation, which can provide a theoretical basis for the design of drainage pipelines. [ABSTRACT FROM AUTHOR]

This study aims to fully explore the influence of rock joint roughness in the slope stability analysis of an open mine. Therefore, based on the least squares parameter estimation method, a generalized shear strength parameter coupling roughness, which is used to evaluate a slope design, was established by a matching formula reflecting the relationship between the roughness coefficient and the shear strength parameter. Firstly, to verify and calibrate the model, physical direct shear tests were conducted on serrated rock joints, and the effect of roughness was analyzed qualitatively. The results show that an increase in tooth height increases the internal friction angle but decreases cohesion. Therefore, the rock joint direct shear test numerical model by PFC-2D was established and compared with the physical test curve, effectively verifying its correctness. The relationship between cohesion c and internal friction angle φ with roughness coefficient JRC was further quantified, and the new model was then fitted to characterize the relationship between roughness and shear strength parameters. This method is applied to the design optimization of an open pit mine slope. The new parameters are input to GeoSMA-3D, which is used to search for the key block of a bedding slope on an open-pit mine, to optimize the design of the slope.

Open conduit modeling of cave stream floods can yield useful information about water velocities and shear stresses, which can in turn be used to estimate sediment transport capabilities. All such calculations require roughness coefficients for estimating energy losses and a priori knowledge of either discharge or flow depths to set model boundary conditions. However, the difficulties associated with observing in-cave floods generally preclude measuring discharge; roughness coefficients must be assumed based on channel properties. To overcome these challenges, we monitored stream flow depths in Fullers Cave, Greenbrier County, West Virginia using pressure transducers, and simultaneously measured stage and discharge in a karst window immediately upstream of the cave. Five pressure transducers were deployed opportunistically along a 93-meter-long reach in a 10+ meter high canyon averaging 1.5 to 3 meters wide. Stage-discharge relationships were determined for the karst window using an electromagnetic flow meter for floods with peak discharges of 1.66 m3 s-1 or less. The collected data was used to obtain the empirical Manning's n roughness values, head losses, and energy gradients. Calculated floodwater velocities are comparable to values obtained from scallops on passage walls. Major energy losses were observed where breakdown partially occludes the passage. At peak flow, Manning n values average 0.053 for reaches typified as cobble-floored canyons, but n was 0.069 in the breakdown reach. Roughness values declined exponentially with increasing discharge, but friction slopes calculated using head losses show more complex relationships with discharge. Notably, n values back calculated using bed gradients differ from those calculated using measured head losses by as little as 12%, so the use of bed gradients in roughness estimations will generally yield reasonable approximations of flow conditions. Fullers Cave experiences significantly larger open conduit floods than we observed, so additional work is needed to estimate roughness coefficients for higher discharges. Our empirical roughness coefficients can be applied to similar cave passages in other caves and contexts, including modeling slot canyonlike channels, and our methods demonstrate a technique for measuring hard to obtain data. The addition of data for open conduit conduits significantly expands the range of environments that can be modeled using empirical data beyond pipe-full caves. Applications include studying flooding, sediment transport, and bedrock erosion process. All of these topics will be addressed in Fullers in the future. [ABSTRACT FROM AUTHOR]

Manning-type relations do not contain the term viscosity, which limits their use to the field of rough turbulent flow. Strickler roughness coefficient k or n of Manning are estimated with great difficulty, requiring a proven practical experience. In order to simplify the problem and allow a rapid calculation of k, the main objective of the present study is to establish an explicit analytical relation which links k and the absolute roughness?. To do this, it was useful to combine the rational Darcy-Weisbach relationship and the empirical Manning-Strickler formula. After some development, the function (;) () * (k;ε) =ε*, where ε* = ε/Dh * is the relative roughness, was clearly defined. It was possible to calculate the mean value of the function ? in the practical range of ε* such that ? is equal to a constant. This constant is different from that proposed by the literature. [ABSTRACT FROM AUTHOR]

Historically, streamflow daily values are obtained indirectly by applying a rating curve on water level data. In several Amazon basin stations, a backwater effect impacts the flow, thereby invalidating the rating curve method. To account for this effect, we generated a daily discharge data series by applying the Manning equation to daily water level data from the Manacapuru station located on the Solimões River. Each Manning parameter had to be established based on its relationship to the water level. The roughness coefficient was obtained by inverting the Manning equation for each discharge measurement, and a “coefficient–stage” relationship was established. The slope of the energy line was estimated by the water-surface slope between two fluviometric stations. Discretizing the equations for each parameter enhanced the discharge estimation for the Manacapuru station, thereby generating an accurate discharge data series.

Aim of the study: The paper presents the results of research carried out in the Będkówka stream. The aim of study was to determine the influence of large roughness elements on the change in the coefficient of roughness and resistance coefficients. Material and methods: A section of the stream was selected for the study, on which nine measurement cross-sections were determined, including three of them were large roughness elements. The dimensionless resistance coefficient (λ) was calculated from the Colebrook-White equation. Results and conclusions: It was stated that in sections with large roughness elements, both water flow velocities as well as resistance and roughness coefficients obtained values higher than in other cross-sections. The coefficient of cross-section cover (ω) and degree of change of roughness coefficient Δn were also calculated and a regression relation Δn = f (ω) was determined. This relationship will allow to determine the change in the hydraulic conditions of the water flow, expressed by the change in the coefficient of roughness.

A timely and cost-effective method of creating inundation maps could assist first responders in allocating resources and personnel in the event of a flood or in preparation of a future disaster. The Height Above Nearest Drainage (HAND) model could be implemented into an on-the-fly flood mapping application for a Canada-wide service. The HAND model requires water level (m) data inputs while many sources of hydrological data in Canada only provide discharge (m3/sec) data. Synthetic rating curves (SRCs), created using river geometry/characteristics and the Manning's formula, could be utilized to provide an approximate water level given a discharge input. A challenge with creating SRCs includes representing how multiple different land covers will slow impact flow due to texture and bulky features (i.e., smooth asphalt versus rocky river channel); this relates to the roughness coefficient (n). In our study, two methods of representing multiple n values were experimented with (a weighted method and a minimum-median method) and were compared to using a fixed n method. A custom ArcGIS tool, Canadian Estimator of Ratings Curves using HAND and Discharge (CERC-HAND-D), was developed to create SRCs using all three methods. Control data were sourced from gauge stations across Canada in the form of rating curves. Results indicate that in areas with medium to medium–high river gradients (S > 0.002 m/m) or with river reaches under 5 km, the CERC-HAND-D tool creates more accurate SRCs (NRMSE = 3.7–8.8%, Percent Bias = −7.8%—9.4%), with the minimum-median method being the preferred n method. [ABSTRACT FROM AUTHOR]

High rainfall intensity will generate different response on the concrete block pavement (CBP) performance. A study found that larger openings of CBP did not lead more water penetrated. In other study, larger openings can lead greater decrease in runoff velocity. The correlation between the openings, water penetration and runoff velocity has remained unclear. In this study, we investigated hydraulic performance of CBP as an impact of surface roughness condition, under high rainfall intensities, saturated sub-base layer, and various slope surfaces. We conducted experiment using a 2 m by 6 m of rectangular CBP layer with herringbone 90 and basket-weave pattern. We used a modified dye tracing method in view to monitor the surface flow velocity under various high rainfall intensities. The results showed that hydraulic performance of surface runoff in the CBP layer was more influenced by the surface roughness condition. The roughness condition was very sensitive to the change in surface configuration of the CBP. The relationship between rainfall intensity, surface slope and roughness number followed polynomial functions. A further study is required to investigate the appropriate quality of CBPs, which have high durability applied over a steep slope surface and under high rainfall intensities.

The samples of slightly weathered granite drilled before the construction of Runyang suspended bridge's north anchorage are used as the research object in this paper. Through a lot of shear strength tests of concrete-bedrock rough cement face, the influence of the cement face roughness on the shear strength, shear deformation characteristics and shear failure mechanism were systematically studied. The results show that: The post-peak stress–strain curves of smooth and rough cement faces are obviously different. The shear stress–strain curve of cement face can be generalized into 3 types. The shear stress–strain model of rough cement face is the most general form, and the smooth cement face and no cementation are its special cases. The empirical relation between cement face roughness JRC and shear strength parameters is established by the fitting of experimental data. When the cement face is climbing, the internal friction angle increases with the climbing angle. When the climbing angle is constant, the increase of cohesion is positively correlated with the ratio of fluctuation difference and wavelength. When the climbing thrust is equal to the gnawing thrust, the specimen is transformed from climbing to gnawing. [ABSTRACT FROM AUTHOR]

In the present study design value of the roughness coefficient for a lined distributary (Chena distributary district Kasur) was validated and its effect on the water drawing capacity of outlets was assessed. Chena distributary, off takes from the left bank of Depalpur canal, at RD 359020. The total length of the distributary is 25.46 km. More than 50 percent of its length has been lined. In this study, a reach from RD 0.00 to 7590 having a trapezoidal lined section was used. The total numbers of outlets being fed by the distributary were 62. The first 17 outlets were included in the study. A comparison was made between design and field measurements of the hydraulic parameters of the canal and the outlets. Simulations of canal and outlet flows were made using the (Simulation Irrigation Canal) SIC model. A considerable difference was observed between the design and the prevailing water surface profiles and resultantly water drawing capacity of the outlets. The results showed that the prevailing value of the roughness coefficient was 0.02 instead of 0.016, the design value. Because of increased roughness coefficient value, due to sedimentation or due to some tempering, the depth of flow increased in the head reaches. Therefore outlets at the head were drawing more than allocated share. In the tail reaches due to reduced discharges, tailenders were deprived of their due share. Not only cleaning and maintenance of lined portion of canal at regular intervals but also strict regulations to avoid tampering are required for sustainable operation of an irrigation system as per design. [ABSTRACT FROM AUTHOR]

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The prediction of water levels in rivers is important to prevent economical as well as human losses caused by flooding. Hydraulic models are commonly used to predict those water levels and take actions to mitigate flooding damage. In this research, a 2D approach to solve the depth average Reynolds Average Navier Stokes (RANS) equations, called Conveyance Estimation System (CES), is analyzed to explore its capabilities for prediction. This article presents an extension of the study performed in Knight y col., 2009. More specifically, in this study, a more detailed characterization of the roughness parameter and the number of roughness zones is explored producing additional scenarios. The performance of each scenario is evaluated by means of different fitting functions using rating curves for comparison. The research shows that the use of an adequate roughness description, such as a roughness factor calibrated for the whole cross section or a boulder roughness model calibrated for the channel bed plus roughness values from the CES roughness advisor for banks, leads to optimal model results in a mountain river. [ABSTRACT FROM AUTHOR]

The present study aims at the influence of the land use from the riparian zone of large rivers with potential flood risk (APSFR) on hydraulic parameters. An experimental campaign was carried out based on 3 scenarios (i) the current situation of land use, (ii) all forests considered arable land, (iii) all land considered forested. Based on hydraulic simulations, changes in floodplain land use structure, expressed in the model by changing roughness coefficients, can lead to significant changes in flood propagation, highlighted by changes in maximum water level and velocity, or maximum flooded area. These changes in the hydraulic regime of the large rivers are important aspects, which must be taken carefully considered into the urban and regional development plans design. [ABSTRACT FROM AUTHOR]