An experimental study to determine the effects of particle size and bifurcation angle on the distribution of flow and sediment transport parameters in a bifurcated channel.

An experimental study to determine the effects of particle size and bifurcation angle on the distribution of flow and sediment transport parameters in a bifurcated channel. | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article An experimental study to determine the effects of particle size and bifurcation angle on the distribution of flow and sediment transport parameters in a bifurcated channel. Amit Das, Bibhas Chandra Barman, Nityananda Nandi This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-3909326/v1 This work is licensed under a CC BY 4.0 License Status: Posted Version 1 posted You are reading this latest preprint version Abstract Flow and sediment sharing in a bifurcated channel are considered to be a very important issues in river engineering and flood management. The present study has been conducted based on the field bifurcation of the Kangsabati river bifurcates at Kapastikri, about 75 km downstream of Kangsabati reservoir of West Midnapore, West Bengal, India. A scaled physical model simulating bifurcation region was conducted on a fixed-bed model at the Laboratory of River Research Institute (RRI), West Bengal (WB), India. The model set-up has been run with a range of discharges, including low, moderate, and high with three different sets of bifurcation angles. Furthermore, three different sizes of sediment of varying densities have been used to find the transport capacity of sediment for individual bifurcated angle. A set of data have been collected for different conditions like varying discharge, angle of bifurcation, mean size of sediment () particle and a comprehensive analysis have been done with respect to collected data to see how discharge and sediment load (bed-load) are distributed over the bifurcated branches. The present physical model study has determined the optimum discharge in the main channel for which the sediment and discharge get equally distributed over the bifurcated branches. The experimental data confirm that the distribution of bed load is dependent on the shape of the bifurcation and the sediment transport ratio ( s 1 /s 2 ) is sensitive to the angle of bifurcation in which s 1 & s 2 represent sediment transport rate (kg/hr) in respective branches. River bifurcation Sediment transport Bifurcation angle Bed-load Physical model Figures Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Introduction The journey of a river from its source in the mountains to the sea involves a complex interplay of physical processes (such as meandering, bifurcation, bar formation etc.), and the river undergoes several changes in its characteristics and behaviours. The specifics of a river bifurcation are dependent upon several elements, including the river's flow rate, the amounts of sediments present, the land's slope, and the existence of vegetation or other impediments, whether man-made or natural. Generally speaking, river bifurcations are dynamic systems that are subject to alter over time due to both natural and manmade influences. At a river bifurcation, a change in the distribution of sediment often leads to aggradation in one of the downstream branches. Consequently, the bifurcation structure will become unstable when the water discharge through this branch decreases and the water discharge through the other branch increases at the same time. This has an impact on the possibility of floods in one branch, water scarcity and poor water quality (Faulstich et al. 2023 ; Grzywna and Sender 2021 ) in another branch, navigability, as well as the availability of water for vegetational, agricultural and human needs. A good understanding of flow and sediment distribution process is thus crucial for creating diverse habitats for wildlife and providing opportunities of human use such as irrigation, transportation, and sharing of water. Flow Bifurcation are typical features of braided rivers, alluvial fans and river deltas, and strongly determine the stability of a river system. Different aspects that influence the flow and sediment distribution in a bifurcated channel and their stability. Stability of bifurcation is one of an important aspect, (Wang et al. 1995 ) theoretically investigated the stability of the configuration weather both branch open or one of the branches get closed. (Miori et al. 2006 ) discusses the equilibrium configurations of a bifurcation in a gravel bed channel with erodible banks which shows that stable equilibrium solutions are characterized by a strongly unbalanced partition of water and sediment discharges in the two branches. River deltas typically contain networks of bifurcating channels and the complexity of the bifurcation problem lies in the determination of the distribution of sediments at the downstream branches (Hoitink et al. 2020 ; Das et al. 2022 ) proposed an empirical nodal point relationship to estimate the flow and sediment distribution for a channel bifurcation (Melman 2011) discusses the flow and sediment distribution in a bifurcated channel, specifically focusing on the Montaño - Murindo bifurcation of the Atrato river in Colombia, mentions that the division of flow and sediments is influenced by local geometrical phenomena, such as the angle of offtake and river bends. A good understanding of flow and sediment distribution process is thus crucial for creating diverse habitats for wildlife and provide opportunities of human use such as irrigation, transportation, and hydropower generation. Several experimental studies have investigated the angle at which bifurcations develop, shedding light on their sediment distribution dynamics. Researchers such as (Riad 1961 ; Den Dekker and Van Voorthuizen 1994 ; Islam 2000 ), and others have conducted physical model studies in this regard. These studies generally reveal that sediment distribution correlates more than linearly with discharge distribution; a wider diverting angle tends to attract more sediment, particularly bed load, while suspended sediment distribution tends to align more closely with discharge distribution. Early experiments by (Bulle 1926 ) and subsequent studies by (Seminara and Tubino 2011 ; Rezapour et al. 2009 ) confirm this tendency for sediment to preferentially deviate toward the lateral branch, often disproportionately to water discharge distribution. (Islam et al. 2006 ) conducted experiments to validate the nodal point relation proposed by (Wang et al. 1995 ) finding that the parameter k in the relation depends significantly on the bifurcation angle. Furthermore, (Herrero et al. 2015 ) conducted experiments with 900 channel diversions, emphasizing the interconnected nature of bed topography evolution, flow characteristics, and sediment distribution at fluvial diversions. (Vanoni 2006 ) suggested that there is no universally optimal bifurcation angle for channel diversions, as it varies based on factors such as discharge ratio in the main stream and intake geometry at the bifurcation point, including the radius of curvature Some studies have been carried out based on real bifurcations. (Sloff et al. 2003 ) report the results of a numerical modelling and experimental analysis on sediment behaviours in Pannerdense bifurcation. (Frings and Kleinhans 2008 ) carried out an analysis on data of three bifurcations in the Rhine River system: i.e. Pannerdense Kop, Ijssel Kop and Merwede Kop. The location of the bifurcation in relation to the planimetric shape of the river can play an important role in sediment distribution amongst the downstream branches. The bend sorting process that takes place in a river bend, distributing coarser sediment in the outer part of the bend and finer sediment in the inner part, causes that when a bifurcation is placed in a river bend, the outer branch receives less sediment than the inner one due to supply-limited conditions. The present study has been carried out based on actual field bifurcation of river Kangsabati, originated from Chota-Nagpur plateau in Purulia district enters Paschim Midnapore in Binpur area, West Bengal, which then bifurcates at Kapastikri, about 75 km downstream of Kangsabati reservoir. This bifurcation in the river Kangsabati is found to cause severe problems during high flood discharge in the adjoining areas of Ghatal subdivision. It has been observed that the major portion of Kangsabati water passes through Old Kasai and remaining water passes through New Kasai in case of low and moderate discharges. The share through the New Kasai increases with the increase of discharges. At very high discharges (greater than 1200 cumec), the New Kasai share raises up to nearly 45%. This seems to be due to inherent morphology at the junction point at Kapastikri which very often causes flood in adjoining Ghatal Subdivision and Panskura during high discharge. It is, therefore, required to bring this bifurcation to a condition when the flow in the daughter channels will not cause any inundation problem. So, to study the sharing of discharges and bed-load transport, model tests have been conducted on a fixed-bed model at River Research Institute (RRI), West Bengal (WB), India. Further, an experimental study has been conducted with different sets of bifurcation angle, roundness of bifurcation point, varying upstream discharge, varying sediment particle size ( \({d}_{50}\) ) to see the distribution of discharge and sediment over the downstream branches with the same longitudinal slope. A comprehensive analysis has been done based on data collected from the physical model to find an optimal solution in which discharge and sediment get more or less equally distributed over the bifurcated channel for a given upstream discharge. This may help the nearly equal sharing of water during moderate and high flood discharges so that the undesirable discharge doesn’t pass through a particular channel. In this study the most vulnerable river is Old Kasai, a branch of the Kangsabati river. Materials and Methods Physical model set-up A general layout of the physical model set-up has been shown in Fig. 1(b) is comprised of three branches: a main branch (Kangsabati) which bifurcates into two branches; Old Kasai and New Kasai. The angle of bifurcation of Old Kasai and New Kasai are \({\theta }_{1}\) & \({\theta }_{2}\) , while the radius of curvature of the corresponding branches are \({r}_{1}\) & \({r}_{2}\) . A scaled physical model simulating the bifurcation of the Kangsabati river has been conducted at the River Research Institute (RRI), West Bengal, Mohanpur, Nadia, India, considering the horizontal and vertical scale ratios of 1:350 and 1:70, respectively Fig. 3 (c). So, the distortion factor is 5. The discharge ratio of prototype and model is 1: 0.000005. The maximum discharge of river Kangsabati is 4600 cumecs in 100 years return period (WAPCOS Ltd. 2009). The slope of the main Kangsabati is 0.000246 (m/m) and the slope of bifurcated branches i.e., Old Kasai is 0.000875 (m/m) and New Kasai is 0.0015 (m/m) (WAPCOS Ltd. 2009). The diversion angle of Old Kasai is 23º and New Kasai is 14º from the line of symmetry, ratio of their angle becomes 23:14. The radius of curvature for Old Kasai and New Kasai is 0.56 m and 0.777 m respectively. Furthermore, with this existing geometry additional two sets of bifurcation angle have been customised i.e., 45 ̊ and 60 ̊ with the ratio of bifurcation angle 23:14. The present study demonstrate the effects of bifurcation angle on the flow and sediment distribution over the bifurcated branches Simulation of hydraulic conditions The model experiments simulating bifurcation at Kapastikri in river Kangsabati have used the data of hydraulic observation (RRI, I&W Govt. of West Bengal, India) from 14th August 2012 to 31st October 2012 and 26th July to 8th November 2013. The discharge ratio of prototype and model is 1:0.000005. The model has been run with a range of discharges, including low, moderate, and high, with the selected discharges being 0.002, 0.004, 0.006, 0.008 and 0.010 \({m}^{3}/sec\) . Initially, water pumped from a well, it was first passed through a stilling chamber to minimise turbulence intensity, which allowed the flow to become natural before it reached the actual model setup. The boundary condition for the physical model is done with a rating curve obtained from the relationship of discharge vs gauge height. The scaled gauge height at the boundary is maintained by controlling the opening of the tail end gate as shown in Fig. 2 (c). The scaled gauge height in the main channel (Kangsabati), left channel (Old Kasai) and right channel (New Kasai) measured separately by pointer scale arrangements as shown in Fig. 2 (b) for a given discharge. The experiment performed multiple equilibrium condition runs to analyse how the water discharge and sediment transport rate varied between the two bifurcations for changing flow and sediment size conditions. Methods of experiment The physical model has been done with the primary goal to determine how discharge and sediments were distributed at a channel bifurcation. Analysis of field samples of river Kangsabati have been done and sediments indicated a prototype grain size of 0.275 and 0.285 mm for an average velocity of 0.55 and 1.04 m/sec. For scaled models, choosing the sediment size is getting more challenging, we can’t simply reduce particle size in accordance with model scale as particle size becomes very small that may cause major changes in cohesiveness qualities, entirely changing the sediment transport mechanics between the model and prototype. A quantitative analysis has been done in terms of sediment transport in the present study. Three different sizes of sediment of different densities were used to study the phenomenon. The sediment transport consists of bed load only. The mean diameters ( \({d}_{50}\) ) of the sediments used in the experiments were 0.190, 0.250 and 0.275 mm. For each sediment size, five upstream discharges of 0.002, 0.004, 0.006, 0.008 and 0.010 \({m}^{3}/sec\) have been used. The v-notch arrangement as shown in Fig. 2 (a) is used to measure the flow rate. The first step is to prepare the model with selected sediment and then run the model with the selected discharges. The upstream sediment load supplied during an experiment for a particular discharge has been determined from Engelund–Hansen sediment transport formula (Sulaiman et al. 2021 ) Sediment transport capacity is calculated as follows: \({q}_{t}=\) 0.05 \({\gamma }_{s}{V}^{2}{\left[\frac{{d}_{50}}{\left(\frac{{\gamma }_{s}}{\gamma }-1\right)}\right]}^{\frac{1}{2}}{\left[\frac{\tau }{\left(\frac{{\gamma }_{s}}{\gamma }-1\right){d}_{50}}\right]}^{\frac{3}{2}}\) Eq-(1) Where, \({q}_{t}=\) Sediment load discharge in kg/hr; \({\gamma }_{s}\) = Unit weight of sediment in kN/ \({m}^{3}\) ; V = Mean velocity of the channel in m/sec; g = Gravitational acceleration in m/ \({sec}^{2}\) ; ⍴= Density of the water in kg/ \({m}^{3}\) ; \(\tau =\) Bed shear stress in N/ \({m}^{2}\) ; \({d}_{50}\) = Diameter of sediment particle in m; For the upstream discharges of 0.002, 0.004, 0.006, 0.008 and 0.010 \({m}^{3}/sec\) , the average sediment loads ( \({s}_{0})\) were 1.5, 3, 4.5, 6 and 8.5 kg/hr respectively. The amounts of sediments estimated by using the Engelund–Hansen sediment transport formula corresponded very closely to the above sediment loads, i.e., the sediment transport in the main channel followed by Eq. (1). A sand feeder provides the supply of sediments placed at the main branch in such a distance so that the sediments supplied from the sand feeder are uniformly distributed before reaching the bifurcation point. The sediment falls from the sediment feeder into the wooden structure Fig. 1(d), which distributes the sediment uniformly over the main channel width. The experiment performed multiple equilibrium condition runs (i.e., when the discharges in the downstream branches were constant) to analyse how the water discharge and sediment transport rate varied between the two bifurcated branches for three different bifurcation angles by changing flow and sediment size conditions. The experimental run has been done with five different upstream discharge values as mentioned above and held other parameters i.e., bifurcation angle and sediment size constant, these two parameters isolated systematically by individually varying them across the experimental runs. Total of 45 experimental run was conducted with the combination of these three variables i.e., bifurcation angle, sediment size, and upstream discharge. Guage height was measured during each experimental run and the individual discharges of branches (New Kasai and Old Kasai) were calculated using a calibrating stage-discharge chart for the model. Ripples were formed in the channel bed at the end of the run. The sediments were transported through the bifurcated branch trapped in the sand traps which were located in the downstream section of each bifurcated branches. The deposited sediment in the sand trap was collected, oven dried for 24 hours and weighted. The sediment transport rate in the downstream bifurcated branches calculated knowing the total quantity of sediment collected from sand traps over the duration of experimental run. Results and discussion Influence of particle size and upstream discharge The model set-up experimented with different sets of bifurcation angle and different grain size, to study the effect of discharge and sediment distribution over the downstream branches. The quantity of discharge distributed in each bifurcated branches i.e., for Old Kasai branch is q 1 and for New Kasai branch is q 2 , measured for a specific discharge q in the main channel. Similarly, the quantity of distributed sediment in the bifurcated branches i.e., for Old Kasai branch is s 1 and for New Kasai branch is s 2 , measured for the corresponding discharges. The discharge ratio q 1 /q 2 and sediment discharge ratio s 1 /s 2 is presented in Table 1 to 3 for the corresponding discharge ( \({q}_{0}\) ) of 0.002, 0.004, 0.006, 0.008, 0.010 cumec. It has been observed from the table. 1 to 3 that when the discharge in the main channel increases, the discharge ratio q 1 /q 2 decreases and the value of the sediment discharge ratio increases. So, it may be concluded that the discharge ratio and sediment discharge ratio are not proportionally related. Table 1 Experimental data of model for bifurcation angle of 37 ̊ Main Channel Q ( \({ m}^{3}/sec\) ) Ratio of q 1 /q 2 Ratio of s 1 /s 2 d = 0.190mm d = 0.250mm d = 0.275mm d = 0.190mm d = 0.250mm d = 0.275mm 0.002 1.3767 1.3138 1.2468 0.8926 0.8701 0.8615 0.004 1.2474 1.2044 1.1897 0.9237 0.9069 0.8843 0.006 1.0061 0.9904 0.9891 1.0092 0.9872 0.9554 0.008 0.9928 0.9879 0.9686 1.1046 1.1039 0.9941 0.010 0.9899 0.9669 0.9599 1.3523 1.3006 1.2990 Table 2 Experimental data of model for bifurcation angle of 45 ̊ Main Channel Q ( \({ m}^{3}/sec\) ) Ratio of q 1 / q 2 Ratio of s 1 / s 2 d = 0.190mm d = 0.250mm d = 0.275mm d = 0.190mm d = 0.250mm d = 0.275mm 0.002 1.2767 1.1549 1.1129 0.9615 0.9010 0.8726 0.004 1.1733 1.0236 1.0164 0.9843 0.9689 0.9297 0.006 0.9989 0.9893 0.9878 1.1038 1.0104 0.9937 0.008 0.9750 0.9686 0.9578 1.1924 1.1405 1.1046 0.010 0.9187 0.9085 0.8828 1.3786 1.2649 1.2332 Table 3 Experimental data of model for bifurcation angle of 60 ̊ Main Channel Q ( \({ m}^{3}/sec\) ) Ratio of q 1 / q 2 Ratio of s 1 / s 2 d = 0.190mm d = 0.250mm d = 0.275mm d = 0.190mm d = 0.250mm d = 0.275mm 0.002 1.2016 1.1235 1.1890 0.9926 0.9896 0.9615 0.004 1.1073 1.1036 1.0842 1.0434 0.9969 0.9971 0.006 0.9980 0.9810 0.9829 1.1073 1.1044 1.0903 0.008 0.9472 0.9630 0.9378 1.2837 1.2045 1.1926 0.010 0.9008 0.8885 0.8528 1.3105 1.2966 1.2396 The model experimented with sediment size of 0.190, 0.250, and 0.275 mm shows, with increasing sediment particle size reduces discharge ratio values i.e., the Old Kasai branch receives less discharge when larger particle size is used in the experiment. A possible explanation could be that for a given discharge the larger particle size silting up inside the sharp bend of Old Kasai branch narrows the flow width and also because of sharp bend more resistance offers which actually restrict the flow. The large sized sediment particle comparatively required more tractive force to move from its position for a given discharge, so when Old Kasai branch receive less discharge for increased value of sediment size the transport ratio also reduces with the increased sediment particle size. Figure 3 (a), (b), &(c) show a graph plotted with the data sets of q 1 / q 2 and s 1 / s 2 for the corresponding discharges of 0.002, 0.004, 0.006, 0.008 and 0.010 cumec shows that the discharge ratio gradually declines while the sediment discharge ratio increases along with the increasing flow and the plotted lines are intersecting each other, indicating that there is an optimum discharge for which the ratios become equal. The present physical model study corresponding to the discharge at which the distribution of flow and sediment become approximately equal is found out to be 0.006 cumec (corresponding proto discharge of 1200 cumec) for the bifurcation angle of 37 ̊, 45 ̊ and 60 ̊. The relation between sediment transport ratio s 1 / s 2 and the angle of bifurcation is presented in Fig. 3 (d) for a specific discharge in main channel of 0.006 cumec. It shows that s 1 /s 2 ratio increases as bifurcation angle increases and also the increasing particle size carries higher s 1 / s 2 ratio. The range of bifurcation angle is limited in this model study that’s why the critical angle for which the sediment transport ratio ( s 1 / s 2 ) become maximum can’t determine accurately. The upstream section of Kangsabati river have a curvature causes the flow deviate from its axial flow, which led to the development of a secondary current that predominated at high discharge and directed towards the Old Kasai branch, as shown in Fig. 4 (a). This increased the s 1 /s 2 ratio at high discharge, causing the discharge ratio ( q 1 /q 2 ) and sediment discharge ratio ( s 1 /s 2 ) to have an inverse relationship. Experimentally it has been observed that the transported sediment in Old Kasai branch get deposited inside the bend, forming sand-bar as shown in Fig. 4 (b). The width and height of bar dependent on the water level, the bar height proportionally increases with water level. The bar width become wider ( \({w}_{b}\) ) at low discharge resulting the flow width at bend constricted, when at high discharge, a strong secondary current extending its effect in Old Kasai branch eroding edges of bars in bend resulting narrow sized bar. Influence of bifurcation angle The model experiment performed to understand how bifurcation angle, input water discharge and sediment grain size effect the partitioning of sediment and water into downstream bifurcations. The relation between the sediment transport ratio ( s 1 /s 2 ) and the angle of diversion for the discharge ratio of ( q 1 /q 2 ) being equal to 1 is presented in Fig. 3 (d) for three different sediment sizes of 0.190, 0.250, and 0.275mm. The amount of attracted sediment into the bifurcating branches is smallest for the channel with a bifurcation angle of 37 ̊, and highest for the bifurcation channel with an angle of 60 ̊ in the present study. The distribution of bed load is dependent on the shape of the bifurcation and sediment size. (Ksi\każek and Meijer 2011 )previous investigator had done a numerical model for the bifurcation angle of 0 to 135 degree with discharge ratio of 0.5 with bed load size of 0.15 mm. The model experimental data has been compared with (Ksi\każek and Meijer 2011 ) model data, and a good conformity is found with the result presented in Fig. 5 . Conclusion This experimental study has been done with three sets of bifurcation angle (37 ̊, 45 ̊ and 60 ̊), different grain size (0.190, 0.250, and 0.275 mm) and varying discharge (0.002, 0.004, 0.006, 0.008, and 0.010 cumec) to examine the effect of discharge and sediment distribution in the downstream bifurcated channel. A set of data collected during experiment and with the observed data the following conclusions are drawn: The experimental data presented in table. 1 to 3 shows that when the discharge in the main channel increases, the discharge ratio q 1 /q 2 decreases and the value of the sediment discharge ratio increases. Similar relationship builds when particle size increases. So, there is an inverse relationship between discharge ratio and sediment discharge ratio. Based on experimental findings, one possible explanation might be that the upstream section of Kangsabati river have a curvature causes the flow deviate from its axial flow, which led to the development of a secondary current that predominated at high discharge and directed towards the Old Kasai branch, as shown in Fig. 4 (a). This increased the ( s 1 /s 2 ) ratio at high discharge, causing the discharge ratio ( q 1 /q 2 ) and sediment discharge ratio ( s 1 /s 2 ) to have an inverse relationship. Tables 1 to 3 show that with increasing bifurcation angle (up to 60 ̊ in the present study), the large-sized sediment particle cannot follow the bending flow lines for the corresponding discharges, resulting in ( s 1 /s 2 ) ratio decline except for a few cases. Figure 3 (d) clearly shows the sensitivity of sediment ratio with varying particle size (0.190mm, 0.250mm, and 0.275mm) for the different bifurcation angle. The present physical model study determines that corresponding discharge is 0.006 cumec for which the ratios ( q 1 /q 2 & s 1 /s 2 ) become approximately one for the bifurcation angle of 37 ̊, 45 ̊ and 60 ̊ (table no 1 to 3). So, it may be concluded that the distribution of sediment and discharge in a bifurcated channel are strongly dependent on upstream discharge. Abbreviations The following symbols are used in this technical note: \({q}_{0}\) , \({q}_{1},\) \({q}_{2}\) =Discharge in main branches and bifurcated branches respectively; \({r}_{1}\) , \({r}_{2}\) = Radius of curvature for branches old kasai and new kasai respectively; \({s}_{0}\) , \({s}_{1},\) \({s}_{2}\) =Sediment transport in main branches and bifurcated branches for a given cross-section in kg/hr; \({w}_{b}\) = Width of bar formation and θ = Nose angle. Declarations Conflict of interest The Authors declare that they have no known completing financial interests or personal relationships that could have appeared to influence the work reported in this paper. Funding No funding was obtained for this study Author Contribution All authors contributed to the study, conception, and design. Methodology, Customizing experimental set-up, data acquisition, and writing the original draft were performed by Amit Das. Supervision, writing- review, and editing were performed by Dr. Bibhas chandra Barman and Dr. Nityananda Nandi. Acknowledgement The authors acknowledge the full cooperation of the staffs of Haringhata Central Laboratory (HCl), River Research Institute (RRI), West Bengal (WB), India. Data Availability Not applicable References Bulle, H. (1926). Investigations on the trapping of bed-load in branching rivers. VD1-Verlag, Forschungsarbeit auf dem Gebiets des Ing. Wesens, Berlin , (283). Das, A., Barman, B. C., & Nandi, N. (2022). 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Alternate bars and meandering: Free, forced and mixed interactions, 12 , 267–320. https://doi.org/10.1029/wm012p0267 Sloff, C. J., Bernabè, M., & Baur, T. (2003). On the stability of the Pannerdense Kop river bifurcation. In IAHR Symposium River, Coastal and Estuarine Morphodynamics, Barcelona (pp. 1001–1011). Sulaiman, S. O., Al-Ansari, N., Shahadha, A., Ismaeel, R., & Mohammad, S. (2021). Evaluation of sediment transport empirical equations: case study of the Euphrates River West Iraq. Arabian Journal of Geosciences , 14 (10). https://doi.org/10.1007/s12517-021-07177-1 Vanoni, V. A. (2006). Sedimentation engineering . Wang, Z. B., De Vries, M., Fokkink, R. J., & Langerak, A. (1995). Stabilité des bifurcations de rivières dans des modèles morphodynamiques filaires. Journal of Hydraulic Research , 33 (6), 739–750. https://doi.org/10.1080/00221689509498549 WAPCOS Ltd, Master plan and DPR for Ghatal Area. (March 2009). Draft Final Report, Vol. I. 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Also discoverable on Platform About Our Team In Review Editorial Policies Advisory Board Help Center Resources Author Services Accessibility API Access RSS feed Manage Cookie Preferences © Research Square 2026 | ISSN 2693-5015 (online) Privacy Policy Terms of Service Do Not Sell My Personal Information {"props":{"pageProps":{"initialData":{"identity":"rs-3909326","acceptedTermsAndConditions":true,"allowDirectSubmit":true,"archivedVersions":[],"articleType":"Research Article","associatedPublications":[],"authors":[{"id":289024834,"identity":"8785c682-a4bd-4dd3-b444-7adad64a660b","order_by":0,"name":"Amit Das","email":"data:image/png;base64,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","orcid":"","institution":"Indian Institute of Engineering Science and Technology, Shibpur","correspondingAuthor":true,"prefix":"","firstName":"Amit","middleName":"","lastName":"Das","suffix":""},{"id":289024835,"identity":"c96d1492-742a-45d4-aec4-ae885dfd47ef","order_by":1,"name":"Bibhas Chandra Barman","email":"","orcid":"","institution":"River Research Institute","correspondingAuthor":false,"prefix":"","firstName":"Bibhas","middleName":"Chandra","lastName":"Barman","suffix":""},{"id":289024836,"identity":"ae01843a-94c6-45cb-96d1-0a5c37fdab74","order_by":2,"name":"Nityananda Nandi","email":"","orcid":"","institution":"Indian Institute of Engineering Science and Technology, Shibpur","correspondingAuthor":false,"prefix":"","firstName":"Nityananda","middleName":"","lastName":"Nandi","suffix":""}],"badges":[],"createdAt":"2024-01-29 18:19:45","currentVersionCode":1,"declarations":"","doi":"10.21203/rs.3.rs-3909326/v1","doiUrl":"https://doi.org/10.21203/rs.3.rs-3909326/v1","draftVersion":[],"editorialEvents":[],"editorialNote":"","failedWorkflow":false,"files":[{"id":54585819,"identity":"8463a0a3-9ba2-4286-8327-6c2b90301fb6","added_by":"auto","created_at":"2024-04-12 15:43:17","extension":"jpg","order_by":1,"title":"Figure 1","display":"","copyAsset":false,"role":"figure","size":137961,"visible":true,"origin":"","legend":"\u003cp\u003eA schematic of the experimental set-up (a) Satellite image of kangsabati river bifurcation at Kapastikri, (b) General lay-out plan of the model set-up, (c) Physical model set-up at RRI, (d) Arrangement of sediment supply.\u003c/p\u003e","description":"","filename":"1.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3909326/v1/aee0a40aa250919af05e9583.jpg"},{"id":54585818,"identity":"e89ad36a-086c-4fde-9847-3e2484d56362","added_by":"auto","created_at":"2024-04-12 15:43:16","extension":"jpg","order_by":2,"title":"Figure 2","display":"","copyAsset":false,"role":"figure","size":106319,"visible":true,"origin":"","legend":"\u003cp\u003eMeasuring and regulating instrument in the model experiment (a) V-notch arrangement, (b) Pointer scale arrangements to measure gauge height, (c) Tail end gate to simulate gauge height, (d) Oven drier to dry collected sediment.\u003c/p\u003e","description":"","filename":"2.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3909326/v1/db76092c762cc7e5b02a41fb.jpg"},{"id":54585826,"identity":"f67cf15a-c332-4c28-8972-c65295602f56","added_by":"auto","created_at":"2024-04-12 15:43:23","extension":"jpg","order_by":3,"title":"Figure 3","display":"","copyAsset":false,"role":"figure","size":82696,"visible":true,"origin":"","legend":"\u003cp\u003eDischarge vs ratio of \u003cem\u003e(q\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) \u0026amp; (s\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e) \u003c/em\u003efor bifurcation angle (a) 37 degree, (b) 45 degree, (c) 60 degree, and (d) relation of (\u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) ratio with angle of bifurcation for (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e=1)\u003c/p\u003e","description":"","filename":"3.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3909326/v1/8c6970d5fbb2e382cd8961d5.jpg"},{"id":54585825,"identity":"019517f6-c542-4eb7-8fb4-f1526ed7e596","added_by":"auto","created_at":"2024-04-12 15:43:22","extension":"jpg","order_by":4,"title":"Figure 4","display":"","copyAsset":false,"role":"figure","size":131621,"visible":true,"origin":"","legend":"\u003cp\u003eObservation of (a)Strong secondary current, (b) Bar formation during experiment\u003c/p\u003e","description":"","filename":"4.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3909326/v1/f58411f2f6310bc43934667d.jpg"},{"id":54585824,"identity":"aabd1b9e-f5bf-4570-be2d-7fff9426de14","added_by":"auto","created_at":"2024-04-12 15:43:22","extension":"jpg","order_by":5,"title":"Figure 5","display":"","copyAsset":false,"role":"figure","size":28691,"visible":true,"origin":"","legend":"\u003cp\u003eComparison of bed load ratio s\u003csub\u003e1\u003c/sub\u003e/s\u003csub\u003e2\u003c/sub\u003e as a function of bifurcation angle for discharge ratio (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u0026nbsp;\u003c/em\u003e\u003c/sub\u003e=1)\u003c/p\u003e","description":"","filename":"5.jpg","url":"https://assets-eu.researchsquare.com/files/rs-3909326/v1/9563bf2b46cc14f8e9e6d1c7.jpg"},{"id":54586375,"identity":"ccd58a1f-d60e-439d-b852-d18e07a1e8a7","added_by":"auto","created_at":"2024-04-12 15:51:30","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":710616,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-3909326/v1/1d293f2b-464a-40e2-9d4a-47de018d338c.pdf"}],"financialInterests":"No competing interests reported.","formattedTitle":"An experimental study to determine the effects of particle size and bifurcation angle on the distribution of flow and sediment transport parameters in a bifurcated channel.","fulltext":[{"header":"Introduction","content":"\u003cp\u003eThe journey of a river from its source in the mountains to the sea involves a complex interplay of physical processes (such as meandering, bifurcation, bar formation etc.), and the river undergoes several changes in its characteristics and behaviours. The specifics of a river bifurcation are dependent upon several elements, including the river's flow rate, the amounts of sediments present, the land's slope, and the existence of vegetation or other impediments, whether man-made or natural. Generally speaking, river bifurcations are dynamic systems that are subject to alter over time due to both natural and manmade influences. At a river bifurcation, a change in the distribution of sediment often leads to aggradation in one of the downstream branches. Consequently, the bifurcation structure will become unstable when the water discharge through this branch decreases and the water discharge through the other branch increases at the same time. This has an impact on the possibility of floods in one branch, water scarcity and poor water quality (Faulstich et al. \u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e2023\u003c/span\u003e; Grzywna and Sender \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e2021\u003c/span\u003e) in another branch, navigability, as well as the availability of water for vegetational, agricultural and human needs. A good understanding of flow and sediment distribution process is thus crucial for creating diverse habitats for wildlife and providing opportunities of human use such as irrigation, transportation, and sharing of water.\u003c/p\u003e \u003cp\u003eFlow Bifurcation are typical features of braided rivers, alluvial fans and river deltas, and strongly determine the stability of a river system. Different aspects that influence the flow and sediment distribution in a bifurcated channel and their stability. Stability of bifurcation is one of an important aspect, (Wang et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1995\u003c/span\u003e) theoretically investigated the stability of the configuration weather both branch open or one of the branches get closed. (Miori et al. \u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) discusses the equilibrium configurations of a bifurcation in a gravel bed channel with erodible banks which shows that stable equilibrium solutions are characterized by a strongly unbalanced partition of water and sediment discharges in the two branches. River deltas typically contain networks of bifurcating channels and the complexity of the bifurcation problem lies in the determination of the distribution of sediments at the downstream branches (Hoitink et al. \u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e2020\u003c/span\u003e; Das et al. \u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2022\u003c/span\u003e) proposed an empirical nodal point relationship to estimate the flow and sediment distribution for a channel bifurcation (Melman 2011) discusses the flow and sediment distribution in a bifurcated channel, specifically focusing on the Monta\u0026ntilde;o - Murindo bifurcation of the Atrato river in Colombia, mentions that the division of flow and sediments is influenced by local geometrical phenomena, such as the angle of offtake and river bends. A good understanding of flow and sediment distribution process is thus crucial for creating diverse habitats for wildlife and provide opportunities of human use such as irrigation, transportation, and hydropower generation.\u003c/p\u003e \u003cp\u003eSeveral experimental studies have investigated the angle at which bifurcations develop, shedding light on their sediment distribution dynamics. Researchers such as (Riad \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e1961\u003c/span\u003e; Den Dekker and Van Voorthuizen \u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e1994\u003c/span\u003e; Islam \u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e2000\u003c/span\u003e), and others have conducted physical model studies in this regard. These studies generally reveal that sediment distribution correlates more than linearly with discharge distribution; a wider diverting angle tends to attract more sediment, particularly bed load, while suspended sediment distribution tends to align more closely with discharge distribution. Early experiments by (Bulle \u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1926\u003c/span\u003e) and subsequent studies by (Seminara and Tubino \u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e2011\u003c/span\u003e; Rezapour et al. \u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e2009\u003c/span\u003e) confirm this tendency for sediment to preferentially deviate toward the lateral branch, often disproportionately to water discharge distribution. (Islam et al. \u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) conducted experiments to validate the nodal point relation proposed by (Wang et al. \u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e1995\u003c/span\u003e) finding that the parameter k in the relation depends significantly on the bifurcation angle. Furthermore, (Herrero et al. \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e2015\u003c/span\u003e) conducted experiments with 900 channel diversions, emphasizing the interconnected nature of bed topography evolution, flow characteristics, and sediment distribution at fluvial diversions. (Vanoni \u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e2006\u003c/span\u003e) suggested that there is no universally optimal bifurcation angle for channel diversions, as it varies based on factors such as discharge ratio in the main stream and intake geometry at the bifurcation point, including the radius of curvature\u003c/p\u003e \u003cp\u003eSome studies have been carried out based on real bifurcations. (Sloff et al. \u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e2003\u003c/span\u003e) report the results of a numerical modelling and experimental analysis on sediment behaviours in Pannerdense bifurcation. (Frings and Kleinhans \u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e2008\u003c/span\u003e) carried out an analysis on data of three bifurcations in the Rhine River system: i.e. Pannerdense Kop, Ijssel Kop and Merwede Kop. The location of the bifurcation in relation to the planimetric\u003c/p\u003e \u003cp\u003eshape of the river can play an important role in sediment distribution amongst the downstream branches. The bend sorting process that takes place in a river bend, distributing coarser sediment in the outer part of the bend and finer sediment in the inner part, causes that when a bifurcation is placed in a river bend, the outer branch receives less sediment than the inner one due to supply-limited conditions.\u003c/p\u003e \u003cp\u003eThe present study has been carried out based on actual field bifurcation of river Kangsabati, originated from Chota-Nagpur plateau in Purulia district enters Paschim Midnapore in Binpur area, West Bengal, which then bifurcates at Kapastikri, about 75 km downstream of Kangsabati reservoir. This bifurcation in the river Kangsabati is found to cause severe problems during high flood discharge in the adjoining areas of Ghatal subdivision. It has been observed that the major portion of Kangsabati water passes through Old Kasai and remaining water passes through New Kasai in case of low and moderate discharges. The share through the New Kasai increases with the increase of discharges. At very high discharges (greater than 1200 cumec), the New Kasai share raises up to nearly 45%. This seems to be due to inherent morphology at the junction point at Kapastikri which very often causes flood in adjoining Ghatal Subdivision and Panskura during high discharge. It is, therefore, required to bring this bifurcation to a condition when the flow in the daughter channels will not cause any inundation problem. So, to study the sharing of discharges and bed-load transport, model tests have been conducted on a fixed-bed model at River Research Institute (RRI), West Bengal (WB), India. Further, an experimental study has been conducted with different sets of bifurcation angle, roundness of bifurcation point, varying upstream discharge, varying sediment particle size (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({d}_{50}\\)\u003c/span\u003e\u003c/span\u003e) to see the distribution of discharge and sediment over the downstream branches with the same longitudinal slope. A comprehensive analysis has been done based on data collected from the physical model to find an optimal solution in which discharge and sediment get more or less equally distributed over the bifurcated channel for a given upstream discharge. This may help the nearly equal sharing of water during moderate and high flood discharges so that the undesirable discharge doesn\u0026rsquo;t pass through a particular channel. In this study the most vulnerable river is Old Kasai, a branch of the Kangsabati river.\u003c/p\u003e"},{"header":"Materials and Methods","content":"\u003cdiv id=\"Sec3\" class=\"Section2\"\u003e \u003ch2\u003ePhysical model set-up\u003c/h2\u003e \u003cp\u003eA general layout of the physical model set-up has been shown in Fig.\u0026nbsp;1(b) is comprised of three branches: a main branch (Kangsabati) which bifurcates into two branches; Old Kasai and New Kasai. The angle of bifurcation of Old Kasai and New Kasai are \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\theta }_{1}\\)\u003c/span\u003e\u003c/span\u003e\u0026amp; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\theta }_{2}\\)\u003c/span\u003e\u003c/span\u003e, while the radius of curvature of the corresponding branches are \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({r}_{1}\\)\u003c/span\u003e\u003c/span\u003e \u0026amp; \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({r}_{2}\\)\u003c/span\u003e\u003c/span\u003e. A scaled physical model simulating the bifurcation of the Kangsabati river has been conducted at the River Research Institute (RRI), West Bengal, Mohanpur, Nadia, India, considering the horizontal and vertical scale ratios of 1:350 and 1:70, respectively Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e(c). So, the distortion factor is 5. The discharge ratio of prototype and model is 1: 0.000005. The maximum discharge of river Kangsabati is 4600 cumecs in 100 years return period (WAPCOS Ltd. 2009). The slope of the main Kangsabati is 0.000246 (m/m) and the slope of bifurcated branches i.e., Old Kasai is 0.000875 (m/m) and New Kasai is 0.0015 (m/m) (WAPCOS Ltd. 2009). The diversion angle of Old Kasai is 23\u0026ordm; and New Kasai is 14\u0026ordm; from the line of symmetry, ratio of their angle becomes 23:14. The radius of curvature for Old Kasai and New Kasai is 0.56 m and 0.777 m respectively.\u003c/p\u003e \u003cp\u003e Furthermore, with this existing geometry additional two sets of bifurcation angle have been customised i.e., 45 ̊ and 60 ̊ with the ratio of bifurcation angle 23:14. The present study demonstrate the effects of bifurcation angle on the flow and sediment distribution over the bifurcated branches\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec4\" class=\"Section2\"\u003e \u003ch2\u003eSimulation of hydraulic conditions\u003c/h2\u003e \u003cp\u003eThe model experiments simulating bifurcation at Kapastikri in river Kangsabati have used the data of hydraulic observation (RRI, I\u0026amp;W Govt. of West Bengal, India) from 14th August 2012 to 31st October 2012 and 26th July to 8th November 2013. The discharge ratio of prototype and model is 1:0.000005. The model has been run with a range of discharges, including low, moderate, and high, with the selected discharges being 0.002, 0.004, 0.006, 0.008 and 0.010\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({m}^{3}/sec\\)\u003c/span\u003e\u003c/span\u003e. Initially, water pumped from a well, it was first passed through a stilling chamber to minimise turbulence intensity, which allowed the flow to become natural before it reached the actual model setup. The boundary condition for the physical model is done with a rating curve obtained from the relationship of discharge vs gauge height. The scaled gauge height at the boundary is maintained by controlling the opening of the tail end gate as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e(c). The scaled gauge height in the main channel (Kangsabati), left channel (Old Kasai) and right channel (New Kasai) measured separately by pointer scale arrangements as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e(b) for a given discharge. The experiment performed multiple equilibrium condition runs to analyse how the water discharge and sediment transport rate varied between the two bifurcations for changing flow and sediment size conditions.\u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec5\" class=\"Section2\"\u003e \u003ch2\u003eMethods of experiment\u003c/h2\u003e \u003cp\u003eThe physical model has been done with the primary goal to determine how discharge and sediments were distributed at a channel bifurcation. Analysis of field samples of river Kangsabati have been done and sediments indicated a prototype grain size of 0.275 and 0.285 mm for an average velocity of 0.55 and 1.04 m/sec. For scaled models, choosing the sediment size is getting more challenging, we can\u0026rsquo;t simply reduce particle size in accordance with model scale as particle size becomes very small that may cause major changes in cohesiveness qualities, entirely changing the sediment transport mechanics between the model and prototype. A quantitative analysis has been done in terms of sediment transport in the present study. Three different sizes of sediment of different densities were used to study the phenomenon. The sediment transport consists of bed load only. The mean diameters (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({d}_{50}\\)\u003c/span\u003e\u003c/span\u003e) of the sediments used in the experiments were 0.190, 0.250 and 0.275 mm. For each sediment size, five upstream discharges of 0.002, 0.004, 0.006, 0.008 and 0.010\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({m}^{3}/sec\\)\u003c/span\u003e\u003c/span\u003e have been used. The v-notch arrangement as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e2\u003c/span\u003e (a) is used to measure the flow rate. The first step is to prepare the model with selected sediment and then run the model with the selected discharges. The upstream sediment load supplied during an experiment for a particular discharge has been determined from Engelund\u0026ndash;Hansen sediment transport formula (Sulaiman et al. \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e2021\u003c/span\u003e)\u003c/p\u003e \u003cp\u003eSediment transport capacity is calculated as follows:\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\({q}_{t}=\\)\u003c/span\u003e \u003c/span\u003e0.05\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({\\gamma }_{s}{V}^{2}{\\left[\\frac{{d}_{50}}{\\left(\\frac{{\\gamma }_{s}}{\\gamma }-1\\right)}\\right]}^{\\frac{1}{2}}{\\left[\\frac{\\tau }{\\left(\\frac{{\\gamma }_{s}}{\\gamma }-1\\right){d}_{50}}\\right]}^{\\frac{3}{2}}\\)\u003c/span\u003e\u003c/span\u003e Eq-(1)\u003c/p\u003e \u003cp\u003eWhere,\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\({q}_{t}=\\)\u003c/span\u003e \u003c/span\u003e Sediment load discharge in kg/hr;\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\({\\gamma }_{s}\\)\u003c/span\u003e \u003c/span\u003e= Unit weight of sediment in kN/\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({m}^{3}\\)\u003c/span\u003e\u003c/span\u003e;\u003c/p\u003e \u003cp\u003eV\u0026thinsp;=\u0026thinsp;Mean velocity of the channel in m/sec;\u003c/p\u003e \u003cp\u003eg\u0026thinsp;=\u0026thinsp;Gravitational acceleration in m/\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({sec}^{2}\\)\u003c/span\u003e\u003c/span\u003e;\u003c/p\u003e \u003cp\u003e⍴= Density of the water in kg/\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({m}^{3}\\)\u003c/span\u003e\u003c/span\u003e;\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\(\\tau =\\)\u003c/span\u003e \u003c/span\u003e Bed shear stress in N/\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({m}^{2}\\)\u003c/span\u003e\u003c/span\u003e;\u003c/p\u003e \u003cp\u003e \u003cspan class=\"InlineEquation\"\u003e \u003cspan class=\"mathinline\"\u003e\\({d}_{50}\\)\u003c/span\u003e \u003c/span\u003e= Diameter of sediment particle in m;\u003c/p\u003e \u003cp\u003eFor the upstream discharges of 0.002, 0.004, 0.006, 0.008 and 0.010\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({m}^{3}/sec\\)\u003c/span\u003e\u003c/span\u003e, the average sediment loads (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({s}_{0})\\)\u003c/span\u003e\u003c/span\u003e were 1.5, 3, 4.5, 6 and 8.5 kg/hr respectively. The amounts of sediments estimated by using the Engelund\u0026ndash;Hansen sediment transport formula corresponded very closely to the above sediment loads, i.e., the sediment transport in the main channel followed by Eq.\u0026nbsp;(1). A sand feeder provides the supply of sediments placed at the main branch in such a distance so that the sediments supplied from the sand feeder are uniformly distributed before reaching the bifurcation point. The sediment falls from the sediment feeder into the wooden structure Fig.\u0026nbsp;1(d), which distributes the sediment uniformly over the main channel width.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe experiment performed multiple equilibrium condition runs (i.e., when the discharges in the downstream branches were constant) to analyse how the water discharge and sediment transport rate varied between the two bifurcated branches for three different bifurcation angles by changing flow and sediment size conditions. The experimental run has been done with five different upstream discharge values as mentioned above and held other parameters i.e., bifurcation angle and sediment size constant, these two parameters isolated systematically by individually varying them across the experimental runs. Total of 45 experimental run was conducted with the combination of these three variables i.e., bifurcation angle, sediment size, and upstream discharge. Guage height was measured during each experimental run and the individual discharges of branches (New Kasai and Old Kasai) were calculated using a calibrating stage-discharge chart for the model. Ripples were formed in the channel bed at the end of the run. The sediments were transported through the bifurcated branch trapped in the sand traps which were located in the downstream section of each bifurcated branches. The deposited sediment in the sand trap was collected, oven dried for 24 hours and weighted. The sediment transport rate in the downstream bifurcated branches calculated knowing the total quantity of sediment collected from sand traps over the duration of experimental run.\u003c/p\u003e \u003c/div\u003e"},{"header":"Results and discussion","content":"\u003cdiv id=\"Sec7\" class=\"Section2\"\u003e \u003ch2\u003eInfluence of particle size and upstream discharge\u003c/h2\u003e \u003cp\u003eThe model set-up experimented with different sets of bifurcation angle and different grain size, to study the effect of discharge and sediment distribution over the downstream branches. The quantity of discharge distributed in each bifurcated branches i.e., for Old Kasai branch is \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e and for New Kasai branch is \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e, measured for a specific discharge \u003cem\u003eq\u003c/em\u003e in the main channel. Similarly, the quantity of distributed sediment in the bifurcated branches i.e., for Old Kasai branch is \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e and for New Kasai branch is \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e, measured for the corresponding discharges. The discharge ratio \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e and sediment discharge ratio \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e is presented in Table \u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e to \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e for the corresponding discharge (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({q}_{0}\\)\u003c/span\u003e\u003c/span\u003e) of 0.002, 0.004, 0.006, 0.008, 0.010 cumec. It has been observed from the table. 1 to 3 that when the discharge in the main channel increases, the discharge ratio \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e decreases and the value of the sediment discharge ratio increases. So, it may be concluded that the discharge ratio and sediment discharge ratio are not proportionally related.\u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eExperimental data of model for bifurcation angle of 37 ̊\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMain Channel \u003cem\u003eQ\u003c/em\u003e (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({ m}^{3}/sec\\)\u003c/span\u003e\u003c/span\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eRatio of \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e \u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eRatio of \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.190mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.250mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.275mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.190mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.250mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.275mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.3767\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.3138\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.2468\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.8926\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.8701\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.8615\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.2474\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.2044\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.1897\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9237\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9069\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.8843\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.0061\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.9904\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9891\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.0092\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9872\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.9554\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.9928\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.9879\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9686\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.1046\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.1039\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.9941\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.9899\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.9669\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9599\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.3523\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.3006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.2990\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eExperimental data of model for bifurcation angle of 45 ̊\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMain Channel \u003cem\u003eQ\u003c/em\u003e (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({ m}^{3}/sec\\)\u003c/span\u003e\u003c/span\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eRatio of \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/ q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eRatio of \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/ s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.190mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.250mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.275mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.190mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.250mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.275mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.2767\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.1549\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.1129\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9615\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.8726\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.1733\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.0236\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.0164\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9843\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9689\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.9297\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.9989\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.9893\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9878\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.1038\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.0104\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.9937\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.9750\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.9686\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9578\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.1924\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.1405\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.1046\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.9187\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.9085\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.8828\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.3786\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.2649\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.2332\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003e \u003cdiv class=\"gridtable\"\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e \u003ccaption language=\"En\"\u003e \u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e \u003cdiv class=\"CaptionContent\"\u003e \u003cp\u003eExperimental data of model for bifurcation angle of 60 ̊\u003c/p\u003e \u003c/div\u003e \u003c/caption\u003e \u003ccolgroup cols=\"7\"\u003e \u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c6\" colnum=\"6\"\u003e\u003c/div\u003e \u003cdiv align=\"char\" char=\".\" class=\"colspec\" colname=\"c7\" colnum=\"7\"\u003e\u003c/div\u003e \u003cthead\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c1\" morerows=\"1\" rowspan=\"2\"\u003e \u003cp\u003eMain Channel \u003cem\u003eQ\u003c/em\u003e (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({ m}^{3}/sec\\)\u003c/span\u003e\u003c/span\u003e)\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c4\" namest=\"c2\"\u003e \u003cp\u003eRatio of \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/ q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colspan=\"3\" nameend=\"c7\" namest=\"c5\"\u003e \u003cp\u003eRatio of \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/ s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003ctr\u003e \u003cth align=\"left\" colname=\"c2\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.190mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c3\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.250mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c4\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.275mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c5\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.190mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c6\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.250mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003cth align=\"left\" colname=\"c7\"\u003e \u003cp\u003e\u003cem\u003ed\u0026thinsp;=\u0026thinsp;0.275mm\u003c/em\u003e\u003c/p\u003e \u003c/th\u003e \u003c/tr\u003e \u003c/thead\u003e \u003ctbody\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.002\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.2016\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.1235\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.1890\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e0.9926\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9896\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.9615\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.004\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e1.1073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e1.1036\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e1.0842\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.0434\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e0.9969\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e0.9971\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.006\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.9980\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.9810\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9829\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.1073\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.1044\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.0903\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.9472\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.9630\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.9378\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.2837\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.2045\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.1926\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003ctr\u003e \u003ctd align=\"left\" colname=\"c1\"\u003e \u003cp\u003e0.010\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c2\"\u003e \u003cp\u003e0.9008\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c3\"\u003e \u003cp\u003e0.8885\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c4\"\u003e \u003cp\u003e0.8528\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c5\"\u003e \u003cp\u003e1.3105\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c6\"\u003e \u003cp\u003e1.2966\u003c/p\u003e \u003c/td\u003e \u003ctd align=\"char\" char=\".\" colname=\"c7\"\u003e \u003cp\u003e1.2396\u003c/p\u003e \u003c/td\u003e \u003c/tr\u003e \u003c/tbody\u003e \u003c/colgroup\u003e \u003c/table\u003e\u003c/div\u003e \u003c/p\u003e \u003cp\u003eThe model experimented with sediment size of 0.190, 0.250, and 0.275 mm shows, with increasing sediment particle size reduces discharge ratio values i.e., the Old Kasai branch receives less discharge when larger particle size is used in the experiment. A possible explanation could be that for a given discharge the larger particle size silting up inside the sharp bend of Old Kasai branch narrows the flow width and also because of sharp bend more resistance offers which actually restrict the flow. The large sized sediment particle comparatively required more tractive force to move from its position for a given discharge, so when Old Kasai branch receive less discharge for increased value of sediment size the transport ratio also reduces with the increased sediment particle size.\u003c/p\u003e \u003cp\u003eFigure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e (a), (b), \u0026amp;(c) show a graph plotted with the data sets of \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/ q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e and \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/ s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e for the corresponding discharges of 0.002, 0.004, 0.006, 0.008 and 0.010 cumec shows that the discharge ratio gradually declines while the sediment discharge ratio increases along with the increasing flow and the plotted lines are intersecting each other, indicating that there is an optimum discharge for which the ratios become equal. The present physical model study corresponding to the discharge at which the distribution of flow and sediment become approximately equal is found out to be 0.006 cumec (corresponding proto discharge of 1200 cumec) for the bifurcation angle of 37 ̊, 45 ̊ and 60 ̊. The relation between sediment transport ratio \u003cem\u003es\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e/ \u003cem\u003es\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e and the angle of bifurcation is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d) for a specific discharge in main channel of 0.006 cumec. It shows that \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e ratio increases as bifurcation angle increases and also the increasing particle size carries higher \u003cem\u003es\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e/\u003cem\u003es\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e ratio. The range of bifurcation angle is limited in this model study that\u0026rsquo;s why the critical angle for which the sediment transport ratio (\u003cem\u003es\u003c/em\u003e\u003csub\u003e1\u003c/sub\u003e/\u003cem\u003es\u003c/em\u003e\u003csub\u003e2\u003c/sub\u003e) become maximum can\u0026rsquo;t determine accurately.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003cp\u003eThe upstream section of Kangsabati river have a curvature causes the flow deviate from its axial flow, which led to the development of a secondary current that predominated at high discharge and directed towards the Old Kasai branch, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e(a). This increased the \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e ratio at high discharge, causing the discharge ratio (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) and sediment discharge ratio (\u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) to have an inverse relationship. Experimentally it has been observed that the transported sediment in Old Kasai branch get deposited inside the bend, forming sand-bar as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e(b). The width and height of bar dependent on the water level, the bar height proportionally increases with water level. The bar width become wider (\u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({w}_{b}\\)\u003c/span\u003e\u003c/span\u003e) at low discharge resulting the flow width at bend constricted, when at high discharge, a strong secondary current extending its effect in Old Kasai branch eroding edges of bars in bend resulting narrow sized bar.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e \u003cdiv id=\"Sec8\" class=\"Section2\"\u003e \u003ch2\u003eInfluence of bifurcation angle\u003c/h2\u003e \u003cp\u003eThe model experiment performed to understand how bifurcation angle, input water discharge and sediment grain size effect the partitioning of sediment and water into downstream bifurcations. The relation between the sediment transport ratio (\u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) and the angle of diversion for the discharge ratio of (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) being equal to 1 is presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d) for three different sediment sizes of 0.190, 0.250, and 0.275mm. The amount of attracted sediment into the bifurcating branches is smallest for the channel with a bifurcation angle of 37 ̊, and highest for the bifurcation channel with an angle of 60 ̊ in the present study. The distribution of bed load is dependent on the shape of the bifurcation and sediment size. (Ksi\\każek and Meijer \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2011\u003c/span\u003e)previous investigator had done a numerical model for the bifurcation angle of 0 to 135 degree with discharge ratio of 0.5 with bed load size of 0.15 mm. The model experimental data has been compared with (Ksi\\każek and Meijer \u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e2011\u003c/span\u003e) model data, and a good conformity is found with the result presented in Fig.\u0026nbsp;\u003cspan refid=\"Fig4\" class=\"InternalRef\"\u003e5\u003c/span\u003e.\u003c/p\u003e \u003cp\u003e \u003c/p\u003e \u003c/div\u003e"},{"header":"Conclusion","content":"\u003cp\u003eThis experimental study has been done with three sets of bifurcation angle (37 ̊, 45 ̊ and 60 ̊), different grain size (0.190, 0.250, and 0.275 mm) and varying discharge (0.002, 0.004, 0.006, 0.008, and 0.010 cumec) to examine the effect of discharge and sediment distribution in the downstream bifurcated channel. A set of data collected during experiment and with the observed data the following conclusions are drawn:\u003c/p\u003e \u003cp\u003e \u003cul\u003e \u003cli\u003e \u003cp\u003eThe experimental data presented in table. 1 to 3 shows that when the discharge in the main channel increases, the discharge ratio \u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e decreases and the value of the sediment discharge ratio increases. Similar relationship builds when particle size increases. So, there is an inverse relationship between discharge ratio and sediment discharge ratio. Based on experimental findings, one possible explanation might be that the upstream section of Kangsabati river have a curvature causes the flow deviate from its axial flow, which led to the development of a secondary current that predominated at high discharge and directed towards the Old Kasai branch, as shown in Fig.\u0026nbsp;\u003cspan refid=\"Fig3\" class=\"InternalRef\"\u003e4\u003c/span\u003e (a). This increased the (\u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) ratio at high discharge, causing the discharge ratio (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) and sediment discharge ratio (\u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) to have an inverse relationship.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eTables\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e to \u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e show that with increasing bifurcation angle (up to 60 ̊ in the present study), the large-sized sediment particle cannot follow the bending flow lines for the corresponding discharges, resulting in (\u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) ratio decline except for a few cases. Figure\u0026nbsp;\u003cspan refid=\"Fig2\" class=\"InternalRef\"\u003e3\u003c/span\u003e(d) clearly shows the sensitivity of sediment ratio with varying particle size (0.190mm, 0.250mm, and 0.275mm) for the different bifurcation angle.\u003c/p\u003e \u003c/li\u003e \u003cli\u003e \u003cp\u003eThe present physical model study determines that corresponding discharge is 0.006 cumec for which the ratios (\u003cem\u003eq\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/q\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e \u0026amp; \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) become approximately one for the bifurcation angle of 37 ̊, 45 ̊ and 60 ̊ (table no 1 to 3). So, it may be concluded that the distribution of sediment and discharge in a bifurcated channel are strongly dependent on upstream discharge.\u003c/p\u003e \u003c/li\u003e \u003c/ul\u003e \u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cp\u003eThe following symbols are used in this technical note:\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u0026nbsp;\u003cspan class=\"mathinline\"\u003e\\({q}_{0}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({q}_{1},\\)\u003c/span\u003e\u003c/span\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({q}_{2}\\)\u003c/span\u003e\u003c/span\u003e =Discharge in main branches and bifurcated branches respectively;\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u0026nbsp;\u003cspan class=\"mathinline\"\u003e\\({r}_{1}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({r}_{2}\\)\u003c/span\u003e\u003c/span\u003e= Radius of curvature for branches old kasai and new kasai respectively;\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u0026nbsp;\u003cspan class=\"mathinline\"\u003e\\({s}_{0}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e, \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({s}_{1},\\)\u003c/span\u003e\u003c/span\u003e \u003cspan class=\"InlineEquation\"\u003e\u003cspan class=\"mathinline\"\u003e\\({s}_{2}\\)\u003c/span\u003e\u003c/span\u003e=Sediment transport in main branches and bifurcated branches for a given cross-section in kg/hr;\u003c/p\u003e\n\u003cp\u003e\u003cspan class=\"InlineEquation\"\u003e\u0026nbsp;\u003cspan class=\"mathinline\"\u003e\\({w}_{b}\\)\u003c/span\u003e\u0026nbsp;\u003c/span\u003e= Width of bar formation and \u0026theta;\u0026thinsp;=\u0026thinsp;Nose angle.\u003c/p\u003e"},{"header":"Declarations","content":"\u003ch2\u003eConflict of interest\u003c/h2\u003e\n\u003cp\u003eThe Authors declare that they have no known completing financial interests or personal relationships that could have appeared to influence the work reported in this paper.\u003c/p\u003e\n\u003ch2\u003eFunding\u003c/h2\u003e\n\u003cp\u003eNo funding was obtained for this study\u003c/p\u003e\n\u003ch2\u003eAuthor Contribution\u003c/h2\u003e\n\u003cp\u003eAll authors contributed to the study, conception, and design. Methodology, Customizing experimental set-up, data acquisition, and writing the original draft were performed by Amit Das. Supervision, writing- review, and editing were performed by Dr. Bibhas chandra Barman and Dr. Nityananda Nandi.\u003c/p\u003e\n\u003ch2\u003eAcknowledgement\u003c/h2\u003e\n\u003cp\u003eThe authors acknowledge the full cooperation of the staffs of Haringhata Central Laboratory (HCl), River Research Institute (RRI), West Bengal (WB), India.\u003c/p\u003e\n\u003ch2\u003eData Availability\u003c/h2\u003e\n\u003cp\u003eNot applicable\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\n\u003cli\u003eBulle, H. (1926). Investigations on the trapping of bed-load in branching rivers. \u003cem\u003eVD1-Verlag, Forschungsarbeit auf dem Gebiets des Ing. Wesens, Berlin\u003c/em\u003e, (283).\u003c/li\u003e\n\u003cli\u003eDas, A., Barman, B. C., \u0026amp; Nandi, N. (2022). 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Water flow and sediment transport in a 90\u0026deg; channel diversion: An experimental study. \u003cem\u003eJournal of Hydraulic Research\u003c/em\u003e, \u003cem\u003e53\u003c/em\u003e(2), 253\u0026ndash;263. https://doi.org/10.1080/00221686.2014.989457\u003c/li\u003e\n\u003cli\u003eHoitink, A. J. F., Nittrouer, J. A., Passalacqua, P., Shaw, J. B., Langendoen, E. J., Huismans, Y., \u0026amp; van Maren, D. S. (2020). Resilience of River Deltas in the Anthropocene. \u003cem\u003eJournal of Geophysical Research: Earth Surface\u003c/em\u003e, \u003cem\u003e125\u003c/em\u003e(3), 1\u0026ndash;36. https://doi.org/10.1029/2019JF005201\u003c/li\u003e\n\u003cli\u003eIslam, G. M. T. (2000). On the distribution of sediments at channel bifurcation. In \u003cem\u003eBuilding Partnerships\u003c/em\u003e (pp. 1\u0026ndash;10).\u003c/li\u003e\n\u003cli\u003eIslam, G. M. T., Kabir, M. R., \u0026amp; Nishat, A. (2006). Nodal Point Relation for the Distribution of Sediments at Channel Bifurcation. \u003cem\u003eJournal of Hydraulic Engineering\u003c/em\u003e, \u003cem\u003e132\u003c/em\u003e(10), 1105\u0026ndash;1109. https://doi.org/10.1061/(asce)0733-9429(2006)132:10(1105)\u003c/li\u003e\n\u003cli\u003eKsi\\każek, L., \u0026amp; Meijer, D. G. (2011). Changes of Sediment Distribution in a Channel Bifurcation--3D Modeling. In \u003cem\u003eExperimental Methods in Hydraulic Research\u003c/em\u003e (pp. 175\u0026ndash;187). Springer.\u003c/li\u003e\n\u003cli\u003eMelman, F. C. R. (Frank). (2011). Navigability at an unstable bifurcation, (August).\u003c/li\u003e\n\u003cli\u003eMiori, S., Repetto, R., \u0026amp; Tubino, M. (2006). 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On the stability of the Pannerdense Kop river bifurcation. In \u003cem\u003eIAHR Symposium River, Coastal and Estuarine Morphodynamics, Barcelona\u003c/em\u003e (pp. 1001\u0026ndash;1011).\u003c/li\u003e\n\u003cli\u003eSulaiman, S. O., Al-Ansari, N., Shahadha, A., Ismaeel, R., \u0026amp; Mohammad, S. (2021). Evaluation of sediment transport empirical equations: case study of the Euphrates River West Iraq. \u003cem\u003eArabian Journal of Geosciences\u003c/em\u003e, \u003cem\u003e14\u003c/em\u003e(10). https://doi.org/10.1007/s12517-021-07177-1\u003c/li\u003e\n\u003cli\u003eVanoni, V. A. (2006). \u003cem\u003eSedimentation engineering\u003c/em\u003e.\u003c/li\u003e\n\u003cli\u003eWang, Z. B., De Vries, M., Fokkink, R. J., \u0026amp; Langerak, A. (1995). Stabilit\u0026eacute; des bifurcations de rivi\u0026egrave;res dans des mod\u0026egrave;les morphodynamiques filaires. \u003cem\u003eJournal of Hydraulic Research\u003c/em\u003e, \u003cem\u003e33\u003c/em\u003e(6), 739\u0026ndash;750. https://doi.org/10.1080/00221689509498549\u003c/li\u003e\n\u003cli\u003eWAPCOS Ltd, Master plan and DPR for Ghatal Area. (March 2009). Draft Final Report, Vol. I.\u003c/li\u003e\n\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":true,"highlight":"","institution":"","isAcceptedByJournal":false,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true},"keywords":"River bifurcation, Sediment transport, Bifurcation angle, Bed-load, Physical model","lastPublishedDoi":"10.21203/rs.3.rs-3909326/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-3909326/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003eFlow and sediment sharing in a bifurcated channel are considered to be a very important issues in river engineering and flood management.\u0026nbsp;The present study has been conducted based on the field bifurcation of the Kangsabati river bifurcates at Kapastikri, about 75 km downstream of Kangsabati reservoir of West Midnapore, West Bengal, India. A scaled physical model simulating bifurcation region was conducted on a fixed-bed model at the Laboratory of River Research Institute (RRI), West Bengal (WB), India. \u0026nbsp;The model set-up has been run with a range of discharges, including low, moderate, and high with three different sets of bifurcation angles. Furthermore, three different sizes of sediment of varying densities have been used to find the transport capacity of sediment for individual bifurcated angle. A set of data have been collected for different conditions like varying discharge, angle of bifurcation, mean size of sediment () particle and a comprehensive analysis have been done with respect to collected data to see how discharge and sediment load (bed-load) are distributed over the bifurcated branches. The present physical model study has determined the optimum discharge in the main channel for which the sediment and discharge get equally distributed over the bifurcated branches. The experimental data confirm that the distribution of bed load is dependent on the shape of the bifurcation and the sediment transport ratio (\u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e\u003cem\u003e/s\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e) is sensitive to the angle of bifurcation in which \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e1\u003c/em\u003e\u003c/sub\u003e \u0026amp; \u003cem\u003es\u003c/em\u003e\u003csub\u003e\u003cem\u003e2\u003c/em\u003e\u003c/sub\u003e represent sediment transport rate (kg/hr) in respective branches.\u003c/p\u003e","manuscriptTitle":"An experimental study to determine the effects of particle size and bifurcation angle on the distribution of flow and sediment transport parameters in a bifurcated channel.","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2024-04-12 15:42:53","doi":"10.21203/rs.3.rs-3909326/v1","editorialEvents":[{"type":"communityComments","content":0}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"researchsquare","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":true,"externalIdentity":"","sideBox":"","snPcode":"","submissionUrl":"/submission","title":"Research Square","twitterHandle":"researchsquare","acdcEnabled":true,"dfaEnabled":false,"editorialSystem":"","reportingPortfolio":"","inReviewEnabled":false,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"641af119-5256-49f9-b134-8fb433b1468e","owner":[],"postedDate":"April 12th, 2024","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"posted","subjectAreas":[],"tags":[],"updatedAt":"2024-04-12T15:42:59+00:00","versionOfRecord":[],"versionCreatedAt":"2024-04-12 15:42:53","video":"","vorDoi":"","vorDoiUrl":"","workflowStages":[]},"version":"v1","identity":"rs-3909326","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-3909326","identity":"rs-3909326","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}