Analysis of sedimentation in connection to grain size and shear stress at lower reach of the Rupnarayan river, West Bengal, India

Transcription

1 Indian Journal of Geo-Marine Sciences Vol.45(9), September 2016, pp Analysis of sedimentation in connection to grain size and shear stress at lower reach of the Rupnarayan river, West Bengal, India 1 Swapan Kumar Maity & 2 Ramkrishna Maiti 1 Department of Geography, Haldia Govt. College, West Bengal, India 2 Department of Geography and E. M., Vidyasagar University, Midnapur, West Bengal, India [ 1 swapan.maity55@gmail.com ; 2 ramkrishnamaiti@yahoo.co.in] Received: 16 August 2013; revised: 09 October 2013 Bathymetric close grid survey of the lower reach of Rupnarayan River was made using Dumpy Level and Echo sounder interfaced with Position Fixing System (GPS). Simultaneous tidal observations were available at an interval of half-an hour. Velocity during high and low tide is measured by Digital water meter and floating method. Rate of sedimentation in three seasons (Pre-monsoon, Monsoon and Post-monsoon) was measured by keeping the wooden tray on river bed for few days. Textural analysis of sediment grains by sieving technique reveals that sediments are mainly of fine to coarse in nature. Moderate to moderately well sorting of sediments indicate low and moderate energy condition in the ional environment. Predominant positive skewness and mesokurtic to nature of the sediments indicate continuous addition of finer or coarser materials and retention of their original characteristics during ion. Most of the sediments are transported by suspension with rolling, graded suspension and uniform suspension before ion. Sediments are ed by combined effects of and fluvial processes under shallow agitating environment and carried by turbidity action. Shear stress during swifter and stronger high tide is more than during slower and weaker low tide [Key words: Sedimentation, shear stress, sediment texture, skewness, suspension.] Introduction The flow velocity lowers than the threshold causes ion of the sediment particles 1. If the incoming sediment supply is similar to the sediment which is being entrained, then the sediment coming in to a particular reach may replace the entrained sediment 2-4. But if a huge amount of sediment is discharged from upstream area, the river response by aggrading in order to steep the gradient and increase its velocity to become more competent 5-6. Rate of sediment transport and accumulation in estuarine environments are affected by tidal s and river discharges 7. Transportation and ion processes of sediment particles are affected by the parameters like roundness, sphericity, surface texture, detrital heavy mineral ratio, biogenic components and syngenetic minerals, which quantify grain, further aid to identify the environment Character of the bed sediment is also significant, for it is not only the size of the sediment that is important, but also the arrangement of different grain sizes Grain size distribution is controlled by the physical transportation of sediment, including sediment aggregation and ion, gravitational circulation, tidal pumping and tidal trapping 14. Sediment grain size influences flow resistance by altering the hydraulic characteristics near the bed of the channel Palaeo environment can be interpreted from grain size analysis of sediments The coarser sediments are found in highenergy environments while finer sediments clog at low energy regimes Shepard 20 has distinguished beach from dune and from river s. Texturally, the river sediments are y and are coarse grained, whereas in an estuary the sediments are clayey and fine grained 26, though at the head of the estuary, is dominant. According to Morten Pejrup 27, a constant clay/mud ratio can explain different degree of flocculation of the suspended sediment, which in turn is strongly influenced by turbulence of the estuary. In detail study on various ion environments, Friedman 23 found that when skewness of distribution was plotted against mean (phi value), the dune s, ocean beach s and the lake beach s shows a clear complete separation. Moiola and Weiser 25 have added the regime of river s into the same plot. River s can be differentiated from beach s in a bivariate plot where sorting of grains is plotted against skewness 23. Friedman 23 and Moiola and Weiser 25 pointed out that kurtosis and skewness of a given sediment population when plotted against each other is an efficient tool to differentiate the environment of ion of 28 sediments. Sahu has employed Linear

2 MAITY & MAITI: ANALYSIS OF SEDIMENTATION AT LOWER REACH OF RUPNARAYAN RIVER 1129 Discriminate Functions for finding the relation between variances exhibited by parameters. The shear stress in excess of a threshold is indicative of entrainment of sediment, which could potentially result in the degradation of the channel bed or banks 3, 12-13, 29. Shear stress that is exerted on the channel bed as water moves down slope is known to increase with flow depth and channel steepness, as indicated by the DuBoys equation for bankful boundary shear stress 13, 30. Patterns such as sheltering, imbrications, armoring, and variations in sorting can also affect resistance, and in turn the critical shear stress required to entrain the sediment 3, 31. Friction angle changes with the size of the grain relative to surrounding grain sizes, and sheltered particles may require higher critical shear stress to be entrained 32. In addition, in a poorly- substrate with a large range of particle sizes, resistance can vary across the channel bed depending on the coarseness of the sediments in one region versus another, while a well- substrate has a homogenous resistance across the channel 30. During the last few years river Rupnarayan has been incapacitated due to continuous sedimentation leading to formation and development of shoal area. The problem is more severe at lower reach of the river, from Dainan/Kolaghat to Geonkhali. Being a tidal river Rupnarayan is affected by both riverine and maritime processes. In the present study attempts have been made to explain the causes and mechanism of sedimentation at lower reach of the Rupnarayan River in connection with the sediment grain size distribution and shear stress available in the stream. Materials and Methods River Silabati and Dwarakeswar meet at Bandar, and the combined flow is named as Rupnarayan, which joins river Hoogly at Geonkhali covering a distance of 78 km sq. km catchment area of the river has typical tropical monsoonal type of climate with an average rainfall of 1320mm to 1630mm and annual temperature ranges from 11 o C to 45 o C. The entire Rupnarayan River has been divided into 3 reaches. The upper reach having 28 km length is extended between Bandar and Jasar. The middle reach is 10 km long extending between Jasar and Dainan (Kolaghat). The lower reach extends from Dainan to Geonkhali with a length of 40 km and is divided into four sub-reaches (Geonkhali to Dhanipur, Dhanipur to Anantapara, Anantapara to Gopinathpur and Gopinathpur to Dainan reach) based on the necessity of the study. The lower reach is bounded by N to N and E to E. Bathymetric close grid survey of the study area was made using Dumpy Level and Echo sounder interfaced with Position Fixing System (GPS). Simultaneous tidal observations were available at an interval of half-an hour at different gauge stations on the river Rupnarayan. Velocity Fig.1- Study area is measured by Digital water meter and floating method. Water samples during high and low tide were collected to measure the water density and suspended load concentration. Rate of sedimentation in three seasons (Pre-monsoon, Monsoon and Post-monsoon) was measured by keeping the wooden tray on river bed for few days. A total number of 45 sediment samples including 15 during pre-monsoon, 15 during monsoon and 15 during post-monsoon have been collected from different sections of the river based on grain size variation, color variation, geomorphic unit and area of shoaling and scouring using hand auger, for textural analysis by sieving technique. Samples were repeatedly washed, dried, and thoroughly mixed. By successive coning and quartering on a piece of paper a specific weight of 40gm was taken. Dry samples were placed in the uppermost sieve and covered in a set of stacked sieves. Stack of sieves arranged in order so that the coarsest sieve at the top with finer ones below (with a pan at the

3 1130 INDIAN J. MAR. SCI., VOL. 45, NO. 9 SEPTEMBER 2016 bottom to catch any sediment that pass through the lowest and finest sieve). The sieves set are therefore placed on a shaking machine. Sample was then sieved for 15minutes in ro-top mechanical sieve shaker using a standard ASTM Erode colt sieve at half phi intervals. Sediment that has retained on each sieve and pan was collected and weighted using a balance having an Linear Discriminate Analysis (LDA) is done following Sahu 28 to identify the environment of ion. Y1 = Mean (Standard Deviation) Skewness Kurtosis.(5) Y2 = Mean (Standard Deviation) Skewness Kurtosis.. (6) Y3 = Mean (Standard Deviation) Skewness Kurtosis. (7) Y4 = Mean (Standard Deviation) Skewness Kurtosis (8) Fig.2- Sediment samples collection sites accuracy of gm and cumulative weight percentage was calculated and cumulative frequency curves were drawn. The conventional method suggested by Folk and Ward 8 was followed and different size parameters were calculated. Mean, Median, Sorting, Skewness and other statistics are calculated in phi units using Folk and Ward graphical methods. Mean = ( ) (1) 3 Standard Deviation = ( 84 16) ( 95 5). (2) ( ) ( ) Skewness =..(3) ( ) (2 95 5) ( 95 5) Kurtosis = (4) 2.44( 75 25) If, Y then it indicates the Beach environment but Y1 < indicates the Aeolian condition. If, Y then conditions is indicated but Y2 < represents the Beach environment. When Y then environment is indicated but Y3 <-7.41 indicates the environment. The value of Y represents the fluvial while Y4 < 9.81 represent the influence of turbidity. C-M plotting is made after Passega and Byramjee 33 to evaluate the hydrodynamic forces working during the ion of the sediments. The available shear stress (force per unit area) during high and low tide is calculated following DuBoys equation: τ = ρgds. (9) o Where, ρ is the water density (1.00 g/cm 3 ), g is the gravitational acceleration ( m/s 2 ), d is the hydraulic radius (m), and S is the slope. The critical shear stress (amount of force needed to transport the sediment of a particular size) has been calculated following Shields 34 formula; τ = Kg(ρs ρ)d. (10) cr Where, K is the constant (0.045), g is the gravitational acceleration, ρs is sediment density (typically 2.65 gm/cm 3 ), ρ is water density and D is the median grain size in meter. Result and Discussion Rupnarayan River has experienced a net shoaling of million m 3 with million m 3 ion and million m 3 scouring during the last 20 years.

4 MAITY & MAITI: ANALYSIS OF SEDIMENTATION AT LOWER REACH OF RUPNARAYAN RIVER 1131 Table.1- Sedimentation rate at different reaches Sedimentation rate (mm./sq.m./hr.) Reach Geonk hali Dhani pur Ana ntap Gopin athpur Dainan / Kolaghat ur Premonsoon Monsoon Postmonsoon Rate of sedimentation is high during premonsoon and post-monsoon than as in monsoon (Table.1) because in freshet condition voluminous discharge from land increase river energy causing easy removal of sediments. The grain size distribution is believed to be considered of several normal subpopulations representing the sediments transported by the process of rolling, saltation and suspension 35. Textural characteristics of sediments are strongly influenced by several factors, including source area, composition of adjacent lands, climate, length and energy of sediment transport, redox conditions in the ional environments Textural attributes like, Mean (Mz), Standard deviation (σ1), Skewness (Sk1), and Kurtosis (KG) are widely used to reconstruct the ional environments of sediments and sedimentary rocks 38. Correlation between size parameters and transport processes/ional mechanisms of sediments has been established by meticulous studies in many modern and ancient sedimentary environments 8, 21, Mean size is the average size of the sediments influenced by the source of supply, transporting medium and the energy conditions of the ing environment 39, 44. The mean grain size varies between 2.99 to 4.76, 2.86 to 4.58 and 2.79 to 4.87 during pre-monsoon, monsoon and post-monsoon respectively (Figure. 3). So, during monsoon period mean grain is coarser than pre-monsoon and post-monsoon due to voluminous supply of riverine sediment. Texturally, the river sediments are y and are coarse grained, whereas in an estuary the sediments are clayey and fine grained 26. More than half (55%) of the studied sediment samples fall in very fine category and 31% of the samples are coarse type (Table.2, 3 and 4). Remaining 14% are of fine category, mainly found in monsoon season. Coarse and very fine s were ed at a low and moderately low energy conditions and the fine were ed at a moderate energy conditions. Standard deviation measures the sorting of sediments and indicates the fluctuations in the kinetic energy or velocity conditions of the ing agent 28. During pre-monsoon the value of standard deviation varies from 0.45 to 1.32, while in monsoon it varies from 0.62 to During post-monsoon it ranges between 0.66 and In pre-monsoon and postmonsoon season most of the sediments are moderately to moderately well, while in monsoon period more than 50% samples are poorly. Inman 44 and Friedman 24 observed that coarser sediments tend to show deterioration in sorting whereas fine sediments are well. Sign of skewness is related to the environmental energy 45. In the study area 37% of the sediment samples are of fine skewed type, while 33% of samples are near symmetrical and remaining are of very fine and coarse skewed type. The samples collected during pre-monsoon and post-monsoon seasons are characterized by positive skewness but most of the samples (60%) of monsoon season are of negatively skewed (Table.2, 3 and 4). Negative Skewness (coarse skewness) is correlated with high energy and winnowing action (removal of fines) and positive / fine skewness with low energy levels (accumulation of fines) 23. The positive skewness of sediments indicates the unidirectional transport (channel) or the ion of sediments in sheltered low energy environment 46. Fig.3- Spatial variation of size parameters of sediment

5 1132 INDIAN J. MAR. SCI., VOL. 45, NO. 9 SEPTEMBER 2016 Kurtosis is considered as one of the important textural parameters to distinguish various environments as explained by Duane 45 and Mason and Folk 21. The value of Kurtosis varies from 0.59 to 1.93, 0.43 to 1.18 and 0.43 to 1.73 during pre-monsoon, monsoon and post-monsoon respectively (Figure. 3). Nearly 46% of the sediment samples are mesokurtic in nature while very and very samples are around 14% in each (Table.2, 3 and 4). Friedman 47 suggested that extreme high or low values of kurtosis imply that part of the sediment achieved its sorting elsewhere in a high energy environment. The variation in the kurtosis values is a reflection of the flow characteristics of the ing medium Sedimentological datasets are typically large and compiled into tables, but pure numerical information is difficult to understand and interpret. Thus, scientists commonly use graphical representations to reduce complexities, recognize trends and patterns in the data, and develop hypotheses. Of the graphical techniques, one of the most common methods used by sedimentologists is to plot the basic gravel,,, and clay percentages on equilateral triangular diagrams. This means of presenting data is simple and facilitates rapid classification of sediments and comparison of 50 sediment samples. Further, sediment classification has been attempted by plotting the percentage of, and clay in a triangular diagram proposed by Folk 51. As the study area has estuarine characteristics thus, nearly 86% of the sediment samples are of y type, 11% are of muddy and remaining 3% (one sample) fall in y category (Figure.4). The sediment samples of monsoon season are characterized by high proportion of than of and clay. So, particles are finer during pre-monsoon and post-monsoon than monsoon season. According to Sahu 28, the variations in the energy and fluidity factors seem to have excellent correlation with the different processes and the environment of ion. Sahu s linear discriminate functions of Y1 (Aeolian, beach), Y2 (Beach, shallow water), Y3 (shallow, fluvial) and Y4 (turbidity, fluvial) were used to decipher the process and environment of ion. From the values of Y1 and Y2 about 88% of the samples fall in Aeolian and shallow processes respectively. Twenty three samples (51%) were showing the Y3 values fall in shallow environment. During monsoon season most of the samples (80%) fall in fluvial environment. The Y4 values show that about 46% of the samples were ed by fluvial action and 54% by turbidity action (Table. 2, 3 and 4). The results indicate that the ion of sediment in this area is affected by fluvial and processes both. Fig.4- Ternary diagram showing the nature of sediments Table.2- Statistical analysis and Linear discriminate analysis of sediments during pre-monsoon Sediment Type of Sorting Degree of Degree of Linear discriminate analysis Sample sediment asymmetry peakness Y1 Y2 Y3 Y4 1 fine Mesokurtic Aeolian 2 Fine Aeolian 3 fine fine skewed Aeolian 4 fine Leptokurtic Aeolian 5 fine well Mesokurtic Aeolian 6 fine Well Mesokurtic Aeolian 7 fine fineskewed Mesokurtic Aeolian 8 Coarse Aeolian 9 fine Fine- Platykurtic Beach Beach

6 MAITY & MAITI: ANALYSIS OF SEDIMENTATION AT LOWER REACH OF RUPNARAYAN RIVER 1133 skewed 10 Coarse Mesokurtic Aeolian 11 Coarse Aeolian Beach 12 Coarse Beach 13 fine Aeolian 14 Coarse Aeolian 15 Coarse well fineskewed Platykurtic Aeolian Table.3- Statistical analysis and Linear discriminate analysis of sediments during monsoon Sediment Type of Sample sediment 1 Fine 2 Fine 3 Fine 4 fine 5 fine 6 fine 7 fine 8 Coarse 9 fine 10 Coarse 11 Coarse 12 fine 13 fine 14 fine 15 Coarse Sorting well well Degree of asymmetry Coarseskewed Coarse skewed Coarse skewed Degree of Linear discriminate analysis peakness Y1 Y2 Y3 Y4 Mesokurtic Aeolian Platykurtic Aeolian Mesokurtic Aeolian Mesokurtic Aeolian Aeolian Beach Mesokurtic Aeolian l Aeolian Mesokurtic Aeolian Mesokurtic Aeolian Leptokurtic Aeolian Mesokurtic Aeolian Platykurtic Aeolian Mesokurtic Aeolian Mesokurtic Aeolian Table.4- Statistical analysis and Linear discriminate analysis of sediments during post-monsoon Sediment Type of Sample sediment 1 fine 2 Fine 3 fine 4 fine Sorting Degree of asymmetry Coarseskewed Degree of Linear discriminate analysis peakness Y1 Y2 Y3 Y4 Mesokurtic Aeolian Mesokurtic Aeolian Mesokurtic Aeolian Mesokurtic Aeolian Beach

7 1134 INDIAN J. MAR. SCI., VOL. 45, NO. 9 SEPTEMBER fine 6 Fine 7 fine 8 fine 9 fine 10 fine 11 Coarse 12 Coarse 13 fine 14 Coarse 15 Coarse well Coarse skewed fineskewed fineskewed Coarse skewed fineskewed Leptokurtic Aeolian Mesokurtic Aeolian Beach Beach Leptokurtic Aeolian Mesokurtic Aeolian Mesokurtic Aeolian Beach Beach Aeolian Aeolian Aeolian Aeolian The C-M pattern offers a platform for deducing transportation modes of sediments. It is a relationship of C (coarser one percentile value in micron) and M (median value in micron) on log-probability scale. The area of a complete C-M pattern may be divided into sections which are related to sedimentary environments. The location of the plotted points for a single within the area of a complete C-M pattern indicates the probable conditions of transport before ion. The plotting of the points represents that PQR segment is populated (Figure.5) indicating mostly the estuarine characteristics of the sediments 52. So, most of the sediments are transported by suspension with rolling and graded suspension in less turbulent condition. Some of the sediments (mainly during pre-monsoon and post-monsoon) are found in SR segment indicating the uniform suspension of the sediment. Only two samples in monsoon season are transported by rolling and suspension. Most of the sediment samples are located between 50 and 200 microns which indicate poor to moderate sorting of sediments as established elsewhere. Moreover, C is below 1000 microns for most of the sediments infer less violent hydrodynamic condition leading to finer ion. It is the shear stress at the river bed that causes the particles near the bed to move when the shear is greater than the critical shear stress of the particle which is proportional to the particle size. The shear stress in excess of a threshold is indicative of entrainment of sediment, which could potentially result in the degradation of the channel bed or banks 3, 12-13, 29. Same shear generated by a particular flow may be able to move of say, particles, but unable to cause movement of gravels. The particles which move due to the average bed shear stress exceeding the critical value of the particle display different ways of movement depending on the flow condition, sediment size, fluid and sediment densities, and the channel conditions. At relatively low shear stress, the particles roll or slide with continuous contact with the bed (contact load). Fig.5- C-M pattern of sediments in the study area On increasing the shear stress, some particles loose contact with the bed for some time, and hop or bounce from one point to another in the direction of flow (Saltation load). For further increase in shear stress, the particles may go in suspension and remain thus due to the turbulent fluctuations and get carried downstream by stream flow (suspended load).

8 MAITY & MAITI: ANALYSIS OF SEDIMENTATION AT LOWER REACH OF RUPNARAYAN RIVER 1135 Available shear stress, during high and low tide and the critical shear stress for different grain sizes for pre-monsoon, monsoon and postmonsoon seasons have been calculated (Table.5, 6 and 7) in the study area. The analysis of the relation between available shear stress and critical shear stress reveals that during all the seasons at all places where available shear stress is less than critical shear stress are characterized by ion of sediments. As the studied reach is affected by tide, shear stress during swifter and stronger high tide is more than during slower and weaker low tide. During high tide the shear stress is more than critical shear stress of a particular grain size causing easy landward movement of the sediments but low tide shear stress is less than critical shear stress which hinders easy clearance of sediments causing the sedimentation. Table.5- Available and critical shear stress during premonsoon Sedime nt sample Available shear 2 Critical shear stress Remarks stress (N/m ) τ 2 o (N/m ) τ = = ρgds cr High Low Kg(ρs ρ)d tide tide Erosion Deposition Erosion Deposition Erosion Deposition Erosion Deposition Deposition Deposition Deposition Erosion Deposition Deposition Erosion Table.6- Available and critical shear stress during monsoon Sedime nt sample Available shear 2 Critical shear stress Remarks stress (N/m ) τ 2 o (N/m ) τ = = ρgds cr High Low Kg(ρs ρ)d tide tide Erosion Deposition Erosion Erosion Erosion Erosion Erosion Erosion Erosion Deposition Deposition Erosion Erosion Erosion Erosion Table.7- Available and critical shear stress during postmonsoon Sedime nt sample Available shear 2 Critical shear stress Remarks stress (N/m ) τ 2 o (N/m ) τ = = ρgds cr High Low Kg(ρs ρ)d tide tide Erosion Deposition Deposition Deposition Erosion Deposition Deposition Deposition Deposition Deposition Deposition Erosion Erosion Deposition Erosion In case of some sediment samples though the critical shear stress is less than available shear stress (mainly during monsoon season) but sedimentation happens. It is due to the factors like sheltering, imbrications, packing of grains, grainfabric effects, adhesion forces and organic mats 3-4. Thus, for particle sizes less than about 0.2 mm, the threshold stress needed for entrainment must increase as particles get smaller because particles in that size range are submerged in the laminar sub-layer and therefore not subject to greater stresses associated with turbulent flow 53. Mueller et al. 30 stated that in a poorly- substrate with a large range of particle sizes, resistance can vary across the channel bed depending on the coarseness of the sediments in one region versus another, while a well- substrate has a homogenous resistance across the channel. Friction angle changes with the size of the grain relative to surrounding grain sizes, and sheltered particles may require higher critical shear stress to be entrained 32. Grain-fabric effects refer to the way in which grains organize themselves into interlocking arrangements in which the whole structure is stronger than the component grains. Adhesion forces refer to surface-tension effects and to the mutual electrochemical attraction that

9 1136 INDIAN J. MAR. SCI., VOL. 45, NO. 9 SEPTEMBER 2016 some very fine particles such as clay exhibit. These forces have no practical relevance for channels formed in or gravel but they are very important in muddy ( and clay) channels. Organic mats represent another factor independent of grain size that can affect the force required to initiate movement of a particle on the bed of a river. Mud and -bed rivers commonly develop a surface mat of algae during prolonged low flows. Conclusion The mechanism of sedimentation is the result of combined effect of riverine and processes in connection to grain size distribution and energy fluctuation during high and low tide in different seasons. The deficit of energy than the critical energy to transport a particular grain size during low tide is the main reason behind the rapid sedimentation here. Granulometric analysis of sediments indicates wide variation of mean grain size in different seasons and fine to coarse in nature. Sediments are moderately to moderately well (except monsoon season) due to low and moderate energy condition in the ional environment. Sorting character infers that the sediments are mostly from the sources during high tide, because finer sediments are well than coarser 24, 44. Predominant positive skewness and mesokurtic to nature of the sediments indicate the ion of sediments in low energy condition and continuous addition of finer or coarser materials and retention of their original characters during ion 46. From the energy process discriminate functions of Sahu 28, it reveals that the sediments were ed by combined effects of and fluvial processes under shallow agitating environment and carried by turbidity action. Most of the sediments are transported by suspension with rolling, graded suspension and uniform suspension before ion as indicated by C-M pattern. References 1. Morisawa, M.E., Streams, there dynamics and morphology, (Mc Graw-Hill, New York) 1985, pp Lane, E. W., Design of stable alluvial channels, Transactions, American Society of Civil Engineers, 120(2776) (1955), Charlton, R., Fundamentals of fluvial geomorphology, (Routledge, New York, NY) 2007, pp Clayton, J. and Pitlick, J., Persistence of the surface texture of a gravel-bed river during a large flood, Earth Surface Processes and Landforms, 33(5) (2008), , doi: /esp Smith, K.G., Erosional processes and landforms in Dadland National Monument, South Dakota, Geol. Soc. Amer. Bull., 69 (1974), Mackin, J.H., Concept of the graded river, Geol. Soc. Amer. Bull., 59 (1948), Hall, M.J, Nadeau, J.E and Nicilich, M., The use of trace metal content to verify sediment transport from Delaware Bay on to the New Jersey inner shelf, J. Coastal Res., 3(1987), Folk, R. L. and Ward, M.C., Brazos River bars (Texas): a study in the significance of grain size parameters, J. Sediment. Petrol., 27 (1) (1957), Friedman, G.M., Differences in size distributions of populations of particles among s of various origins, Sedimentology, 26(1979), Martins, L.R., Significance of Skewness and Kurtosis in environmental interpretation. Journal of Sedimentary Petrology, 35(3) (1965), Tulsa. USA. 11. Dietrich, W. E., Kirchner, J. W., Ikeda, H. and Iseya, F., Sediment supply and the development of the coarse surface layer in gravel-bedded rivers, Nature, 340(6230) (1989), , doi: /340215a Buffington, J. and Montgomery, D., A systematic analysis of eight decades of incipient motion studies, with special reference to gravel-bedded rivers, Water Resources Research, 33(8) (1997), Church, M., Bed material transport and the morphology of alluvial river channels, Annual Review of Earth and Planetary Sciences, 34 (2006), , doi: /annurev.earth Wai, O.W.H. Wang, C.H., Li, Y.S., Li, X.D., The formation mechanisms of turbidity maximum in the Pearl River estuary, China. Marine Pollution Bulletin., 48 (2004), Leopold, L., The hydraulic geometry of stream channels and some physiographic implications, (English, U.S. Govt. Print. Off., Washington) [Online] Available from: ic_geometry_of_stream_channels_and_som e_physiographic_implications (Accessed 18 April 2010). 16. Leopold, L., Sediment size that determines channel morphology, dynamics of Gravel Bed Rivers, (J. Wiley, New York, NY.) 1992, pp Jain, R. K. and Kothyari, U. C., Cohesion influences on erosion and bed load transport, Water Resources Research, 45 (2009), 17, doi: /2008wr Beal, M. and Shepard, F., A use of roundness to determine ional environments. J. Sed. Petrol., 26(1956), Bradley, W.C., Sub erosion and wave cut platforms. Bull. Geol. Soc. Am. 69(1999), Shepard, F.P., Distinguishing between beach and dune s. J. Sed. Petrol. 31(1960), Mason, C.C. and Folk, R.L., Differentiation of beach, dune and aeolian flat environments by size analysis, Mustang Island, Texas. Jour. Sed. Pet., 28 (1958), Folk, R., A Review of Grain-size Parameters. Sedimentology., 6(1966),

10 MAITY & MAITI: ANALYSIS OF SEDIMENTATION AT LOWER REACH OF RUPNARAYAN RIVER Friedman G.M., Distinction between dune, beach and river s from their textural characteristics, J. Sediment. Petrol., 31 (4) (1961), Friedman, G.M., Dynamic processes and statistical parameters compared for size frequency distribution of beach river s, J. Sediment. Petrol., 37 (2) (1967), Moiola, R. J. and Weiser D., Textural parameters: an evaluation, J. Sediment. Petrol., 38 (1) (1968), Muraleedharan, Nair, M.N. and Ramachandran, K.K., Textural and trace metal distribution in sediments of Beypore estuary. Indian J. of Mari Science., 31 (2002), Morten Pejrup., The triangular diagram used for classification of estuarine sediments: A new approach. Tide Influenced Sedimentary Environments and Faces., 34 (1988), Sahu, B. K., Depositional mechanism from the size analysis of clastic sediments, J. Sediment. Petrol., 34 (1) (1964), Ritter, D., Kochel, R. and Miller, J., Process Geomorphology, (McGraw-Hill Companies, The, New York, NY) 2002, pp Mueller, E., Pitlick, J. and Nelson, J., Variation in the reference shields stress for bed load transport in gravel-bed streams and rivers, Water Resources Research, 41(4) (2005), doi: /2004wr Clayton, J., Local sorting, bend curvature, and particle mobility in meandering gravel bed rivers, Water Resources Research, 46 (2010), doi: /2008wr Wiberg, P. L. and Smith, J. D., Calculations of the critical shear stress for motion of uniform and heterogeneous sediments, Water Resources Research, 23(8) (1987), , doi: /WR023i008p Passega R. and Byramjee R., Grain size image of clastic s. Sedimentology., 13(1969), Shield, N.D., Anwendung der ahnlickeit Mechanik under Turbulenzforschung auf die Geschiebelerwegung, (Mitt. Preoss Versuchanstalt fur Wasserbau und Schiffbau) 1936, pp Inman, D.L., Sorting of sediments in the light fluid mechanics, Jour. Sed. Pet., 19 (1949), Bhatia, M.R., Cook, K.A.W., Trace element characteristics of graywackes and tectonic setting discrimination of sedimentary basins. Contribution of Mineralogy and Petrology, 92 (1986), Fralick, P.W. and Kronberg, B.I., Geochemical discrimination of clastic sedimentary rock sources. Sedimentary Geology., 113(1997), Amaral, E.J., Depositional environment of the St. Peter stone deduced by textural analysis. Jour. Sed. Pet.., 47 (1977), Visher, G. S., Grain size distributions and ional processes, J. Sediment. Petrol., 39 (3) (1969), Valia, H.S. and Cameron, B., Skewness as paleoenvironmental indicators. Jour. Sed. Pet.,. 4 (1977), Wang.et.al. Cross shore distinction of sediment texture under breaking waves along low energy coasts. Jour. Sed. Res., 68 (1998), Asselman, N.E.M., Grain size trends used to assess the effective discharge for flood plain sedimentation. River Waal, The Netherlands. Jour. Sed. Research,. 69 (1999), Sly, P.G., Thomas, R.L. and Pelletier, B.R., Comparison of sediment energy-texture relationships in and lacustrine environments. Hydrobiologia., 91 (1982), Inman, D. L., Measures for describing the size distribution of sediments, J. Sediment. Petrol., 22 (3) (1952), Duane, D.B., Significance of skewness in recent sediments, western Pamlico Sound, North Carolina, J. Sediment. Petrol., 34 (4) (1964), Brambati, A., Stratigraphy and sedimentation of Siwaliks of North Eastern India. Proc. Inter. Sem. Intermontane Basins: Geology and Resources, Chiang Mai, Thailand. (1969), Friedman, G.M., On sorting, sorting co-efficient and log normality of the grain size distribution of stones, J. Geol., 70 (1962), Seralathan.P. and Padmalal, D., Textural studies of the surficial sediments of Muvattupuzha river and central Vembanad Estuary, Kerala. Jour. Geol. Soc. India, 43 (1994), Baruah, J., Kotoky, P. and Sarma.J.N., Textural and geochemical study on river sediments: A case study on the Jhanji river, Assam. Jour. Indian Assoc. Sedimentologists., 16(1997), Poppe, L.J. and Eliason A.H., A Visual Basic program to plot sediment grainsize data on ternary diagrams. Computers & Geosciences., 34 (2007), Folk, R.L., Petrology of Sedimentary Rocks, (Hemphill Publishing Co., Austin) Ramanathan, A.L., Rajkumar, K., Majumdar, J., Singh, G., Behra, P.N., Santra, S.C. and Chidambaram, S., Textural characteristics of the surface sediments of a tropical mangrove sundarban ecosystem, India. Indian Jour. of Mar. Sci., 38 (4) (2009), Komar, P.D., The analysis of grain-size measurements by sieving and settling tube techniques. Journal of Sedimentary Petrology, 54(1988),