CHAPTER 6SIZE ANALYSIS

6.1 INTRODUCTION

Grain size is studied for a variety of reasons. It is a fundamental

descriptive measure of sediment and sedimentary rocks. It is also important in

understanding the mechanisms operative during transportation and deposition. The

distance of sediment transport size analysis provides reliable criteria to decipher

the nature of source rocks, mode of origin and transportation of the detritus,

paleotectonic and paleoclimatic setup of positive and negative regions,

environments of sedimentation and post-depositional changes experienced by

sediments.

Granulometric analysis of clastic rocks has beeii discussed in its varied

aspects by a number of workers. More significant contributions have been made

in the past three decades by Greenman (1951), Inman (1952), Folk and Ward

(1957), Passega (1957, 1962), Mason and Folk (1958a), Friedman (1958. 1961,

1962a, 1967, 1979), Tanner (1958, 1964), McCammon (1962a, 1962b), Emrich

and Wobber (1963), Spencer (1963), Sahu (1964a, 1964b, 1965, 1966, 1967,

1968, 1975, 1977), Schlee and Webster (1965), Folk (1966), Griffiths (1967),

Moiola and Weiser (1968), \/isher (1969), Jones (1970). Martini (1971). Textoris

(1971), Shea (1974), Clark (1976), Middleton (1976), Swan el a/. (1976), Adams

(1977), Sagoe (1977), Valia and Cameron (1977). Greenwood (1978), Viard and

Breyer (1979), Goldberry (1980), Stow and Bowen (1980), Tucker and Vacher

(1980), Chaudhri and Khan (1981), Chaudhri et at. (1981), Chaudliri and

74

Chakraboity (1982), Chaudhri and Chandra (1982). Chaudhri and Ramanujam

(1982), Chaudhri (1983), Brierley and Hickin (1985), Ying Wang et al. (1986),

Dawson (1988), Patro (1993), Peter (1993), David (1994), Gregory (1995),

Padmalal (1996) and others.

The sediment texture and its downstream variation in the Neyvar river is

examined in this chapter. This section covers the size parameters of sands of'

Neyyar mainstream from Agasthyamalal to Poovar and of the sands covering the

major tributaries upstream and from major downstream side tributaries. Size

analyses were done by sieving graphic measures of moment measures.

6.2 ANALYTICAL TECHNIQUES

The methods for size analysis are based on one of the three fundamental

principles, viz., setting velocity, sieving, and thin section technique. The various

methods used have their merits and demerits. The choice of method used is

governed mainly by the material at hand and the objectives.

Sieving method is used for size analysis of sediments from Neyyar river

basin. About 250 samples of from Neyyar river covering both tributaries and

main stream were washed with distilled water and dried. The dried samples were

subjected to sieve for half 'phi' interval in Ro-Tap sieve shaker at 15 minutes

interval. The ASTM mesh sizes of 5, 7, 10, 14. 18. 25. 35, 45, 60, 80, 120,

170. 250 and pan were utilized for sieving analysis. The sieved samples were

collected in separate polythene bags, labelled, weighed and kept for further

analysis.

75

Number percentage frequency distributions were computed at half-phi

interval. The frequency curves, cumulative curves and log probability ' plots were

also made. The graphic measures were calculated with the help of formulae

provided by Folk and Ward (1957). Moment measures were calculated with the

help of computer, using the programme based on the formulae suggested by

Jricdiitan aII(I Sanders (1978) and data framed in tables.

6.3 GRAPHIC MEASURES

The various graphic measures calculated for the Neyyar river basin include

mode, median, graphic mean (M 2 ), inclusive graphic Standard deviatioi ((71),

inclusive graphic skewness (SKI), graphic kurtosis (KG). A brief description of

each of the parameters is given below.

6.3.1 MODE

Mode represents the most frequently occurring particle size and is denoted

by the highest point on the frequency curve. Croxton and Cowden (1939)

proposed a method to calculate 'mode' in relatively symmetrical curves. From

cumulative curve, it can be determined by taking readings at steps of 0.1 within

each range of half-phi till the maximum percentage is recorded. Folk and Ward

(1957) termed this measure as 'modal concentration'. The parameter is mainly

controlled by two factors, namely, size of the material, and nature of the

depositing medium and therefore, reflects the denudation and depositional history

of sediments.

76

6.3.2 MEDIAN

Median refers to the particle size corresponding exactly to the 50

percentile. The parameter can be read directly from the cumulative frequency

curve. Folk and Ward (1957) suggested that median should hot be used to

describe average size of the particles.

In the sediments having normal distribution (Skewness zero), the phi

values of mode, median, and mean sizes coincide with one another. In others, the

three parameters may have widely different values (Friedman and Sanders, 1978).

6.3.3 GRAPHIC MEAN (Mz)

Graphic mean gives the average size of the sediments. ilie parameter can

be calculated by the formula

16 + 450 + 84

Graphic Mean (Mz)

3

Where Mz is the mean size, 16 is the average mean of the coarsest

third, and 84 is the average mean of the finest third.

According to Folk and Ward (1957), graphic iueaii (Mz) is twice accurate

an approximation to the moment mean (x). The mean size of the sediments

facilitates decipherment of the nature of the source rocks, mode and distance of

transportation and environment (S) of accumulation.

77

6.3.4 INCLUSIVE GRAPHIC STANDARD DEVIATION (a

Inclusive graphic standard deviation () evaluates sorting of the sediments.

This in turn, helps reconstruct the sedimentation history of the detritus. The

formula proposed by Folk and Ward (1957) is used in this work to compute the

inclusive graphic standard deviation ((Y) of the Neyyar river basin.

4)84 - 4)16 4)95 - 4)5Inclusive graphic standard deviation (o) = +

4 6.6

Where () is the inclusive graphic standard deviation and 4)95, 4)84, 4)16

and 4)5 are the percentiles of the respective numbers and are read directly on the

abscissa of the cumulative curve. A verbal classification of inclusive graphic

standard deviation values ranging from any positive decimal fraction to over four

was suggested by Folk and Ward (1957). The classification is reproduced herein.

Less than 0.35 very well sorted

0.35 to 0.50 well sorted

0.50 to 0.71 moderately well sorted

0.71 to 1.00 moderately sorted

1.00 to 2.00 poorly sorted

2.00 to 4.00 very poorly sorted

More than 4.00 extremely poorly sorted

78

6.3.5 INCLUSIVE GRAPHIC SKEWNESS (SKI)

Skewiiess refers to the smmet1y of the distibution and indicates whether

the sediments have a tail of fine or coarse fraction. The formula suggested by

Folk and Ward (1957) is used to calculate the inclusive graphic skewness (SKI)

values of the sediments of Neyyar river basin.

4)84 + 4)16 - 2 4)50 4)95 + 4)5 - 24)50Inclusive graphic skewness (SKI) = ____________________ +

2(4)84 - 4)16) 2(4)95 - 4)5)

where SKI is the inclusive graphic skewiess and 4)5, 4)16, 4)50, 4)84 and

4)95 are the percentiles of the respective numbers. Their values are obtained from

the abscissa of the graph of the cumulative curves.

A symmetrical distribution has ske 'iiess value 0.00. Any deviation from

this to the positive or negative value indicates fine-skewed or coarse-skewed

nature of the curve respectively. Inclusive graphic skewness values have been

classified into five classes by Folk and Ward (1957).

+03() to +0.10 Fine skewed

+(J 10 to -0.10 Near symmetrical

-0.10 to -030 Coarse skewed

-0.30 to -1.00 Strongly coarse skewed

79

6.3.6 GRAPHIC KURTOSIS (KG)

Kurtosis reflects the peakedness of a frequency curve and measures the

ratio between sorting in the tail of the distribution and that in the central portion.

For the calculation of graphic kurtosis values the author followed the formula

suggested by Folk and Ward (1957) viz.

(4)95 - 4)5)Graphic kurtosis (KG) =

2.44(4)75 - 4)25)

where KG is the Graphic Kurtosis and 4)5, 4)25, 4)75 and 4)95 are the

percentiles of the numbers and are read on the abscissa of the cumulative graph

directly.

Folk and Ward (1957) suggested that the normal distribution has graphic

kurtosis value 1.00. Any deviation from the normal was grouped by them into

six classes.

Less than 0.67 very platykuilic

0.67 to 0.90 platykurtic

0.90 to 1.11 mesokurtic

1.11 to 1.50 leptokurtic

1.50 to 3.00 very leptokurtic

Over 3.00 extremely leptokurtic

80

6.4 MOFVIFN'J' MEASURES

Computatioii of moment m easures involves all grain size classes instead ofa few selected ones (of graphic measures) The term ' moment' in time presentContext is studied ill

two-fold mode: 'moment' involving mobility that involves

force and distance and as in statics involving frequency and distance. Moment

measures were put foul1 by Vaui Ostrand (1925) and su bsequently used and

elaborated by Wentworth (1929) Krumbejim (1936a), Krumbejui and Pettijoim

(1938), Greenman (195 I), Grilfltlis (1962, 1967), McBride (1971), Swan et al.

(1976), Adams (1977), Friedman and Sanders (1978), Friedman (1979) andothers.

Moment measures of the Neyyar river basin were calculated with the help

of IBM 1620 computer. The formulae recommended by Friedman and Sanders

(1978) and Friedman (1979) were used.

6.4.1 MOMENT MEAN

It is also known as the first moment. Moment mean was calculated by

time formula,

fluim)Moment Mean (x) = -

100

Where x is the moment mean, f is time frequency in per cent for each

size class and 14 is the mid-point of each phi size class. Iii symmetrical

distribution the mean is located at the centre of gravity of the distribution.

81

6.4.2 MOMENT STANDARD DEVIATION ()

Moment standard deviation corresponds to sorting as it provides

information about the extent to which particle sizes are clustered about the mean.

By this formula, the value of the moment standard deviation is obtained.

1 (m - x)2

Moment Standard Deviation () =

100

Where cr is the moment standard deviation, 'f' is the frequency in per

cent, n is the mid-point of each size class and xj is the moment mean.

Friedman (1962) grouped the moment standard deviation values into seven

classes.

Less than 0.35

0.35 to 0.50

0.50 to 0.80

0.80 to 1.40

1.40 to 2.00

2.00 to 2.60

More than 2.60

very well sorted

well sorted

moderately well sorted

moderately sorted

poorly sorted

very poorly sorted

extremely poorly sorted

82

6.4.3 MOMENT SKEWNESS (a3)

The textural parameter is a measure of sYmmetry. It reflects the deviation

from a perfectly SY11111letrical curve and is sensitive to the presence or absence of

fine or coarse fraction in the population. It has been calculated with the help of

the formula

Cr- If (m - x) 3

Moment skewiiess (a 3) =

NE

where a 3 , is moment skewness, a is moment standard deviation, f is

frequency in per cent. 114 is mid-point of each size class and x is the moment

mean.

6.4.4 MOMENT KURTOSIS (a4)

Moment kurtosis relates to the relative peakedness, i.e., the width of the

distrjbutjoji relative to the distance between the tails. The parameter is computed

with the help of the formula.

a- 4 If (n - x)4

Moment kurtosis (a4) =

wo

6.5 RESULT AND DISCUSSION

6.5.1 STATISTICAL ANALYSIS OF GRAPHIC MEASURES

The graphic measure of selected samples from upstream to downstream

(Table 6.1 & 6.2) shows the median value of graphic measures ranging from -

83

Table 6.1 Phi Percentiles

SampleNo.

K6-2.70 .50KS 0.45 1.00M3 -1.80 -0.50 -M7-3 -1.30 -0.30J3 -2.30 =2.20 -ND-4 -2.55 -2.40ND- 11 -2.55 -2.45L9 -2.33 -2.10L8 -2.60 -2.50

Ottal 0.70 1.40Munna I 1.50 2.00

Munii2 1.60 1.90Mundl 1.00 1.80Mund2 0.10 1.50S9 0.10 i 0.30Chit I 0.90 --1.8.0-1-Chit2 0.05 1.15Mampl 0.10 1.30Mamp2 0.10 1.30Manip3 -2.50 -2.50Marnp4 -2.30 -2.10NKI 1.00 0.50

Perl 0.10 1.60NK3

-J0.20 0.10

NK4 1.10 1.80Amal 1.30 1.70 -Ama2 1.10 1.45

Vat 0.30 0.70

Vat-2 0.75 1.20

13 1 0.20 -- 1.60

16 25j50j75 84_

- -2.20 -1.30 0.25 0.00 1.101 p0_ 200J 260j 275 320

-0.90 0.10 - 0.60 1.00 1.10 1.50

- 020 - 050 100 140 165 235

-. -2.10 - -1.18 -0.45 0.20 1.35

-2.30 -2.50 -2.10 -1.40 -1.00 1.00

-2.40 -2.35 -2.20 -1.30 -0.80 0.70

- 1.10 0.50 0.70 1.70 2.10 3.00

-2.20 -1.60 0.40 1.70 1 2.20 2.90

-

1.70 190 230 2 70 2 80 3 60

2.20 - - 2.40 2.60 2.80 3.40 3.80

2.30 2.50 2.70 2.90 -----3.00 - 3.90 -

- 2.30 2502.80 3.20j 3.50 -.00

2.10 1 2.30 2.80 3.20 3.40 3.90

0.40 0.90 1070 2.20 2.45 2.95

2.25 2.50 2.80 3.10 3.40 3.80

1.50 1 1.60 1.70 1.90 2.00 2.35

- !: 80 - 2.00 2.40 3.10 3.50 3.90

2.00 2.20 2.60 3.00 3.40 4.00

-240 -2301-150 0.60

0 . __: 0 ._-__I_ 0 0 --_':

1.60 ----1.90 2.60 3.40 - -- 3.60 4.00

2.00 2.20 20 2.90 - 3.10 3.70

0.70 0.80 2.20 2.70 2 3. .80 .30..- ......

2.00 2.30 2.60 3.00 3.40 3.80

2.10 2.30 2.70 2.95 3.25] 3.85 -

1.70 1.85 2.35 2.70 2.80 I

1.00 1.40 1.70 1.90 1.95 2.25

-- 1.40 1.70 - -- 1.90 2.50 2.65---------3.00

2.00 2.30 2.70 I 2.90 3.10 3.80

Table 6.2 Textural parameters (graphic measures) of Neyyar river basin

Sample Mode Median Graphic Inclusive Inclusive GraphicNo. - - - Mean Graphic Graphic Kurtosis

Unmiode Birnode Polymode (Mz) Standard Skewness

Deviation (SKI)-- - - (CI)

K6 - -10 0011 -130 -120 I l2 023 060KS - 20 -- 30 - 200 208 073 015 090M3 JO - - 060 027 080 -030 091M7-3 - -- 12 -- -J I 0 1 00 095 076 -004 121

- 0.0 -1-1.18--------------1.18 ---- 1.13ND4 1.1 3.0 - 2.10 -1.80 0.84 0.72 2.681NDII -LI 0.0 --2.20]-i.80 0.881 0.0 ..1.221L4 0.0 2.0 3.0 1 0.70 0.57 0.95 -0.50

-jo.J

L8 0.0 2.0 J 0.40 0.13 1.92 -0.13 0.67OttaL -- -j 2iö 227 0.68 ---051 1.13

Mull I 3.0- ---- j 260 28 _i 057 033 193Mun2 3.0 - -j 2.70 2.70] 0.48 0.03 2.05Mundl 3.0 - -7 2.80 2.87 1 0.63 0.13 1.29

und2 0 - - 1 2.80 2.77 0.69 -0.08 L09S9 2.0- --- - - --- ----- - 1.70 1.52 0.91 H-0.16 0.84Chit ! 1 30 j - 280 282 1 059 i 002c1lit2 2.0- - - ------1.70 1.73 031 0)4 1.64 -

- Manipl j 2.5 4.0 - 2.40 2.57 0.82 0.23 0.97Mamp2 3.0 -- - - 2.60 -- 2.67 0.76 0.09

Mamp3 l 20 I 00 - I -150 -083 168 055 - 068Mamp4[-I 0 00 JO -03j-050i1 251 011 078NkI 10 4.0 j - - 2.60 2.60 1.03Per 1 3.0 - -. 2.70 _• 0.60 I -0.16 1.23NK3 2.0 2.51 3.0 2.201 1.90 1.01 -0.37--.... 0.69 1NK4 30 40 -26O267 '065 L.

Anial I 3.0 - - 2.70 j2.68 0.62 I-0 . !9] JArna230 -23 228 058 041 096

Vat 11.0 - - 1.70 1.55 0.52 0.3 9_1 1.38

Vat2 - 20 - - I 190 198 0.581 021 092

p i 30 I - - I 270 260 061L-014 l___1. 50_

Table 6.3 Folk and Ward (1957), Size parameters (moment measures) of Neyyar river basin

FIRST SEGMENT - MAJOR UPSTREAM TRIBUTARIES

Agasthyamalai_to KallikkadMean Medium Mode Sorting Skewness Kurtosis

Ki -0.178 -0.253 -0.75 1.34 0.3 2.45K2 0.033 -0.101 0.25 0.9 0.36 3.51K3-B 0.767 0.783 0.75 1.18 0.13 2.86K5-T 0.534 0.551 0.25 0.77 0.13 3.16K6-T -1.085 -1.276 -1.75 1.13 0.94 3.52K7 -1.11 -1.321 -1.75 1.16 1.05 3.83K8 0.986 0.826 0.25 1.27 0.53 2.72K9 2.006 2.004 2.25 0.72 -0.35 3.63K1-B 1.103 1.188 1.25 0.97 -0.24 3.44K11 2.014 2.012 2.25 0.71 -0.35 3.71K12-T -0.2 -0.275 -0.75 1.34 0.33 2.5K13 -0.387 -0.361 -0.75 1.24 0.24 2.48K14-T -0.058 -0.054 0.25 0.93 0.27 3.26K15 -0.964 -0.927 -0.751 1.16 1.18 5.06K16 1.101 1.187 1.25 0.97 -0.23 3.43K17 0.767 0.389 0.25 0.88 -0.03 3.23Ml 0.366 0.507 0.25 1.13 -0.07 2.76M2-T 0.557 -0.457 -1.75 1.54 0.34 2.01M2-B 0.375 0.581 0.75 0.65 -0.41 3.31M3-T 0.504 0.574 0.2510.89 -0.05 281M4-T 0.562 0.375 0.25 0.7 -0.51 5.01M7-1 0.348 1.001 1.25 0.83 -0.36 4.12M7-3B 0.969 0.563 0.75 1.39 . 0.06 3.62M3-B 0.479 1 1.25 0.83 -0.38 4.19M7-3 0.966 2.683 2.25 0.71 1.j9 • 6.14N1-B 2.571 3.019 2.751 0.59 - -1.36 P6.25N2-T 1.01 -2.349 -1.751 0.62 1.7 6.46N13 -0.364 -0.332 -1.751 1. 52 S..,-. 0.29 -, 2.04J26 1 0.524 0.674 0.75 i ,. 1.69 '.0.17 ' 2:11J2-1T -1.221 -1.737 -1:75 126 115 3.6 1J2-3T -0.372 -0.369 -1.75 1.51 0.3 2.08J2-4 -1.224 -1.739 -1.75 1.25 1.14 3.53

S.

?1.• S

Table 6.3 Continues

MAJOR DOWNSTREAM TRIBUTARY (ARUVIKKODUTODU)

Mean Medium Mode Sorting Skewness Kurtosis

Aktl 0.583 0.749 1.25 1.14 -0.52 3.04

Akt2 -1.127 -1.477 -1.75 1.33 1.59 5.23

Akt3 2.38 2.584 2.25 1.1 -0.54 2.48

Akt4 2.188 2.399 2.25 -0.88 -0.73 3.14

Ak15 2.566 . 2.609 2.25 0.61 -0.35 4.57

Akt6 2.511 2.603 2.25 0.67 - -0.83 5.27

Akt7 2.718 2.78 2.75 0.7 - -1.49 7.41

Akt8 2.137 2.28 2.25 0.83 -0.67 - 3.41Akt9 1.854 2.01 2.25 1.06 -0.54 3.09

AktlO 2.61 -2----0.94.684 2.25 0.7 5.61

Aktll 2.532 2.693 2.75 - 0.81-.81 -1.16 4.88

Aktl2 2.527 2.685 2.25 - 0.8 -1.08 4.76

Akt13 2.506 2.604 2.25 0.68 -0.86 5.25

Akt14 2.685 2.81 2.75 0.85 -1.21 - 5.11Aktl5 2.609 2.684 2.25 - 0.7 - -0.94 - 5.61Akt16 2.134 2.204 2.25 0.71 - -0.56 3.94

Aktl7 2.032 2.238 2.75 1.32 -099 3.49

Aktl8 -0.286 -0.278 -1.75 1.59 0.21 1.85

Aktl9 2.562 2.683 2.25 0.71 -1.19 6.18

Akt20 0.384 - 0.227 -0.75 1.67 0.55 2.15

A m r6- 541.32 1.93 6.19

Amr73 0.704 1.112 2.25 2.04 -0.15 1.59

Amrl-7 1.278 1.783 3.75 1.94 -0.4 1.85

Arnr9 0.658 - 0.808 1.25 1.54 -0.08 2.22

Amr2-7 0.907 1.516 2.25 1.93 -0.3 1.76

Arnr3 2.329 2.408 2.25 0.65 -0.35 3.9

Amr4 1. 071 2.721 3.25 1.34 -0.05 1.57

MAJOR DOWNSTREAM SIDE TRIBUTARY - CHITTAR

Cht -0.397-0.604 -1.751 1.441 0.51 2.5

ChtlB 0.682 0.867 2.25j 1.821 -0.11 1.86

Cht2-T 1.342 1.808 2.251 1.391 -0.2 2Z

Cht3 -0.266 -1.06 -1.751 2121 0.62 IZCht4 _0.003_-0.17_-0.2511.2910.64_3.24Cht5-T 2 . 532.642_2.251 __0.691 _.-1.02_5.96Cht6 _2.633_2.754_2.7L_0.771_-1.49_6.69Cht7 _2.575_2.69_2.251 0.721.-1.23_6.34Cht8 2.614 -2.753 2.75 0181_-1.43_6.11

Cht9 2.576 -2697 2.25 -0.741_-1.23_6.12ChtlO 2.612 -2.755 2.75 0.811 _-1.46_6.12

Chtll 2.528 2.699 2.75 0.851_-1.27_5.06

Chtl2 2.641 2.767 2.75 0.791_-1.53_6.6

Chtl3 2.585 2.69 1 2.25 0.71-123 6.55

Chtl4 1.24 1.193_0.7510810.72 2.36

Table 6.3 Continues

SECOND SEGMENT

Kallikkad_to_OttasekharamangalamND-2B -0837 -1 952 -1.75 -1.72 0.79 216ND-3T 0.544 0.613 075 0.72 -039 469ND-4T 0.503 0.697 225 1.84 002 1.57ND-5 0.269 0442 1,25 1.47 -003 24ND-6T -0.237 -0.246 -0.75 1.2 013 2.49ND-7 -0.425 -0.417 -1.751 1.13 031 2.67ND-li -0.192 -0114 0.251 1.3 -0071 2.14ND-8T -1.518 -1,811 -1.751 0.89 151 6.3ND-9B 0.031 -0.956 0.25 1.21 045 302ND-10B 0.36 -0445 -0.75 1.36 053 2.62ND-11 -1,685 -2.695 -1.75 0.94 1.83 5.84ND-12B 0.5461 0695 0.75 1.05 -059 3.47ND-13B 1.929 2,734 325 1.34 -0.241 1.56

D-14 -1.685 -2.693 -1.751 094 1 831 5.84D-15T -1.765 -232 -1.751 084 295 1471D-16 -045 -0471 -0.751 1.05 038 273b17 0.462 0.235 -0.751 1.7 036 1.87

ND-18T 0446 0517 -025 074 -0.02 368ND-19 -0957 -0136 -0,75 1.21 051 303ND-20 -1 215 -2.647 -1.75 1.49 1,36 392L1ND-7 0,478 0652 125 1,47 -004 223L2ND-T 0188 -0089 -1 75 174 0.1 16L3B -1153 -2214 -1.751 138 089 2.51L4ND-B -0.256 -0036 0.751 1.51 -001 1.89L5-7 -0882 -1.578 -1.751 1.54 0.7 2.19L6ND-T -0.441 0681 1.25 1.38 -047 2.66L7-ND 0473 0.6-45 225 1.84 002 1 54L8-T 1838 1815 175 073 -006 308L9 0,9821 1,332 12 1,61 -06 248Li ONTT -0978 -1 648 -1,751 1 45 1 131 294Lii 2145 2.444 225 102 -101 294L12 0.261 0585 1 25 1.5 -037 222L13-B 2,313 2.467 225 0.72 -098 4.45L14ND-B 1 855 1 842 175 0.75 -013 304L15ND-B -1.075 -1.221 -1.75 1.06 0.74 297L16 09771 i 328 1 .251 161 -0,571 245L17 2,133 2 446 2.25 103 -097 3 36L18 1159 113 125 098 038 251L19 -0.853 -1 257 -1.75 146 0.67 227L20 2088 2 241 225 083 -103 443L21 -0.06 -1.014 -1.75 2.37 046 151L22 0, 4r,41 0 233 -0751 106 0 361 185L236 1,8931 1 882 2,251084 -0211 293L24T -0066 -1 025-175 108 046 1 52L25T -1 075 -1,221 -175 145 074 297L26 2 148 2,295 225 1.05 -099 428L27B 0569 0711 075 121 -047 342L28T -0842 -1 214 -i75 161 064 228S27 -0449 -0471 -075 1.13 038 273

w

137 -075 103 05 303

328 125 095 -057 2 45 41 7 -075 098 031 2 446 225 134 -097 038 -075 071 0 24 2 38113 1 251 1 241 038 1 2.51

Table 6.3 Continues

THIRD SEGMENT

Ottasekharamangalam to Mam pazhakaraMun-T 0.165 0.271 -1.751 1.79 . 0.. 1.72Mun-2 1.974 1.896 2.25 0.63 0.21 - -3. * 93Mun-6T 1.528 1.893 2.25 1.39 -0.75 2.89Mun-7T 1.278 1.85 2.25 1.43 -0.77 2.69Otta 2.013 2.213 2.25 0.93 -0.49 2.71Otta2B 2.064 2.221 2.25 0.87 -0.56 3.02Munt-T 2.153 2.159 2.25 0.62 -0.2 3.86Munt-2 1.952 2.342 2.25 1.12 -0.39 1.96Munt3-T 1.797 2.148 2.25 1.17 -0.16 1.68Munt-5 2.579 2.661 2.25 0.65 -1.04 6.54Munt-6 1.828 2.14 2.25 1.14 -0.21 1.77Munt7T 2.224 2.226 2.25 0.62 -0.15 4.03Munt-8T 1.654 1.96 1.25 1.33 -0.86 3.25Munt9-T 1.548 1.631 2.75 1.1 0.3A

8U.

MuntlO 2.66 2.736 2.25 0.67 -1Muntli 2.605 2.699 2.25 0.61 -1.7Muntl2 2.599 2.7 2.75 0.62 -1.8Munt13 2.709 2.723 2.25 0.61 -0.Muntl4 2.598 2.7 3.25 0.62 -1.81 9.79Muntl5 2.996 3.181 2.75 0.68 -267 11.35Muntl6T 2.659 2.736 -1.75 0.68 -1,5 7.98Am-i -1.679 -2.262 0.25 1.03 2.64 10.58Tru-2T 0.111 0.233 2.25 1.5 -0.04 - 2.19Au9T 2.504 2.7 -1.75 - 0.82 -1.19 5.04

Aru-6 -0.538 -0.589 2.25 - 1.tO .32 2.04Aru-7 2.393 2.61 -1.75 0.8.97 .4.42Aru-8 - -0.109 -0.1981 -1.75 - 1.5.15 1.92

* ... .

Fable 6.3 Continues

FOURTH SEGMENT

MAMPAZHAKARA TO VALIYANKOD

MamI_1.122 2.3 3.25 1.88 -0.2 1.610MamVl .313 0.358-1.751.95 0.45 1.91

Mam2 0.397 1.545 2.25 2.17 -0.25 1.29MamM3 2.105 2.173 2.25 073 -0.74 3.96MamK4 2.432 2.526 2.25 0.66 -0.63 5.23MamM5 -0.279 -0.604 -1.75 1.93 0.6 2.06Mam6-T 2.247 2.589 2.25 1.02 -1.32 5.63MarnN7 1.565 1.657 -1.75 0.85 0.01 . 2.4MamN8 1.739 1.733 1.75 037 .. 038 ' 4.39Marn9-T 2.682 2.761 2.75 0.72 -1.35 655MarnNlO 2.387 2.584 2.25 0.83 -0.93 •4.38MamN11T 2.294 2.499 2.25 0.81 -0.77 4.16Mam12-B 2.744 2.779 3.251 0.67 -1.22 6.63MarnN13 2.361 2.549 2.25 0.82 -0.85 4.24MamN14 2.343 2.055 2.25 0.7 0.25 1.66MamN15 1.705 1.723 1.75 043 -0.28 5.57MamNT 2.384 2.577 2.25 0.83 -089 4.3NK1 2.264 2.405 2.25 0.95 -0.64 3.44NK2-T 2.458 2.658 2.25 082 -1.3 5.4NK3-T 2.5 2.676 2.25 0.81 -1.16 5.21NK4 2.451 2.647 2.251 0.82 -1.1 4.96NK5-B 2.617 3.036 2.751 0.88 -1.11 4.15NK6-T 2.44 2.694 2.251 0.86 -116 4.65NK7 2.396 2.617 2.251 0.84 -1.1 4.7NK8-B -0.71 -1.271 -1.751 1.64 0.77 2.36Mda9 0.593 0.803 1.251 1.71 -0.46 2.1MdalO -0.716 -1.277 -1.751 1.63 0.78 -2.36PerliT -0.777 -1.44 -1.751 163 0.85 2.52Perl2-13 -0.274 -0.139 0.751 1.49 -0.02 1.77NK13-T -0.471 -0.547 -1.75 1.37 0.43 2.43NKt14 -0.556 -0.45 0.25 1.22 017 2.2NK15-B -0.293 -0.441 -1.75 1.69 056 2.36NK16-B 2.027 2.15 2.25 0.96 -0.32 2.37NK17 0.607 1.572 2.25 2.01 -0.42 1.53NKAM18 -0.004 -0.122 -0.25 1.44 0.24 2.28

Table 6.3 Continues

FIFTH SEGMENT

Valiyankod_to PoovarVL1T 2.309 2.539 2.25 0.85 -0.77 3.88VL2T 2.312 2.537 2.25 0.84 -0.81 3.99VL3 1.96 1.9 2.25 0.59 0.14 3.94VL4T 2.015 1.946 2.25 0.62 0.12 4VI-5 1.867 1825 1.75 0.69 -0.85 9.41VI-6 1.953 1.894 1.75 0.63 0.2 3.92VI-7 1.428 1.415 1.25 0.42 0.21 4.06VL8 1.788 1.764 1.75 0.7 0.15 3.14VI-9 1.576 1.681 1.25 0.49 -0.6 3.19P1 1.414 - 1 0.44 0.49 5.47P2 1.989 1.923 2.251 0.61 0.09 4.07P3 1.445 1.429 1.2510,42 0.19 3.78P4T 1.971 1.883 1.75 0.62 0.38 3.5P5 2.086 2.201 225 0.76 -0.86 3.85P6 1.85 1.839 1.75 0.74 . 0.03 3.09P7 1.442 1.441 1.25 . 0.42 0.04 3.51Pm1B 1.305 1.285 1.25 0.45 0.09 5.5Pm2B 1.119 1.124 1.25 0.57 0.15 . 2.43Pm3B 2.547 2.644 . 2.25 0.72 ...; -1 5.18Pm4B 1.692 1.706 1.751 0.5 -0.11 . 4.26

2.2d) to 2.8d? and graphic mean from -1.18 to 2.87. The major portion of the

Neyyar river sediment population is of unimodal low about 30% of bimodal,

16.6% of polymodal.

Inclusive graphic standard deviation value ranges from 004 to 1.92

which corresponds to very well soiled to poorly sorted class. Inclusive graphics

skewness fonis 0.50 to 0.72 which corresponds to very coarse skewed to fine

skewed class of Folk and Ward (1957). Graphic kurtosis ranges from 0.60 to

2.684 that lies in the l)latykullic to very Ieptokui-tic size parameter.

6.5.2 ANALYSIS OF MOMENT MEASURES

Analyses of moment measures were done for about 250 samples from

upstream to Poovar, time mouth of the river. Total length of the river is divided

into 5 segments from Upstream to downstream side upto mouth for the'purpose

of calculation of moment measures (Table 6.3).

6.5.2.1 SIZE PARAMETERS OF MAJOR UPSTREAM TRIBUTARIES

6.5.2.1a Kallar

The distribution of sediment size parameters of upstream tributary Aal/ar

is as follows. The mean size of Ka/far ranges from -1. 1 l to 2.006. Standard

deviation values of the majority (90 9%) of sand samples lie between 0.72 to

1.274, in the moderately sorted class of Folk (1961). Skewiess value of samples

of Kallar is between -0.35d and 1.05 in the strongl y fine skewed clas. Kurtosis

value ranges from 2.45 to 3.83, the very leptokurtic class.

84

6.5.2.1b Mullar

Mean size of Mtillar samples varies between 0.34 and 0.96. The

standard deviation ranges from 0.65 to I .54. Majority of the samples are with

in the moderately sorted class of Folk (1961) and a sizeable portion of the

remainder falls under moderatel y sorted class. However standard deviation values

do not show any trend in the direction of transport. Skewiess ranges from 0.35

to I.05& in the strongly fine skewed class. Most of the samples are extremely

leptokurtic. Kurtosis ranges from 2.45 to 3.83.

6.5.2.1c Neyyar

Mean size parameters of Neyyar ranges from 2.57 to 2.844. Sorting

varies between 0.59 to 1.52 in the moderately sorted class, skewiess varies

from -1.36 to 1.7 in the strongly fine skewed class and kurtosis ranges from

2.04 to 6.46 in extremely leptokurtic class.

6.5.2.2 SIZE PARAMETERS OF MAJOR DOWNSTREAM TRIBUTARIES

6.5.2.2a Chittar

Mean size of samples varies from 0.39 to 2.64. Sorting varies between

0.69 and 2.12 in the moderately well sorted class. Skewiiess values range from

1.53 and 0.72 in the strongly fine skewed class. Extremely leptokurtic kurtosis

ranges from 1.864 to 6.69.

6.5.2.2b Aruvikkodutodu

Mean size of the sediments vaiies from I. 1274 to 2.7l8. Sorting value

ranges from 0.88 to 1.59 in the moderately sorted class. Skewimess range from

1.49 to 1 .59. Kurtosis values range from 1.85 to 7.41 in the extreme

leptokurtic class.85 ...

.5.2.3 SIZE PARAMETERS OF MAIN STREAM

For the main stream, moment measures were calculated for 4 segments of

Neyyar river from upstream to downstream such as, Kallikkad to

Ottasekharamangalam, Ottasekharamangalarn to Mampazhakara, Marnpazhakara to

Valiyankod, Valiyankod to Poovar.

6.5.2.3a Kallikkad to Ottasekharamangalam

The mean size of samples from Kallikkad to Ottasekharamaiigalam ranges

from 1.764) to 2.314). The standard deviation ranges from 1.724) to 2.374) that

falls in the moderately sorted class. Skewness ranges from 1.364) to 1.144), which

is classified in the strongly fine skewed class.

From Kallikkad to Ottasekharamangalam the kurtosis value ranges from

1.514) to 14.714) and is in the extremely leptokurtic category.

6.5.2.3b Ottasekharamangalam to Mampazhakara

Here the mean size of samples varies between 1.674) to 2.994). Standard

deviation ranges from 0.614) to 1.794), in the moderatel y sorted class. Skewness

values range fioni 1.814) to 2.644) in the strongl y fine skewed class. Kurtosis

ranges from 1.684) to 10.584). and is classified as extremely leptokurtic.

6.5.2.3c Manipaztiakara to Vallyankoci

Mean size of samples varies between 1.354) to 2.744). The standard

deviation ranges from 0.884) to 2.174) in the moderately sorted class. Skeiess

values ranges from 1.444) to 1.934) for strongl y fine skewed class. Extremely

leptokurtic kurtosis range from 1.294) to 7.414).

86

6.5.2.3d Vallyankod to Poovar

Mean size of' the sediments varies from 1. 1 14) to 2.54). Sorting value

ranges from 0.424) to 0.854) and lies in the moderate sorted class. Skewness

ranges from 1.004) to 0.494), which is in the strongly fine skewed class. Kurtosis

value is extremely leptokurtic and ranges from 3.09 to 5.50.

6.5.3 BINARY PLOTS OF NEYYAR RIVER

To work out the depositional environment of Neyyar river sediments,

binary plots were made for upstream major tributaries, downstream major

tributaries and for Neyyar mainstream. The binary plots were made between

moment sorting and moment mean grain size,size, moment kurtosis and moment mean

grain size, moment mean grain size and moment skevviiess, moment sorting and

moment skewness, moment skewness and moment kurtosis and moment sorting

and moment kurtosis (Fig. 6.1, 6.2 & 6.3). Binary 'plots reveal positive trend.I

6.5.4 CM PATTERN . . .

The CM diagram that plots the coarest one percentile, 'C' against the

median grain size, M (Passega. 1964, Royse, 1968) uses arithmetic size data and

indicates local sorting and transport processes as xNell as discriminating turbidite.

Sediments from traction load in the zone 'NOP' for Neyyar and form

channel lag deposits (Fig. 6.4). A part of the Ne yvar sediment also lies in graded

suspension deposits. 'OR' represent suspended bed material load that accrete as -

on point bars and channel bars.

87

1.8

1

1.4

1 bi)

Cc.# 08

0.6

0.4

0.2

00 1 2 3

Mean

X

7

6

5

C,)

C,)C

3

2

n

7

6

5

J)0

1)

X X

XX

X

y-0286x+357l7

]X X

y = -2.65x + 6.3749

7

X6 X

5 X X

XX. 4.C

3xXXX

2

1 y = O .37x +33912

0 . I

-2 -1 0 1 2 3

Mean

4

3

2

X

t)

o'- 4-. Lj0'%

-1X

-20

Mean

2

15

05

) 0(I)

-0,5

-15

0 0.5

Sorting

y -0,4818x +0.3301

X

2 3

1.5 2

0

05 1 1.5 2 -2 -1 0

1 2

Sorting Skewness

Fig. 6.1 Binary plots of upstream tributaries

2.5

2 XX X

X1.5

XX

XX

y = -0.2838x + 1.4989

0• I

0 1 2Mean

8

X7

6 X XX

X .C,) 5

3 X ^)K^X2 XX

X XXX X

y 04194x + 3 . 2190 . -. - i

-2 -1 0 1 2 3Mean

4

y -05975x +055183

2

3Mean

2

1.5 X

1 . y=05693x-1.0189

C/)0,5 X1

-1 0 1 2 3Sorting

X

X . )

XK

X

X

y -04361x +37211

8 8

7 X

76

X X 6X

5C,)

. 40

IX XK

2XX

y -1 4099 +5.3641

0 00 1 2 3 -2 -1- -0 1 2

Sorting Skevfless

Fig. 6.2 Binary plots ofdo'iistream tributaries

4

y=-02384x+136193.

E 2.5

2ci)

1.5

00

1Mean2

10

9

8 y = 0.6269x + 2,6898

7r

. 6tno

4.

3

2xxx

0 I

-2 -1 0 1 2 3Mean

4y-0.4919x+0,3786

3

,, 2(F)

cl I xx x x

x

-2 x

0 1 ' 2 3Mean

2X

1.5y 0.614x - 0.9215

x05

(F)

. -0,5(ID

-1.5

-20 0.5 1 1.5 2

Soiling

y -251x +6 1672

x

10

9

87

6(I)

. 50

4

2

0

10

9

87

(F) 6(F)0 5

4

3

2

0

y = -0,9865x +32534

X

x'X.X

V

4X

XXXX

0 05 1 15 2 . -2 -1 •0 1 2

Sorting Skewness

Fig. 6.3 Binaiy plots of mainstream tributaries

Fig. 6'f Plot showing C versus M of sedimentsof Neyyar R.

10000

0L.

1000ED

CED0LED

1

010

0.1 1 10 100 1000 10000M Median (micron)

6.5.5 FACTOR ANALYSIS

From the Q-mode factor analysis of size data (Table 6.4 & 6.5) the

variation of size parameters from upstream to doiistream can be clearly studied.

In the Q-mode factor analysis of size only seven factors are considered. From the

histogram of factor scores Vs grain size (Fig. 6.5 & 6.7) and factor matrix Vs

locations from upstream to downstream of Neyyar iiver (Fig. 6.5) the following

observations are made.

6.5.5.1 First factor analysis

From the histogram of factor scores versus values noted a dominance

of fine sand and then followed by very fine sand coarse silt.

6.5.5.2 Second factor analysis

From the plots the dominance of granules is noted in the second factor

followed by very coarse sand and coarse sand.

6.5.5.3 Third factor analysis S .'•

From the plots of third factor scores versus values .doniinance of

medium sand followed by fine sand and coarse sand is noted.

6.5.5.4 Fourth factor analysis

Dominance of granules followed by medium Sand and fine sand is noted

in the histogram of forth factor scores versus values.

6.5.5.5 Fifth factor analysis

In thethe fifth factor the dominance of fine sand followed by granule and

medium sand is noted from the histogram of fifth order scores versus values.

88

N

0

(N0

0

0

0

9)IJ1

I .tU JO

DP

j0C

9

99

99

99

99

xtju

U jO

Jc

iwv

Cl

43E

4

ñ93

ed

epe

W43

JflJdcz

S'IN

Luntil

1438

unvj

IN

I':•

ct

,ewv

lJ-0

'Cled

IEPeAcu C

lUJL13

UflJd

IS ANN

I438

'I)-J

WflLU

runvJ

JNAN

Cl

JIv

L3I3

edPA

injad

S N

Ln

qw

•j

Cl

8-JW

flL!

SUfl V'J

jrr

Cl

tu(I)

XU

WLLI iO

PX

U1C

UI 10134

cw

vC

l

oJIv

flAI3

!lidPA

WflJd

qs 'IN

qw

vJ

qwnqj

6SUflIN

ON

cr

Cl

IvJtA

ZA

17

U)

SC

nr

S

W

ca

os

.)Cd)

so

0-

)

z0

LA

0.)NCl)

00

Cl)

Cl)

.

0.)>(I)0.)

0C.)C

l)

0

cz

pt•

>-

IC

sc

_____

0.)

__

__

_

g•

.C

l)

2•

0C

)C

Cso-

o 0

0

0

0

0

0

0

0

0

0

0

0) 10 N

. CL

) It)

C) N

C'1

sjoos jooj Ill

L)

o 0 0 0 0 0 0 0 0 0 0

0) 10 N

. (0

U

) lq

m

N

soioos iooij i

0

0

0

0

0

0

0(0

N

I7

(0

S0100S

JO

pC

J A

lo o

0

0

0

0

0

0

0

0

0

10 (

0

N 0

1

0 (1) '

N

N

sa

io

os io

p Ii

S'17U)

cc

s.o

o

0S L-&U

)

S C

cu

S* .

g

C1

3 E

A

•c

S 0--

C

.)

S i2

Z- C13

o 0 0 0 0 0 0 0 0

(0

'(N

C

(0(00

SO

JOO

S 1

0O

i1 A

0

0

0

0

0

0

0co

(0(N

C

SO

JOO

S JO

t?J IA

I-0ca

S

U)C)

S £.7

C)

.Q

)

S,o(

0

C)

SC

)0>

u

I-

S P

...

(I)C)

Sc Ii

C_!'

Cft

I1.

ES

L

C) 0

•U)

C)

9,0i

0

o

C)

S 0

--C)0

— C

.)

U)

4-.

Isc

cdC

)

0C)

•U

)

:i 1]0

U)

C)

0_

CC)

0(I)

I-.C

C)

00

00

00

(N'T

c1S

JO

OS

JO

OR

J h

A

Table 6.4 Showing Rotated factor matrix of Q-mode factor analysis ofgrain size of Neyyar river

Fac 4 I Fac 5 Fac 6 1 Fac 7Samid Fac 1

K2 00

K6 -0.004

K5 0.605

MI -0.00!

M3 -0.034

M7-3 0.064J3 -0.005

ND4 0.004

NDII -0.018

L5-Ba -0.011

L9-Sh 0.239

L7Pa 0.794

L8-Cl 0.491

Munna 0.287 I

Ottas 0.764

Muniia 0.740

Munna 0,714

Munna 0.708

Munna 0.992

Munna 0.981

S9S 0,966

Thumb 0.087

Chitt 0.602

I Chitt 0.119

Chitt . 0.988

Chiu 0.991

Chitt 0,974Mampa 0.888

Mampa 0.367

Mampa 0.986

Mampa 0.984

Mampa 0.116

NK Sh 0.706

NK Sh 0.942

Pentin 0.053

NK3-T 1 -0,005

NK4M 0,160

Chemb 0.747

Vadak 0.947

Paul 0.636

Elavu 0,717

Kacha 0,969

Ayiro 0.973

Amara 0.251

Amara 0.833

Vatto 0.886

Vatto 0.455

Vatto 0,432

Vatto 0.382

Vatto 0071

Vatto 0,436

Poova 0.966

Fac 20.1780.9160.0540.1380.0790.0850.9820.9960.9950.9690.3750.0520.3830.7690.0490.125O.0470.0450 0230.0260.0290.6890.1120.3420.0240.022O.0270.0360.0610.0230.0220.0520.0320.0320,9620.7030.5900.0310.0320.0640.0470.0270.0280,3240.0420.0390.056O.05300580,0480.0520.031

Fac 30.045

-0.0260.7760.2070.1650.5140.00!

-0.049-0.0280.03 50.4780.5680.5900.3730.5900.5690.2920.68!0,1110.0840.2350.3950.5430.0720.1210,0990.1900,4440,7970.1080.0780.9740,5590.3220.1490.0180.2510.4480.3070.7180.6740.2320.2230,2490.5350.4540.8530.8910.8750 938'0.8900.245

-0.944-0.332-0.138-0.950-0.895-0.717-0.1810 0210.000

-0.134-0.744-0.131-0.473-0.420-0.186-0.330-0.337.-0043-0.027-0.035-0.046-0.560-0.479-0.889-0.040-0.034-0,054 i

-0.019-0.360-0.040-0.041-0,097-0,037-0.036 1

-0.185-0.704-0.730-0.14!-0.038-0.230-0.083-0.030-0.031-0302-0.048-0.068-0.211-0.088-0236-0,168-0,076-0.052

-0.050-0.051-0.015-0.035-0.016-0.018-0.033-0,017-0.020-0.021-0.0830.078

-0.049-0049:0.047-0.060-0.047-0,020-0.0180.158

-0 068-0076-0.138-0076-0.040-0061-0.08 5-0005-0 026-0.078-0059-0.057-027!-0059-005!-0.046-0.071-01395-0222-0.08 8-0014-0.070-0.017-0,808-0.003-0.022-0043-0035-0037-0.059-0047-0003

a-102-0.143 0.0770.020 0.0200.122 -0.1200.350 -0.1650.445 -0.002

-0.006 0.000-0.009 0.0110.048. -. -0.023

• 0.122. -0.076-0.032. . 0.030-0.085-0.0160.178 -0.0010,039 fO.0380.007' -0.166..

;4014 -00180.032 -0.510

-0.117 -0.0500.013 0.0000.023 0.0280.032 0.019

-0.067 0.016-0.084 -0.110-0.240 . 0.0320.033 0.0060.031 0.007

-0.003 -0.060-0.087 -0.0290.107 -0.2800,049 0,0180.066 0.032

-0,032 0.010-0.141 -0.155-0.022 -0.009. 0,017 -0.009-0.054 0.033-0,149 0,0270.040 -0147

-0.032 -0.0260040. 0.050

-0,071 -0.059-0.009 -0,008-0.000 0.0100.001 0,004

-0,044 0.004-0.024 -0,0270.106-0.005

-0.030 . 0,0250132 -0,0110.009 0.011

-0,068 -0.001-0.007 -0.032

Table 6.5 Showing Elgeti values and Vaiimax factor scores of Q-mode factoranalysis of grain size of Neyyar river

Eigeii values

Eigen values -- Percent of Trade I Cam. % of Trace

30.5130

586790 586790107507

206744 79,35345. 1161

9.8387 89.192130440

58538 95.04590.8445

1.6240 9667000.6642

1.2772 9794720.3830

07365 986837U225

0.4280 991117o 1594

03006 9941830 1406

02704 9968870,0831

01598 99848500357

00687 99.91710.0281

0054 1 999712

O.0150

00288 10000000.0000

0.0000 100000000.0000

00000 1000000W)000

0.0000 100.00(X)00()()0

000000 tOO 000))0 0000

00000 100000000000

0.0O()0 tOO 00000,0000

00000 100 00000.0000

0.0000 100000000000

0.0000 10000000.0000

00000 10000000 0000

0.0000 100.00000 0(X)0

0.0000 100 00(X)0,0000

00000 100000000000

00000 1000000() 0000

00000 100 (XXX)0 0000

0.0000 100 (X)0()0 0000

00000 10000000.0(X)0

00000 10000000.00(X)

00000 10)) 0000-0 0000 -00000 1000000-0.000X) -()()()()0 100 0000-0 0000 -00000 10000(X)-0.0000 -00000 100 00(X)-0.0000 -000000 1000000-()()()0() -00000 1000000-00000 -00000 100M00-0 0000 -00000 100 00(0-0 0000 -00000 10000(X)-0 (XX)0 -00000 100 00(X)-0 0000 -0,0000 100 0000-0 0000 -0000010000(X)-0 0000 -0 0000 100 ()()(X-0 0(X)O -0 0000 100 00(X)-0 0000 -00000 10000(X)-0.0000 -00000 1000000-00000 -00000 100 0000-0 0000

00000 . 100 00(X)-0 0000 -0.0000 100 (X)O0

Varimax Factor Scores

Sam! d-2.0-1.5-1.0-0.50.00.51.01.52.02.53.03.54.04.5

Fac 1-1.709-0.423-0.387-0,763-0.1670.502

-2.844-5.833-2,93331.68287.67015.840M0704,869

Fac2

31.23235.43!183868614. 8077.3784,3775,4016.1842.5654.565

-1.295-0.2980.407 -

Fac3 Fac4-5381 I 47.419 j -

-1,825 1.389

-4.828 -11443 I

-4.32! -22.531

-II 793 -57437

-5.480 -39.116

1853 -51.218

29.889 -29.240

89.761 5.104

27.174 1519

-11.335 -4,254

-8,308 2.303

-7422 . 0225

-0.363 -0.627

Fac 595160 874

-3814-49452,6872.7510.9943.05!1.700

-1 30350. S 86

-83 847-28 523

-9,226

Fac6 Fac7

I- '47.33 54'

-6.667 -. 2.604

-23.697 ' 13.690

-24,282 15.533

- 16 . 386 31.123

16,213 , -73.658

78.48! 9.481

69.659 27.032

-9,779 26.661

-17,012 -5.379

16.411 20.775

15.576 13.803

6.914 -0,682

-2399 -3.949

6.5.5.6 Sixth factor analysis

In the sixth factor there is dominance of coarse sand followed by medium

and granule as noted from the plots of sixth factor scores versus 4) values.

6.5.5.7 Seventh factor analysis

There is dominance of very coarse sand followed by medium sand aiid

fine sand. It is clearly noted in the figure of seventh factor scores versus 4'

values.

6.5.6 DOWNSTREAM SIZE VARIATION

From the plot of factor matrix versus locations from upstream to

downstream upto mouth shows the first factor, i.e., the dominance of fine sand

followed by very fine sand and coarse silt. The first factor dominancç is noted in

locations from upstream near dam side, Ottasekharamangalam and iii one of the

Neyyar major downstream tributary Chittar. Mampazhtakara, Neyyatinkara,

Amaiavila to Vattom and Poovar in the coastal segment.

The second factor, i.e., the dominance of. granules followed by very coarse

sand and coarse sand is noted in areas of Kallar% junction point of Kallar and

Neyyar in the upstream, Near dam area, Penimkadavila. The third factor, medium

sand dominance followed by fine sand and coarse sand is noted in Vattom near

Poovar the confluencing point of Near. The fourth factor, i.e., the dominance

of granules followed by medium sand and fine sand is seen in locations Ka/la,;

Mu//ar. The factors, 5, 6 and 7 are less dominant in location from upstream to

downstream.

89

Size data of samples collected from transects in the channel at different

sampling sites, reveal the role of selective transport in the textural modification.

The distribution of mean size of samples across the channel is non uniform. Non-

uniformity in the mean size is more pronounced towards downstream (Fig. 6.8).

There is a general trend in dowiistream decrease of mean size. The coarse sand

(0.0 to 0.5) fraction persists in the channel. Incidentally presence of most of the

coarse sand is restricted to the thaiweg of the channel. Apparently non-uniformity

of the sediment means across the channel is the result of selective transport due

to variation of energy imparted to the bed material oil uneven channel bed.

It was noticed that most of thalweg sediment are poorly sorted and

platykurtic. Addition of a new mode in the main population call rise to a

bimodal sediment which is poorly sorted and platvkurtic (Folk and Ward. 1957).

The higher energy in the thalweg during high water stage permits only gravel to

coarse sand to settle as the main population followed by fine sand a later

addition. Fraser (1935) considered that at any instant a river usuall y deposits only

material of a very limited size range.

Russell (1934) suggested that two factors favour the sorting process. They

are I. Rapid aggredation and 2. Extreme variation in discharge. Of these two

conditions, the latter seems to he true in the case of Nev yar, as the discharge is

highly seasonal.

Bar sediments generally are unimodal. Unimodality call the result of

over passing of gravel size material. Allen (1983) showed that those gravel size

90

clasts tend to over pass a bar by bouncing and rolling faster than the particles of

sand size.

Neyyar sands are mostly near symmetrical with a -low negative skewness

(Table 6.3). Duane (1964) suggested that winnowiüg action would produce a

negatively skewed sediment but Folk and Ward (1957) demonstrated that in

Brazos River skewness is a function of mean size of the sediment and a

sediment dominantly of sand with a small tail of gravel is negatively skewed.

Like the Brazos River, it appears that the negative skewness of Neyyar sand is

the reflection of the dominance of sand mode in the sediment. A similar

observation was reported by Self (1975). Krumbein (1940) and Plumley (1948)

have proposed that if the sediment contains suhequal amount of sand and gravel

or if sand dominates, the resulting size distribution would be near-symmetrical and

negatively skewed. In Neyyar, the seasonality of flow (due to monsoonal climate)

and its relatively high velocities tend to winnow and remove the finer sediment,

causing non-deposition, leading to a scarcity of positive skeiiess. Further, it is

evident firom the sediment supplied from the source zone of the drainage basin is

dominated by coarse to medium sand. Therefore, in Neyyar river, skewness of

sediment is a function of the nature of flow and size distribution of detritus in

the source zone.

6.5.7 ROLE OF TRIBUTARY INFLUX

Downstream modification of sediment is effected b y selective transport and

abrasion. However, Blatt (1967) pointed out that there is lack of hard data to

support such 'intutions' of geologists. The effect of tributary influx, is a major

91

hurdle in gathering hard, supporting data for evaluating the role of selective

transportort or abrasion in the downstream modification of sediment attributes

(Davies el al., 1978).

In the following discussion, the nature of size distribution of sediments in

major tributaries, upstream and downstream viz.. KalIai: Nej ....Mu//ar in the

upstream side, Chitiar and Aruvikkodutodu in the downstream side and its effect

on the mainstream are examined.

A prominent decrease of mean size and standard deviaton as a fi.tnction of

distance is noted in C/uivar and Aruvikkodoiodu. But such a tend is not evident

in Ka//a, Neyyai; Mu//ar (higher gradient tributaries) the sediment at the

headstream reaches, is characteristically coarser with a mixture of pebble and

coarse and medium sand. In the tributaries downstream, mean size reduces rapidly

with a simultaneous improvement of sorting which is perhaps a consequence of

fall in the stream gradient. A similar explanation was offered by Self (1975).

Kalla,: Neyyai; Mu//ar are the major tributaries supplying considerable quantities

of water and sediment to the mainstream. Although one ought to expect a

prominent effect of these three major tributaries oil size distribution of

sediment in mainstream, textural data of samples collected from these tributaries

at points 5 kill upstream of the confluences with the mainstream reveal the

contrary. The samples collected are reasonably identical. This implies a similarity

in texture and mineralogy of the rock types of provenance of the tributaries as

well as of the mainstream. Besides, this may indicate the adjustment existing

92

between the morphological attributes and water and sediment discharge of the

river system (Chovely and Kennedy, 1971).

The down river size distribution especially the mean size, shows a

downstream coarsening trend from Ottasek1iaraiangalam to Poovar. The lower

order tributaries are high gradient category supplying coarse to medium sand.

Therefore the downstream increase in mean size could be the result of tributary

dilution.

The cause of variation of size parameters of sediment in the upstream

reaches of mainstream (from Agasthyanzalai to Poovar) is examined. Trivikaramji

(1986) reported that wide fluctuation in size parameters of sediment of Neyyar

river in South Kerala is a result of human activities.

93