stretches. This characteristic depositional behavior of
sediments favors tidal accumulation rather than its formation from unidirectional flow from the upper to the
lower stretches. The downstream accumulation of sand
suggests the influence of flood flow, whereas the
upstream mud is the result of a standstill during the high
and low tides.
The sediments are generally very well-sorted to
medium-sorted fine silt in nature. Samples are slightly
negative to slightly positively skewed (SK 1 ) and are
platykurtic in nature. Inflections generally at two to
three truncation points are a statistical fact for all
the samples. All the cumulative curves are mostly
nonlinear, showing close resemblance in pattern with
each other.
Texture of point bar sediments
Texturally, the sediments are generally composed of 95 %
silt, with subequal proportions of fine sand and clay
forming the remaining 5 %. Sediments are mostly well
sorted to moderately sorted, with graphic mean size
belonging mostly to the silt fraction. Most of the sediments show a slight tendency toward negative skewness.
The cumulative curves mainly exhibit higher peakedness,
with K G values often close to 1.0.
Sandy sediments of the point bars show a completely
different pattern from that of sandy silty sediments. The
cumulative curves for these sediments show a nonlinear
pattern and are perfectly comparable to that of the sandy
point bar sediments. These sediments display two major
inflections at 2.25 phi and 3.25 phi, respectively. These
inflections divide the curves into three subpopulations as
rolling, siltation, and suspension, respectively. The saltation population constitutes about 75 % of the materials,
the rest being deposited by either rolling or suspension.
Silty sediments having range from 4 to 9 phi show exactly
the same pattern where the three subpopulations can be
well recognized. In these curves, the inflections take place
at 6–7 phi, respectively. The central saltation population
constitutes about 75 %. These sediments do reflect their
deposition from tractive movements of water in the estuarine flow condition.
Texture of marsh sediments
The marsh sediments are composed of 90 % silt with
subequal proportions of fine sands and clays forming the
rest. The marsh sediments are mostly moderately well
sorted to moderately sorted, with the graphic mean size
belonging to the silt fraction. Most samples exhibit
a slight tendency of negative skewness. The negative
skewness in the marshy region of the estuaries perhaps
indicates trapping of larger bed-load particles by the marsh
vegetation. The cumulative curves primarily show a high
peakedness with greater K G values. The statistical size
parameters of the sediment samples are very much analogous to lagoon or distal shelf sediments.
Texture of mangrove swamp sediments
Tidal flats are mostly siliciclastic. The sediments are generally silty to sandy. All the cumulative curves are
non-lognormal. The silty sediments are extremely zigzag
and reflect deposition out of ebb-flood cycles. The statistical size parameters show that the sediments are mainly well
sorted to moderately sorted, with graphic mean size belonging to the silt fraction. Most sediment samples show a slight
tendency of negative skewness. The cumulative curves
largely show high peakedness, with K G values often greater
than 1.0. The cumulative curves for the sandy sediments
exhibit three distinct subpopulations (i.e., rolling, saltation,
and suspension subpopulations). The cumulative curves for
the silty sediments, however, show more intricate zigzag
patterns reflecting ebb-flood cycles.
Texture of dune sands
The grain size of dune sands generally shows lognormal
distribution with very fine sand and well-sorted sediments.
The graphic mean size ranges between 2.5 and 3.5 phi.
The graphic standard deviation indicates well-sorted finer
sand particles. The sorting value reflects reworked intertidal zone sediments through wind transportation cycles.
Dune sediments exhibit a slightly positive skewness
because of admixture of very small quantity of finer
suspended particles to the lognormal saltation population.
Kurtosis of sediments is very close to 1.0 indicating lognormal distribution with mesokurtic characteristics.
Textural sensitiveness
There is rhythmicity in the nature of deposition, which
perhaps indicates the depositional pulses for the ebb and
flood flows through rivers. The inflection points in the
curves between successive ebb-flood cycles are marked
at 2.5–3.0 phi, 3.5 phi, 5–6 phi, and 8 phi sizes, respectively. Such rhythmicity in the nature of depositional
behavior of tidal sediments is supposed to be highly process responsive.
Sandy sediments (ranging from 1.5 to 4 phi) from the
point bars and mid-channel bars of estuaries display
a completely different pattern from that of sandy silt sediments. The cumulative curves for these sediments exhibit
a nonlinear pattern and are comparable to that of the other
point bar sediments. These sediments have two major
inflections, one at 2.25 phi and the other at 3.0–3.5 phi.
These inflections divide the curves into three subpopulations as rolling, saltation, and suspension, respectively.
The saltation population generally constitutes about
75 % of the total material, the rest being deposited by
either rolling or suspension. Silty sediments having
a range from 4 to 9 phi from similar areas also show
exactly the same pattern where the three abovementioned
subpopulations can be well recognized. In these curves,
the inflections take place at 6–7 phi, respectively. The central saltation population constitutes about 70 %. These
sediments reflect their deposition from tractive movements of water in a unidirectional flow condition.
SEDIMENT GRAIN SIZE
557
sediments favors tidal accumulation rather than its formation from unidirectional flow from the upper to the
lower stretches. The downstream accumulation of sand
suggests the influence of flood flow, whereas the
upstream mud is the result of a standstill during the high
and low tides.
The sediments are generally very well-sorted to
medium-sorted fine silt in nature. Samples are slightly
negative to slightly positively skewed (SK 1 ) and are
platykurtic in nature. Inflections generally at two to
three truncation points are a statistical fact for all
the samples. All the cumulative curves are mostly
nonlinear, showing close resemblance in pattern with
each other.
Texture of point bar sediments
Texturally, the sediments are generally composed of 95 %
silt, with subequal proportions of fine sand and clay
forming the remaining 5 %. Sediments are mostly well
sorted to moderately sorted, with graphic mean size
belonging mostly to the silt fraction. Most of the sediments show a slight tendency toward negative skewness.
The cumulative curves mainly exhibit higher peakedness,
with K G values often close to 1.0.
Sandy sediments of the point bars show a completely
different pattern from that of sandy silty sediments. The
cumulative curves for these sediments show a nonlinear
pattern and are perfectly comparable to that of the sandy
point bar sediments. These sediments display two major
inflections at 2.25 phi and 3.25 phi, respectively. These
inflections divide the curves into three subpopulations as
rolling, siltation, and suspension, respectively. The saltation population constitutes about 75 % of the materials,
the rest being deposited by either rolling or suspension.
Silty sediments having range from 4 to 9 phi show exactly
the same pattern where the three subpopulations can be
well recognized. In these curves, the inflections take place
at 6–7 phi, respectively. The central saltation population
constitutes about 75 %. These sediments do reflect their
deposition from tractive movements of water in the estuarine flow condition.
Texture of marsh sediments
The marsh sediments are composed of 90 % silt with
subequal proportions of fine sands and clays forming the
rest. The marsh sediments are mostly moderately well
sorted to moderately sorted, with the graphic mean size
belonging to the silt fraction. Most samples exhibit
a slight tendency of negative skewness. The negative
skewness in the marshy region of the estuaries perhaps
indicates trapping of larger bed-load particles by the marsh
vegetation. The cumulative curves primarily show a high
peakedness with greater K G values. The statistical size
parameters of the sediment samples are very much analogous to lagoon or distal shelf sediments.
Texture of mangrove swamp sediments
Tidal flats are mostly siliciclastic. The sediments are generally silty to sandy. All the cumulative curves are
non-lognormal. The silty sediments are extremely zigzag
and reflect deposition out of ebb-flood cycles. The statistical size parameters show that the sediments are mainly well
sorted to moderately sorted, with graphic mean size belonging to the silt fraction. Most sediment samples show a slight
tendency of negative skewness. The cumulative curves
largely show high peakedness, with K G values often greater
than 1.0. The cumulative curves for the sandy sediments
exhibit three distinct subpopulations (i.e., rolling, saltation,
and suspension subpopulations). The cumulative curves for
the silty sediments, however, show more intricate zigzag
patterns reflecting ebb-flood cycles.
Texture of dune sands
The grain size of dune sands generally shows lognormal
distribution with very fine sand and well-sorted sediments.
The graphic mean size ranges between 2.5 and 3.5 phi.
The graphic standard deviation indicates well-sorted finer
sand particles. The sorting value reflects reworked intertidal zone sediments through wind transportation cycles.
Dune sediments exhibit a slightly positive skewness
because of admixture of very small quantity of finer
suspended particles to the lognormal saltation population.
Kurtosis of sediments is very close to 1.0 indicating lognormal distribution with mesokurtic characteristics.
Textural sensitiveness
There is rhythmicity in the nature of deposition, which
perhaps indicates the depositional pulses for the ebb and
flood flows through rivers. The inflection points in the
curves between successive ebb-flood cycles are marked
at 2.5–3.0 phi, 3.5 phi, 5–6 phi, and 8 phi sizes, respectively. Such rhythmicity in the nature of depositional
behavior of tidal sediments is supposed to be highly process responsive.
Sandy sediments (ranging from 1.5 to 4 phi) from the
point bars and mid-channel bars of estuaries display
a completely different pattern from that of sandy silt sediments. The cumulative curves for these sediments exhibit
a nonlinear pattern and are comparable to that of the other
point bar sediments. These sediments have two major
inflections, one at 2.25 phi and the other at 3.0–3.5 phi.
These inflections divide the curves into three subpopulations as rolling, saltation, and suspension, respectively.
The saltation population generally constitutes about
75 % of the total material, the rest being deposited by
either rolling or suspension. Silty sediments having
a range from 4 to 9 phi from similar areas also show
exactly the same pattern where the three abovementioned
subpopulations can be well recognized. In these curves,
the inflections take place at 6–7 phi, respectively. The central saltation population constitutes about 70 %. These
sediments reflect their deposition from tractive movements of water in a unidirectional flow condition.
SEDIMENT GRAIN SIZE
557