Management, January 2–4, St. Thomas’ College Thrissur, Kerala, Limnological Association of Kerala.
Rogers, S., and Skrabal, T. E., 2011. Managing erosion on estuarine
shorelines. The Sound Front Series.
Stanley, D. J., and Warne, A. G., 1998. Nile delta in its destruction
phase. Journal of Coastal Research, 14, 794–825.
Striebig, B. A., 1999. Sustainable residential design and construction. The Pennsylvania State University, Information Technology
Services
(ITS),
https://www.courses.psu.edu/c_e/
c_e433_bas124/erosion.html
Cross-references
Sediment Transport
SEDIMENT GRAIN SIZE
Gautam Kumar Das
Department of Chemical Engineering, Jadavpur
University, Kolkata, West Bengal, India
Synonyms
Grain size analysis; Grain size distribution; Sediment particles size; Texture
Definition
Texture refers to the general physical appearance of the
sediment.
Grain size is the average size of the grains in a sediment
sample. It is also known as the particle size.
Sand consists of grains of particle size ranging from
0.0625 to 2 mm (0.002–0.08 in.). It pertains to particles
that lie between silt and granules on the Wentworth scale
of grain size. Sand size class ranges from À1.0 to 4.0 (phi).
Silt consists of grains of particle size ranging from
0.008 to 0.0625 mm (0.0003–0.002 in.). It is intermediate
in size between sand and clay. Silt size class ranges from
4.0 to 8.0 (phi).
Clay consists of grains of particle size between silt and
colloid. These include any of the various hydrous aluminum silicate minerals that are plastic, are expansive, and
have ion-exchange capacities. Clay size class ranges from
8 (phi) and onwards.
Introduction
Sediment is made up of loose particles of sand, silt, and
clay. Particle size refers to the diameter of individual
grains of sediment. It is a fundamental descriptive measure
of sediments from any environment. Grain size analysis of
estuarine sediments is required to study the trends in surface processes related to dynamic conditions of transportation and deposition.
Measures of the grain size distribution
The nature of grain size distribution in sediments of estuarine or any environment can be described on the basis of
five specific parameters. The graphic mean size is an arithmetic average of a series of diameter values. The median
diameter is the 50th percentile diameter of a cumulative frequency curve drawn on arithmetic probability paper. Standard deviation is expressed as measures of dispersion
(sorting) of sediments, and it is the square root of the arithmetic average of the squares of all the deviations from the
mean size value of a series of observations. Skewness measures the asymmetry of the grain size distribution. Grain
size distribution is skewed when the mean deviates from
the median. Skewness of the sediments for symmetrical
grain size distribution is zero. Skewness becomes negative
when the grain size is skewed toward smaller phi value, and
it is positive when skewed toward higher phi value. Kurtosis is the condition of peakedness or flatness of the graphic
representation of a statistical distribution.
Expression of sediment grain size
Estuarine waters transport a wide range of sediments varying in size from 2 mm (0.002 mm) to more than 4 mm, but
finer sizes dominate most estuaries. A few estuaries transport sand (>62 mm), gravel, and larger sediments.
Sediment grain size is measured in metric units as
propounded by Wentworth (1932). It was expressed as
phi (f) by Krumbein (1938), since the logarithmic diameter has more significance in a discussion of the statistical
relations of sediments. Sediment grain size in phi (f) is
expressed as the negative logarithm to the base 2 of the
sediment particle diameter in mm. Thus sediment grain
size is expressed as follows:
f ¼ Àlog 2 e
where f is the sediment grain size and Ɛ is the negative
numerical value of the diameter. Ɛ is equal to 2, 1, ½, ¼,
etc., whereas f is equal to À1, 0, +1, +2, etc. Thus f
increases with decreasing diameter.
Sand is the particle size of 0.0625–2 mm
(0.002–0.08 in.). It pertains to particles that lie between
silt and granules on the Wentworth scale of grain size.
Sand size class ranges from À1.0 to 4.0 (phi). Silt is
a particle size of 0.008–0.0625 mm (0.0003–0.002 in.).
It is intermediate in size between sand and clay. Silt size
class ranges from 4.0 and 8.0 (phi). Clay is a particle size
between silt and colloid. Any of the various hydrous aluminum silicate minerals are plastic, are expansive, and
have ion-exchange capacities. Clay size class ranges from
8 (phi) to higher.
Sampling of estuarine sediments
Utmost care is needed in sampling estuarine sediments
because the grain size analyses are sensitive to the manner
in which the original samples are collected, handled, and
preserved. Introduction of any foreign particle into the
sample through improper care, cleaning of equipment, or
processing can alter the texture. Estuarine landforms such
as point bars, river mouth bars, tidal shoals, major tidal
inlets, and upstream and downstream of the rivers are ideal
SEDIMENT GRAIN SIZE
555
Rogers, S., and Skrabal, T. E., 2011. Managing erosion on estuarine
shorelines. The Sound Front Series.
Stanley, D. J., and Warne, A. G., 1998. Nile delta in its destruction
phase. Journal of Coastal Research, 14, 794–825.
Striebig, B. A., 1999. Sustainable residential design and construction. The Pennsylvania State University, Information Technology
Services
(ITS),
https://www.courses.psu.edu/c_e/
c_e433_bas124/erosion.html
Cross-references
Sediment Transport
SEDIMENT GRAIN SIZE
Gautam Kumar Das
Department of Chemical Engineering, Jadavpur
University, Kolkata, West Bengal, India
Synonyms
Grain size analysis; Grain size distribution; Sediment particles size; Texture
Definition
Texture refers to the general physical appearance of the
sediment.
Grain size is the average size of the grains in a sediment
sample. It is also known as the particle size.
Sand consists of grains of particle size ranging from
0.0625 to 2 mm (0.002–0.08 in.). It pertains to particles
that lie between silt and granules on the Wentworth scale
of grain size. Sand size class ranges from À1.0 to 4.0 (phi).
Silt consists of grains of particle size ranging from
0.008 to 0.0625 mm (0.0003–0.002 in.). It is intermediate
in size between sand and clay. Silt size class ranges from
4.0 to 8.0 (phi).
Clay consists of grains of particle size between silt and
colloid. These include any of the various hydrous aluminum silicate minerals that are plastic, are expansive, and
have ion-exchange capacities. Clay size class ranges from
8 (phi) and onwards.
Introduction
Sediment is made up of loose particles of sand, silt, and
clay. Particle size refers to the diameter of individual
grains of sediment. It is a fundamental descriptive measure
of sediments from any environment. Grain size analysis of
estuarine sediments is required to study the trends in surface processes related to dynamic conditions of transportation and deposition.
Measures of the grain size distribution
The nature of grain size distribution in sediments of estuarine or any environment can be described on the basis of
five specific parameters. The graphic mean size is an arithmetic average of a series of diameter values. The median
diameter is the 50th percentile diameter of a cumulative frequency curve drawn on arithmetic probability paper. Standard deviation is expressed as measures of dispersion
(sorting) of sediments, and it is the square root of the arithmetic average of the squares of all the deviations from the
mean size value of a series of observations. Skewness measures the asymmetry of the grain size distribution. Grain
size distribution is skewed when the mean deviates from
the median. Skewness of the sediments for symmetrical
grain size distribution is zero. Skewness becomes negative
when the grain size is skewed toward smaller phi value, and
it is positive when skewed toward higher phi value. Kurtosis is the condition of peakedness or flatness of the graphic
representation of a statistical distribution.
Expression of sediment grain size
Estuarine waters transport a wide range of sediments varying in size from 2 mm (0.002 mm) to more than 4 mm, but
finer sizes dominate most estuaries. A few estuaries transport sand (>62 mm), gravel, and larger sediments.
Sediment grain size is measured in metric units as
propounded by Wentworth (1932). It was expressed as
phi (f) by Krumbein (1938), since the logarithmic diameter has more significance in a discussion of the statistical
relations of sediments. Sediment grain size in phi (f) is
expressed as the negative logarithm to the base 2 of the
sediment particle diameter in mm. Thus sediment grain
size is expressed as follows:
f ¼ Àlog 2 e
where f is the sediment grain size and Ɛ is the negative
numerical value of the diameter. Ɛ is equal to 2, 1, ½, ¼,
etc., whereas f is equal to À1, 0, +1, +2, etc. Thus f
increases with decreasing diameter.
Sand is the particle size of 0.0625–2 mm
(0.002–0.08 in.). It pertains to particles that lie between
silt and granules on the Wentworth scale of grain size.
Sand size class ranges from À1.0 to 4.0 (phi). Silt is
a particle size of 0.008–0.0625 mm (0.0003–0.002 in.).
It is intermediate in size between sand and clay. Silt size
class ranges from 4.0 and 8.0 (phi). Clay is a particle size
between silt and colloid. Any of the various hydrous aluminum silicate minerals are plastic, are expansive, and
have ion-exchange capacities. Clay size class ranges from
8 (phi) to higher.
Sampling of estuarine sediments
Utmost care is needed in sampling estuarine sediments
because the grain size analyses are sensitive to the manner
in which the original samples are collected, handled, and
preserved. Introduction of any foreign particle into the
sample through improper care, cleaning of equipment, or
processing can alter the texture. Estuarine landforms such
as point bars, river mouth bars, tidal shoals, major tidal
inlets, and upstream and downstream of the rivers are ideal
SEDIMENT GRAIN SIZE
555