International Journal of Marine Science, 2017, Vol.7, No.2, 8-18
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2.2.6 The water (sea) level fluctuation
The evolution of the sand spit may be attributed to sea level fluctuations as described by Bernardes and Rocha
(2007). The high tide permit the marine water to enter the estuary. In addition the sea level rise due to the climate
change increase the possiblity to enter the saline water into the estuary.
2.2.7 Other environmental forces
Natural disturbances caused by the environmental forces include winds and tidal currents (Miththapala, 2013).
Short-term natural events causing significant stress to estuarine environments are primarily weather related:
hurricanes, tropical storms or northeasters.
2.3 Grain size analysis of Rosetta Estuary sediments
Sediments samples were collected from the middle of the stream of Rosetta Estuary at four sites (R1, R2, R3 and
RB) at the interval of 1/2 km distance as shown in Figure 1. The dominant mean grain size of the sediments under
investigation is fine sand with 98% with no gravel or clay. Table 1 lists the percentages of sediment gradient
components. Table 2 categorized the results of sediment grain size analysis as mean grain size, sorting, skewness
and kurtosis and their description. The sorting of the surface sediments indicated that there is similarity of the
sorting category of the sediments in front of the estuary and inside it as moderately well sorted or moderately
sorted. This indicated that the estuarine sediments contains allochthonous sediments, which is probably from the
coastal area. The investigation of the grain size analysis of the sediments revealed that due to diminish of alluvial
river sediments the sand detected in the Rosetta Estuary is originally transported from the coastal area.
Table 1 Percentages of Rosetta Estuary sediments compositions during March 2015
Sample ID
Gravel %
Sand %
Silt %
Clay %
R1
0
98.34
1.66
0
R2
0
99.24
0.76
0
R3
0
99.13
0.88
0
RB
0
98.66
1.34
0
Table 2 Mean grain size (ɸ), sorting (ɸ), skewness and kurtosis of Rosetta Estuary sediments during March 2015
Sample ID
Mean (phi)
Sorting (phi)
Skewness
Kurtosis
R1
2.75
0.63
0.08
1.06
Fine sand
Moderately well sorted Near symmetrical
Mesokurtic
R2
2.49
0.79
﹣
0.05
0.96
Fine sand
Moderately sorted
Near symmetrical
Mesokurtic
R3
2.49
0.8
﹣
0.13
1.35
Fine sand
Moderately sorted
Coarse skewed
Leptokurtic
RB
2.7
0.66
0.03
1.19
Fine sand
Moderately well sorted Near symmetrical
Leptokurtic
The results of skewness indicated that the distribution of the grain size is near symmetrical and it skewed slightly
toward the coarse size at the end of the estuary (R3) as shown in Table 2. This is in agreement with the finding of
King (1972).
3 Conclusions
Estuaries are highly dynamic ecosystems that are very vulnerable both to natural and anthropogenic disturbances.
In order to study the morphology of Rosetta Estuary especially its depositional land forms such as spit , this work
has been done. The investigation of Rosetta spit revealed that through the period of study from 2007 to 2015 its
shape and location were changed with time. Spit was formed inside the Rosetta Estuary. Different factors were
discussed, which affecting the formation of the spit inside the Rosetta Estuary. The first factor is the Reduction in
water discharge to Mediterranean Sea through Rosetta Estuary, which mainly occurred after the establishment of
the Aswan high Dam. The difference in salinity between the river water and the recent estuarine water is
considered as the second factor. Limitation of sediments flow with river water to Rosetta Estuary is one of the
