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Investigation of tidal asymmetry in the Shatt Al-Arab river estuary, Northwest of Arabian Gulf

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Lafta A. A.

Oceanologia

2022

tom No. 64 (2)

376--386

Approximately one-year water level records were utilized for examining the tidal dynamics and tidal asymmetry at the Shatt Al-Arab river estuary. The harmonic and the tidal skewness, two traditional methods in quantifying tidal asymmetry in tidal systems, were used. The water level measurements revealed a presence of a tidal wave attenuation when propagating further towards the inland direction, with notable reductions in the tidal range. The results of the harmonic analysis indicated that the diurnal and semi-diurnal constituents experience considerable damping towards the upstream direction. The largest constituent was M2, followed by K1, O1, and S2. The largest shallow water constituent was MK3, followed by M4, MS4, MN4, and M6. The tidal form number ranged from 0.68 to 0.7 along the estuary; then, mixed, mainly semi-diurnal tidal nature was observed. However, six possible combinations of tidal constituents were used to quantify the tidal asymmetry, involving the interactions between astronomical constituents alone as well as with the higher harmonics. According to the harmonic method, the relative phase difference of M2 and M4 constituents was in the range of 63 to 87.06, suggesting a flood dominance behavior of tidal wave along the estuary. Positive values of the tidal skewness were observed at all stations, with a pronounced increase towards the inland direction. The M2 and M4 interaction was the main contributor to tidal asymmetry, followed by M2-K1-O1, M2-S2-MS4, M2-M4-M6, K1-M2-MK3, and M2-N2-MN4 interactions.

General characteristics of tidal currents in the entrance of Khor Abdullah, northwest of Arabian Gulf

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Lafta A. A.

Oceanologia

2023

tom Vol. 65 (3)

494--502

The general characteristics of tidal currents in the entrance of the Khor Abdullah at Iraq marine water, located at the northwest tip of the Arabian Gulf, were studied based on realistic current measurements. The velocity measurements used in this study extended to about one year, which was never previously available in this vital region of the Arabian Gulf. The results illustrated that this area is characterized by strong currents exceeding 1 m/s during both ebb and flood tides, driven by local water level variations. The maximum currents recorded during the study period were 1.65 and 1.36 m/s at the ebb and flood tides, respectively. Additionally, the monthly averages of ebb currents are higher than those of flood currents. The harmonic analysis results revealed that the tidal effect explained approximately 98% of the variation in water currents, with the remaining percentage due to residual currents. Among the 35 tidal components used in harmonic analysis, the M2 component was the main contributor to tidal currents variation in the area, followed by S2, K1, N2, and O1. The residual current seems to have a low effect on the currents variations in the area, with maximum values not exceeding 0.0677 and 0.058 m/s during the ebb and flood tides, respectively. The results obtained give a general view of the tidal current behavior and could be beneficial for several aspects of marine and coastal engineering as well as shipping and navigation activities in this region.