Sea level as a major oceanographic parameter is always needed in the field of
hydrographic surveying for Chart Datum (CD) realization. Lowest Astronomical Tide
(LAT) is a physical surface and the most recent used tidal datum as defined by the
International Hydrographic Organization (IHO); "The lowest tidal level may occur
under average meteorological conditions and under combination of any astronomical
conditions" (IHO, 2011). It was adopted to be used as the vertical tidal datum for depths
reduction on nautical charts. In the current paper, the main objective is to calculate the
height of (LAT) referred to the mean sea level in Al-Ahmadi harbor, Kuwait. Sea level
data were measured by sea level sensors using offshore Acoustic Doppler Current
Profiler (ADCP). Simulated sea level time series was acquired from Delft-3D
hydrodynamic model, and then it was used for chart datum calculation. Both
observed and modeled sea level series were analyzed using harmonic analysis
technique, to separate tidal from non-tidal components. Results of both data sets
modeled and observed (tidal and non-tidal signals) were cross-correlated for model
validation. Results showed a strong direct correlation between both tidal and residual
components from both data sets by 97.93 % and 98.06 % respectively. Furthermore,
from harmonic analysis it was found that M2 (Principal lunar semi diurnal), K1
(principal luni-solar diurnal), O1 (principal lunar diurnal) and S2 (Principal solar semi
diurnal) are the most significant and dominant tidal constituents in the area. Moreover,
tidal type regime Form Factor (FF) ratio shows a mixed semi-diurnal tidal regime by
(0.85). These outcomes agree with the results obtained by (Pous, 2012; and Akbari,
2016) using shallow water model and 3D coastal ocean model respectively, for the same
area. The tide asymmetry ratio, which is regarded as the major representation of harbor
sediment transport, was 0.0193 and 0.0191, respectively, for both observed and
modeled datasets, indicating that there is a distortion in tide wave in the area, with ebbdominant
outflow sediment
transport
away
from
the
harbor.
Finally, from modeled sea
level dataset, LAT as Chart-datum in the area was found (1.57 m) below Mean Sea
Level (MSL),
which is higher than the one calculated by the European Petroleum
Survey Group (EPSG 5188) during mina Al-Ahmadi refinery construction in 2004 by
(5 cm). |
