Sea-level, tides and residuals in Alexandria Eastern Harbour, Egypt
2021
Tarek M. El-Geziry
The present study focuses on a comprehensive sea-level analysis in Alexandria Eastern Harbour (AEH). The study is based on hourly sea-level records from 10.06.2018 to 15.06.2020, from the new Inexpensive Device for Sea-level Measurement (IDSL), installed in AEH in June 2018. Before analysis, sea-level records were referred to the Mean Lower Low Water (MLLW) in the Harbour of −429 cm. The T_TIDE package was used to generate the astronomical tides. Residuals were calculated by subtracting the astronomical elevations from the observed sea-levels.Results revealed a mean sea-level of 24.6 cm. The seasonal behaviour of sea-level was determined with the lowest monthly means in spring and the highest in summer and winter. Tides in the Harbour are of semidiurnal type; with a mean tidal level of 0.05 cm. 23 tidal constituents out of 36 are significant, with SSa and M2 constituents having the largest amplitudes of 5.4 cm and 5.1 cm, respectively. Results revealed a ratio of 4.7 between spring and neap ranges. Residuals contribute to 99.0% in the recorded sea-level. The design risk factor and return periods of positive sea-level ranges were calculated and introduced in the present work.
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