Sea-level, tides and residuals in Alexandria Eastern Harbour, Egypt

摘要

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 M2constituents 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.