The Computation of Theoretical Depth Datum in the Changjiang Estuary and Its Adjacent Sea Areas

The tidal height data of 94 sites in the Changjiang Estuary and its adjacent sea areas are analysed using the G·Godin`s tidal height analysis and prediction programs revised by Foreman. The harmonic constants of 11 constituents and the corresponding mean sea level are found. The theoretical depth datum (TDD), lowest possible low water level, Indian spring low water level and chart datum on British admiralty charts of 94 tidal sites are computed and contrasted. And the relationships between them are given by statistical analysis methods. The formula of theoretical depth datum for the Changjiang estuary and its adjacent sea areas are fit by multi-ply regression from SPSS soft. Thus, the four datum distribution in the sea area is obtained and discussed. The established formula for the possible maximum tidal level difference in the Changjiang estuary and its adjacent region are analyzed and given out.