Amplified Msf tides at Kochi backwaters on the southwest coast of India

NOTICEABLE transformations occur in the pattern and range of tides during their propagation from the open ocean into continental shelves and further into shallower coastal waters, broad lagoons and backwaters. Such transformations, caused by a myriad of topographical and bathymetric influences, are indicated by the presence of relatively large-amplitude over-tides and compound-tides. These tidal constituents represent the nonlinear harmonics generated primarily under the influence of large bottom friction. Wave phenomena such as reflection, resonance, etc. may also affect the various tidal constituents in different ways. Mutual interaction of the tidal constituents exerts an important influence on the propagation and shape of the tides in estuaries and backwaters. The study presented in this article reports the characteristics of tides at Kochi backwater (KB) system on the southwest coast of India based on in situ time-series tidal measurement results. The present tidal measurements from eight stations covering the entire KB indicate that the upstream boundary regions of KB and its inter-mouth region exhibit prominent fortnightly tidal character because of the presence of Msf tidal constituent (14.76 day period) whose amplitude is relatively larger than what is generally found. The theme of this article is primarily about the large Msf tides observed at a few stations in KB, which is a new finding in these areas. Large Msf tidal constituent has been reported from relatively fewer sites in the world. In the Pacific Ocean, Msf tide has been identified at Canton Island 1 . In the Atlantic Ocean, alongshore propagating large Msf tide has been observed at a few locations along the northern coast of the Gulf of Guinea