Impact of tidal inlet and its geomorphological changes on lagoon environment: A numerical model study

Geomorphological changes of a tidal inlet are governed by complex interactions of tidal currents, waves and sediments. Tidal inlet(s) of the Chilika lagoon (19° 28′-19° 54′ N; 85° 06′-85° 35′ E) on the east coast of India and its geomorphological changes is linked to the contemporary phase of lagoon transformation such as sedimentation (from riverine discharge, land drainage and decay of macrophytes), choking of the outer channel, northward shifting, closing and opening of inlet(s). These transformations are responsible for decrease in salinity, depth and weak lagoon-sea interaction, which in turn are responsible for decline in water area, increase in vegetated area (macrophyte growth) and decrease in fish productivity. The present study investigates the past and present geomorphological changes of Chilika inlet(s) using historical data, satellite data, field observations and numerical modelling techniques. A numerical model was used to simulate the hydrodynamic conditions and salinity distribution in the lagoon for one inlet and multiple inlets and the results are calibrated with observations. The study suggests that tidal inlet(s) and its geomorphological changes have significant impacts on ebb and flood currents at the inlet(s), salinity distribution in the lagoon, sediment and water exchange between the lagoon and sea. Possible impacts of inlet(s) on ecological conditions of the lagoon environment are discussed.