Migration of Tidal Inlets of Chilika Lagoon, Odisha, India -A Critical Study

Chilika Lake, Asia’s largest brackish water lagoon situated on the East coast of India is separated from Bay of Bengal by sand bars and connected with the sea by a series of tidal inlets. The inlets are maintained by discharges of inflowing streams during monsoon and by tides and ebb tides during non-monsoon. Imbalance in ingress and egress of sediment due to their continuous exchange between sea and the lagoon causes sedimentation of lagoon. Varying inflow, littoral drift and such other factors influence sedimentation. It results shifting mouths (inlets) continuously. Some mouths closed and some opened at various locations of the spits of the lagoon in course of time. This governs the inflow and the outflow characteristics and hence the salinity. A barrage at Naraj on Kathajodi, a major distributary of the river Mohanadi, and an artificial channel connecting the mouth of the Lagoon from Magarmunha to Bay of Bengal were provided to regulate the inflow. This phenomenon has been studied critically considering long history, geophysical parameters, terrestrial events and human interventions etc. Since the activities are location based, exact hydrodynamics has not yet been established for formation, closure and shifting of the tidal inlets. The present study deals with mouthing activities with time, the mechanism involved and effect of Naraj barrage on closure, migration and opening of new tidal inlets in Chilika Lagoon. The possible effects of celestial bodies and sun-earth geometry, which were unnoticed so far, are studied. Key wordsChilika Lagoon, Tidal inlet, Shift, Barrier-spit, littoral drift