Sediment transport investigation near Sagar Island in Hooghly Estuary,Kolkata Port,Kolkata

A radiotracer investigation was carried out in Hooghly Estuary at Kolkata Port Trust, Kolkata to examine the suitability of a dumping site for dredged sediment located at south of shipping channel. Scandium-46 (300 GBq) as scandium glass powder having the particle size distribution ranging from 40 to 100 μm was used as a radiotracer. The tracer was injected onto the seabed at the site using a remotely operated injection system and its movement was tracked using waterproof scintillation detector. The tracer concentration curves were plotted for different trackings. From the tracer concentration curves iso-activity contours were plotted and parameters such as general direction of movement on seabed, transport velocity, transport thickness and bed load movement rate were determined. The analysis of data indicated that the sediment predominantly moves towards north-east direction during the period of the study and coming in the shipping channel. Based on the investigations, it was found that the proposed site is not suitable for dumping the dredged material, as the movement of sediment is towards the shipping channel.