Dredging and Siltation Study in the Gulf of Khambhat

The Gulf of Khambhat is an inverted funnel-shaped indentation on the Arabian Sea of India. The maximum water depth of Gulf of Khambhat region is 35 m. Tidal range is high with semi-diurnal type. The current is very strong with magnitude of 2.5 m/s which occurs during mid-tide. Gulf of Khambhat (21° 03′ 41.49″ N, 72° 25′ 18.26″ E) receives enormous sediment from the discharge of three major rivers: Narmada, Tapti, and Sabarmati. The shoal movement as well as shoal enhancement has been observed in this region. At certain locations, the depth of water is reduced from 20 to 2 m in ten years. The dredging at an area of about 300 by 300 m from −2 to −20 m and disposal in deep contour is proposed, and the siltation rate in the dredge area and disposal area is studied. MIKE 21 HD flow module is used for tidal propagation, and for the siltation analysis, MIKE 21/3 integrated module is used. Desk studies are done analyzing satellite imageries. The results of analyses indicate that the sediment flow at dredge location is dominated by tidal current and the river flow is having no significance at the site which is located 24 km from confluence point. It can be observed that the bed level accretion works out to 180 cm per year. The disposal location was also identified where the siltation rate is assessed as 7 cm per year. The details of studies are furnished in the paper.