Study on Stability of Eden Navigational Channel in Hooghly River Estuary

Abstract

Hooghly estuary is a complex dynamic estuary facing dredging maintenance and navigation-related problems due to the high rate of sediment load brought by the Hooghly River. The present study is to investigate the hydrodynamics and morphodynamics of the Hooghly estuary, with specific reference to stability of Eden navigational fairway and permanent operation of the channel as a possible main navigational route to HDC in the place of Auckland channel from the Bay of Bengal. Impact of stoppage of dredging at Auckland bar on the other channels (Eden and the Rangafalla channel that connect to Kolkata Dock System, KDS) is investigated. Simulations involving different scenarios like Auckland channel dredged and non-dredged conditions are considered to investigate the stability of the Eden channel and also to address the aspects relating to the maintenance of other channels. In the study, for the Auckland open condition, the predicted siltation levels are of about 8–12 cm over Auckland and about 4–8 cm over Eden bar, over 15 days of simulation. For Auckland closed condition and for Auckland with two tracks, the results indicate a marginal reduction in siltation over the entire Eden area, and it is also observed that the siltation in Jellingham and Haldi River confluence is significantly reduced. For the monsoon conditions in all the above scenarios, the results, as per the siltation patterns and as per the siltation levels on the edges of the channels, indicate that there will be a marginal increase in siltation, by about 20% when higher silt load is considered. The study suggests that Eden channel could continuously be used with little dredging in the longer term of more than 5 years with monitoring and realignment of the channel to cater for movement of sandbars. Further, non-dredging of Auckland channel may not have any bearing on the operation of Eden, Jellingham and Rangafalla channels.