Abstract:
In this preliminary phase of the study, a prima-facie analysis was conducted to get an insight into the basic causes of insufficient navigation draught in the six locations on the Ganga river falling between Varanasi & Farakka.
This initial preliminary study phase has brought out the occurrence of channel flow bifurcation and shoal formation. behaviour due to heavy sedimentation at these sites as the root cause of navigation bottlenecks. Stream bank erosion and heavy sediment deposition due to inadequate transport
capacity could be identified as major underlying causes leading to channel instability and resultant reduction in draught.
Basic prerequisite to development of reasonably durable navigation channel in the Ganga river can be cited as effective sediment management both in the stream as well as in the watershed areas and effectively control the predominant channel instability processes to achieve concentration of stream flow to generate desired draught. The problem of reduced draught in several locations of the Ganga river can be primarily attributed to channel instability phenomenon triggered by heavy sediment inflows and channel widening process due to erosion which invariably cause erratic drifting of the thalweg channel.
From the preliminary analysis of the satellite data of the Ganga river along with available information on LAD, discharge etc., it could be surmised that in the identified six locations the draught reduction problem is primarily an off-shoot of the stream flow division into multiple channels with resulting braided configuration. This river behaviour of stream channel bifurcation in the Ganga is actuated by bank erosion accompanied with random deposition of sediments in heaps during the receding stages of flood flows when sediment transport capacity in the stream sharply declines.
In the above backdrop, the strategy to develop cost-effective durable fairway in the Ganga river warrants adoption of suitable flow channelisation measures to be supported by commensurate river sediment management along with compatible stream bank protection system in place to provide the required stream bank stability.
