Looking into the claim of siltation, I found
this paper on sediment transport in the Ganges-Brahmaputra system, which mentions a 1985 study by Emmel and Curray that "found no evidence of recent sediment accumulation on the Bengal deep sea fan". Apparently half the sediment carried by those rivers never leaves the river mouth, and most of what does gets swept off into a trench known as the "Swatch of No Ground" and carried out to deeper waters.
This paper describes a study of a sediment core taken from the Bay of Bengal, showing 43cm of accumulation attributable to the Holocene period, which covers the last 12,000 years or so. Needless to say, this does not support an accumulation rate that would cause a problematic level of sedimentation within the last two months.