The Ganges Delta And The Hungry Tide

Amitav Ghosh is his book The Hungry Tide  evocatively describes the Ganges -Brahmaputra delta, the place where these mighty rivers change form as in from a one major active meandering channel into many entangled entities:

In our legends it is said that the goddess Ganga's descent from the heavens would have split the earth had Lord Shiva not tamed here torrent by tying it into his ash-smeared locks. To hear this story is to see the river in a certain way: as a heavenly braid, for instance, an immense rope of water, unfurling through a wide and thirsty plain. That there is a further twist to the tale becomes apparent only in the final stages of the river's journey - and this part of the story always comes as a surprise, because it is never told and thus never imagined. It is this : there is a point at which the braid comes undone; where Lord Shiva's matted hair is washed apart into a vast  knotted tangle. Once past that point the river throws off its bindings and separates into hundreds, maybe thousands of tangled strands.

Until you behold it for yourself, it is almost impossible to believe that here, interposed between the sea and the plains of Bengal, lies an immense archipelago, stretching for almost three hundred kilometers, from the Hoogly River in West Bengal to the shores of the Meghna in Bangladesh. 

The islands are the trailing threads of India's fabric, the ragged fringe of her sari, the achol that follows her, half-wetted by the sea. They number in the thousands, these islands; some are immense and some no larger than sandbars; some have lasted through recorded history while others were washed into being just a year or two ago. These islands are the rivers restitution, the offerings through which they return to the earth what they have taken from it, but in such a form as to assert their permanent dominion over their gift. The rivers channels are spread across the land like a fine mesh net, creating a terrain where the boundaries between land and water are always mutating, always unpredictable.

The delta and its front end - the sediment fan -  that is present below sea level in the Bay of Bengal is essentially made up of Himalayan sediment worn down by the many rivers and redeposited in the Bay. A pile of sediment more than 10 km thick have accumulated since the early Cenozoic.  Image below shows the Ganges Brahmaputra delta and the region called the Sunderbans named for the mangrove forests that grow on the thousands of sandbars and islands.