Why does the Brahmaputra River’s main channel in Assam tend to lie near its southern bank?

In the Assam Valley, the deep channel of the Brahmaputra River tends to lie closer to its southern bank because of the influence of its tributaries. The northern tributaries, which descend from the rain-soaked Himalayan slopes, carry a significantly heavier silt load than the tributaries that cross the older, harder plateau rocks to the south. This massive influx of sediment from the north effectively pushes the river's main channel toward the southern bank.1