Why does the Brahmaputra River carry much more silt after entering Assam?

The Brahmaputra River carries a significantly heavier silt load upon entering Assam because of the influence of its northern tributaries. While the river's waters are clear in Tibet, the northern tributaries that flow down from the rain-soaked Himalayan slopes possess a much higher volume and speed, which results in a substantially heavier sediment load compared to the tributaries originating from the hard rocks of the plateau to the south. These silt-laden northern tributaries are so powerful that they effectively push the river's deep channel toward the southern bank.1