Explanation: In the Himalayan reaches, the course of these rivers is highly tortous, but over the plains they display a strong meandering tendency and shift their courses frequently.

• River Kosi, also known as the ‘sorrow of Bihar’, has been notorious for frequently changing its course.
• The Kosi brings huge quantity of sediments from its upper reaches and deposits it in the plains. The course gets blocked, and consequently, the river changes its course.

Source: NCERT