Drainage System of India: Which river is known as the 'Sorrow of Bihar'?

The Kosi River is called the 'Sorrow of Bihar' due to its tendency to frequently change course and cause devastating floods in Bihar. The river carries enormous amounts of silt from the Himalayas, which raises its bed and causes it to breach its banks and change direction unpredictably. This has led to widespread destruction of crops, property, and displacement of populations in Bihar over the centuries.