The river known as the 'Sorrow of Bihar' is the:

The Kosi river is called the "Sorrow of Bihar" because of its frequent, devastating floods and its tendency to shift its course suddenly, causing great loss of life, crops and property in north Bihar.

Course of the Kosi:

• It is formed in Nepal by seven Himalayan streams; it is therefore also called the Saptakoshi.
• It flows through Nepal and enters Bihar near Bhimnagar.
• It joins the Ganga near Kursela in the Katihar district of Bihar.
• Its basin includes some of the highest mountains in the world, such as Mount Everest and Kangchenjunga.

Why the Kosi causes such damage:

• It carries a very heavy load of silt and sand from the steep, young Himalayas.
• When it reaches the flat plains of Bihar, it slows down and deposits this sediment, raising its own bed.
• As a result, it frequently overflows its banks and shifts its channel.
• Over the last 200 to 250 years, the Kosi has moved westward by about 120 to 150 km, laying down a huge fan of sand and silt, called the Kosi megafan.

The 2008 Kosi flood:

• In August 2008, the Kosi breached its eastern embankment at Kusaha in Nepal and shifted its course, flooding large parts of north Bihar.
• Millions of people were affected, and it was declared a national calamity.

Flood control efforts:

• The Kosi Project, under an agreement between India and Nepal in 1954, built the Kosi Barrage at Bhimnagar (in Nepal near the border) and embankments along the river.
• However, embankments have not fully solved the problem, as silt builds up within them.
• A high dam on the Kosi in Nepal has long been proposed for flood control and hydropower.

Other "sorrows":

The Huang He (Yellow River) is called the "Sorrow of China" because of its destructive floods.

Why not the other options?

• ✗The Gandak, Bagmati and Burhi Gandak are other rivers of north Bihar, but the Kosi is the one known as the Sorrow of Bihar.