Question

The Kosi river is known as the “Sorrow of Bihar”. Why?

Answer 1

Hint Kosi river floods Bihar annually destroying crops, property and lives. It is loaded with heavy sediments and very often changes its channels causing overflowing and flooding.

Complete Step by Step Answer Kosi is a transboundary river. It flows through Tibet, Nepal and India. After being joined by several tributaries it starts to be called as Saptakoshi by the time it enters India. It is 720 km long and drains an area of about 28,800 sq miles. The river Kosi is said to be very unstable, very often changing course and causing devastating floods. The instability is attributed to the large amounts of silt it carries during the monsoon season. Soil erosion and landslide in the upper course of the river produce one of the highest silt yields in the world. This is the reason it is referred to as the “Sorrow of Bihar”.
On an annual basis, it’s flooding affects an area of 21,000 km square of fertile land causing immense damage to the rural agricultural economy. The average discharge or water flow of the river is 2,166 cubic metres per second, however, during the monsoons, it increases as much as 18 times. The river has many intersecting channels which aren’t solidified and therefore shift laterally from time to time causing floods. In the devastating floods of 2005 in Bihar, 95% of the water the river carried shifted into a channel it has not occupied for over 100 years affecting thousands of people. Every year the Kosi destroys the state.

Note Kosi originates in Tibet and flows through three countries before depositing itself into the Bay of Bengal. It is a highly sedimented river and frequently changes the course. Since Kosi floods Bihar every year, it is given the title of “Sorrow of Bihar''.