CONSTRUCTION OF COFFER DAMS FOR FIGHTING FEROCIOUS KOSI

Abstract

Kosi River is an alluvial stream flows through Shivalih hill in Nepal & Tibet (China).It comes on the plane at Chatra about 45km North of Indo –Nepal border. There is a barrage on Indo-Nepal border at Bhim Nagar, Birpur in Supaul District of Bihar, Inia.Kosi River was devastating before it was tamed.In eighteen century it was flowing near Purnea town and shifted westward, now flowing near Supaul. It shifted about 120 km westward in 275 years. 
This river is formed by the confluence of seven small streams flowing through Tibet a Nepal. These seven streams are – Indravati, Tamar Kosi, likhu Kosi, Doodh Kosi, Arun Kosi and Tama Kosi. It travels about 729 kms from source to confluence with Ganga in Kurshela.
Some hydraulic particulars of the rivers were:- 
Design Discharge of Barrage -9, 50, 000 cusec
Max Discharge observed on 5^th Oct 1968- 9,13,000 cusec( after construction of barrage)
Total No .of Gate- 46
On 16^th Aug, 2008 there was a breach in eastern Kosi Afflux Bund of river Kosi In Nepal. The location of breach point was 13 m upstream from barrage. The river was flowing in three streams. Technical experts decided to construct three coffer dams to retrain the three streams into one and bring back the river river in main channel. it was on 24^th Janurary,2008 on which the main flow of Kosi was stopped through bridge and diverted towards barrage through pilot channel. The barrage again stated functioning.