An Engineered and Sustainable Solution for Flood and Sediment Management in Kosi River, India

Abstract

Flooding is one of the most devastating and frequent natural hazards in the Indian subcontinent. In India, Bihar is one of the most flood prone states. Floods hit the state almost every year and causes enormous loss of lives, property, agriculture and infrastructure. Bihar has about 6.88 million hectares of flood prone area which is about 73.06% of its geographical area. The Kosi river is the most unstable river in Bihar and known as the “Sorrow of Bihar” because floods in this river cause huge destruction almost every year by its course changing tendency in the plains of North Bihar. It is one of the largest tributary of the river Ganga originating from Himalayas in Tibet and joins the Ganga in Bihar after flowing through Nepal. Majority of the drainage area of this river (almost 85 %) lies in Tibet and Nepal while only 15% lies in Indian Territory. The river carries huge amount of sediment with flow every year (about 120 million m3/Year) which primarily causes change in the morphological behaviour of the river. Even after the adoption of several measures, mostly grey infrastructure for the flood management in the Kosi river, the flood devastation in the region is still continued. The grey infrastructure approach gives a false sense of security and it also results in many unintended negative consequences. The present paper analyses the problem of flooding in the Kosi river basin; explores the feasibility of innovative and green infrastructure based sustainable solutions. Considering the prime issue of sediments in the Kosi, a novel concept of detention cum siltation ponds have been proposed. These ponds require hardly 7.84-13.54% of the drainage basin of Kosi in India. The proposed detention cum siltation ponds with other green infrastructure measures for the flood and sediment management in the river basin have overarching benefits. The environmental and economic sustainability aspect adds a great value to feasibility of the proposed measures.