Sustainable Silt Management in the Lower Kosi River, North Bihar, India: Demand Assessment, Investment Model and Socio-Economic Development

Abstract

The Kosi River, draining through Nepal and north Bihar, India, has been known for excessive sediment (commonly called silt) deposition—a primary cause of several hazards. However, there are still no good estimates of the volume of silt accumulated in the Kosi River channel, which makes removal and utilization of silt a major challenge, both technically as well as economically. In this work, we first present a novel method to estimate sediment volume on a reach scale using hydrological and channel planform data mapped from satellite images. We then identify various commercial uses of the Kosi River sediments such as embankment construction, backfilling, land reclamation, landscaping, agricultural applications, industrial applications, and geotextile silt walls. In consultation with various stakeholders, backfilling and embankment construction were identified as potentially the best solutions shortlisted for the development of a business case and investment model. Therefore, we prepared an investment model based on economic viability, cost-to-benefit ratio, and stakeholder consultations for two districts. We performed a SWOT analysis by breaking down the opportunities and risks into political, economic, social, technological, environmental, and legal (PEST-EL) factors to identify the pros and cons within the sector and of the ecosystem in which the stakeholders operate.