Harvesting nature’s bounty: leveraging flood water diversion for sustainable agriculture and pisciculture in wetlands

Abstract

Flood-prone regions in the Himalayan foothills, such as Assam’s Lakhimpur district, India frequently experience monsoonal inundation, sedimentation, and dry-season water scarcity. This study presents the first of its kind nature-based floodwater management framework by utilizing seven identified wetlands for floodwater diversion, storage, and multipurpose reuse. Wetland selection was carried out using Sentinel-2 imagery; applying criteria such as ≥ 10 ha surface area, ≤ 3.5 km proximity to rivers, and location within moderate or lower flood hazard zones. Wetland storage capacities were estimated using 1 m LiDAR-derived DEM, incorporating enhancement through 2 m excavation and 2.55 m-high embankments (top width: 3.51 m; base width: 8.65 m). Hydrological modeling using HEC-HMS demonstrated high accuracy (NSE: 0.859 to 0.891), simulating peak discharges of 1012 m³/s (Ranganadi) and 120.4 m³/s (Singra). Least-Cost Path analysis was used to identify gravity-driven diversion routes, enabling the design of unlined canals (depth: 2 m; base width: 11 m), with estimated construction costs between ₹1.49–2.49 Crores. Sediment load assessment, based on CWC guidelines, revealed high sedimentation in the Ranganadi (11,085 tons/day) and minimal in Singra (176 tons/day), with site-specific check dams (10 for Ranganadi and 6 for Singra catchment) proposed for mitigation. The potential of using stored floodwater during lean seasons was evaluated through CROPWAT 2.0, showing irrigation feasibility for up to 1,980 ha of land with crops such as potato, maize, and cabbage for both catchments, and support cage pisciculture, generating over ₹34,000 per cage/year. This integrated approach offers a scalable, cost-effective model for flood mitigation, water reuse, and rural livelihood enhancement in sediment-rich Himalayan catchments.