Engineering Management of River Dredging for Flood Protection: An AI-Assisted Socio-Hydrodynamic Study of the Ghaghara-Saryu Basin, Uttar Pradesh, India

Abstract

Riverbank erosion remains a persistent and serious threat to rural communities and agricultural land in the Gangetic plains of India, where highly active alluvial rivers cause continuous lateral migration and bank failure during monsoon seasons. This study evaluates the effectiveness of sectoral dredging as a soft-engineering river training approach through two field interventions in Uttar Pradesh: the Ghaghara River at Village Sirauli Gung, District Barabanki, and the Saryu River at Village Bahadurpur, District Gonda. Pilot channels, referred to as cunettes, measuring 3.8 km and 3.9 km in length and 45 metres in width, were excavated to redirect the river’s main current away from vulnerable concave banks. A hybrid bank stabilisation system combining Geotubes and Balli piling was deployed to induce siltation in abandoned reaches and reinforce the bank toe. Data acquisition integrated LiDAR surveys, high-resolution UAV photogrammetry, bathymetric mapping, and 2D hydrodynamic modelling using HEC-RAS to validate hydraulic performance and sediment transport behaviour. Discharge calculations based on Lacey’s Regime Theory confirmed that the standard 45-metre cunette can convey approximately 472.63 m³/s, while the widened 100-metre channel section achieved a capacity of approximately 1,458 m³/s. Post-intervention numerical simulations and field observations confirmed a significant reduction in near-bank flow velocity to 0.8–1.2 m/s and boundary shear stress to below 15 N/m². Economic evaluation yielded Benefit-Cost Ratios of 1.41:1 for the Ghaghara reach and 1.35:1 for the Saryu reach. In total, 13.46 lakh cubic metres of dredged material were reused in situ for embankment reinforcement and land reclamation, consistent with the National Framework for Sediment Management-2022. The interventions secured the livelihoods of approximately 22,000 residents, protected 8,000 hectares of fertile agricultural land, and generated 15,288 temporary employment days for local communities. These findings present sectoral dredging as a scalable, cost-effective, and ecologically responsible model for flood risk reduction in dynamic braided river systems.