Hydrometric sensor-based monitoring and empirical modeling of sediment transport and river erosion dynamics in a bird feather-type watershed

Accurate sediment transport modeling is crucial for understanding river erosion dynamics, particularly in tropical watersheds with complex morphologies, such as those characterized by bird feather-type drainage systems. This study aims to improve Erwanto's empirical sediment load model by integrating hydrometric sensor data and water quality parameters, analyze spatial sediment transport and erosion characteristics, validate the calibrated model against bathymetric measurements, and develop conservation zoning based on sediment and erosion risks in the Bomo Watershed, Banyuwangi, Indonesia. Field monitoring employed portable hydrometric sensors to measure discharge, velocity, depth, TDS, turbidity, and temperature. The revised empirical models for suspended load (Qs), bed load (Qb), and total load (Qt) achieved high predictive performance with R values of 0.974, 0.957, and 0.964, and NSE exceeding 0.95. Validation using bathymetric-derived sediment yield on March 23 and 30, 2024, showed low MAE (0.29—0.42 ton/day) and excellent model efficiency (NSE = 0.954). Sediment transport analysis at the point placement measurement revealed deposition at the mid-cross-section (SDR = -0.31; E = 3.52 × 10⁻4 kg/m2/s), while Shields and Froude numbers confirmed localized transitions from stable to moveable bed and subcritical turbulent flows. Conservation zoning delineated Songgon (Upper Bomo) as a priority area due to its high erosion rate (> 2.46 ton/ha/year) and sediment load (> 400 m3/km2/year), while Sempu-Rogojampi-Wonosobo and downstream areas require runoff control and channel maintenance. This study demonstrates that integrating empirical models with sensor-based hydrometric monitoring and spatial mapping supports adaptive river erosion mitigation strategies in tropical watersheds.