Modeling Sediment Deposition in Rivers Through Computational Fluid Dynamics

Abstract

Sedimentation in irrigation canals significantly reduces operational efficiency and agricultural productivity in tropical monsoon regions. This study applied three-dimensional computational fluid dynamics (CFD) to analyze sediment deposition patterns in the Pakal River affecting the Bareng Irrigation District, East Java, Indonesia. The integrated approach combined HEC-HMS watershed modeling with ANSYS Fluent CFD simulation to evaluate sedimentation under design flood conditions (20-year return period).Design discharge was determined as 30.4 m³/s using the Modified Haspers-Weduwen method. CFD simulation revealed severe deposition totaling 2,200 m³ per design event, distributed across four distinct zones driven by weir backwater effects, bend circulation, channel expansion, and insufficient transport velocity. Model validation demonstrated strong performance (NSE = 0.84 for velocity, 81% spatial agreement for deposition). A critical finding is that low design discharge creates widespread subcritical flow conditions, resulting in more severe deposition than higher flows.The validated methodology provides a replicable framework for evidence-based sediment management in resource-constrained irrigation systems across tropical regions, with broader applicability to climate adaptation planning and infrastructure resilience assessment.