Sediment management in reservoirs: A comprehensive review of processes, trapping efficiency, flushing techniques, and bypass solutions

Sedimentation in dam reservoirs is a major challenge in water resources management, reducing storage capacity and impairing hydropower generation, flood control, and water supply. This study presents a comprehensive review of sedimentation processes in reservoirs, the governing factors influencing sediment deposition, methods for estimating incoming sediment loads, and their impacts on dam performance. The Dez Dam in Iran is examined as a case study, revealing a loss of approximately 20% of its initial storage capacity over 60 years, with an average annual sedimentation rate exceeding 15 million m 3 . Sediment management strategies are categorized into preventive measures (watershed management and sediment trapping) and corrective measures (pressure and drawdown flushing, sediment bypass tunnels, dredging, and density current venting). Trap efficiency is strongly influenced by hydraulic and sediment characteristics, and techniques such as flushing and sediment bypass tunnels (SBTs) have successfully restored reservoir capacity in documented cases, including dams in Japan, Switzerland, and the Sefidrud Dam in Iran. Despite these advancements, challenges such as hydro-abrasion in tunnels and operational constraints persist. This study emphasizes the need for integrated approaches, advanced modeling, and sustainable sediment management practices to extend reservoir lifespan. The findings of this review provide practical guidance for reservoir managers and engineers in selecting appropriate sediment management strategies based on reservoir characteristics, thereby supporting more sustainable dam operation and long-term storage preservation. • Comprehensive review of sedimentation processes in reservoirs to protect dam safety and extend operational life. • Controlling sedimentation through trap efficiency optimization, flushing techniques, and sediment bypass tunnels. • Detailed case study of Dez Dam in Iran, highlighting high sedimentation rates and management challenges. • Evaluation of preventive and corrective strategies with real-world examples from Iran and worldwide. • Recommendations for sustainable, integrated sediment management using advanced tools and monitoring.