Sediment-flushing equilibrium downstream of tide gates in a coastal region: Findings from a 36-day prototype water-diversion experiment

The Lixiahe Region, a coastal area with tide-gate-regulated port channels vulnerable to sedimentation impacts. Investigating sedimentation challenges induced by tide gates in port channels and testing a sediment management method combining water transfer strategies (informed by mountainous reservoir practices) with optimized gate operations through a 36-day prototype experiment. The study quantified critical water volumes required to achieve sediment-flushing equilibrium and identified optimal timing for tide gate operations, providing actionable thresholds for balancing sedimentation and hydraulic efficiency. Furthermore, it demonstrated that coordinated water transfer (inspired by mountainous reservoir management) and adaptive gate operations outperform conventional dredging in mitigating sedimentation while reducing operational costs and ecological disruption. Building on these findings, a transferable sediment management scheme was developed, integrating dynamic water allocation with gate control protocols. This framework was validated against decade-long operational data (2012–2021), revealing its adaptability to seasonal hydrological variability and long-term sediment dynamics. The scheme proposes actionable strategies, including pre-flooding water diversion to preemptively flush sediments and synchronized gate adjustments during tidal cycles, to enhance channel stability. These insights offer coastal regions with tide-gate systems a scalable, eco-sensitive alternative to dredging, aligning sediment control with sustainable water resource management under changing hydrological conditions. • A 36-day prototype water-diversion experiment addressed coastal sediment issues. • Combined water transfer and tide gate operations effectively managed sediment. • Water volumes and gate operations were identified for sediment-flushing equilibrium. • Actionable sediment management suggestions were provided for similar regions.