Sediment flushing rapidly remobilizes large volumes of deposited sediments into downstream channels, triggering abrupt alterations in redox conditions and nitrogen cycling. However, its impacts on riverine nitrous oxide (N₂O) emissions and underlying mechanisms remain poorly understood. Here, field observations during two flushing events of the Xiaolangdi Reservoir in the Yellow River were integrated with variation partitioning analysis, Lindeman-Merenda-Gold relative importance analysis, and partial least squares structural equation modeling to quantify emission dynamics and controls. Sediment flushing generated a pronounced asymmetric N₂O emission pulse, with fluxes increasing from 0.62 mg m^-2 d^-1 pre-flushing to 1.64 mg m^-2 d^-1 during flushing (2.7-fold), followed by gradual recovery to 1.11 mg m^-2 d^-1 post-flushing. This response was driven by particle-microinterface coupled nitrification-denitrification, where suspended particles enhanced redox stratification, substrate availability, and microbial functional restructuring, enabling spatially coupled nitrogen transformations. Particles did not directly drive N₂O emissions but acted as indirect regulators of biogeochemical conditions. Monte Carlo simulations estimated cumulative emissions of 5.1 × 10³ kg N₂O per sediment flushing event, revealing a substantial short-term emission hotspot. These findings identify sediment flushing as a previously underappreciated trigger of episodic riverine N₂O pulses and highlight the need to incorporate such engineered disturbances into greenhouse gas inventories of regulated rivers