Abstract: The “Comprehensive Plan for the Yellow River Basin (2012-2030)” outlines that during the planning period, the Yellow River will primarily use the Qingshuigou Channel to stabilize its flow. Once the Qingshuigou Channel is no longer in use, the Diaokou Channel will serve as the backup. We investigated the characteristics of sediment and water dispersal into the sea after the river course switch to the Diaokou Channel, considering the current channel dynamics and focusing on the water and sediment regulation (WSR) period, a key phase of river management. Using a validated three-dimensional numerical model, we simulated and analyzed the salinity, suspended sediment concentration, and estuarine dynamics during WSR for both channels. Results reveal that: (1) although the overall trends of coastal flow systems along the two channels are consistent, local flow fields are different; (2) the dispersion of plumes and suspended sediments responds consistently to the changes in water and sediment flow during different stages of WSR. Due to estuarine topography and shoreline influences, the Diaokou Channel showed a significantly larger dispersion range; and (3) the switch of the channels will lead to rapid changes in delta evolution: the modern estuarine delta will experience erosion and retreat, while the Diaokou delta will undergo rapid land buildup. Moreover, outcome of the modelling suggests that, due to the shallower depths and gentler slopes in the Diaokou Channel, the rate of land buildup may surpass that of the current channel in a short term under similar conditions.