Abstract: In order to reveal the main influencing factors and characteristics of deltaic channel evolution following avulsion,numerical experiments were conducted by a fully coupled hydro-sediment-morphodynamic model with the focus on the “wandering-braiding-merging” processes in schematic fan deltas.Results show that the initial undulating topography is critical for reproducing the wandering patterns in the early stage.The morphological evolution characteristics and time scales of channel development are highly related to the deltaic slope as well as the flow and sediment boundary conditions.A small bed slope and a low discharge favor the wandering processes,while a large bed slope and a high discharge favor merging and routing processes under steady flow condition.Channel erosion is dominant at low sediment concentration,whereas channel erosion and levee-lip accretion occur simultaneously at high sediment concentration.Enhanced tidal force at downstream boundary may accelerate the flow routing processes,whereas the seaward deposition on the subaqueous slope shows an opposite effect.Under unsteady flow conditions,the early stage is characterized by the development of main channel and branches at the flood season but only wetted main channel at the dry season; while the later stage is featured by a single main channel all the time,which is maintained by the flood discharge.