Simulation result shows that the deltaic beach of Songzi River aggrades in the form of swallow tail and self-balance adjustiment in which master stream aggrades first and then branch streams. Flood period is the stage for the beach to develop.The beach roots in flood period

then it gets thinner in medium water level

and is exposed in low-water.River axis tends to the central line in high water level

it flexes in low water level

and this is supposed to be the controlling factor for the formation and evolution of Lujiahe beach.The lujiahe beach turns to be a wide point bar of concave bank in flood periods

and becomes a channel bar in medium and low water periods.Fenghuangtan and Jiangkouzhou Neaches are both dominated by cove pattern and the boundary conditions of the river channel.The Fenghuangtan beach would aggrade in flood periods while Jiangkouzhou would mainly be scoured.It means that the former would grow bigger and the later would decrease and subduce.