Comparison of Formation Model and Channel Stability between Two Different Sorts of Multiple Channel River Patterns

In multiple channel rivers, anastomosing rivers as a new river pattern differing from anabranched and braided rivers have aroused much attention. Nevertheless, the difference between the anabranched and the anastomosing rivers is frequently ignored. Some researchers even think that they are of the same channel pattern according to channel planform. To explain their fundamental differences, this paper focuses on the multiple channel formation models of the two river patterns. Based on the study of the anabranched channel reach of Lower Changjiang River and the anastomosing Jingjiang distributaries, it is held that the anabranched multiple channel forms with appearance of one or more mid channel lands, which have two layers of sediments whose grains are thin and fine in the upper part and thick and coarse in the lower part, whereas the anastomosing multiple channel forms with appearance of one or more stable channels on the floodplain surrounded by coherent fine grained sediments. Anastomosing multiple channels show higher stability than anabranched ones.