Channel processes and floodplain formation under conditions of steady alluviation of the valley

Abstract

Lower reaches of some large rivers (such as Amur, Amazon etc.) are characterized at present with alluviation which leads to formation of inner deltas, near-floodplain lakes, increased thickness of floodplain faces of alluvium etc. In such a rivers the floodplain soon comes to the dynamic equilibrium state, after that its elevation above the channel remains constant, the morphology, dynamics and alluvium sequence differ essentially from those observed in the downcutting rivers. In the Amur valley the length of the alluviation zone is up to 1200 km and the rate of sedimentation averages 0,56 mm per year. Some differences in the floodplain dynamics are established between plain and mountain segments of the Amur valley.