Effects of width channel increase in the formation and evolution of sandbars (riffles)
Keywords:channel processes, morphodynamic type of channel, morphology and dynamic of riffles and sand bars, types of riffles, river navigation, Ob River, Northern Dvina River, Ganges River
The paper presents the morphology and the long-term regime of riffles formed in the local widening of river channels: the Ob, the Northern Dvina, and the Ganges. Navigation maps for the last 120 years, detailed channel plans for the last 60 years as well as satellite images from 1977 and further were used to study the long-term regime of riffles. Five types of riffles are distinguished in the widening of river channels. Each type of riffles has a specific regime and a characteristic period of long-term reformations, with both the regime and the period being controlled by local surroundings of riffles. The presented study of the long-term regime of riffles and its relationship with local morphological conditions could be useful to optimize dredging works and, as a consequence, help to preserve optimal conditions of waterways.