CHANGES OF LOWER VYCHEGDA RIVERBED RELIEF IN THE COURSE OF DREDGING AND AFTER ITS FINISHING

Abstract

The paper discusses the problems of a large river morphodynamics in the course of artificial channel straightening and after that, the Lower Vychegda taken as an example. There are dune bedforms (riffles) of various size and morphology in its channel. During the period of intensive dredging many riffles were completely destroyed, others became morphologically simpler and the dynamics of their periodic reformations became simpler too. Since 1991 artificial dredging almost ceased. Some of the riffles have returned to the natural state while others have kept the human induces mode of channel deformation and relatively larger depths. At downstream ends of straight channel sections the new very shallow riffles were formed, being of maximum for the Vychegda wavelength and not eroded during the low water level period. These riffles did not exist under natural conditions prior to dredging. They formed due to irreversible anthropogenic changes of channel deformation regime on upstream riffles.