Abstract— <p>It has been established that the formation of the relief of the Lower Amur region is due to the long history, differentiated tectonic movements, climatic features, and a complex permafrost pattern. Despite the low elevations of the mountain ridge tops, numerous traces of Quaternary glaciation, relict permafrost forms, and active manifestation of modern cryogenic processes on the highest peaks of the mountains have been found there for the first time. Data on the distribution and occurrence of permafrost strata within the Udyl’-Kizi and Evoron-Chukchagir lowlands point to their relict nature. Specific features of erosion-accumulative processes of mountain taiga rivers in the monsoon climate zone, caused by significant seasonal unevenness of the runoff, have been revealed. It is shown that the Amur River bed, crossing vast lowlands, forms complex floodplain-channel branches, in which the water flow and sediment deposits are being constantly redistributed between the branches. An assessment is given of the role of uneven floodplain sedimentation played in the emergence of various forms of mesorelief. The features of the formation of the floodplain and floodplain lakes under conditions of a deficit of traction load within the Lower Amur Lowland are revealed.</p>