THE CLIMATE CHANGES IMPACT ON THE RIVER CHANNELS AND VALLEY BOTTOMS IN THE EASTERN SIBERIA

Morphology and morphometry of the buried and contemporary valleys bottoms in two mountain placer districts of the Eastern Siberia were analyzed. The Lena district is located within Vitima–Patom plateau on the right bank of the Vitim river, the Kular one is located in the interfluve of the rivers Yana and Omoloy. Using the topographic maps and paleogeomorphological schemes compiled on the basis of drilling data, we defined the morphodynamic types of channels, morphometric parameters (the width of the bottom step, the bend deflection of the meander) and the morphology of the bottoms of the buried and modern valleys. The patterns of their change were traced during several geological periods with different climatic conditions specified by paleolandscape method.

Morphological and morphometric characteristics of the bottoms and beds of mountain valleys depend on the altitudinal zonation. In the mid-mountain relief of the Lensky district, even at the considerable changes of climate, morphodynamic type of riverbed, bottom morphology and morphometric parameters of buried and modern valleys are practically identical. More significant is the impact of climate change on the bottoms of valleys and channels in the Kular district. Here, in the relief of low-mountains and plateaus, with a cooling of the climate and the decrease of rainfall, the width of the bottoms of the modern valleys is significantly reduced compared to buried valleys, formed in warm humid climate of the Paleogene.

Using the results of long-term observations on the mountain river Bzyb (Caucasus) the mechanism underlying these differences was revealed. It is associated with the intensity of deformation of bed forms depending on the nature of the relief terrain and water availability.

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