Logjams on rivers, their channel-forming and environmental role
Formation of logjams and their channel-forming role are described basing on published data about forest rivers of Russia, Europe and North America as well as the results of investigation of more than 50 rivers of the Kamchatka Peninsula. Spatial patterns of logjams distribution are revealed. The largest and the most frequent logjams are typical for the rivers of submountain regions. Logjam formation is governed by channel gradient and river size, as well as the intensity of log input to them. Characteristics of logjams for unexplored rivers could be predicted on the basis of a multiple regression model using the parameters of channel and floodplain as predictors. Within the river continuum logjams are most typical for semi-mountain and mountain rivers with well-developed alluvial forms. By blocking the rivers logjams become an active factor of restructuring this type of channels. Changes in flow hydraulics and channel morphology predetermine the influence of logjams on the structure of aquatic biotopes.