Mud flows impact on the mountain rivers channel processes is discussed, the processes features proved to be different within the zones of mudflows formation, transit and deposition, the channel morphology depends on the form of the mudflow deposits. After mudflow flood creates a primary channel in the mudflow deposits, later the channel undergoes a slow transformation by the stream which results in sequential changes of channel types according to changes in the stream slope and discharge. No correlation has been found between alluvium size and channel slope in mudflows while the correlation is qiute close in the channel transformed by water course. Mudflows account also for the lack of correlation between dimensions of the pavement on one hand and the fluvial layer on the other.