Photograph taken in 1983. Bank erosion as a source of material for debris- flow formation. Photographs taken August 1984. Note man in center of picture. Flow is from left to right.
Flow is from left to right.
The influence of ground water is another factor in the formation of debris deposits. Ground water recharged by precipitation or snowmelt, and perched on less permeable eruptive deposits and seeping from the pyroclastic deposits, may cause slump failure and mass movement downslope into a stream channel. A number of observers, however, have reported that ice flows and flood flows on Mud Creek have lodged in the canyon as a result of ice or debris blockage. The eyewitness accounts in the following paragraph provide the best evidence of the relation between channel blockage by the breakup of glacial snow and ice, formation of temporary impoundments during flood flows, and the subsequent occurrence of debris flows. From time to time parts of the steeper eastern wall of the Mud Creek canyon collapse into the gorge, forming temporary dams behind which the water is impounded until able to overflow and carry away the obstacle.