Abstract
A forest in a small watershed at kamabuchi Experimental Forest was completely cut. After cutting all sprout-growth on the cleared area was cut back two times a year for five growing seasons. Then the vegetation was burn from the 6th year successive years without the former cutting of sproutgrwoth and the watershed became covered by thick miscanthuse. Three small landslides occured five years after the treescutting. Seven years after cutting total-layer avalanches occerred and their size increased from year to year.
The reason for this occurrence of avalanches may be attributed to the fact that : (1) the stumps were pressed out by the creeping pressure of snow; (2) the landslides occurred : these two causes (1) and (2) in turn contributed to the instability of the snow cover on the steep slope. (3) furthermore the friction resistance of the ground surface against snow cover decreased due to the loss of resistance produced by the over lying profuse miscanthuse cover.
