Abstract
The concept of avalanche size was introduced to develop a scale of avalanches obtained during four winter seasons from December 2001 to May 2005 on the east side of Mt. Gongendake (1104m a.s.l.), located at the western Maseguchi District in Nou Town, Niigata Prefecture. The relationship between avalanche size and frequency was investigated using 431 avalanche video images of the most avalancheprone slope on the east side of Mt. Gongendake. Research using avalanche size data in the United States (US size scale) has shown that avalanche size (S) and frequency (n) are described by the relationship (Log n =−αS+β), excluding minimum-size avalanches, and that the coefficient α varies over time and space. This study obtained a similar relationship, excluding minimum-size avalanches, with α and β coefficients of 0.65 and 3.7, respectively. Additionally, the coefficient α differed from one winter season to another and had a relationship with snowfall thickness or maximum snow depth. Therefore, a certain relationship exists between avalanche magnitude and frequency, but the coefficient α may be different from the snow condition of each winter season in the case of a same slope.
