CHARACTERISTICS AND PREDICTION OF HIGH-FREQUENCY AVALANCHE RUNOUT

In this paper, we present field data and analysis relating avalanche t errain variables and avalanche runout for 46 high-frequency avalanche paths. Most previous studies of this nature have been concerned with t he location of extreme runout for return periods of order 100 yr. In o ur study, we focus on extreme runout avalanche paths where return peri ods are much less than 100 yr and we compare the results with previous data collections. Our analysis shows that high-frequency avalanche pa ths are, on average, steeper and shorter than their low frequency coun terparts. Our analysis also indicates that the dimensionless measure o f avalanche extreme runout, the runout ratio, approximates a Gumbel di stribution, consistent with previous results. The calculation of a non exceedance probability, using the Gumbel distribution, is recommended for the prediction of extreme runout in land-use planning exercises fo r zones effected by high frequency avalanches.