The distribution of avalanche runout varies in space and time for individua
l avalanche paths and from mountain range to mountain range. In this paper,
such variations are considered based on the assumption (supported by data
worldwide) that the spatial distribution of extreme avalanche runout follow
s a Gumbel distribution and that the arrival rate of avalanches can be mode
lled as a Poisson process. The input required is a set of extreme avalanche
runout distances for the mountain range and a knowledge of avalanche frequ
ency at the beginning of the runout zone for the path in question. Such inf
ormation allows theoretical estimation of the effective return period as a
function of position, which is very important in zoning applications. In ad
dition, general expressions are derived to relate Gumbel parameters for dif
ferent mountain ranges to a frequency index to explore general frequency im
plications from one mountain range to another. The estimated Gumbel paramet
ers imply consistent relationships for expected avalanche frequency and ter
rain from one mountain range to another.